Effects of hydroxyl groups on binary diffusion coefficients of α-amino acids in dilute aqueous solutions

Abstract

Binary diffusion coefficients, D 12, of α-amino acids with hydroxyl groups, e.g., serine, threonine, allothreonine and homoserine, in dilute aqueous solutions were measured at six different temperatures from 293.2 to 333.2 K by the Taylor dispersion method. The determined D 12 values of serine and threonine at 298.2 K were in good agreement with the published data, whereas no data for allothreonine and homoserine is available in the literature. The D 12 values for each amino acid were well represented with the Stokes–Einstein equation by adjusting the molecular diameter. The D 12 values for amino acids containing hydroxyl groups, except for homoserine, were lower by approximately 5%, on the basis of the same solute molar volume, than those from the corresponding amino acids without hydroxyl groups.