title: Lysine-functionalized silver nanoparticles for visual detection and separation of histidine and histidine-tagged proteins.
abstract: A new chromogenic chemosensor based on lysine-functionalized silver nanoparticles 1 was prepared and characterized by transmission electron microscopy (TEM), Fourier transform Raman, and ultraviolet-visible (UV-vis) spectroscopy. The color changes of nanoparticles 1 in the absence and the presence of metal ion were observed upon addition of various amino acids and proteins in aqueous solution. Among the various amino acids, the sensor 1 in the absence of metal ion shows a novel colorimetric sensor with capability to probe histidine and histidine-tagged proteins. On the other hand, the color changes of 1 in the presence of metal ions such as KCl or NiCl(2) did not occur with any amino acids. Therefore, the sensor 1 in the absence of metal ion responds selectively to histidine, a response which can be attributed to its aggregation induced by histidine with high numbers of electrostatic interactions. This highly selective sensor 1 allows a rapid quantitative assay of histidine to concentrations as low as 5.0 microM, providing a new tool for the direct measurement of histidine and histidine-tagged proteins in vitro system. Furthermore, we examined the effect of pH on absorbance (A(520)) of 1 in the presence of histidine (pH 4-12). The absorbance under basic conditions was higher than that under acidic or neutral conditions, in accord with the stronger aggregation of 1 with histidine by electrostatic interaction between the carboxylate anion of 1 and ammonium protons of histidine under basic conditions.
authors.affiliation: Department of Chemistry and Research Institute of Natural Sciences and Environmental Biotechnology National Core Research Center, Gyeongsang National University, Jinju 660-701, Korea.
authors.forename: Doo Ri
authors.initials: DR
authors.lastname: Bae
authors.forename: Won Seok
authors.initials: WS
authors.lastname: Han
authors.forename: Jung Mi
authors.initials: JM
authors.lastname: Lim
authors.forename: Sunwoo
authors.initials: S
authors.lastname: Kang
authors.forename: Jin Yong
authors.initials: JY
authors.lastname: Lee
authors.forename: Dongmin
authors.initials: D
authors.lastname: Kang
authors.forename: Jong Hwa
authors.initials: JH
authors.lastname: Jung
mesh_terms: D002151:Calorimetry; D006639:Histidine / Q000032:analysis* / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism; D008024:Ligands; D008239:Lysine / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D011506:Proteins / Q000032:analysis* / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism; D012834:Silver / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet
chemical_list: D008024:Ligands; D011506:Proteins; D012834:Silver; D006639:Histidine; D008239:Lysine