Abstract: Single-module nonribosomal peptide synthetases (NRPSs) and NRPS-like enzymes activate and transform carboxylic acids in both primary and secondary metabolism; and are of great interest due to their biocatalytic potentials. The single-module NRPS IvoA is essential for fungal pigment biosynthesis. As disclosed herein, we show that IvoA catalyzes ATP-dependent unidirectional stereoinversion of L-tryptophan to D-tryptophan with complete conversion. While the stereoinversion is catalyzed by the epimerization (E) domain, the terminal condensation (C) domain stereoselectively hydrolyzes D-tryptophanyl-S-phosphopantetheine thioester and thus represents a noncanonical C domain function. Using IvoA, we demonstrate a biocatalytic stereoinversion/deracemization route to access a variety of substituted D-tryptophan analogs in high enantiomeric excess.

Abstract: A new and improved lift mechanism which is suitably adapted for raising and lowering a pedestal/heater assembly inside a processing chamber for semiconductor wafer substrates. The pedestal/heater assembly lift mechanism includes a drive motor which is directly coupled through a shaft coupling to a threaded lead screw for rotating the lead screw in the clockwise or counterclockwise direction. The lead screw threadibly engages the pedestal/heater assembly for selectively raising and lowering the pedestal/heater assembly inside the processing chamber.