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67f6487a-c5f8-4670-8d61-66fccc7271a0
| 2 |
We have also titrated the primary electron acceptor of the reaction center. Its equilibrium midpoint potential at pH 6.8 is below -450 mV. This is very much lower than the previous estimate for green bacteria, and also substantially lower than values obtained for purple bacteria. Such a low-potential primary acceptor would be thermodynamically capable of direct reduction of NAD+ via ferredoxin in a manner analagous to photosystem I in chloroplasts and blue-green algae.
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297c90e4-c23d-451c-9fc3-5772912fbfba
| 0 |
Reaction of uracil and thymine derivatives with sodium bisulfite. Studies on the mechanism and reduction of the adduct. The rates and equilibria for the addition of sodium bisulfite to uracil, thymine, and their nucleosides have been studied for the pH range 3-9.5. The rate of addition for uracil is proportional to the concentration of sulfite ion and unionized uracil.
|
297c90e4-c23d-451c-9fc3-5772912fbfba
| 1 |
The equilibrium constant (25 degrees C) for the reaction is (1.0 +/- 0.15) X 10(3) 1 - mol-1 for uracil and 0.62 +/- 0.03 1- mol-1 for thymine. A pH of 6-7, with a high bisulfite concentration is suggested for biochemical applications of the uracil reaction.
|
297c90e4-c23d-451c-9fc3-5772912fbfba
| 2 |
The uracil reaction, which proceeds readily under physiological conditions and has a high equilibrium constant, may be a contributing cause of the biochemical effects of bisulfite and sulfur dioxide. Additional evidence on the structure of the thymine-bisulfite adduct has been obtained by nuclear magnetic resonance spectroscopy. This spectrum supports the assignment of structure as dihydrothymine-6-sulfonate.
|
297c90e4-c23d-451c-9fc3-5772912fbfba
| 3 |
The uracil-bisulfite adduct is reduced by sodium borohydride to sodium 3-ureido-propanol-2-sulfonate. This reaction is suggested for the chemical modification of nucleic acids.
|
f57e518e-04e4-476a-a997-30fd74a42c6a
| 0 |
Intramembrane particle aggregation in erythrocyte ghosts. II. The influence of spectrin aggregation. Physicochemical properties of mixtures of spectrin and actin extracted from human erythrocyte ghosts have been correlated with ultrastructural changes observed in freeze-fractured erythrocyte membranes. (1) Extracted mixtures of spectrin and actin have a very low solubility (less than 30 mug/ml) near their isoelectric point, pH 4.8
|
f57e518e-04e4-476a-a997-30fd74a42c6a
| 1 |
. These mixtures are also precipitated by low concentrations of Ca2+, Mg2+, polylysine or basic proteins. (2) All conditions which precipitate extracts of spectrin and actin also induce aggregation of the intramembrane particles in spectrin-depleted erythrocyte ghosts. Precipitation of the residual spectrin molecules into small patches on the cytoplasmic surface of the ghost membrane is thought to be the cause of particle aggregations, implying an association between the spectrin molecules and the intramembrane particles.
|
f57e518e-04e4-476a-a997-30fd74a42c6a
| 2 |
(3) When fresh ghosts are exposed to conditions which precipitate extracts of spectrin and actin, only limited particle aggregation occurs. Instead, the contraction of the intact spectrin meshwork induced by the precipitation conditions compresses the lipid bilayer of the membrane, causing it to bleb off particle-free, protein-free vesicles.
|
f57e518e-04e4-476a-a997-30fd74a42c6a
| 3 |
(4) The absence of protein in these lipid vesicles implies that all the proteins of the erythrocyte membrane are immobilized by association with either the spectrin meshwork or the intramembrane particles.
|
e42dce91-bc43-4118-a701-2988cd800bef
| 0 |
The rate of calcium uptake into sarcoplasmic reticulum of cardiac muscle and skeletal muscle. Effects of cyclic AMP-dependent protein kinase and phosphorylase b kinase. Calcium transport into sarcoplasmic reticulum fragments isolated from dog cardiac and mixed skeletal muscle (quadriceps) and from mixed fast (tibialis), pure fast (caudofemoralis) and pure slow (soleus) skeletal muscles from the cat was studied.
|
e42dce91-bc43-4118-a701-2988cd800bef
| 1 |
Cyclic AMP-dependent protein kinase and phosphorylase b kinase stimulated the rate of calcium transport although some variability was observed. A specific protein kinase inhibitor prevented the effect of protein kinase but not of phosphorylase b kinase. The addition of cyclic AMP to the sarcoplasmic reticulum preparations in the absence of protein kinase had only a slight stimulatory effect despite the presence of endogenous protein kinase.
|
e42dce91-bc43-4118-a701-2988cd800bef
| 2 |
Cyclic AMP-dependent protein kinase catalyzed the phosphorylation of several components present in the sarcoplasmic reticulum fragments; a 19000 to 21 000 dalton peak was phosphorylated with high specific activity in sarcoplasmic reticulum preparations isolated from heart and from slow skeletal muscle, but not from fast skeletal muscle. Phosphorylase b kinase phosphorylated a peak of molecular weight 95000 in all of the preparations.
