Doesn't T4 work best at 15C? If i'm not in a hurry i ligate overnight too (I know most of the ligating occurs in the first hour or two). Hope it helps, Rich. -- Richard Hastings Department of Biochemistry Queens Medical Centre University of Nottingham Nottingham NG7 2UH ENGLAND 0115 9249924 Ext.44789 Fax. 0115 9422225