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→Louis Pasteur
In isomeric bodies, the elements and the proportions in which they are combined are the same, only the arrangement of the atoms is differetn... We know, on the one hand, that the molecular arrangements of the two tartaric acids are asymmetric, and on the other hand, that these arrangements are absolutely identical, excepting that they exhibit asymmetry in opposite directions. Are atoms of the dextro acid grouped in the form of a right-handed spiral, or are they placed at the apex of an irregular tetrahedron, or are they disposed according to this or that asymmetric arrangement? We do not know.<ref>From pasteur's lecture to the Societe Chimique de Paris in 1883, quoted in DuBos, R. (1976) Louis Pasteur: Free Lance of Science, p. 95, Charles Scribner's Sons, New York.</ref>
In isomeric bodies, the elements and the proportions in which they are combined are the same, only the arrangement of the atoms is differetn... We know, on the one hand, that the molecular arrangements of the two tartaric acids are asymmetric, and on the other hand, that these arrangements are absolutely identical, excepting that they exhibit asymmetry in opposite directions. Are atoms of the dextro acid grouped in the form of a right-handed spiral, or are they placed at the apex of an irregular tetrahedron, or are they disposed according to this or that asymmetric arrangement? We do not know.<ref>From pasteur's lecture to the Societe Chimique de Paris in 1883, quoted in DuBos, R. (1976) Louis Pasteur: Free Lance of Science, p. 95, Charles Scribner's Sons, New York.</ref>
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Now we do know. X-ray crystallographic studies in 1951 confirmed that the levorotatory and dextrorotatory forms of tartaric acid are mirror images of each other at the molecular level and established the absolute configuration of each. The same approach has been used to demonstrate that although the amino acid alanine has two stereoisomeric forms alanine in proteins exists exclusively in on form, the L isomer.
==References==
==References==