Hennara/MedRAG_contents · Datasets at Hugging Face

uuid stringlengths 36 36	chunk_index int64 0 24	text stringlengths 1 1.82k ⌀
ff10a339-9996-49ce-9936-9323a6a9e27f	3	These results suggest that under these conditions the PD between CSF and blood may play no effective role in determining the distributions of these charged species by 6 h. These results are contrasted with recent findings which suggest that H+ and HCO3- are distributed according to passive forces between CSF and blood.
64e2016f-f114-4fc5-9ba9-8836ca2db2ee	0	Ontogeny of tracheal fluid, pulmonary surfactant, and plasma corticoids in the fetal lamb. We examined fetal plasma corticoids and flow rate, electrolyte composition, and surfactant content of tracheal fluid in chronic experiments with eight fetal lambs. From 120 to 148 days of gestation the rate of fluid production was 4.5
64e2016f-f114-4fc5-9ba9-8836ca2db2ee	1	ml/kg per h, and there was no change in mean fluid sodium (147.8 meq/1), chloride (153.1 meq/1), calcium (2.2 mg/100 ml), and pH (6.23). Tracheal fluid potassium increased from 4.3 meq/1 at 120-130 days to 8.9 meq/1 at term, while plasma sodium, chloride, calcium, pH, and potassium were constant at 146.1
64e2016f-f114-4fc5-9ba9-8836ca2db2ee	2	meq/1, 110.0 meq/1, 12.1 mg/100 ml, 7.39, and 4.0 meq/1, respectively. Plasma corticoids were less than 1.5 mug/100 ml total (0.3 mug/100 ml free) until 130 days, when they increased rapidly to 10.5 total (3.2 free) at 148 days.
64e2016f-f114-4fc5-9ba9-8836ca2db2ee	3	Surfactant was first detected in tracheal fluid between 124 and 133 days and its secretion increased rapidly after 135 days to a value of 125 mug/kg per h at 148 days. A sudden increase in fetal plasma corticoids does not seem to be the stimulus for appearance of surfactant in the lamb, although these hormones may induce the rapid accumulation of surfactant prior to delivery.
faa48af4-4d72-4776-81fb-0c14ff7651f4	0	Hydrogen ion concentration and oxygen uptake in an isolated canine hindlimb. Oxygen utilization (VO2) and lactate production by an isolated perfused canine hindlimb was evaluated at various hydrogen ion concentrations. A membrane lung perfusion system was established such that blood flow and temperature could be fixed at normal levels.
faa48af4-4d72-4776-81fb-0c14ff7651f4	1	Oxygen, nitrogen, and carbon dioxide (CO2) gas flows to the membrane lung were independently regulated to provide a fixed arterial oxygen content (CaO2). By changing CO2 flow, the pH of the arterial blood was varied between 6.9 and 7.6 at 10-min intervals. The mean O2 delivery (CaO2 X blood flow) was between 16.3
faa48af4-4d72-4776-81fb-0c14ff7651f4	2	ML O2/min and 20.5 ml O2/min. Standard error of the mean in each dog, however, was less than 0.4 ml O2/min. VO2 was linearly related to the pH of the perfusing blood: VO2% = 100.1 pH - 643 (r = 0.866). Oxygen consumption was inversely related to PCO2:
faa48af4-4d72-4776-81fb-0c14ff7651f4	3	VO2% = -0.62 PCO2 + 124, but the correlation was less good (r = 0.729). Lactate production was linearly related to the pH of the perfusing blood (above a pH of 7.4): lactate produced = 22.5 pH - 162.5 (r = 0.75). At a pH below 7.4
faa48af4-4d72-4776-81fb-0c14ff7651f4	4	, lactate was not produced. Oxygen consumption of skeletal muscle appears critically dependent on extracellular fluid pH. A change in pH of 0.1 alters VO2 almost exactly 10%. Alkalosis is a potent stimulus to lactic acid production by skeletal muscle.
35f71cc7-1535-4eab-8c7d-ff088d3fcd2a	0	Cerebrospinal fluid sampling technique and Astrup pH and PCO2 values. The pH and PCO2 values measured by the Astrup technique were compared in cerebrospinal fluid (CSF) obtained using two different sampling techniques: 1) a direct or in vivo technique and 2) the widely accepted syringe sampling technique. In 65 pairs of measurements in 9 dogs it was found that the pH was always overestimated and the PCO2 always underestimated in the syringe sample when compared to the in vivo sample.
35f71cc7-1535-4eab-8c7d-ff088d3fcd2a	1	The equations describing the relationships are as follows: 1) pH (syringe = 0.995 pH (in vivo) + 0.084 and 2) PCO2 (syringe) = 0.873 PCO2 (in vivo) + 0.2. The amount by which the syringe sample underestimated the true PCO2 value increased with the absolute PCO2 value, consistent with the possibility of there being a diffusional loss of CO2 during the transfer of CSF from the syringe to the pH electrode (PCO2 (in vivo)- PCO2 (syringe) = 2.4
35f71cc7-1535-4eab-8c7d-ff088d3fcd2a	2	, 4.9, 7.5, and 10.0 mmHg at in vivo PCO2's of 20, 40, 60, and 80 mmHg). This study indicates that the technique used for sampling CSF is crucial to the expected accuracy of the results and that the number of transfers of CSF during the sampling and measurement procedures should be minimized in order to obtain reliable results.
d232ae55-a266-4501-ac11-feac76f01ac5	0	Hypoventilation in ponies after carotid body denervation. Seven ponies were subjected to carotid body denervation (CD) and two ponies were sham operated (S). Measurement of arterial blood gases and arterial blood and cerebrospinal fluid (CSF) acid-base balance were made prior to and 1,2,4,9, and 17 wks after surgery in unanesthetized animals.
d232ae55-a266-4501-ac11-feac76f01ac5	1	Resting ventilation and ventilatory responsiveness to hypoxia and NaCN infusion were assessed prior to and 2,9, and 17 wks after surgery. Alveolar hypoventilation in the CD ponies was marked 1-2 wk after surgery when VE and VA were reduced 40% and 10%, respectively, from control and PaCO2 was 12-15 mmHg above control.
d232ae55-a266-4501-ac11-feac76f01ac5	2	However, the effect was not nearly as great 4, 9, and 17 wk after surgery when the PaCO2 stabilized at approximately 6 mmHg above control PaCO2. Arterial blood pH was normal in the hypercapnic CD ponies, but CSF pH remained acid relative to normal throughout the 17-wk period.
d232ae55-a266-4501-ac11-feac76f01ac5	3	Changes in ventilatory responsiveness to hypoxia and NaCN tended to parallel changes in resting ventilation. These findings suggest: 1) the carotid bodies are essential in ponies to maintain normal ventilation: 2) in CD ponies peripheral chemosensitivity is partially regained at some unestablished locus; and 3) pH compensating mechanisms in chronically hypercapnic ponies function relatively better in blood than in CSF.
8ae2a65e-7fc3-4565-bf09-9db08d65319c	0	Total and regional cerebral blood flow during moderate and severe exercise in miniature swine. To determine the influence of exercise on cerebral blood flow, we ran 14 swine at 3-6 mph and at 0-10% grades on a treadmill for 30 min at moderate and severe levels of exercise.
8ae2a65e-7fc3-4565-bf09-9db08d65319c	1	Measuring heart rate, cardiac output, and aortic pressure via implanted probes, we injected 15-mum radiolabeled microspheres via the left atrium before and during exercise. We measured their distribution by gamma spectrometry, determining total cerebral blood flow, regional blood flow, and ratio of flow to gray and white matter.
8ae2a65e-7fc3-4565-bf09-9db08d65319c	2	Heart rate, cardiac output, and aortic pressure rose progressively with increasing exercise. Total cerebral flow resembled that reported in humans, i.e., it did not change significantly with exercise. Regional flow distribution also failed to change significantly with exercise. The ratio of gray to white matter flow did not change except to the cerebellum where it rose significantly from resting values at both moderate and severe exercise.
8ae2a65e-7fc3-4565-bf09-9db08d65319c	3	Gray matter received more flow than white matter during all three conditions of observation. Cerebral blood flow was remarkably constant during even severe exercise.
45f0443a-66a2-4b6a-ad9f-45409137aab1	0	Method for measuring hepatic uptake of oxygen or other blood-borne substances in situ. A preparation is described by which hepatic arterial blood flow and portal venous blood flow can be accurately and continuously measured while simultaneously providing a method by which multiple blood samples can be taken from the hepatic artery, portal vein, and hepatic vein without disrupting hepatic hemodynamics or causing hemodilution.
45f0443a-66a2-4b6a-ad9f-45409137aab1	1	By this means hepatic uptake or release of blood-borne substances can be measured in situ and correlated with hemodynamic parameters. In 13 splenectomized cats, oxygen uptake by the denervated liver was 4.5 +/- 0.3 ml . min-1. 100 g-1 of tissue, representing 54% of total oxygen removed by the splanchnic bed.
45f0443a-66a2-4b6a-ad9f-45409137aab1	2	The hepatic hemodynamics determined by this method are similar to those reported by others in vivo and the metabolic state of the liver remained stable for at least 2 h during which an average of 29 blood samples were taken. Advantages of this preparation over other methods of obtaining similar data are discussed.
2ce18811-718a-4922-9d72-951c6dfaa98a	0	Analysis of pesticide residues by chemical derivatization. II. N-methylcarbamates in natural water and soils. A method for the quantitative determination of several N-methylcarbamates in natural waters and the applicability of the derivative to soil samples using a previously published extraction procedure are described. After extraction of the carbamates from the substrate, the carbamates are hydrolyzed in a 10% methanol-potassium hydroxide solution to form the phenolic hydrolysis products, which are isolated and derivatized with pentafluorobenzyl (PFB) bromide to produce the PFB ether derivatives.
