Why are enantiomers of biological interest?

Question

another question i have ponderd for many a week... heh some help would be of great value!!!

Answer 1

The left- and right-handed enantiomers have identical physical properties like melting point, and almost, but not quite identical chemical properties. In a complicated biological system like a human body, the chemical differences between the two enantiomers are important. So nucleic acids and amino acids only come in one version in nature. If we ever come across proteins or DNA made of the opposite enantiomer anywhere in the universe, it will be convincing evidence of extraterrestrial life. The drug thalidomide which caused all those birth defects in the early 60s was a racemic mix of the two enantiomers. Unfortunately it was the enantiomer which had no medicinal effect that did the damage. If the manufacturing process had removed it, the drug would still have had the desired effect without causing any birth defects.