title: Spectroscopic probing of the microenvironment in a protein-surfactant assembly.
abstract: The effect of the anionic surfactant sodium dodecyl sulfate (SDS) on the protein human serum albumin (HSA) was studied using steady-state spectroscopy, time-resolved measurements, and circular dichroism spectroscopy. The binding of SDS to the domain IIA of HSA, housing the single tryptophan amino acid residue (Trp214), was monitored, and it was found that this addition of the surfactant takes place in a sequential manner depending upon the concentration of the added surfactant. Both fluorescence intensity and lifetimes of HSA decreased with the increasing concentration of SDS, and the surfactant molecules serve the role of a quencher for the fluorescence of Trp214. Circular dichroism data also support the structural changes induced by SDS. The 17 disulfide bridges present in HSA provide the necessary structural rigidity to the protein. Stern-Volmer plots and thermodynamic parameters have been used to characterize the sequential binding of SDS to HSA, and these parameters not only confirm that the binding is spontaneous in nature but also is quite strong, depending on the concentration of the added surfactant.
authors.affiliation: Department of Chemical Sciences, Indian Institute of Science Education and Research Bhopal, ITI Campus (Gas Rahat) Building, Govindpura, Bhopal 462 023, Madhya Pradesh, India.
authors.forename: Uttam
authors.initials: U
authors.lastname: Anand
authors.forename: Chandrima
authors.initials: C
authors.lastname: Jash
authors.forename: Saptarshi
authors.initials: S
authors.lastname: Mukherjee
mesh_terms: D002942:Circular Dichroism; D006801:Humans; D012709:Serum Albumin / Q000737:chemistry*; D012967:Sodium Dodecyl Sulfate / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet; D013501:Surface-Active Agents / Q000737:chemistry*; D013997:Time Factors
chemical_list: D012709:Serum Albumin; D013501:Surface-Active Agents; D012967:Sodium Dodecyl Sulfate