Conformational study of papain in the presence of sodium dodecyl sulfate in aqueous medium.
The interactions between a globular protein, papain and the anionic surfactant, sodium dodecyl sulfate (SDS) have been investigated in aqueous medium using fluorimetric, circular dichroism, Fourier transform infra-red, UV-vis spectrophotometric, dynamic light scattering, and nuclear magnetic resonance techniques. The conformational change of papain in aqueous solution has been studied in the presence of SDS. The results show the high alpha-helical content and unfolded structure of papain in the presence of SDS due to strong electrostatic repulsion leading to a "necklace and bead model" in protein-surfactant complexes.

title: A multitechnique approach in protein/surfactant interaction study: physicochemical aspects of sodium dodecyl sulfate in the presence of trypsin in aqueous medium.
abstract: Interaction of sodium dodecyl sulfate (SDS) with a globular protein, trypsin, has been physicochemically studied in aqueous medium in detail using tensiometric, conductometric, calorimetric, fluorimetric, viscometric, and circular dichroism techniques. The results indicate that SDS-trypsin aggregates start to form at a surfactant concentration higher than the critical micelle concentration of pure SDS micelle. In contrast, the counterion binding decreases in the presence of trypsin. The free energies and enthalpies of micellization, interfacial adsorption, and entropy of micellization associated with the interaction have also been calculated. The values show that the interaction phenomenon is entropy controlled and endothermic in nature. The increase in viscosity is observed for the system of SDS-trypsin cluster above the critical micelle concentration of SDS micelle only. The aggregation number and interface polarity decrease compared to the values of micelles without protein. Circular dichroism spectra show the high alpha-helical content and unfolded structure of trypsin in the presence of SDS due to strong electrostatic repulsion leading to a probable "necklace and bead" model in the case of biopolymer-surfactant complexes.

title: Interfacial and self-aggregation of binary mixtures of anionic and nonionic amphiphiles in aqueous medium.
abstract: Interfacial and bulk properties of sodium dodecyl sulfate (SDS), polyoxyethylene (20) sorbitan monooleate (Tween-80), and their binary mixtures in aqueous medium have been investigated using surface tension, conductance, and fluorescence measurements at different temperatures. The critical micelle concentration (CMC), counterion binding, polarity index, aggregation number, thermodynamics of interfacial adsorption, and micellization are evaluated. The entropic contribution is found to be the predominant factor in micelle formation. The aggregation number and the polarity index of the micelle interior estimated by the pyrene fluorescence technique show interesting temperature dependence. The size and composition of the mixed micelles vary with the total concentration. The micellar compositions, activities of the individual components in the mixed species, and intersurfactant interactions are also estimated following regular solution theory, excess thermodynamic functions, and a molecular thermodynamic model. The surfactant mixtures are found to be nonideal with a lower degree of counterion binding compared to the individual members. Mixed micelles are nonspherical in nature at all temperatures when the mole fraction (α) of the ionic part in mixtures is high but transform to spherical when α(SDS) is ≤0.50.

title: Mixed micelle formation among anionic gemini surfactant (212) and its monomer (SDMA) with conventional surfactants (C12E5 and C12E8) in brine solution at pH 11.
abstract: The micellization of anionic gemini surfactant, N,N'-ethylene(bis(sodium N-dodecanoyl-beta-alaninate)) (212), and its monomer, N-dodecanoyl-N-methyl alaninate (SDMA), and polyethoxylated nonionic surfactants, C(12)E(5) and C(12)E(8), has been studied tensiometrically in pure and mixed states in an aqueous solution of 0.1 M NaCl at pH 11 to determine physicochemical properties such as critical micellar concentration (cmc), surface tension at the cmc (gamma(cmc)), maximum surface excess (Gamma(max)) and minimum area per surfactant molecule at the air/water interface (A(min)). The theories of Rosen, Rubingh, Motomura, Maeda, and Nagarajan have been applied to investigate the interaction between those surfactants at the interface and in the micellar solution, the composition of the aggregates formed, the theoretical cmc in pure and mixed states, and the structural parameters as proposed by Tanford and Israelachvili. Various thermodynamic parameters (free energy of micellization and interfacial adsorption) have been calculated with the help of regular solution theory and the pseudophase model for micellization.

title: Interaction of trypsin with sodium dodecyl sulfate in aqueous medium: a conformational view.
abstract: The conformational behavior of a globular protein, trypsin has been studied in presence of an anionic surfactant, sodium dodecyl sulfate (SDS) in aqueous medium by different techniques, such as, viscometry, circular dichroism, fluorimetry, Fourier transform infra-red, UV-vis absorption, dynamic light scattering and nuclear magnetic resonance. The results indicate that the viscosity of the mixture increases above the critical micelle concentration of SDS micelle supporting an expansion of a protein coil in the cluster. The spectroscopic techniques show the change of the conformation, i.e., the change of the values of alpha-helicity, beta-sheet, and random-coil of trypsin in the presence of SDS, and ultimately unfolding of trypsin occurs due to strong electrostatic repulsion of micellar clusters of the protein-surfactant complexes.

title: Detection of a large number of subgroup 1 human rotaviruses with a “long” RNA electropherotype
abstract: SummaryThe long or short electrophoretic migration patterns of group A human rotaviruses are linked to their subgroup antigenic specificities. Long pattern isolates usually belong to subgroup 2 (SG2) and short pattern to subgroup 1 (SG1). To date detection of only 4 isolates which do not follow this linkage, have been reported. In the present communication we report the detection of unusually large number (39 isolates) of long pattern human isolates with SG1 specificities.

