Intermacromolecular complex formation between biopolymers through hydrogen bonding

Abstract

Complex formation of basic polypeptides, poly(L-proline) From I [PLP (I)], Form II [PLP(II)], and PHLP with acidic polypeptides, poly (L-glutamic acid) (PLGA), poly(D-glutamic acid) (PDGA), and poly (L-aspartic acid) (PLAA) through hydrogen bonding in a hydroalcoholic media has been studied with viscometer, light scatter, pH meter, and CD. The result exhibited that all complex occurred as the composition of basic/acidic polypeptide=1:2, yielding the maximum value at $\Delta$I and maximum (or minimum) at reduced viscosity in the 1:2 composition irrespective of the complex systems used. A more favorable complex formed in the PLP(II)-PLGA complex than PHLP-PLGA due to the existence of more flexible helical conformation in PLP(II) than PHLP. The complexation is highly dependent on the conformation of the basic polypeptides as well as the acidic polypetides, i.e., the stereoselective complexation is observed. The PLGA having a right-handed helix at PH 3.2 formed the complex favorably and quickly with left-handed helix PLP(II), whereas PDGA havig a left-handed helix at PH 3.2 favorably formed the complex with right-handed helix PLP(I). The effect of side The result showed that more favorable condition for the complexation was PLGA-PLP(II) system which has longer side chain length at acidic polypeptide than PLAA-PLP(II) which has shorter side chain length. The above all facts were well supported by the result of CD for the binary and ternary systems by comparing the ideal spectra which are acquired by the addition of each pure polypeptide``s spectrum with real experimental spectra for the complex. by the CD spectra for the complexes we could predict the conformational change of each acidic and basic polypeptide in the complexes.