A thermotolerant variant of T4 DNA Ligase, Hi-T4 DNA Ligase catalyzes the formation of a phosphodiester bond between juxtaposed 5 phosphate and 3 hydroxyl termini in duplex DNA or RNA and is designed to function at higher temperatures than wild type T4 DNA Ligase. Hi-T4 DNA Ligase will join blunt end and cohesive end termini as well as repair single-stranded nicks in duplex DNA, RNA or DNA/RNA hybrids at temperatures as high as 50C.