|
e42dce91-bc43-4118-a701-2988cd800bef
| 3 |
Cyclic AMP-dependent protein kinase-stimulated phosphorylation was optimum at pH 6.8; phosphorylase b kinase phosphorylation had a biphasic curve in cardiac and slow skeletal muscle with optima at pH 6.8 and 8.0. The addition of exogenous phosphorylase b kinase or protein kinase increased the endogenous level of phosphorylation 25-100%.
|
e42dce91-bc43-4118-a701-2988cd800bef
| 4 |
All sarcoplasmic reticulum preparations contained varying amounts of adenylate cyclase, phosphorylase b and a (b:a = 30.1), "debrancher" enzyme and glycogen (0.3 mg/mg protein), as well as varying amounts of protein kinase and phosphorylase b kinase which were responsible for a significant endogenous phosphorylation.
|
e42dce91-bc43-4118-a701-2988cd800bef
| 5 |
Thus, the two phosphorylating enzymes stimulated calcium uptake in the sarcoplasmic reticulum of a variety of muscles possessing different physiologic characteristics and different responses to drugs. In addition, the phosphorylation catalyzed by these enzymes occurred at two different protein moieties which make physiologic interpretation of the role of phosphorylation difficult.
|
e42dce91-bc43-4118-a701-2988cd800bef
| 6 |
While the role phosphorylation in these mechanisms is complex, the presence of a glycogenolytic enzyme system may be an important link in this phenomenon. The sarcoplasmic reticulum represents a new substrate for phosphorylase b kinase.
|
c1ea1ee3-e4ea-4d07-b82d-17e09a2004e8
| 0 |
[Microcolorimetric study of the association of trypsin with a pancreatic inhibitor]. Enthalpy of the association of trypsin with pancreatic inhibitor from bovine pancreas at 25 degrees C as a function of pH and ionic strength is estimated. The dependence of the enthalpy on pH is of an extremal character with a minimum at pH 7.6
|
c1ea1ee3-e4ea-4d07-b82d-17e09a2004e8
| 1 |
(delta H degrees =-10.3 ccal/mole). The increase of ionic strength with the addition of LiCl, KCl and CsCl at pH 7.6 leads to be increase of delta H degrees. Possible mechanisms of enthlpy changes depending on medium conditions are considered.
|
31a0c9e7-1c4e-46c8-9e87-0ba58f09d641
| 0 |
[Partial purification and properties of protease from Torula thermophila]. 11-Fold purified protease preparation is isolated from cultural medium of Torula thermophila UzPT-1 by means of ammonium sulphate precipitation and gel chromatography through Sephadex G-100. Disc polyacrylamide gel electrophoresis revealed two portease components, one of them possessing proteolytic activity.
|
31a0c9e7-1c4e-46c8-9e87-0ba58f09d641
| 1 |
pH interval for protease activity was found to be 3.5-12, the maximal activity was observed at pH 8.5-11, the highest enzyme resistance--at pH 6-8. The enzyme almost completely preserved its activity for 1 hour in distilled water at 60 degrees C. The temperature maximum of the enzyme activity was 70 degrees at pH 8.
|
31a0c9e7-1c4e-46c8-9e87-0ba58f09d641
| 2 |
The enzyme may be referred to proteases of serine nature, because it is completely inactivated with diisopropylphosphofluoridate, but it retains the activity in the presence of chelating agents (EDTA, o-phenantroline, ditizone) and inhibitors of SH-groups (sodium p-chloromercuriumbenzoate, iodoacetic acid). The enzyme was not inactivated with phenylmethylsulphonylfluoride and the trypsin inhibitor from soybean.
|
31a0c9e7-1c4e-46c8-9e87-0ba58f09d641
| 3 |
The protease studied most efficiently hydrolyzed caseine and hemoglobin, in a less degree--human serum albumin and fibrinogen and almost did not attack egg albumin. The enzyme undergoes association-dissociation under pH change during gel filtration through Sephadex.
|
222a215d-e3f6-4cdc-abf6-66a703433f0c
| 0 |
[Various properties of the creatine transport system and the location of creatine kinase in skeletal muscle mitochondria]. Water and creatine contents were studied in rat skeletal muscle mitochondria after their 5 min. incubation in creatine solutions, pH 7.2 or 8.4. The content of water and creatine in mitochondria was found to be higher at pH 8.4
|
222a215d-e3f6-4cdc-abf6-66a703433f0c
| 1 |
, than at pH 72, the creatine content correlated with the water content. Structural creatine analogues, containing aminogroups with pKa greater than or equal to 9.5 or carboxyl groups, inhibited the infusion of creatine into mitochondria more strongly than substances having aminogroups with pKa less than 5. The penetrating form is creatine amphiion;
|
222a215d-e3f6-4cdc-abf6-66a703433f0c
| 2 |
the effect of pH on the permeability is probably due to the activation of the creatine transmitter. Rat skeletal muscle mitochondria contain creatine kinase at both sides of the inner membrane. This conclusion is based on the fact that under conditions, supplying the direct course of the creatine kinase reaction (the incubation medium contains Ca2+ and creatine;
|
222a215d-e3f6-4cdc-abf6-66a703433f0c
| 3 |
pH 7.8), ADP produces the stimulation of mitochondrial respiration up to the oxygen exhausting in a polarographic unit. Similarly, ADP irreversibly stimulates mitochondrial respiration in the presence of 1 mM EDTA, if EDTA and ADP are added after the preincubation of mitochondria in creatine-containing medium and after accumulating small amounts of Ca2+ by mitochondria.
