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Gas phase structural stability of neutral and zwitterionic forms of alanine in presence of (H2O)(n=1-7) clusters: A density functional theory study

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Title Gas phase structural stability of neutral and zwitterionic forms of alanine in presence of (H2O)(n=1-7) clusters: A density functional theory study
 
Creator OJHA, AK
VYAS, N
DUBEY, SP
 
Subject Water clusters
Zwitterionic and neutral forms of alanine
DFT
RAMAN OPTICAL-ACTIVITY
VIBRATIONAL-SPECTRA
CONFORMATIONAL-ANALYSIS
HYDRATED CLUSTERS
ELECTRON-DENSITY
AQUEOUS-SOLUTION
WATER-MOLECULES
PROTON-TRANSFER
ALPHA-GLYCINE
AMINO-ACIDS
 
Description In the present contribution we have examined the gas phase structural stability of zwitterionic alanine (ZAla) relative to the stability of neutral alanine (Ala) in presence of water clusters of size n = 1-7 using Density Functional Theory (DFT) calculations. The gas phase structural energy, and thermodynamical parameters of Ala-(H2O)(n=1-7) and ZAla-(H2O)(n=2-7) complexes are calculated at B3LYP/6-311++G(d,p) level of theory. We do not get stable structure of ZAla and ZAla + (H2O) in gas phase. This implies that the hydrogen bonding with one water molecule does not produce stable structure of ZAla. However, we found the existence of stable structure of ZAla-(H2O)(2) complex in gas phase. This essentially means that at least two water molecules are required to produce stable structure of ZAla in gas phase. Further, we also observed that the Ala-(H2O)(2) is relatively more stable than that of ZAla-(H2O)(2). The optimized energy of Ala-(H2O)(3) and ZAla-(H2O)(3) complexes is found to be almost same and thus these two complexes are said to be isoenergetic. The ZAla-(H2O)(n) complex is found to be structurally as well as thermodynamically more stable than that of Ala-(H2O)(n) for n >= 4. It indicates that the possibility of finding the ZAla-(H2O)(n) complex is larger than that of Ala-(H2O)(n) for n >= 4 in gas phase. The above observations are also well supported by the thermodynamical parameters such as: Gibbs energy, enthalpy and entropy of the complexes. (C) 2012 Elsevier B.V. All rights reserved.
 
Publisher ELSEVIER SCIENCE BV
 
Date 2014-10-15T14:01:45Z
2014-10-15T14:01:45Z
2012
 
Type Article
 
Identifier COMPUTATIONAL AND THEORETICAL CHEMISTRY, 100216-23
http://dx.doi.org/10.1016/j.comptc.2012.09.010
http://dspace.library.iitb.ac.in/jspui/handle/100/15051
 
Language en