Enabling sum frequency spectroscopy and fluorescence correlation spectroscopy of model cellular membranes

The majority of proteins secreted from cells contain a signal peptide sequence that is required for secretion mediated by the endoplasmic reticulum and Golgi apparatus. However, many proteins lack the essential signal peptide sequence, yet still undergo secretion. Such proteins are known to regulate cell proliferation, differentiation, and migration. Fibroblast growth factor 1 (FGF-1) is one protein which undergoes non-classical protein transport. The role of its interactions with the cellular membrane during non-classical protein transport is not fully understood, although FGF-1 has shown preferential destabilizing effects on artificial membranes composed of acidic phospholipids. In the present work, physiologically relevant model membrane systems have been developed and characterized in order to investigate the role of phospholipid:FGF-1 interactions in translocation of the protein across the membrane. In addition, a confocal z-scan fluorescence correlation spectrometer (z-scan FCS) and a sum frequency spectrometer (SFS) have been assembled, and temperature controlled liquid sample holders have been designed and fabricated. Z-scan FCS and SFS have been employed to characterize the model membrane systems and have been shown to be suitable tools for elucidating the role of specific phospholipid:FGF-1 interactions in transmembrane translocation.