(1/957) Diperamycin, a new antimicrobial antibiotic produced by Streptomyces griseoaurantiacus MK393-AF2. I. Taxonomy, fermentation, isolation, physico-chemical properties and biological activities.
Antibacterial antibiotics, diperamycin (1) was produced in the culture broth of Streptomyces griseoaurantiacus MK393-AF2. Various spectroscopic analyses of 1 suggested that 1 belonged to a member of cyclic hexadepsipeptide antibiotic. Antibiotic 1 had potent inhibitory activity against various Gram-positive bacteria including Enterococcus seriolicida and methicillin-resistant Staphylococcus aureus. (+info)
(2/957) Structure of actinotetraose hexatiglate, a unique glucotetraose from an actinomycete bacterium.
An Actinomycete strain A499 belonging to the genera Amycolatopsis or Amycolata isolated from a Western Australian soil sample produced the cyclic decapeptide antibiotic quinaldopeptin (1), together with the actinotetraose hexatiglate (2), the hexa-ester of a novel non-reducing glucotetraose. (+info)
(3/957) Do charge-remote fragmentations occur under matrix-assisted laser desorption ionization post-source decompositions and matrix-assisted laser desorption ionization collisionally activated decompositions?
The precursor ions of tetraphenylporphyrins that are substituted with fatty acids can be introduced into the gas phase by matrix-assisted laser desorption ionization (MALDI) and undergo post-source and collisionally activated decompositions (CAD) in a time-of-flight mass spectrometer. The goal of the research is to obtain a better understanding of post-source decompositions (PSD); specifically, we asked the question of whether ions undergoing PSD have sufficient energy to give charge-remote fragmentations along an alkyl chain. We chose the porphyrin macrocycle because we expected it to act as an inert "support," allowing the molecule to be desorbed by MALDI and to be amenable to charge-remote fragmentation. MALDI-PSD and MALDI-CAD spectra are similar to high-energy CAD spectra and considerably more informative than low-energy CAD spectra, showing that charge-remote fragmentations of the fatty acid moieties do occur upon MALDI-PSD and MALDI-CAD. (+info)
(4/957) IC202A, a new siderophore with immunosuppressive activity produced by Streptoalloteichus sp. 1454-19. II. Physico-chemical properties and structure elucidation.
IC202A (1) was isolated from the culture filtrate of Streptoalloteichus sp. 1454-19. The structure of 1 was determined by spectral analysis including a variety of two-dimentional NMR and FAB-MS experiments. IC202A is a ferrioxamine-related compound containing a butylidene N-oxide function. (+info)
(5/957) Ectopic expression of the minimal whiE polyketide synthase generates a library of aromatic polyketides of diverse sizes and shapes.
The single recombinant expressing the Streptomyces coelicolor minimal whiE (spore pigment) polyketide synthase (PKS) is uniquely capable of generating a large array of well more than 30 polyketides, many of which, so far, are novel to this recombinant. The characterized polyketides represent a diverse set of molecules that differ in size (chain length) and shape (cyclization pattern). This combinatorial biosynthetic library is, by far, the largest and most complex of its kind described to date and indicates that the minimal whiE PKS does not independently control polyketide chain length nor dictate the first cyclization event. Rather, the minimal PKS enzyme complex must rely on the stabilizing effects of additional subunits (i.e., the cyclase whiE-ORFVI) to ensure that the chain reaches the full 24 carbons and cyclizes correctly. This dramatic loss of control implies that the growing polyketide chain does not remain enzyme bound, resulting in the spontaneous cyclization of the methyl terminus. Among the six characterized dodecaketides, four different first-ring cyclization regiochemistries are represented, including C7/C12, C8/C13, C10/C15, and C13/C15. The dodecaketide TW93h possesses a unique 2,4-dioxaadamantane ring system and represents a new structural class of polyketides with no related structures isolated from natural or engineered organisms, thus supporting the claim that engineered biosynthesis is capable of producing novel chemotypes. (+info)
(6/957) Methylation of tea catechins by rat liver homogenates.
