Thanks for your letter of June 18th. If I had known of Heppel's paper at the time I wrote our note, you can be sure I
should have quoted it together with the other papers listed in my publication. As you certainly know, it is almost impossible
to keep track of the literature at the present time.
I have not yet had time to read this paper, but I am wondering whether the situation which we describe is not different from
the one prevailing when you deal with a ribopolymer and a mononucleotide precursor in the polymerization reaction. In the
latter case, even if polynucleotide phosphorylase is not a template-requiring enzyme, the ribopolymer may act as a sort of
template. For such reactions, there are, of course, many precedents in the polymerase systems.