In article <k9mhc.131.005C5B48 at rfhsm.ac.uk>, k9mhc at rfhsm.ac.uk (vid mohan-ram)
>what is it that mg actually does in the mix?......make dna more accesible to
>polymerase or what?.......and whats the relationship between mg and dntp
AFAIR, _all_ enzymatic reactions involving trinucleotides are Mg (other
metals could substitute with efficiency that varies) dependent due to simple
reason: the substrate is Mg-NTP complex.
Affinity of divalent Me for NTPs is around 0.2-2 mM (depends) so at 2 mM Mg
practically all amount of NTPs added is a substrate.
In PCR, I'd say, DNA interactions, melting temp., etc are secondary
factors that come to play.