Ribonucleic acids denaturation

Because of their relatively low molecular weight (70 to 90 nucleotide residues), transfer ribonucleic acids are of special interest for 13C NMR investigations [769, 778, 782-784] of nucleic acids. Using a tube of 20 mm o.d., a sample of thermally denatured yeast... 

Henley, D. D., Lindahl, T., et al. (1966). Hydrodynamic changes accompanying the thermal denaturation of transfer ribonucleic acid. Proc. Natl. Acad. Sci. USA 55(1), 191—198. 

El-FFF is a technique devoted to the fractionation of proteins which is reflected in the number of papers applying this technique to protein separations. The possibilities of El-FFF were first demonstrated by Caldwell for the separation of albumin, lysozyme, hemoglobin, and y-globulin in two different buffer solutions (pH 4.5 and 8.0) [35]. Later, the performance of an El-FFF channel with flexible membranes [36], a channel with rigid membranes [256], or a circular channel [260] for the separation of proteins were described. In these studies, human and bovine serum albumin, y-globulin (bovine), cytochrome C (horse heart), lysozyme (egg white) and soluble ribonucleic acid (t-RNA), as well as denaturated proteins, were successfully separated. 

Enzymatic activity, however, is not merely associated with covalent structures, but chiefly with tertiary structure which is still more difficult to determine. The crucial role of tertiary structure is proved by the fact that denaturation brings about inactivation. Even with proteins which may be reversibly denatured, such as chymotrypsin and trypsin, activity is lost as long as denaturation persists. Ribonuclease appeared for a while to be an exception, since it was still active in 8 M urea. But it was shown later that phosphate ions, at a concentration as low as 0.003 M, and polyphosphates induced in urea-denatured ribonuclease spectral changes usually associated with refolding (164). It could then be assumed that ribonucleic acid, the actual substrate, was also able to refold the denatured form and prevent inactivation in this way. In other words, even in ribonuclease, the active center is probably not built by adjacent residues in a tail or a ring, but by some residues correctly located in space by the superimposed... 

Ribonucleic acid occurs in all organisms, apparently associated with proteins. The nucleoproteins have been purified by physical methods, but the best preparations are undoubtedly not homogeneous except in the case of certain viruses. The relationship between the two components of even the viruses is still under investigation. On denaturing the protein with physical changes, salts, alcohol, etc., the nucleic acids are liberated. Salts, acid, and organic solvents are used in the purification of protein-free RNA. 

Although the anti-poly G poly C sera react with poly dG poly dC, no precipitation with Micrococcus lysodeikticus DNA (72% GC) is observed, whether native or heat-denatured DNA is used. Negative results are also obtained with native or denatured DNA from E, coli, Clostridium j>erfringens, phage 2 C, chicken myeloblastic leukemic cells or calf thymus. In contrast, antibodies to poly G poly C react with RNA and appear to be capable of distinguishing ribonucleic acids according to their origin. 

In the past, dissociation of the nucleoprotein complex has been brought about by salt solutions or by heat denaturation,129 but, more recently, decomposition has been effected by hydrolysis with trypsin,126 or by the use of dodecyl sodium sulfate130 or strontium nitrate.131 Some virus nucleoproteins are decomposed by ethyl alcohol.132 This effect may be similar to that of alcohol on the ribonucleoproteins of mammalian tissues. If minced liver is denatured with alcohol, and the dried tissue powder is extracted with 10% sodium chloride, the ribonucleoproteins are decomposed to give a soluble sodium ribonucleate while the deoxyribonucleoproteins are unaffected.133 On the other hand, extraction with 10 % sodium chloride is not satisfactory unless the proteins have first been denatured with alcohol. Denaturation also serves to inactivate enzymes of the tissues which might otherwise bring about degradation of the nucleic acid during extraction. 

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