Thoeretical analysis of conformational transitions in model compounds of natural teichoic acids

Abstract

Conformational transitions of poly(propylenephosphate)(PPP) from soluble forms through gels of loosely coiled structure, of limited solubility, to hypercoiled forms of compact structure, insoluble in water, have been explained by theoretical considerations. The studies were carried out using the CNDO/2 method for model molecule of PPP, such as dimethylphosphoric acid and 1,3-bis(methylphosphono-oxy)propane, for which the value of the association energy was calculated. The theoretical results unaminously show that phosphate groups present in PPP macromolecules are responsible for the conformational properties of the polymer. The hypercoiled form of this polyelectrolyte is stabilized by association interactions (ΔE_a= 79 kcal mol^–1). The interaction of the hydrophobic parts of the chain additionally stabilizes the compact structure of PPP (ΔE≈ 4 kcal mol^–1).