CHAPTER INTRODUCTION

Transcription

1 48 CHAPTER 3 PARTIAL MOLAL VOLUME, PARTIAL MOLAL COMPRESSIBILITY AND VISCOSITY B-COEFFICIENT OF FOUR HOMOLOGOUS -AMINO ACIDS IN AQUEOUS SODIUM FLUORIDE SOLUTIONS AT DIFFERENT TEMPERATURES 3.1 INTRODUCTION Proteins are the most vital of all the biological molecules evolved for a variety of specific purposes. To be functional and active, a very specific three dimensional structure is required. An array of vital forces, i.e., hydrophobic interactions, hydrogen bonding, ionic interactions, van der Waals interactions constitute the main forces responsible for the specific structure and conformation of proteins. Some covalent forces like disulphide linkage also contribute in maintaining the structure of protein (Privalov Hydration of proteins plays a significant role in the stability, dynamic, structural characteristics and fundamental activities of biopolymers. Proteins are complex molecules and their behaviour in solutions is governed by number of specific interactions. To reduce the degree of complexity in the study of these interactions, the study of the interactions in systems containing smaller bio-molecules, such as amino acids and peptides are preferred by many authors (Riyazuddeen and Bansal 2006, Yan et al 1998.

2 49 The zwitterionic nature of amino acids has an important bearing on biological functions in the physiological media such as blood, membranes, cellular fluids etc., where water happens to be important (Zubay The properties of proteins such as their structure, solubility, denaturation, activity of enzymes, etc. are greatly influenced by electrolytes (Von Hippel and Schleich 1969 a,b, Jencks 1969, Makhatadze and Privalov 1992, Robinson and Jencks The apparent and partial molal volumes of electrolyte solutions have proven to be a very useful tool in elucidating the structural interactions occurring in solutions (Millero The partial molal volumes, which are the first derivative of Gibbs energy with respect to pressure, are also used to calculate the effect of pressure on ionic equlibria for processes of engineering and oceanographic importance (Millero Since amino acids are zwitterions in aqueous solutions, their hydrations and interactions with proteins have resemblance with those of electrolytes (Zhao 2006, Millero et al The compressibility property, which is the second derivative of the Gibbs energy, also is a sensitive indicator of molecular interactions, particularly in cases where partial molal volume data fail to provide an unequivocal interpretation of the interactions (Iqbal and Verrall Viscosity has also been proven to be a sensitive and accurate probe for solution studies (Wang et al Study of interactions of some amino acids with KCl/KNO 3 at T= ( to K and that of L-alanine with potassium di-hydrogen citrate and tri-potassium citrate at T = ( to K have been reported by Riyazuddeen and Altamash (2010, Sadeghi and Goodarizi (2008 respectively. Wang et al (1999 have reported the partial molar volumes of some -amino acids in aqueous sodium acetate solutions at K. Apparent molar volumes and viscosity B-coefficients of caffeine in aqueous thorium nitrate solutions at T = (298.15, , and K are

3 50 determined by Sinha et al (2010. The viscosity B-coefficients of some amino acids have been investigated in aqueous potassium thiocyanate (Wadi and Goyal 1992, sodium butyrate (Yan et al 2001 and ammonium chloride (Natarajan et al 1990 solutions. Effect of temperature on volumetric and viscometric properties of some amino acids in aqueous metformine hydrochloride (Rajagopal and Jayabalakrishnan 2010c and salbutamol sulphate (Rajagopal and Jayabalakrishnan 2009 have also been reported. The effectiveness of fluoride as anion in stabilising proteins is greater than chloride, bromide and iodide. Similarly, sodium cation is having the order of stabilising proteins as Na + > Li + > Ca 2+ > Mg 2+ (Wiggins Sodium fluoride is colourless crystalline salt used in the treatment of tooth decay (Bourne Literature survey shows that the influence of sodium fluoride on the volumetric properties of glycylglycine alone has been reported by Lin et al (2006. In this chapter the data on density, ultrasonic speed and viscosity of some amino acids (glycine, L-alanine, L-valine and L-leucine in aqueous sodium fluoride at T= (303.15, , and K are reported. Apparent molal volumes (V, partial molal volumes (V 0, Hepler coefficient ( 2 V 0 / T 2, transfer volumes ( V 0 and hydration number (n H are evaluated using density data. Apparent molal compressibility (K, partial molal compressibility (K 0, transfer compressibility ( K 0 and hydration number (n H have been calculated using ultrasonic speed data. Viscosity B-coefficients of Jones-Dole equation, transfer B-coefficient ( B, variation of B with temperature (db/dt, free energy of activation per mole of solvent µ 0* 1 and solute ( µ 0* 2 are estimated from viscosity data. Pair and triplet interaction coefficients have also been calculated from transfer parameters. The linear correlation of V 0, V 0, K 0, K 0, and B for the homologous

4 51 series of amino acids have been used to calculate the contribution of charged end groups (NH 3 +, COO -, methylene group (CH 2 and other alkyl chain of the amino acids. 3.2 EXPERIMENTAL The densities ( of the solutions of sodium fluoride are measured using a single stem pycnometer. The ultrasonic speed (u are determined using a multifrequency ultrasonic interferometer (M-84, Mittal make, India at a frequency of 2 MHz. Viscosity ( are measured by means of a suspended level Ubbelohde viscometer. Densities, ultrasonic speeds and viscosities are measured at temperatures T = (303.15, , and K as discussed in detail in Chapter RESULTS The experimental densities of the homologous amino acids in aqueous sodium fluoride solutions at temperatures T = (303.15, , and K are given in Table 3.1. The uncertainty values for density are calculated and are included in Table 3.1. Throughout this chapter m denotes molality of amino acids and m S molality of sodium fluoride. The apparent molal volumes (V are calculated from the measured densities using the equation (1.1 and the error values associated with them are evaluated using equation (1.2 and are given in Table 3.1.

5 Table 3.1 Density, and apparent molal volume, V of amino acids in aqueous sodium fluoride solutions at different temperatures m S = 0 mol kg -1 m S = 0.1 mol kg -1 m S = 0.3 mol kg -1 m S = 0.5 mol kg -1 m (mol kg -1 *10 3 V *10 6 *10 3 V *10 6 *10 3 V *10 6 *10 3 V *10 6 (kg m -3 (m 3 mol -1 (kg m -3 (m 3 mol -1 (kg m -3 (m 3 mol -1 (kg m -3 (m 3 mol -1 T = K Glycine ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( (0.04 = = = = Alanine ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( (0.04 = = = = Valine ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( (0.04 = = = =

6 Table 3.1 (Continued m S = 0 mol kg -1 m S = 0.1 mol kg -1 m S = 0.3 mol kg -1 m S = 0.5 mol kg -1 m (mol kg -1 *10 3 (kg m -3 V *10 6 (m 3 mol -1 *10 (kg m -3 V *10 6 (m 3 mol -1 *10 (kg m -3 V *10 6 (m 3 mol -1 *10 (kg m -3 V *10 6 (m 3 mol -1 = = = = Leucine ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( (0.04 = = = = T = K Glycine ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( (0.03 = = = = Alanine ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( (0.03 = = = =

7 Table 3.1 (Continued m S = 0 mol kg -1 m S = 0.1 mol kg -1 m S = 0.3 mol kg -1 m S = 0.5 mol kg -1 m (mol kg -1 *10 3 (kg m -3 V *10 6 (m 3 mol -1 *10 (kg m -3 V *10 6 (m 3 mol -1 *10 (kg m -3 V *10 6 (m 3 mol -1 *10 (kg m -3 V *10 6 (m 3 mol -1 Valine ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( (0.04 = = = = Leucine ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( (0.04 = = = = T = K Glycine ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( (0.03 = = = =

8 Table 3.1 (Continued m S = 0 mol kg -1 m S = 0.1 mol kg -1 m S = 0.3 mol kg -1 m S = 0.5 mol kg -1 m (mol kg -1 *10 3 (kg m -3 V *10 6 (m 3 mol -1 *10 (kg m -3 V *10 6 (m 3 mol -1 *10 (kg m -3 V *10 6 (m 3 mol -1 *10 (kg m -3 V *10 6 (m 3 mol -1 Alanine ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( (0.03 = = = = Valine ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( (0.04 = = = = Leucine ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( (0.04 = = = =

