SDS-PAGE is usually used to estimate relative molecular mass, to determine the relative abundance of major proteins in a sample, and to determine the distribution of proteins among fractions. Different staining methods, such as Coomassie blue staining and silver staining, can be used to detect separated proteins and to get some information about their biochemical properties. Specialized techniques based on SDS-PAGE such as western blotting, native PAGE and two-dimensional electrophoresis can be further used to detect and separate complex protein samples.