EFFECT OF MOLECULAR-STRUCTURE ON COMPLEXATION BETWEEN ACIDIC-POLYPEPTIDES AND BASIC-POLYPEPTIDES IN SOLUTION

Interpolymer complex formation between basic polypeptides, poly(L-prol ine) Form I [PLP(I)I, Form II [PLP(II)I and poly-4-hydroxy-L-proline ( PHLP), and acidic polypeptides, poly(l-glutamic acid) (PLGA), poly(D-g lutamic acid) (PDGA) and poly(L-aspartic acid) (PLAA), has been studie d in water-methanol (1:2 v/v) mixed-solvent by viscometry, potentiomet ry, light scattering and circular dichroism (CD) measurements. It has been found that polymer complexes between basic-and acidic-polypeptide s are formed via hydrogen bonding with a stoichiometric ratio of basic /acidic polypeptides =1:2 (in unit mole ratio) and that PLP(II) forms polymer complex more favorably with PLGA than with PLAA, and the compl ex of PLP(II) with PLGA is also more favorable than the complex format ion of PHLP with PLGA. In addition, the complex formation is highly de pendent on the conformation, especially the optical structure of the c omponent polymers, i.e., the stereoselective complexation is observed. The PLGA having a right-handed helix at pH 3.2 formed the complex fav orably and quickly with left-handed helix PLP(II), whereas PDGA having a left-handed helix at pH 3.2 favorably formed the complex with right -handed helix PLP(I).