Incorporation of beta-selenolo[3,2-b]pyrrolyl-alanine into proteins for phase determination in protein X-ray crystallography.

beta-Selenolo[3,2-b]pyrrolyl-L-alanine that mimics tryptophan with the benzene ring of the indole moiety replaced by selenophene, was incorporated into human annexin V and barstar. This was achieved by fermentation and expression in a Trp-auxotrophic Escherichia coli host strain using the selective pressure incorporation method. The seleno- proteins were obtained in yields comparable to those of the wild-type proteins and exhibit full crystallographic isomorphism to the parent proteins, but expectedly show altered absorbance profiles and quenched tryptophan fluorescence. Since the occurrence of tryptophan residues in proteins is rare, incorporation of the electron-rich selenium-containing tryptophan surrogate into proteins represents a useful supplementation and even a promising novel alternative to selenomethionine for solving the phase problem in protein X-ray crystallography.

Synthesis of neo-glycosylated L-alanyl-D-isoglutamine derivatives as potential immunoadjuvants.

The synthesis is described for muramyl-dipeptide-related amphiphilic analogs, where 1,10-diaminodecane served as a lipophilic C-terminal linker for the preparation of a bidentated L-alanyl-D-isoglutamine derivative and incorporation of aldonic and uronic acids at the N-termini as hydrophilic cores. For the N-acylation steps via lactones, suitable conditions were elaborated to allow for the use of unprotected or minimally protected aldonic and uronic acid lactones, respectively. These procedures may represent a useful general approach for the synthesis of neoglycopeptides.