|
e12f9042-996b-4e1d-9460-ddc4326b8ac6
| 0 |
[Isolation and properties of a homogeneous L-asparaginase preparation from Pseudomonas fluorescens AG]. Highly purified L-asparaginase having a specific activity of 500+/- +/-40 IU./mg protein is isolated from Pseudomonas fluorescens AG cells. The purification procedure includes isopropanol fractionation, gel filtration through Sephadex G-100, chromatography on hydroxylapatite and DEAE-cellulose columns.
|
e12f9042-996b-4e1d-9460-ddc4326b8ac6
| 1 |
The asparaginase preparation is homogenous on the basis of polyacrylamide gel electrophoresis data. The pH optimum is found to be 8.0-9.0, isoelectric point and molecular weight are 4.5+/-0.05 and 70,000+/-5,000 respectively, Km for L-asparagine being-4.1-10(-4)M. The enzyme does not hydrolyse L-glutamine.
|
e12f9042-996b-4e1d-9460-ddc4326b8ac6
| 2 |
The hydrolysis rate of D-glutamine is less than 1% of the deamydation rate of L-isomer. p-Chloro-mercurium benzoate at a concentration of 10(-4) M completely inhibits the asparaginase activity. Asparaginase from Ps. fluorescens AG possesses and antileucosic activity, inhibiting 3H-thymidine incorporation into DNA of Berkit lymphoma cells.
|
0da9ea5c-e8db-42f3-a7fd-a5e2a20f32f1
| 0 |
[Analysis of sheep blood serum haptoglobin]. Three types of haptoglobin (Hp), differing in the number of bands of Hp--Hb complex on polyacrylamide gel electrophoregramm are found in sheep blood serum. HpA, HpB and HpC fractions included one, two-three and six-eight bands respectively.
|
0da9ea5c-e8db-42f3-a7fd-a5e2a20f32f1
| 1 |
A modified procedure for the HpC isolation is described. Effects of urea, sodium dodecylsulpate, beta-mercaptoethanol, pH and maleinization on the behaviour of HpC under polyacrylamide gel electrophoresis is studied. The data obtained suggest that the HpC molecule consists of two subunits (of alpha and beta types), bound with S--S bounds in an alphabeta-dimer, which form a whole HpC molecule for the expense of non-covalent bonds.
|
b30f83db-aad6-44b7-ab8d-06d15e12dd52
| 0 |
[Reaction ability and alkylation kinetics of sulfhydride groups of soluble succinate dehydrogenase]. Inhibition kinetics of succinate--an acceptor of oxidoreductase activity of soluble succinate dehydrogenase by N-ethylmaleimide is studied. The alkylation reaction is described by the kinetic equation of the first order, its stechiometric coefficient being 1.
|
b30f83db-aad6-44b7-ab8d-06d15e12dd52
| 1 |
The binding of enzyme sulphhydride groups by p-chloromercuriumbenzoate blocks the enzyme alkylation and its inhibition by oxaloacetate. Succinate protects succinate dehydrogenase from the inhibitory effect of N-ethylmaleimide. The reaction of the enzyme with an alkylating agent in the presence of different substrate concentrations corresponds kinetically to the model, according to which a sulphhydride group acts in the active site of the enzyme.
|
b30f83db-aad6-44b7-ab8d-06d15e12dd52
| 2 |
pKa of this group is 7.0 at 20degreesC. The dependency of the maximal substrate oxidation reaction rate and that of the enzyme alkylation rate on pH coinside at the pH range 5.8--7.8. The presence of anions in the alkylation medium decreases the reaction ability of the active site with respect to N-ethylmaleimide.
|
b30f83db-aad6-44b7-ab8d-06d15e12dd52
| 3 |
A mechanism of the initial stage of succinate oxidation with the cooperation of the sulphhydride group of the enzyme active site is postulated.
|
7dcc3aed-a454-463f-b079-2ac84d4a5bf0
| 0 |
[Effect of IAA on the photophosphorylation of pea isolated chloroplasts]. Effect of IAA (10(-10)-10(-3) M) on photophosphorylation, NADP reduction and the oxygen exchange is investigated. It is shown that low concentrations of IAA (10(-10)-10(-7) M) increase the photophosphorylation reaction and the flow of electrones to NADP under the phosphorylation conditions in the chloroplasts, and their effect on the O2 exchange is not the same in different types of photophosphorylation.
|
7dcc3aed-a454-463f-b079-2ac84d4a5bf0
| 1 |
It is supposed that the effect of IAA on the photophosphorylation is connected with H292 metabolism in chloroplasts and with catalase and peroxidase functions.
|
963b7526-3b7e-4731-a9f8-1413b8bfa094
| 0 |
[Purification, molecular multiplicity and kinetic properties of "biosynthetic" L-threonine dehydratase from E. coli K-12]. "Biosynthetic" L-threonine dehydratase was purified to homogeneous state with yield 29% of total activity from E. coli K-12. The cells were disrupted by means of ultra sound.
