Jun 19, 2001 - 19 Shilo H, Ogawa T & Yoshihashi H, J Alii chem Soc. 77 ... 2 1 Frank H S & Evan M W, J chem Phys, 13 (1945) 507. 22 Chalikian T V.
Indian Journal of Chemistry Vol. 41A, February 2002, pr. 312-315
Apparent molar volume and apparent molar compressibility of glycine in aqueous vanadyl su lphate solutions at 298 .15,303.15 and 308.l5 K P G Rohankar & A S Aswar* Department of Chemistry, Amravati University, Amravati 444 602. Indi a
Received 19 Jun e 2001; revised 16 October 2001 Appare nt molar volume and apparent molar compressibil ity of glyc ine in aqueo us vanady l sulphate sol ution s (0. 10, 0.05 and 0.01 M ) have been determin ed from 298.15 K to 308 . 15 K. The transfer of vo lumes for the transfer of g lycine from water to aqueou s vanadyl sulph ate have been evaluated. Negative tran sfer of vo lume has been o bse rved for 0.1 M and 0.05 M vanadyl sulph ate solutions. The results are explained o n the basis of electrostricti on.
Hydration of proteins plays a signi ficant role in the stability , dynamics, structural characteristics and functional activity of biopolymers. During the last two decades considerable study has been carried out to investi gate hydration of proteins through volumetric ' and ultrasonic measurements, since these properties are sensitive to the degree and nature of hydration 1-7 . Due to the complex nature of proteins, direct study is somewhat difficult. Therefore, the useful approach is to study simpler model compounds such as am ino acids. Most of the studies on aminoacids8- lo and biomolecules 11.1 2 have been carried out in pure and mixed aqueous solutions. But such investi gations in the presence of metal ions, which play an important rol e in vitai functions of living organi sm, are still scanty. Vanadium plays an important role in plant growth , lipid metabolism and regulation of cholesterol synthesis. Therefore, it was thought that it would be of interest to study glycine in 0.10, O.OS and 0.01 M vanadyl sulphate solutions at 298. 1S K, 303. 1S K and 308.1S±0.1 K through vol umetric and ultrasonic methods. Experimental Vanadyl sulphate pentahydrate and glycine used were of AR grade and dri ed over P20 5 in desiccator before use. All solutions were prepared afresh by weight in doub ly distilled water, degassed by boiling,
having conductance less than 0.6xlO-6 Scm- I. The density measurements were performed with a precalibrated bicapillary pyknometer. The highest attainable precision 13 of the density measurement carried out with capillary pyknometer is Sx 10- 3 kgm- 3 . However, our density measurements were precise much better than Sx lO- 2 kgm- 3 . Ultrasonic velocity was measured with a variable path ultrasonic interferometer at 2 MH z. The repeatability of velocity measurment was ±0.1 ms- lover the temperature range studied. The temperature was maintained at ±0.1 K by means of a thermostat. Results and discussion The densities and ultrasonic velocities of glycine in 0. 1, O.OS and 0.01 M aqueous vanadyl sulphate solutions at 298.1S K, 303.1S K and 308. 1S K ±O.l K as a function of molality are listed in Table 1. The concentration dependences of the speed of so und and density were tri ed to fit into following equations:
y = ay + by m
... (1) ... (2)
where y = u or d au = u* or d* , u* is the speed of sound in solvent and d * is the densi ty of the solven t and m is the molality of the solution . Equation 2 yields better fit th an Eq. I. The coefficients of Eq . 2 together wi th the correlation coefficients, r, are given in Table 2. The velocity data shows only a slight deviation from linearity. The apparent molar volume was calculated from Eq. (3)
