Monitoring of solid phase peptide synthesis by FT-IR spectroscopy

Aggregation phenomena of growing peptides on the resin have seldom been investigated. We report here how conformations are determined by FT-IR spectroscopy. Therefore the sequence 80–99 of HIV 1-protease was synthesized. After every coupling a resin sample was taken out of the reaction column and a FT-IR spectrum recorded. The results were compared with the UV monitoring obtained from another synthesis of the same peptide. © 1998 European Peptide Society and John Wiley & Sons, Ltd.     

Novel insights into biosynthesis and uptake of rhamnolipids and their precursors

Applied Microbiology and Biotechnology - The human pathogenic bacterium Pseudomonas aeruginosa produces rhamnolipids, glycolipids with functions for bacterial motility, biofilm formation, and...     

Neurofibromin Homologs Ira1 and Ira2 Affect Glycerophosphoinositol Production and Transport in Saccharomyces cerevisiae

Saccharomyces cerevisiae produces extracellular glycerophosphoinositol through phospholipase-mediated turnover of phosphatidylinositol and transports glycerophosphoinositol into the cell upon nutrient limitation. A screening identified the RAS GTPase-activating proteins Ira1 and Ira2 as required for utilization of glycerophosphoinositol as the sole phosphate source, but the RAS/cyclic AMP pathway does not appear to be involved in the growth phenotype. Ira1 and Ira2 affect both the production and transport of glycerophosphoinositol.Membrane phospholipids are continually synthesized and degraded as cells grow and respond to environmental conditions. A major pathway of phosphatidylinositol (PI) turnover in Saccharomyces cerevisiae is its deacylation to produce extracellular glycerophosphoinositol (GroPIns) (3). Plb3, an enzyme with phospholipase B (PLB)/lysophospholipase activity, is thought to be primarily responsible for the production of extracellular GroPIns, with Plb1 playing a lesser role (11, 12, 13). GroPIns is transported into the cell by the Git1 permease (17). GIT1 expression is upregulated by phosphate limitation and inositol limitation. In fact, GroPIns can act as the cell''s sole source of both inositol (17) and phosphate (1).A screening for gene products involved in the process by which GroPIns enters the cellular metabolism identified Ira1 and Ira2, yeast homologs of the mammalian protein neurofibromin. Alterations in NF1, the gene encoding neurofibromin, are associated with the pathogenesis of neurofibromatosis type 1, an autosomal dominant genetic disease (4, 5, 25). Ira1 and Ira2 and neurofibromin function as RAS GTPase-activating proteins (RAS GAPs). S. cerevisiae Ras1 and Ras2 activate adenylate cyclase to modulate cyclic AMP (cAMP) levels. The binding of cAMP to the regulatory subunits of protein kinase A (Bcy1) results in dissociation and activation of the catalytic subunits (Tpk1 to Tpk3). Ira1 and Ira2 inactivate RAS and thereby downregulate the pathway (18, 19). Hydrolysis of cAMP by the phosphodiesterases encoded by PDE1 and PDE2 also downregulate the pathway (7, 20, 23). The RAS/cAMP pathway responds to nutrient signals to modulate fundamental cellular processes, including stress resistance, metabolism, and cell proliferation (7, 20, 21).     

Cantharellus pleurotoides, a new and unusual basidiomycete from Guyana

Cantharellus pleurotoides sp. nov. (Cantharellaceae, Cantharellales, Basidiomycota) is described from the Pakaraima Mountains of Guyana, occurring in rainforests dominated by ectomycorrhizal Dicymbe spp. (Caesalpiniaceae). This fungus is singular among Cantharellus species described worldwide in possessing a pleurotoid basidioma. Macromorphological, micromorphological, and habitat data are provided for the new species.     

Synapse clusters are preferentially formed by synapses with large recycling pool sizes

Synapses are distributed heterogeneously in neural networks. The relationship between the spatial arrangement of synapses and an individual synapse's structural and functional features remains to be elucidated. Here, we examined the influence of the number of adjacent synapses on individual synaptic recycling pool sizes. When measuring the discharge of the styryl dye FM1-43 from electrically stimulated synapses in rat hippocampal tissue cultures, a strong positive correlation between the number of neighbouring synapses and recycling vesicle pool sizes was observed. Accordingly, vesicle-rich synapses were found to preferentially reside next to neighbours with large recycling pool sizes. Although these synapses with large recycling pool sizes were rare, they were densely arranged and thus exhibited a high amount of release per volume. To consolidate these findings, functional terminals were marked by live-cell antibody staining with anti-synaptotagmin-1-cypHer or overexpression of synaptopHluorin. Analysis of synapse distributions in these systems confirmed the results obtained with FM 1-43. Our findings support the idea that clustering of synapses with large recycling pool sizes is a distinct developmental feature of newly formed neural networks and may contribute to functional plasticity.     

Distinct intracellular vesicle transport mechanisms are selectively modified by spastin and spastin mutations

Spastin is a microtubule severing ATPase that regulates intracellular and axonal transport of vesicles. Intracellular vesicle trafficking was analyzed in differentiated SH‐SY5Y‐neuroblastoma cells, transfected with spastin wild‐type and three spastin mutations (ΔN, K388R, S44L) to investigate spastin‐mediated effects on the velocity of vesicles, stained with LysoTracker Red®. The vesicle velocity varied considerably between mutations and detailed analysis revealed up to five distinct velocity classes. Microtubule severing by overexpressed wild‐type spastin caused reduced vesicle velocity. S44L and ΔN mutations, which were functionally impaired, showed similar velocities as control cells. K388R‐transfected cells exhibited an intermediate velocity profile. The results support the idea that spastin mutations not only alter axonal transport, but in addition regulate intracellular trafficking in the cell soma as well. J. Cell. Physiol. 226: 362–368, 2011. © 2010 Wiley‐Liss, Inc.     

New species and distribution records of Clavulina (Cantharellales, Basidiomycota) from the Guiana Shield

Two new species of Clavulina Schroet. (Clavulinaceae, Cantharellales, Basidiomycota) and new distribution records for Clavulina amazonensis Corner and Clavulina sprucei (Berk.) Corner are described from the Pakaraima Mountains of Guyana, in the central Guiana Shield region. These fungi occur in rainforests dominated by ectomycorrhizal (ECM) trees of the leguminous genus Dicymbe (Fabaceae subfam. Caesalpinioideae). Macromorphological, micromorphological and habitat data are provided for each species. Nuclear ribosomal DNA sequences of the internal transcribed spacer region and 28S subunit were obtained for new species and from representative collections of C. amazonensis and C. sprucei. The two new species, Clavulina kunmudlutsa sp. nov. and Clavulina tepurumenga sp. nov., constitute important edible fungi for the Patamona Amerindians. Our specimens of C. sprucei represent the first reports of the species since 1853 as well as a range extension of nearly 1500 km, while sequence data from basidiomata as well as ECM roots suggest that this taxon consists of a cryptic species complex.