Paper Draft 2

Embed Size (px)

DESCRIPTION

scientific paper of amino acids by Dr S Nagaraj

Text of Paper Draft 2

ULTRASONIC VELOCITY STUDIES OF AMINO ACIDS IN AQUEOUS TERTIARY BUTYL ALCOHOL AT 303.15K

ABSTRACT

Ultrasonic velocity and Adiabatic compressibility of Glycine, DL-Alanine, L-Valine and L-Arginine HCL have been measured in Water + Tertiary Butyl Alcohol(TBA) mixtures ranging from pure water to 80% TBA by mass at 303.15K. From the Ultrasonic Velocity, the adiabatic compressibility of the four amino acids in the mixtures has been calculated. From the Ultrasonic Velocity and adiabatic compressibility, apparent molar compressibility, intermolecular free length and change in free energy were calculated. These values were interpreted in terms of structure-breaking or structure making effects of these amino acids in the water + TBA mixtures.

Key words: Apparent molar volume, Density, Viscosity, Amino acids, Tertiary butyl alcohol

1. INTRODUCTIONProteins are the large, complex molecules composed of smaller structural subunits called amino acids. Since proteins are large molecules, the direct study of protein-water interactions is difficult. So it can be studied by the interaction of amino acids in aqueous and mixed aqueous solutions1-4. (REFERENCE FROM PREVIOUS PUBLICATION) The process of hydration plays an important role in the stability, dynamics, structural characteristics and functional activities of the amino acids. The physiochemical and thermodynamic properties in aqueous solution provides the information about solute-solute and solute-solvent interactions. The ultrasonic velocity measurements find wide applications in characterizing the physico-chemical behaviour of liquid mixtures9-11 and in the study of molecular interactions. Ultrasonic velocity of a liquid is related to the binding forces between the atoms or the molecules. Ultrasonic velocities have been adequately employed in understanding the nature of molecular interaction in pure liquids12, binary and ternary mixtures.13-15 The method of studying the molecular interaction from the knowledge of variation of thermodynamic parameter values with composition gives an insight into the molecular process16-18. (REFERENCE FROM THESIS)The attempts made by Ernst and Glinski22 and Kiyohara et al.23,24 indicate that ultrasonic velocities evaluated making use of thermodynamically valid expressions may be utilized to obtain excess Ultrasonic velocities which are useful in understanding the binary liquid mixtures interactions. It is worthwhile to note here that Kudriavtsev25 derived expressions for evaluating theoretically the velocity of sound in pure liquids and liquid mixtures based on thermodynamically valid equations for internal energy in liquids and liquid mixtures and found that the expressions yield velocity data in good agreement with the experimental data for binary mixtures. (REFERENCE FROM THESIS)From the Ultrasonic velocity (); adiabatic compressibility (), apparent molar compressibility (K), intermolecular free length (Lf) and change in free energy (G) were calculated. These parameters were used to discuss the solute-solvent/co solvent and solute-solute interactions.

2. EXPERIMENTALAll the chemicals used are of analytical grade. Commercially obtained chemicals were further purified wherever necessary. In the present investigation, a single crystal variable path interferometer was used to measure the ultrasonic velocities of the solutions. From the knowledge of wavelength (), the ultrasonic velocity () can be calculated by the relationVelocity = Wavelength x Frequency = f (1)Adiabatic compressibility () is an important parameter which throws light on the solute-solvent interactions in solutions. This parameter is widely used to study the behavior of amino acids in solutions. The adiabatic compressibility () is expressed as = 1/ d2 (2) Where is ultrasonic velocity and d is density of the medium

Apparent molar compressibility (k) can be defined as a measure of intermolecular association or dissociation or repulsion. This parameter describes about the interactions between the molecules. The apparent molar compressibility (K) is expressed ask = 1000/Cd0 (d0- d0) + 0M/ d0 (3)Where d, and d0, 0 are the densities and the adiabatic compressibilities of solvent and solution respectively, C is molar concentration of the solute and M is molar mass of the solute.The intermolecular free-length is the distance covered by a sound wave between the surfaces of the neighboring molecules and is given by Jacobson15 asLf = K()1/2 (4)Where K is the temperature dependant constant and is the adiabatic compressibility.

The change in free energy of activation is calculated by G = - KB T ln (h/ KB T) kJmol-1 (5)Where, KB is Boltzmanns constant (1.3806 x 10-23 JK-1), T is temperature, h is Plancks constant (6.626 x 10-34 Js) and is the relaxation time. Table 1: Change in Ultrasonic Velocity, Adiabatic compressibility, Apparent Molar Compressibility, Intermolecular Free length and Change in Free Energy of Amino acids in Water at 303.15K Conc (g mol l-1)Density (d)(g cm-3)Ultrasonic Velocity(ms-1)Adiabatic Compressibility ()(x10-10 m2 N-1)Apparent molar compressibility (-k)(x10-7 m2 N-1)Intermolecular free-length (Lf)(1011m)Change in Free Energy (-G) (kJmol-1)

