Supramolecular Covalent Anchoring

Abstract Artificial metalloenzymes can be created by incorporating an active metal catalyst precursor in a macromolecular host. When considering such artificial metalloenzymes, the first point to address is how to localize the active metal moiety within the protein scaffold. Although a covalent anchoring strategy may seem most attractive at first, supramolecular anchoring strategy has proven most successful thus far. 

Adenosine nucleotides were also electrochemically detected with ICSs. " For these purposes, gold electrodes were functionalized by covalent anchoring of macrocyclic polyamines. [Ru(NFl3)6] was used as redox probe for the voltammetric detection of ATP, ADP, and AMP. The response mechanism originates from the inhibition of the redox reaction of the marker upon formation of supramolecular complexes between macrocyclic polyamine hosts and adenine nucleotide guests at the surface of the electrode. 

Besides the preparation of glyconanotube conjugates by supramolecular interactions, another synthetic pathway commonly used involved covalent attachment of the saccharidic units on the CNT scaffolds. The progress recently recorded concerning the derivatization of unfunctionalized CNTs, allowing introduction of suitable anchoring functions at their surface, are the basis of this synthetic alternative.255... 

In terms of structural chemistry, liposomes are supramolecular aggregates. A drug will also associate with the liposome by via non-covalent binding. With modified and unmodified ODNs, liposomes have become a particularly promising approach, aided by the fact that specific ODN-modifications may also be used specifically to influence drug-liposome interaction. Thus, base-modified cholesterol derivatives have been developed to act as specific anchor points for ODNs in liposomal formulations [397-408], Application of pH-sensitive liposomes made from DOPE/OA [409] or DOPE/OA/CHOL [410] has also been suggested. As a first important effect of liposome formulation, protection of ODNs from extracellular nucleases has been observed [411-413]. Use of such formulations has proven to be a valid method for cellular internalization in cultured cell lines, an effect which has been reviewed by a number of authors [414,415]. 

The covalent approach towards DNA-based catalysis involves direct attachment of the catalytically active metal complex to the DNA via a covalent bond. The presumed advantage of this approach over the supramolecular variant is the greater control over both the geometry around the metal center and the exact microenvironments (i.e., the DNA sequence) in which the metal complex is located. So far, two reports have been published in which transition metals were anchored to deoxyribonucleotides via covalently linked phosphine ligands (Fig. 15). 

Recently, we have shown that the supramolecular approach (a non-covalent two-fold extra-ligation in conjunction with Zn-porphyrin chemical dimers and trimers) can be successfully employed to create a variety of multiporphyrin structures capable of the fast effective intra-complex energy migration and photoinduced electron transfer [5]. Following this self-assembly principle we have succeeded to anchor in pyridyl substituted porphyrin molecules on CdSe/ZnS QD surfaces. In this case, CdSe/ZnS QDs show luminescence quenching induced by dynamic and/or static interactions between QD and porphyrins depending critically on sample stability, temperature and solvent polarity [6]. The general focus of this contribution is devoted to demonstrate the... 

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