The high resolving power of polyacrylamide (PA) gels for proteins, peptides and nucleic acids can be improved by using gradient gels instead of homogeneous (i.e. single concentration) gels. However, a more specific separation of polynucleotides in PA gels affords separation by incorporating a 40-80% denaturant gradient (7molL_1 urea, 40% (v/v) form-amide) into a homogeneous PA gel (of e.g. 6.5% (w/v) total polymer concentration) or applying a temperature gradient to a homogeneous PA gel.

In PA gradient gels the average pore radius decreases with increasing gel concentrations, i.e. in the direction of the migrating protein (polynucleotide) bands. This results in a sharpening of the bands because the molecules at the front of the moving band are slower than those at the rear. Because of this effect, gradient gels need not be covered by a stacking gel, as in disc gel electrophoresis. In porosity gradient the separation of proteins in the range from 1 to 100 kDa. Analytical Biochemistry 166: 368.

Shapiro AL, Vinuela E and Maizzel Jr JV (1967) Molecular weight estimation of polypeptide chains by electrophor-esis in SDS-polyacrylamide gels. Biochem. Biophys. Res. Commun. 28: 815.

Takano E, Maki M, Mori H, Hatanaka N, Marti T, Titani K, Kannagi R, Ooi T and Murachi T (1988) Pig heart calpastatin: identiRcation of repetitive domain structures and anomalous behaviour in poly-acrylamide gel electrophoresis. Biochemistry 27: 1964.

Weber K, Pringle JR and Osborn M (1972) Measurement of molecular weights by electrophoresis on SDS-acrylam-ide gel. Methods in Enzymology 26: 3.

gels with a steep increase of polymer concentration (e.g. from 4 to 30% T (w/v) where %T = g acrylam-ide + g Bis = N,N'-methylenebisacrylamide (Bis) per 100 mL) proteins of a large size range (approximately 104-106 Da) can be separated. In shallow gradients ( > 4% T to < 30% T), the separable size range of proteins is limited but they still provide an improved band sharpening.

There are two modes to run porosity gradient gels: a fixed-time mode, where electrophoresis is terminated after a certain time, and a time-dependent mode, which means that a number of consecutive electro-phoretic mobilities are registered. Fixed-time elec-trophoresis is performed if protein (polynucleotide) patterns are to be screened, such as in population genetics or when determining the molecular mass of sodium dodecyl sulfate (SDS) denatured proteins. Molecular size properties of nondenatured proteins, however, cannot be elucidated that way, but afford time-dependent investigation of protein mobilities. On the other hand, time-dependent PA gradient gel electrophoresis not only offers the possibility to estimate the molecular mass of native proteins and enzymes but also allows determination of their Stokes radius, frictional coefficient, free electrophoretic

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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