The enzyme d-ribonuclease is antigenic. Antisera, prepared by three different methods, reacted against antigen dilutions up to one million. Apparently the homologous antiserum, when combined with the d-ribonuclease inhibited the activity of the enzyme from 10 to 30 per cent.

The ribonuclease and phosphodiesterase activities of rat liver plasma membranes, purified from the crude nuclear fraction by centrifugation in an A-XII zonal rotor and flotation, were examined and compared. The plasma membrane is responsible for between 65 and 90% of the phosphodiesterase activity of the cell and between 25 and 30% of the particulate ribonuclease activity measured at pH8.7 in t...

Studies of the denaturation of proteins indicate certain characteristics of the forces which normally constrain them in their native chain conformations. In the case of bovine pancreatic ribonuclease, the description of the noncovalent bonds involved has taken on heightened interest following the recent report by White (1) that the integrity of the 4 disulfide bonds does not appear to be prereq...

A method for the preparation of crystalline ribonuclease was described by Kunitz (1) in 1940. Since that time various workers (2-6) have shown that at least some samples of ribonuclease so prepared had, in addition to the ability to degrade ribonucleic acid, the ability to hydrolyze proteins. That the latter was due to contaminants and not to an intrinsic property of the ribonuclease molecule h...

Recent studies have considerably clarified the mechanism ofhydrolysis of ribonucleic acids (RNA) by pancreatic ribonuclease and by spleen phosphodiesterase. Digestion ofRNA with ribonuclease results in the splitting of all pyrimidine-pyrimidine internucleotidic links and of those pyrimidine-purine internucleotidic links which involve C(3w) of the pyrimidine nucleotide (Schmidt et al. 1951; Mark...

1. The ability of crystalline ribonuclease to hydrolyze proteins is due to impurities present in the preparations and not to an intrinsic property of the ribonuclease molecule. The amounts of these impurities vary enormously with different preparations. 2. The dangers inherent in the use of crystalline enzymes as specific tools, without assaying them for all possible interfering impurities, are...

The action of pancreatic ribonuclease is inhibited by a number of mononucleotides (l), of which one of the most effective is cytidine 2’-phosphate (2). We have presented evidence (3) that cytidine 2’-phosphate is a competitive inhibitor of the action of ribonuclease upon either ribonucleic acid or cytidine 2’) 3’ cyclic phosphate, but that the dissociation constant of the cytidine 2’-phosphate-...

Poly(A)-containing messenger RNA isolated from rabbit reticulocytes as estimated by periodate oxidation and condensation with [3H]isoniazid has two oxidizable end groups per molecule of mol. wt. 220000. When the mRNA is subjected to stepwise degradation by beta-elimination, only one oxidizable end-group is found. This indicates that one of the 2',3' hydroxyl end-groups is linked through the nor...