Enrichment of nucleic acids

Provided are methods directed to enriching nucleic acids in a biological sample. These methods, in some embodiments can discriminately enrich the abundance of low-copy nucleic acids relative to higher-copy nucleic acids. In some embodiments, the methods provided can enrich a low-copy number mutant allele associated with a disease state, thus allowing early detection and optimized treatment. In other embodiments, the methods can be used for detection of particular molecules, such as antigens, in a sample.