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Query: EC:3.1.27.4 (ribonuclease)
 6,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Ribonuclease hydration in wide concentration and temperature range using differential scanning microcalorimetry and NMR technique was studied. The temperature- concentration equilibrium diagram for H2O--ribonuclease system was suggested. Protein hydration in D2O was shown to be higher than in ordinary water. NMR measurements in dilute protein solutions showed that cooperative temperature denaturation was followed by solvation changes. Models of globular protein hydration are discussed.
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PMID:[Ribonuclease hydration and its heat stability in solutions of H2O and D2O]. 624 23

Heat denaturation of ribonuclease in diluted water solutions was studied by means of proton magnetic relaxation, microcalorimetry and viscosity. It has been shown that heat denaturation of ribonuclease is a one stage process; it involves the whole globule and is accompanied by changes in the state of salvated (water) molecules. A redistribution of water molecules in the hydrate "envelope" of protein changes the character of proton magnetic relaxation of the whole solvent.
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PMID:[Proton magnetic relaxation and thermodynamic parameters of ribonuclease solutions during thermal denaturation]. 624 33

We have designed and synthesized a model pentadecapeptide predicted to have the essential sequence information needed to form a stable and enzymatically active noncovalent complex with bovine pancreatic ribonuclease S-protein. The model peptide sequence, based on the conformational approach of simplifying the native sequence in a manner consistent with retention of essential noncovalent contacts and of secondary structure features, contained alanine at all positions except for Glu 2, Lys 7, Phe 8, Arg 10, His 12, and Met 13. The peptide was synthesized by the Merrifield solid phase method. The circular dichroism spectra of the purified model peptide in water and trifluoroethanol indicated a tendency to form an alpha-helical structure similar to that found for native S-peptide. The model peptide formed a stable complex with ribonuclease S-protein. With 12-fold excess of the peptide, the complex exhibited 36% of the specific activity of fully native ribonuclease S against the substrate cyclic cytidine 2':3'-monophosphate at pH 7.15. The dissociation constant of the model peptide for S-protein was found to be 1.1 x 10(-6) M, compared with 0.1 x 10(-6) M for native S-peptide. Crystals grown of the model peptide-S-protein complex were found to be isomorphous with those of native complex. The activity, stability, and structural integrity of the model complex verify the deductions made about essential sequence information in the NH2-terminal region of ribonuclease. Further, the results emphasize the general usefulness of the conformational approach in designing simplified sequences for other peptides and proteins.
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PMID:Sequence modeling using semisynthetic ribonuclease S. 627 8

The study of the temperature dependence of the hydrolysis of cytidine 2',3'-phosphate by bovine pancreatic ribonuclease A (EC 3.1.27.5) at pH 7.0 by using the pH-stat method showed a transition at 4 degrees C [J. A. Biosca and C. M. Cuchillo (1980) Biochem. J. 189, 655-657]. The breaks found in the Van't Hoff and Arrhenius plots at pH 7.0 were confirmed in the present work by following the reaction spectrophotometrically with a stopped-flow spectrophotometer adapted to the use of sub-zero temperatures. Similar results were found at pH 5.5. In addition it was found that the discontinuity disappears when 40% ethyleneglycol is present in the reaction mixture. However, in this latter instance a discontinuity around 0 degrees C appears in the Arrhenius plot. To explore the possibility that all these effects were due to a conformational transition in the protein, thermal perturbation experiments were carried out with the enzyme. A change in the slope of the plot of delta A290 as a function of temperature was found around 6 degrees C at pH 7.0 but not at pH 5.5. The results reported here can be interpreted as due to a change in the protein structure induced by the change of the structure of water. The studies carried out in the presence of ethyleneglycol also open the way to the cryoenzymological experimentation on ribonuclease.
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PMID:Influence of the structure of water on the hydrolysis of cytidine 2',3'-phosphate catalysed by bovine pancreatic ribonuclease A. 628 86

Bacteria were isolated from lake water, and their ability to remain viable in a dilute, nutrient-deficient environment was tested by a method that permits suspension of test bacteria between two appressed microporous membranes in an aqueous environment. This approach permitted separation of the lake isolates into two categories. Members of the tribe Klebsielleae were shown to have a prolonged survival rate of 40% or better after 24 h, whereas nonsurvivors were not viable for much longer than 24 h. These nonsurvivors belonged to the genera Acinetobacter, Aeromonas, Alcaligenes, Erwinia, Escherichia, Flavobacterium, and Pseudomonas. Differences in ribonuclease and adenosine triphosphatase levels between Escherichia coli (nonsurvivor) and Klebsiella (survivor) cells were detected. At pH 7.5, stressed E. coli cells contained 14% of the adenosine triphosphatase activity detected in the control, whereas at pH 5.5, in the presence of calcium ions, these same cells contained 50% of the control adenosine triphosphatase levels. At pH 7.2, E. coli cells were strongly inhibited by an adenosine triphosphatase inhibitor, bathophenanthroline (88%); oligomycin (64%); and the proton ionophore carbonyl- cyanide-m-chlorophenyl hydrazone (67%). Both sodium azide and valinomycin were only moderately inhibitory (15 and 28%, respectively). Although the ability to scavenge internal endogenous reserves seems important, we postulate that certain enteric bacteria are capable of utilizing acidic conditions (pH 5.5) as an electrochemical gradient to generate necessary high-energy intermediates for prolongation of survival beyond that possible in environments of near-neutraL pH.
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PMID:Bacterial survival in a dilute environment. 645 90

