Premium
Electric dichroism of poly(riboadenylic acid)
Author(s) -
Charney Elliot,
Milstien Julie B.
Publication year - 1978
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.1978.360170703
Subject(s) - chemistry , electric field , stacking , polymer , asymmetry , dichroism , valence (chemistry) , ionic bonding , polyelectrolyte , ionic strength , ion , anisotropy , chemical physics , linear dichroism , crystallography , charge density , polarization (electrochemistry) , molecular physics , circular dichroism , optics , physics , organic chemistry , quantum mechanics , aqueous solution
Electric dichroism measurements on poly(A) in low‐ionic‐strength solution demonstrate that below a molecular weight of 130,000 the double‐stranded polymer is hydrodynamically rigid and above that molecular weight becomes increasingly flexible. At 500,000 it is considerably more flexible than DNA of the same molecular weight, with a mean end‐to‐end distance of about 1150 Å compared to approximately 1600 Å for DNA. The fully extended length for both DNA and poly(A) of this molecular weight is about 2750 Å. It is further shown that the orientation of these polyelectrolytes in an electric field is consistent with theoretical treatments of the counter‐ion distribution and a preliminary model based on the additivity of classical valence charge anisotropy and counter‐ion polarization is postulated for the orientation mechanism. Single‐stranded pol (A) is shown not only to retain its base stacking in the presence of the electric field but to extend the persistent regions of stacked bases so that it attains a rodlike structure very similar to the one in the double‐stranded polymer is found to be less than that expected from consideration of the x‐ray structure. An explanation for this result is sought in the electric asymmetry of the helical polymer.