title: Characterisation of molten globule-like state of sheep serum albumin at physiological pH.
abstract: Sheep serum albumin (SSA) is a 583 amino acid residues long multidomain monomeric protein which is rich in cysteine and low in tryptophan content. The serum albumins (from human, bovine and sheep) play a vital role among all proteins investigated until now, as they are the most copious circulatory proteins. We have purified SSA from sheep kidneys by a simple and efficient two-step purification procedure. Further, we have studied urea-induced denaturation of SSA by monitoring changes in the difference absorption coefficient at 287nm (Δε287), intrinsic fluorescence emission intensity at 347nm (F347) and mean residue ellipticity at 222nm ([θ]222) at pH 7.4 and 25°C. The coincidence of denaturation curves of these optical properties suggests that urea-induced denaturation is a bi-phasic process (native (N) state↔intermediate (X) state↔denatured (D) state) with a stable intermediate populated around 4.2-4.7M urea. The intermediate (X) state was further characterized by the far-UV and near-UV CD, dynamic light scattering (DLS) and fluorescence using 1-anilinonaphthalene-8-sulfonic acid (ANS) binding method. All denaturation curves were analyzed for Gibbs free energy changes associated with the equilibria, N state↔X state and X state↔D state in the absence of urea.
authors.affiliation: Centre for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, New Delhi 110025, India.
authors.forename: Mohammad Aasif
authors.initials: MA
authors.lastname: Dar
authors.affiliation: Centre for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, New Delhi 110025, India.
authors.lastname: Wahiduzzaman
authors.affiliation: Centre for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, New Delhi 110025, India.
authors.forename: Md Anzarul
authors.initials: MA
authors.lastname: Haque
authors.affiliation: Centre for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, New Delhi 110025, India. Electronic address: asimulislams@gmail.com.
authors.forename: Asimul
authors.initials: A
authors.lastname: Islam
authors.affiliation: Centre for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, New Delhi 110025, India.
authors.forename: Md Imtaiyaz
authors.initials: MI
authors.lastname: Hassan
authors.affiliation: Centre for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, New Delhi 110025, India.
authors.forename: Faizan
authors.initials: F
authors.lastname: Ahmad
mesh_terms: D000818:Animals; D002417:Cattle; D002942:Circular Dichroism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D011487:Protein Conformation; D011489:Protein Denaturation; D017510:Protein Folding; D012709:Serum Albumin / Q000737:chemistry* / Q000302:isolation & purification* / Q000378:metabolism; D012756:Sheep / Q000097:blood*; D013696:Temperature; D013816:Thermodynamics
chemical_list: D012709:Serum Albumin
keywords: Molten globule state; Protein folding; Protein stability; Sheep serum albumin; Urea-induced denaturation