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Conformational states of poly( L ‐tyrosine) in aqueous solution
Author(s) -
Patton Elizabeth,
Auer Henry E.
Publication year - 1975
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.1975.360140413
Subject(s) - chemistry , titration , aqueous solution , intramolecular force , circular dichroism , antiparallel (mathematics) , polymer , titration curve , polyelectrolyte , crystallography , tyrosine , stereochemistry , organic chemistry , biochemistry , physics , quantum mechanics , magnetic field
Abstract Poly( L ‐tyrosine) [( L ‐Tyr) n ] has been characterized in aqueous solution using circular dichroism (CD) and infrared (ir) spectroscopy, and ultracentrifugal analysis. Most of the experiments were carried out at 0.01% polymer or less to avoid the complications caused by precipitation previously encountered by others. This permitted us to study solutions of ( L ‐Tyr) n at lower pH values than had been attained previously. Our results show that a transition to an antiparallel‐β conformation occurs at pH 11.32 upon titration from higher pH. The β structure is intramolecular when first formed and aggregates with time or upon titration below pH 11. Ultracentrifugal analysis of the intramolecular β conformation shows that it is quite compact, with a frictional coefficient ratio, f/f min , of 1.09. In addition to the β structure, a nonordered form of the polymer has been obtained below pH 11 by rapid titration of the ionized polyelectrolyte. This form is nonaggregated and was found to have an f / f min of 1.01, and is therefore almost spherical. The aggregated β form was found to be thermodynamically more stable than the nonordered form at pH 10.7.