Figure 1From: Efficient assembly of very short oligonucleotides using T4 DNA LigaseEvaluation of minimal oligonucleotide substrate requirements for T4 DNA ligase. (a) Schematic diagram of an immobilized DNA strand used in ligation assays and DNA construction. M-270 Dynabeads (Invitrogen) are attached through a streptavidin-biotin linkage to the 5' end of a double stranded DNA. The free end is designed with a variable 5' overhang, complementary to labeled oligonucleotides used in ligation. An additional BbsI restriction site and a forward primer site are included in the case of DNA construction. (b) Increasing concentrations of 5'-phosphorylated, 3'-fluorescently labeled oligonucleotide are ligated to 5 pmoles of immobilized dsDNA with a complementary overhang. Reactions were performed for one hour at 16°C and washed with TE to remove unligated substrate. Successful ligation kinetics are observed at the 5-bp duplex length (▲), but no significant ligation occurs at lengths of 4-bp (■) or 3-bp (◆).Back to article page