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Intensity fluctuation spectroscopy and transfer RNA conformation. III. Influence of NaCl concentration on the size and shape of the initially salt‐free tRNA in solution
Author(s) -
Patkowski A.,
Chu B.
Publication year - 1979
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.1979.360180816
Subject(s) - chemistry , transfer rna , intermolecular force , salt (chemistry) , laser linewidth , molecule , dynamic light scattering , ion , spectroscopy , chemical physics , crystallography , analytical chemistry (journal) , rna , chromatography , organic chemistry , biochemistry , laser , physics , materials science , quantum mechanics , nanoparticle , optics , gene , nanotechnology
The influence of sodium ion concentration in solution on the initially salt‐free conformation of bulk tRNA from baker's yeast has been investigated by means of photon correlation spectroscopy. From the measured values of translational ( D T ) and rotational ( D R ) diffusion coefficients, the semiaxes of an ellipsoid of revolution, which are hydrodynamically equivalent to the tRNA molecule, were calculated for tRNA solutions in pure H 2 O as well as in 0.005, 0.1, 0.5 M NaCl and 0.01 M MgCl 2 solutions at pH 4.2 and 7.5. These data, combined with our previous studies, suggested a model which describes the formation of an ordered tRNA structure due to increasing NaCl concentrations. Furthermore, we have obtained information concerning intermolecular interactions between tRNA molecules in solution. In low‐salt or salt‐free tRNA solutions, we detected in the linewidth distribution function an extra‐fast component which can be attributed as possibly due to charge fluctuations related to the reaction of ionization of organic bases. In our light‐scattering linewidth measurements, we do not see fluctuations of charged and uncharged states directly as concentration fluctuations. Rather, we postulate a modulation of long‐range intermolecular electrostatic interactions between the tRNA molecules due to such charge fluctuations. It is this modulation which is related to the fast component of the time correlation function at finite concentrations. A quantitative theory is needed to provide a more definitive explanation of the dynamical behavior of tRNA in salt‐free or low‐salt solutions.