Rotation, solvation effects

As found for other stacked base pairs, in the stacked thymine-thymine pair changes in the interaction energy upon rotation of one thymine unit are almost completely compensated for by solvation effects [99JPC(B)884]. The adenine-thymine (A-T) base pair, which possesses a significant degree of conformational... 

The experimental estimate of 37.5 nm for p may be compared with the predictions of the rotational isomeric state model using the result for C of Yathindra and Rao mentioned above, for which p lies in the range 13 to 22 nm. The difference is small enough to be attributed to error in experimental light scattering, the effects of residual intermolecular association, the effects of molecular weight dispersity, or solvation effects, which are neglected in the theoretical estimate of p. 

These 46 publications include studies of the structure and bonding of molecules, thermochemistry, ioniation potentials and electron affinities, vibrational spectroscopy, internal rotation, hydrogen bonding in both small molecules and in biomolecules, intermolecular interactions, reactive intermediates, polymers and solvation effects. 

The ORD curves in a mixture of w-cresol and 25 vol. % of chloroform were found to fit the simple Drude equation. These results indicate that the discontinuity of specific rotation of polymer in mixed solvents is a consequence of the solvatation effect and is independent of polymer conformation. The characterization of e-methyl nylon is difficult due to its extremely low solubility in most organic solvents. 

Figure 9.10 Schematic relationship between the radius Rq of an unsolvated sphere and the effective radius R of a solvated sphere or of a spherical volume excluded by an ellipsoidal particle rotating through all directions.

As for the theoretical treatment, we could only try to include the eleetrostatie solute-solvent interaetions and, in faet, we corrected the electronic potential energies for the solvation effeets by simply adding as calculated according to the solvaton model [eq. (2)]. The resulting potential curves are to be seen as effective potentials at equilibrium, i.e. refleeting orientational equilibrium distributions of the solvent dipoles around the eharged atoms of the solute molecule. In principle, the use of potentials thus corrected involves the assumption that solvent equilibration is more rapid than internal rotation of the solute molecule. Fig. 4 points out the effects produced on the potential... 

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