muramidase and dodecyltrimethylammonium

Understanding the mode of action of osmolytes on the protein with and without stressed conditions still requires experimental proof. In this direction, we have studied the interactions of a model protein hen egg white lysozyme (HEWL) and some homopeptides with sorbitol and a mixture of [dodecyltrimethylammonium bromide (DTAB) + sorbitol] by using a combination of high sensitivity calorimetry, density, sound velocity, and conductivity measurements with spectroscopic support. The physical chemistry underlying these interactions has been addressed on the basis of the energetics of interactions and other physicochemical properties. These results have highlighted that, even though the number of -CONH groups increases in higher homopeptides, the hydrophobic effect of - CH

Topics: Circular Dichroism; Electric Conductivity; Glycine; Micelles; Muramidase; Osmolar Concentration; Peptides; Quaternary Ammonium Compounds; Sorbitol; Spectrometry, Fluorescence; Thermodynamics

We investigate the competition between the associations of oppositely charged protein-surfactant complexes and oppositely charged surfactant complexes. In all systems examined, the most favorable complexation is the one between the two oppositely charged surfactant ions, despite the strong binding known, for example, dodecyl sulfate, DS-, to lysozyme. Thus, the phase behavior of the catanionic system is dominating the features observed also in the presence of protein. The phase behavior of the dilute protein-free dodecyltrimethylammonium chloride-sodium dodecyl sulfate-water system is presented and used as a basis for the discussion on the different solubilization mechanisms. Our results show that the mechanism for resolubilization of a protein-surfactant salt is fundamentally different when it is caused by addition of a second surfactant than when it is accomplished by an excess of the first surfactant. The competition between lysozyme and cationic amphiphiles as hosts for the anionic surfactants was studied experimentally and analyzed quantitatively. Aggregates with C12 cationic surfactants are clearly preferred by the anionic surfactants, while for C10 and particularly C8 a clear excess of cationic surfactant has to be added to completely dissolve the complex salt lysozyme-anionic surfactant.

Topics: Cations; Muramidase; Quaternary Ammonium Compounds; Sodium Dodecyl Sulfate; Solubility; Spectrophotometry, Ultraviolet; Surface Tension; Surface-Active Agents; Water

The study includes partitioning of proteins in aqueous two-phase systems consisting of the polymer dextran and the non-ionic surfactant C12E5 (pentaethylene glycol mono-n-dodecyl ether). In this system a micelle-enriched phase is in equilibrium with a polymer-enriched phase. Charges can be introduced into the micelles by the addition of charged surfactants. The charge of the mixed micelles is easily varied in sign and magnitude independently of pH, by the addition of different amounts of negatively charged surfactant, sodium dodecyl sulphate (SDS), or positively charged surfactant dodecyl trimethyl ammonium chloride (DoTAC). A series of water-soluble model proteins (BSA, beta-lactoglobulin, myoglobin, cytochrome c and lysozyme), with different net charges at pH 7.1, have been partitioned in non-charged systems and in systems with charged mixed micelles or charged polymer (dextran sulphate). It is shown that partition coefficients for charged proteins in dextran-C12E5 systems can be strongly affected by addition of charged surfactants (SDS, DoTAC) or polymer (dextran sulphate) and that the effects are directly correlated to protein net charge.

Topics: Buffers; Cytochrome c Group; Dextran Sulfate; Ethers; Hydrogen-Ion Concentration; Isoelectric Point; Lactoglobulins; Micelles; Muramidase; Myoglobin; Polyethylene Glycols; Polymers; Proteins; Quaternary Ammonium Compounds; Serum Albumin, Bovine; Sodium Chloride; Sodium Dodecyl Sulfate; Surface Properties; Surface-Active Agents; Water

Binding of lysozyme with cetyltrimethylammonium bromide (CTAB) and dodecyl-trimethylammonium bromide (DTAB) at various detergent concentrations and pH was studied at 25 degrees C by equilibrium dialysis technique. In the case of CTAB, binding isotherms at pH 5.0, 7.0, and 9.0 show cooperative binding at all the concentrations of the detergent and the binding ratios increase with pH. Cooperative binding is also shown by DTAB at all the concentrations and pH, but the binding ratios are lower compared to CTAB. The Gibb's free energy change calculated on the basis of Wyman's binding potential concept increases with pH, indicating increased binding strength of CTAB at higher pH. The UV difference spectra of CTAB and DTAB with lysozyme and its model compounds such as L-Trp, L-Tyr X HCI and L-Phe show two peaks at 297 nm and 250 nm at pH 9.0 indicating the possible involvement of tryptophans as the binding sites along with the carboxylate anion or the phenolic group of a tyrosine on lysozyme. The effect of higher ionic strength on the binding of CTAB with lysozyme at pH 9.0 is evidenced by lower binding ratios and decreased intensities of the UV difference bands, thus indicating the involvement of electrostatic interactions. However, the hydrophobic interactions between the detergents and the aromatic amino acid residues in lysozyme contribute more to the binding strength. The binding of these cationic detergents by lysozyme induces conformational changes in the enzyme. They are followed by the circular dichroism (CD) technique which shows a decrease in the aromatic bands in the 320-250 nm region.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Cetrimonium; Cetrimonium Compounds; Chickens; Circular Dichroism; Detergents; Hydrogen-Ion Concentration; Kinetics; Muramidase; Protein Binding; Quaternary Ammonium Compounds; Spectrophotometry, Ultraviolet; Surface-Active Agents; Thermodynamics