Fluorescence, phospholipid exchange

Somerharju et al. (1981) developed an assay for phospholipid exchange activity with the fluorescent phospholipid derivative, l-acyl-2-parinaroyl-phosphatidylcholine. When vesicles of this fluorescent phospholipid are... 

One role of the class Y amphipathic helices found in apoA-IV and apoA-I appears to be to serve as low-affinity lipid-associating domains. The snorkel hypothesis predicts that this class of amphipathic helix would not penetrate as deeply into phospholipid surfaces as would class A and thus would have lower lipid affinity. This prediction is supported by experimental evidence (based on Trp fluorescence blue shifts, ease of Trp fluorescence quenching, and liposomal leakage) that apoA-IV sits higher in a phospholipid monolayer than do the other exchangeable apolipoproteins that contain class A amphipathic helices (Weinberg and Jordan, 1990). 

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