Laser Raman spectroscopy of lipid-protein systems. Differences in the effect of intrinsic and extrinsic proteins on the phosphatidylcholine Raman spectrum.

Laser Raman spectroscopy is used to examine the interactions of intrinsic and extrinsic proteins with the lipid layer structure. The interactions of cytochrome c and cytochrome c oxidase with lipids have been well established by others using a variety of techniques. Cytochrome c is thought to act as an extrinsic membrane protein while cytochrome c oxidase is thought to act as an intrinsic membrane protein. The lipid-cytochrome c and lipid cytochrome c oxidase systems are used to assist in interpreting the spectral changes due to extrinsic and intrinsic protein interactions. The two types of proteins examined produced differential changes in the lipid hydrocarbon C-H stretch Raman modes for both dimyristoyl and dipalmitoyl phosphatidylcholine. The plasma proteins albumin and fibrinogen were also found to differentially affect the lipid hydrocarbon C-H stretch Raman nodes. These proteins appear to interact with lipids in an extrinsic manner different from that of cytochrome c.