http://hdl.handle.net/2027.42/78361 Wed, 22 May 2013 16:44:48 GMT 2013-05-22T16:44:48Z http://hdl.handle.net/2027.42/75683 ATP-dependent ligases in trypanothione biosynthesis – kinetics of catalysis and inhibition by phosphinic acid pseudopeptides Oza, Sandra L.; Chen, Shoujun; Wyllie, Susan; Coward, James K.; Fairlamb, Alan H. Sat, 01 Nov 2008 00:00:00 GMT http://hdl.handle.net/2027.42/75683 2008-11-01T00:00:00Z http://hdl.handle.net/2027.42/75597 Multifunctional host defense peptides: functional and mechanistic insights from NMR structures of potent antimicrobial peptides Bhattacharjya, Surajit; Ramamoorthy, Ayyalusamy Sun, 01 Nov 2009 00:00:00 GMT http://hdl.handle.net/2027.42/75597 2009-11-01T00:00:00Z http://hdl.handle.net/2027.42/75523 Ratiometric Singlet Oxygen Nano-optodes and Their Use for Monitoring Photodynamic Therapy Nanoplatforms Cao, Youfu; Koo, Yong-Eun Lee; Koo, Sang Man; Kopelman, Raoul Ratiometric photonic explorers for bioanalysis with biologically localized embedding (PEBBLE) nanoprobes have been developed for singlet oxygen, using organically modified silicate (ORMOSIL) nanoparticles as the matrix. A crucial aspect of these ratiometric singlet-oxygen fluorescent probes is their minute size. The ORMOSIL nanoparticles are prepared via a sol-gel–based process and the average diameter of the resultant particles is about 160 nm. These sensors incorporate the singlet-oxygen–sensitive 9,10-dimethyl anthracene as an indicator dye and a singlet-oxygen–insensitive dye, octaethylporphine, as a reference dye for ratiometric fluorescence-based analysis. We have found experimentally that these nanoprobes have much better sensitivity than does the conventional singlet-oxygen–free dye probe, anthracene-9, 10-dipropionic acid disodium salt. The much longer lifetime of singlet oxygen in the ORMOSIL matrix, compared to aqueous solutions, in addition to the relatively high singlet oxygen solubility because of the highly permeable structure and the hydrophobic nature of the outer shell of the ORMOSIL nanoparticles, results in an excellent overall response to singlet oxygen. These nanoprobes have been used to monitor the singlet oxygen produced by “dynamic nanoplatforms” that were developed for photodynamic therapy. The singlet oxygen nanoprobes could potentially be used to quantify the singlet oxygen produced by macrophages. Tue, 01 Nov 2005 00:00:00 GMT http://hdl.handle.net/2027.42/75523 2005-11-01T00:00:00Z http://hdl.handle.net/2027.42/75126 Single amino acid substitutions in either YhjD or MsbA confer viability to 3-deoxy-d- manno -oct-2-ulosonic acid-depleted Escherichia coli Mamat, Uwe; Meredith, Timothy C.; Aggarwal, Parag; Kühl, Annika; Kirchhoff, Paul; Lindner, Buko; Hanuszkiewicz, Anna; Sun, Jennifer; Holst, Otto; Woodard, Ronald W. The Escherichia coli K-12 strain KPM22, defective in synthesis of 3-deoxy-d- manno -oct-2-ulosonic acid (Kdo), is viable with an outer membrane (OM) composed predominantly of lipid IV A , a precursor of lipopolysaccharide (LPS) biosynthesis that lacks any glycosylation. To sustain viability, the presence of a second-site suppressor was proposed for transport of lipid IV A from the inner membrane (IM), thus relieving toxic side-effects of lipid IV A accumulation and providing sufficient amounts of LPS precursors to support OM biogenesis. We now report the identification of an arginine to cysteine substitution at position 134 of the conserved IM protein YhjD in KPM22 that acts as a compensatory suppressor mutation of the lethal δKdo phenotype. Further, the yhjD400 suppressor allele renders the LPS transporter MsbA dispensable for lipid IV A transmembrane trafficking. The independent derivation of a series of non-conditional KPM22-like mutants from the Kdo-dependent parent strain TCM15 revealed a second class of suppressor mutations localized to MsbA. Proline to serine substitutions at either residue 18 or 50 of MsbA relieved the Kdo growth dependence observed in the isogenic wild-type strain. The possible impact of these suppressor mutations on structure and function are discussed by means of a computationally derived threading model of MsbA. Fri, 01 Feb 2008 00:00:00 GMT http://hdl.handle.net/2027.42/75126 2008-02-01T00:00:00Z