Charged acrylamide copolymer gels as media for weak alignment

The use of mechanically strained acrylamide/acrylate copolymers is reported as a new alignment medium for biomacromolecules. Compared to uncharged, strained polyacrylamide gels, the negative charges of the acrylamide/acrylate copolymer strongly alter the alignment tensor and lead to pronounced electroosmotic swelling. The swelling itself can be used to achieve anisotropic, mechanical strain. The method is demonstrated for the alignment of TipAS, a 17 kDa antibiotic resistance protein, as well as for human ubiquitin, where alignment tensors with an A(ZZ,NH) of up to 60 Hz are achieved at a gel concentration of 2% (w/v). The alignment can be modulated by the variation of pH, ionic strength, and gel concentration. The high mechanical stability of the swollen gels makes it possible to obtain alignment at polymer concentrations of less than 1% (w/v).