RESUMEN

Physical, chemical and microbiological stability of the materials is affected by the rotational and translational mobility of free and hydrated water. The role of water in areas such as protein hydration and enzyme activity, food technology, lyophilization and polymers hydration is, therefore, important and can be well understood in terms of dielectric relaxation spectroscopy. Concentration and temperature-dependent hydrophobicity of amino acid is reflected in their tendencies to appear in appropriate positions in proteins. Therefore, to gain more insights on the temperature and concentration dependence of hydrophobicity and structural properties of amino acid, dielectric relaxation of aqueous alanine have been studied in the temperature region 303.15 K to 278.15 K. Time domain spectroscopy have been used in the frequency range of 10 MHz to 30 GHz and in the concentration range 0.18708 ≤ c/M ≤ 0.74831. Two relaxation processes namely the low-frequency relaxation (l) and the high-frequency relaxation (h) has been detected for the aqueous alanine. Dielectric parameters such as static dielectric constant (εj), relaxation time (τj) dipole moments (û) and correlation factor (g) have been studied to investigate molecular interaction between alanine and water. The number of water molecules irrotationally bond by the solute molecules (Zib) was also determined to examine the hydrophobicity of alanine which was found more hydrophobic towards low temperatures and concentrations. Thermodynamic parameters calculated are also supported well for the hydrophobic behaviour of alanine towards low temperatures and concentrations.Communicated by Ramaswamy H. Sarma.

Asunto(s)

Alanina , Aminoácidos , Temperatura , Alanina/química , Espectroscopía Dieléctrica , Interacciones Hidrofóbicas e Hidrofílicas , Agua/química

RESUMEN

A new relation, ΔE = aebq, between the chemical shift ΔE and effective charge 'q' is proposed. It has been shown that the relation generates polynomial relations, between ΔE and 'q' used by earlier investigators and addresses their short-comings effectively. Further, four possible sign combinations of 'q' and ΔE are accounted for using the proposed equation. Units of arbitrary constants 'a' and 'b' are derived. The tendency of 'q' to attain saturation value is also explained. The success of the new relation has been tested using its linearized form ln ∣ ΔE ∣ = ln ∣ a ∣ + bq for a large number of compounds, by taking their experimental X-ray absorption edge shifts along with corresponding values of 'q' from the available literature. In the process, the claim of earlier workers regarding linear relationship between ΔE and 'q' and ΔE and 'qX', where 'X' is the electronegativity, has been found incorrect in the case of 6p6 isoelectronic series of compounds.