Probing the effect of straight chain fatty acids on the properties of lead-containing plexiglass

It was found that, just by adding easily accessible and low-cost straight chain fatty acid additives into the co-polymerization reaction system of lead methacrylate with methyl methacrylate, the optical properties...

The final assembly of trehalose polyphleates takes place within the outer layer of the mycobacterial cell envelope

Trehalose polyphleates (TPP) are high-molecular-weight, surface-exposed glycolipids present in a broad range of nontuberculous mycobacteria. These compounds consist of a trehalose core bearing polyunsaturated fatty acyl substituents (called phleic acids) and a straight-chain fatty acid residue and share a common basic structure with trehalose-based glycolipids produced by Mycobacterium tuberculosis. TPP production starts in the cytosol with the formation of a diacyltrehalose intermediate. An acyltransferase, called PE, subsequently catalyzes the transfer of phleic acids onto diacyltrehalose to form TPP, and an MmpL transporter promotes the export of TPP or its precursor across the plasma membrane. PE is predicted to be an anchored membrane protein, but its topological organization is unknown, raising questions about the subcellular localization of the final stage of TPP biosynthesis and the chemical nature of the substrates that are translocated by the MmpL transporter. Here, using genetic, biochemical, and proteomic approaches, we established that PE of Mycobacterium smegmatis is exported to the cell envelope following cleavage of its signal peptide and that this process is required for TPP biosynthesis, indicating that the last step of TPP formation occurs in the outer layers of the mycobacterial cell envelope. These results provide detailed insights into the molecular mechanisms controlling TPP formation and transport to the cell surface, enabling us to propose an updated model of the TPP biosynthetic pathway. Because the molecular mechanisms of glycolipid production are conserved among mycobacteria, these findings obtained with PE from M. smegmatis may offer clues to glycolipid formation in M. tuberculosis.

Pheromone Bouquet of the Mandibular Glands in Andrena haemorrhoa F. (Hym., Apoidea)

The complex volatile secretion from the mandibular glands of Andrena haemorrhoa (Hym., Apoidea) has been analysed by GC/M S. It is composed primarily of three groups of compounds: 1. Spiroacetals of five different systems: two 1,6-dioxyspiro[4.4]nonanes, four 1,6-dioxaspiro[4.5] decanes, two 1,7-dioxaspiro[5.5]undecanes, one 1,6-dioxaspiro[4.6]undecane and one 1,7-dioxa-spiro[5.6]dodecane. 2. Straight chain fatty acid derivatives: methyl ketones, primary and secondary alcohols, acetates and hydrocarbons. 3. Isoprenoids: geraniol and geranyl acetate. Mass spectral fragmentation patterns have been studied for several synthesized spiroacetals.