title: Zinc-histidine as nucleation centers for growth of ZnS nanocrystals.
abstract: Histidine is a chelator of zinc, most notably in zinc-finger proteins (zinc coordinated by cysteine and histidine) and in hyperaccumulator plants. Sulfide incorporation into molecules containing metal-cysteinyl complexes has been shown to occur in vivo in certain yeasts, leading to enhanced metal tolerance. Demonstrated here for the first time is incorporation of sulfide into zinc-histidine, resulting in histidine-ZnS nanocrystals (NCs) having unique optical properties. Sulfide complexation occurred optimally at alkaline pH into zinc-(histidine)2 species, and UV/Vis absorption maxima were red-shifted as increasing sulfide addition occurred. Intermediate sulfide concentrations led to multiple, thermodynamically preferred NC species within a sample. Fluorescence of histidine-ZnS NCs was greater than ZnS prepared previously with cysteinyl peptides. Transmission electron microscopy and selected-area electron diffraction indicated hexagonal ZnS crystals having an average size of 4.2 nm. A photocatalytic application of histidine-ZnS NCs was shown by efficient degradation of p-nitrophenol and paraquat in the presence of UV irradiation.
authors.affiliation: Department of Neuroscience, University of California, Riverside 92521, USA.
authors.forename: R
authors.initials: R
authors.lastname: Kho
authors.forename: L
authors.initials: L
authors.lastname: Nguyen
authors.forename: C L
authors.initials: CL
authors.lastname: Torres-Martínez
authors.forename: R K
authors.initials: RK
authors.lastname: Mehra
mesh_terms: D001665:Binding Sites; D002614:Chelating Agents / Q000737:chemistry; D003460:Crystallization; D006639:Histidine / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D008854:Microscopy, Electron; D009942:Organometallic Compounds / Q000737:chemistry; D010084:Oxidation-Reduction; D010777:Photochemistry; D013050:Spectrometry, Fluorescence; D013053:Spectrophotometry; D013056:Spectrophotometry, Ultraviolet; D013440:Sulfides / Q000737:chemistry*; D015032:Zinc / Q000737:chemistry*; D017967:Zinc Compounds / Q000737:chemistry*
chemical_list: D002614:Chelating Agents; D009942:Organometallic Compounds; D013440:Sulfides; D017967:Zinc Compounds; C052388:zinc-histidine complex; D006639:Histidine; D015032:Zinc; C031238:zinc sulfide