Adsorption of Adenine, Cytosine, Thymine, and Uracil on Sulfide-Modified Montmorillonite: FT-IR, Mössbauer and EPR Spectroscopy and X-Ray Diffractometry Studies

Abstract

In the present work the interactions of nucleic acid bases with and adsorption on clays were studied at two pHs (2.00, 7.00) using different techniques. As shown by Mössbauer and EPR spectroscopies and X-ray diffractometry, the most important finding of this work is that nucleic acid bases penetrate into the interlayer of the clays and oxidize Fe(2+) to Fe(3+), thus, this interaction cannot be regarded as a simple physical adsorption. For the two pHs the order of the adsorption of nucleic acid bases on the clays was: adenine ≈ cytosine > thymine > uracil. The adsorption of adenine and cytosine on clays increased with decreasing of the pH. For unaltered montmorillonite this result could be explained by electrostatic forces between adenine/cytosine positively charged and clay negatively charged. However for montmorillonite modified with Na(2)S, probably van der Waals forces also play an important role since both adenine/cytosine and clay were positively charged. FT-IR spectra showed that the interaction between nucleic acid bases and clays was through NH(+) or NH (2) (+) groups. X-ray diffractograms showed that nucleic acid bases adsorbed on clays were distributed into the interlayer surface, edge sites and external surface functional groups (aluminol, silanol) EPR spectra showed that the intensity of the line g ≈ 2 increased probably because the oxidation of Fe(2+) to Fe(3+) by nucleic acid bases and intensity of the line g = 4.1 increased due to the interaction of Fe(3+) with nucleic acid bases. Mössbauer spectra showed a large decreased on the Fe(2+) doublet area of the clays due to the reaction of nucleic acid bases with Fe(2+).

Adsorption of nucleotides onto ferromagnesian phyllosilicates: Significance for the origin of life

“…For instance, nontronite NAu2 adsorbs as much as twice more dGMP than CMP at an equilibrium concentration of 0.5 mM. Purine nucleotides are more adsorbed than pyrimidine ones, as already observed in several studies Hashizume et al, 2010;Carneiro et al, 2011;Saha and Sarkar, 2014).…”

“…Phyllosilicates are assumed to be among the best candidates for the adsorption of nucleotides, a gram of clay can produce up to several hundreds of square meters of reactive surface in water. Hence, many studies have investigated phyllosilicates for adsorption (Banin et al, 1985;Ferris et al, 1989b;Franchi et al, 1999;Cai et al, 2006;Cai et al, 2008;Benetoli et al, 2008;Swadling et al, 2010;Hashizume et al, 2010;Carneiro et al, 2011;Michalkova et al, 2011;Swadling et al, 2013;Feuillie et al, 2013;Carneiro et al, 2013) or mineral-catalyzed polymerization (Ertem and Ferris, 1998;Ferris, 2002;Huang and Ferris, 2006;Joshi et al, 2009;Kaddour and Sahai, 2014). Most of those studies used montmorillonite and kaolinite as a reference for swelling and non-swelling clays, respectively.…”

Ionization constants and thermal stabilities of uracil and adenine under hydrothermal conditions as measured by in situ UV–visible spectroscopy

“…(See, for example: Sowerby et al, 2001Sowerby et al, , 2002Franchi et al, 2003;Saladino et al, 2004;Lambert, 2008;Carneiro et al, 2011). Sorption at the solution-surface interface takes place by one of two mechanisms.…”

“…These processes are also pH dependent. For example, at 25°C, adenine is more strongly adsorbed on montmorillonite at pH 2 than at pH 7, presumably because of the formation of AdH 2+ , while uracil adsorption is pH independent (Carneiro et al, 2011). The sorption of nucleic acid bases by clay minerals can also be enhanced by monovalent and divalent cations (Franchi et al, 2003).…”

Adsorption of amino acids and nucleic acid bases onto minerals: a few suggestions for prebiotic chemistry experiments

“…Clays exhibit several useful properties that promote adsorption of biomolecules, including high surface area and cationic exchange capacity, catalytic properties, intercalation of molecules in mineral interlayers and global distribution. Among the clays, most of the studies of adsorption of amino acids and nucleic acid bases were performed using Na-montmorillonite (Lailach & Brindley 1969;Hedges 1977;Rishpon et al 1982;Winter & Zubay 1995;Franchi et al 2003;Parbhakar et al 2007;Benetoli et al 2008;de Santana et al 2010;Negrón-Mendoza et al 2010;Pucci et al 2010;Carneiro et al 2011a;Sciascia et al 2011) and M-(Ca, Mg, Mn, Zn, Cu, Fe, Co, Ni)-montmorillonite (Lailach et al 1968;Lailach & Brindley 1969;StrašáK 1991;Hashizume et al 2010). Other clays such as bentonite (Benetoli et al 2008), kaolinite (Hedges 1977;Rishpon et al 1982;Benetoli et al 2008), vermiculite (Fraser et al 2011a,b) and saponite (Fu et al 1996;Weckhuysen et al 1999) have also been used for adsorption experiments of amino acids and nucleic acid bases.…”