Ligations using Promega T4 DNA Ligase
** See Product Info Sheet for more information
Use a 1:1, 1:3, or 3:1 molar ratio of vector:insert DNA when cloning a fragment into a plasmid vector. These ratios will vary with other types of vectors, for example, cDNA and genomic cloning vectors. The following example illustrates the conversion of molar ratios to mass ratios for a 3.0kb plasmid and a 0.5kb insert DNA fragment.
ng of vector x kb size of insert x molar ratio of insert/vector = ng of insert
kb size of vector
How much 0.5kb insert DNA should be added to a ligation in which 100ng of 3kb vector will be used? The desired vector:insert ratio will be 1:3.
100ng vector x 05.kb insert x 3/1 = 50ng insert
The following ligation reaction of a 3kb vector and a 0.5kb insert DNA uses a 1:1 vector: insert ratio. Typical ligation reactions use 100-200ng of vector DNA.
Vector DNA 100ng
Insert DNA 17ng
Ligase 10X buffer 1ul
T4 DNA Ligase (Weiss units) 0.1-1u
Nuclease free water to 10ul
Room temperature for 3 hours, or
4¡C overnight, or
15¡C for 4-18 hours.