It seems that the DTT in NEB Buffer 4 precipitates COCl2 in the reaction solution. T-tailing of an internal control (50 ng PCR fragment, 360 bp) does not work in my hands when using NEB Buffer 4, 5mM COCl2 and NEB TdT enzyme. Here more proof from Schreiber Lab:
http://www.broadinstitute.org/chembi...ement/FAQ.html
http://www.broadinstitute.org/chembi...ement/FAQ.html
Ashes11, did you find an alternative for the NEB4 buffer?
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