RESEARCH
RESEARCH
One topic of particular interest is related to the fascinating range of interactions that govern the functioning of biomembranes, their components and proteins interacting with them. This is a very dynamic and biologically important environment, where structural biology and biophysical understanding go hand in hand. We aim to leverage some of the particular capabilities and strong points of biological SSNMR to enhance our understanding of these processes. This will include MAS SSNMR studies on selected proteins of particular interest, as well as more basic experiments aimed at the underlying physics.
Below I describe some of my previous research on related topics:
Many
integral membrane proteins
have a membrane spanning region that is
characterized by the presence of predominantly hydrophobic residues,
but is flanked by specific characteristic residues. This is illustrated
below for
selected membrane proteins crystal
structures, where we see a
clear pattern of distribution of
the tryptophan 
and tyrosine
residues near the membrane interface,
where they appear to act as interfacial
anchors.
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The helices that constitute the membrane spanning domain of many of these proteins often display a specific tilt relative to the membrane. This can be functionally important, and has helix tilting has been found to be involved in the functioning of various membrane proteins. In addition, tilting is one of the ways in which the hydrophic mismatch between a protein and surrounding lipids can be adjusted. During my PhD in the lab of Roger Koeppe II, we studied various aspects of protein-lipid interactions in detail, through the use of model transmembrane peptides. (WALP peptides) that feature model a a helical core of hydrophobic amino acids, surrounded by interfacial anchors. Using solid state NMR methods using macroscopically aligned membranes, we were able to study both their tilt and the behavior of their Trp interfacial anchors, while in a proper, hydrated lipid bilayer environment. The use of 2H NMR on transmembrane helices containing deuterated Ala [2] residues allowed a direct measurement of their tilt angles, whereas similar measurements where the Trp residues were deuterated provided insights into these residues.
Additional measurements on lipid liposomes allowed us to see the remarkable effect of these peptides on the phospholipid phase transitions, as monitored by 31P-NMR. They were found to lead to the increased induction of inverted, non-bilayer structures, which was correlated to the extent of hydrophobic mismatch. Interestingly, the formation of non-bilayer phases is thought to be essential for biological processes that involve membrane fusion and fission.
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WALP19:
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