2ce18811-718a-4922-9d72-951c6dfaa98a	1	The PFB derivatives are cleaned up and fractionated on a silica gel microcolumn and determined by electron capture gas-liquid chromatography (GLC). Eight organophosphate pesticides and 2 phthalate acid esters that hydrolyze to phenols or phthalic acid were evaluated as potential interferences and were found not to interfere with any of the carbamates tested.
2ce18811-718a-4922-9d72-951c6dfaa98a	2	Quantitative determinations of 0.1 mug carbofuran and 3-ketocarbofuran and 0.5 mug carbaryl, metmercapturon, and Mobam in a 1 L water sample are possible. Propoxur was not determined at levels less than 1 mug/L due to the short GLC retention time of the derivative and interferences from the reagents at the lower levels.
de0c9c2d-92e6-42e9-96c6-3a34207e5685	0	Separation of pesticide residues from lipids prior to gas-liquid chromatographic analysis. Lipids are separated from dieldrin, endrin, and p,p'-DDE residues by saponification in ethanolic sodium hydroxide, acidification with dilute sulfuric acid, and adsorption chromatography on deactivated alumina, using petroleum ether as the eluant. Dieldrin, endrin, and p,p'-DDE are efficiently recovered (95-102%), and p,p'-DDT is converted to p,p'-DDE, which is then recovered with high yield (90-96%).
de0c9c2d-92e6-42e9-96c6-3a34207e5685	1	Extremely low lipid carryover (less than 0.3-0.5%) is observed for 0.5-1.0 g samples of chicken fat.
ea326513-4f0d-4b06-9157-17a97ae76b78	0	Collaborative study of the Food Chemicals Codex method for the determination of the neutralizing value of sodium aluminum phosphate. Fifteen laboratories participated in a collaborative study to evaluate the Food Chemicals Codex method for the determination of the neutralizing value of sodium aluminum phosphate. The AOAC method for determining the neutralizing value of sodium acid pyrophosphate, sec.
ea326513-4f0d-4b06-9157-17a97ae76b78	1	8.010, was also included in the study. The precisions of the Food chemicals Codex method, based on the between-replicate standard deviation and on one collaborator making one determination, are 1.16 and 3.66, respectively. The Food Chemicals Codex method for the determination of the neutralizing value of sodium aluminum phosphate has been adopted as official first action.
759e12be-6885-4d12-a03a-76f6096ae06f	0	Affinity chromatography of trypsin and related enzymes. I. Preparation and characteristics of an affinity adsorbent containing tryptic peptides from protamine as ligands. An absorbent for the affinity chromatography of trypsin [EC 3.4.21.4] (AP Sepharose) was prepared. The ligand was a mixture of oligopeptides (mainly di- and tripeptides) containing L-arginine as carboxyl termini, and was obtained from a tryptic digest of protamine.
759e12be-6885-4d12-a03a-76f6096ae06f	1	Trypsin was absorbed at relatively low pH (7-4), but was not absorbed at the optimum pH of catalysis (8.2). This was clearly explained on the basis of the pH dependence of the interaction of trypsin with its products. Inactivated trypsin, trypsinogen, and chymotrypsin were not absorbed.
759e12be-6885-4d12-a03a-76f6096ae06f	2	The absorption of active trypsin was interferred with by either benzamidine or urea. From these observations, it is evident that AP Sepharose is an affinity adsorbent. AP Sepharose was useful for purification of commercial bovine trypsin. A preliminary application for the purification of Streptomyces griseus trypsin was also successful.
de613544-3f3b-4d9a-932e-c4f097fc180c	0	Effects on tryptophyl absorption of the ionization of the catalytic carboxyls in hen and turkey lysozymes. The difference spectra of hen and turkey egg-white lysozymes [EC 3.2.1.17] produced by acidification were measured. The difference spectra of both lysozymes had peaks at 295 and 301 nm which are characteristic of tryptophyl residues.
de613544-3f3b-4d9a-932e-c4f097fc180c	1	The pH dependence curves of the extinction differences (delta eplision) at 301 nm and 295 nm for hen lysozyme were identical with the corresponding curves for turkey lysozyme. The pH dependence of delta eplision at 301 nm was analyzed assuming that the extinction at 301 nm is due to Trp 108 only, which interacts with the catalytic carboxyls, Glu 35 and Asp 52.
de613544-3f3b-4d9a-932e-c4f097fc180c	2	The macroscopic pK values of Glu 35 and Asp 52 in both lysozymes thus determined were 6.0 and 3.3, respectively. These values were in excellent agreement with those determined by measuring the pH dependence of the circular dichroic band at 305 nm (Kuramitsu et al. (1974) J. Biochem, 76, 671-683;
de613544-3f3b-4d9a-932e-c4f097fc180c	3	(1975) ibid. 77, 291-301). The pH dependence of delta eplision at 295 nm could not be completely explained in terms of the electrostatic effects of the catalytic groups on Trp 108.
085d2bfc-d5e0-4808-b990-882c563a39f9	0	Resonance Raman scattering from hemoproteins. Effects of ligands upon the Raman spectra of various C-type cytochromes. Resonance Raman spectra were measured for various C-type cytochromes (mammalian cytochrome c, bacterial cytochrome c3, algal photosynthetic cytochrome f, and alkylated cytochrome c) and a B-type cytochrome (cytochrome b5) in their reduced and oxidized states.
085d2bfc-d5e0-4808-b990-882c563a39f9	1	(1) For ferrous alkylated cytochrome c, a Raman line sensitive to the replacement of an axial ligand of the heme iron uas found around 1540 cm=1. This ligand-sensitive Raman line indicated the transition from acidic (1545 cm-1) to alkaline (1533 cm-1) forms with pK 7.9. The pH dependence of the Raman spectrum corresponded well to that of the optical absorption spectra.
085d2bfc-d5e0-4808-b990-882c563a39f9	2	(2) For ferrous cytochrome f, the ligand-sensitive Raman line was found at the same frequency as cytochrome c (1545 cm-1). Accordingly two axial ligands are likely to be histidine and methionine as in cytochrome c. (3) For ferrous cytochrome c3, the frequency of the ligand-sensitive Raman line was between those of cytochrome c and cytochrome b5.
085d2bfc-d5e0-4808-b990-882c563a39f9	3	Since two axial ligands of the heme iron in cytochrome c3 might be histidines. However, a combination of histidine and methionine as a possible set of two axial ligands was not completely excluded for one or two of the four hemes. (4) In ferrous cytochrome b5, two weak Raman lines appeared at 1302 and 1338 cm-1 instead of the strongest band at 1313 cm-1 of C-type ferrous cytochromes.
085d2bfc-d5e0-4808-b990-882c563a39f9	4	This suggests the practical use of these bands for the identification of types of cytochromes. The difference in frequency and intensity between B- and C-types of hemes implies that the low effective symmetry of the heme in ferrous cytochrome c is due to vibrational coupling of ring modes with peripheral substituents rather than geometrical disortion of heme.
9c45e182-e356-4cf1-9b5e-396171f00d61	0	Studies on the microsomal electron-transport system of anaerobically grown yeast. III. Spectral characterization of cytochrome P-450. A carbon monoxide-binding pigment which shows an absorption peak at about 450 nm in the reduced carbon monoxide difference spectrum was purified from the microsomal fraction of yeast grown anaerobically.
9c45e182-e356-4cf1-9b5e-396171f00d61	1	The spectral characteristics of the pigment were practically identical with those of cytochrome P-450 of hepatic microsomes, especially from polycyclic hydrocarbon-induced animals. The pigment was denatured to P-420, and bound with ethyl isocyanide in the reduced state. Although Type I spectral change was not evident, the pigment showed Type II and modified Type II spectral changes upon binding with some organic compounds, as in the case of hepatic cytochrome P-450.
9c45e182-e356-4cf1-9b5e-396171f00d61	2	These observations clearly indicate that the carbon monoxide-binding pigment of yeast microsomes may be designated as cytochrome P-450 of yeast.
42e529a1-3f3f-4926-bc65-3ed89a74296d	0	Polarographic studies on ubiquinone-10 and rhodoquinone bound with chromatophores from Rhodospirillum rubrum. Redox components bound with chromatophores of Rhodospirillum rubrum, and pure samples of ubiquinone-10 and rhodoquinone were studied polarographically at 24 degrees. In a mixture of ethanol and water (4 : 1, v/v) at pH 7, ubiquinone-10 and rhodoquinone had half-wave potentials (E1/2) OF +43 MV and -63 mV, respectively.
42e529a1-3f3f-4926-bc65-3ed89a74296d	1	For both quinones, values of the electron transfer number (n) were 2 , and plots of E1/2 versus pH formed straight lines with slopes of -30 mV/pH in the neutral pH range; thus, values of the proton transfer number (n-a) were estimated to be 1 for both quinones.
42e529a1-3f3f-4926-bc65-3ed89a74296d	2	When bound with chromatophores, ubiquinone-10 and rhodoquinone had E1/2 values of +50 mV (n=2) and -30 mV (n=2), respectively, at pH 7. Values of (n-a) were estimated to be 1 for ubiquinone-10 and 2 for rhodoquinone. A component (POC-170) thought to be one of the active center bacteriochlorophylls (Liac-890) was characterized;
42e529a1-3f3f-4926-bc65-3ed89a74296d	3	it has E1/2 value of -170 mV at pH 7 and its oxidation-reduction is possibly brought about by dehydrogenation-hydrogenation. Conceivably, the oxidation-reduction sites of ubiquinone-10, rhodoquinone and POC-170 partly, if not all, exist on the surface of chromatophore membrane or project outside the membrane, because of their accessibility to the polarographic electrode.
1bc49384-74b6-40f2-830f-23afe9147eff	0	Effect of metal ions in the culture medium on the stearoyl-coenzyme A desaturase activity of Mycobacterium phlei. A particulate fraction prepared from Mycobacterium phlei grown in a metal-deficient medium exhibited a greatly reduced activity of stearoyl-CoA desaturase compared to that from normally grown cells. Metal deficiency, however, had no effect on the FAD-dependent NADPH-cytochrome C reductase activity, which has been suggested to participate in the desaturation process.
