Investigation of guanosine-quartet assemblies by vibrational and electronic circular dichroism spectroscopy, a novel approach for studying supramolecular entities.
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.
Setnicka
Vladimír
V
Institute of Chemical Technology, Technická 5, 166 28 Prague 6, Czech Republic. vladimir.setnicka@vscht.cz
Urbanová
Marie
M
Volka
Karel
K
Nampally
Sreenivasachary
S
Lehn
Jean-Marie
JM
D001665:Binding Sites; D035843:Biomedical Research / Q000379:methods*; D002942:Circular Dichroism; D004581:Electronics; D006151:Guanosine / Q000737:chemistry*; D020100:Hydrogels / Q000737:chemistry*; D008854:Microscopy, Electron; D008968:Molecular Conformation; D021241:Spectrometry, Mass, Electrospray Ionization; D013055:Spectrophotometry, Infrared; D013816:Thermodynamics
D020100:Hydrogels; D006151:Guanosine