introducing and removing amino acid blocking groups. Section II deals with coupling methods, and several papers take up the problem of racem-ization. Especially interesting is a report of the use of a gas chromatographic technique to compare the degree of racemization by various commonly used coupling techniques. The third section discusses the occurrence of "unnatural" amino acids and special ...

Lysophosphatidic acid (LPA) and sphingosine 1-phosphate (S1P) are potent biologically active lipid mediators that exert a wide range of cellular effects through specific G protein-coupled receptors. To date, four LPA receptors and five S1P receptors have been identified. These receptors are expressed in a large number of tissues and cell types, allowing for a wide variety of cellular responses ...