1bc49384-74b6-40f2-830f-23afe9147eff	1	When the cells were grown in the deficient medium supplemented with both Fe2+ and Mg2+, the desaturase activity was restored to the normal level. Supplementation with Mg2+ alone promoted growth but did not restore the desaturase activity, whereas Fe2+ alone did cause a significant restoration. Among the various metal ions tested, only Fe2+ and Fe3+ enhanced the formation of desaturase activity in the deficient medium.
1bc49384-74b6-40f2-830f-23afe9147eff	2	When added to the assay medium in vitro, Fe2+ and Fe3+ did not stimulate the desaturase activity of the particulate fraction from the deficient cells. Cultivation in the metal-deficient medium had essentially no effect on the levels of cytochromes in the particulate fraction, but dramatically decreased the non-heme iron content and the amount of a high-spin ferric species exhibiting an ESR signal at g=4.3
1bc49384-74b6-40f2-830f-23afe9147eff	3	. No labile sulfur could be detected in the normal or metal-deficient particulate fractions. It is concluded that the presence of iron ions in the culture medium is necessary for the synthesis and/or assembly of the terminal portion of the desaturase system.
43b477a7-c18e-4d9e-8b8b-b7c8fea1a257	0	Photoaffinity labeling of concanavalin A. Preparation of a concanavalin A derivative with reduced valence. Concanavalin A (Con A) was labeled with p-azidophenyl alpha-D-mannopyranoside under ultraviolet irradiation and the reaction products were separated by affinity chromatography on Sephadex G-100 at pH 5. One of the Con A derivatives thus obtained was characterized as a monovalent dimer at pH 5 and a divalent tetramer at pH 7 by sedimentation equilibrium and equilibrium dialysis, indicating that this photoaffinity labeling did not alter the quaternary structure of Con A.
43b477a7-c18e-4d9e-8b8b-b7c8fea1a257	1	In agreement with these results, the labeled Con A did not show the capacity to precipitate glycogen at pH 5, but it formed precipitates with glycogen at pH 7. Although its hemagglutinating activity was found to be weaker than that of the native Con A, the dose-response cure of the labeled Con A in the mitogenic stimulation of human peripheral lymphocytes was almost identical to that of the native con A.
90151b47-151c-4ef1-b926-af0636decb20	0	Chemical modification of carboxyl groups of fibrinogen and its effect on the binding of cationic detergent. Carboxyl groups of native human fibrinogen were modified with glycine methyl ester and 1-ethyl-3(3-dimethylaminopropyl)carbodiimide. It seemed likely that the modification occurred stepwise. Approximately 26% of the carboxyl groups of fibrinogen was modified finally.
90151b47-151c-4ef1-b926-af0636decb20	1	The modified fibrinogen had no interaction with cationic detergent, and did not form any complex with the detergent. In dilute acid, fibrinogen was observed to show only a slight interaction with cationic detergent. It is probable that the exposed and ionized carboxyl groups are essential for the formation of a complex between fibrinogen and cationic detergent.
c770dcb3-8498-4c4a-a847-47658bedba34	0	Purification and characterization of proteinase inhibitors from adzuki beans (Phaseolus angularis). Two proteinase inhibitors, designated as inhibitors I and II, were purified from adzuki beans (Phaseolus angularis) by chromatographies on DEAE- and CM-cellulose, and gel filtration on a Sephadex G-100 column. Each inhibitor shows unique inhibitory activities.
c770dcb3-8498-4c4a-a847-47658bedba34	1	Inhibitor I was a powerful inhibitor of trypsin [EC 3.4.21.4], but essentially not of chymotrypsin ]EC 3.4.21.1]. On the other hand, inhibitor II inhibited chymotrypsin more strongly than trypsin. The molecular weights estimated from the enzyme inhibition were 3,750 and 9,700 for inhibitors I and II, respectively, assuming that the inhibitions were stoichiometric and in 1 :
c770dcb3-8498-4c4a-a847-47658bedba34	2	1 molar ratio. The amino acid compositions of both inhibitors closely resemble those of low molecular weight inhibitors of other leguminous seeds: they contain large amounts of half-cystine, aspartic acid and serine, and little or no hydrophobic and aromatic amino acids. Inhibitor I lacks both tyrosine and tryptophan residues.
c770dcb3-8498-4c4a-a847-47658bedba34	3	The molecular weights were calculated to be 7,894 and 8,620 for inhibitors I and II, respectively. The reliability of these molecular weights was confirmed by the sedimentation equilibrium and 6 M guanidine gel filtration methods. On comparison with the values obtained from enzyme inhibition, it was concluded that inhibitor I and two trypsin inhibitory sites on the molecule, whereas inhibitor II had one chymotrypsin and one trypsin inhibitory sites on the molecule.
06746f2d-c714-4658-9ed3-cb6452f41adb	0	Mitochondrial malate dehydrogenase of bovine cerebrum. Characterization and mechanisms of inhibition by silver ions. Attempts were made to characterize mitochondrial malate dehydrogenase [L-malate: NAD+ oxidoreductase, EC 1.1.1.37] (M-MDH) purified from bovine cerebrum and to elucidate the mechanisms responsible for inhibition of the enzymic activity by Ag+.
06746f2d-c714-4658-9ed3-cb6452f41adb	1	The molecular weights of the native enzyme and its subunits were 54,000-55,000 and 30,000-32,000, respectively. In general, the physiochemical and catalytic properties of bovine cerebral M-MDH was not very different from those of other corresponding mammalian enzymes. Incubation of the enzyme with Ag+ caused the loss of equivalent amounts of sulfhydryls with a parallel decrease of the enzymic activity.
06746f2d-c714-4658-9ed3-cb6452f41adb	2	When the enzyme was exposed to 2-, 3.5-, and 5-fold molar excesses of Ag+, the enzymic activity showed an initial rapid fall and a subsequent slow restoration to a partially inactivated level (60-70, 45-50, and 15-20% of an untreated control, respectively), while the alpha-helical content of the enzyme fell exponentially with time.
06746f2d-c714-4658-9ed3-cb6452f41adb	3	A 7-fold molar excess of Ag+ reduced both the enzymic activity and the alpha-helical content to a much greater degree and no restoration of the enzymic activity was observed. The Km values of Ag+-inactivated enzyme for NADH and oxaloacetate were the same as those of the native enzyme.
06746f2d-c714-4658-9ed3-cb6452f41adb	4	The data suggest that Ag+ could inhibit enzymic activity both by reducing the structural regularity of the enzyme molecule and by attacking sulfhydryl groups necessary for the catalytic activity of bovine cerebral M-MDH.
33fcd951-f1c0-4b0b-8260-93bc1f9549cc	0	Double-headed protease inhibitors from black-eyed peas. II. Structural studies by optical absorption and circular dichroism. Two new double-headed protease inhibitors from black-eyed peas have amino acid compositions typical of the low molecular weight protease inhibitors from legume seeds. Black-eyed pea chymotrypsin and trypsin inhibitor (BEPCI) contains no tryptophan, 1 tyrosine, and 14 half-cystines out of 83 amino acid residues per monomer.
33fcd951-f1c0-4b0b-8260-93bc1f9549cc	1	Black-eyed pea trypsin inhibitor (BEPTI) contains no tryptophan, 1 tyrosine, and 14 half-cystines out of 75 residues per monomer. The molar extinctions at 280 nm are 2770 for BEPCI and 3440 for BEPTI. The single tyrosyl residue is very inaccessible to solvent in native BEPCI and BEPTI at neutral pH and titrates anomalously with an apparent pK = 12.
33fcd951-f1c0-4b0b-8260-93bc1f9549cc	2	Ionization of tyrosine is complete in 13 hours above pH 12. No heterogeneity of the local environment of the tyrosyl residues in different subunits can be detected spectrophotometrically. The large number of cystine residues leads to an intense and complex near-ultraviolet CD spectrum with cystine contributions in the regions of 248 and 280 nm and tyrosine contributions at 233 and 280 nm.
33fcd951-f1c0-4b0b-8260-93bc1f9549cc	3	An intact disulfide structure is required for appearance of the tyrosyl CD bands. The inhibitors are unusually resistant to denaturation when compared with similar low molecular weight proteins of high disulfide content. All observations are consistent with a far more rigid structure for BEPCI and BEPTI than for a typical protein.
ee1c0293-ddaa-4a24-a7c9-27890b4cd98a	0	Double-headed protease inhibitors from black-eyed peas. III. Subunit interactions of the native and half-site chemically modified proteins. The chemical modification of two new double-headed-protease inhibitors from black-eyed peas, a trypsin-chymotrypsin inhibitor (BEPCI) and a trypsin inhibitor (BEPTI) with dansyl chloride was investigated under various conditions.
ee1c0293-ddaa-4a24-a7c9-27890b4cd98a	1	The NH2-terminal serine of both BEPCI and BEPTI, the 4 lysyl residues of BEPCI, and 4 of the 5 lysyl residues of BEPTI, could not be dansylated in the absence of urea. The single tyrosine per subunit of BEPCI and BEPTI was unreactive even in the presence of urea but could be labeled with half-site reactivity by the Celite method.
ee1c0293-ddaa-4a24-a7c9-27890b4cd98a	2	Lysine, NH2-terminal serine, and tyrosine were reactive in fully reduced, carbamidomethylated BEPCI and BEPTI. Gel filtration was used to study the subunit interactions of BEPCI and BEPTI. At pH 8 or pH 3.0 there is a complex set of multiple equilibria with widely differing rates of attainment.