|
963b7526-3b7e-4731-a9f8-1413b8bfa094
| 1 |
Nucleic acids and nucleoproteins were precipitated with protamine sulphate, the proteins were fractioned with (NH4)2SO4, by gel filtration through Sephadex G-25 followed by chromatography on DEAE-cellulose using stepways elution by changing the pH-values. The homogenity of the enzyme was shown by polyacrylamide gel disc electrophoresis in the presence of dodecylsulphate.
|
963b7526-3b7e-4731-a9f8-1413b8bfa094
| 2 |
The enzyme consists of equal subunits having a molecular weight about 57000. The polyacrylamide gel disc electrophoresis had shown that the native enzyme consists of a set of oligomeric forms. The multiplisity of molecular organization of the enzyme was relfected in complicated kinetic behavior: at pH greater than 9 on the plots of initial reaction rate (upsilon) versus initial substrate concentration ([S]0) there were four inflexion points (two intermediate plateaux) the position and deepness of which depended on enzyme concentration.
|
963b7526-3b7e-4731-a9f8-1413b8bfa094
| 3 |
Kinetic properties of the highly purified enzyme and the enzyme in crude cell extracts at pH 9.3 and 7.4 were identical. At pH 8,3 on the upsilon versus [S]0 plots appeared two inflexion points (one intermediate plateau), the position of which practically did not depend on enzyme concentration in the reaction mixture but strongly depended on the enzyme concentration in the stock solution.
|
963b7526-3b7e-4731-a9f8-1413b8bfa094
| 4 |
Repeated polyacrylamide gel disc electrophoresis of several oligomeric forms isolated by the first electrophoresis had shown that oligomeric forms underwent a slow polymerization. It is suggested that "biosynthetic" L-threonine dehydratase from E. coli K-12 is a set of multiple oligomeric forms having different kinetic parameters. Probably, each form of the enzyme has a "simple" kinetics characterized by hyperbolic or sigmoidal shape of upsilon versus [S]0 plots.
|
963b7526-3b7e-4731-a9f8-1413b8bfa094
| 5 |
The rate of equilibrium between the oligomeric forms is small in comparison with the enzyme reaction velosity, that lead to the complex kinetic curves appearing as a result of summing up the kinetics inherent to the individual forms.
|
55187c91-cf07-404e-b809-06deaaaf3449
| 0 |
[Purification and some properties of electrophoretic variants of 6-phosphogluconate dehydrogenase from rat erythrocytes]. Purification procedure of electrophoretic variants FF and SS of 6-phosphogluconate dehydrogenase (6-PGD) is described. The method includes (NH4)2SO4 fractionation and chromatography on DEAE- and CM-celluloses. Isoenzymes were purified about 5000 fold, and were found to be homogenous by disc electrophoresis in 7% polyacrylamide gel.
|
55187c91-cf07-404e-b809-06deaaaf3449
| 1 |
It was found by comparative studies of activities of variants FF and SS, that pH optimum was 8.2 for variant FF and 8.8 for variant SS. Km for 6-phosphogluconate were found to be 17,5-10(-5) M for variants SS and FF respectively.
|
723741ec-008e-4db7-b90e-514b0beb8284
| 0 |
[Comparative study of glutamate dehydrogenases of Chlorella]. The kinetic properties of the constitutive double specific glutamate dehydrogenase (NAD(P)--GDH) and the inducible NADP-specific glutamate dehydrogenase (NADP--GDH) of Chlorella pyrenoidosa Pringsheim 82T (thermophilic strain) in a deaminating reaction have been studied. NAD(P)-GDH behaves in a deamination as a Michaelis-Menten enzyme.
|
723741ec-008e-4db7-b90e-514b0beb8284
| 1 |
NADP-GDH displays some lag-period before a steady-state phase. The duration of this lag depends on a substrate concentration. Besides that, an effect of all the substrates on a heat inactivation of both GDH and a product inhibition have been studied. All the substrates except the reduced co-factors protect effectively GDH from the heat inactivation, especially the thermolabille NADP-GDH.
|
723741ec-008e-4db7-b90e-514b0beb8284
| 2 |
On the contrary, NAD(P)-H promote the heat inactivation of both GDH. The product inhibition analysis shows that the inducible NADP-GDH acts in vivo as a synthetic enzyme. In the previous paper (V. R. Shatilov et all., 1974, Dokl. Acad. Nauk USSR, 216,223) it was shown for the constitutive GDH that p-CMB strongly inhibited a desamination and slightly (if any) affect an amination.
|
723741ec-008e-4db7-b90e-514b0beb8284
| 3 |
It this paper it is shown that action of p-CMB on the amination depends on the presence of NAD+ (not NADP+ or L-glutamate). p-CMB and NAD+ affect tha amination in a strongly sunergetic manner. Some suggestions about the intracellular localization of chlorella GDH are made.
|
ab718c73-d5d8-4509-a8d8-f7c413f7cb9c
| 0 |
[Fibril formation in solutions of solubilized collagen]. Influence of the preparations of bacterial proteinases, protorisine and prototerrisine, was studied on the stability of the mature collagen of beef skin. The chemical composition of the tissue has been shown to be changed by these enzymes inconsiderably. The tissue treated by orisine and terrisine is completely dissolved in 0.5
|
ab718c73-d5d8-4509-a8d8-f7c413f7cb9c
| 1 |
M acetic acid (solubilized collagen). When the solutions of such collagen are heated to 37 degrees within the pH range from 4 to 10 at the ionic strength of 0.25 fibrils are formed. Under electron microscope fibres are cross-striated that is typical of native collagen fibres with periodicity of about 640 A.
