Neal Lab
Multivariate Optical Spectroscopy of
Biomolecular Assemblies in Complex Fluids
The ultimate goal of this work is the application of multivariate measurements to the investigation of dynamic interactions in biomolecular assemblies. We’ve used multivariate energy transfer measurements to study lipid mixing during bicelle formation and multivariate decay measurements to resolve differentially bound protein substrates and distinguish binding sites. Currently we are focusing on the interaction mechanisms of cell penetrating peptides (CPPs) and lipid bilayers. CPPs are short amino acid sequences that have been observed to quickly and easily penetrate cell membranes, implying that they are ideal transport systems for drug delivery. However, recent work has shown that even mild cell fixation conditions redistribute CPPs, undermining the hypothesis that CPPs enter cells by direct permeation. There are three proposed models of CPP cell penetration: direct permeation; endocytosis and reverse micelle formation. These models may occur exclusively or in combination with one another. We will use correlation spectroscopy to study the relationship between CPP structure and penetration mechanism by labeling CPPs with microenvironment probes that will change as the peptide interacts with solvent and model cell walls (giant unilamellar vesicles). Differences in internalization mechanism will be reflected in the sequence of microenviroments encountered by the label as the peptide interacts with the vesicle bilayer. 
