Molecule enantiomer

Drawing a chiral molecule (enantiomer) On a plane paper, chiral molecules can be drawn using wedge bonds. There are also a few other methods that use horizontal bonds representing bonds pointing out of the paper and vertical bonds pointing into the paper. Some examples are given below. 

The chirality of DNA was applied to selective separation. A DNA aptamer as a new target-specific chiral selector for HPLC was investigated by Michaud et al. [119,120]. They showed that a tailor-made chiral stationary phase based on a DNA aptamer with known stereospecific binding for the D-enantiomer of the oligopeptide, arginine-vasopressin, exhibits enantioselectivity between the d- and L-peptides. This DNA-based target-specific aptamer chiral stationary phase provides a powerful tool for the resolution of small (bioactive) molecule enantiomers. 

We know from the standard model of elementary particle physics [116] that there is a tiny weak interaction contribution to every Coulomb interaction. For ordinary matter, where particle interconversion can be ignored, weak interactions due to exchange of neutral Z vector bosons are involved. Unlike the Coulomb interaction, the (neutral and charged variants of) weak interactions do not conserve parity. This leads, in consequence, to a very small energy difference between mirror-image molecules (enantiomers), which in turn might prove to be of importance for the development of a homochiral biochemistry on our planet [117]. 

A method which can discern the subtle differences between nonsuperimposable mirror image molecules (enantiomers) must be highly sensitive to the three-dimensional features of molecules, that is, to conformation. 

Enantiomers (optical isomers) A chiral molecule and its nonsuperimposable, mirror-image molecule. Enantiomers are one type of stereoisomer Stereoisomers Molecules with the same molecular formula but different three-dimensional structures... 

Freedman TB, Long F, Citra M and Nafie LA (1999) Hydrogen stretching vibrational circular dichroism spectroscopy absolute configuration and solution conformation of selected pharmaceutical molecules. Enantiomer (in press). 

For each pair of structures shown below, indicate whether the two species are identical molecules, enantiomers, or isomers of some other sort. 

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