|
ab718c73-d5d8-4509-a8d8-f7c413f7cb9c
| 2 |
After chilling to 4 degrees, a part of fibrils is dissolved again. Nephlometry was used to study the rate of fibril formation as a function of pH and temperature values. A conclusion has been drawn that the mature collagne dissolved after incubation with bacterial proteinases is close to the acid-soluble collagen fraction in the ability to produce fibres upon heating.
|
4b7c0bc7-8616-4725-81e9-71d1e313c8f3
| 0 |
PAH clearance, sodium excretion, and PAH extraction ratio in acidotic near-term lambs treated with hypertonic sodium bicarbonate. The electrolyte changes and renal hemodynamic adjustment to hypertonic sodium bicarbonate (NaHCO3) correction of a metabolic acidosis were studied in 4 neonatal lambs and in 2 controls. PAH clearance increased from 0.92
|
4b7c0bc7-8616-4725-81e9-71d1e313c8f3
| 1 |
to 1.65 ml/min/kg (p less than 0.05), urine flow from 0.37 to 0.61 ml/min/kg (p less than 0.05), and Na excretion from 8.4 to 23.7 muEq/min/kg (p less than 0.05) during the NaHCO3 infusion. These increases were transient and returned to pre-infusion levels following NaHCO3 infusion.
|
4b7c0bc7-8616-4725-81e9-71d1e313c8f3
| 2 |
Calculation of Na intake and output revealed a net retention of 5.1 mEq/kg in the study lambs which was reflected in a rise of serum Na and osmolarity (Osm) during the post-NaHCO3 -infusion period. The extraction ratio of sodium p-aminohippurate (EPAH) and its relationship to arterial pH were studied in 4 additional lambs.
|
4b7c0bc7-8616-4725-81e9-71d1e313c8f3
| 3 |
The EPAH did not change with metabolic acidosis but for unknown reasons, the infusion of NaHCO3 resulted in a temporary depression of EPAH (p less than 0.001).
|
6b19ce7d-854b-449e-ae2c-1c66c6a2babd
| 0 |
On the proteolytic acitivity of ribosomes. The presence of a proteinase on polysomes, isolated from rat liver has been demonstrated. The proteinase was not removed from polysomes upon treatment of the latter with 0,5 M ammonium chloride. The pH optimum of the enzymes is at pH 7,0.
|
9d7bb852-968e-486d-b611-3a9c6d51fdde
| 0 |
[Correction of plasma hemoglobin measurements in calculating a hemolysis index]. A "haemolysis index" may be defined from plasma haemoglobin concentration. This is useful in evaluating the consequences of the artificial kidneys and lungs (pumps and circuitry). Measurements must be taken repeatedly, and corrections made for variations in plasma volume from standard conditions (haematocrit or total haemoglobin) to obtain meaningful comparisons. The "haemolysis index" must take into account the number of passages through the circuit.
|
6d7aecaf-4323-45d2-820b-ae56aaffbbfa
| 0 |
[Study of the osmotic behaviour of human platelets]. Observation of the behaviour of platelets in hypotonic media affords an approach to the evaluation of their fragility. It should be possible to apply such a test to various fields such as the study of rheological properties of platelets, the investigation of certain pathological cases and eventual alterations during storage. The curve obtained reflects a continuous distribution of platelet osmotic fragility.
|
06aa4af5-4070-44b3-87f3-8f1832bb7f75
| 0 |
Oxygen transport by haemoglobin. A comparison of whole blood, washed erythrocytes and haemoglobin solution. The properties of haemoglobin oxygen transport were compared under three different conditions: red cell in its natural medium, i.e. plasma (whole blood), washed red cell and haemoglobin A, the former suspended, the latter solved in an iso-osmotic tris buffer.
|
06aa4af5-4070-44b3-87f3-8f1832bb7f75
| 1 |
The oxygen haemoglobin affinity (expressed as P50) and the respiratory Bohr effect variations were studied with modified media and unchanged pH and 2,3-diphosphoglycerate (2,3-DPG) concentration. Provided they are refered to intra-erythrocytic pH, none of these values were changed when varying environment. These results suggest that the three major ligands (H+ ions, 2,3-DPG and CO2) interaction with haemoglobin is largely predominant upon other factors which would interfere, and can completely account for oxygen transport by haemoglobin.
|
6f93739c-1365-4436-a6fb-c8a9815af6f2
| 0 |
Kinetics of the disordered chain-to-beta transformation of poly(L-tyrosine) in aqueous solution. The kinetics of the transformation of poly(L-tyrosine) from the disordered chain to the intramolecular beta structure in aqueous solution has been studied. The reaction is induced by an isothermal pH jump and is followed by conventional circular dichroism methods.
|
6f93739c-1365-4436-a6fb-c8a9815af6f2
| 1 |
Upon application of curve-fitting procedures, it is found that the kinetics are poorly represented by a single first-order process, but a two-step sequential first-order equation is adequate. Sharp pH-dependent maxima in the phenomenological rate constants and in the fractional amplitude of the rapid step were found.
