Lysine-Functionalized Silver Nanoparticles for Visual Detection and Separation of Histidine and Histidine-Tagged Proteins

• Published in: Langmuir Vol. 26; no. 3; pp. 2181 - 2185
• Main Authors: Bae, Doo Ri, Han, Won Seok, Lim, Jung Mi, Kang, Sunwoo, Lee, Jin Yong, Kang, Dongmin, Jung, Jong Hwa
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 02.02.2010
• Subjects: Calorimetry; Chemistry; Colloidal state and disperse state; Devices and Applications: Sensors, Fluidics, Patterning, Catalysis, Photonic Crystals; Exact sciences and technology; General and physical chemistry; Histidine - analysis; Histidine - chemistry; Histidine - isolation & purification; Histidine - metabolism; Ligands; Lysine - chemistry; Metal Nanoparticles - chemistry; Models, Molecular; Molecular Conformation; Physical and chemical studies. Granulometry. Electrokinetic phenomena; Proteins - analysis; Proteins - chemistry; Proteins - isolation & purification; Proteins - metabolism; Silver - chemistry; Spectrophotometry, Ultraviolet; Surface physical chemistry; Separation; Nanoparticle; Electrostatic interaction; Metal ion; Transition metal; Protein; Aggregation; Assay; Silver; Absorbance; Transmission electron microscopy; Lysine; Aminoacid; Carboxylate; Proton; pH; Aqueous solution; Ultraviolet visible spectrometry
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/la9026865

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 NiCl2 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 μM, 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.