Combined Non-invasive PIXE/PIGE Analyses of Mammoth Ivory from Aurignacian Archaeological Sites.

Among the earliest Homo sapiens societies in Eurasia, the Aurignacian phase of the Early Upper Paleolithic, approximately 40 000-30 000 years ago, mammoth ivory assumed great social and economic significance, and was used to create hundreds of personal ornaments as well as the earliest known works of three-dimensional figurative art in the world. This paper reports on the results of micro-PIXE/PIGE analyses of mammoth-ivory artifacts and debris from five major sites of Aurignacian ivory use. Patterns of variable fluorine content indicate regionally distinctive strategies of ivory procurement that correspond to apparent differences in human-mammoth interactions.

The performance of tranchet blows at the Late Middle Paleolithic site of Grotte de la Verpillière I (Saône-et-Loire, France).

This paper focuses on the technological characteristics of Keilmesser with a lateral tranchet blow modification on the cutting edge. It examines the underlying technological production of these bifacial objects: this implies the evaluation of their working stage succession, as well as produced forms necessary for the execution of tranchet blow performance. Furthermore, it offers a techno-morphological description of these enigmatic tools.

Streams as Entanglement of Nature and Culture: European Upper Paleolithic River Systems and Their Role as Features of Spatial Organization.

Large river valleys have long been seen as important factors to shape the mobility, communication, and exchange of Pleistocene hunter-gatherers. However, rivers have been debated as either natural entities people adapt and react to or as cultural and meaningful entities people experience and interpret in different ways. Here, we attempt to integrate both perspectives.

Insights into a divergent phenazine biosynthetic pathway governed by a plasmid-born esmeraldin gene cluster.

Phenazine-type metabolites arise from either phenazine-1-carboxylic acid (PCA) or phenazine-1,6-dicarboxylic acid (PDC). Although the biosynthesis of PCA has been studied extensively, PDC assembly remains unclear. Esmeraldins and saphenamycin, the PDC originated products, are antimicrobial and antitumor metabolites isolated from Streptomyces antibioticus Tü 2706.

Broad substrate specificity of the amide synthase in S. hygroscopicus--new 20-membered macrolactones derived from geldanamycin.

The amide synthase of the geldanamycin producer, Streptomyces hygroscopicus, shows a broader chemoselectivity than the corresponding amide synthase present in Actinosynnema pretiosum, the producer of the highly cytotoxic ansamycin antibiotics, the ansamitocins. This was demonstrated when blocked mutants of both strains incapable of biosynthesizing 3-amino-5-hydroxybenzoic acid (AHBA), the polyketide synthase starter unit of both natural products, were supplemented with 3-amino-5-hydroxymethylbenzoic acid instead. Unlike the ansamitocin producer A.

N-methylation of the amide bond by methyltransferase asm10 in ansamitocin biosynthesis.

Ansamitocins are potent antitumor agents produced by Actinosynnema pretiosum. As deduced from their structures, an N-methylation on the amide bond is required among the various modifications. The protein encoded by asm10 belongs to the SAM-dependent methyltransferase family.

The biosynthesis of 3-amino-5-hydroxybenzoic acid (AHBA), the precursor of mC7N units in ansamycin and mitomycin antibiotics: a review.

The aminoshikimate pathway of formation of 3-amino-5-hydroxybenzoic acid (AHBA), the precursor of ansamycin and other antibiotics is reviewed. In this biosynthesis, genes for kanosamine formation have been recruited from other genomes, to provide a nitrogenous precursor. Kanosamine is then phosphorylated and converted by common cellular enzymes into 1-deoxy-1-imino-erythrose 4-phosphate, the substrate for the formation of aminoDAHP.

Timing of the Delta(10,12)-Delta(11,13) double bond migration during ansamitocin biosynthesis in Actinosynnema pretiosum.

The timing of introduction of the unusually placed Delta(11,13) diene system in ansamitocin (AP) biosynthesis was probed by synthesizing optically active potential tri- and tetraketide intermediates as their SNAC thioesters. An AP-nonproducing mutant Actinosynnema pretiosum was complemented by the R enantiomer of the triketide and by the tetraketide with rearranged double bonds, but not by the tetraketide carrying the double bonds in conjugation to the thioester function. The results show that the double bonds are installed in their final positions during processing of the nascent polyketide on module 3 of the asm PKS and that KS4 of the PKS acts as a gatekeeper which accepts only a tetraketide with shifted double bonds as substrate for further processing.

Amide N-glycosylation by Asm25, an N-glycosyltransferase of ansamitocins.

