Gold thiol-modified

In addition to the use of cyclohexane, dimethylformamide (DMF) was used as a good solvent. So as to pick up the thiol-modified terminal, gold-coated cantilevers were used. The nominal values of their spring constant ki were 30 or 110 pN nm . A typical force-extension curve measured in cyclohexane is shown in Figure 21.4. The solvent temperature was kept at about 35°C, which corresponded to its temperature for PS chains. Thus, a chain should behave as an ideal chain. The slope at the lowest extension limit (dashed line in Figure 21.4) was 1.20 X lO" N m . ... 

Kobayashi et al. [91] recently synthesized a phase that is comprised of thiol-modified gold-coated polystyrene particles. An increase in the selectivity of the anthracene-phenanthrene pair was observed on the Cis-Au particle when compared with a traditional monomeric Cis phase with a surface coverage of 3.0 p,mol/m. This isomer pair is not the ideal choice for the determination of shape selectivity however, this synthetic technique should in general lead to dense, ordered phases that are anticipated to yield relatively highly shape-selective chromatographic separations. 

Kobayashi, K., Kitagawa, S., and Ohtani, H., Development of capillary column packed with thiol-modified gold-coated polystyrene particles and its selectivity for aromatic compounds, J. Chromatogr. A, 1110, 95, 2006. 

Recent studies have indicated that the base composition of the OND can affect the efficiency of its ability to bind to a surface. This is most probably a consequence of the different affinity that each base shows for any particular surface [21-24], This has been clearly demonstrated in adsorption studies using homo-ONDs (unmodified and thiol modified) onto gold surfaces [23,24]. It was observed that unmodified homo-ONDs adsorb on gold with relative affinities A > C > G > T (Figs. 5 and 6). When performing competitive adsorption experiments with unmodified and thiol modified ONDs,... 

Fig. 6 Average coverage of unmodified hatched bars) and thiol-modified solid bars) homo-OND films after one hour adsorption onto gold surfaces in 1M KH2PO4. The ratio between both bars indicates the ability of nonspecific binding to interfere with specific thiol binding for each sequence, i.e. the relative strength of nonspecific adsorption for each OND [24]...

DNA arrays have been also generated by Dip-Pen Nanolithography (DPN) [80]. DPN involves the transfer of NAs directly from a coated Atomic Force Microscope (AFM) tip to the substrate of interest by virtue of direct molecular diffusion. Using this technique, thiol-modified ONDs have been patterned onto gold substrates and acrylamide-modified ONDs onto glass sHdes that were previously modified with mercaptopropyltrimethoxysilane. Feature sizes ranging from many micrometers to less than 100 nanometers could be obtained. The deposition of two different OND sequences onto the same substrate has also been reported [80], but the appHcation of this principle to the fabrication of high-density arrays remains to be addressed. 

The two-step synthesis of CdS on sulfur or thiol modified polycrystalhne gold electrode was described [160]. The morphologies of CdS formed in both cases and the electrochemical behavior of these compounds were compared. 

Taton et al. used gold nanoparticles functionalized with thiol-modified oligonucleotides to detect the presence of its complementary sequence hybridized on a transparent substrate (Fig. 13.9).16 In comparison to conventional fluorophore probes, this technique is three times more sensitive in discriminating an oligonucleotide sequence with a single basepair mismatch. In addition, signal amplification by reduction of silver ions on the nanoparticles drastically increased the sensitivity of... 

One of the most common metal surfaces that oligonucleotides have been attached to is gold, which is readily conjugated with thiol-modified materials. 

DNA adsorbed on a glassy carbon electrode was also used as an effective electron promoter enabling electron transfer via hopping conduction through electrode/base pair/cytochrome c by Ikeda et al. [128]. Gold electrodes modified with short oligonucleotides inunohilized via thiol chemisorption were described hy Lisdat et al. [129] to study the promotion of electron transfer to cytochrome c. 

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