ee1c0293-ddaa-4a24-a7c9-27890b4cd98a	3	We have found evidence for a rapid dimer-tetramer equilibrium, a distinct moderate rate dimer-tetramer equilibrium, a very slow monomer-dimer equilibrium, and postulate slow isomerization of the two forms of dimer and the two forms of tetramer. The monomer-dimer equilibrium is quite unusual in that the dimer is stabilized by chaotropic ions and even slightly by guanidine HC1.
ee1c0293-ddaa-4a24-a7c9-27890b4cd98a	4	In contrast to the complex pattern seen in native BEPCI, the half-site, dansylated BEPCI exists at similar concentration exclusively as a tetramer at neutral pH.
a8d127d5-8f38-48d0-8519-df61c5bed680	0	Affinity labeling of the primary bilirubin binding site of human serum albumin. A label for the bilirubin binding sites of human serum albumin was synthesized by reacting 2 mol of Woodward's reagent K (N-ethyl-5-phenylisoxazolium-3'-sulfonate) with 1 mol of bilirubin. This yielded a water-soluble derivative in which both carboxyl groups of bilirubin were converted to reactive enol esters.
a8d127d5-8f38-48d0-8519-df61c5bed680	1	Covalent labeling was achieved by reacting the label with human serum albumin under nitrogen at pH 9.4 and 20 degrees. Under the same conditions, no covalent binding to the monomers of several proteins could be demonstrated. The number of binding sites for bilirubin and the label were found to be the same, and competition experiments with bilirubin showed inhibition of covalent labeling.
a8d127d5-8f38-48d0-8519-df61c5bed680	2	The absorption, fluorescence and CD spectra of the label in a complex with human serum albumin were similar to those of the bilirubin human serum albumin complex. However, following covalent attachment to the spectral properties were changed, indicating loss of conformational freedom of the chromophore. Labeling ratios were selected to result in the incorporation of less than 1 mol of label/mol of human serum albumin.
a8d127d5-8f38-48d0-8519-df61c5bed680	3	Under these conditions, labeling is thought to occur primarily at the high affinity binding site.
480a267c-af8e-4d0a-a7aa-662acea66e5f	0	Acylation of subtilisin Carlsberg by phenyl esters. Approximate Hammett reaction constants rho calculated from k2/K8 values of several phenyl esters of N-acetyl-L-phenylalanine, hippuric acid, and beta-phenylpropionic acid are 0.0, 0.4, and 1.0 respectively.
480a267c-af8e-4d0a-a7aa-662acea66e5f	1	To determine whether the lack of substituent effect of k2/K8 with the N-acetyl-L-phenylalanine esters is a result of substituent-insensitive k2 or rate-limiting association of enzyme and substrate, pH-k2/K8 deependences and solvent deuterium isotope effects were determined for certain of the substrates and compared with those found with the corresponding hippurates and beta-phenylpropionates. In the pH range 5 to 8, k2/K8 of the phenyl and 4-nitrophenyl esters of each series is dependent upon the unprotonated form of an enzymatic base of apparent pKa approximately 7.4
480a267c-af8e-4d0a-a7aa-662acea66e5f	2	, identical with the pKa found for the free enzyme. With the phenyl esters of each substrate class, k2/K8 decreased by 2 to 3 times in deuterium oxide compared with water. The results suggest that a step involving a general base-catalyzed proton transfer, almost certainly k2, is rate-limiting with the N-acetyl-L-phenylalaninates, as well as the hippurates and beta-phenylpropionates.
480a267c-af8e-4d0a-a7aa-662acea66e5f	3	Attack by the protein on the latter substrates is prediminantly nucleophilic, judged by the similarity of rho in the enzymatic and reference hydroxide ion-catalyzed hydrolyses. The power rho values for the N-acetyl-L-phenylalaninates and hippurates could result from an electrophilic component in their hydrolytic mechanisms.
f3ce5be7-24a8-4f98-bd39-afab6933adb4	0	Inhibition by superoxide dismutase of methemoglobin formation from oxyhemoglobin. The formation of methemoglobin from oxyhemoglobin in a solution containing photoreduced riboflavin and oxygen was inhibited by superoxide dismutase. The rate of the reaction was pH-dependent in the range of 6.8 to 7.8, increasing as the pH was reduced.
f3ce5be7-24a8-4f98-bd39-afab6933adb4	1	Inhibition by superoxide dismutase was enhanced as the EDTA concentration increased and was dependent on enzymatic activity. Under conditions in which superoxide dismutase inhibition was incomplete, catalase inhibited the reaction but mannitol had no effect. The data support the mediation of methemoglobin formation by superoxide. The hypothesis is offered that superoxide anion reduced the heme-bound oxygen in oxygemoglobin by one electron, permitting the subsequent dissociation of ferrihemoglobin and peroxide.
f3ce5be7-24a8-4f98-bd39-afab6933adb4	2	The ability of superoxide dismutase to inhibit the formation of methemoglobin may represent one of its functions in the mature erythrocyte.
c7085119-ddca-4eed-9133-41bd8dceb9b6	0	Transport and metabolism of vitamin B6 in the yeast Saccharomyces carlsbergensis 4228. Active transport of pyridoxine, pyridoxal, and pyridoxamine occurs in resting cells of Saccharomyces carlsbergensis 4228 and can lead to intracellular concentrations of free vitamin much higher than those supplied externally. The initial Km for pyridoxine uptake is 3.6
c7085119-ddca-4eed-9133-41bd8dceb9b6	1	x 10(-7) M at 30 degrees and pH 4.5, which are optimum for growth. Transport is inhibited by many unphosphorylated vitamin analogs, the most effective being 5'-deoxypyridoxine, 5'-deoxypridoxal, toxopyrimidine, 4'-deoxypyridoxine, and 3-amino-3-deoxypyridoxine. Two distinct uptake systems that differ in structural specificity and ionic requirements are present.
c7085119-ddca-4eed-9133-41bd8dceb9b6	2	One, with optimum pH of 3.5, transports pyridoxal effectively, but not pyridoxamine; the other (optimum pH 6.0) transports pyridoxamine effectively, but not pyridoxal. Both systems transport pyridoxine, while neither transports pyridoxal 5'-phosphate. Other properties of these systems are similar, indicating that they share certain elements in common.
c7085119-ddca-4eed-9133-41bd8dceb9b6	3	An initial temperature optimum of 30 degrees is observed for pyrodoxine transport and, at this temperature, an "overshoot" in intracellular vitamin levels, with subsequent decrease to a constant level, occurs with time. It appears that intracellular vitamin, or a derivative, activates the exit mechanism for the vitamin.
c7085119-ddca-4eed-9133-41bd8dceb9b6	4	Exit rates also depend on the resuspension buffer and are increased in the presence of glucose and decreased by azide. Above 30 degrees net uptake of pyridoxine drops initially, then rapidly increases to a second optimum at 50 degrees; the uptake system is inactivated at about 55 degrees.
c7085119-ddca-4eed-9133-41bd8dceb9b6	5	The optimum at 50 degrees apparently results from activation of inflow as exit is rapid and is accelerated by azide. No overshoot was detected at 50 degrees, so it appears that the exit system is not regulated by intracellular vitamin at this temperature. A phase transition in membrane lipids occurs at 30 degrees and may be responsible for the change in properties of the inflow and exit mechanisms above this temperature.
8c8269b5-042a-4089-b589-d900ef9c4440	0	Transport and metabolism of vitamin B6 in Salmonella typhimurium LT2. Salmonella typhimurium LT2 concentrates radioactivity intracellularly from [3H]pyridoxal or [3H]pyridoxine up to 25 times the external concentration. After 1 min of uptake intracellular radioactivity is found as phosphorylated vitamin B6. The process is sensitive to temperature and is maximally active at pH 8.1
8c8269b5-042a-4089-b589-d900ef9c4440	1	, but under the conditions tested it is insensitive to monovalent cations or metabolic inhibitors, and does not require an exogenous energy source. The Km values for uptake of pyridoxine and pyridoxal are 2.0 x 10(-7) M and 1.2 x 10(-7) M, respectively; [3H]pyridoxamine is not transported.
8c8269b5-042a-4089-b589-d900ef9c4440	2	Evidence is presented for an uptake mechanism involving facilitated diffusion followed by trapping by pyridoxal kinase. S. typhimurium also appears to lack a periplasmic binding protein for vitamin B6.
5a02ebe3-a03e-4740-a367-a20a029c6fa7	0	Correlation of the kinetics of electron transfer activity of various eukaryotic cytochromes c with binding to mitochondrial cytochrome c oxidase. 1. A detailed study of cytochrome c oxidase activity with Keilin-Hartree particles and purified beef heart enzyme, at low ionic strength and low cytochrome c concentrations, showed biphasic kinetics with apparent Km1 = 5 x 10(-8) M, and apparent Km2 = 0.35
5a02ebe3-a03e-4740-a367-a20a029c6fa7	1	to 1.0 x 10(-6) M. Direct binding studies with purified oxidase, phospholipid-containing as well as phospholiptaining aid-depleted, demonstrated two sites of interaction of cytochrome c with the enzyme, with KD1 less than or equal to 10(-7) M, and KD2 = 10(-6) M.
5a02ebe3-a03e-4740-a367-a20a029c6fa7	2	2. The maximal velocities as low ionic strength increased with pH and were highest above ph 7.5. 3. The presence and properties of the low apparent Km phase of the kinetics were strongly dependent on the nature and concentration of the anions in the medium. The multivalent anions, phosphate, ADP, and ATP, greatly decreased the proportion of this phase and similarly decreased the amount of high affinity cytochrome c-cytochrome oxidase complex formed.
5a02ebe3-a03e-4740-a367-a20a029c6fa7	3	The order of effectiveness was ATP greater than ADP greater than P1 and since phosphate binds to cytochrome c more strongly than the nucleotides, it is concluded that the inhibition resulted from anion interaction with the oxidase. 4mat low concentrations bakers' yeast iso-1, bakers' yeast iso-1, horse, and Euglena cytochromes c at high concentrations all attained the same maximal velocity.

