Denaturing loading buffer

0.3% bromophenol blue

0.3% xylene cyanol

12 mM EDTA, in formamide

The formamide may have to be deionized prior to its addition to the loading buffer. If any yellow color is present, deionize the formamide by stirring on a magnetic stirrer with Dowex XG8 mixed bed resin for 1 hour and filtering it twice through Whatman No. 1 paper. Store the deionized formamide in small aliquots under nitrogen at −70°C.