A Study of the Solvation Structure of L-Leucine in Alcohol-Water Binary Solvents through Molecular Dynamics Simulations and FTIR and NMR Spectroscopy.
The solvation structures of l-leucine (Leu) in aliphatic-alcohol-water and fluorinated-alcohol-water solvents are elucidated for various alcohol contents by using molecular dynamics (MD) simulations and IR, and (1) H and (13) C NMR spectroscopy. The aliphatic alcohols included methanol, ethanol, and 2-propanol, whereas the fluorinated alcohols were 2,2,2-trifluoroethanol and 1,1,1,3,3,3-hexafluoro-2-propanol. The MD results show that the hydrophobic alkyl moiety of Leu is surrounded by the alkyl or fluoroalkyl groups of the alcohol molecules. In particular, TFE and HFIP significantly solvate the alkyl group of Leu. IR spectra reveal that the Leu C-H stretching vibration blueshifts in fluorinated alcohol solutions with increasing alcohol content, whereas the vibration redshifts in aliphatic alcohol solutions. When the C-H stretching vibration blueshifts in the fluorinated alcohol solutions, the hydrogen and carbon atoms of the Leu alkyl group are magnetically shielded. Consequently, TFE and HFIP molecules may solvate the Leu alkyl group through the blue-shifting hydrogen bonds.
Department of Chemistry and Applied Chemistry, Graduate School of Science and Engineering, Saga University, Honjo-machi, Saga, 840-8502, Japan. takamut@cc.saga-u.ac.jp.
Toshiyuki
T
Takamuku
Department of Chemistry and Applied Chemistry, Graduate School of Science and Engineering, Saga University, Honjo-machi, Saga, 840-8502, Japan.
Yohei
Y
Hatomoto
Department of Chemistry and Applied Chemistry, Graduate School of Science and Engineering, Saga University, Honjo-machi, Saga, 840-8502, Japan.
Junko
J
Tonegawa
Department of Chemistry and Applied Chemistry, Graduate School of Science and Engineering, Saga University, Honjo-machi, Saga, 840-8502, Japan.
Youichi
Y
Tsutsumi
Department of Chemistry and Applied Chemistry, Graduate School of Science and Engineering, Saga University, Honjo-machi, Saga, 840-8502, Japan.
Tatsuya
T
Umecky
D007930:Leucine / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D056004:Molecular Dynamics Simulation; D012995:Solubility; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods*
D007930:Leucine
alcohols; amino acids; hydrogen bonds; hydrophobic effect; magnetic shielding