Water sorption in a dextran gel

The state of adsorbed water in a dextran gel has been investigated by near-infrared and gravimetric-adsorption techniques. Water-vapor adsorption (desorption) isotherms at three temperatures are reported. The calculated sorption heats are found to be markedly temperature-dependent as well as dependent on the coverage. The near-infrared spectrum (4650–9000 cm^-1) is reported, together with tentative assignments. The H₂O combination (ν + δ) band at 5184 cm_-1 has been examined as a function of relative humidity. The line-shapes of this band have been analyzed by a recently established, Fourier-inversion technique, and information on the microdynamics of the adsorbed water molecules has been resolved on the picosecond time-scale. At low and intermediate degrees of hydration, reorientational jumps take place with periods from four to six times longer than those for free water. The onset of saturation is then accompanied by the sudden removal of the reorientational jumps. A comparison of microdynamical and thermodynamic data indicates the hydration mechanism to be highly cooperative at all relative humidities.     

Cost-effective gel documentation using a web-cam.

In search for a cost effective gel documentation system applicable for different fields of molecular biology, we analyzed the capabilities of a cheap CCD-camera originally designed to capture images for transmission through the internet (web-cam) with regard to gel documentation. The camera was connected to a personal computer by universal serial bus (USB) and used for the documentation of DNA separated on agarose gels and stained by ethidium-bromide using the software provided with the camera. The web-cam provided digital images of sufficient quality for routine documentation and combined the low set-up costs of a Polaroid system with the low running costs of video capture systems, hence is ideal as a start-up system and as augmentation to existing equipment.     

Universal behaviour of gel formation from acrylamide-carrageenan mixture around the gel point: a fluorescence study

The steady state fluorescence (SSF) technique was used to study the sol-gel transition, for the solution free radical crosslinking copolymerization of acrylamide (AAm) with various carrageenan content. N, N'- methylenebis (acrylamide) (BIS) and ammonium persulfate (APS) are used as crosslinker and an initiator, respectively. Pyranine (8-hydroxypyrene-1, 3,6-trisulfonic acid, trisodium salt, HPTS) was added as a floroprobe for monitoring the polymerization. Pyranine molecules start to bind to acrylamide polymer chains upon the initiation of the polymerization; thus, the spectra of the bonded pyranines shift to the shorter wavelengths. Fluorescence spectra from the bonded pyranines allows one to monitor the sol-gel transition, without disturbing the system mechanically, and to test the universality of the sol-gel transition as a function of some kinetic parameters like polymer concentration. Observations around the critical point show that the gel fraction exponent beta obeyed the percolation result for low carrageenan concentrations (< 2.0%) however classical results were produced at higher carrageenan concentration (> 2.0%).     

Agarose: a possible universal gel exclusion agent

Granulated agarose gels suitable for gel exclusion chromatography of proteins of any molecular weight may now be prepared. This was made possible by the observation that agarose solutions of 16% polysaccharide may be prepared by displacing 8% agarose from solution with 8% polyethylene glycol Mr 6000. The displaced polysaccharide concentrates in a viscous mass occupying half the volume of the original carbohydrate solution. By diluting the displaced polysaccharide with hot watery solutions of electrolyte and allowing the solutions to congeal, gels of any desired concentration, ranging from low to the maximum of 16%, may be prepared.     

Electroelution of protein fractions from a polyacrylamide gel

A method for electroelution of protein fractions from polyacrylamide gel and device for performing such a process have been developed. The application of two tris-glycine buffers with the low and high ionic strength, pH 9.0-9.2 provides a concentration of protein simultaneously to extraction from the gel. The duration of elution is in the range of 1-3 hours and depends on the protein mobility. The effectiveness of the system is demonstrated for disc-electrophoretic separation and electrophoresis in slab gel in the presence of SDS. The maximal amount of pure protein fraction obtained is about 4.5-5.0 mg. The method may be useful especially for the fractionation of limited quantities of protein samples.     

A disposable biosensor employing a glucose-sensitive biochemomechanical gel

A novel approach to construct a disposable biosensor is proposed. By immobilizing glucose oxidase in a pH-sensitive copolymerized poly(N-isopropylacrylamide)/acrylic acid gel, a glucose-sensitive gel can be obtained. When the gel makes contact with a sample solution containing glucose, the pH of the gel decreases as a result of the enzymatic reaction, inducing the collapse of the gel. The response time to the shrinkage depended upon the activity of the enzyme and the concentration of glucose, although the final ratio of shrinkage settled to approximately the same value irrespective of the concentration of glucose. The transient stage can be used for sensing. The volume change of the gel was transduced into the movement of a colored solution in a flow channel with the help of a silicone rubber diaphragm. The mechanism was used to construct a disposable glucose sensor. A clear dependence of the column length of the colored solution on the concentration of glucose was observed. By measuring the change at a predetermined time, the glucose concentration was obtained. This sensor can be considered the ultimate style in disposable sensors, as detection does not require any electrical measurement or spectroscopic procedures.     

Two-dimensional agarose gel electrophoresis without gel manipulation

The apparatus and procedure to perform two-dimensional agarose gel electrophoresis without manipulating the gel used for the first electrophoresis (first-dimension gel) have been developed. The procedure is less complex, less damaging to first-dimension gels, and more precise than procedures that require manipulation of the first-dimension gel. When combined with gel-embedding techniques, the procedure presented can be used to perform the second electrophoresis in a gel different from the first-dimension gel. A first-dimension gel too dilute to be manipulated and a more concentrated gel for the second electrophoresis have been used to separate DNA open circles from a mixture of variable-length linear DNAs.     

Two-dimensional gel electrophoresis in proteomics: a tutorial

Two-dimensional electrophoresis of proteins has preceded, and accompanied, the birth of proteomics. Although it is no longer the only experimental scheme used in modern proteomics, it still has distinct features and advantages. The purpose of this tutorial paper is to guide the reader through the history of the field, then through the main steps of the process, from sample preparation to in-gel detection of proteins, commenting the constraints and caveats of the technique. Then the limitations and positive features of two-dimensional electrophoresis are discussed (e.g. its unique ability to separate complete proteins and its easy interfacing with immunoblotting techniques), so that the optimal type of applications of this technique in current and future proteomics can be perceived. This is illustrated by a detailed example taken from the literature and commented in detail. This Tutorial is part of the International Proteomics Tutorial Programme (IPTP 2).     

Bacterial synergism or antagonism in a gel cassette system

The growth and the metabolic activity of Shewanella putrfaciens, Brochothrix thermosphacta, and Pseudomonas sp., when cultured individually or in all possible combinations in gel cassettes system supplemented with 0.1% glucose at 5 degrees C, were investigated. The overall outcome was that the coexistence of the above-mentioned microorganisms affected not only each growth rate but also their type of metabolic end products compared to the control cultures. These effects were varied and depended on the selection of the combination of the tested bacteria. For example, the growth of Pseudomonas sp. strains cocultured with either B. thermosphacta or S. putrefaciens strains resulted in different effects: a promoting one for the first and an inhibitory one for the second. Moreover, the production of formic acid and two unidentified organic acids (peaks a and b) was characteristic in all cases in which S. putrefaciens was cultured.