Murthy, T V S Aruna

Murthy, V R

Reddy, R N V Ranga

Subbaiah, D V

English

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M ia n  J. Phys. 65B (6), 635-539 (1991)Molecular polarizabilities and diamagnetic susceptibilities of L-alanyl-L-alanineR N V Ranga Reddy, D V Subbaiah, V R Murthy and T V S  Aruna MurthyDepartment of Physics, Sri Krishnadevaraya University,Anantapur-515 003, IndiaA b stract: The mean polarizability (<^) of L-alanyl-L-alanine (L-A-L-A) is evaluated by Molecular vibration method of Rao and Murthy (1979) and Lippincott-3-function potential modal (Rao and Murthy 1972 Curr. Sci. 4116). From the estimated polarizability the diamagnetic susceptibility of L-alanyl- L-alanine (L-A-L-A) is calculated by using Rao and Murthy's method. The diamagnetic susceptibility of the oligomer is evaiuated by Pascal's method also. The additivity of polarizability and susceptibility in oligomers is established.Keyw ords: Molecular polarizability, diamagnetic susceptibility, L-alanyl- L-alanine, bio-polymers.P A C S N o :  87.15.MiI . IntroductionBio-polymers play a vital role in understanding the basic principles of cell structure, metabolism and other physiological phenomena. A  study of their properties is very useful in understanding the molecular configurations and the nature of hydrogen bondings in the molecule. The conformation of such bio-polymers is usually studied by physical techniques like X-ray diffraction, NMR, ORD, CD, IR and Resonance Raman spectroscopy. Recently attempts are made by Rao and Murthy to utilise the molecular polarizability in conformation of bio-polymers, though its application to simple molecules has been done extensively by LeFevre School. In this direction (Rao et al 1977) and Murthy et al (1977, 1979, 1980) have studied the molecular polarizabilities of a few bio-polymers and liquid crystals and applied successfully molecular polarizability in the conformational analysis of bio-polymers (Murthy 1979). The molecular polarizability is found to be useful in evaluating London dispersion forces also.In the present investigation the mean polarizability of L-alanyl-L-alanine is reported by using (i)  Molecular vibration method and (ii) Lipplncott-8-functiot) method. The diamagnetic susceptibility of L -A -L -A  is also estimated from the knowledge of polarizability data and compared with the one obtained from Pascal's method (Pascal 1910, Pacault 1948).535OSS' R  N  V  R an ga  Reddy  et al 3 .  Results and discussionof ( b u - b r ) ,  (b t + 2 b r )  (as calculated from eqs. 1 and 2 ) b^ and t in Table 1. The values of S < m , S2<^ and obtains*Table 1. Bond polarizabilities of L*A-L-A (xIO** cm*).Bond ‘>T0.089 0.192 0.123 0.034N ^ -C a 0.008 0.487 0.168 0.160C t - H 0.070 0.199 0.113 0.043C . - C 0.017 0.614 0.216 0.199C - 0 0.013 0.260 0.095 0.082C H , C j 0.006 0.622 0.211 0.205C - H 0.071 0.198 0.113 0.042C - -N 0.010 0.449 0.156 0.146N -H 0.076 0.192 0.114 0.038N - C o 0.009 0.620 0.180 0.170C - 0 0.014 0.242 0.090 0.076Lippincott method are presented in Table 2. The mean polarizability of L -A -L -A  obtained from the two methods are presented in Table 3. The values ofTable 2. Molecular polarizability ( x 1 0 " c m ‘ )  of L -A -L -A  from Lippincott method.2.464 0.168 1.606 1.413diamagnetic susceptibility of L*A-L-A  obtained from Rao and Murthy's method and Pascal's method is presented in Table 4.Table 3. Comparison of the mean molecular polarizability (  X 10**|Cm') of L -A -L -A .Molecular vibra­tion method1.398Lippincottmethod1.413From Table 3, it is found that there is a very good agreement between the values of obtained from molecular vibration method and Lippincott method.Molecular polarizabilities and diamagnetic susceptibilities etc 539From Table 4, It is found that the diamagnetic susceptibility of L -A -L -A  obtained from Rao and Murthy s method and Pascars method are agreeing very well.Table 4. Diamagnetic susceptibility ( x IO "  CGS emu/mol) of L-A-L-A.75.48 76.208 79.116"Estimated from Rao and Murthy's method by using ^jif of molecular vibration method.^Estimated from Rao and Murthy's method by using of Lippincott method.^Estimated from Pascal's method.ReferencesGupta M K and Gupta V D 1978 Indian J. Blochem. Biophys. 15 413 Murthy V R 1970 Ph,D, Thesis ($ V University, Tirupati, India)-----1979 Indian  J. Biochem, Biophys. 16 32Murthy V R, Subbaiah D V and Naidu S  V 1977 Ind .J. Chem. 1 ---- 1979 Indian J. Biochem. Biophys. 16 43Murthy V R, Naidu S  V and Ranga Reddy R N V 1980 Mol. Cryst. Liq. Cryst. 59 27Pacault A  1948 Rev. Sci. 86 38Pascal P 1910 Ann. Chem. Phys. 19 5Rao B P and Murthy V R 1972 Curr. Sci. 41 15Rao B P, Murthy V R and Subbaiah D V 1976 Indian J. Pure and Appl. Phys. 14 276-----1977 Indian J. Biochem. Biophys. 14 181Rao B P and Murthy V R 1979 Indian J. Chem. 13 17Selwood P W  1960 Techniques of Organic Chemistry (New York: Wiley-Intersclence) Voll. Part IV p 28

Molecular Polarizabilities and Diamagnetic Susceptibilities of L-Anyl-L-Alanine

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Molecular Polarizabilities and Diamagnetic Susceptibilities of L-Anyl-L-Alanine

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