Ansamitocins are potent antitumor maytansinoids produced by Actinosynnema pretiosum. Their biosynthesis involves the initial assembly of a macrolactam polyketide, followed by a series of postpolyketide synthase (PKS) modifications. Three ansamitocin glycosides were isolated from A.

On the biosynthetic origin of methoxymalonyl-acyl carrier protein, the substrate for incorporation of "glycolate" units into ansamitocin and soraphen A.

Feeding experiments with isotope-labeled precursors rule out hydroxypyruvate and TCA cycle intermediates as the metabolic source of methoxymalonyl-ACP, the substrate for incorporation of "glycolate" units into ansamitocin P-3, soraphen A, and other antibiotics. They point to 1,3-bisphosphoglycerate as the source of the methoxymalonyl moiety and show that its C-1 gives rise to the thioester carbonyl group (and hence C-1 of the "glycolate" unit), and its C-3 becomes the free carboxyl group of methoxymalonyl-ACP, which is lost in the subsequent Claisen condensation on the type I modular polyketide synthases (PKS). d-[1,2-(13)C(2)]Glycerate is also incorporated specifically into the "glycolate" units of soraphen A, but not of ansamitocin P-3, suggesting differences in the ability of the producing organisms to activate glycerate.

Determination of the cryptic stereochemistry of the first PKS chain-extension step in ansamitocin biosynthesis by Actinosynnema pretiosum.

The biosynthesis of the antitumor antibiotic, ansamitocin, involves the assembly of a linear octaketide on the ansamitocin (asm) polyketide synthase (PKS), which is then cyclized to proansamitocin and further modified to the final product. In the first chain-extension step on the asm PKS, a stereocenter is generated which is then obliterated in a subsequent double-bond migration. The cryptic configuration at this stereocenter was determined by first synthesizing the two enantiomers of the intermediate diketide as their N-acetylcysteamine (SNAC) thioesters.

From ergot to ansamycins-45 years in biosynthesis.

In this review the author traces his scientific career from its beginnings in Germany to his moves to, successively, Purdue University, The Ohio State University, and finally University of Washington. During this time his research progressed from extensive studies on ergot alkaloids, the stereochemistry of enzyme reactions, and tracer studies on antibiotic biosynthesis to its latest emphasis on the molecular biology of ansamycin antibiotics. The formative influence of several mentors and colleagues is acknowledged.

Combinatorial biosynthesis--potential and problems.

Because of their ecological functions, natural products have been optimized in evolution for interaction with biological systems and receptors. However, they have not necessarily been optimized for other desirable drug properties and thus can often be improved by structural modification. Using examples from the literature, this paper reviews the opportunities for increasing structural diversity among natural products by combinatorial biosynthesis, i.

Identification of tailoring genes involved in the modification of the polyketide backbone of rifamycin B by Amycolatopsis mediterranei S699.

Rifamycin B biosynthesis by Amycolatopsis mediterranei S699 involves a number of unusual modification reactions in the formation of the unique polyketide backbone and decoration of the molecule. A number of genes believed to be involved in the tailoring of rifamycin B were investigated and the results confirmed that the formation of the naphthalene ring moiety of rifamycin takes place during the polyketide chain extension and is catalysed by Rif-Orf19, a 3-(3-hydroxyphenyl)propionate hydroxylase-like protein. The cytochrome P450-dependent monooxygenase encoded by rif-orf5 is required for the conversion of the Delta12, 29 olefinic bond in the polyketide backbone of rifamycin W into the ketal moiety of rifamycin B.

Suitability of the German test method for cleaning efficacy in washer-disinfectors for flexible endoscopes according to prEN ISO 15883.

In Europe, the evaluation of processing flexible endoscopes in washer-disinfectors (WDs) is performed in compliance with prEN ISO 15883-1 which includes determination of the efficacy of the cleaning process. Recent data suggest that cleaning processes show large differences when the prEN ISO 15883-1 German test model is applied. Hence, we analysed a total of 72 experiments in order to evaluate the test method.

Metabolism studies of the anti-tumor agent maytansine and its analog ansamitocin P-3 using liquid chromatography/tandem mass spectrometry.

Maytansine, a potent clinically evaluated plant-derived anti-tumor drug, and its microbial counterpart, ansamitocin P-3, showed a substantially higher cytoxicity than many other anti-tumor drugs. Owing to a shortage of material and lack of sufficiently sensitive analytical methods at the time, no metabolism studies were apparently carried out in conjunction with the initial preclinical and clinical studies on maytansine, but some products of decomposition during the period of storage of the formulated drug were reported. In the current study, the in vitro metabolism of maytansine and ansamitocin P-3 was studied after incubation with rat and human liver microsomes in the presence of NADPH, and with rat and human plasma and whole blood, using liquid chromatography/multi-stage mass spectrometry.