Fumonisin intake of the German consumer

In order to calculate the dietary fumonisin intake of the German consumer, a large survey was carried out on a variety of potentially contaminated products in the period between December 1998 and July 2001. A total of 1960 food samples comprising all known relevant groups of products were analysed for fumonisins. Furthermore, 272 of these samples were also analysed for hydrolysed fumonisins (HFB). For routine analysis enzyme immunoassay was used, confirmatory and control analyses were performed using HPLC-FLD after precolumn derivatisation, or by LC-MS/MS. Daily intake of fumonisins was calculated by combining fumonisin contamination data obtained in this study with available food consumption data for Germany. In a “mean case” scenario, median fumonisin levels in foods and mean food intake values were used. To generate a “bad case” scenario, the 90^th percentile of fumonisin levels in foods and mean food intake values were combined. The overall daily fumonisin intake by the German consumer was 1.1 μg in the “mean case” scenario, and 21 μg in the “bad case” scenario. It was concluded that in general there is no increased risk for the German consumer in aspects of exceeding the recommended tolerable daily intake of fumonisins (2 μg/kg body weight). However, certain products (and certain brands of products) were repeatedly found to contain elevated fumonisin levels, which in a “worst case” scenario (“high” food intake of maize-based products) could pose a potential risk for the consumer, in particular concerning foods for infants and young children. High fumonisin levels were found in infant foods in 1999, but contamination levels decreased strongly in the following years. HFBs (mostly HFB₁) were frequently found in processed cereals such as corn flakes, but in relatively low concentrations. According to our findings, the new European Union maximum levels for fumonisins are suitable to eliminate peak contamination levels of fumonisins in foods, but would lead to a regular excess of the TDI for infants and young children if these maximum levels would indeed be exhausted. Financial support: This work was financially supported by the German Federal Ministry for Nutrition, Agriculture and Consumer Protection, research grant 415-6080-1/60 (BMG alt).     

Protein threading by recursive dynamic programming.

We present the recursive dynamic programming (RDP) method for the threading approach to three-dimensional protein structure prediction. RDP is based on the divide-and-conquer paradigm and maps the protein sequence whose backbone structure is to be found (the protein target) onto the known backbone structure of a model protein (the protein template) in a stepwise fashion, a technique that is similar to computing local alignments but utilising different cost functions. We begin by mapping parts of the target onto the template that show statistically significant similarity with the template sequence. After mapping, the template structure is modified in order to account for the mapped target residues. Then significant similarities between the yet unmapped parts of the target and the modified template are searched, and the resulting segments of the target are mapped onto the template. This recursive process of identifying segments in the target to be mapped onto the template and modifying the template is continued until no significant similarities between the remaining parts of target and template are found. Those parts which are left unmapped by the procedure are interpreted as gaps.The RDP method is robust in the sense that different local alignment methods can be used, several alternatives of mapping parts of the target onto the template can be handled and compared in the process, and the cost functions can be dynamically adapted to biological needs.Our computer experiments show that the RDP procedure is efficient and effective. We can thread a typical protein sequence against a database of 887 template domains in about 12 hours even on a low-cost workstation (SUN Ultra 5). In statistical evaluations on databases of known protein structures, RDP significantly outperforms competing methods. RDP has been especially valuable in providing accurate alignments for modeling active sites of proteins.RDP is part of the ToPLign system (GMD Toolbox for protein alignment) and can be accessed via the WWW independently or in concert with other ToPLign tools at http://cartan.gmd.de/ToPLign.html.     

Subcellular localization of tissue polypeptide antigen and cytokeratins in epithelial cells (salivary ad mammary glands). Combined use of the cryoultramicrotomy and the protein A-gold technique

Epithelial cells from various sites and at various stages of differentiation reveal distinct cytokeratin polypeptide patterns. WE have localized these heterogeneous elements at the subcellular level in human salivary glands and in a solid tumor of the breast using a monoclonal and a polyclonal antibody against cytokeratin, and an antibody against tissue polypeptide antigen (TPA) which seems to be related to some cytokeratins. Labeling by the cytokeratin antibodies was more intense in squamous and duct cells than in acinar cells. The TPA:B1 antibody reacted predominantly with duct cells and to a lesser extent with acinar and squamous cells. A precise evaluation of the labeling pattern and a well-preserved cell structure appeared to be important factors in obtaining more detailed information about intermediate filament proteins. The cryoultramicrotomy and the protein A-gold technique are suitable for these studies.     

QTL Dissection of Lag Phase in Wine Fermentation Reveals a New Translocation Responsible for Saccharomyces cerevisiae Adaptation to Sulfite

Quantitative genetics and QTL mapping are efficient strategies for deciphering the genetic polymorphisms that explain the phenotypic differences of individuals within the same species. Since a decade, this approach has been applied to eukaryotic microbes such as Saccharomyces cerevisiae in order to find natural genetic variations conferring adaptation of individuals to their environment. In this work, a QTL responsible for lag phase duration in the alcoholic fermentation of grape juice was dissected by reciprocal hemizygosity analysis. After invalidating the effect of some candidate genes, a chromosomal translocation affecting the lag phase was brought to light using de novo assembly of parental genomes. This newly described translocation (XV-t-XVI) involves the promoter region of ADH1 and the gene SSU1 and confers an increased expression of the sulfite pump during the first hours of alcoholic fermentation. This translocation constitutes another adaptation route of wine yeast to sulfites in addition to the translocation VIII-t-XVI previously described. A population survey of both translocation forms in a panel of domesticated yeast strains suggests that the translocation XV-t-XVI has been empirically selected by human activity.     

Hyperosmotic stress alters the RNA polymerase II interactome and induces readthrough transcription despite widespread transcriptional repression

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A Molecular Mechanics and Database Analysis of the Structural Preorganization and Activation of the Chromophore-Containing Hexapeptide Fragment in Green Fluorescent Protein

Abstract

We propose that heterologous posttranslational chromophore formation in green fluorescent protein (GFP) occurs because the chromophore-forming amino acid residues 65SYG67 are preorganized and activated for imidazolinone ring formation. Based on extensive molecular mechanical conformational searching of the precursor hexapeptide fragment (64FSYGVQ69), we suggest that the presence of low energy conformations characterized by short contacts (～3Å) between the carbonyl carbon of Ser65 and the amide nitrogen of Gly67 accounts for the initial step in posttranslational chromophore formation. Database searches showed that the tight turn required to establish the key short contact is a unique structural motif that is rarely found, except in other FSYG tetrapeptide sequences. Additionally, ab initio calculations demonstrated that an arginine side chain can hydrogen bond to the carbonyl oxygen of Ser65, activating this group for nucleophilic attack by the nearby lone pair of the Gly67 amide nitrogen. We propose that GFP chromophore-formation is initiated by a unique combination of conformational and electronic enhancements, identified by computational methods.