Methylation of (-)-epigallocatechin (EGC), (-)-epicatechin gallate (ECg), and (-)-epigallocatechin gallate (EGCg) was carried out with a rat liver homogenate and S-adenosyl-L-methionine. A structural analysis of the reaction products by MS and NMR showed that 4'-O-methyl EGC, 4"-O-methyl ECg, and 4"-O-methyl EGCg had been formed from EGC, ECg, and EGCg, respectively. These results suggest that methylation may be one of the metabolic pathways to the catechins. (+info)
(7/957) Isolation and structural characterization of glycosphingolipids of in vitro propagated human umbilical vein endothelial cells.
To investigate in detail the expression of glycosphingolipids (GSLs) on endothelial cells, 4.85 x 10(9) human umbilical vein endothelial cells (HUVECs) were cultivated in a 2 l bioreactor using microcarriers as a support for anchorage dependent growing cells. Neutral GSLs and gangliosides were isolated and their structures were determined by TLC immunostaining, fast atom bombardment-mass spectrometry (FAB-MS) of the native GSLs, and gas chromatography-electron impact mass spectrometry (GC-EIMS) of partially methylated alditol acetates. GbOse4Cer, GbOse3Cer, and LacCer, all carrying mainly C24- and C16-fatty acid beside C18-sphingosine, were detected as the major neutral GSLs (36%, 23%, and 15% of the total orcinol stain, respectively); GlcCer, nLcOse4Cer, and nLcOse6Cer were expressed to substantial minor amounts (9%, 12%, and 5% of the total orcinol stain, respectively). TLC immunostaining revealed the presence of lipid bound Lewisx antigen, whereas the isomeric Lewisa structure was detectable only in very low quantities. GM3(Neu5Ac) with C18-sphingosine was the major ganglioside constituting about 90% of the whole ganglioside fraction. The fatty acid composition was determined by GC-MS of fatty acid methyl esters, indicating the predominance of C24- and C16-substituted GM3(Neu5Ac), followed by C18- and C22-substituted species. Terminally alpha2-3 sialylated neolacto-series ganglioside IV3Neu5Ac-nLcOse4Cer was the second most abundant ganglioside in HUVECs (8% of the total resorcinol stain), and IV6Neu5Ac-nLcOse4Cer and VI3Neu5Ac-nLcOse6Cer (together less than 2% of total resorcinol stain) were found in minor quantities. Lipid bound sialyl Lewisx antigen with poly-N-acetyllactosaminyl chains, and traces of gangliotetraose-type gangliosides GM1 and GD1a were identified by TLC immunostaining. The expression of dominant neutral GSLs LacCer, GbOse3Cer, and GbOse4Cer, and of ganglioside GM3(Neu5Ac) was assayed by indirect immunofluorescence microscopy of cell layers grown in chamber slides, each showing different plasma membrane and subcellular distribution patterns. The complete structural characterization of GSLs from HUVECs contributes to our understanding about their functional role, not only of the carbohydrate but also of the lipid moiety, as receptors for bacterial toxins, as cell surface antigens of cellular interaction and as receptors for blood components and macromolecules of the extracellular matrix. (+info)
(8/957) The structures of the carbohydrate backbones of the lipopolysaccharides from Escherichia coli rough mutants F470 (R1 core type) and F576 (R2 core type).
The lipopolysaccharides (LPS) from Escherichia coli rough mutant strains F470 (R1 core type) and F576 (R2 core type) were deacylated yielding in each case a mixture of oligosaccharides with one predominant product which was isolated using high-performance anion-exchange chromatography. In addition, one oligosaccharide present in minor quantities was isolated from LPS of E. coli strain F576 (R2 core type). The structures of the oligosaccharides were determined by chemical analyses and NMR spectroscopic experiments. Furthermore, de-O-acylated and dephosphorylated LPS preparations were investigated by fast-atom bombardment and collision induced dissociation tandem mass spectrometry. The combined data allow us to deduce the following carbohydrate backbones of the E. coli R1 and R2 core types which share the following structure (Scheme 1): but differ in the substituents R1 and R2 which for the R1 core type are predominantly: and to a minor extent: and for the R2 core type predominantly: and to a minor extent: in which all sugars are d-pyranoses (l,d-Hep, lglycerodmanno-heptopyranose; P, phosphate). (+info)