  We study the long-range electron and energy transfer mediated by a polaron on
an $\alpha$-helix polypeptide chain coupled to donor and acceptor molecules at
opposite ends of the chain. We show that for specific parameters of the system,
an electron initially located on the donor can tunnel onto the $\alpha$-helix,
forming a polaron which then travels to the other extremity of the polypeptide
chain where it is captured by the acceptor. We consider three families of
couplings between the donor, acceptor and the chain, and show that one of them
can lead to a 90\% efficiency of the electron transport from donor to acceptor.
We also show that this process remains stable at physiological temperatures in
the presence of thermal fluctuations in the system.
