Thin-layer cellulose media

As we compare paper with thin-layer chromatography, we can see that paper sheets as such probably will be supplanted by thin-layer cellulose media. This means that the same immobile-mobile systems that are applied to paper can also be used for cellulose thin layer. The inorganic adsorbents do not appear to be very efficient for resolving highly polar compounds. When they are impregnated with immobile phases, ascension times are increased greatly because the capillaries are being... 

The support medium may be a sheet of cellulose or a glass or plastic plate covered with a thin coating of silica gel, alumina, or cellulose. Large sheets of cellulose chromatography paper are available in different porosities. These may be cut to the appropriate size and used without further treatment. The paper should never be handled with bare fingers. Although thin-layer plates can easily be prepared, it is much more convenient to purchase ready-made plates. These are available in a variety of sizes, materials, and thicknesses of stationary support. They are relatively inexpensive and have a more uniform support thickness than hand-made plates. 

While thin layers of cellulose is the medium favored by most investigators in recent years for the separation of amino acids in bio-... 

In cross-flow flltration, the wastewater flows under pressure at a fairly high velocity tangentially or across the filter medium. A thin layer of solids form on the surface of the medium, but the high liquid velocity keeps the layer from building up. At the same time, the liquid permeates the membrane producing a clear filtrate. Filter media may be ceramic, metal (e.g., sintered stainless steel or porous alumina), or a polymer membrane (cellulose acetate, polyamide, and polyacrylonitrile) with pores small enough to exclude most suspended particles. Examples of cross filtration are microfiltration with pore sizes ranging from 0.1 to 5 pm and ultrafiltration with pore sizes from 1 pm down to about 0,001 pm. 

Cellulosic fibers may also be pressed into transparent films without the addition of any medium. Such samples are randomly oriented. A further method for investigating cellulosic fibers involves pressing out a very thin layer of contiguous filaments. Under favorable conditions, there results a thin, cohesive layer of oriented fibers that is sufficiently transparent for study in the infrared, without the need for any liquid or solid embedding medium. The purpose in preparing such a sample is to try to extend the use of polarized infrared spectroscopy beyond the field of films. Films are eminently suitable as samples, but information is sometimes required on the fibrous form itself and this must be obtained directly. 

Materials such as filter paper, cellulose acetate, gels made from starch, agar or polyacrylamide and thin layers of silica and alumina have been used as the supporting medium for the electrolyte solution and sample. 

To measure the GTPase-activation of the ARE domain by the non-ARF domain of ARDl, samples of the ARDl ARF domain (typically 50 pmol) were incubated in stripping buffer for 30 min and then, for 40 min in the same medium plus 0.5 /xM [a PGTP] (3000 Ci/mmol) and 10 mM MgCl2 (120 /xl final volume). After addition of the non-ARF domain of ARDl (50 pmol in 40 /xl), the mixture (160 /xl) was incubated at 25° for 30 min before proteins were collected on nitrocellulose filters in a manifold, washed, and air-dried. Nucleotides were eluted from filters in 2 M formic acid (250 /xl) and samples (2-4 /xl) analyzed by thin layer chromatography on polyethyleneimine-cellulose plates followed by autoradiography. Radioactivity in the remaining eluate was quantified to determine total protein-bound nucleotide (Vitale et al., 2001). ... 

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