title: Visual chiral recognition of tryptophan enantiomers using unmodified gold nanoparticles as colorimetric probes.
abstract: A simple protocol to distinguish enantiomers is extremely intriguing and useful. In this study, we propose a low-cost, facile, sensitive method for visual chiral recognition of enantimers. It is based on the inherent chirality of gold nanoparticles (AuNPs), and the unmodified AuNPs are used as chiral selector for D- and L-Tryptophan (Trp). In the presence of D-Trp, an appreciable red-to-blue color change of AuNPs solution can be observed, whereas no color change is found in the presence of L-Trp. The method can be used to detect D-Trp in the range of 0.2-10 μM, and the limit of detection is 0.1 μM. The chiral assay described in this work is easily readout with the naked eye or using a UV-vis spectrometer. Furthermore, the AuNPs can selectively adsorb D-Trp, and simple centrifugation can allow the precipitation of D-Trp with AuNPs and leave a net excess of the other enantiomer in solution, thus resulting in enantioseparation. In this method, AuNPs do not need any labeling or modifying with chiral molecules. The method is more attractive because of its high sensitivity, low cost, ready availability and simple manipulation.
authors.affiliation: Key Laboratory of Analytical Chemistry for Life Science of Shaanxi Province, School of Chemistry & Chemical Engineering, Shaanxi Normal University, Xi'an 710062, China.
authors.forename: Lin
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Analytical Chemistry for Life Science of Shaanxi Province, School of Chemistry & Chemical Engineering, Shaanxi Normal University, Xi'an 710062, China.
authors.forename: Chunli
authors.initials: C
authors.lastname: Xu
authors.affiliation: Key Laboratory of Analytical Chemistry for Life Science of Shaanxi Province, School of Chemistry & Chemical Engineering, Shaanxi Normal University, Xi'an 710062, China.
authors.forename: Cunwei
authors.initials: C
authors.lastname: Liu
authors.affiliation: Key Laboratory of Analytical Chemistry for Life Science of Shaanxi Province, School of Chemistry & Chemical Engineering, Shaanxi Normal University, Xi'an 710062, China. Electronic address: libx29@hotmail.com.
authors.forename: Baoxin
authors.initials: B
authors.lastname: Li
mesh_terms: D003124:Colorimetry; D006046:Gold / Q000737:chemistry* / Q000191:economics; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000191:economics; D010316:Particle Size; D013237:Stereoisomerism; D013499:Surface Properties; D014364:Tryptophan / Q000032:analysis* / Q000191:economics
chemical_list: D006046:Gold; D014364:Tryptophan
keywords: Chiral recognition; Colorimetric probes; Gold nanoparticles; Visual detection