A Surface Mediated Supramolecular Chiral Phenomenon for Recognition of l- and d-Cysteine.

Jing Wang,Xu Xu,Kai-Xuan Fei,Shuai-Shuai Zhang,Yin-Xian Peng

doi:10.3390/nano8121027

Abstract

Chiral recognition is of fundamental importance in chemistry and life sciences and the principle of chiral recognition is instructive in chiral separation and enantioselective catalysis. Non-chiral Ag nanoparticles (NPs) conjugated with chiral cysteine (Cys) molecules demonstrate strong circular dichroism (CD) responses in the UV range. The optical activities of the l-/d-Cys capped Ag NPs are associated with the formation of order arrangements of chiral molecules on the surface of Ag NPs, which are promoted by the electrostatic attraction and hydrogen bonding interaction. The intensity of the chiroptical response is related to the total surface area of Ag NPs in the colloidal solution. The anisotropy factor on the order of 10−2 is acquired for Ag NPs with the size varying from ~2.4 to ~4.5 nm. We demonstrate a simple and effective method for the fabrication of a quantitative chiral sensing platform, in which mesoporous silica coated Ag nanoparticles (Ag@mSiO2) were used as chiral probes for recognition and quantification of Cys enantiomers.

Highlights

L-Cysteine (L-Cys), a natural proteinogenic amino acid containing a thiol moiety, plays a key role in biological systems involving protein synthesis, detoxication, and metabolic processes
Cys capped Ag NPs were synthesized by sodium borohydride (NaBH4) reduction of the aqueous solution of AgNO3 in the presence of cysteine and sodium citrate (SC)
Circular dichroism (CD) spectroscopy was utilized to characterize the chiroptical properties of the synthesized Cys capped Ag NPs

Summary

Introduction

L-Cysteine (L-Cys), a natural proteinogenic amino acid containing a thiol moiety, plays a key role in biological systems involving protein synthesis, detoxication, and metabolic processes. An abnormal level of L-Cys in the human body is a risk factor for various human diseases. D-Cys is an essential chiral intermediate for pharmaceuticals. It is a crucial intermediate for the synthesis of cefminox sodium, a broad-spectrum, third-generation cephalosporin antibiotic. D-Cys has been shown to be a powerful inhibitor of some bacteria, such as Escherichia coli [3]. Developing a powerful new method for accurate identification and quantification of Cys is critically important in the fields of biological systems, pharmaceutical sciences, and biotechnology

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Conclusion