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Physico-chemical study of low polymer ribonucleic acids in solution
97R
Abstracts
showed that not less t h a n half the nueleotides of S- RN A are involved in helical regions. I t has been shown t h a t increase in ionic strength augments the stability of the hydrogen bonds. The part played by the a m o u n t of G - - C pairs in the stability of the secondary structures has been discussed. The properties of S-RNA investigated are very close to those, of R N A as macromolecules. PHYSICO-CHEMICAL STUDY OF LOW POLYMER RIBONUCLEIC ACIDS IN SOLUTION
L. L. Kiselev, E. P. l~ehbinder and L. Yu. Frolova, Vysokomol. soedin. 4: No. 5, 7 5 5 - 7 6 1 , 1962. THE change in shape of yeast S-I~NA molecules has been investigated with respect to the electrolyte content, p H and temperature of the solution. F o r this purpose measurements were made o f ' t h e reduced and intrinsic viscosities and of the specific optical rotation and the optical density of S - R N A solutions. I t has been shown that molecules of low polymer ribonucleic acids m a y exist in solution in two clearly different conformations: a globular (compact) conformation and an unfolded (loose, uncoiled) conformation. The fomer is characterized by a minimal effective hydrodynamic volume and high content of hydrogen bonds. I t exists in neutral solution of ionic strength 0.1 at 25 °. This compact conformation is the more ordered one, possessing a considerable a m o u n t of helical structures. The loose conformation is characterized by a large hydrodynamic v()lume and by the absence of ordered (helical) regions. I t exists at Z ~ 10-3, p I - I ~ 3 and elevated temperatures. The transition from the compact to the loose conformation bears the character of a "random-coil]" transition. The macromolecular structure o f S - R N A sharply differs from t h a t of D N A and displays great similarity to the maeromolecular structure of high polymer R N A in solution. FLOW BIREFRINGENCE IN SOLUTIONS OF DEOXIRIBONUCLEIC ACIDS D N A - - I . THE OPTICAL ANISOTROPY OF NATIVE AND AGGREGATED D E N A T U R A T E D D N A
E. V. Frisman, V. I. Vorobev, L. V. Shchagina and N. K. Yanovskaya, Vysokomol. soedin. 4: No. 5, 762-768, 1962. THE optical anisotl"opy of native and aggregated D N A has been determined from flow birefringence and viscosity measurements. The difference in polarizability of the m o n o m er unit has revealed considerable rigidity n o t only in native but also in aggregated denaturated D N A molecules. An estimate of the degree of coiling in native D N A has shown it. to be of low value. *ANIONIC POLYMERIZATION OF FORMALDEHYDE--II.
J. Mejzlik, J. Mencikova and Z. Machacek, Vysokomol. soedin. 4: No. 5, 769-775, 1962. A STUDY of the polymerization of formaldehyde in diethyl ether solution has shown that the molecular weight of the resultant polymer is independent of the degree of conversion up to 50~o conversion. This is regarded as p r o o f of the chain mechanism of the reaction, Using three catalysts (dibutylamine, tributylamine, t e t r a b u t y l a m m o n i u m laurate) of relative activities 1:3.5:4, the molecular weight of the polymer formed has been found to ~be independent of both the type and concentration of the catalyst. A reaction order of about two with respect to the m o n o m e r has been found for the reaction catalysed by dibutylamine and t e t r a b u t y l a m m o n i u m laurate. I t has been found that the molecular weight of the polymer is directly proportional to the m o n o m e r concentration and inversely proportional to the concentration of impurities.
Abstracts
showed that not less t h a n half the nueleotides of S- RN A are involved in helical regions. I t has been shown t h a t increase in ionic strength augments the stability of the hydrogen bonds. The part played by the a m o u n t of G - - C pairs in the stability of the secondary structures has been discussed. The properties of S-RNA investigated are very close to those, of R N A as macromolecules. PHYSICO-CHEMICAL STUDY OF LOW POLYMER RIBONUCLEIC ACIDS IN SOLUTION
L. L. Kiselev, E. P. l~ehbinder and L. Yu. Frolova, Vysokomol. soedin. 4: No. 5, 7 5 5 - 7 6 1 , 1962. THE change in shape of yeast S-I~NA molecules has been investigated with respect to the electrolyte content, p H and temperature of the solution. F o r this purpose measurements were made o f ' t h e reduced and intrinsic viscosities and of the specific optical rotation and the optical density of S - R N A solutions. I t has been shown that molecules of low polymer ribonucleic acids m a y exist in solution in two clearly different conformations: a globular (compact) conformation and an unfolded (loose, uncoiled) conformation. The fomer is characterized by a minimal effective hydrodynamic volume and high content of hydrogen bonds. I t exists in neutral solution of ionic strength 0.1 at 25 °. This compact conformation is the more ordered one, possessing a considerable a m o u n t of helical structures. The loose conformation is characterized by a large hydrodynamic v()lume and by the absence of ordered (helical) regions. I t exists at Z ~ 10-3, p I - I ~ 3 and elevated temperatures. The transition from the compact to the loose conformation bears the character of a "random-coil]" transition. The macromolecular structure o f S - R N A sharply differs from t h a t of D N A and displays great similarity to the maeromolecular structure of high polymer R N A in solution. FLOW BIREFRINGENCE IN SOLUTIONS OF DEOXIRIBONUCLEIC ACIDS D N A - - I . THE OPTICAL ANISOTROPY OF NATIVE AND AGGREGATED D E N A T U R A T E D D N A
E. V. Frisman, V. I. Vorobev, L. V. Shchagina and N. K. Yanovskaya, Vysokomol. soedin. 4: No. 5, 762-768, 1962. THE optical anisotl"opy of native and aggregated D N A has been determined from flow birefringence and viscosity measurements. The difference in polarizability of the m o n o m er unit has revealed considerable rigidity n o t only in native but also in aggregated denaturated D N A molecules. An estimate of the degree of coiling in native D N A has shown it. to be of low value. *ANIONIC POLYMERIZATION OF FORMALDEHYDE--II.
J. Mejzlik, J. Mencikova and Z. Machacek, Vysokomol. soedin. 4: No. 5, 769-775, 1962. A STUDY of the polymerization of formaldehyde in diethyl ether solution has shown that the molecular weight of the resultant polymer is independent of the degree of conversion up to 50~o conversion. This is regarded as p r o o f of the chain mechanism of the reaction, Using three catalysts (dibutylamine, tributylamine, t e t r a b u t y l a m m o n i u m laurate) of relative activities 1:3.5:4, the molecular weight of the polymer formed has been found to ~be independent of both the type and concentration of the catalyst. A reaction order of about two with respect to the m o n o m e r has been found for the reaction catalysed by dibutylamine and t e t r a b u t y l a m m o n i u m laurate. I t has been found that the molecular weight of the polymer is directly proportional to the m o n o m e r concentration and inversely proportional to the concentration of impurities.