A real-time assay for monitoring nucleic acid cleavage by quadruplex formation

Direct and straightforward methods to follow nucleic acid cleavage are needed. A spectrophotometric quadruplex formation assay (QFA) was developed, which allows real-time monitoring of site-specific cleavage of nucleic acids. QFA was applied to study both protein and nucleic acid restriction enzymes, and was demonstrated to accurately determine Michaelis-Menten parameters for the cleavage reaction catalyzed by EcoRI. QFA can be used to study the mechanisms of protein-nucleic acid recognition. QFA is also a useful tool for dissecting individual nicking rates of a double-stranded cleavage.