|
6f93739c-1365-4436-a6fb-c8a9815af6f2
| 2 |
It is proposed to attribute these phenomena to a transition in initial states which is shown to occur over the same pH range within the domain of the disordered-to-beta transition. No sigmoid transient curves were observed, indicating that no slow nucleation events are discernible in this system.
|
6f93739c-1365-4436-a6fb-c8a9815af6f2
| 3 |
These observations contrast strikingly with the mechanism elaborated for beta formation in (Lys)n [R. Hartman et al., J. Mol. Biol. 90 (1974) 415].
|
31993dab-708c-4dd7-ac4c-3e443660581d
| 0 |
Thermodynamic investigations of proteins. I. Standard functions for proteins with lysozyme as an example. A direct method is proposed for obtaining thermodynamic standard functions for native and denatured proteins using experimental data from scanning calorimetry, isothermal calorimetry and potentiometric titrations. The possibility of this approach is demonstrated on the example of lysozyme in the range of pH 1.5
|
31993dab-708c-4dd7-ac4c-3e443660581d
| 1 |
-7.0 and temperature 0-100 degrees C. Tests for the validity of the obtained functions of enthalpy and entropy are presented in the form of cyclic processes using experimental data obtained from thermodynamically different pathways. The Gibbs function is checked by comparison with results of an independent method. The methodic problems in determining and checking standard functions for proteins are discussed in detail.
|
457dca84-2c7e-46ba-bcec-f9dd1ecc41bd
| 0 |
Thermodynamic investigations of proteins. III. Thermodynamic description of lysozyme. Standard functions of enthalpy, entropy and the Gibbs energy of native and denatured lysozyme in the range of 0-100 degrees C and pH 1.5-7.0 are represented in three-dimensional projections. The denaturational Gibbs energy change reaches 16 kcal mol-1 at conditions of maximal protein stability (0 degrees C, pH 4.5
|
457dca84-2c7e-46ba-bcec-f9dd1ecc41bd
| 1 |
-7.0) and equals 14.5 kcal mol-1 at 25 degrees C and neutral pH. This result was found to be in agreement with the data reported from guanidine hydrochloride denaturation studies. Partial thermodynamic functions of the conformational and ionizational changes of the protein are obtained from entropy and Gibbs-energy changes in denaturation.
|
457dca84-2c7e-46ba-bcec-f9dd1ecc41bd
| 2 |
The conformational partial entropy and Gibbs-energy change are found to be independent of pH. The pH-dependent partial ionizational entropy and Gibbs-energy changes are induced by normalization of the ionization behaviour of buried groups and cause a decrease of protein stability.
|
0fc20e32-f18c-4161-9161-3f04c5a6df80
| 0 |
The self-association of adenosine-5'-triphosphate studied by circular dichroism at low ionic strengths. The self-association of adenosine-5'-triphosphate (ATP) was studied as a function of pH, additional counterions, concentration and temperature. Circular dichroism measurements were employed as a measure of the base-stacking.
|
0fc20e32-f18c-4161-9161-3f04c5a6df80
| 1 |
The self-association of ATP is pH dependent with the protonation of the adenine ring helping stabilize the association. Highly charged counterions alter this aggregation. At pH 2.8 and 20 degrees C, a dimerization constant of 88 M-1 is obtained, while an isodesmic model leads to an equilibrium constant of 158 M-1.
|
0fc20e32-f18c-4161-9161-3f04c5a6df80
| 2 |
With increasing pH, the association constants decrease. At pH 2.8 there is a very strong temperature dependence of the CD amplitude. These results indicate the existence of additional electrostatic stabilization for the stacking of the adenine rings. At acidic pHs, models are proposed to explain this high degree of stability and a calculation of the approximate electrostatic contribution to the aggregation shows it to be of the proper magnitude.
|
9baeed5a-621d-435e-96c4-57b4094921ea
| 0 |
Studies on immobilized trypsin in high concentrations of organic solvents. Trypsin was covalently immobilized on porous glass in the presence and absence of a specific substrate and reacted in various organic solvents of different dielectric constants. Optimum solvent concentration, pH profile, Km(app), Vmax(app), productivity versus temperature, activity, and reaction rates were determined.
|
9baeed5a-621d-435e-96c4-57b4094921ea
| 1 |
Reaction rates of six lysyl dipeptides were compared. Crystalline trypsin was dansylated for studies by nanosecond fluorescence techniques to determine the effects of introducing high concentrations of organic solvents on the molecule. The results indicated that greater reaction rates were observed with dipeptides having more acidic carboxyl terminal groups.
|
9baeed5a-621d-435e-96c4-57b4094921ea
| 2 |
The data also indicated that greater reaction rates were observed in higher concentrations of solvents of lower dielectric constants. Nanosecond fluorescence spectroscopy of trypsin in high concentrations of a low dielectric constant solvent indicated major dehydration even though maximal enzyme activity was achieved under these conditions.
