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Title
Japanese:Ab initio MO and Monte Carlo simulation study on the conformation of L-alanine zwitterion in aqueous solution 
English:Ab initio MO and Monte Carlo simulation study on the conformation of L-alanine zwitterion in aqueous solution 
Author
Japanese: 菊池 修, 渡邊寿雄, 小川 寧, 高瀬 秀人, 高橋 央宜.  
English: Osamu Kikuchi, Toshio Watanabe, Yasushi Ogawa, Hideto Takase, Ohgi Takahashi.  
Language English 
Journal/Book name
Japanese:Journal of Physical Organic Chemistry 
English:Journal of Physical Organic Chemistry 
Volume, Number, Page Volume 10    Number 3    Page 145-151
Published date Mar. 1997 
Publisher
Japanese: 
English:Wiley 
Conference name
Japanese: 
English: 
Conference site
Japanese: 
English: 
Official URL http://dx.doi.org/10.1002/(SICI)1099-1395(199703)10:3%3C145::AID-POC885%3E3.0.CO;2-B
 
DOI https://doi.org/10.1002/(SICI)1099-1395(199703)10:3%3C145::AID-POC885%3E3.0.CO;2-B
Abstract The conformation of the L-alanine zwitterion (ALAZ) in aqueous solution was examined by an ab initio MO method including the solvent effect with the generalized Born (GB) equation. The geometry optimization with the 6-31++G* basis set gave the (, )=(80, 8) conformation as the most stable conformation of ALAZ in aqueous solution, where is the HNCC torsional angle and is the NCCO torsional angle. Stabilization by the solvent is larger in the =90° conformation than in the =0° conformation. However, the differential solvation is small and the conformation with a nearly planar NCCO skeleton is the most stable conformation in aqueous solution. The barrier to rotation of the CO2 group ( rotation) was calculated to be 6·7 (6-31++G*) and 5·9 (MP2/6-31++G*) kcal mol-1, while that to rotation of the NH3 group ( rotation) was very small (<1 kcal mol-1). The relative free energy of solvation and relative stability among the representative conformations of ALAZ were calculated by Monte Carlo (MC) simulation with the statistical perturbation method. The energy variation along the rotation indicated that the value of =5-10° is favorable for ALAZ in aqueous solution. The MC simulation supports the ab initio GB results for the conformational properties of ALAZ in aqueous solution.

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