Patent ID: 7781573

Claim:
A method of purifying or separating full length nucleic acids of about 40 bases or more and bearing a 5′-hydrophobic end from a crude solution containing at least two kind of contaminants, the method comprising: diluting the solution with a binding buffer and passing the diluted solution through a series of n columns packed with reversed-phase sorbents having differing pore sizes, starting with column(1) and proceeding through column(n), n being a finite integer greater than one; wherein one kind of the said contaminants includes truncated nucleic acid without a 5′-hydrophobic end and another kind of the said contaminants includes truncated nucleic acid bearing a 5′-hydrophobic end; each of column(1) through column(n−1) has a sorbent with a pore size range selected to preferentially bind a range of sizes of the truncated nucleic acid bearing a 5′-hydrophobic end; and column(n) has a sorbent with a pore size range selected to preferentially bind the full length nucleic acid.