Unexpected differences between D- and L-tyrosine lead to chiral enhancement in racemic mixtures - Dedicated to the memory of Prof. Shneior Lifson - A great liberal thinker

M Shinitzky*, F Nudelman, Y Barda, R Haimovitz, E Chen, DW Deamer

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

We report here an unexpected difference in the solubilities of D- and L-tyrosine in water, which could be discerned by their rate of crystallization and the resulting concentrations of their saturated solutions. A supersaturated solution of 10 mM L-tyrosine at 20 degreesC crystallized much more slowly than that of D- tyrosine under the same conditions, and the saturated solution of L-tyrosine was more concentrated than that of D- tyrosine. Supersaturated solutions of 10 mM DL-tyrosine in water formed precipitates of predominantly D- tyrosine and DL-tyrosine, resulting in an excess of L-tyrosine in the saturated solution. The experimental setups were monitored independently by UV-absorption, radioactivity tracing, optical rotation and X-ray diffraction. The process of nucleation and crystallization of D- and L-tyrosine is characterized by an exceptionally high cooperativity. It is possible that minute energy differences between D- and L-tyrosine, originating from parity violation or other non-conservative chiral discriminatory rules, could account for the observations. The physical process that initiated chiral selection in biological systems remains a challenging problem in understanding the origin of life, and it is possible that chiral compounds were concentrated from supersaturated racemic mixtures by preferential crystallization.

Original languageEnglish
Pages (from-to)285-297
Number of pages13
JournalOrigins of life and evolution of biospheres
Volume32
Issue number4
Publication statusPublished - Aug 2002

Keywords

  • chiral selection
  • crystallization
  • enantiomeric discrimination
  • origin of life
  • VIOLATING ENERGY DIFFERENCE
  • BIOMOLECULAR CHIRALITY
  • SYMMETRY-BREAKING
  • AMINO-ACIDS
  • ORIGIN
  • CRYSTALLIZATION
  • HOMOCHIRALITY
  • MOLECULES

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