CHARACTERIZATION OF LACTATE-GUANIDINIUM AND LACTATE-LACTATE INTERACTIONS IN AQUEOUS-SOLUTION BY SPECTROPOLARIMETRY

Spectropolarimetry has been used to quantify the lactate-guanidinium a nd lactate-lactate equilibrium interactions in aqueous solution. Assoc iation constants for the lactate-guanidinium and lactate-lactate forma tions are 6.11 dm(3) mol(-1) and 1.12 dm(3) mol(-1), respectively, in aqueous solution; 6.11 dm(3) mol(-1) is a high value for an electrosta tic interaction in water. This stability, however, cannot account for the extremely strong lactate-protein binding, observed earlier by NMR spectroscopy. The molar rotation coefficients for both the heteroassoc iation and homoassociation complexes are also calculated. The homoasso ciative lactate-lactate binding is the first such interaction, whose c onstant has been determined by spectropolarimetry in aqueous solution.