Purification of intact nucleic acid from samples

is required for many molecular biology applications. Accurate PCR replication of RNA and DNA sequences requires complete removal of cellular lipids and proteins. Likewise, most restriction endonucleases used to digest genomic DNA are inactivated or degraded by cellular proteases normally present prior to purification of the nucleic acids. Thus, failure to remove these cellular contaminants often leads to poor results. The assessment of the purity of a nucleic acid sample is usually performed by a procedure known as the A260/A280 or 260/280 ratio. While this procedure was first described by Warburg and Christian in 1942 to assess protein purity in the presence of nucleic acid contamination [1] it is now the most common method used to measure nucleic acid purity and is supported by the Beer-Lambert Law: