RESUMEN
The surfaces of silica-based sensor chips, designed for evanescent-field-coupled waveguide-mode sensors, were functionalized using various surface chemistries. The immobilization of molecular entities on the functionalized silica surfaces was monitored using various microscopic techniques (scanning electron, fluorescence, and atomic force microscopies). Further, gold nanoparticle-based signal enhancement analyses were performed with protein conjugation on different functionalized surfaces using a waveguide-mode sensor. Based on these analyses, the sensor surfaces modified with glutaraldehyde (Glu) and carbonyldiimidazole were found to be good for molecules of different sizes. In addition, it can be inferred that the Glu-modified surface may be suitable for small molecules with diameters around 5 nm owing to its surface roughness. The modified surface with carbonyldiimidazole is suitable for the direct immobilization of larger molecules especially for biomolecular assemblies without intermediate chemical modifications.
Asunto(s)
Glutaral/química , Imidazoles/química , Análisis por Matrices de Proteínas/métodos , Dióxido de Silicio/química , Estreptavidina/análisis , Microscopía Fluorescente , Tamaño de la Partícula , Análisis por Matrices de Proteínas/instrumentación , Propiedades de SuperficieRESUMEN
The air/PFO and the buried electrode/PFO interfaces have been investigated by two-color SFG spectroscopy. Due to the interface confinement effects, the planes of PFO rings are nearly parallel to the surface plane, and the optical band gaps become smaller at the interfaces than those of the bulk.
RESUMEN
Surface potential switching on gold(111) surfaces is induced by complexation/decomplexation reactions of a bipyridine (BP) derivative and palladium(II) chloride, as observed by Kelvin probe force microscopy (KFM). On the basis of the theoretical predictions, a 4-(5-phenylethynyl-2,2'-bipyridine-5'-yl-ethynyl)benzenethiol (PhBP) derivative was synthesized and used as an active monolayer to catch transition metal ions. By using the microcontact printing (CP) technique, micron-size patterned PhBP monolayers, which act as effective hosts to coordinate palladium(II) chloride, were prepared on gold(111) surfaces. The KFM signal decreases by complexation of the Pd(II) chloride in PhBP monolayers and is recovered by removal of Pd ions using an ethylenediamine solution, as confirmed by X-ray photoelectron spectroscopy. This process is reversible, indicating that the surface potential switching is realized by complexation/decomplexation of Pd(II). A CP PhBP monolayer, when it detects the target palladium ion, shows sensitivity for the picomolar level detection judged from surface potential changes in KFM measurements. The dipole moment estimated by the surface potentials is much smaller than the calculated value, indicating that mechanisms for the reduction of the surface dipole moment exist in real monolayers prepared by the CP method.
RESUMEN
We report the cloning and characterization of a cancer-associated cell membrane glycoprotein recognized by mAb NCC-3G10. The antibody showed strong reactivity to a wide variety of cancer cells, but only to a limited number of normal cells including lymphocytes, endothelial cells, and basal cells of stratified squamous epithelium. The cDNA for the antigen encodes 178 aa, which includes a putative signal sequence, a potential O-glycosylated extracellular domain, a single transmembrane domain, and a short cytoplasmic tail. Transfection of the cDNA into PLC/PRF/5 liver cancer cells resulted in reduced cell-cell adhesiveness, based on both morphology and results of Ca(2+)-dependent cell aggregation assay. In transfected cells, E-cadherin was markedly decreased at the protein level in inverse proportion to the expression level of the antigen recognized by NCC-3G10, but not at the mRNA level. Aggregation of the antigen by NCC-3G10-coated beads triggered accumulation of actin, suggesting some interplay between this antigen and E-cadherin through actin. When metastatic ability was examined in severe combined immunodeficient mice by injecting PLC/PRF/5 cells into the spleen, the transfectants formed a markedly higher number of metastatic nodules in comparison with controls. We have named this cell membrane glycoprotein, which down-regulates E-cadherin and promotes metastasis, dysadherin.