Chiral selection in poly(C)-directed synthesis of oligo(G)

Area of Science:

• Origin of life studies
• Chiral selection mechanisms
• Prebiotic chemistry

Background:

• Autocatalytic processes are key to amplifying optical asymmetry in early life.
• Polynucleotide replication is a proposed autocatalytic mechanism for chiral amplification.
• Template-directed synthesis offers a model for prebiotic replication.

Purpose of the Study:

• To investigate chiral selection in template-directed guanosine mononucleotide oligomerization.
• To determine the efficiency of replication with homochiral versus heterochiral monomers.
• To assess the impact of opposite-handed monomers on template-directed synthesis.

Main Methods:

• Utilized activated guanosine mononucleotides and a poly(C) template.
• Synthesized L-guanosine 5'-mononucleotide to study chiral selection.
• Performed template-directed oligomerization reactions with varying monomer chirality.

Main Results:

• Oligomerization proceeded efficiently with monomers of the same optical handedness as the poly(C) template.
• Reactions were significantly less efficient with monomers of the opposite handedness.
• Opposite-handed monomers acted as chain terminators in racemic mixtures, inhibiting further elongation.

Conclusions:

• Template-directed synthesis demonstrates strong chiral selection favoring homochirality.
• The chain-terminating effect of opposite-handed monomers presents a challenge for origin-of-life theories relying on simple template replication.
• Further research is needed to reconcile these findings with models for the origin of biological homochirality.