title: Infrared reflection-absorption spectroscopy and polarization-modulated infrared reflection-absorption spectroscopy studies of the aequorin langmuir monolayer.
abstract: The Langmuir monolayer of aequorin and apoaequorin was studied by infrared reflection-absorption spectroscopy (IRRAS) and polarization-modulated IRRAS techniques. The alpha-helices in the aequorin Langmuir monolayer were parallel to the air-water interface at zero surface pressure. When the surface pressure increased to 15 mN.(m-1), the alpha-helices became tilted and the turns became parallel to the air-water interface. As for apoaequorin, the alpha-helices were also parallel to the air-water interface at 0 mN.m(-1). However, the alpha-helix became tilted and the turns became parallel to the air-water interface quickly at 5 mN.m(-1). With further compression of the apoaequorin Langmuir monolayer, the orientation remained the same. The different behaviors of aequorin and apoaequorin at the air-water interface were explained by the fact that aequorin formed dimers at the air-water interface but apoaequorin was a monomer. It is more difficult for a dimer to be tilted by the compression of the Langmuir monolayer.
authors.affiliation: Department of Chemistry, University of Miami, Coral Gables, Florida 33146, USA.
authors.forename: Chengshan
authors.initials: C
authors.lastname: Wang
authors.forename: Miodrag
authors.initials: M
authors.lastname: Micic
authors.forename: Mark
authors.initials: M
authors.lastname: Ensor
authors.forename: Sylvia
authors.initials: S
authors.lastname: Daunert
authors.forename: Roger M
authors.initials: RM
authors.lastname: Leblanc
mesh_terms: D000331:Aequorin / Q000737:chemistry*; D000388:Air; D008567:Membranes, Artificial; D011312:Pressure; D017433:Protein Structure, Secondary; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods; D013499:Surface Properties; D014867:Water / Q000737:chemistry
chemical_list: D008567:Membranes, Artificial; D014867:Water; D000331:Aequorin