Molecular Biophysics Program
Molecular Cell Biology Program
|Dr. Carl Frieden, Dr. Qin Shu, Dr. Tridib Mondal, Dr. Sudha Cowsik, Berevan Baban, Sergio Molina, Dr. Linda Kurz and Dr. George Drysdale.|
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|Biochem 5325 - Lectures notes|
ApoE proteins and Alzheimer's DiseaseApolipoproteins are essential for lipid and cholesterol transport and metabolism. ApoE4 is one of a family of three apoE proteins. While there are several genetic risk factors for late-onset AD (onset after age 60), the original observation made in 1993 that the ε4 allele is a genetic risk factor still holds. In fact. apoE4 is the major risk factor for Alzheimer's disease (AD). It is now known that the ε4 allele of apoE increases risk ~3-fold when present in 1 copy and ~12-fold when present in 2 copies relative to the ε3 allele. The three common isoforms of apoE, a protein of 299 amino acids, differ only in two amino acids at positions 112 and 158. We are examining how these single amino acid changes can give rise to functional differences.
Amyloid beta, Aβ, is a small peptide associated with plaques in those who have Alzheimer's Disease. Genetic, biochemical, and animal model studies strongly suggest that apoE4 is likely to influence Alzheimer's Disease pathogenesis via effects on the metabolism of the 38-43 amino acid amyloid-β (Aβ) peptide.
We are studying the molecular properties of the interaction of apoE isoforms with lipids and with Aβ using biophysical techniques.
Curli proteins. Bacterial communities, called biofilms, are important in various types of infections, including urinary tract infections (UTIs), chronic skin wounds, otitis media and lung infections in cystic fibrosis patients. For E. coli and other Enterobacteriaceae biofilms, adhesive amyloid fibers called curli can be a major proteinaceous constituent of the extracellular matrix. Curli promote biotic and abiotic surface colonization, stabilize cell-cell contacts allowing cell aggregation and thickening of the biofilm layer, and confer resistance to the biofilm against environmental stresses and biocides. The structural subunits of curli amyloid fibers are CsgA (major component) and CsgB (minor component), CsgE and CsgF which may serve a chaperone function and CsgG, a lipoprotein that localizes to the outer membrane as an oligomeric pore structure and is required for the export of curli subunits to the cell surface. Both CsgA and CsgB are intrinsically disordered proteins (IDPs). In vitro, CsgA and CsgB can self-associate to form high molecular weight aggregates/fibrils. We are studying the properties of the curli subunits and their mechanism of aggregation.
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Protein folding, protein dynamics, protein structure/function
relationships, protein-protein interactions and polymerization/aggregation
mechanisms are projects that we have studied in this laboratory.
Protein FoldingThe long term goal of the protein folding studies was to understand the nature of the unfolded and intermediate structures on the unfolding and refolding pathways, including the role of proteins that assist folding (called chaperonins). The work uses site-directed mutagenesis and techniques such as 19F and proton NMR, circular dichroism, fluorescence measurements and x-ray crystallography. Current studies include work with the apoE family of proteins, with the role of proline in protein folding and with intrinsically disordered proteins such as amyloid beta and the bacterial protein CsgA. Many of the studies involved incorporating fluorine labeled amino acids into the protein and then examining the NMR spectrum. We use stopped flow methods in conjunction with a fluorine cryoprobe for these measurements. From data collected in current and past projects we have a large database of fluorine chemical shifts in proteins. These shifts are sensitive to low concentrations of denaturant, to temperature and to pH. A website for fluorine chemical shifts has been established at http://biochem.wustl.edu/~bmbnmr/Fluorine.html.
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Dr. Carl Frieden
Department of Biochemistry and Molecular Biophysics, Box 8231
Washington University School of Medicine
660 South Euclid
St. Louis, MO 63110 (USA)
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