Lysine-functionalized silver nanoparticles for visual detection and separation of histidine and histidine-tagged proteins.
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.
Bae
Doo Ri
DR
Department of Chemistry and Research Institute of Natural Sciences and Environmental Biotechnology National Core Research Center, Gyeongsang National University, Jinju 660-701, Korea.
Han
Won Seok
WS
Lim
Jung Mi
JM
Kang
Sunwoo
S
Lee
Jin Yong
JY
Kang
Dongmin
D
Jung
Jong Hwa
JH
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
D008024:Ligands; D011506:Proteins; D012834:Silver; D006639:Histidine; D008239:Lysine