Thymine adsorption

Adsorption of adenine and coadsorption of adenine-thymine and uracil-thymine on Au(lll) has been reported [300]. Adenine was chemisorbed in two different states. Mutual interaction between adenine and thymine was detectable only at... 

The electrochemical behaviour and the adsorption of nucleic acid molecules and DNA constituents have been extensively studied over recent decades [1-6]. Electrochemical studies demonstrated that all DNA bases can be electrochemically oxidized on carbon electrodes [7-13], following a pH-dependent mechanism. The purines, guanine (G) and adenine (A), are oxidized at much lower positive potentials than the pyrimidines, cytosine (C) and thymine (T), the oxidation of which occurs only at very high positive potentials near the potential corresponding to oxygen evolution, and consequently are more difficult to detect. Also, for the same concentrations, the oxidation currents observed for pyrimidine bases are much smaller than those observed for the purine bases. Consequently, the electrochemical detection of oxidative changes occurring in DNA has been based on the detection of purine base oxidation peaks or of the major... 

Roelfs, B., Bunge, E., Schroter, C., Solomun, T., Meyer, H., Nichols, R.J., and Baumgartel, H. (1997) Adsorption of thymine on gold single-crystal electrodes. Journal of Physical Chemistry... 

Figure 6.16 (a) Molecular structure of thymine, (b) Adsorption model of thymine on an Ag... 

In situ STM has provided detailed structural models for the adsorption of cytosine, uracil and thymine at a number of electrode surfaces.These studies have included thymine adsorbed on Au(lll), Au(lOO) and Au(210), uracil adsorption on Au(lll), Au(lOO) and Ag(lll). These pyrimidine bases show a particularly interesting phase behaviour, which can be seen from cyclic voltammograms (CV). A CV for the... 

Figure 7-8. A proposed adsorption model for chemisorbed uracil and thymine. ...

Figure 19 shows the A/l/i o — curves of cytosine, thymine, and their derivatives. In the case of cytosine, A // o begins to increase at about —0.5 V. The curve shows a quasi-bell shape having a maximum at the pzc at lower concentrations but aquires a somewhat more complex shape at higher concentration, with some increase in A // ol at potentials more positive than 0.1 V (curve b in Fig. 19A). This seems to indicate that the adsorption process is accompanied by reorientation or formation of the cytosine dimer on the positively charged surface. Since such complicated shapes are observed only in the curves of cytosine and guanine, having the same substituent groups, the interaction of —NH2 and =0 may be partly responsible for their complicated behavior on the electrode surface.

Deoxythymidine and dTMP give a lA/ // ol relation similar to thymine (Fig. 19 and F). It is likely that the participation of the deoxyribose and phosphate parts in the adsorption of deoxythymidine and dTMP is not significant, in contrast with that of deoxycytidine and dCMP. 

Adsorption Parameters of Adenine, Thymine, and Their Derivatives in the Negative Potential Region on Au... 

Based on these results, possible models to show the orientation of both the adenine and the thymine series in their adsorption on the negatively charged electrode surface are given in Fig. 20. 

The SPR is found around ( o = 46°. From data taken at various electrode potentials, the number of organic species in the condensed thymine film could be calculated [957]. With a combination of SPR and EQCMB, the adsorption of a perfluo-... 

The DNA bases, guanine, thymine, cytosine, and adenine, were studied by STM on several substrates. Some authors report hydrogen bonding or stacking of the molecules on Au(lll). The Cu surfaces are often used as substrates for adsorption of the DNA bases. Hydrogen-bond patterns were analyzed on this surface. 

Two works were devoted to the ab initio cluster calculations of the interactions between minerals of the kaolinite group with thymine (TH) and uracil (U). The key purpose of such studies was to determine (i) the equilibrium adsorption of selected nucleic acids, differing in chemical, molecular structure and functions (DNA, RNA) on specific clay mineral surfaces and (ii) the nature of the interaction between nucleic acids and clay using computational chemistry methods and modeling. An additional objective was to assess the effect of presence of water and sodium cation commonly occurring in soils on the process of adsorption. 

Table 21.4 presents the atomic charges of adsorbed and isolated thymine obtained by the fitting of the electrostatic potential. For uracil and thymine the adsorption... 

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