Solvent-free crystallizations of amino acids: the effects of the hydrophilicity/hydrophobicity of side-chains.
This work studied the self-assembling (crystallizing) behaviour of amino acids in the absence of solvent and additives (by sublimation and deposition in vacuum), instead of from aqueous solution. It is found that the hydrophilicity/hydrophobicity of side-chains can significantly affect the crystallization of amino acids in the absence of solvent. Crystal structures of amino acids having hydrophobic side-chains (L-valine, L-leucine, L-isoleucine and l-methionine) obtained from sublimation are the same with those obtained from aqueous solution. New polymorphs for six amino acids are thought to have been obtained, based on X-ray diffraction and IR data for three of them (L-tyrosine, L-Phyenylalanine and L-tryptophan), and just IR data for the other three (L-alanine, L-proline and L-threonine).
Liu
Zhimin
Z
State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, P.O. Box 110, Dalian 116023, China.
Li
Can
C
D000597:Amino Acids, Branched-Chain / Q000737:chemistry*; D003460:Crystallization; D057927:Hydrophobic and Hydrophilic Interactions; D012997:Solvents; D017550:Spectroscopy, Fourier Transform Infrared; D014618:Vacuum; D014867:Water / Q000737:chemistry*; D014961:X-Ray Diffraction
D000597:Amino Acids, Branched-Chain; D012997:Solvents; D014867:Water