9 Table 3.1 (Continued m S = 0 mol kg -1 m S = 0.1 mol kg -1 m S = 0.3 mol kg -1 m S = 0.5 mol kg -1 m (mol kg -1 *10 3 (kg m -3 V *10 6 (m 3 mol -1 *10 (kg m -3 V *10 6 (m 3 mol -1 *10 (kg m -3 V *10 6 (m 3 mol -1 *10 (kg m -3 V *10 6 (m 3 mol -1 T = K Glycine ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( (0.03 = = = = Alanine ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( (0.03 = = = = Valine ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( (0.04 = = = =

10 Table 3.1 (Continued m S = 0 mol kg -1 m S = 0.1 mol kg -1 m S = 0.3 mol kg -1 m S = 0.5 mol kg -1 m (mol kg -1 *10 3 (kg m -3 V *10 6 (m 3 mol -1 *10 (kg m -3 V *10 6 (m 3 mol -1 *10 (kg m -3 V *10 6 (m 3 mol -1 *10 (kg m -3 V *10 6 (m 3 mol -1 Leucine ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( (0.04 = = = = Values within parenthesis indicates the error inv 57

11 58 Usually the partial molal volumes (V 0 are obtained using the equation (1.3 by the method of least squares. However in the cases where molality dependence of V is found to be either negligible or having no definite trend, the partial molal volumes at infinite dilution, V 0 are evaluated by taking an average of all the data points ( Bhat and Ahluwalia 1985, Wang et al 1999, Yan et al In the present case, the values of V 0 are evaluated by taking an average of all the data points. The values of partial molal volumes V 0, along with the literature values of partial molal volumes of amino acids in water, are given in Table Table 3.2 Partial molal volume ( V of amino acids in aqueous sodium fluoride solutions at different temperatures Amino Acid 0 V * 10 6 / m 3 mol -1 at various m s / mol kg (Water Present Work Literature T = K Glycine ( a b c ( ( (0.32 Alanine ( a c ( ( (0.21 Valine ( c ( ( (0.59 Leucine ( ( ( (0.23 T = K Glycine 43.98( d e 44.37( ( (0.53 Alanine 60.41( d e 61.77( ( (0.25 Valine 90.30( f g 92.64( ( (0.68 Leucine ( i ( ( (0.50 T = K Glycine 44.26( c j 44.85( ( (0.73 Alanine 61.43( f 62.9 b 62.82( ( (0.45 Valine 91.23( f 93.39( ( (0.46 Leucine ( k ( ( (0.48 T = K Glycine 44.79( l 45.59( ( (1.09 Alanine 61.55( g 63.75( ( (0.50 Valine 91.87( l 94.09( ( (0.49 Leucine ( g ( ( (0.50 Values within parenthesis indicates the error in a Yan et al (2004, b Bhattacharya and Sengupta (1985, c Lark and Bala (1983, d Munde and Kishore (2003, e Lark et al (2004, f Gopal and Agarwal (1973, g Kikuchi et al (1995, i Yan et al (1999, j Zhao et al (2004, k Duke et al (1994, l Banipal and Kapoor ( V

12 59 The contribution of the zwitterionic end group V 0 (NH + 3, COO -, the methylene group V 0 (CH 2 and other alkyl chains of homologous series of amino acids to V 0 at different temperatures are evaluated using equations (1.4 to (1.7 and are reported in Table 3.3. Table 3.3 Contributions of zwitterionic groups (NH + 3, COO -, CH 2 and 0 other alkyl side chains to partial molal volumes ( V of amino acids in aqueous sodium fluoride solutions at different temperatures Group 0 V * 10 6 / m 3 mol -1 at various m s / mol kg (Water T = K NH + 3, COO CH CH 3 CH (CH 3 2 CHCH (CH 3 2 CH CH 2 CH T = K NH + 3, COO CH CH 3 CH (CH 3 2 CHCH (CH 3 2 CH CH 2 CH T = K NH + 3, COO CH CH 3 CH (CH 3 2 CHCH (CH 3 2 CH CH 2 CH T = K NH + 3, COO CH CH 3 CH (CH 3 2 CHCH (CH 3 2 CH CH 2 CH

13 60 The partial molal volumes of transfer V 0 of amino acids from pure water to sodium fluoride water mixtures are calculated using equation (1.8 and the results are given in Table 3.4. Table 3.4 Partial molal volume of transfer ( V 0 of amino acids in aqueous sodium fluoride solutions at different temperatures Amino Acid 0 V * 10 6 / m 3 mol -1 at various m s / mol kg T = K Glycine Alanine Valine Leucine T = K Glycine Alanine Valine Leucine T = K Glycine Alanine Valine Leucine T = K Glycine Alanine Valine Leucine The zwitterionic end group contribution V 0 (NH + 3, COO -, the methylene group contribution V 0 (CH 2 and the contribution from other alkyl chains of homologous series of amino acids to V 0 are evaluated using equations (1.4 to (1.7 and are given in Table 3.5

