Using infrared spectroscopy of a nitrile labeled phenylalanine and tryptophan fluorescence to probe the α-MSH peptide's side-chain interactions with a micelle model membrane

The interactions of α-MSH (Ac-SYSMEHFRWGKPV-NH₂) side-chains were biophysically characterized with a micelle model membrane and in model intracellular bacterial conditions using infrared (IR) spectroscopy of a nitrile labeled α-MSH analogue, circular dichroism (CD), and tryptophan fluorescence. Local changes detected by the tryptophan and a nitrile-labeled phenylalanine using fluorescence and infrared spectroscopies, respectively, suggest that the Trp9 side-chain in the conserved core (HisPheArgTrp) of α-MSH is buried in an SDS micellar environment, while Phe(CN)7 does not appear to be buried.