title: Dopexamine hydrochloride: pharmacology and use in low cardiac output states.
abstract: T HE TERM “INOTROPE” is broadly used to describe agents that enhance cardiac performance, although the mechanism by which some of these drugs improve myocardial function may be attributable less to their effect on myocardial contractility than to the other hemodynamic changes that are associated with their use. In the treatment of cardiac failure, agents with pharmacodynamic profiles that combine relatively mild direct effects on the myocardium with those resulting from a relatively greater effect on preload and afterload offer potential benefits from the standpoint of myocardial energy use. This is of prime concern in both the acutely or chronically ischemic heart and following cardiopulmonary bypass (CPB) when cardiac failure can, on occasion, be ascribed more to unavailability of energy reserves than to persisting ischemia. Dopexamine hydrochloride, a synthetic analog of dopamine, is characterized by just such a profile of action and may offer a favorable alternative to the more established therapeutic regimens of dopamine and dobutamine. The pharmacology of dopexamine and its use in the treatment of chronic or postoperative cardiac failure is reviewed here.

title: The role of sodium dodecyl sulfate (SDS) micelles in inducing skin barrier perturbation in the presence of glycerol.
abstract: The stratum corneum (SC) serves as the skin barrier between the body and the environment. When the skin is contacted with an aqueous solution of the surfactant sodium dodecyl sulfate (SDS), a well-known model skin irritant, SDS penetrates into the skin and disrupts this barrier. It is well established, both in vitro and in vivo, that the SDS skin penetration is dose-dependent, and that it increases with an increase in the total SDS concentration above the critical micelle concentration (CMC) of SDS. However, when we added the humectant glycerol at a concentration of 10 wt% to the aqueous SDS contacting solution, we observed, through in vitro quantitative skin radioactivity assays using (14)C-radiolabeled SDS, that the dose dependence in SDS skin penetration is almost completely eliminated. To rationalize this important observation, which may also be related to the well-known beneficial effects of glycerol on skin barrier perturbation in vivo, we hypothesize that the addition of 10 wt% glycerol may hinder the ability of the SDS micelles to penetrate into the skin barrier through aqueous pores that exist in the SC. To test this hypothesis, we conducted mannitol skin permeability as well as average skin electrical resistivity measurements in vitro upon exposure of the skin to an aqueous SDS contacting solution and to an aqueous SDS + 10 wt% glycerol contacting solution in the context of a hindered-transport aqueous porous pathway model of the SC. Our in vitro studies demonstrated that the addition of 10 wt% glycerol: (i) reduces the average aqueous pore radius resulting from exposure of the skin to the aqueous SDS contacting solution from 33 +/- 5 Angstrom to 20 +/- 5 Angstrom, such that a SDS micelle of radius 18.5 +/- 1 Angstrom (as determined using dynamic light-scattering measurements) experiences significant steric hindrance and cannot penetrate into the SC, and (ii) reduces the number density of aqueous pores in the SC by more than 50%, thereby further reducing the ability of the SDS micelles to penetrate into the SC and perturb the skin barrier.

title: Fluorescent Probing of Protein Bovine Serum Albumin Stability and Denaturation Using Polarity Sensitive Spectral Response of a Charge Transfer Probe
abstract: The polarity sensitive photo-induced intra-molecular charge transfer (ICT) fluorescence probe (E)-3-(4-methylamino-phenyl)-acrylic acid ethyl ester (MAPAEE) has been used to study the model protein Bovine Serum Albumin (BSA) in its native and thermal and urea induced denatured states. The interaction between BSA and the regular surfactant Sodium Dodecyl Sulphate (SDS) as well as the biologically relevant steroid-based amphiphile Sodium Deoxycholate (NaDC) has also been very keenly followed using this ICT probe. The variation of micellar properties of both SDS and NaDC with increasing ionic strengths and in presence of the chaotrope urea has also been well documemted by the same probe. Steady-state spectroscopy, FRET, and fluorescence anisotropy measurements have been used to gain better insight into these processes and the molecule MAPAEE to be a full-bodied fluorescent probe for studying such intricate biological systems, their properties and interactions.

title: Comparison of the cortical connections of areas 4 gamma and 4 delta in the cat cerebral cortex.
abstract: Area 4 of the cat cerebral cortex has been subdivided into several regions based on cytoarchitectonic studies: areas 4 gamma, 4 delta, 4sfu, and 4fu (Hassler and Muhs-Clement [1964] J. Hirnforsch. 6:377-420). In a previous study, we found separate representations of contralateral limb movements in areas 4 gamma and 4 delta (Ghosh [1997] ). To investigate the relationship between these representations, the ipsilateral cortical connections of area 4 gamma and 4 delta were compared by the use of the retrograde neural tracers. After intracortical microstimulation of area 4, tracer was injected into one or two of the following regions: the forelimb regions of the rostral and caudal subdivisions of areas 4 gamma and 4 delta (r4 gamma, r4 delta, c4 gamma, c4 delta, separated by the cruciate sulcus) and the hindlimb regions of c4 gamma and c4 delta. Retrogradely labeled neural profiles were counted in every fourth section of the coronal series and located in cytoarchitectonic areas of the ipsilateral cortex. We found topographically organized reciprocal connections between areas 4 gamma and 4 delta; these connections were part of a rich network of interconnections between the cytoarchitectonic subdivisions of area 4. The forelimb regions of c4 gamma and c4 delta, of r4 gamma and c4 delta, and of r4 gamma and r4 delta were interconnected. These findings support the location of a secondary motor area in 4 delta. No interconnections between the forelimb regions of r4 gamma and c4 gamma, and of r4 delta and c4 gamma, could be found. Area 6 (particularly area 6a gamma) was found to project strongly to the forelimb regions of r4 gamma and r4 delta and relatively weakly to the forelimb region of c4 delta. Retrogradely labeled neurons were also detected in areas 3a, 3b, 1, 2pri, 5, 7, and insula after tracer injections in area 4.