14 61 Table 3.5 Contributions of zwitterionic groups (NH 3 +, COO -, CH 2 and other alkyl side chains to partial molal volumes of transfer ( V 0 of amino acids in aqueous sodium fluoride solutions at different temperatures Group V 0 * 10 6 / m 3 mol -1 at various m s / mol kg T = K NH + 3, COO CH CH 3 CH (CH 3 2 CHCH (CH 3 2 CH CH 2 CH T = K NH + 3, COO CH CH 3 CH (CH 3 2 CHCH (CH 3 2 CH CH 2 CH T = K NH + 3, COO CH CH 3 CH (CH 3 2 CHCH (CH 3 2 CH CH 2 CH T = K NH + 3, COO CH CH 3 CH (CH 3 2 CHCH (CH 3 2 CH CH 2 CH The standard partial molal volumes of amino acids are used to determine the number of water molecules, n H, hydrated to the amino acid by using equations (1.9 to (1.13 and are given in Table 3.6. The hydration number n H values evaluated from the compressibility data using the standard equation (1.18 are also presented in Table 3.6.

15 62 Table 3.6 Hydration number (n H of amino acids in aqueous sodium fluoride solutions at different temperatures Amino Acid From volume data n H at various m s / mol kg From compressibility data From volume data T = K From compressibility data From volume data From compressibility data Glycine Alanine Valine Leucine T = K Glycine Alanine Valine Leucine T = K Glycine Alanine Valine Leucine T = K Glycine Alanine Valine Leucine On the basis of McMillan-Mayer theory (McMillan and Mayer 1945 of solutions, Friedman and Krishnan (1973 b considered that the thermodynamic transfer properties of solutes in aqueous solutions could be explained in terms of the cosolutes interaction. The pair and triplet volume interaction parameters are obtained by fitting transfer data to equation (1.14.

16 63 The pair and triplet compressibility interaction coefficients V AB / K AB / AB and V ABB / K ABB / ABB are given in Table 3.7. Table 3.7 Pair interaction coefficients, V AB / K AB / AB and Triplet interaction coefficients V ABB / K ABB / ABB of amino acids in aqueous sodium fluoride solutions at different temperatures Amino Acid V AB * 10 6 m 3 mol -2 kg V ABB * 10 6 K AB * K ABB * AB * 10 3 m 3 mol -3 kg 2 m 3 mol -1 kg Pa -1 m 3 mol -1 kg Pa -1 m 3 mol -2 kg ABB * 10 3 m 3 mol -3 kg 2 T = K Glycine Alanine Valine Leucine T = K Glycine Alanine Valine Leucine T = K Glycine Alanine Valine Leucine T = K Glycine Alanine Valine Leucine The variation of limiting partial molal volume V 0 with temperature is expressed using the quadratic equation (1.15 (Pal and Kumar The

17 64 coefficients a, b and c are determined and these coefficients are used to interpret the effect of the hydrocarbon chain on water structure using the general hydrophobicity criteria proposed by Hepler (1969. The values of a, b and c are given in Table 3.8. Table 3.8 Temperature coefficients, a, b and c of amino acids in aqueous sodium fluoride solutions Amino Acid a coefficient b coefficient c -1 m 3 mol -1 K m s = 0.1 / mol kg -1 coefficient -2 m 6 mol -2 K Glycine Alanine Valine Leucine m s = 0.3 / mol kg -1 Glycine Alanine Valine Leucine m s = 0.5 / mol kg -1 Glycine Alanine Valine Leucine The ultrasonic speed values of the homologous amino acids in aqueous sodium fluoride solutions at temperatures T = (303.15, , and K are given in Table 3.9. The uncertainty values u for ultrasonic speed are calculated and are included in Table 3.9.

