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71.
72.
A collection of the cyanobacterium Lyngbya confervoides off Grassy Key in Florida yielded grassypeptolide (1), a 31-membered macrocyclic depsipeptide with unusually high D-amino acid content, two thiazolines, and one beta-amino acid. We report the rigorous 3D structure determination and conformational analysis in solution and solid state by NMR, MS, X-ray crystallography, chemical degradation, and molecular modeling involving distance geometry and restrained molecular dynamics. Grassypeptolide (1) inhibited cancer cell growth with IC50 values from 1.0 to 4.2 microM. 相似文献
73.
Money VA Cartmell A Guerreiro CI Ducros VM Fontes CM Gilbert HJ Davies GJ 《Organic & biomolecular chemistry》2008,6(5):851-853
The substrate binding regions of a beta-1,3:1,4 glucanase are revealed through structural analysis with a thio-oligosaccharide and kinetics of enzyme variants. 相似文献
74.
Marine chemical ecology 总被引:1,自引:0,他引:1
This review covers the recent marine chemical ecology literature for benthic cyanobacteria, macroalgae, sponges, octocorals, molluscs, other benthic invertebrates, fish and seabirds. 相似文献
75.
Dr. Jamal El Bakali Dr. Michal Blaszczyk Dr. Joanna C. Evans Dr. Jennifer A. Boland Dr. William J. McCarthy Imam Fathoni Dr. Marcio V. B. Dias Dr. Eachan O. Johnson Dr. Anthony G. Coyne Prof. Valerie Mizrahi Prof. Tom L. Blundell Prof. Chris Abell Dr. Christina Spry 《Angewandte Chemie (International ed. in English)》2023,62(17):e202300221
The coenzyme A (CoA) biosynthesis pathway has attracted attention as a potential target for much-needed novel antimicrobial drugs, including for the treatment of tuberculosis (TB), the lethal disease caused by Mycobacterium tuberculosis (Mtb). Seeking to identify inhibitors of Mtb phosphopantetheine adenylyltransferase (MtbPPAT), the enzyme that catalyses the penultimate step in CoA biosynthesis, we performed a fragment screen. In doing so, we discovered three series of fragments that occupy distinct regions of the MtbPPAT active site, presenting a unique opportunity for fragment linking. Here we show how, guided by X-ray crystal structures, we could link weakly-binding fragments to produce an active site binder with a KD <20 μM and on-target anti-Mtb activity, as demonstrated using CRISPR interference. This study represents a big step toward validating MtbPPAT as a potential drug target and designing a MtbPPAT-targeting anti-TB drug. 相似文献
76.
77.
Bercaw JE Hazari N Labinger JA Scott VJ Sunley GJ 《Journal of the American Chemical Society》2008,130(36):11988-11995
InI3 catalyzes the reaction of branched alkanes with methanol to produce heavier and more highly branched alkanes, which are more valuable fuels. The reaction of 2,3-dimethylbutane with methanol in the presence of InI3 at 180-200 degrees C affords the maximally branched C7 alkane, 2,2,3-trimethylbutane (triptane). With the addition of catalytic amounts of adamantane the selectivity of this transformation can be increased up to 60%. The lighter branched alkanes isobutane and isopentane also react with methanol to generate triptane, while 2-methylpentane is converted into 2,3-dimethylpentane and other more highly branched species. Observations implicate a chain mechanism in which InI3 activates branched alkanes to produce tertiary carbocations which are in equilibrium with olefins. The latter react with a methylating species generated from methanol and InI3 to give the next-higher carbocation, which accepts a hydride from the starting alkane to form the homologated alkane and regenerate the original carbocation. Adamantane functions as a hydride transfer agent and thus helps to minimize competing side reactions, such as isomerization and cracking, that are detrimental to selectivity. 相似文献
78.
