title: Stepwise unfolding of bovine and human serum albumin by an anionic surfactant: an investigation using the proton transfer probe norharmane.
abstract: Interactions of the anionic surfactant sodium dodecyl sulfate (SDS) with the transport proteins bovine serum albumin (BSA) and human serum albumin (HSA) have been divulged using an external photoinduced proton transfer probe, norharmane (NHM). Steady-state fluorometry, time-resolved measurements, micropolarity analysis, circular dichroism (CD), and isothermal titration calorimetry (ITC) have been exploited for the study. With the gradual addition of SDS to the probe-bound proteins, the fluorometric responses of the different prototropic species of NHM exhibit an opposite pattern as to that observed while NHM binds to the proteins. The study reveals a sequential unfolding of the serum proteins with the gradual addition of SDS. ITC measures the heat changes associated with each step of the unfolding. ITC experiments, carried out at two different pH's, elucidate the nature of interaction between SDS and the two serum proteins. At a very high concentration of SDS, the external probe (NHM) is found to be dislodged from the protein environments to bind to the SDS micellar medium.
authors.affiliation: Department of Chemistry, Jadavpur University , Kolkata 700 032, India.
authors.forename: Saptarshi
authors.initials: S
authors.lastname: Ghosh
authors.forename: Satrajit
authors.initials: S
authors.lastname: Chakrabarty
authors.forename: Debipreeta
authors.initials: D
authors.lastname: Bhowmik
authors.forename: Gopinatha Suresh
authors.initials: GS
authors.lastname: Kumar
authors.forename: Nitin
authors.initials: N
authors.lastname: Chattopadhyay
mesh_terms: D065966:Absorption, Physicochemical; D000818:Animals; D002243:Carbolines / Q000737:chemistry*; D002417:Cattle; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008958:Models, Molecular; D017433:Protein Structure, Secondary; D058767:Protein Unfolding / Q000187:drug effects*; D011522:Protons; D012710:Serum Albumin, Bovine / Q000737:chemistry*; D012967:Sodium Dodecyl Sulfate / Q000737:chemistry*; D013501:Surface-Active Agents / Q000494:pharmacology*
chemical_list: D002243:Carbolines; D011522:Protons; D013501:Surface-Active Agents; D012710:Serum Albumin, Bovine; D012967:Sodium Dodecyl Sulfate; C010262:norharman