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Proteins are involved in virtually every biological process. To function, these chains must fold into the unique three-dimensional structure that is characteristic for each protein. The research in my group aims to increase the understanding of the molecular recognition process by which proteins fold, and what factors determine their stability. The major focus is on selected cofactor-binding proteins, for example azurin (copper cofactor) and flavodoxin (organic cofactor). Folding speeds, as well as pathways, for such proteins may be affected by the presence of the cofactor. A range of equilibrium and time-resolved (stopped-flow) spectroscopic techniques are used to characterize the folding reactions. In addition, with a novel method, where electron-transfer (initiated by photochemistry or electrochemistry) is used as the trigger, we can study very rapid folding events (on the microsecond time scale).

Proteins are involved in virtually every biological process. Here is an example of one such molecule.

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1. Biophysical Studies of Protein Folding: We want to learn more about the complex molecular recognition process by which proteins fold and what factors determine their stability. Our research focuses mostly on, but is not limited to, cofactor-binding proteins with pleated-sheet structure. The pleated-sheet motif is very important from a medical viewpoint; amyloid diseases such as Alzheimer's are correlated with aggregated such proteins. Cofactor-binding proteins are essential components of living cells involved in electron-transfer, energy pro duction and oxygen transport, for example. The folding of a cofactor-binding protein into its native structure includes, in addition to folding of the peptide chain, the correct positioning of the ligands to the cofactor. Some proteins coordinate metal io ns others large, rigid cofactors such as iron porphyrins. The cofactor could play a key role in the folding of cofactor-binding proteins; it may act as a nucleus that directs the folding. We combine biophysical, chemical and biochemical experimental approaches in our studies. The main experimental tools are circular dichroism, absorption and fluorescence spectroscopy. To reveal time-resolved data we use a novel electron-transfer trigger ed method, applicable to redox-active proteins, and traditional stopped-flow mixing. We currently study the following proteins: Azurin - A blue copper protein with eight strands wrapped in a beta-barrel. In folded azurin, copper is directly coordinated to side-chains of amino acids in the polypeptide. The copper ion binds to unfolded reduced azurin, coordinatin g three ligands. Cytochrome f - Cytochrome f is involved in photosynthetic electron transport. The protein contains two globular domains, both with pleated-sheet structure. The fold is different from that of other c-type cytochromes which all have helical structures. Flavodoxin - Flavodoxin possesses an organic cofactor, flavin mononucleotide (FMN), non-covalently bound to the protein. Flavodoxins have a very interesting - and common - fold: a central five-stranded pleated-sheet structure flank ed by four helices. Ferredoxin – Ferredoxins have iron-sulfur clusters as cofactors. We study various such proteins from thermophilic organisms to learn more about factors governing thermostability as well as the role of these cofactors. Chaperonin – Chaperonin proteins GroEL and GroES help other proteins to fold. We are trying to figure out how the GroES heptamer itself forms its native, functional ring-structure from seven unfolded monomers. 2. Other Research Projects: Membrane Penetration of Genetic Drugs Drugs directed to our genes are the next generation of medicine. The major hurdle with this approach is the poor cellular uptake of these compounds. Their increased size, as compared to most of today’s small-molecule drugs, drastically decr ease the possibilities for passive diffusion across plasma membranes. We attack the cell-uptake problem with genetic drugs by designing intelligent drug-carrier constructs and test them in cell models based on liposomes. Lyme-Disease Diagnostics Lyme disease is a severe disease caused by infectious tick. We are investigating diagnostic properties of peptides derived from an invariable region of the spirochete surface protein VlsE that is immuno-dominant. In addition, we plan to ful ly characterize the full-length VlsE protein.