Our goal is to understand at the molecular level the mechanism and the dynamics of folding, insertion and dimerization of transmembrane protein fragments in lipidic membranes. This will be achieved by combining chemically engineered membrane peptides, whose folding/unfolding can be triggered by light, with spectroscopy (IR, CD, Raman, UV/vis, and fluorescence) and molecular dynamics and spectral simulations.
We aim to understand how amphipathic peptides and amphipathic regions of proteins interact with lipid membranes and increase their permeability. For that, we use a range of biophysical methods, including spectroscopy and microscopy at different scales, which allow us to characterize the peptide structure and peptide-membrane binding, to observe the formation of pores and to follow membrane leakage. Most valuable information is obtained through the study of the leakage kinetics in single giant vesicles, which is then analyzed using theoretical models and statistics. The systems of work include the well known peptide toxin melittin, active fragments from the apoptotic proteins Bax and Bak, and new peptides redesigned from the natural sequences of the former.
Melittin pores in supported lipid monolayers as viewed by tapping-mode AFM
We are developing the use of biological buffers as pH-sensitive vibrational probes, aiming to solve some of the limiations of traditional pH-probes based on chromophores and fluorophores. The pH-vibrational probes will be used to track with high fidelity protonation changes during the functional mechanism of membrane proteins by time-resolved vibrational spectroscopies, as well as to obtain pH maps of gigant unilamellar vesicles with vibrational microscopies.
Lorenz-Fonfria, Saita, Lazarova, Schlesinger & Heberle
Proc Natl Acad Sci U S A