Exactly the same happens with the the cyclic peptides synthesised by Ghadiri's group. This time, the R and S forms are created by coupling different amino acids, and not simply taking a racemic mixture of each. The monomeric structures of these peptides are shown below. Pirkle reagent, these cyclic peptides form an infinite chain, this time with the rings interacting via hydrogen bonds by stacking on top of each other. This results in alignment of the central cavities to form a tube or channel, filled with water molecules.
Adjacent tubes interact via dispersion forces aligning the lipophilic rims.
When added to a culture of penicillin-resistant bacteria, these nanobiotics are thought to insert into the lipophilic cell membrane. Here, surrounding solvating water is removed, and the peptide rings instead stack into the ziggurat, in a manner analogous to the crystal structures shown above. By altering the precise nature of the amino acids comprising the cyclic peptide, various specific nanobiotics can be engineered. Unlike conventional anti-biotics therefore, these substances do not function chemically but in essence mechanically, at a true nanomolecular scale. J. Sanchez-Quesada, M. R. Ghadiri, H. Bayley, and O. Braha, J. Am.