Whereas T4 DNA Ligase is sensitive to the presence of salt in the reaction, Salt-T4 DNA Ligase can tolerate salt concentrations up to 500 mM for the ligation of cohesive ends, or up to 150 mM for the ligation of blunt ends. Therefore, Salt-T4 DNA Ligase should be the enzyme of choice if the ligation is to be performed in a salt-containing buffer (e.g., NEBuffer 3.1) or if salt carryover (from DNA preparations) is a concern. Please note in the presence of PEG (1X StickTogether™ DNA Ligase Buffer), DNA in a high salt solution will precipitate, inhibiting ligation. If you want to ligate DNA in the presence of salt over 100 mM, we recommend the use of 1X T4 DNA Ligase Buffer.