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71.
Sophisticated molecular biological research has revealed many virulence attributes in at least four pathogenic fungi, but the future study of fungal virulence requires investigators to distinguish between molecules that directly interact with the host, molecules that regulate these, and molecules that are always required for fungal growth and survival, independent of the host. 相似文献
72.
Recently, it has been demonstrated that Fourier transform infrared spectroscopy (FTIR) detects conformational changes in the glutamate receptor ligand-binding domain that are associated with agonist binding. Combined with flash photolysis, this observation offers the prospect of following conformational changes at individual protein and agonist moieties in parallel and with high temporal resolution. Here, we demonstrate that gamma(alpha-carboxy-2-nitrobenzyl) glutamate (caged glutamate) does not interact with the protein, and that following photolysis with UV light the FTIR difference spectrum indicated changes in the protein tertiary and secondary interactions. These changes were similar to those observed for the protein upon addition of free glutamate. Thus, caged glutamate and its photolysis by-products are inert in this system, whereas the released glutamate exhibits full activity. Difference spectra of caged glutamate and of reaction analogs permitted identification of and correction for FTIR signals arising from the photolytic reaction and confirmed that its products are indeed glutamate and 2-nitrosophenyl glyoxalic acid. 相似文献
73.
Understanding the large-scale structural network formed by neurons is a major challenge in system neuroscience. A detailed connectivity map covering the entire brain would therefore be of great value. Based on diffusion MRI, we propose an efficient methodology to generate large, comprehensive and individual white matter connectional datasets of the living or dead, human or animal brain. This non-invasive tool enables us to study the basic and potentially complex network properties of the entire brain. For two human subjects we find that their individual brain networks have an exponential node degree distribution and that their global organization is in the form of a small world. 相似文献
74.
Andreas Prlić Thomas A Down Eugene Kulesha Robert D Finn Andreas Kähäri Tim JP Hubbard 《BMC bioinformatics》2007,8(1):333
Background
The Distributed Annotation System (DAS) is a network protocol for exchanging biological data. It is frequently used to share annotations of genomes and protein sequence. 相似文献75.
Glycosylation sites and site-specific glycosylation in human Tamm- Horsfall glycoprotein 总被引:4,自引:1,他引:3
The N-glycosylation sites of human Tamm-Horsfall glycoprotein from one
healthy male donor have been characterized, based on an approach using
endoproteinase Glu-C (V-8 protease, Staphylococcus aureus ) digestion and a
combination of chromatographic techniques, automated Edman sequencing, and
fast atom bombardment mass spectrometry. Seven out of the eight potential
N-glycosylation sites, namely, Asn52, Asn56, Asn208, Asn251, Asn298,
Asn372, and Asn489, turned out to be glycosylated, and the potential
glycosylation site at Asn14, being close to the N-terminus, is not used.
The carbohydrate microheterogeneity on three of the glycosylation sites was
studied in more detail by high-pH anion-exchange chromatographic profiling
and 500 MHz1H-NMR spectroscopy. Glycosylation site Asn489 contains mainly
di- and tri-charged oligosaccharides which comprise, among others, the
GalNAc4 S (beta1-4)GlcNAc terminal sequence. Only glycosylation site Asn251
bears oligomannose-type carbohydrate chains ranging from Man5GlcNAc2to
Man8GlcNAc2, in addition to a small amount of complex- type structures.
Profiling of the carbohydrate moieties of Asn208 indicates a large
heterogeneity, similar to that established for native human Tamm-Horsfall
glycoprotein, namely, multiply charged complex-type carbohydrate
structures, terminated by sulfate groups, sialic acid residues, and/or the
Sda-determinant.
相似文献
76.
The gamma-aminobuytric acid(A) (GABA(A)) receptor is a membrane-bound protein that mediates signal transmission between neurons through formation of chloride ion channels. GABA is the activating ligand, which upon binding to the receptor triggers channel opening in the microsecond time domain and reversible desensitization of the receptor in the millisecond time region. We have investigated the channel-opening mechanism for this receptor in rat hippocampal neurons before the protein desensitizes by using a rapid flow method (cell-flow) with a 10 ms time resolution and a laser-pulse photolysis technique with a approximately 30 micros time resolution to determine the rate and equilibrium constants for channel opening and closing. Two different forms of the receptor, namely, a rapidly and a slowly desensitizing form, exist in the rat hippocampal cells and are characterized by their different rates for desensitization. At 250 microM GABA the rate constant for desensitization was 2.3 +/- 0.4 s(-)(1) for the rapidly desensitizing form and 0.4 +/- 0.1 s(-)(1) for the slowly desensitizing form. The dissociation constant of GABA from the site controlling channel opening was 100 +/- 40 microM for the rapidly desensitizing form and 120 +/- 60 microM for the slowly desensitizing form. The rate constants for channel closing did not differ significantly for the two forms, 85 +/- 20 s(-)(1) for the rapidly desensitizing and 100 +/- 60 s(-)(1) for the slowly desensitizing form. However, the channel-opening rate constant differed by a factor of 3, 1840 +/- 160 s(-)(1) for the rapidly desensitizing and 6700 +/- 330 s(-)(1) for the slowly desensitizing form. This difference in the rate constant for channel opening for the two forms, determined by the laser-pulse photolysis technique, is reflected as a shift in the channel-opening equilibrium constant, which is 7 +/- 5 and 20 +/- 15 for the rapidly and slowly desensitizing forms respectively, determined by the cell-flow method. These constants, together with the concentration of GABA and the concentration of receptor sites in the membrane, determine the number of channels that open as a function of GABA concentration, and the rate at which they open and close. These constants play an important role in determining the rate of the transmembrane ion flux and, therefore, the receptor-controlled changes in transmembrane voltage that trigger signal transmission. 相似文献
77.
78.
79.
Marie-Christine Ottet Marie Schaer Leila Cammoun Maude Schneider Martin Debbané Jean-Philippe Thiran Stephan Eliez 《PloS one》2013,8(3)
The 22q11.2 deletion syndrome (22q11DS) is a widely recognized genetic model allowing the study of neuroanatomical biomarkers that underlie the risk for developing schizophrenia. Recent advances in magnetic resonance image analyses enable the examination of structural connectivity integrity, scarcely used in the 22q11DS field. This framework potentially provides evidence for the disconnectivity hypothesis of schizophrenia in this high-risk population. In the present study, we quantify the whole brain white matter connections in 22q11DS using deterministic tractography. Diffusion Tensor Imaging was acquired in 30 affected patients and 30 age- and gender-matched healthy participants. The Human Connectome technique was applied to register white matter streamlines with cortical anatomy. The number of fibers (streamlines) was used as a measure of connectivity for comparison between groups at the global, lobar and regional level. All statistics were corrected for age and gender. Results showed a 10% reduction of the total number of fibers in patients compared to controls. After correcting for this global reduction, preserved connectivity was found within the right frontal and right parietal lobes. The relative increase in the number of fibers was located mainly in the right hemisphere. Conversely, an excessive reduction of connectivity was observed within and between limbic structures. Finally, a disproportionate reduction was shown at the level of fibers connecting the left fronto-temporal regions. We could therefore speculate that the observed disruption to fronto-temporal connectivity in individuals at risk of schizophrenia implies that fronto-temporal disconnectivity, frequently implicated in the pathogenesis of schizophrenia, could precede the onset of symptoms and, as such, constitutes a biomarker of the vulnerability to develop psychosis. On the contrary, connectivity alterations in the limbic lobe play a role in a wide range of psychiatric disorders and therefore seem to be less specific in defining schizophrenia. 相似文献
80.