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Thermal and kinetic stability of the giant extracellular hemoglobin of Glossoscolex paulistus (HbGp): effects of surfactants, salts, urea, iron heme oxidation state and pH.

Grant number: 13/09349-6
Support type:Scholarships in Brazil - Post-Doctorate
Effective date (Start): October 01, 2013
Effective date (End): March 31, 2014
Field of knowledge:Biological Sciences - Biophysics - Molecular Biophysics
Principal researcher:Marcel Tabak
Grantee:José Wilson Pires Carvalho
Home Institution: Instituto de Química de São Carlos (IQSC). Universidade de São Paulo (USP). São Carlos , SP, Brazil


The extracellular hemoglobin of Glossoscolex paulistus (HbGp) has an extraordinary molecular mass of 3.6 MDa, with its oligomeric structure arranged as two superposed hexagonal discs forming a "bracelet". The quaternary structure of HbGp has 144 globin chains and 36 non-globin chains (named linkers). The HbGp dissociates in alkaline pH and in the presence of high surfactant concentrations, at 25 oC. Recent studies on the thermal stability of HbGp at different pH values, in the absence and presence of SDS and CTAC, using CD, SAXS and DLS techniques has provided interesting information about denaturation and aggregation processes for HbGp. However, structural changes, iron oxidation and the kinetics of aggregation processes for HbGp, in the presence and absence of surfactant, remain practically unknown. In this context, the present postdoctoral project proposes a further investigation of the kinetics of aggregation for oxy- and cyanomet-HbGp, in the absence and presence of SDS and CTAC, at different temperatures, by DLS. We also propose the use of new techniques, such as FTIR and fluorescence to investigate structural changes during the thermal denaturation of oxy- and cyanomet-HbGp, in the absence and presence of surfactant at acidic and neutral pH. The investigation of the dicátion salts, such as MgCl2 and CaCl2, and the monocation salt, NaCl, effects on the thermal stability of HbGp at pH 7.0, monitored by SAXS is also proposed. The electroanalytical technique of cyclic voltammetry to monitor the process of denaturation of oxy- and cyanomet-HbGp, induced by guanidine chloride and urea at pH 7.0, at 25 oC is also our focus. The use of these different techniques will contribute to improve the knowledge about the oligomeric dissociation, denaturation and aggregation phenomena for this giant hemoglobin, which has been studied by our group of Molecular Biophysics, at Institute of Chemistry of São Carlos (IQSC) for several years.

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Scientific publications
(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)
CARVALHO, FRANCISCO A. O.; ALVES, FERNANDA R.; CARVALHO, JOSE W. P.; TABAK, MARCEL. Guanidine hydrochloride and urea effects upon thermal stability of Glossoscolex paulistus hemoglobin (HbGp). International Journal of Biological Macromolecules, v. 74, p. 18-28, . (13/09829-8, 11/09863-6, 13/09349-6)
ALVES, FERNANDA ROSA; CARVALHO, FRANCISCO ADRIANO O.; CARVALHO, JOSE WILSON P.; TABAK, MARCEL. Glossoscolex paulistus Extracellular Hemoglobin (HbGp) Oligomeric Dissociation upon Interaction with Sodium Dodecyl Sulfate: Isothermal Titration Calorimetry (ITC). Biopolymers, v. 101, n. 10, p. 1065-1076, . (13/09829-8, 11/09863-6, 13/09349-6)
CARVALHO, JOSE WILSON P.; CARVALHO, FRANCISCO ADRIANO O.; BATISTA, TATIANA; SANTIAGO, PATRICIA S.; TABAK, MARCEL. Cetyltrimethylammonium chloride (CTAC) effect on the thermal stability of oxy-HbGp: Dynamic light scattering (DLS) and small angle X-ray scattering (SAXS) studies. COLLOIDS AND SURFACES B-BIOINTERFACES, v. 118, p. 14-24, . (13/09349-6)

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