HYDRATION OF ALPHA-MALTOSE AND AMYLOSE - MOLECULAR MODELING AND THERMODYNAMICS STUDY

Hydration of alpha-maltose and amylose were investigated using molecular modelling and thermodynamics methods. The structure and energy of hydration of three low-energy conformers of alpha-maltose were determined by the MM3 molecular mechanics method. The hydration structure was found to be sensitive to the conformation of alpha-maltose and hydration numbers 10 or 11 were estimated for the different conformers. Differential scanning calorimetry and thermogravimetric analysis were used to determine the number of water molecules specifically bonded (non-freezing water) to amylose and different samples of alpha-maltose. Due to high crystallinity of alpha-maltose samples, the observed non-freezing water content was lower than predicted by molecular modelling. In contrast, the experimental number of non-freezing molecules of water per D-glucopyranose residue for amorphous amylose (n(h) = 3.8) is in good accordance with the value of 3.8 extracted from our calculations.