Using lanthanides as probes for polyelectrolyte–metal ion interactions. Hydration changes on binding of trivalent cations to nucleotides and nucleic acids

Abstract

a b s t r a c tThe interaction of the trivalent lanthanide ions Ce(III) and Tb(III) with ribonucleic acid (RNA) and guanosine 5 0 -triphosphate (GTP) in aqueous solution has been studied using their luminescence spectra and decays. Complexation is indicated by changes in luminescence intensity. With the system terbium(III)-RNA and terbium(III)-GTP, changes in luminescence with pH are probably related to conformational changes on the structure and also to the different degrees of protonation of phosphate groups and nucleotide bases. The degree of hydration of Tb(III) on binding to RNA and GTP is followed by luminescence lifetime measurements in water and deuterium oxide solutions, and at least one hydration water is lost from the lanthanide ion on binding to RNA or GTP at pH 4.7 and pH 7. Rather different behavior is observed on binding RNA at pH 9, where six water molecules are lost, possibly due to the lanthanide binding to the bases of the RNA backbone. This is similar to what has previously been seen with DNA, and is supported by 31 P NMR spectral measurements, which confirm the possibility of lanthanide binding to both phosphate and bases in the nucleic acids. In the case of GTP at pH 9, two water molecules appear to be lost, probably due to terbium binding both to guanine and a phosphate group. Gd(III) EPR spectral measurements with DNA, RNA and GTP suggest decreased lanthanide ion mobility on binding.

Understanding the Interaction between Trivalent Lanthanide Ions and Stereoregular Polymethacrylates through Luminescence, Binding Isotherms, NMR, and Interaction with Cetylpyridinium Chloride

“…The results show that 5−6 water molecules are lost on Tb(III) binding to PMA. This is similar to what is observed when this metal ion binds to poly(acrylate), 19,20 poly(vinyl sulfate), 27 single-strand DNA 8 or RNA 54 and is consistent with each bidentate carboxylate group replacing two water molecules on complexation. The experimental uncertainty in the number of bound water molecules (n H 2 O ) determined by this method has been discussed elsewhere 22 and is estimated to be approximately ±0.5.…”

Structure and dynamics of a DNA-based model system for the study of electron spin–spin interactions

“…It may be possible to differentiate between the formation of one or two metal ion-phosphate oxygen bonds by substituting Tb(III) for Dy(III). The coordination environment around EDTA(Tb(III)) is expected to be very similar to that of EDTA(Dy(III)) and the phosphorescence decay of Tb(III) is known to be sensitive to the number of bound water molecules [60][61][62].…”

Diffusion Behaviour of Trivalent Metal Ions in Aqueous Solutions

“…The accuracy of the systems (uncertainty 1-2 %) has been demonstrated by measurements on other solutions of different electrolytes (e.g. [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]).…”

“…Europium(III) is a trivalent lanthanide ion with attractive and versatile spectroscopic and magnetic properties [1,2], which are an advantage for applications in different fields such as biochemistry or materials. Eu(III) can be used as a luminescent probe of bioactive species including metal ions, oxyanions and acidity of biological environments [3][4][5]. Eu(III) can also be applied for the study of surfactant association in the solution [6].…”