Capillary electrophoresis of DNA fragments in 9 to 20% uncrosslinked polyacrylamide gels: unique separating capacity hypothetically related to maintenance of random-coil DNA conformation independently of gel concentration

Electrophoretic mobility of semi-flexible double-stranded DNA in defect-controlled polymer networks: Mechanism investigation and role of structural parameters

Our previous studies have reported an empirical model, which explains the electrophoretic mobility (μ) of double-stranded DNA (dsDNA) as a combination of a basic migration term (Rouse-like or reptation) and entropy loss term in polymer gels with ideal network structure. However, this case is of exception, considering a large amount of heterogeneity in the conventional polymer gels. In this study, we systematically tune the heterogeneity in the polymer gels and study the migration of dsDNA in these gels. Our experimental data well agree with the model found for ideal networks. The basic migration mechanism (Rouse-like or reptation) persists perfectly in the conventional heterogeneous polymer gel system, while the entropy loss term continuously changes with increase in the heterogeneity. Furthermore, we found that in the limit where dsDNA is shorter than dsDNA persistence length, the entropy loss term may be related to the collisional motions between DNA fragments and the cross-links.

Ultrathin-layer sodium dodecyl sulfate gel electrophoresis of proteins: effects of gel composition and temperature on the separation of sodium dodecyl sulfate-protein complexes

This paper discusses the effects of gel composition and separation temperature on the migration properties of fluorescein-5-isothiocyanate-labeled protein molecular mass markers (ranging from 20 100 to 205 000 Da) in automated ultrathin-layer sodium dodecyl sulfate (SDS) gel electrophoresis. The separation mechanism with the agarose and composite agarose - linear polyacrylamide, agarose - hydroxyethyl cellulose, and agarose - polyethylene oxide matrices were all found to comply with the Ogston sieving model in the molecular mass range of the protein molecules investigated. Our temperature studies revealed that electrophoretic separation of SDS protein complexes is an activated process and, in pure agarose and in composite agarose hydroxyethyl cellulose and agarose - polyethylene oxide matrices that the separation requires increasing activation energy as a function of the molecular mass of the separated proteins. On the other hand, when linear polyacrylamide was used as composite additive, the activation energy demand of the separation decreased with increasing solute molecular mass. The sensitivity of the laser-induced fluorescent detection of the automated ultrathin-layer electrophoresis system was evaluated by injecting a series of dilutions of the markers and was found to be less than 2.5 ng/band for the fluorophore-labeled protein.

Gel electrophoretic distinction between toxic and nontoxic forms of beta-amyloid (1-40)

The in vitro toxicity of synthetic beta-amyloid (1-40) correlates with its binding to Congo red (CR). Potentially, therefore, CR binding to the beta-amyloid containing neuritic plaques in Alzheimer's disease could be used diagnostically. Using polyacrylamide under nondenaturing conditions, the present study shows that both CR binding and nonbinding synthetic beta-amyloid exhibits multiple charge-isomeric and size-isomeric species. The CR binding species exhibit values of free electrophoretic mobility, related to the surface charge density of the protein, which are less than those of the CR non-binding species within 95% confidence limits. Since surface net charge and solubility are correlated, the decreased solubility of the CR binding species may be responsible for the relative abundance and CR binding of beta-amyloid in the neuritic plaques of Alzheimer patients.