Relaxation dynamics of l-alanine in water medium investigated by dielectric relaxation spectroscopy (original) (raw)
Related papers
Dielectric Study of Aqueous Solutions of Alanine and Phenylalanine
Journal- Chinese Chemical Society Taipei
Dielectric relaxation measurements on aqueous solutions of alanine and phenylalanine were carried out using time domain reflectometry (TDR) at 25, 30, 35, and 40 °C in the frequency range from 10 MHz to 20 GHz. Aqueous solutions of alanine and phenylalanine are prepared for five different molar concentrations of the respective amino acid. For all the solutions considered, only one relaxation peak was observed in this frequency range. The relaxation peaks shift to lower frequency with an increase in alanine and phenylalanine molar concentration. The molar enthalpy of activation and molar entropy of activation show endothermic interactions.
Journal of Molecular Liquids, 2019
A study on the dielectric properties of various molar concentration levels of aqueous L-glutamine, ethanol mixtures at microwave frequency region (0.02 b ν/GHz b 20) is carried out in the temperature range of 298 K to 323 K. Dielectric parameters such as dielectric permittivity, dielectric loss of different molar concentrations of L-glutamine in water, ethanol medium are evaluated. It is noticed that the real and imaginary part of dielectric permittivity increases with increase in molar concentration levels of L-glutamine in water and ethanol medium and decreases with increase in temperature. From these parameters, average relaxation time (τ), excessive inverse relaxation time (1/τ) E , excessive dielectric permittivity (ε E) are determined and their behavior is analyzed in terms of the distribution of hydrogen bond network in the liquid medium. The theoretical dipole moments of Lglutamine in both aqueous and ethanol medium are determined by using DFT-B3LYP method with different solvation models. Mean molecular polarizability (α M) of the system is calculated from the Lippincott δ function potential model and compared with the Lefevre method. The activation entropy (ΔS*), activation enthalpy (ΔH*), Helmholtz energy (ΔF E) parameters have also been evaluated and the results are correlated.
A study on the dielectric properties of glycine in aqueous solution medium in the microwave frequency region (130 MHz-20 GHz) is carried out using the open-ended coaxial probe technique. Dielectric parameters such as dielectric constant, dielectric loss of various weight percentage levels of glycine in double distilled aqueous medium such as water are determined. It is observed that the real part of dielectric permittivity decreases and imaginary part of the dielectric permittivity increases with increase in the weight percentage level of glycine in water. From these parameters we calculated the relaxation time and its behaviour is analysed. Dipole moment value is calculated from the optimized geometrical structure of the glycine molecule from the AM 1 , PM 3 , and MNDO ab initio quantum mechanical calculations using the Argus Lab chemical modeling Software 2004.
Present work reports the dielectric response for non-steroidal anti-inflammatory drugs (NSAID) 2-[2-[2-[(2,6-dichlorophenyl)amino]phenyl]acetyl] oxyacetic acid (Aceclofenac) in the aqueous leucine solution at different concentrations and temperatures (298.15 K-283.15 K) using time domain reflectometry technique in the frequency region 1 GHz to 30 GHz. Dielectric parameters such as complex permittivity (ε*), dielectric constant (ε), dielectric relaxation time (τ), dipole moment (µ) and Kirkwood correlation factor (g) have been calculated and the study is corroborated by the thermodynamic parameters such as molar enthalpy of activation (∆H), entropy of activation (∆S) and free energy of activation (∆F) to give insight into the structural dynamics.
Dielectric Relaxation of Biological Water †
The Journal of Physical Chemistry B, 1997
Dielectric relaxation and NMR spectrum of water in biological systems such as proteins, DNA, and reverse micelles can often be described by two widely different time constants, one of which is in the picosecond while the other is in the nanosecond regime. Although it is widely believed that the bimodal relaxation arises from water at the hydration shell, a quantitative understanding of this important phenomenon is lacking. In this article we present a theory of dielectric relaxation of biological water. The time dependent relaxation of biological water is described in terms of a dynamic equilibrium between the free and bound water molecules. It is assumed that only the free water molecules undergo orientational motion; the bound water contribution enters only through the rotation of the biomolecule, which is also considered. The dielectric relaxation is then determined by the equilibrium constant between the two species and the rate of conversion from bound to free state and vice versa. However, the dielectric relaxation in such complex biomolecular systems depends on several parameters such as the rotational time constant of the protein molecule, the dimension of the hydration shell, the strength of the hydrogen bond, the static dielectric constant of the water bound to the biomolecule, etc. The present theory includes all these aspects in a consistent way. The results are shown to be in very good agreement with all the known results. The present study can be helpful in understanding the solvation of biomolecules such as proteins.
Relaxation dynamics of a protein solution investigated by dielectric spectroscopy
Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics, 2012
In the present work, we provide a dielectric study on two differently concentrated aqueous lysozyme solutions in the frequency range from 1 MHz to 40 GHz and for temperatures from 275 to 330 K. We analyze the three dispersion regions, commonly found in protein solutions, usually termed β-, γ-, and δ-relaxation. The β-relaxation, occurring in the frequency range around 10 MHz and the γ-relaxation around 20 GHz (at room temperature) can be attributed to the rotation of the polar protein molecules in their aqueous medium and the reorientational motion of the free water molecules, respectively. The nature of the δ-relaxation, which often is ascribed to the motion of bound water molecules, is not yet fully understood. Here we provide data on the temperature dependence of the relaxation times and relaxation strengths of all three detected processes and on the dc conductivity arising from ionic charge transport. The temperature dependences of the β-and γ-relaxations are closely correlated. We found a significant temperature dependence of the dipole moment of the protein, indicating conformational changes. Moreover we find a breakdown of the Debye-Stokes-Einstein relation in this protein solution, i.e., the dc conductivity is not completely governed by the mobility of the solvent molecules. Instead it seems that the dc conductivity is closely connected to the hydration shell dynamics.
2022
Dielectric relaxation measurements of amino acid (L-alanine) in water solution were carried out using time domain reflectometry at 25C to -5C in the frequency range between 10 MHz to 30 GHz. The dielectric parameters i.e. static dielectric constant and relaxation time, were obtained from the complex permittivity spectra using a nonlinear least square fit method. From the values of the relaxation time, the thermodynamic parameters are determined. The Kirkwood correlation factor was calculated from the static permittivity. The dielectric relaxation parameters increase with an increase in concentration (mM) of amino acid (L-alanine) due to the structure of hydrogen bond groups by the amino acid (L-alanine) molecules in the aqueous solution. The relaxation peak shifted to lower frequency with an increase in molar concentration of amino acid.
Microwave Dielectric Relaxation of Alcohols in non polar solutions
IOSR Journal of Applied Physics, 2014
The properties of the binary mixtures of 1-propanol and phenol have been studied at constant temperature 303K in dilute solutions of benzene using standard standing wave microwave X-band (9.4 GHz) Jband (7.4 GHz) technique. The values of different dielectric parameters ε 0 , ε', ε'', ε ∞ have been determined for five different mole fractions of 1-propanol and phenol. The values of permittivity and dielectric loss are used to evaluate relaxation time for overall molecular rotation (τ 1), relaxation time for intermolecular rotations (τ 2), most probable relaxation time (τ 0) and dipole moment (µ) at constant temperature 303K. The values of relaxation times and dipole moment are found to increases with the mole fraction of 1-propanol, phenol in all binary mixtures. The energy parameter (ΔFτ) for dielectric relaxation process of the mixtures is also calculated. It is found that the dielectric relaxation process can be treated as a rate process. The present investigation suggest that existence of both the intermolecular and intramolecular orientation takes place in both binary mixtures.