Another form of non denaturing SDS-PAGE is called diagonal electrophoresis: Peptide joined together by disulfide bond can be detected by diagonal electrophoresis. The mixture of peptide is subjected to electrophoresis in single lane in vertical direction (without treatment with reducing agents). After first run, gel is treated with reducing agent and run in second direction (horizontal). Peptide joined by disulfide will not come in diagonal line in second direction as their molecular mass changes due to reduction of disulfide bonds (peptides are separated)