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Dr. H. Brian Halsall
Curriculum Vitae
Biomolecular Structure and Analysis
Brian Halsall is a Professor of Chemistry and Chairman of the Biochemistry Division. A biochemist, he has had broad research interests in analytical and physical biochemistry since his PhD work with Peter Spragg on analytical ultracentrifugation and its application to studying glycoprotein aggregation. His postdoctoral studies with Verne Schumaker at UCLA explored the analytical aspects of the zonal ultracentrifuge, and these he continued while on the staff of the MAN program, directed by Norman Anderson, at Oak Ridge National Laboratory. He joined the Chemistry Department of the University of Cincinnati in 1974 where he has revisited glycoprotein biochemistry and moved into high sensitivity sensors.
Research Areas
Glycoproteins
Most of the vast number of proteins in human serum are glycoproteins. Glycoproteins are among the largest group of macromolecules in nature, and in many respects the least is known about them. This is particularly true concerning the function(s) of the glycan chains and the relationships that may exist between the protein core and the glycan chains covalently attached to it. We have chosen orosomucoid ( a 1 -acid glycoprotein) as a model protein to explore these relationships using such methods as fluorescence spectroscopy, mass spectrometry, and differential scanning calorimetry, and macromolecular probes such as monoclonal antibodies. In the acute phase of inflammatory disease, the glycan chain composition of orosomucoid changes. Certain diseases, particularly cancer, also result in dramatic glycan changes from complex to hybrid structures. Thus, we have developed methodology that permits the investigation of disease/glycan chain correlations at the level of the individual glycosylation site. Using HPLC peptide and glycan mapping and mass spectrometry, we are also able to resolve glycopeptides that arise from both of the genes that code for orosomucoid, allowing us to examine glycosylation differences in disease in each gene product.
A further feature of orosomucoid is its ability to sequester small, lipophilic molecules such as platelet activating factor and a host of important therapeutic drugs. Our interest here is to define the details of the binding site, and to relate this to a model of the overall three dimensional structure of the molecule. To do this we are using topographic mapping with monoclonal antibodies together with ligand affinity labeling and titration microcalorimetry.
Sensing and Immunoassay
Radiolabels are being replaced rapidly as the marker of choice in the great majority of immunoassays. The most sensitive replacements include some form of amplification, of which the most common has been enzymatic. One of the approaches we have taken has been to couple the enzymatic amplification of the analyte concentration to
detection of the enzyme product by electrochemical methods. Most successful have been amperometric methods used in conjunction with flow injection analysis, HPLC or with rotating disk electrodes. With detection limits below 3,500 molecules, we are now focusing on lowering the detection limit further for special applications such as CBW detection, and on systems requiring a much smaller (less than 10 microliter) sample size for application in, for example, pediatrics, where small samples are desirable or mandatory. Active areas include multianalyte assays, developing substrates with well developed redox properties, minimizing interactions between biological and non-biological surfaces, developing miniature, self contained immunosensors for remote or personal sensing, and developing systems that can measure analytes in the presence of blood replacements.
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