18 65 Table 3.9 Ultrasonic speed (u of Amino acids in Aqueous Sodium Fluoride solutions at different temperatures m u / m s -1 at various m s / mol kg -1 (mol kg (Water T = K Glycine uncertainty u = u = u = u = Alanine uncertainty u = u = u = u = Valine uncertainty u = u = u = u = Leucine uncertainty u = u = u = u = 1.381

19 66 Table 3.9 (Continued m u / m s -1 at various m s / mol kg -1 (mol kg (Water T = K Glycine uncertainty u = u = u = u = Alanine uncertainty u = u = u = u = Valine uncertainty u = u = u = u = Leucine uncertainty u = u = u = u = 1.366

20 67 Table 3.9 (Continued m u / m s -1 at various m s / mol kg -1 (mol kg (Water T = K Glycine uncertainty u = u = u = u = Alanine uncertainty u = u = u = u = Valine uncertainty u = u = u = u = Leucine uncertainty u = u = u = u = 1.397

21 68 Table 3.9 (Continued m u / m s -1 at various m s / mol kg -1 (mol kg (Water T = K Glycine uncertainty u = u = u = u = Alanine uncertainty u = u = u = u = Valine uncertainty u = u = u = u = Leucine uncertainty u = u = u = u = 1.458

22 69 The apparent molal compressibilities (K of the homologous amino acids in aqueous sodium fluoride solutions at temperatures T = (303.15, , and K are calculated using the equation (1.16 and are listed in Table Table 3.10 Apparent molal compressibility (K of amino acids in aqueous sodium fluoride solutions at different temperatures m K * / m 3 mol -1 Pa -1 at various m s / mol kg -1 (mol kg (Water T = K Glycine Alanine Valine Leucine

23 70 Table 3.10 (Continued m K * / m 3 mol -1 Pa -1 at various m s / mol kg -1 (mol kg (Water T = K Glycine Alanine Valine Leucine

24 71 Table 3.10 (Continued m K * / m 3 mol -1 Pa -1 at various m s / mol kg -1 (mol kg (Water T = K Glycine Alanine Valine Leucine

25 72 Table 3.10 (Continued m K * / m 3 mol -1 Pa -1 at various m s / mol kg -1 (mol kg (Water T = K Glycine Alanine Valine Leucine

26 73 The partial molal compressibility (K 0 of the homologous amino acids has been evaluated using equation (1.17 by least square fit method (Figure 3.1. The calculated values of K 0 (along with error and the experimental slope values S k are given in Table The literature values of partial molal compressibility of amino acids in water are also given in Table 3.11 for comparison K / (10-15 m 3.mol -1.Pa m/(mol.kg -1 Figure 3.1 Plot of apparent molal compressibility (K against molality (m of ( glycine, ( alanine, ( valine, ( leucine at T = K of 0.1 M sodium fluoride solution

27 Table 3.11 Partial molal compressibility (K 0, slopes (S k of Amino acids in aqueous sodium fluoride solutions at different temperatures Amino acids K 0 * S k * K 0 * S k * K 0 * S k * K 0 * S k * m 3 mol -1 Pa -1 kg m 3 mol -2 Pa -1 m 3 mol -1 Pa -1 kg m 3 mol -2 Pa -1 m 3 mol -1 Pa -1 kg m 3 mol -2 Pa -1 m 3 mol -1 Pa -1 kg m 3 mol -2 Pa -1 at various m s / mol kg (Water T = K Glycine ( ( ( ( Alanine ( ( ( ( Valine ( ( ( ( Leucine ( ( ( ( T = K Glycine ( m ( ( ( Alanine ( ( ( ( Valine ( ( ( ( Leucine ( ( ( (

28 Table 3.11 (Continued Amino acids K 0 * S k * K 0 * S k * K 0 * S k * K 0 * S k * m 3 mol -1 Pa -1 kg m 3 mol -2 Pa -1 m 3 mol -1 Pa -1 kg m 3 mol -2 Pa -1 m 3 mol -1 Pa -1 kg m 3 mol -2 Pa -1 m 3 mol -1 Pa -1 kg m 3 mol -2 Pa -1 at various m s / mol kg (Water T = K Glycine ( n ( ( ( Alanine ( n ( ( ( Valine ( n ( ( ( Leucine ( n ( ( ( T = K Glycine ( g ( ( ( Alanine ( g ( ( ( Valine ( g ( ( ( Leucine ( g ( ( ( Values within parenthesis indicates the error in K 0 m Wadi and Ramasami (1997, n Kharakoz (1991, g Kikuchi et al (

