title: pH induced structural modulation and interfacial activity of hemoglobin at the air/water interface.
abstract: In this Article, we report the surface activity of the human globular blood protein, hemoglobin (Hb), at the air/water interface. The Langmuir-Blodgett technique is used for monolayer characterization. The adsorption growth-kinetics study shows that the adsorption process at the air/water interface is involved with two mechanisms: one diffusion with adsorption and the other rearrangement with unfolding. The kinetics is found to be dependent on pH and protein concentration in the subphase. The CD and FTIR studies suggest larger intermolecular aggregate and beta-sheet formation in the film lifted from the air/acidic water subphase. In alkaline pH and in isoelectric pH (6.8), not much variation is observed. The FE-SEM images support this observation. The acidic pH induced such conformational changes, and aggregation is explained with the argument of alpha-helix to beta-sheet conversion as well as the competition between protonation and deprotonation of the aromatic-amino acid residues at the air/water interface.
authors.affiliation: Department of Spectroscopy, Indian Association for the Cultivation of Science, Jadavpur, Kolkata-700032, India.
authors.forename: Mrityunjoy
authors.initials: M
authors.lastname: Mahato
authors.forename: Prabir
authors.initials: P
authors.lastname: Pal
authors.forename: Tapanendu
authors.initials: T
authors.lastname: Kamilya
authors.forename: Ratan
authors.initials: R
authors.lastname: Sarkar
authors.forename: G B
authors.initials: GB
authors.lastname: Talapatra
mesh_terms: D000327:Adsorption; D000388:Air; D002942:Circular Dichroism; D006454:Hemoglobins / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D017433:Protein Structure, Secondary; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties; D014867:Water / Q000737:chemistry*
chemical_list: D006454:Hemoglobins; D014867:Water