From amino acids to dipeptide: The changes in thermal stability and hydration properties of β-alanine, L-histidine and L-carnosine

The changes in hydration structure of β-alanine and L-histidine through dipeptide formation were studied and discussed from experimentally measured values of densities, viscosities and computational investigations of amino acids diluted aqueous solutions, β-alanine and L-histidine, and the final dipeptide, L-carnosine over the temperature range from 283.15 K to 313.15 K. The apparent molar volume (Vϕ), apparent molar volume at infinite dilution (Vϕo), Masson's experimental slope (Sv), limiting apparent molar expansibility, (Eϕo), Hepler's coefficient, hydration number, and viscosity B coefficient have been evaluated using the experimental density and viscosity values. The formation of the peptide bond has been examined in terms of water structuring nature around dipeptide and starting amino acids, and how it is linked with dipeptide self-interactions. Also, L-carnosine solubility in water was determined, as well as the thermal decomposition of the investigated compounds was examined by simultaneous thermogravimetric (TG) and DSC measurement. For the evaluation of their decomposition, the data obtained by coupled TG–mass spectrometric (MS) measurements were used.