Elongated Polyproline Motifs Facilitate Enamel Evolution through Matrix Subunit Compaction

How does proline-repeat motif length in the proteins of teeth and bones relate to the evolution of vertebrates? Counterintuitively, longer repeat stretches are associated with smaller aggregated subunits within a supramolecular matrix, resulting in enhanced crystal length in mammalian versus amphibian tooth enamel

Theoretical considerations concerning the separation of enantiomeric solutes by liquid chromatography

A statistical thermodynamic theory of chiral solute retention and separation using chiral stationary phase high-performance liquid chromatography (CSP-HPLC) is formulated and applied in the limit of infinite dilution of solute to models of chemically bonded CSPs consisting of either chiral tetrahedral moieties or chiral molecular cavities intended to simulate a cyclodextrin CSP. Explicit expressions are derived for the corresponding separation factors and the likelihood of enantiomeric separation is investigated as a function of the multitude of possible interactions and retention modes for the enantiomers and CSPs considered. The separation factor reduces to a simple Boltzmann factor whenever a dominant retention mode, usually involving strong hydrogen bonding, prevails for both enantiomers. In mixed mobile phases, inversion of enantiomer elution order as a function of composition is a predicted possibility with a cyclodextrin CSP. Enantiomeric separation by diffusion through aqueous solution interphases of cyclodextrin is also investigated. © 1988, American Chemical Society. All rights reserved