text: A large research effort involves approaches to know whether proteins have binding sites which are specific for particular lipids and whether the protein–lipid complexes can be considered to be long-lived, on the order of the time required for the turnover a typical enzyme, that is 10 sec. This is now known through the use of H-NMR, ESR, and fluorescent methods.
  There are two approaches used to measure the relative affinity of lipids binding to specific membrane proteins. These involve the use of lipid analogues in reconstituted phospholipid vesicles containing the protein of interest:
  1) Spin-labeled phospholipids are motionally restricted when they are adjacent to membrane proteins. The result is a component in the ESR spectrum which is broadened. The experimental spectrum can be analyzed as the sum of the two components, a rapidly tumbling species in the "bulk" lipid phase with a sharp spectrum, and a motionally restricted component adjacent to the protein. Membrane protein denaturation causes further broadening of ESR spin label spectrum and throws more light on membrane lipid-proteins interactions 
  2) Spin-labeled and brominated lipid derivatives are able to quench the intrinsic tryptophan fluorescence from membrane proteins. The efficiency of quenching depends on the distance between the lipid derivative and the fluorescent tryptophans.