sepharose and dodecyl-sulfate

The formation of silver patterns via electrolysis from aqueous silver sulfate + x% w/v agarose sol and gel media, with and without supporting electrolyte, in a quasi-two-dimensional (2D) cylindrical cell at room temperature, is utilized as a reference system to investigate the complexity of pinning effects. From pattern morphology and electrochemical data, both delocalized and localized pinning in the bulk dominate the drift of the growth front, depending on the concentration of agarose in the heterogeneous media. Delocalized pinning results from mobile, small agarose aggregates at the growth front and from their accumulation by the front drift. For gels, localized pinning comes from their own percolated structure. A depinning/pinning transition is observed in going from sols to gels. The relative contribution of diffusion and advection in mass-transport-controlled silver electrodeposition depends on the plating bath composition. On the other hand, silver ion attachment to the cathode appears to be interfered with by some screening caused by weakly adsorbed, mobile agarose aggregates at the metal surface without slowing down the rate of the electron-transfer step at the cathode. Their relative contribution of a delocalized, localized pinning and screening effect to a great extent determines the morphology and transition in the growth mode of silver patterns in both media. The analysis of charge and current transients and the corresponding silver pattern morphologies for open and dense radial patterns is made. Results are qualitatively simulated with a novel, rather simple cellular automaton algorithm.

Topics: Electrochemistry; Electrolytes; Gels; Models, Molecular; Molecular Conformation; Polymethyl Methacrylate; Sepharose; Silver; Sodium Dodecyl Sulfate

Detergent-saturated phenyl-Sepharose was used to exchange detergents for one another in the presence of membrane proteins. The alkyl detergents lauryl maltoside, octyl glucoside, and dodecyl sulfate were each successfully exchanged for Triton X-100, Triton N-101, or Nonidet P-40 present in a solution of either cytochrome c oxidase, a mixture of inner mitochondrial membrane proteins, or a mixture of erythrocyte membrane proteins. The method involves (1) saturating a small column of phenyl-Sepharose (1-2 mL) with one of the alkyl detergents at a pH of 8 or 9 and an ionic strength of 0.01, (2) applying a detergent-solubilized membrane protein sample containing as much as 20 mg/mL of Triton X-100, Triton N-101, or Nonidet P-40, and (3) eluting the protein with buffer containing the detergent with which the resin had been saturated. With this approach, 90-99% of the detergent in the initial protein sample was exchanged for the second detergent with an 80-100% recovery of protein. The advantages of this method over previous approaches for exchanging detergents include the rapidity of the technique and the apparent general applicability of the method to a wide variety of detergents and membrane proteins.

Topics: Animals; Cattle; Chromatography, Affinity; Detergents; Electron Transport Complex IV; Fatty Alcohols; Glucosides; Humans; Membrane Proteins; Nonoxynol; Octoxynol; Polyethylene Glycols; Saccharomyces cerevisiae; Sepharose; Sodium Dodecyl Sulfate; Surface-Active Agents

Naked nuclear DNA is easily sheared. Two general methods are described for preparing intact DNA in a stable form that can be pipetted without breaking it. Cells are encapsulated in agarose microbeads and then lysed in a non-ionic detergent (i.e., Triton X-100) and 2 M NaCl or an ionic detergent (e.g., sodium or lithium dodecyl sulphate) in low salt. Most cellular protein and RNA then diffuse out through pores in the beads to leave encapsulated and naked DNA which is nevertheless accessible to enzymes and other probes. Remarkably, considerable structure is preserved since the DNA is supercoiled and chromosomes retain their shape.

Topics: Cell Nucleus; Chromosomes; DNA; DNA, Superhelical; Fatty Alcohols; HeLa Cells; Humans; Methods; Microspheres; Sepharose; Sodium Dodecyl Sulfate