|
1a09bf89-728a-4b12-a4f2-cd0177caf13a
| 0 |
Enzyme immobilization on fibrin. The following conclusions can be drawn concerning the utilization of fibrin to immobilized enzyme systems. Fibrin can be used both as a powder or membrane, to covalently immobilize trypsin with retention of activity. Carbon-14 labeled trypsin can be used to estimate the amount of immobilized enzyme on a proteinaceous support.
|
1a09bf89-728a-4b12-a4f2-cd0177caf13a
| 1 |
Significant amounts of noncovalently coupled (adsorbed) enzyme are present on the surface of the support. Esterase activity of the immobilized labeled trypsin was inversely proportional to the amount of attached enzyme. Optimum TAME hydrolysis occurred at pH 8-8.4. The storage stability of trypsin was enhanced. Inhibition of trypsin esterase activity occurred at substrate concentrations greater than 30mM.
|
b84d70ca-3bd2-4a9a-8ad2-127bdc2397d4
| 0 |
[Neuro-muscular synapse ultrastructure in the Lambert-Eaton myasthenic syndrome]. A study was made of the ultrastructure of the neuro-muscular synapses in the patients with the myasthenic Lambert-Eaton syndrome. Most of the synapses displayed an increased content of synaptic vesicles in the axon terminals, and the anastomosing synaptic folds were increased in number and depth. Local destructive changes were found in the terminals of some synapses. The data obtained confirmed the fact that this syndrome was underlied by disorder of the transmitter release from the presynaptic structures.
|
5a8019f9-d34b-41ce-9730-431678be23db
| 0 |
Prostaglandins in pyometrial fluid from the cow, bitch and ferret. 1 Pyometra is a disorder of the uterus usually associated with bacterial infection plus obstruction. 2 Large quantities of fluid often collect in the uterus during this condition. 3 Pyometrial fluid obtained from three species was found to contain prostaglandin F2alpha, usually in large quantities. 4 Prostaglandin E2 was present in smaller quantities in five of the six samples. 5 These findings are discussed in relation to the known occurrence of prostaglandins in inflammatory fluid, and to the problem of infertility.
|
3ca7b088-30b0-4e47-9e86-56c6a4e9942a
| 0 |
Assessment in the guinea-pig ileum and mouse vas deferens of benzomorphans which have strong antinociceptive activity but do not substitute for morphine in the dependent monkey. 1 Four benzomorphans which have potent antinociceptive activity in the hot-plate and writhing tests in the mouse but do not suppress or precipitate withdrawal symptoms in the morphine-dependent monkey, have been examined for their pharmacological actions in the guinea-pig ileum and mouse vas deferens.
|
3ca7b088-30b0-4e47-9e86-56c6a4e9942a
| 1 |
2 In the guinea-pig ileum their agonist potencies are 1.5 to 400 times greater than that of normorphine of morphine whereas in the mouse vas deferens their potencies relative to morphine are 0.3 to 100. They exhibit no antagonist activity in either preparation. Benzomorphans which substitute for morphine in the morphine-dependent monkey do not show such differences between their relative potencies in the guinea-pig ileum and mouse vas diferens.
|
3ca7b088-30b0-4e47-9e86-56c6a4e9942a
| 2 |
3 The relative potencies of the four benzomorphans to inhibit stereospecific [3H]-dihydromorphine binding by membrane fragments from rat brain, are more closely related to their relative agonist potencies in the mouse vas deferens than to those found in the guinea-pig ileum. 4 In order to antagonize the agonist actions of these benzomorphans, naloxone is required in concentrations which are 3 to 7 times higher than those needed for the antagonism of normorphine or morphine or of benzomorphans which suppress abstinence in morphine-dependent monkeys.
|
3ca7b088-30b0-4e47-9e86-56c6a4e9942a
| 3 |
5 It may be possible to use the three assays, namely, ratio of relative agonist potency in mouse vas deferens to that in guinea-pig ileum, ratio of relative agonist potency to relative affinity to opiate receptors and the concentration of nalozone required for antagonism, for the prediction of the potential of new compounds to produce physical dependence.
|
f390f28c-306a-44eb-94f2-33c98d9d3126
| 0 |
The actions of flupenthixol upon 5-hydroxytryptamine-induced aggregation and the uptake of 5-hydroxytryptamine and dopamine by human blood platelets. The effects of the alpha- and beta-isomers of flupenthixol on 5-hydroxytryptamine (5-HT)-induced platelet aggregation and on 5-HT and dopamine uptake were investigated. Alpha-Flupenthixol was 185 times more potent than the beta-isomer as an inhibitor of platelet aggregation. In contrast both isomers were equipotent as inhibitors of uptake of 5-HT and dopamine. The data suggest that 5-HT-induced aggregation and uptake are separate processes.
|
c7e6ae86-929a-44b8-a919-9c130ca8c60e
| 0 |
Evolution of functional respiratory disorders in different types of pneumoconiosis. Three homogeneous groups of patients with silicosis, coal workers' pneumoconiosis and arc welders' pneumoconiosis had been reexamined after an interval of six years. The same examinations were repeated on each occasion with the purpose of evaluating the evolution of radiographic and functional changes.
|
c7e6ae86-929a-44b8-a919-9c130ca8c60e
| 1 |
The clinical course, roentgenographic findings and results of function tests differed in the three groups. In silicosis and coal workers' pneumoconiosis the roentgenographic changes showed distinct progression. This progression was less evident in coal workers' pneumoconiosis, but deterioration of pulmonary function was more pronounced than in silicosis, apparently due to emphysema.