ff10a339-9996-49ce-9936-9323a6a9e27f

3

These results suggest that under these conditions the PD between CSF and blood may play no effective role in determining the distributions of these charged species by 6 h. These results are contrasted with recent findings which suggest that H+ and HCO3- are distributed according to passive forces between CSF and blood.

64e2016f-f114-4fc5-9ba9-8836ca2db2ee

0

Ontogeny of tracheal fluid, pulmonary surfactant, and plasma corticoids in the fetal lamb. We examined fetal plasma corticoids and flow rate, electrolyte composition, and surfactant content of tracheal fluid in chronic experiments with eight fetal lambs. From 120 to 148 days of gestation the rate of fluid production was 4.5

64e2016f-f114-4fc5-9ba9-8836ca2db2ee

1

ml/kg per h, and there was no change in mean fluid sodium (147.8 meq/1), chloride (153.1 meq/1), calcium (2.2 mg/100 ml), and pH (6.23). Tracheal fluid potassium increased from 4.3 meq/1 at 120-130 days to 8.9 meq/1 at term, while plasma sodium, chloride, calcium, pH, and potassium were constant at 146.1

64e2016f-f114-4fc5-9ba9-8836ca2db2ee

2

meq/1, 110.0 meq/1, 12.1 mg/100 ml, 7.39, and 4.0 meq/1, respectively. Plasma corticoids were less than 1.5 mug/100 ml total (0.3 mug/100 ml free) until 130 days, when they increased rapidly to 10.5 total (3.2 free) at 148 days.

64e2016f-f114-4fc5-9ba9-8836ca2db2ee

3

Surfactant was first detected in tracheal fluid between 124 and 133 days and its secretion increased rapidly after 135 days to a value of 125 mug/kg per h at 148 days. A sudden increase in fetal plasma corticoids does not seem to be the stimulus for appearance of surfactant in the lamb, although these hormones may induce the rapid accumulation of surfactant prior to delivery.

faa48af4-4d72-4776-81fb-0c14ff7651f4

0

Hydrogen ion concentration and oxygen uptake in an isolated canine hindlimb. Oxygen utilization (VO2) and lactate production by an isolated perfused canine hindlimb was evaluated at various hydrogen ion concentrations. A membrane lung perfusion system was established such that blood flow and temperature could be fixed at normal levels.

faa48af4-4d72-4776-81fb-0c14ff7651f4

1

Oxygen, nitrogen, and carbon dioxide (CO2) gas flows to the membrane lung were independently regulated to provide a fixed arterial oxygen content (CaO2). By changing CO2 flow, the pH of the arterial blood was varied between 6.9 and 7.6 at 10-min intervals. The mean O2 delivery (CaO2 X blood flow) was between 16.3

faa48af4-4d72-4776-81fb-0c14ff7651f4

2

ML O2/min and 20.5 ml O2/min. Standard error of the mean in each dog, however, was less than 0.4 ml O2/min. VO2 was linearly related to the pH of the perfusing blood: VO2% = 100.1 pH - 643 (r = 0.866). Oxygen consumption was inversely related to PCO2:

faa48af4-4d72-4776-81fb-0c14ff7651f4

3

VO2% = -0.62 PCO2 + 124, but the correlation was less good (r = 0.729). Lactate production was linearly related to the pH of the perfusing blood (above a pH of 7.4): lactate produced = 22.5 pH - 162.5 (r = 0.75). At a pH below 7.4

faa48af4-4d72-4776-81fb-0c14ff7651f4

4

, lactate was not produced. Oxygen consumption of skeletal muscle appears critically dependent on extracellular fluid pH. A change in pH of 0.1 alters VO2 almost exactly 10%. Alkalosis is a potent stimulus to lactic acid production by skeletal muscle.

35f71cc7-1535-4eab-8c7d-ff088d3fcd2a

0

Cerebrospinal fluid sampling technique and Astrup pH and PCO2 values. The pH and PCO2 values measured by the Astrup technique were compared in cerebrospinal fluid (CSF) obtained using two different sampling techniques: 1) a direct or in vivo technique and 2) the widely accepted syringe sampling technique. In 65 pairs of measurements in 9 dogs it was found that the pH was always overestimated and the PCO2 always underestimated in the syringe sample when compared to the in vivo sample.

35f71cc7-1535-4eab-8c7d-ff088d3fcd2a

1

The equations describing the relationships are as follows: 1) pH (syringe = 0.995 pH (in vivo) + 0.084 and 2) PCO2 (syringe) = 0.873 PCO2 (in vivo) + 0.2. The amount by which the syringe sample underestimated the true PCO2 value increased with the absolute PCO2 value, consistent with the possibility of there being a diffusional loss of CO2 during the transfer of CSF from the syringe to the pH electrode (PCO2 (in vivo)- PCO2 (syringe) = 2.4

35f71cc7-1535-4eab-8c7d-ff088d3fcd2a

2

, 4.9, 7.5, and 10.0 mmHg at in vivo PCO2's of 20, 40, 60, and 80 mmHg). This study indicates that the technique used for sampling CSF is crucial to the expected accuracy of the results and that the number of transfers of CSF during the sampling and measurement procedures should be minimized in order to obtain reliable results.

d232ae55-a266-4501-ac11-feac76f01ac5

0

Hypoventilation in ponies after carotid body denervation. Seven ponies were subjected to carotid body denervation (CD) and two ponies were sham operated (S). Measurement of arterial blood gases and arterial blood and cerebrospinal fluid (CSF) acid-base balance were made prior to and 1,2,4,9, and 17 wks after surgery in unanesthetized animals.

d232ae55-a266-4501-ac11-feac76f01ac5

1

Resting ventilation and ventilatory responsiveness to hypoxia and NaCN infusion were assessed prior to and 2,9, and 17 wks after surgery. Alveolar hypoventilation in the CD ponies was marked 1-2 wk after surgery when VE and VA were reduced 40% and 10%, respectively, from control and PaCO2 was 12-15 mmHg above control.

d232ae55-a266-4501-ac11-feac76f01ac5

2

However, the effect was not nearly as great 4, 9, and 17 wk after surgery when the PaCO2 stabilized at approximately 6 mmHg above control PaCO2. Arterial blood pH was normal in the hypercapnic CD ponies, but CSF pH remained acid relative to normal throughout the 17-wk period.

d232ae55-a266-4501-ac11-feac76f01ac5

3

Changes in ventilatory responsiveness to hypoxia and NaCN tended to parallel changes in resting ventilation. These findings suggest: 1) the carotid bodies are essential in ponies to maintain normal ventilation: 2) in CD ponies peripheral chemosensitivity is partially regained at some unestablished locus; and 3) pH compensating mechanisms in chronically hypercapnic ponies function relatively better in blood than in CSF.

