title: Fine tuning the pH triggers the enantiorecognition of underivatized amino acids by silver nanoparticles: a novel approach based on the focused use of solution equilibria.
abstract: Stereoselective amino acid analysis is still a challenging task. In this work, we report a study on the chiral recognition of D,L-Trp and D,L-His using L-Cys capped silver nanoparticles (AgNPs) and copper(II) ion. The AgNPs have been characterized by TEM, UV-Vis spectra and dynamic light scattering (DLS) measurements and used for chiral discrimination. In the L-Cys capped AgNPs, the α-amino and α-carboxyl groups of the surface-confined amino acid, besides showing either a negative or a neutral charge as a function of the pH, can coordinate the copper(II) ion, which in turn, binds the L- or D-amino acid present in solution forming diastereoisomeric complexes. The resulting systems have been characterized by UV-Vis spectroscopy, exploiting the zwitterionic nature of the cysteine to obtain enantiodiscrimination by a fine tuning of the pH. The analysis of the UV-Vis data by using a multiwavelength approach allows us to determine the kinetic constants ruling the processes.
authors.affiliation: Dipartimento di Scienze Chimiche, Università degli Studi di Catania, Viale Andrea Doria 6, 95125 Catania, Italy. Electronic address: acontino@unict.it.
authors.forename: Annalinda
authors.initials: A
authors.lastname: Contino
authors.affiliation: Dipartimento di Scienze Chimiche, Università degli Studi di Catania, Viale Andrea Doria 6, 95125 Catania, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Maccarrone
authors.affiliation: CNR-IMM, MATIS via S. Sofia 64, 95123 Catania, Italy.
authors.forename: Massimo
authors.initials: M
authors.lastname: Zimbone
authors.affiliation: Dipartimento di Fisica e Astronomia, Università degli Studi di Catania, Via S. Sofia 64, 95123 Catania, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Musumeci
authors.affiliation: Dipartimento di Fisica e Astronomia, Università degli Studi di Catania, Via S. Sofia 64, 95123 Catania, Italy.
authors.forename: Lucia
authors.initials: L
authors.lastname: Calcagno
authors.affiliation: CNR-IMM, Stradale Primosole 50, 95121 Catania, Italy.
authors.forename: Salvatore
authors.initials: S
authors.lastname: Pannitteri
mesh_terms: D000596:Amino Acids / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D053768:Metal Nanoparticles / Q000737:chemistry*; D046529:Microscopy, Electron, Transmission; D012834:Silver / Q000737:chemistry*; D012996:Solutions; D013056:Spectrophotometry, Ultraviolet; D013237:Stereoisomerism; D013816:Thermodynamics
chemical_list: D000596:Amino Acids; D012996:Solutions; D012834:Silver
keywords: Amino acids; Chiral analysis; Copper(II); Silver nanoparticles; Solution equilibria