29 76 The contributions of charged end groups K 0 (NH 3 +, COO -, K 0 (CH 2 group and other alkyl chain of the amino acids to K 0 have been estimated using equations (1.4 to (1.7 and are given in Table Table 3.12 Group contributions of partial molal compressibility (K 0 of amino acids in aqueous sodium fluoride solutions at different temperatures K 0 * / m 3 mol -1 Pa -1 at various m s / mol kg -1 Group 0.00 (Water T = K NH + 3, COO CH CH 3 CH (CH 3 2 CHCH (CH 3 2 CH CH 2 CH T = K NH + 3, COO CH CH 3 CH (CH 3 2 CHCH (CH 3 2 CH CH 2 CH T = K NH + 3, COO CH CH 3 CH (CH 3 2 CHCH (CH 3 2 CH CH 2 CH T = K NH + 3, COO CH CH 3 CH (CH 3 2 CHCH (CH 3 2 CH CH 2 CH

30 77 The transfer partial molal compressibilities K 0 of amino acids from pure water to sodium fluoride water mixtures are calculated using equation (1.8 and the values are given in Table Table 3.13 Transfer partial molal compressibility ( K 0 of Amino acids in aqueous sodium fluoride solutions at different temperatures K 0 * / m 3 mol -1 Pa -1 at various m s / mol kg -1 Amino Acid T = K Glycine Alanine Valine Leucine T = K Glycine Alanine Valine Leucine T = K Glycine Alanine Valine Leucine T = K Glycine Alanine Valine Leucine The contributions of K 0 (NH + 3, COO -, K 0 (CH 2 and other alkyl chain of the homologous amino acids to transfer partial molal compressibilities K 0 are evaluated using equations (1.4 to (1.7 and are listed in Table 3.14.

31 78 Table 3.14 Group Contributions of Transfer Partial molal compressibility ( K 0 of Amino acids in Aqueous Sodium Fluoride solutions at different temperatures K 0 * / m 3 mol -1 Pa -1 at various m s / mol kg -1 Group T = K NH + 3, COO CH CH 3 CH (CH 3 2 CHCH (CH 3 2 CH CH 2 CH T = K NH + 3, COO CH CH 3 CH (CH 3 2 CHCH (CH 3 2 CH CH 2 CH T = K NH + 3, COO CH CH 3 CH (CH 3 2 CHCH (CH 3 2 CH CH 2 CH T = K NH + 3, COO CH CH 3 CH (CH 3 2 CHCH (CH 3 2 CH CH 2 CH The viscosity data of the homologous amino acids in aqueous sodium fluoride solutions at temperatures T = (303.15, , and K are given in Table The uncertainty values for viscosity are calculated and are also given in Table 3.15.

32 79 Table 3.15 Viscosity ( of Amino acids in Aqueous Sodium Fluoride solutions at different temperatures m / m Pa s at various m s / mol kg -1 (mol kg (Water T = K Glycine uncertainty = = = = Alanine uncertainty = = = = Valine uncertainty = = = = Leucine uncertainty = = = =

33 80 Table 3.15 (Continued m / m Pa s at various m s / mol kg -1 (mol kg (Water T = K Glycine uncertainty = = = = Alanine uncertainty = = = = Valine uncertainty = = = = Leucine uncertainty = = = =

34 81 Table 3.15 (Continued m / m Pa s at various m s / mol kg -1 (mol kg (Water T = K Glycine uncertainty = = = = Alanine uncertainty = = = = Valine uncertainty = = = = Leucine uncertainty = = = =

35 82 Table 3.15 (Continued m / m Pa s at various m s / mol kg -1 (mol kg (Water T = K Glycine uncertainty = = = = Alanine uncertainty = = = = Valine uncertainty = = = = Leucine uncertainty = = = =

