Supramolecular probes

Recently, in 2010, an effort was made by Kalenius to create a supramolecular probe with improved selectivity and effectiveness for saccharide binding." On the basis of the results from previous work by Krtil and coworkers, the Kalenius group used bile acid—a steroid derivative—as the porphyrin appendage with the goal of effecting saccharide-specific molecular recognition." The attachment of two bile add arms to a porphyrin core creates a host, 17—a system expected to be capable of... 

Moreover, peptide amphiphiles have been revealed as promising candidates for MRI and biomaterial scaf-folds." " Gd " "-based MR contrast agents have been covalently attached to peptide amphiphile backbones, which noncovalently self-assemble into nanofibers. The position of the Gd " " complex on the backbone was investigated in order to optimize relaxivity. These supramolecular probes exhibited high relaxivity values (up to 21.5 mM s ) and significant MR contrast enhancement was observed in vitro in comparison to a Gd-DTPA standard. Gd +-modified peptide amphiphiles have potential application in nonin-vasive tracking of biomaterial implants in vivo. 

Kikuchi, Y., Kobayashi, K., and Aoyama, Y. (1992) Complexation of chiral glycols, steroidal polyols, and sugars with a multibenzenoid, achiral host as studied by induced circular-dichroism spectroscopy exciton chirality induction in resorcinol-aldehyde cyclotetramer and its use as a supramolecular probe for the assignments of stereochemistry of chiral guests, J. Am. Chem. Soc. 114, in press. 

Kikuchi, Y., Kobayashi, K., Toi, H., and Aoyama, Y. Supramolecular probing of the absolute configuration of chiral monools via host-guest complexation, to be published. 

Reference [33] describes recent progress on cyanine probes that bind noncova-lently to DNA, with a special emphasis on the relationship between the dye structure and the DNA binding mode. Some of the featured dyes form well-defined helical aggregates using DNA as a template. This reference also includes spectroscopic data for characterizing these supramolecular assemblies as well as the monomeric complexes. 

Xu H, Xu X, Dabestani R et al (2002) Supramolecular fluorescent probes for the detection of mixed alkali metal ions that mimic the function of integrated logic gates. J Chem Soc Perkin Trans 2 636... 

Siering C, Kerschbaumer H, Nieger M et al (2006) A supramolecular fluorescence probe for caffeine. OrgLett 8 1471-1474... 

Fluorescence is also a powerful tool for investigating the structure and dynamics of matter or living systems at a molecular or supramolecular level. Polymers, solutions of surfactants, solid surfaces, biological membranes, proteins, nucleic acids and living cells are well-known examples of systems in which estimates of local parameters such as polarity, fluidity, order, molecular mobility and electrical potential is possible by means of fluorescent molecules playing the role of probes. The latter can be intrinsic or introduced on purpose. The high sensitivity of fluo-rimetric methods in conjunction with the specificity of the response of probes to their microenvironment contribute towards the success of this approach. Another factor is the ability of probes to provide information on dynamics of fast phenomena and/or the structural parameters of the system under study. 

Tovar JD, Claussen RC, Stupp SI. Probing the interior of peptide amphiphile supramolecular aggregates. J Am Chem Soc 2005 127 7337-7345. 

Organizational characteristics of surface-active molecules have been studied by several researchers due to their applications in many areas such as personal care, polymerization, catalysis, drug delivery, separation and purification, enhanced oil recovery and lubrication. The structure of supramolecular organized assemblies formed in different solvents, when a critical concentration is exceeded, determines their properties such as solubilization [1-3], catalysis [1,4-6], adsorption [7-11] and flocculation [12,13]. As such, many techniques have been used to determine their structural properties. In this paper, the results obtained using fluorescence probing for properties of assemblies in solution and at solid-liquid interfaces are discussed in detail after a brief review of relevant assemblies formed by them. 

Another well-represented category was that of self-assembled monolayers (SAMS) and other supramolecular systems. The experiments on the SAMS included studies of the surface pKa of one system (110), the kinetics and thermodynamics of the self-assembly process (111), and the characterization of the SAM surface by study of solution contact angles (112). The experiments on supramolecular systems included studies on chemical equilibria in such systems (113, 114, 115), the kinetics of inclusion phenomena (116), and the use of solvatochromic probes in studying inclusion phenomena (117). 

A similar supramolecular approach, in which both n-n stacking stacking of pyrene on the SWNT surface and alkyl ammonium-crown ether interactions were used in the self-assembly process of a fullerene derivative with SWNTs, was recently reported (Scheme 9.22).72 The nanohybrid integrity was probed with various spectroscopic techniques, , and electrochemical measurements. Nanosecond transient absorption studies confirmed electron transfer as the quenching mechanism of the singlet excited state of C60 in the nanohybrid resulting in the formation of SWNT"1"/ Pyr-NH3 + /crown- charge-separated state. 

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