|
c7e6ae86-929a-44b8-a919-9c130ca8c60e
| 2 |
In pneumoconiosis of welders roentgenographic changes showed a clear tendency to regression and respiratory function was not impaired.
|
1394457c-4390-46ff-9e3e-8c33fd1b28b6
| 0 |
Developmental variations of tyrosine hydroxylase and acetylcholinesterase in embryonic and post-hatching chicken sympathetic ganglia. The developmental variations of tyrosine hydroxylase (TH) and of acetylcholinesterase (AChE) were studied in embryonic and post-hatching chicken sympathetic ganglia. Different levels of TH activity were found in two different flocks of White Leghorn chicken, which are probably dependent on genetic differences.
|
1394457c-4390-46ff-9e3e-8c33fd1b28b6
| 1 |
These enzymatic differences, however, do not become apparent before hatching and may indicate a combined effect of genetic variation and functional demands. During the period of incubation, TH activity is characterized by a pronounced and steady increase from the twelfth day of incubation up to day 2 after hatching.
|
1394457c-4390-46ff-9e3e-8c33fd1b28b6
| 2 |
This corresponds to a period of intense maturation of the sympathetic neuron. In the period following hatching, the 'fourth day fall phenomenon' previously described by us for DOPA decarboxylase (DDC), dopamine-beta-hydroxylase (DBH), and monoamine oxidase (MAO) is not seen in the TH curve. Instead, TH activity tends to remain constant between days 2 and 14 after hatching (ah).
|
1394457c-4390-46ff-9e3e-8c33fd1b28b6
| 3 |
Both ganglionic protein and weight remain constant in this period, indicating a phase of general pause in protein synthesis. AChE activity increases steadily from the eighth until the twenty-first day of incubation. A sudden and significant drop in AChE activity was found at day 2 ah followed by a period of rapid increase at day 3 ah and a levelling of activity up to day 30 ah.
|
1394457c-4390-46ff-9e3e-8c33fd1b28b6
| 4 |
Comparing the present variations to those observed in our previous studies on DBH, a temporal relationship between TH and DBH activity is observed during the phases of synaptogenesis and maturation but not during the phase of intense functional activity. Our results strongly suggest that before hatching in chick embryo sympathetic ganglia, the cholinergic presynaptic terminals play a role in regulating the development of the adrenergic neurons.
|
1394457c-4390-46ff-9e3e-8c33fd1b28b6
| 5 |
In the period following hatching, however, the DBH and TH levels in cell bodies seem to be principally regulated by the functional activity. This results in depletion of DBH, but not TH, through liberation along with the neurotransmitter at the periphery. Depletion of DBH at the terminals may result in increased transport and thereby depletion in the cell body.
|
1394457c-4390-46ff-9e3e-8c33fd1b28b6
| 6 |
This mechanism is probably responsible for the difference in the profiles of activity of DBH and TH in the cell bodies observed in the first week after hatching.
|
42f77755-d4b4-4ad6-8e67-1bd8dee46030
| 0 |
[Erythrocyte stroma included in polyacrylamide gel. Applications to affinity chromatography]. Stromata prepared with human or animal red blood cells are suspended in acrylamide solution. Gel as prepared for electrophoresis is dispersed, before use, and can be used in chromatographic columns for the retention of agglutinins. Lectins, e.g., where first absorbed and then eluted with solution of inhibitory sugar or with acid buffer. Some applications are mentioned.
|
923d98f4-3dfe-46c0-a5d8-5e814bbcf28a
| 0 |
[Value of the "gastric chamber", new technic performed ex vivo, for the study of the gastric mucosa of the rat]. The "gastric chamber" technique, performed in the anaesthetised rat, enables the study of gastric mucosal fragility induced by doses of phenylbutazone, which do not themselves cause ulceration or exulceration.
|
923d98f4-3dfe-46c0-a5d8-5e814bbcf28a
| 1 |
The perfusion of buffered solution at pH 2-8 into the gastric chamber shows that prior oral administration of phenylbutazone 50 mg/kg increases the fragility of the mucosa. The optimal delay separating this administration from the time of experimentation is 6 hours. The effects seen are essentially vascular disorders.
|
dc2e40fe-3a24-4fa2-8bfb-a4d5accf6d4a
| 0 |
[Dopamine of the caudate nucleus in Perodictious potto, Macaca mulatta and Macaca fascicularis]. The dopamine, dopac and tyrosinehydroxylase contents of the caudate nucleus in the prosimian Perodicticus potto and in the simii Macaca mulatta and M. fascicularis have been estimated. The results do not support the hypothesis according to which the sluggishness of the potto is somehow related to a low dopamine content of part of the extrapyramidal system as found in the Parkinson-syndrome.
|
c3f9c9f3-32ee-4e81-87dd-a892844a5ec5
| 0 |
[The effect of activator on the esterase activity of plasmin obtained by streptokinase]. In the esterasic dosage of plasminogen, the authors aim to determine the optimal ratio between the amount of streptokinase to add and of plasminogen itself. It is essential that the activator formation be reduced, which explains the dissociations obtained with other methods.
|
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