8ae2a65e-7fc3-4565-bf09-9db08d65319c

0

Total and regional cerebral blood flow during moderate and severe exercise in miniature swine. To determine the influence of exercise on cerebral blood flow, we ran 14 swine at 3-6 mph and at 0-10% grades on a treadmill for 30 min at moderate and severe levels of exercise.

8ae2a65e-7fc3-4565-bf09-9db08d65319c

1

Measuring heart rate, cardiac output, and aortic pressure via implanted probes, we injected 15-mum radiolabeled microspheres via the left atrium before and during exercise. We measured their distribution by gamma spectrometry, determining total cerebral blood flow, regional blood flow, and ratio of flow to gray and white matter.

8ae2a65e-7fc3-4565-bf09-9db08d65319c

2

Heart rate, cardiac output, and aortic pressure rose progressively with increasing exercise. Total cerebral flow resembled that reported in humans, i.e., it did not change significantly with exercise. Regional flow distribution also failed to change significantly with exercise. The ratio of gray to white matter flow did not change except to the cerebellum where it rose significantly from resting values at both moderate and severe exercise.

8ae2a65e-7fc3-4565-bf09-9db08d65319c

3

Gray matter received more flow than white matter during all three conditions of observation. Cerebral blood flow was remarkably constant during even severe exercise.

45f0443a-66a2-4b6a-ad9f-45409137aab1

0

Method for measuring hepatic uptake of oxygen or other blood-borne substances in situ. A preparation is described by which hepatic arterial blood flow and portal venous blood flow can be accurately and continuously measured while simultaneously providing a method by which multiple blood samples can be taken from the hepatic artery, portal vein, and hepatic vein without disrupting hepatic hemodynamics or causing hemodilution.

45f0443a-66a2-4b6a-ad9f-45409137aab1

1

By this means hepatic uptake or release of blood-borne substances can be measured in situ and correlated with hemodynamic parameters. In 13 splenectomized cats, oxygen uptake by the denervated liver was 4.5 +/- 0.3 ml . min-1. 100 g-1 of tissue, representing 54% of total oxygen removed by the splanchnic bed.

45f0443a-66a2-4b6a-ad9f-45409137aab1

2

The hepatic hemodynamics determined by this method are similar to those reported by others in vivo and the metabolic state of the liver remained stable for at least 2 h during which an average of 29 blood samples were taken. Advantages of this preparation over other methods of obtaining similar data are discussed.

2ce18811-718a-4922-9d72-951c6dfaa98a

0

Analysis of pesticide residues by chemical derivatization. II. N-methylcarbamates in natural water and soils. A method for the quantitative determination of several N-methylcarbamates in natural waters and the applicability of the derivative to soil samples using a previously published extraction procedure are described. After extraction of the carbamates from the substrate, the carbamates are hydrolyzed in a 10% methanol-potassium hydroxide solution to form the phenolic hydrolysis products, which are isolated and derivatized with pentafluorobenzyl (PFB) bromide to produce the PFB ether derivatives.

2ce18811-718a-4922-9d72-951c6dfaa98a

1

The PFB derivatives are cleaned up and fractionated on a silica gel microcolumn and determined by electron capture gas-liquid chromatography (GLC). Eight organophosphate pesticides and 2 phthalate acid esters that hydrolyze to phenols or phthalic acid were evaluated as potential interferences and were found not to interfere with any of the carbamates tested.

2ce18811-718a-4922-9d72-951c6dfaa98a

2

Quantitative determinations of 0.1 mug carbofuran and 3-ketocarbofuran and 0.5 mug carbaryl, metmercapturon, and Mobam in a 1 L water sample are possible. Propoxur was not determined at levels less than 1 mug/L due to the short GLC retention time of the derivative and interferences from the reagents at the lower levels.

de0c9c2d-92e6-42e9-96c6-3a34207e5685

0

Separation of pesticide residues from lipids prior to gas-liquid chromatographic analysis. Lipids are separated from dieldrin, endrin, and p,p'-DDE residues by saponification in ethanolic sodium hydroxide, acidification with dilute sulfuric acid, and adsorption chromatography on deactivated alumina, using petroleum ether as the eluant. Dieldrin, endrin, and p,p'-DDE are efficiently recovered (95-102%), and p,p'-DDT is converted to p,p'-DDE, which is then recovered with high yield (90-96%).

de0c9c2d-92e6-42e9-96c6-3a34207e5685

1

Extremely low lipid carryover (less than 0.3-0.5%) is observed for 0.5-1.0 g samples of chicken fat.

ea326513-4f0d-4b06-9157-17a97ae76b78

0

Collaborative study of the Food Chemicals Codex method for the determination of the neutralizing value of sodium aluminum phosphate. Fifteen laboratories participated in a collaborative study to evaluate the Food Chemicals Codex method for the determination of the neutralizing value of sodium aluminum phosphate. The AOAC method for determining the neutralizing value of sodium acid pyrophosphate, sec.

ea326513-4f0d-4b06-9157-17a97ae76b78

1

8.010, was also included in the study. The precisions of the Food chemicals Codex method, based on the between-replicate standard deviation and on one collaborator making one determination, are 1.16 and 3.66, respectively. The Food Chemicals Codex method for the determination of the neutralizing value of sodium aluminum phosphate has been adopted as official first action.

759e12be-6885-4d12-a03a-76f6096ae06f

0

Affinity chromatography of trypsin and related enzymes. I. Preparation and characteristics of an affinity adsorbent containing tryptic peptides from protamine as ligands. An absorbent for the affinity chromatography of trypsin [EC 3.4.21.4] (AP Sepharose) was prepared. The ligand was a mixture of oligopeptides (mainly di- and tripeptides) containing L-arginine as carboxyl termini, and was obtained from a tryptic digest of protamine.

759e12be-6885-4d12-a03a-76f6096ae06f

1

Trypsin was absorbed at relatively low pH (7-4), but was not absorbed at the optimum pH of catalysis (8.2). This was clearly explained on the basis of the pH dependence of the interaction of trypsin with its products. Inactivated trypsin, trypsinogen, and chymotrypsin were not absorbed.

759e12be-6885-4d12-a03a-76f6096ae06f

2

The absorption of active trypsin was interferred with by either benzamidine or urea. From these observations, it is evident that AP Sepharose is an affinity adsorbent. AP Sepharose was useful for purification of commercial bovine trypsin. A preliminary application for the purification of Streptomyces griseus trypsin was also successful.

de613544-3f3b-4d9a-932e-c4f097fc180c

0

Effects on tryptophyl absorption of the ionization of the catalytic carboxyls in hen and turkey lysozymes. The difference spectra of hen and turkey egg-white lysozymes [EC 3.2.1.17] produced by acidification were measured. The difference spectra of both lysozymes had peaks at 295 and 301 nm which are characteristic of tryptophyl residues.

de613544-3f3b-4d9a-932e-c4f097fc180c

1

The pH dependence curves of the extinction differences (delta eplision) at 301 nm and 295 nm for hen lysozyme were identical with the corresponding curves for turkey lysozyme. The pH dependence of delta eplision at 301 nm was analyzed assuming that the extinction at 301 nm is due to Trp 108 only, which interacts with the catalytic carboxyls, Glu 35 and Asp 52.

de613544-3f3b-4d9a-932e-c4f097fc180c

2

The macroscopic pK values of Glu 35 and Asp 52 in both lysozymes thus determined were 6.0 and 3.3, respectively. These values were in excellent agreement with those determined by measuring the pH dependence of the circular dichroic band at 305 nm (Kuramitsu et al. (1974) J. Biochem, 76, 671-683;

de613544-3f3b-4d9a-932e-c4f097fc180c

3

(1975) ibid. 77, 291-301). The pH dependence of delta eplision at 295 nm could not be completely explained in terms of the electrostatic effects of the catalytic groups on Trp 108.

085d2bfc-d5e0-4808-b990-882c563a39f9

0

Resonance Raman scattering from hemoproteins. Effects of ligands upon the Raman spectra of various C-type cytochromes. Resonance Raman spectra were measured for various C-type cytochromes (mammalian cytochrome c, bacterial cytochrome c3, algal photosynthetic cytochrome f, and alkylated cytochrome c) and a B-type cytochrome (cytochrome b5) in their reduced and oxidized states.

085d2bfc-d5e0-4808-b990-882c563a39f9

1

(1) For ferrous alkylated cytochrome c, a Raman line sensitive to the replacement of an axial ligand of the heme iron uas found around 1540 cm=1. This ligand-sensitive Raman line indicated the transition from acidic (1545 cm-1) to alkaline (1533 cm-1) forms with pK 7.9. The pH dependence of the Raman spectrum corresponded well to that of the optical absorption spectra.

085d2bfc-d5e0-4808-b990-882c563a39f9

2

(2) For ferrous cytochrome f, the ligand-sensitive Raman line was found at the same frequency as cytochrome c (1545 cm-1). Accordingly two axial ligands are likely to be histidine and methionine as in cytochrome c. (3) For ferrous cytochrome c3, the frequency of the ligand-sensitive Raman line was between those of cytochrome c and cytochrome b5.

