The characterization and bioelectrocatalytic properties of hemoglobin by direct electrochemistry of DDAB film modified electrodes

Direct electrochemistry of hemoglobin can be performed in acidic and basic aqueous solutions in the pH range 1-13, using stable, electrochemically active films deposited on a didodecyldimethylammonium bromide (DDAB) modified glassy carbon electrode. Films can also be produced on gold, platinum, and transparent semiconductor tin oxide electrodes. Hemoglobin/DDAB films exhibit one, two, and three redox couples when transferred to strong acidic, weak acidic and weak basic, and strong basic aqueous solutions, respectively. These redox couples, and their formal potentials, were found to be pH dependent. An electrochemical quartz crystal microbalance and cyclic voltammetry were used to study the in situ deposition of DDAB on gold disc electrodes and hemoglobin deposition on DDAB film modified electrodes. A hemoglobin/DDAB/GC modified electrode is electrocatalytically reduction active for oxygen and H₂O₂, and electrocatalytically oxidation active for S₂O₄²⁻ through the Fe(III)/Fe(II) redox couple. In the electrocatalytic reduction of S₄O₆²⁻, S₂O₄²⁻, and SO₃²⁻, and the dithio compounds of 2,2′-dithiosalicylic acid and 1,2-dithiolane-3-pentanoic acid, the electrocatalytic current develops from the cathodic peak of the redox couple at a potential of about −0.9 V (from the Fe(II)/Fe(I) redox couple) in neutral and weakly basic aqueous solutions. Hemoglobin/DDAB/GC modified electrodes are electrocatalytically reduction active for trichloroacetic acid in strong acidic buffered aqueous solutions through the Fe(III)/Fe(II) redox couple. However, the electrocatalytic current developed from the cathodic peak of the redox couple at a potential of about −0.9 V (from the Fe(II)/Fe(I) redox couple) in weak acidic and basic aqueous solutions. The electrocatalytic properties were investigated using the rotating ring-disk electrode method.     

复方邻苯二甲醛纳米乳的制备

以肉豆蔻酸异丙酯(IPM)、癸甲溴铵(双十烷基二甲基溴化铵)、1,2-丙二醇和邻苯二甲醛为原料,制备了邻苯二甲醛纳米乳。用透射电镜(TEM)、激光粒度测定仪对其微观形貌进行了表征;通过恒温加速实验考察了其稳定性。结果表明:制备邻苯二甲醛纳米乳的最佳配比为:m(癸甲溴铵)∶m(1,2-丙二醇)=4∶1、m(癸甲溴铵+1,2-丙二醇)∶m(IPM)=9∶1、w(EDTA)=0.05%~1%、w(邻苯二甲醛)=10%;纳米乳在透射电镜下呈球形,粒径分布均匀,平均粒径48.2 nm;恒温加速实验显示其质量稳定,能提高邻苯二甲醛的溶解度,可望用于消毒领域。     

溶剂及TiO2纳米粒子对血红蛋白电子传递的影响

系统考察了血红蛋白分子(Hb)在石墨电极上的直接电子传递性质,结果表明有机溶剂二甲亚砜(DMSO)、表面活性物质双十二烷基二甲基溴化铵(DDAB)及纳米粒子(TiO2)均可改善血红蛋白与电极之间的直接电子传递。在0.1 mol.L-1pH=7.0的PBS缓冲溶液中,固定化Hb显示了一对稳定的峰形对称的氧化还原峰,在扫速为100 mV/s时其电子传递速率常数为3.4 s-1,在20到500 mV/s的扫速范围内,电极响应是一个表面控制过程,其式量电位为Hb/TiO2/DMSO/PG的-(296±8)mV和Hb/TiO2/DDAB/PG的-(172±6)mV(vs.Ag/AgCl)。     

A didodecyldimethylammonium bromide ternary system: Characterization of three-phase stable emulsions by optical microscopy

A preliminary characterization of the didodecyldimethyl ammonium bromide (DDAB)/water (W)/per fluorooctane (PFO) ternary system at 25°C is presented. The gradual addition of water, followed by mixing, to DDAB/PFO mixtures produces very stable emulsions for water contents greater than 20 wt%. On the basis of macroscopic observation, at least four different types of emulsions form up to a water content of around 97 wt%. On the basis of high conductivity values, a water-continuous domain is suggested at all compositions. A second phase diagram, considerably different in phase boundaries, is obtained by adding the PFO oil to DDAB/W samples. This allowed us to ascertain the swelling properties of Lα₁ and Lα₂ lamellar phases. Optical microscopy in the presence and in the absence of polarized light revealed the formation of lamellar liquid crystals either as randomly localized islands or as rings surrounding the oil droplets. Vesicles are identified at high water content. The contemporaneous presence of both Lα₁ and Lα₂ lamellar phases causes a synergistic effect in the PFO stabilization.