Fluorescence\nand Circular Dichroism Dual-Mode Probe\nfor Chiral Recognition of Tyrosine and Its Applications in Bioimaging

Chiral\namino acids (AAs) are essential in metabolism and understanding\nphysiological processes, and they could be used as biomarkers for\nthe diagnosis of different diseases. In this study, chiral Cdots@Van\nwere prepared by postmodifying an achiral Cdots core with vancomycin\nfor recognizing and determining the enantiomeric excess (ee) of tyrosine\n(Tyr) enantiomers. The fluorescence response of Cdots@Van is based\non an “on–off” strategy, with different quenching\npercentages for d- and l-tyrosine. Interestingly,\nthe circular dichroism (CD) spectrum of Cdots@Van responded to only\none form of Tyr enantiomer, specifically d-Tyr, and remained\nnearly unchanged upon the addition of l-Tyr. Quantum mechanical\n(QM) calculations were in excellent agreement with the experimental\nresults, confirming the stronger binding affinity of Cdots@Van for d-Tyr compared to l-Tyr. We further investigated the\nchiral recognition ability of the interconnected vancomycin particles,\nwhich was synthesized using the EDC/NHS coupling reaction between\nvancomycin molecules without a Cdots core. Surprisingly, unlike free\nvancomycin molecules, interconnected vancomycin displayed an enantiomeric\nrecognition ability by CD spectroscopy, similar to what was observed\nfor Cdots@Van. Crucially, this chiral probe has been successfully\nutilized for cell imaging applications.