Investigation of Guanosine-Quartet Assemblies by Vibrational and Electronic Circular Dichroism Spectroscopy, a Novel Approach for Studying Supramolecular Entities
✍ Scribed by Vladimír Setnička; Marie Urbanová; Karel Volka; Sreenivasachary Nampally; Jean-Marie Lehn
- Publisher
- John Wiley and Sons
- Year
- 2006
- Tongue
- English
- Weight
- 237 KB
- Volume
- 12
- Category
- Article
- ISSN
- 0947-6539
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✦ Synopsis
Abstract
The self‐assembly of guanosine‐5′‐hydrazide G‐1 in D~2~O, in the presence and absence of sodium cations, has been investigated by chiroptical techniques: electronic (ECD) and the newly introduced vibrational (VCD) circular dichroism spectroscopy. Using a combination of ECD and VCD with other methods such as IR, electron microscopy, and electrospray ionization mass spectrometry (ESI‐MS) it was found that G‐1 produces long‐range chiral aggregates consisting of G‐quartets, (G‐1)~4~, subsequently stacked into columns, [(G‐1)~4~]~n~, induced by binding of metal cations between the (G‐1)~4~ species. This process, accompanied by gelation of the sample, is highly efficient in the presence of an excess of sodium cations, leading to aggregates with strong quartet–quartet interaction. Thermally induced conformational changes and conformational stability of guanosine‐5′‐hydrazide assemblies were studied by chiroptical techniques and the melting temperature of the hydrogels formed was obtained. The temperature‐dependent experiments indicate that the long‐range supramolecular aggregates are dissociated by increasing temperature into less ordered species, monomers, or other intermediates in equilibrium, as indicated by MS experiments.