  In previous work, RAF theory has been developed as a tool for making
theoretical progress on the origin of life question, providing insight into the
structure and occurrence of self-sustaining and collectively autocatalytic sets
within catalytic polymer networks. We present here an extension in which there
are two "independent" polymer sets, where catalysis occurs within and between
the sets, but there are no reactions combining polymers from both sets. Such an
extension reflects the interaction between nucleic acids and peptides observed
in modern cells and proposed forms of early life.
