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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

Interaction of Cationic Dodecyl-trimethyl-Ammonium Bromide with Oxy-HbGp by Isothermal Titration and Differential Scanning Calorimetric Studies: Effect of Proximity of Isoelectric Point

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Author(s):
Alves, Fernanda Rosa [1] ; Carvalho, Francisco Adriano O. [1] ; Carvalho, Jose Wilson P. [2] ; Tabak, Marcel [1]
Total Authors: 4
Affiliation:
[1] Univ Sao Paulo, Inst Quim Sao Carlos, Sao Carlos, SP - Brazil
[2] Univ Estado Mato Grosso, Barra Do Bugres, MT - Brazil
Total Affiliations: 2
Document type: Journal article
Source: Biopolymers; v. 105, n. 4, p. 199-211, APR 2016.
Web of Science Citations: 1
Abstract

In this work, isothermal titration and differential scanning calorimetric methods, in combination with pyrene fluorescence emission and dynamic light scattering have been used to investigate the interaction of dodecyltrimethylammonium bromide (DTAB) with the giant extracellular Glossoscolex paulistus hemoglobin (HbGp) in the oxy-form, at pH values around the isoelectric point (pI approximate to 5.5). Our ITC results have shown that the interaction of DTAB with the hemoglobin is more intense at pH 7.0, with a smaller cac (critical aggregation concentration) value. The increase of protein concentration does not influence the cac value of the interaction, at both pH values. Therefore, the beginning of the DTAB-oxy-HbGp premicellar aggregates formation, in the cac region, is not affected by the increase of protein concentration. HSDSC studies show higher T-m values at pH 5.0, in the absence and presence of DTAB, when compared with pH 7.0. Furthermore, at pH 7.0, an aggregation process is observed with DTAB in the range from 0.75 to 1.5 mmol/L, noticed by the exothermic peak, and similar to that observed for pure oxy-HbGp, at pH 5.0, and in the presence of DTAB. DLS melting curves show a decrease on the hemoglobin thermal stability for the oxy-HbGp-DTAB mixtures and formation of larger aggregates, at pH 7.0. Our present data, together with previous results, support the observation that the protein structural changes, at pH 7.0, occur at smaller DTAB concentrations, as compared with pH 5.0, due to the acidic pI of protein that favors the oxy-HbGp-cationic surfactant interaction at neutral pH. (C) 2015 Wiley Periodicals, Inc. (AU)

FAPESP's process: 13/09829-8 - Biophysical and structural studies of extracellular hemoglobin of Glossoscolex paulistus, and its monomer d and dodecamer (abcd)3 subunits.
Grantee:Francisco Adriano de Oliveira Carvalho
Support type: Scholarships in Brazil - Post-Doctorate