The laboratory experiments described in this work present the CMC-determination of some surfactants by following three different methods, which require the use of the very common techniques in physical chemistry laboratories, such as UV-Vis spectroscopy, luminescence spectroscopy, and electrical conductivity.In performing these experiments, the CMC of a surfactant is determined by measuring a change (i) in the UV-Vis spectra of benzoylacetone, (ii) in the fluorescence emission spectra of pyrene monomers, and (iii) in the electrical conductivity of an ionic-surfactant solution, as the concentration of the surfactant increases.The CMC values corresponding to the surfactants sodium dodecyl sulfate, tetradecyl trimethylammonium bromide and polyoxyethylene,9-dodecyl ether determined in this work following the three indicated methods and in the absence and presence of electrolytes and non-electrolytes are reported.
The kinetics of the reactions of several secondary aliphatic amines with alkyl nitrites (2-bromoethyl and 1-phenylethyl nitrites) were measured using the spectrophotometric technique in aqueous basic solutions and in the presence of sodium dodecyl sulfate and tetradecyltrimethylammonium bromide. In the case of the cationic micelles, the results were quantitatively interpreted by means of the pseudophase model, which considers micelles acting as a separate phase from water. With the anionic micelles, the results were analyzed by using the simple pseudophase ion-exchange model, in which the alkyl nitrite and the neutral form of the amine are partitioned between the micellar and aqueous pseudophases, and in which the basic ionization equilibria of the amine increases because of the exchange between the alkylammonium ion of the amine and the micellar counterion at the micellar surface. Bimolecular rate constants for the reaction in the micellar pseudophase are always smaller than for those in water. Characteristic features ofthe media and of the substrates in the reactivity behavior of amines are discussed. The binding constants of the amines (by hydrophobic or electrostatic effects) to the micelle are seen as related to the structure, of the amine and the nature of the micellar surface.
Left ventricular hypertrophy is an adaptive response to hypertension, and an independent clinical risk factor for cardiac failure, sudden death, and myocardial infarction. As regression of cardiac hypertrophy is associated with a lower likelihood of cardiovascular events, it is recognized as a target of antihypertensive therapy. This necessitates identification of factors associated with the initiation and progression of hypertrophy. Oxidative stress and metabolic shift are intimately linked with myocardial hypertrophy, but their interrelationship is not clearly understood. This study proposes to identify the temporal sequence of events so as to distinguish whether oxidative stress and metabolic shift are a cause or consequence of hypertrophy. Spontaneously hypertensive rat (SHR) was used as the experimental model. Cardiac hypertrophy was apparent at 2 months of age, as assessed by hypertrophy index and brain natriuretic peptide gene expression. Enhanced myocardial lipid peroxidation accompanied by nuclear factor-kappa B gene expression in one-month-old SHR suggests that oxidative stress precedes the development of hypertrophy. Metabolic shift identified by reduction in the expression of peroxisome proliferator-activated receptor-alpha, medium chain acyl CoA dehydrogenase, and carnitine palmitoyltransferase 1β was seen at 4 months of age, implying that reduction of fatty acid oxidation is a consequence of hypertrophy. Information on the temporal sequence of events associated with hypertrophy will help in the prevention and reversal of cardiac remodeling. Investigations aimed at prevention of hypertrophy should address reduction of oxidative stress. Both, oxidative stress and metabolic modulation have to be considered for studies that focus on the regression of hypertrophy.
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