085d2bfc-d5e0-4808-b990-882c563a39f9

3

Since two axial ligands of the heme iron in cytochrome c3 might be histidines. However, a combination of histidine and methionine as a possible set of two axial ligands was not completely excluded for one or two of the four hemes. (4) In ferrous cytochrome b5, two weak Raman lines appeared at 1302 and 1338 cm-1 instead of the strongest band at 1313 cm-1 of C-type ferrous cytochromes.

085d2bfc-d5e0-4808-b990-882c563a39f9

4

This suggests the practical use of these bands for the identification of types of cytochromes. The difference in frequency and intensity between B- and C-types of hemes implies that the low effective symmetry of the heme in ferrous cytochrome c is due to vibrational coupling of ring modes with peripheral substituents rather than geometrical disortion of heme.

9c45e182-e356-4cf1-9b5e-396171f00d61

0

Studies on the microsomal electron-transport system of anaerobically grown yeast. III. Spectral characterization of cytochrome P-450. A carbon monoxide-binding pigment which shows an absorption peak at about 450 nm in the reduced carbon monoxide difference spectrum was purified from the microsomal fraction of yeast grown anaerobically.

9c45e182-e356-4cf1-9b5e-396171f00d61

1

The spectral characteristics of the pigment were practically identical with those of cytochrome P-450 of hepatic microsomes, especially from polycyclic hydrocarbon-induced animals. The pigment was denatured to P-420, and bound with ethyl isocyanide in the reduced state. Although Type I spectral change was not evident, the pigment showed Type II and modified Type II spectral changes upon binding with some organic compounds, as in the case of hepatic cytochrome P-450.

9c45e182-e356-4cf1-9b5e-396171f00d61

2

These observations clearly indicate that the carbon monoxide-binding pigment of yeast microsomes may be designated as cytochrome P-450 of yeast.

42e529a1-3f3f-4926-bc65-3ed89a74296d

0

Polarographic studies on ubiquinone-10 and rhodoquinone bound with chromatophores from Rhodospirillum rubrum. Redox components bound with chromatophores of Rhodospirillum rubrum, and pure samples of ubiquinone-10 and rhodoquinone were studied polarographically at 24 degrees. In a mixture of ethanol and water (4 : 1, v/v) at pH 7, ubiquinone-10 and rhodoquinone had half-wave potentials (E1/2) OF +43 MV and -63 mV, respectively.

42e529a1-3f3f-4926-bc65-3ed89a74296d

1

For both quinones, values of the electron transfer number (n) were 2 , and plots of E1/2 versus pH formed straight lines with slopes of -30 mV/pH in the neutral pH range; thus, values of the proton transfer number (n-a) were estimated to be 1 for both quinones.

42e529a1-3f3f-4926-bc65-3ed89a74296d

2

When bound with chromatophores, ubiquinone-10 and rhodoquinone had E1/2 values of +50 mV (n=2) and -30 mV (n=2), respectively, at pH 7. Values of (n-a) were estimated to be 1 for ubiquinone-10 and 2 for rhodoquinone. A component (POC-170) thought to be one of the active center bacteriochlorophylls (Liac-890) was characterized;

42e529a1-3f3f-4926-bc65-3ed89a74296d

3

it has E1/2 value of -170 mV at pH 7 and its oxidation-reduction is possibly brought about by dehydrogenation-hydrogenation. Conceivably, the oxidation-reduction sites of ubiquinone-10, rhodoquinone and POC-170 partly, if not all, exist on the surface of chromatophore membrane or project outside the membrane, because of their accessibility to the polarographic electrode.

1bc49384-74b6-40f2-830f-23afe9147eff

0

Effect of metal ions in the culture medium on the stearoyl-coenzyme A desaturase activity of Mycobacterium phlei. A particulate fraction prepared from Mycobacterium phlei grown in a metal-deficient medium exhibited a greatly reduced activity of stearoyl-CoA desaturase compared to that from normally grown cells. Metal deficiency, however, had no effect on the FAD-dependent NADPH-cytochrome C reductase activity, which has been suggested to participate in the desaturation process.

1bc49384-74b6-40f2-830f-23afe9147eff

1

When the cells were grown in the deficient medium supplemented with both Fe2+ and Mg2+, the desaturase activity was restored to the normal level. Supplementation with Mg2+ alone promoted growth but did not restore the desaturase activity, whereas Fe2+ alone did cause a significant restoration. Among the various metal ions tested, only Fe2+ and Fe3+ enhanced the formation of desaturase activity in the deficient medium.

1bc49384-74b6-40f2-830f-23afe9147eff

2

When added to the assay medium in vitro, Fe2+ and Fe3+ did not stimulate the desaturase activity of the particulate fraction from the deficient cells. Cultivation in the metal-deficient medium had essentially no effect on the levels of cytochromes in the particulate fraction, but dramatically decreased the non-heme iron content and the amount of a high-spin ferric species exhibiting an ESR signal at g=4.3

1bc49384-74b6-40f2-830f-23afe9147eff

3

. No labile sulfur could be detected in the normal or metal-deficient particulate fractions. It is concluded that the presence of iron ions in the culture medium is necessary for the synthesis and/or assembly of the terminal portion of the desaturase system.

43b477a7-c18e-4d9e-8b8b-b7c8fea1a257

0

Photoaffinity labeling of concanavalin A. Preparation of a concanavalin A derivative with reduced valence. Concanavalin A (Con A) was labeled with p-azidophenyl alpha-D-mannopyranoside under ultraviolet irradiation and the reaction products were separated by affinity chromatography on Sephadex G-100 at pH 5. One of the Con A derivatives thus obtained was characterized as a monovalent dimer at pH 5 and a divalent tetramer at pH 7 by sedimentation equilibrium and equilibrium dialysis, indicating that this photoaffinity labeling did not alter the quaternary structure of Con A.

43b477a7-c18e-4d9e-8b8b-b7c8fea1a257

1

In agreement with these results, the labeled Con A did not show the capacity to precipitate glycogen at pH 5, but it formed precipitates with glycogen at pH 7. Although its hemagglutinating activity was found to be weaker than that of the native Con A, the dose-response cure of the labeled Con A in the mitogenic stimulation of human peripheral lymphocytes was almost identical to that of the native con A.

90151b47-151c-4ef1-b926-af0636decb20

0

Chemical modification of carboxyl groups of fibrinogen and its effect on the binding of cationic detergent. Carboxyl groups of native human fibrinogen were modified with glycine methyl ester and 1-ethyl-3(3-dimethylaminopropyl)carbodiimide. It seemed likely that the modification occurred stepwise. Approximately 26% of the carboxyl groups of fibrinogen was modified finally.

90151b47-151c-4ef1-b926-af0636decb20

1

The modified fibrinogen had no interaction with cationic detergent, and did not form any complex with the detergent. In dilute acid, fibrinogen was observed to show only a slight interaction with cationic detergent. It is probable that the exposed and ionized carboxyl groups are essential for the formation of a complex between fibrinogen and cationic detergent.

c770dcb3-8498-4c4a-a847-47658bedba34

0

Purification and characterization of proteinase inhibitors from adzuki beans (Phaseolus angularis). Two proteinase inhibitors, designated as inhibitors I and II, were purified from adzuki beans (Phaseolus angularis) by chromatographies on DEAE- and CM-cellulose, and gel filtration on a Sephadex G-100 column. Each inhibitor shows unique inhibitory activities.

c770dcb3-8498-4c4a-a847-47658bedba34

1

Inhibitor I was a powerful inhibitor of trypsin [EC 3.4.21.4], but essentially not of chymotrypsin ]EC 3.4.21.1]. On the other hand, inhibitor II inhibited chymotrypsin more strongly than trypsin. The molecular weights estimated from the enzyme inhibition were 3,750 and 9,700 for inhibitors I and II, respectively, assuming that the inhibitions were stoichiometric and in 1 :

c770dcb3-8498-4c4a-a847-47658bedba34

2

1 molar ratio. The amino acid compositions of both inhibitors closely resemble those of low molecular weight inhibitors of other leguminous seeds: they contain large amounts of half-cystine, aspartic acid and serine, and little or no hydrophobic and aromatic amino acids. Inhibitor I lacks both tyrosine and tryptophan residues.

c770dcb3-8498-4c4a-a847-47658bedba34

3

The molecular weights were calculated to be 7,894 and 8,620 for inhibitors I and II, respectively. The reliability of these molecular weights was confirmed by the sedimentation equilibrium and 6 M guanidine gel filtration methods. On comparison with the values obtained from enzyme inhibition, it was concluded that inhibitor I and two trypsin inhibitory sites on the molecule, whereas inhibitor II had one chymotrypsin and one trypsin inhibitory sites on the molecule.

06746f2d-c714-4658-9ed3-cb6452f41adb

0

Mitochondrial malate dehydrogenase of bovine cerebrum. Characterization and mechanisms of inhibition by silver ions. Attempts were made to characterize mitochondrial malate dehydrogenase [L-malate: NAD+ oxidoreductase, EC 1.1.1.37] (M-MDH) purified from bovine cerebrum and to elucidate the mechanisms responsible for inhibition of the enzymic activity by Ag+.