The kinetics of the reactions between [Zn4(SPh)10](2-) and an excess of MX2 (M = Co, X = NO3 or Cl; M = Fe, X = Cl), in which a Zn(II) is replaced by M(II), have been studied in MeCN at 25.0 degrees C. (1)H NMR spectroscopy shows that the ultimate product of the reactions is an equilibrium mixture of clusters of composition [Zn(n)M(4-n)(SPh)10](2-), and this is reflected in the multiphasic absorbance-time curves observed over protracted times (several minutes) using stopped-flow spectrophotometry to study the reactions. The kinetics of only the first phase have been determined, corresponding to the equilibrium formation of [Zn3M(SPh)10](2-). The effects of varying the concentrations of cluster, MX2, and ZnCl2 on the kinetics have been investigated. The rate law is consistent with the equilibrium nature of the metal exchange process and indicates a mechanism for the formation of [Zn3M(SPh)10](2-) involving two coupled equilibria. In the initial step binding of MX2 to a bridging thiolate in [Zn4(SPh)10](2-) results in breaking of a Zn-bridging thiolate bond. In the second step replacement of the cluster Zn involves transfer of the bridging thiolates from the Zn to M, with breaking of a Zn-bridged thiolate bond being rate-limiting. The kinetics for the reaction of ZnCl2 with [Zn3M(SPh)10](2-) (M = Fe or Co)} depends on the identity of M. This behavior indicates attack of ZnCl2 at a M-mu-SPh-Zn bridged thiolate. Similar studies on the analogous reactions between [Fe4(SPh)10](2-) and an excess of CoX2 (X = NO3 or Cl) in MeCN exhibit simpler kinetics but these are also consistent with the same mechanism. 相似文献
79.
The mechanism for the interaction of thioflavin T (ThT) with amyloid fibrils at the molecular level is not known. Here, we used 1H NMR spectroscopy to determine the binding mode of ThT on the surface of fibrils from lysozyme and insulin. Relayed rotating‐frame Overhauser enhancements in ThT were observed, indicating that the orientation of ThT is orthogonal to the fibril surface. Importantly, the assembly state of ThT on both surfaces is different. On the surface of insulin fibrils, ThT is oligomeric, as indicated by rapid 1H spin‐lattice relaxation rate in the rotating frame (R1ρ), presumably due to intermolecular dipole–dipole interactions between ThT molecules. In contrast, ThT on the surface of lysozyme fibrils is a monomer, as indicated by slower 1H R1ρ. These results shed new light into the mechanism for the enhancement of ThT fluorescence and may lead to more efficient detectors of amyloid assemblies, which have escaped detection by ThT in monomer form. 相似文献
80.
Sizing large proteins and protein complexes by electrospray ionization mass spectrometry and ion mobility 总被引:1,自引:0,他引:1
Kaddis CS Lomeli SH Yin S Berhane B Apostol MI Kickhoefer VA Rome LH Loo JA 《Journal of the American Society for Mass Spectrometry》2007,18(7):1206-1216
Mass spectrometry (MS) and ion mobility with electrospray ionization (ESI) have the capability to measure and detect large noncovalent protein-ligand and protein-protein complexes. Using an ion mobility method of gas-phase electrophoretic mobility molecular analysis (GEMMA), protein particles representing a range of sizes can be separated by their electrophoretic mobility in air. Highly charged particles produced from a protein complex solution using electrospray can be manipulated to produce singly charged ions, which can be separated and quantified by their electrophoretic mobility. Results from ESI-GEMMA analysis from our laboratory and others were compared with other experimental and theoretically determined parameters, such as molecular mass and cryoelectron microscopy and X-ray crystal structure dimensions. There is a strong correlation between the electrophoretic mobility diameter determined from GEMMA analysis and the molecular mass for protein complexes up to 12 MDa, including the 93 kDa enolase dimer, the 480 kDa ferritin 24-mer complex, the 4.6 MDa cowpea chlorotic mottle virus (CCMV), and the 9 MDa MVP-vault assembly. ESI-GEMMA is used to differentiate a number of similarly sized vault complexes that are composed of different N-terminal protein tags on the MVP subunit. The average effective density of the proteins and protein complexes studied was 0.6 g/cm(3). Moreover, there is evidence that proteins and protein complexes collapse or become more compact in the gas phase in the absence of water. 相似文献