In order to investigate the role of carboxyl groups of a base non-specific ribonuclease from Aspergillus saitoi [EC 3.1.27.1] (RNase M, molecular weight 36,000), the modification of RNase M with a water-soluble carbodiimide, 1-cyclohexyl-3-(2-morpholinyl-(4)-ethyl)carbodiimide(CMC), was studied. The inactivation of RNase M proceeded almost linearly with the incorporation of about 9.5 CMC moieties. The peptide backbone structure of the modified RNase M was practically the same as that of the native RNase M, as assessed from the CD spectra in the region of 200-250 nm. In the presence of competitive inhibitors, adenosine, and cytidine, inactivation of RNase M by CMC was partially inhibited. In the presence of cytidine (1 M), the modification of about 4 carboxyl groups of RNase M proceeded with a slight loss of enzymatic activity (ca. 20%). Further modification inactivated RNase M with the incorporation of ca. 4-5 CMC without any detectable intramolecular peptide bond formation. Therefore, it was concluded that carboxyl groups responsible for enzymatic activity were included among these carboxyl groups protected by cytidine. The logarithm of the half-live of the inactivation of RNase M by CMC was a linear function of log[CMC] with a slope of minus one, indicating that at least one carboxyl group among the modified ones may be essential for catalysis. The digestion of CMC-modified RNase M with carboxypeptidase A eliminated the carboxyl terminal group from the site of CMC modification.
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PMID:Modification of a major ribonuclease from Aspergillus saitoi with 1-cyclohexyl-3-(2-morpholinyl-(4)-ethyl)carbodiimide. 657 11

Camphorquinone-10-sulfonic acid hydrate was prepared by the action of selenous acid on camphor-10-sulfonic acid. Camphorquinone-10-sulfonylnorleucine was prepared either from the sulfonic acid via the sulfonyl chloride or by selenous acid oxidation of camphor-10-sulfonylnorleucine. These reagents are useful for specific, reversible modification of the guanidino groups of arginine residues. Camphorquinonesulfonic acid is a crystalline water-soluble reagent that is especially suitable for use with small arginine-containing molecules, because the sulfonic acid group of the reagent is a convenient handle for analytical and preparative separation of products. Camphorquinonesulfonylnorleucine is more useful for work with large polypeptides and proteins, because hydrolysates of modified proteins may be analyzed for norleucine to determine the extent of arginine modification. The adducts of the camphorquinone derivatives with the guanidino group are stable to 0.5 M hydroxylamine solutions at pH 7, the recommended conditions for cleavage of the corresponding cyclohexanedione adducts. At pH 8-9 the adducts of the camphorquinone derivatives with the guanidino group are cleaved by o-phenylenediamine. The modification and regeneration of arginine, of the dipeptide arginylaspartic acid, of ribonuclease S-peptide, and of soybean trypsin inhibitor are presented as demonstrations of the use of the reagents. The use of camphorquinonesulfonyl chloride to prepare polymers containing arginine-specific ligands is discussed.
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PMID:Camphorquinone-10-sulfonic acid and derivatives: convenient reagents for reversible modification of arginine residues. 692 87

Thermal denaturation of ribonuclease at NMR frequencies 22, 75, and 90 MHz was studied by proton magnetic relaxation. It has been found that the pattern of proton relaxation in denaturated macromolecule is determined by slow exchange tau M approximately 10(-2)--10(-3) sec of "rigidly bound" water molecules and the solvent as a whole.
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PMID:[Magnetic proton relaxation of aqueous solutions of ribonuclease in the temperature region of intramolecular melting]. 713 22

The paper describes a method for preparing extracellular alkaline ribonuclease from Bacillus intermedius (EC 3.1.4.23). The method consists of acid treatment of the culture fluid for selective inactivation of the interfering enzymes, concentration of the enzymic protein by ammonium sulfate precipitation, dialysis against water, chromatography on DEAE-cellulose and phosphocellulose in the steady state, rechromatography on a phosphocellulose containing column, desalting and freeze-drying of the end product. Experimental samples of ribonuclease of 92% purity have been thus obtained.
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PMID:[Isolation and purification of alkaline ribonuclease from Bacillus intermedius]. 724 46

The interactions between proteins and solvent components have been investigated for the sucrose/water system. Thermodynamic and kinetic measurements of the thermal unfolding of alpha-chymotrypsin, chymotrypsinogen, and ribonuclease were performed as a function of sucrose concentration. The alteration in protein-solvent interactions in the presence of sucrose was also studied by density measurements and analyzed by multicomponent thermodynamic theory. Sucrose does not induce a conformational change in three proteins studied, although it does induce a small change in the circular dichroism spectrum of ribonuclease. The enthalpy of thermal unfolding shows little dependence on the concentration of sucrose, while the apparent activation energy of the unfolding process is increased by the addition of sucrose. The results from the protein-solvent interaction study indicate that sucrose is preferentially excluded from the protein domain, increasing the free energy of the system. Thermodynamically this leads to protein stabilization since the unfolded state of the protein becomes thermodynamically even less favorable in the presence of sucrose. The exclusion of sucrose from the protein domain seems to be related to the higher cohesive force of the sucrose water solvent system since all the experimental observations can be correlated with the effect of sucrose on the surface tension of water.
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PMID:The stabilization of proteins by sucrose. 725 92


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