Ribonuclease carboxymethyl

Taborsky (23) [see also Shapira (24)] has described a system based on carboxymethyl cellulose as the exchanger operated in Tris buffer at pH 8 with a sodium chloride gradient. The excellent and adjustable resolution of this system is frequently useful. The principal peak, labeled D by Taborsky, is indistinguishable from ribonuclease-A in the IRC-50 system (see Fig. 1). 

The presence of homoserine, homoserine lactone, and acid hydrolysis of ribonuclease, 50 % inactivated by iodoacetate at pH 2.8, and the poor recovery of methionine provides another example for this type of breakdown of methionine sul-fonium salts (Gundlach et al, 1959b). The same products in varying proportions were observed in the decomposition of methionine carboxymethyl-... 

That c in faet reflects helical content is shown by its rise in proteins for which there is independent evidence that helical content is being increased. The nonaqueous transitions of insulin, native and oxidized ribonuclease, silk fibroin, and oxidized bovine serum albumin (Yang and Doty, 1957) as well as that for carboxymethylated human serum albumin (Bresler... 

The predominant contribution of the folded native structure is amply illustrated by the findings that complete reduction of disulfide bonds and 5-carboxymethylation completely alters the immunochemical reactivity of protein antigens, such as ribonuclease, lysozyme, and other antigens.However, reduction of but two of the four disulfide bonds in ribonuclease had a negligible effect on the ability to precipitate with antibody to native ribonuclease. 

Analogous results have been obtained with reduced-carboxymethyl-ated bovine serum albumin, performic acid-oxidized ribonuclease, re-duced-carboxymethylated lysozyme, and several other proteins. 

Epstein CJ and Anfinsen CB. The reversible reduction of disulfide bonds in trypsin and ribonuclease coupled to carboxymethyl cellulose. J. Biol. Chem. 1962 237 2175-2179. 

The characterization of proteins and their derivatives is outside the scope of this monograph. It is necessary to emphasize, however, that modification of native proteins frequently gives rise to complex mixtures of products. The complexity of the situation is not inunediately apparent solely from the stoichiometry of the modification reaction. The now classical case of the reaction of native bovine pancreatic ribonuclease A with iodoacetic acid at pH 5.5 may be cited in this context. One carboxymethyl group is introduced per molecule of... 

Irradiated ribonuclease is treated with H235S and the non-covalently bound 35S is removed by Sephadex chromatography. At this stage the specific activity of the ribonuclease was 0.089 /xc/mg., of which 0.043 /xc/mg. was caused by /2-labeling determined in a separate experiment. Reduction of this material with mercaptoethanol in 8M urea, precipitation, and carboxymethylation resulted in ribonuclease s having a specific activity... 

Ribonuclease B, globin, R17-bacteriophage coat protein, carboxymethylated protein, subunits from BI component of TYMV tryptic digest of glyceraldehyde 3-phosphaie dehydrogenase of yeast Dipeptides with Leu/Ile as N-terminal residues Several di- and tri-peptides (see Table 2)... 

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