Regulation of inter- and intramolecular ligation with T4 DNA ligase in the presence of polyethylene glycol.

Polyethylene glycol (PEG) stimulates ligation with T4 DNA ligase. In 10% (w/v) PEG 6,000 solutions, only intermolecular ligation is enhanced by monovalent cations, while both inter- and intramolecular ligation occur without their presence. Similar stimulation was also caused by divalent cations or polyamines in the PEG 6,000 solutions. Such properties of the ligase could be applied to control the extent of inter- and intramolecular ligation. Ligation with cations or polyamines in 10% PEG 6,000 solutions was effective for intermolecular ligation. Ligation without cations or polyamines in 6.0% to 10% PEG 6,000 solutions was effective for intramolecular ligation.