Tunneling through bonds

Selzer Y, Salomon A, Cahen D (2002) The importance of chemical bonding to the contact for tunneling through alkyl chains. J Phys Chem B 106 10432-10439... 

It is beyond the scope of this text to continue the discussion of Marcus theory. Qualitatively, the student should understand that electrons must find a path through the protein from the donor species to the acceptor. This may take place through bonds as outlined above or through electron tunneling events in which electrons travel through space between orbitals of the donor species to the acceptor species. Chapter 6 of reference 13 presents a clear explanation for further reading. 

The peptidyl transferase centre of the ribosome is located in the 50S subunit, in a protein-free environment (there is no protein within 15 A of the active site), supporting biochemical evidence that the ribosomal RNA, rather than the ribosomal proteins, plays a key role in the catalysis of peptide bond formation. This confirms that the ribosome is the largest known RNA catalyst (ribozyme) and, to date, the only one with synthetic activity. Adjacent to the peptidyl transferase centre is the entrance to the protein exit tunnel, through which the growing polypeptide chain moves out of the ribosome. 

What of the factors that involve quantum mechanics They concern the electron overlap of bond orbitals and the effect of tunneling through a barrier (Chapter 9). 

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