Browsing by Subject "biotin"

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Open Access
Distributions of Parameters and Features of Multiple Bond Ruptures in Force Spectroscopy by Atomic Force Microscopy
(2010) Guo, S; Li, N; Lad, N; Desai, S; Akhremitchev, BB
Force spectroscopy measurement of rupture forces of bound molecules becomes an important physicochemical tool in characterizing intermolecular interactions, Atomic force microscopy (AFM) measurements are among the most common approaches in implementation of this technique. Kinetic information about the molecular bond under study is usually extracted assuming that the detected rupture force comes from rupturing of a single bond. However, multiple bond ruptures might occur in experiments. In this article, we consider how the presence of multiple bonds is manifested in the distribution of parameters that are typically extracted in force spectroscopy experiments. Of particular interest here are the distributions of rupture forces and Kuhn lengths of polymeric tethers. We show that multiple bond ruptures might contribute to the measured distributions even when these distributions have a well-defined single peak. Also, we consider how the probability to form multiple bonds depends on probe velocity. The developed analytical models are applied to experimental data of biotin streptavidin ruptures. The velocity dependence of the amplitude of high force tail supports the hypothesis of multiple bond nature of the measured high forces.
Open Access
The Contribution of Horizontal Gene Transfer to the Evolution of Fungi.
(2007-05-10T14:55:20Z) Hall, Charles Robert
The genomes of the hemiascomycetes Saccharomyces cerevisiae and Ashbya gossypii have been completely sequenced, allowing a comparative analysis of these two genomes, which reveals that a small number of genes appear to have entered these genomes as a result of horizontal gene transfer from bacterial sources. One potential case of horizontal gene transfer in A. gossypii and 10 potential cases in S. cerevisiae were identified, of which two were investigated further. One gene, encoding the enzyme dihydroorotate dehydrogenase (DHOD), is potentially a case of horizontal gene transfer, as shown by sequencing of this gene from additional bacterial and fungal species to generate sufficient data to construct a well-supported phylogeny. The DHOD-encoding gene found in S. cerevisiae, URA1 (YKL216W), appears to have entered the Saccharomycetaceae after the divergence of the S. cerevisiae lineage from the Candida albicans lineage and possibly since the divergence from the A. gossypii lineage. This gene appears to have come from the Lactobacillales, and following its acquisition the endogenous eukaryotic DHOD gene was lost. It was also shown that the bacterially derived horizontally transferred DHOD is required for anaerobic synthesis of uracil in S. cerevisiae. The other gene discussed in detail is BDS1, an aryl- and alkyl-sulfatase gene of bacterial origin that we have shown allows utilization of sulfate from several organic sources. Among the eukaryotes, this gene is found in S. cerevisiae and Saccharomyces bayanus and appears to derive from the alpha-proteobacteria.