36 83 The viscosity B coefficients of amino acids in aqueous sodium fluoride solutions are obtained using equation (1.23 and are given in Table The values of viscosity B coefficients of amino acids in water, available in literature are also given in Tables 3.16 for comparison. Table 3.16 Viscosity B - coefficient of amino acids in aqueous sodium fluoride solutions at different temperatures Amino Acid B * 10 3 / m 3 mol -1 at various m s / mol kg (Water Present Work Literature T = K Glycine ( ( ( (0.008 Alanine ( o ( ( (0.011 Valine ( ( ( (0.020 Leucine 0.497( ( ( (0.030 Glycine (0.010 T = K i p ( ( (0.007 Alanine ( p ( ( (0.007 Valine ( i ( ( (0.013 Leucine ( i ( ( (0.025 Glycine (0.012 T = K q r ( ( (0.007 Alanine ( s ( ( (0.013 Valine ( t ( ( (0.013 Leucine ( t ( ( (0.019 T = K Glycine ( t ( ( (0.015 Alanine ( s ( ( (0.007 Valine ( t ( ( (0.007 Leucine ( t ( ( (0.009 Values within parenthesis indicates the standard error in viscosity B coefficient o Zhao (2006, i Yan et al (1999, p Sandhu and Kashyap (1987, q Islam and Wadi (2004, r Bhattacharya and Sengupta (1988, s Bhattacharya and Sengupta (1980, t Rajagopal and Jayabalakrishnan (2010c

37 84 The zwitterionic end group, the methylene group and other alkyl side chain group contributions of amino acids to viscosity B coefficient have been calculated using equations (1.4 to (1.7. The evaluated values are given in Table Table 3.17 Contribution to the viscosity B coefficient from zwitterionic groups, CH 2 and other alkyl side chains of amino acids in aqueous sodium fluoride solution at different temperatures Group B * 10 3 / m 3 mol -1 at various m s / mol kg T = K NH + 3, COO CH CH 3 CH (CH 3 2 CHCH (CH 3 2 CH CH 2 CH T = K NH + 3, COO CH CH 3 CH (CH 3 2 CHCH (CH 3 2 CH CH 2 CH T = K NH + 3, COO CH CH 3 CH (CH 3 2 CHCH (CH 3 2 CH CH 2 CH T = K NH + 3, COO CH CH 3 CH (CH 3 2 CHCH (CH 3 2 CH CH 2 CH

38 85 It is of interest to examine the transfer B-coefficient B from the B- coefficient data using the equation (1.8 and transfer B coefficient of R group B(R. The results are given in Table Table 3.18 Viscosity B - Coefficient transfer ( B and transfer B coefficients of R group, B(R of Amino acids in Aqueous Sodium Fluoride solutions at different temperatures Amino acids B*10 3 B(R*10 3 B *10 3 B(R *10 3 B *10 3 B(R *10 3 m 3 mol -1 m 3 mol -1 m 3 mol -1 m 3 mol -1 m 3 mol -1 m 3 mol -1 at various m s / mol kg T = K Glycine Alanine Valine Leucine T = K Glycine Alanine Valine Leucine T = K Glycine Alanine Valine Leucine T = K Glycine Alanine Valine Leucine The temperature derivatives of B coefficient (db/dt have also been calculated and are reported in Table 3.19.

39 86 Table 3.19 Temperature coefficient (db/dt of Amino acids in aqueous sodium fluoride solutions at different temperatures Amino (db/dt / m 3 mol -1 K -1 at various m s / mol kg -1 acids 0.00 (Water Glycine Alanine Valine Leucine The solvation of any solute can be judged from the magnitude of B / V 0 (Zhao The values of B /V 0 are given in Table Table 3.20 Ratio of B - coefficient to partial molal volume (B / V 0 of amino acids in aqueous sodium fluoride solutions at different temperatures Amino B / V 0 at various m s / mol kg -1 acids 0.00 (Water T = K Glycine Alanine Valine Leucine T = K Glycine Alanine Valine Leucine T = K Glycine Alanine Valine Leucine T = K Glycine Alanine Valine Leucine

40 87 Free energy of activation of viscous flow is another useful parameter to assess the complexity of liquid structure. The viscosity data are used to estimate the free energy of activation per mole of the solvent ( µ 1 0* and solute ( µ 2 0* as suggested by Feakins et al (1993 and Eyring et al (1941 from equations (1.26 and (1.27. The values of ( µ 1 0* and the partial molal volume of solvent ( V are given in Table The values of the free energy 0 1 of activation per mole of the solute ( µ 2 0* are given in Table Table 3.21 Free energy of activation of solvent 0* 1 and mean volume of solvent ( V of Aqueous Sodium Fluoride solution at 0 1 different temperatures m s mol kg -1 0* 1 0 V 1 m 3 mol -1 kj mol -1 T = K T = K ; 8.93 u ; u T = K T = K u Lark et al (2006