Regensburg 2007 – scientific programme
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O: Fachverband Oberflächenphysik
O 58: Metal Substrates: Adsorption IV
O 58.9: Talk
Thursday, March 29, 2007, 17:45–18:00, H39
Tracking the chiral recognition of adsorbed dipeptides at the single molecule level — •Giovanni Costantini1, Magalí Lingenfelder1, Giulia Tomba2, Lucio Colombi Ciacchi3, Alessandro De Vita2, and Klaus Kern1 — 1MPI-FKF, Stuttgart, Germany — 2Physics Department, King's College London, UK — 3Fraunhofer IWM, Freiburg, Germany
We report on the direct observation of chiral recognition events of diphenylalanine adsorbed on Cu(110) by scanning tunneling microscopy (STM). We monitor the self-organization of co-deposited di-L-phenylalanine (L-Phe-L-Phe) and its stereoisomer D-Phe-D-Phe and rationalise the observed steps of the system's dynamical evolution using first principles and classical molecular dynamics techniques.
We demonstrate that the adsorbed dipeptides must undergo both a conformational change and a chemical rearrangement (into a zwitterionic form) in order to assemble into stable supramolecular structures. The process is successfully completed if the approaching dipeptides have the same chirality, and fails otherwise, so that the final structures are in all cases strictly homochiral.
Our analysis shows that a static three-point-model is in general not sufficient for a complete description of chiral recognition. We prove the importance of mutually induced conformational changes in the chiral recognition process, thereby visualizing at the single molecule level a 50 years old prediction of L. Pauling.