Polycations for DNA Complex Formation

DNA-binding polycations include synthetic polymers such as polylysine, polyethylenimine, cationic den-drimers, carbohydrate-based polymers such as modified chitosan or dextran, and natural DNA-binding proteins such as histones or protamines. The characteristics of these polymers and their use in transfections have been reported extensively.[1-3] Of the ''first-generation'' cationic polymeric carriers evaluated, polyethylenimine,[4] also termed PEI, has the highest transfection efficiency. This can be explained by its intrinsic ability to facilitate endosomal release. The polymer acts as a ''proton sponge,'' containing protonable amines which after endocytosis slow down endosomal acidification, trigger ing enhanced endosomal chloride accumulation followed by osmotic swelling and breaking up of endosomes.[5] Biocompatible and biodegradable polymers with further enhanced efficiency would be advantageous. Approaches currently under evaluation include the use of low-molecular weight polymers oligomerized into larger polymeric structures by biodegradable, connecting disul-fide linkages[6] or esters.[7,8]

Getting Started With Dumbbells

Getting Started With Dumbbells

The use of dumbbells gives you a much more comprehensive strengthening effect because the workout engages your stabilizer muscles, in addition to the muscle you may be pin-pointing. Without all of the belts and artificial stabilizers of a machine, you also engage your core muscles, which are your body's natural stabilizers.

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