title: Surface properties of "jellyfish": Langmuir monolayer and Langmuir-Blodgett film studies of recombinant aequorin.
abstract: In this paper, we studied the surface properties of recombinant aequorin at the air-water interface. Using the Langmuir monolayer technique, the surface properties of aequorin were studied, including the surface pressure and surface potential-area isotherms, compression-decompression cycles, and stability on Trizma Base (Tris/HCl) buffer at pH 7.6. The results showed that aequorin formed a stable Langmuir monolayer and the surface pressure-area isotherms were dependent on both pH and ionic strength. At a pH higher or lower than 7.6, the limiting molecular area decreased. The circular dichroism (CD) spectra of aequorin in aqueous solutions explained this result: when the pH was higher than 7.6, the alpha-helix conformation changed to unordered structures, whereas at a pH lower than 7.6, the alpha-helix conformation changed to beta-sheet. The addition of calcium chloride to the Tris/HCl buffer subphase (pH 7.6) caused an increase of the limiting molecular area of the aequorin Langmuir monolayer. The fluorescence spectra of a Langmuir-Blodgett (LB) film of aequorin in the presence of calcium chloride indicated that the aequorin transformed to the apoaequorin.
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; D001059:Apoproteins / Q000737:chemistry; D002021:Buffers; D002122:Calcium Chloride / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D049408:Luminescent Agents / Q000737:chemistry*; D011189:Potassium Chloride / Q000737:chemistry; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet; D013499:Surface Properties; D014867:Water / Q000737:chemistry*
chemical_list: D001059:Apoproteins; D002021:Buffers; D049408:Luminescent Agents; D011994:Recombinant Proteins; C060014:apoaequorin; D014867:Water; D000331:Aequorin; D011189:Potassium Chloride; D002122:Calcium Chloride