title: Ionic surfactants-Glossoscolex paulistus hemoglobin interactions: Characterization of species in the solution.
abstract: Glossoscolex paulistus hemoglobin (HbGp) is an oligomeric multisubunit protein with molecular mass of 3600kDa. In the current study, the interaction of sodium dodecyl sulfate (SDS) and cetyl trimethylammonium chloride (CTAC) surfactants with the monomer d and the whole oxy-HbGp, at pH 7.0, was investigated. For pure monomer d solution, SDS promotes the dimerization of subunit d, and the monomeric and dimeric forms have sedimentation coefficient values, s20,w, around 2.1-2.4 S and 2.9-3.2 S, respectively. Analytical ultracentrifugation (AUC) and isothermal titration calorimetry (ITC) data suggest that up to 26 DS-anions are bound to the monomer. In the presence of CTAC, only the monomeric form is observed in solution for subunit d. For the oxy-HbGp, SDS induces the dissociation into smaller subunits, such as, monomer d, trimer abc, and tetramer abcd, and unfolding without promoting the protein aggregation. On the other hand, lower CTAC concentration promotes protein aggregation, mainly of trimer, while higher concentration induces the unfolding of dissociated species. Our study provides strong evidence that surfactant effects upon the HbGp-subunits are different, and depend on the surfactant: protein concentration ratio and the charges of surfactant headgroups.
authors.affiliation: Instituto de Química de São Carlos, Universidade de São Paulo, Brazil; Faculdade de Química, Universidade Federal do Sul e Sudeste do Pará, Brazil. Electronic address: adrianocarbureto@gmail.com.
authors.forename: Francisco A O
authors.initials: FA
authors.lastname: Carvalho
authors.affiliation: Instituto de Química de São Carlos, Universidade de São Paulo, Brazil.
authors.forename: Fernanda R
authors.initials: FR
authors.lastname: Alves
authors.affiliation: Instituto de Química de São Carlos, Universidade de São Paulo, Brazil.
authors.forename: Marcel
authors.initials: M
authors.lastname: Tabak
mesh_terms: D000818:Animals; D019540:Area Under Curve; D008725:Bis-Trimethylammonium Compounds / Q000378:metabolism; D002151:Calorimetry; D000067493:Dynamic Light Scattering; D006454:Hemoglobins / Q000378:metabolism*; D057446:Hydrodynamics; D007477:Ions; D008958:Models, Molecular; D009835:Oligochaeta / Q000378:metabolism*; D011485:Protein Binding; D012967:Sodium Dodecyl Sulfate / Q000378:metabolism; D012996:Solutions; D013501:Surface-Active Agents / Q000378:metabolism*; D014461:Ultracentrifugation
chemical_list: D008725:Bis-Trimethylammonium Compounds; D006454:Hemoglobins; D007477:Ions; D012996:Solutions; D013501:Surface-Active Agents; C525618:cethyltrimethylammonium chloride; D012967:Sodium Dodecyl Sulfate
keywords: Glossoscolex paulistus hemoglobin; Surfactants; Unfolding process