Abstract
Molecular recognition is one of the most important phenomena in Chemistry and Biology. Here we present a new way of enantiomeric molecular recognition using intrinsically chiral semiconductor nanocrystals as assays. Real-time confocal microscopy studies supported by circular dichroism spectroscopy data and theoretical modelling indicate an ability of left-handed molecules of cysteine and, to a smaller extent, histidine and arginine to discriminate between surfaces of left- and right-handed nanocrystals.
Highlights
Most interactions between biomolecules involve molecular recognition, a natural mechanism that enables in biological systems such important processes as metabolism, immuno responses, information processing, and others
Through an interplay of Density Functional Theory (DFT) calculations, real-time photoluminescence (PL) measurements and Circular Dichroism (CD) spectroscopy data we observe that molecules of l-cysteine preferentially adsorb on the surface of d-nanocrystals since the formation of d-l heterocomplexes is energetically favoured over the formation of l-l homocomplexes
To check if the molecules of cysteine can enantioselectively interact with the chiral surfaces of the QDs during phase transfer in solution, we chose CdSe QDs synthesized via a standard hot injection procedure and capped
Summary
Quantum Dots received: 12 October 2015 accepted: 21 March 2016 Published: 11 April 2016. Since observation of molecular recognition at the nano/bio interface requires an enantioenriched sample of the QDs capped with achiral ligands, we used a two-step procedure of preliminary preparation of our samples: (1) separation of the nanocrystals enantiomers, (2) substitution of the chiral ligands with achiral ones. If molecular recognition of cysteine on the QD surface promotes the separation of the nanocrystal enantiomers during the chiral phase transfer, the heterocomplexes and homocomplexes should form with different efficiency. We compared the extent of complexing reactions for the heterocomplexes d-l and homocomplexes l-l of the QDs and l-cysteine In this experiment we used the enantioenriched ensembles of the DDT-capped QDs from the second step, the concentrations and volumes of QDs solutions were equalized before the phase transfer (for details see Methods in Supplementary Information, page S3).
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