Thiolated cyclodextrins

We describe how we prepared and characterized gold nanoparticles ( 3 nm in diameter) capped with thiolated cyclodextrins. The CD-capped nanoparticles are hydrophilic, and they bind compounds derivitized from ferrocene as evidenced by values measured by NMR spectroscopy. (Adapted from Liu et al., 2001)... 

The preparation and characterization of gold nanoparticles ( 3 nm in diameter) capped with thiolated cyclodextrins are described. The CD-capped... 

Y. Maeda, T. Fukuda, H. Yamamoto, H. Kitano, Regio- and Stereoselective Complex-ation by a Self-Assembled Monolayer of Thiolated Cyclodextrin on a Gold Electrode , Langmuir, 13,4187(1997)... 

This strategy was based on the supramolecular immobilization of alternating layers of HRP (either modified with 1-adamantane or P-cyclodextrin-branched carboxymethylcellulose residues) on Au electrodes coated with polythiolated P-cyclodextrin polymer. Fragoso et al. adopted a similar strategy by the immobilization of a first layer of thiolated cyclodextrin polymer on a gold electrode followed by the supramolecular capture of adamantane-modified HRP (Fig. 6)... 

A single PANl nanowire of 100 nm diameter was produced by electrochemical growth on gold electrodes modified with SAMs of thiolated cyclodextrins or 4-aminothiophenol (molecular templates) in alkanethiol [73,74]. Monomers were seeded to the surface within the isolated hydrophobic cyclodextrin cavities and initiated polymerization. While in these studies, the shape and directionality of the nanowires were not well controlled, they have demonstrated the possibility of growing individual CPNWs in selected locations using molecular templates. 

Kitano, H. Taira, Y. Inclusion of bisphenols by a self-assembled monolayer of thiolated cyclodextrins on gold electrodes. Langmuir 2002, 18, 5835-5840. 

Bollo S, Yaftez C, Sturm J, Nunez-Vergara L, Squella JA (2003) Cyclic voltammetric and scanning electrochemical microscopic study of thiolated -cyclodextrin adsorbed on a gold electrode. Langmuir 19 3365-3370... 

We saw in Section 12.3.1 the use of the cyclodextrins as mimics for transacylases, a well-understood class of enzymes that perform the task of transferring an acyl group from one substrate to another (e.g. from an ester to water). Transacylase chemistry has also been addressed by Cram,5 who used chiral corands, such as 12.11, related to 3.106 bearing thiolate nucleophiles situated above and below the plane of the macrocycle. An acyclic analogue 12.12 was also prepared for comparison. The salient features of 12.11 are shown diagrammatically in Figure 12.4. 

A similar process for preparing functional cyclodextrin nanospheres has been reported by the Harada group [25], )-Cyclodextrins were exhaustively thiolated at the lower rim and assembled around colloidal gold nanoparticles. Following assembly around the gold template the cyclodextrins were linked through the formation... 

M.T. Rojas, R. Koniger, J.R Stoddart, A.E. Kaifer, Supported Monolayers Containing Preformed Binding Sites - Synthesis and Interfacial Binding Properties of a Thiolated /S-Cyclodextrin Derivative , J. Am. Chem. Soc., 117, 336 (1995)... 

Figure 7. Schematic formulas of cyclodextrin dithiol ligand 25 and cyclodextrin thiolate clusters 26-28.

Rojas, M.T. Koniger, R. Stoddart, J.F. Kaifer, A.E. Supported monolayers containing preformed binding sites. Synthesis and interfacial binding properties of a thiolated (3-cyclodextrin derivative. J. Am. Chem. Soc. 1995, 117. 336. 

Cyclic molecules that have cavities of the right size and internal functionality are often used as an alternative to assembling the cavity around the target molecule of interest, an example of this are the cyclodextrins (CDs) which are macrocyclic compounds composed of sugar units. Kitano and Taira [45] have prepared SAMs of thiolated a-cyclodextrins on gold electrodes for the analysis of bisphenols (Fig. 14) in aqueous solutions. The selectivity of cyclodextrin was initially determined spectroscopically using methyl orange (MO) as the probe. 

Cyclodextrin polyplexes, which are called CDplexes, were prepared from polycationic thiolated amphiphilic cyclodextrin and DNA for gene delivery (see Figure ll.lC). CDplexes also can be functionalized for cellular targeting, nuclear localization and visualization purposes. ... 

Prabaharan, M. and Gong, S. 2008. Novel thiolated carboxymethyl chitosan-g-P-cyclodextrin as mucoadhesive hydrophobic drug delivery carriers. Carbohydr. Polym. 73 117-125. 

Electrochemical properties of polypyrrole films grown in LiC104 acetonitrile solution (2% water) at gold electrodes modified with thiolated /3-cyclodextrin self-assembled monolayers have been investigated. Scanning electron microscopic results show that thiolated /3-cyclodextrin acts as a molecular template to restrict the growth sites within the /3-cyclodextrin cavities (50). 

The protection afforded by functional thiols represents another effective method for the functionalization of Au (SR)m clusters. Photoresponsive Au25(SR)i8 clusters have been produced by protection with azobenzene functionalized thiolates, which give rise to isomerization reactions upon photoirradiation (Fig. 3.5) [33]. In addition, the protection of the clusters with cyclodextrin. 

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