Racemic dating

This is the basis of the amino acid racemization dating method.

Its main proponent is Jeffrey Bada of the Scripps Institution of Oceanography in La Jolla, California.

For the reaction of changing left-handed to right-handed amino acids (L → R), or the reverse (R → L), ΔG = 0, so K = 1. separate the two enantiomers), another homochiral substance must be introduced.

That is, the reaction reaches equilibrium when the concentrations of R and L are equal; that is, a racemate is produced. The procedure is explained in any organic chemistry textbook.

All amino acids in proteins are ‘left-handed’, while all sugars in DNA and RNA, and in the metabolic pathways, are ‘right-handed’.

A 50/50 mixture of left- and right-handed forms is called a racemate or racemic mixture.

Unfortunately, the synthesis of the drug produced a racemate, as would be expected, and the wrong enantiomer was not removed before the drug was marketed. We resolved it by reacting it with a homochiral acid from a plant source, forming diastereomers that could be resolved by fractional crystallisation.

When the resultant homochiral crystals were dissolved, and activated charcoal (a catalyst) added, the substance quickly racemized, because a catalyst accelerates approach to equilibrium.

Of course, many homochiral polymers are required for life, so the probabilities must be compounded. A further problem is that homochiral biological substances racemize in time.

Adrenalin (EPINEPHrine)." A-S Medication Solutions, Chicago, IL.

Adrenaclick Two-Pack (EPINEPHrine)." Amedra Pharmaceuticals LLC, Middlesex, NJ.

Origin-of-life researchers have tried to think of other means of producing the required homochirality.

There have been unsuccessful attempts to resolve racemates by other means.

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