Gold nanoparticles mediation

Mann and coworkers proposed a unique method to prepare nanohybrids of mesoporous silica and gold nanoparticles mediated by programmed DNA hybridization, as illustrated in Figure 4.21 [186], MCM-41 nanoparticles were first functionalized with a 3 -amino-terminated 12-base single strand oligonucleotide... 

K. K. Sandhu, C. M. McIntosh, J. M. Simard, S. W. Snuth and V. M. Rotello, Gold nanoparticle-mediated transfection of mammalian cells. Bioconjug. Chem., 13,3-6 (2002). 

Gold nanoparticle-mediated transfection of mammalian cells. Bioconjugate Chemistry, 13, 3-6. 

Bates et al. reported the construction and characterization of a gold nanoparticle wire assembled using Mg -dependent RNA-RNA interactions for the future assembly of practical nanocircuits [31]. They used magnesium ion-mediated RNA-RNA loop-receptor interactions, in conjunction with 15 nm or 30 nm gold nanoclusters derivatized with DNA to prepare self-assembled nanowires. A wire was deposited between lithographically fabricated nanoelectrodes and exhibited non-linear activated conduction by electron hopping at 150-300 K (Figure 16). 

Table 1. Conditions for the growth of gold nanoparticles via seed (S)-mediated method.

Figure 17.15 The small carboxylate-alkyne compound 4-pentynoic acid can be used to modify proteins at their amine groups with EDC to provide alkyne sites for click chemistry-mediated conjugation. The subsequent reaction of an azido-PEG-modified gold nanoparticle with the alkynyl-protein in the presence of Cu1+ yields the triazole-coupled protein.

Carbohydrates not only interact with protein receptors, but also with other carbohydrates and nucleic acids. Recently, gold nanoparticles (GNPs) have been prepared as new multivalent tools that mimic carbohydrate presentation on the cell surface. Using this tool, a weak calcium-mediated carbohydrate-carbohydrate interaction has been detected using NMR, employing... 

Jana, N.R., Gearheart, L., and Murphy, C.J., Evidence for seed mediated nucleation in the chemical reduction of gold salts to gold nanoparticles, Chem. Mater., 13, 2313, 2002. 

The formation of Au-OHad or surface oxides on gold in alkaline electrolyte was in fact proposed to explain some of the electrocatalytic properties observed for a gold electrode (e.g., incipient hydrous oxide/adatom mediator model ). Our previous measurement of the interfacial mass change also indicated the formation of Au oxides (AU2O3, AuOHorAu(OH)3) on gold nanoparticle surfaces. A detailed delineation of the catalytic mechanism is part of our on-going work. 

Figure 6.6 (a) Schematic representation of PEI-mediated assembly of gold nanoparticles. 

Scheme 2 Schematic of a seed-mediated, surfactant-assisted gold nanorod synthesis. The small black dots represent Ag+ ions, the orange stars are CTAB molecules forming micelles, the yellow circles and green squares are AuCLf and AuC12 , respectively, forming complexes with the CTAB micelles. Freshly-prepared gold nanoparticle seeds are injected into the growth solution in the final step of the nanorod synthesis [166]. (Copyright 2008, American Chemical Society)...

Jana, N. R., Gearheart, L. Murphy, C. J. Seed-mediated growth approach for shape-controlled synthesis of spheroidal and rod-like gold nanoparticles using a surfactant template. Adv. Mater. (Weinheim, Ger.) 13, 1389-1393 (2001). 

Historically, OTEs were used to investigate complex redox reactions including mediated reactions of enzymes (-> mediators). Recently OTEs have been extensively applied to study spectroelectrochemical properties of thin films of electrochromic materials (- elec-trochromic devices, -> electrochromism), and various chromic deposits including bioelectrochemical materials (e.g. - enzymes) or network films of gold -> nanoparticles. They are often used in -> photoelectrochemistry as electrode materials. 

Fig. 8 a Schematic illustration of PEl-mediated assembly of gold nanoparticles, b Hexagonal and c cubic packing arrangements of nanoparticles through transmission electron microscopy (TEM). Reprinted (in part) with permission from [82]... 

Figure 11.2 Left Schematic illustrating use of double stranded DNA to mediate distance between fluorophore and nanoparticle surface. Middle Symbols show the average values of experimentally measured fluorescence lifetime. The last measurement was done in the absence of gold nanoparticles as a calibration. The dashed and dashed-dotted curves display the calculated fluorescence lifetime for the molecular dipole oriented radially or tangentially with respect to the gold nanoparticle. Right Fluorescence signal corresponding to the measurements presented the middle panel. Reprinted with permission from reference [22]. (2007) American Chemical Society.

Direct electrical communication between enzyme aetive sites and electrodes may also be facilitated by the nanoscale morphology of the electrode. The modification of electrodes with metal nanoparticles allows the tailoring of surfaees with features that can penetrate close enough to the enzyme aetive site to make non-mediated electron transfer possible. Electrodes modified by unaggregated 12 nm diameter gold nanoparticles have been found to have the eorrect morphology to allow direct electron transfer between the cytochrome c active site and the eleetrode [41]. Elec-... 

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