Glycine + Water

00.99531501.954.45-5.13-

0.0010.99531502.524.453.085.135.05

0.0050.99541504.734.432.965.125.05

0.010.99561507.374.422.865.125.05

0.050.99691527.014.32.845.085.05

0.070.99751536.334.242.765.065.06

0.10.99841549.574.172.645.045.06

DL-Alanine + Water

00.99531504.164.44-5.12-

0.0010.99531504.634.43.275.115.05

0.0050.99541506.524.423.245.15.05

0.010.99561508.784.413.225.095.06

0.050.99671527.564.293.165.085.06

0.070.99731536.934.243.145.065.07

0.10.99811551.214.163.115.055.07

L-Valine + Water

00.99531502.764.44-5.13-

0.0010.99531503.364.443.215.125.05

0.0050.99541505.734.433.185.125.05

0.010.99551508.74.413.165.115.06

0.050.99661532.54.273.095.075.06

0.070.99711544.64.23.055.055.07

0.10.99791562.94.13.035.025.07

L-Arginine HCl + Water

00.99531501.954.47-5.13-

0.0010.99561502.194.452.645.135.05

0.0050.99571504.844.432.645.125.05

0.010.99621507.484.412.585.115.05

0.050.9991530.954.272.575.075.06

0.071.00031542.734.22.555.055.06

0.11.00241560.354.092.535.015.06

Table 2: Change in Ultrasonic Velocity, Adiabatic compressibility, Apparent Molar Compressibility, Intermolecular Free length and Change in Free Energy of Amino acids in 20% TBA at 303.15K Conc Density (d)Ultrasonic VelocityAdiabatic Compressibility ()Apparent molar compressibility (-k)Intermolecular free-length (Lf)Change in Free Energy (-G)

(g mol l-1)(g cm-3)(ms-1)(x10-10 m2 N-1)(x10-7 m2 N-1)(1011m)(kJmol-1)

Glycine in 20% TBA + 80% Water

00.97171606.23.98-5.02

0.0010.97171606.733.982.65.025.07

0.0050.97181608.783.972.515.015.07

0.010.9721611.223.962.425.015.08

0.050.97321627.13.882.064.985.09

0.070.97381633.753.841.944.975.09

0.10.97461645.343.791.84.955.09

DL-Alanine in 20% TBA + 80% Water

00.97171606.213.96-5-

0.0010.97261665.213.992.524.995.07

0.0050.97371665.353.982.464.985.07

0.010.97451606.433.972.334.965.08

0.050.97791620.063.892.274.945.08

0.070.97911627.723.852.154.935.08

0.10.98031640.063.792.024.915.08

L-Valine in 20% TBA + 80% Water

00.97171608.353.97-5.01-

0.0010.97171608.953.972.55.015.07

0.0050.97181611.353.962.495.015.07

0.010.9721614.313.942.4855.08

0.050.97311637.93.832.44.965.09

0.070.97371649.953.772.394.955.09

0.10.97461667.663.682.344.945.09

L-Arginine HCl in 20% TBA + 80% Water

00.97171606.213.98-5.02-

0.0010.97171606.723.982.355.025.08

0.0050.9721608.753.972.325.015.08

0.010.97241611.263.962.295.015.08

0.050.97511631.063.852.214.975.08

0.070.97651640.883.82.184.955.08

0.10.97851655.653.722.154.925.08

Table 3: Change in Ultrasonic Velocity, Adiabatic compressibility, Apparent Molar Compressibility, Intermolecular Free length and Change in Free Energy of Amino acids in 40% TBA at 303.15K Conc Density (d)Ultrasonic VelocityAdiabatic Compressibility ()Apparent molar compressibility (-k)Intermolecular free-length (Lf)Change in Free Energy (-G)

(g mol l-1)(g cm-3)(ms-1)(x10-10 m2 N-1)(x10-7 m2 N-1)(1011m)(kJmol-1)

Glycine in 40% TBA + 60% Water

00.93821674.753.79-5-

0.0010.93831675.273.792.3955.1

0.0050.93841677.233.782.3455.11

0.010.93851679.33.772.164.995.11

0.050.93961693.943.71.754.975.11

0.070.94031699.663.681.644.965.11

0.10.94121707.473.641.494.945.11

DL-Alanine in 40% TBA + 60% Water

00.93821676.253.79-4.95-

0.0010.97171676.653.791.94.945.09

0.0050.93841678.113.781.884.945.1

0.010.93851679.943.771.764.935.1

0.050.93971694.153.71.694.925.1

0.070.94031700.953.671.554.915.1

0.10.94111711.623.621.444.95.1

L-Valine in 40% TBA + 60% Water

00.93821679.163.79-4.99-

0.0010.93831679.653.772.244.995.1

0.0050.93841681.63.762.214.995.11

0.010.938516843.752.194.995.11

0.050.93961703.033.662.114.955.11

0.070.94021712.143.622.084.955.11

0.10.9411725.73.562.054.935.11

L-Arginine HCl in 40% TBA + 60% Water

00.93821674.753.79-5-

0.0010.93831675.163.792.7755.1

0.0050.93861675.813.792.7555.1

0.010.93891676.833.782.7555.1

0.050.94171684.273.742.654.965.1

0.070.9431688.183.722.624.955.1

0.10.94511692.453.692.554.915.1

Table 4: