Hydration behavior of asparagine: an approach using time domain reflectometry at low temperatures

• Published in: Journal of biomolecular structure & dynamics 2024-12, p.1-14
• Main Authors: Karale, Ravikant R, Kamble, Savita, Alwaleedy, Suad, Kabara, Komal B, Narwade, Pallavi, Al-Hamdani, Saeed Mohammed, Kumbharkhane, Ashok C, Sarode, Arvind V
• Format: Article
• Language: English
• ISSN: 0739-1102; 1538-0254; 1538-0254
• DOI: 10.1080/07391102.2024.2445153

The dielectric behavior of Asparagine (C H N O ) in water over the frequency range of 10 MHz to 30 GHz in the temperature region of 278.15-303.15 K in a step of 5 K has been carried out using time domain reflectometry (TDR) at various concentrations of asparagine. The obtained dielectric spectra reveal two relaxation peaks. The low frequency relaxation is attributed to the interaction between solute-solute molecules, while the high frequency relaxation is due to the reorientation of solvent molecules. The various dielectric and thermodynamic parameters were calculated such as the dielectric constant (ε ), relaxation time (τ ), effective dipole moment (μ ), Kirkwood correlation factor (g ), hydration number or the number of solvent molecules effectively bounded to solute molecule (Z ), effective volume of rotation (V ), free energy of activation (ΔF ), entropy of activation (ΔS ) and enthalpy of activation (ΔH ). The static dielectric constant (ε ) shows increasing trend towards the higher concentration of asparagine, where as the high frequency dielectric constant (ε ) decreases with the concentration of asparagine. The relaxation time of low frequency (τ ) and high frequency (τ ) processes increases towards higher concentration of solute molecule and also towards lower temperature. As the concentration of asparagine increases, the value of effective dipole moment (μ ) decreases. With increasing amino acid concentrations hydration dynamics get affected and indicated by decreasing the hydration number (Z ) but the hydration dynamics of aqueous asparagine was found least temperature dependent.