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Potentiometric titration of poly‐ S ‐carboxymethyl‐ L ‐cysteine in aqueous NaCl solution
Author(s) -
Makino Shio,
Sugai Shintaro
Publication year - 1970
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.1970.360090908
Subject(s) - chemistry , titration , random coil , aqueous solution , titration curve , potentiometric titration , polymer , intramolecular force , hydrogen bond , intermolecular force , analytical chemistry (journal) , inorganic chemistry , crystallography , chromatography , molecule , stereochemistry , organic chemistry , circular dichroism , electrode
pH titration measurements of poly‐ S ‐carboxymethyl‐ L ‐cysteine were undertaken in the aqueous Nacl solution in relation to the β form–random coil transition. The titration curves show a marked molecular weight dependence because of the shortened chain length of materials. Comparison of the optical rotatory dispersion parameter a 0 with the titration curve reveals that the titration curve apparently reflects a β structure–random coil transition. The β form of this polymer is assumed to be an intramolecular β form, rather than a β structure stabilized by an intermolecular hydrogen bond, at least in the polymer concentration range considered here. The standard free energy change per amino acid residue for the transition from un‐ionized random coil to un‐ionized β form is estimated to be about −750 cal/mole residue in the range of 0.005–0.2 M NaCl concentration.