06746f2d-c714-4658-9ed3-cb6452f41adb

1

The molecular weights of the native enzyme and its subunits were 54,000-55,000 and 30,000-32,000, respectively. In general, the physiochemical and catalytic properties of bovine cerebral M-MDH was not very different from those of other corresponding mammalian enzymes. Incubation of the enzyme with Ag+ caused the loss of equivalent amounts of sulfhydryls with a parallel decrease of the enzymic activity.

06746f2d-c714-4658-9ed3-cb6452f41adb

2

When the enzyme was exposed to 2-, 3.5-, and 5-fold molar excesses of Ag+, the enzymic activity showed an initial rapid fall and a subsequent slow restoration to a partially inactivated level (60-70, 45-50, and 15-20% of an untreated control, respectively), while the alpha-helical content of the enzyme fell exponentially with time.

06746f2d-c714-4658-9ed3-cb6452f41adb

3

A 7-fold molar excess of Ag+ reduced both the enzymic activity and the alpha-helical content to a much greater degree and no restoration of the enzymic activity was observed. The Km values of Ag+-inactivated enzyme for NADH and oxaloacetate were the same as those of the native enzyme.

06746f2d-c714-4658-9ed3-cb6452f41adb

4

The data suggest that Ag+ could inhibit enzymic activity both by reducing the structural regularity of the enzyme molecule and by attacking sulfhydryl groups necessary for the catalytic activity of bovine cerebral M-MDH.

33fcd951-f1c0-4b0b-8260-93bc1f9549cc

0

Double-headed protease inhibitors from black-eyed peas. II. Structural studies by optical absorption and circular dichroism. Two new double-headed protease inhibitors from black-eyed peas have amino acid compositions typical of the low molecular weight protease inhibitors from legume seeds. Black-eyed pea chymotrypsin and trypsin inhibitor (BEPCI) contains no tryptophan, 1 tyrosine, and 14 half-cystines out of 83 amino acid residues per monomer.

33fcd951-f1c0-4b0b-8260-93bc1f9549cc

1

Black-eyed pea trypsin inhibitor (BEPTI) contains no tryptophan, 1 tyrosine, and 14 half-cystines out of 75 residues per monomer. The molar extinctions at 280 nm are 2770 for BEPCI and 3440 for BEPTI. The single tyrosyl residue is very inaccessible to solvent in native BEPCI and BEPTI at neutral pH and titrates anomalously with an apparent pK = 12.

33fcd951-f1c0-4b0b-8260-93bc1f9549cc

2

Ionization of tyrosine is complete in 13 hours above pH 12. No heterogeneity of the local environment of the tyrosyl residues in different subunits can be detected spectrophotometrically. The large number of cystine residues leads to an intense and complex near-ultraviolet CD spectrum with cystine contributions in the regions of 248 and 280 nm and tyrosine contributions at 233 and 280 nm.

33fcd951-f1c0-4b0b-8260-93bc1f9549cc

3

An intact disulfide structure is required for appearance of the tyrosyl CD bands. The inhibitors are unusually resistant to denaturation when compared with similar low molecular weight proteins of high disulfide content. All observations are consistent with a far more rigid structure for BEPCI and BEPTI than for a typical protein.

ee1c0293-ddaa-4a24-a7c9-27890b4cd98a

0

Double-headed protease inhibitors from black-eyed peas. III. Subunit interactions of the native and half-site chemically modified proteins. The chemical modification of two new double-headed-protease inhibitors from black-eyed peas, a trypsin-chymotrypsin inhibitor (BEPCI) and a trypsin inhibitor (BEPTI) with dansyl chloride was investigated under various conditions.

ee1c0293-ddaa-4a24-a7c9-27890b4cd98a

1

The NH2-terminal serine of both BEPCI and BEPTI, the 4 lysyl residues of BEPCI, and 4 of the 5 lysyl residues of BEPTI, could not be dansylated in the absence of urea. The single tyrosine per subunit of BEPCI and BEPTI was unreactive even in the presence of urea but could be labeled with half-site reactivity by the Celite method.

ee1c0293-ddaa-4a24-a7c9-27890b4cd98a

2

Lysine, NH2-terminal serine, and tyrosine were reactive in fully reduced, carbamidomethylated BEPCI and BEPTI. Gel filtration was used to study the subunit interactions of BEPCI and BEPTI. At pH 8 or pH 3.0 there is a complex set of multiple equilibria with widely differing rates of attainment.

ee1c0293-ddaa-4a24-a7c9-27890b4cd98a

3

We have found evidence for a rapid dimer-tetramer equilibrium, a distinct moderate rate dimer-tetramer equilibrium, a very slow monomer-dimer equilibrium, and postulate slow isomerization of the two forms of dimer and the two forms of tetramer. The monomer-dimer equilibrium is quite unusual in that the dimer is stabilized by chaotropic ions and even slightly by guanidine HC1.

ee1c0293-ddaa-4a24-a7c9-27890b4cd98a

4

In contrast to the complex pattern seen in native BEPCI, the half-site, dansylated BEPCI exists at similar concentration exclusively as a tetramer at neutral pH.

a8d127d5-8f38-48d0-8519-df61c5bed680

0

Affinity labeling of the primary bilirubin binding site of human serum albumin. A label for the bilirubin binding sites of human serum albumin was synthesized by reacting 2 mol of Woodward's reagent K (N-ethyl-5-phenylisoxazolium-3'-sulfonate) with 1 mol of bilirubin. This yielded a water-soluble derivative in which both carboxyl groups of bilirubin were converted to reactive enol esters.

a8d127d5-8f38-48d0-8519-df61c5bed680

1

Covalent labeling was achieved by reacting the label with human serum albumin under nitrogen at pH 9.4 and 20 degrees. Under the same conditions, no covalent binding to the monomers of several proteins could be demonstrated. The number of binding sites for bilirubin and the label were found to be the same, and competition experiments with bilirubin showed inhibition of covalent labeling.

a8d127d5-8f38-48d0-8519-df61c5bed680

2

The absorption, fluorescence and CD spectra of the label in a complex with human serum albumin were similar to those of the bilirubin human serum albumin complex. However, following covalent attachment to the spectral properties were changed, indicating loss of conformational freedom of the chromophore. Labeling ratios were selected to result in the incorporation of less than 1 mol of label/mol of human serum albumin.

a8d127d5-8f38-48d0-8519-df61c5bed680

3

Under these conditions, labeling is thought to occur primarily at the high affinity binding site.

480a267c-af8e-4d0a-a7aa-662acea66e5f

0

Acylation of subtilisin Carlsberg by phenyl esters. Approximate Hammett reaction constants rho calculated from k2/K8 values of several phenyl esters of N-acetyl-L-phenylalanine, hippuric acid, and beta-phenylpropionic acid are 0.0, 0.4, and 1.0 respectively.

480a267c-af8e-4d0a-a7aa-662acea66e5f

1

To determine whether the lack of substituent effect of k2/K8 with the N-acetyl-L-phenylalanine esters is a result of substituent-insensitive k2 or rate-limiting association of enzyme and substrate, pH-k2/K8 deependences and solvent deuterium isotope effects were determined for certain of the substrates and compared with those found with the corresponding hippurates and beta-phenylpropionates. In the pH range 5 to 8, k2/K8 of the phenyl and 4-nitrophenyl esters of each series is dependent upon the unprotonated form of an enzymatic base of apparent pKa approximately 7.4

480a267c-af8e-4d0a-a7aa-662acea66e5f

2

, identical with the pKa found for the free enzyme. With the phenyl esters of each substrate class, k2/K8 decreased by 2 to 3 times in deuterium oxide compared with water. The results suggest that a step involving a general base-catalyzed proton transfer, almost certainly k2, is rate-limiting with the N-acetyl-L-phenylalaninates, as well as the hippurates and beta-phenylpropionates.

480a267c-af8e-4d0a-a7aa-662acea66e5f

3

Attack by the protein on the latter substrates is prediminantly nucleophilic, judged by the similarity of rho in the enzymatic and reference hydroxide ion-catalyzed hydrolyses. The power rho values for the N-acetyl-L-phenylalaninates and hippurates could result from an electrophilic component in their hydrolytic mechanisms.

f3ce5be7-24a8-4f98-bd39-afab6933adb4

0

Inhibition by superoxide dismutase of methemoglobin formation from oxyhemoglobin. The formation of methemoglobin from oxyhemoglobin in a solution containing photoreduced riboflavin and oxygen was inhibited by superoxide dismutase. The rate of the reaction was pH-dependent in the range of 6.8 to 7.8, increasing as the pH was reduced.

f3ce5be7-24a8-4f98-bd39-afab6933adb4

1

Inhibition by superoxide dismutase was enhanced as the EDTA concentration increased and was dependent on enzymatic activity. Under conditions in which superoxide dismutase inhibition was incomplete, catalase inhibited the reaction but mannitol had no effect. The data support the mediation of methemoglobin formation by superoxide. The hypothesis is offered that superoxide anion reduced the heme-bound oxygen in oxygemoglobin by one electron, permitting the subsequent dissociation of ferrihemoglobin and peroxide.

f3ce5be7-24a8-4f98-bd39-afab6933adb4

2

The ability of superoxide dismutase to inhibit the formation of methemoglobin may represent one of its functions in the mature erythrocyte.