A multitechnique approach in protein/surfactant interaction study: physicochemical aspects of sodium dodecyl sulfate in the presence of trypsin in aqueous medium.
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: 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: 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: 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: Chemically induced unfolding of bovine serum albumin by urea and sodium dodecyl sulfate: a spectral study with the polarity-sensitive charge-transfer fluorescent probe (E)-3-(4-methylaminophenyl)acrylic acid methyl ester.
abstract: Sensitivity of the charge-transfer (CT) band of the fluorescence probe (E)-3-(4-methylaminophenyl)acrylic acid methyl ester (MAPAME) towards the polarity of its immediate environment is employed to investigate the binding interaction of the probe with bovine serum albumin (BSA) and uncoiling of BSA by the denaturants urea and sodium dodecyl sulfate micelles. Binding of the probe with BSA produces a blue shift and enhanced intensity of the CT emission band which clearly point toward a decrease in polarity of the immediate environment of MAPAME. This is expected, since binding with BSA moves the probe from a polar water environment to a much less polar, hydrophobic protein interior, where the CT band is expected to be blue-shifted. Higher intensity arises due to fewer non-radiative decay paths available to the probe in the hydrophobic protein environment. Chemically induced unfolding of BSA by urea and sodium dodecyl sulfate is tracked by monitoring the induced spectral changes of the protein-bound probe MAPAME. Red-edge excitation shift or REES, fluorescence resonance energy transfer (FRET) and anisotropy measurements are used to investigate and monitor these binding and unfolding processes.

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: Essential role of tuberous sclerosis genes TSC1 and TSC2 in NF-kappaB activation and cell survival.
abstract: The TSC1-TSC2 complex has recently been implicated in cell survival responses. We observed that NF-kappaB signaling is attenuated in TSC1- and TSC2-deficient MEFs concomitant with reduced survival following DNA damage or TNFalpha stimulation. Reconstitution of TSC2 expression in TSC2(-/-) MEFs rescued survival in an NF-kappaB activity-dependent manner. Furthermore, in TSC2(-/-) MEFs, the rapamycin-mediated inhibition of deregulated mTOR activity restored NF-kappaB activation and survival. This rapamycin-mediated effect was reversed by inhibition of NF-kappaB transcriptional activation or by inhibition of ERK1/2 MAP kinase or PI-3K pathways, which lie on signaling cascades that lead to NF-kappaB activation. These results provide evidence for a crosstalk between the TSC/Rheb/mTOR pathway and the NF-kappaB induction pathways and indicate that NF-kappaB functions as an important survival factor that regulates TSC2-dependent cell survival.

title: Activation in vitro of NF-kappa B by phosphorylation of its inhibitor I kappa B.
abstract: Nuclear factor kappa B (NF-kappa B), which was first detected by its binding to the kappa B site in the immunoglobulin kappa-gene enhancer, is important for the regulated expression of the kappa-gene and is partly responsible for the induction in appropriate cells of interleukin-2 (IL-2), IL-2 alpha receptor, beta-interferon and serum amyloid A protein. NF-kappa B is present as a nuclear DNA-binding protein in B lymphocytes and mature macrophages, but is found in the cytoplasm of many cells in a form unable to bind to DNA. The cytoplasmic form is bound to an inhibitor protein, I kappa B, from which it can be released in vitro by deoxycholate and other agents. Activation of cells by various agents, notably the phorbol esters that stimulate protein kinase C (PKC), leads to dissociation in vivo of the NF-kappa B/I kappa B complex and migration of NF-kappa B to the nucleus. Therefore, it acts as a second messenger system, transducing activation signals from the cytoplasm to the nucleus. To elucidate the mechanism of signal transfer, we have used an in vitro system in which addition of purified protein kinases to a partially purified NF-kappa B/I kappa B complex leads to the activation of the DNA-binding activity of NF-kappa B. Using gel retardation assays we found that PKC, cyclic AMP-dependent protein kinase (PKA) and a haem-regulated eIF-2 kinase (HRI) could activate NF-kappa B in vitro, whereas casein kinase II was ineffective. To determine the target for the protein kinases we purified and characterized both NF-kappa B and I kappa B and found that I kappa B is phosphorylated and inactivated in the presence of PKC and HRI but not PKA.

title: Linkage mapping of a complex trait in the New York population of the GAW14 simulated dataset: a multivariate phenotype approach
abstract: Multivariate phenotypes underlie complex traits. Thus, instead of using the end-point trait, it may be statistically more powerful to use a multivariate phenotype correlated to the end-point trait for detecting linkage. In this study, we develop a reverse regression method to analyze linkage of Kofendrerd Personality Disorder affection status in the New York population of the Genetic Analysis Workshop 14 (GAW14) simulated dataset. When we used the multivariate phenotype, we obtained significant evidence of linkage near four of the six putative loci in at least 25% of the replicates. On the other hand, the linkage analysis based on Kofendrerd Personality Disorder status as a phenotype produced significant findings only near two of the loci and in a smaller proportion of replicates.