Pressure‐sensitive adhesive utilizing molecular interactions between thymine and adenine

A simple pressure‐sensitive adhesion (PSA) system incorporating noncovalent interaction between thymine and adenine is presented. A copolymer having thymine moieties is combined with a low‐molecular‐weight bifunctional adenine cross‐linker. Molecular interactions caused by multiple hydrogen bonds between the thymine and adenine units are evaluated by FT‐IR spectral measurement. Mechanical properties of the PSA are examined by stress–strain curves and dynamic mechanical analysis. As the number of adenine cross‐linkers increases, Young's modulus increases from 0.24 to 3.0 MPa, and the glass transition temperature increases. Furthermore, it is found that the PSAs have adequate adhesive property from their shear strength test. Heat treatment at 80 °C is effective for reinforcement because of interchange of the hydrogen bonds. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1332‐1338     

Calculation and analysis of lifetimes of thymine and 5-chlorouracil tautomers in aqueous solutions at different pH values

The lifetime of zwitterionic, neutral, oxo, and hydroxy tautomeric forms of thymine and 5-chlorouracil is calculated with regard to intermolecular proton transfer in dimers. Time characteristics of picosecond spectra of aqueous solutions at different values are interpreted.     

Interaction of adenine adducts with thymine: a computational study

The existence of DNA adducts bring the danger of carcinogenesis because of mispairing with normal DNA bases. 1,N6-ethenoadenine adducts (epsilonA) and 1,N6-ethanoadenine adducts (EA) have been considered as DNA adducts to study the interaction with thymine, as DNA base. Several different stable conformers for each type of adenine adduct with thymine, [epsilonA(1)-T(I), epsilonA(2)-T(I), epsilonA(3)-T(I) and EA(1)-T(I), EA(2)-T(I), EA(3)-T(I)] and [epsilonA(1)-T(II), epsilonA(2)-T(II), epsilonA(3)-T(II) and EA(1)-T(II), EA(2)-T(II), EA(3)-T(II)], have been considered with regard to their interactions. The differences in their geometrical structures, energetic properties, and hydrogen-bonding strengths have also been compared with Watson-Crick adenine-thymine base pair (A-T). Single-point energy calculations at MP2/6-311++G** levels on B3LYP/6-31+G* optimized geometries have also been carried out to better estimate the hydrogen-bonding strengths. The basis set superposition error corrected hydrogen-bonding strength sequence at MP2/6-311++G**//B3LYP/6-31+G* for the most stable complexes is found to be EA(2)-T(I) (15.30 kcal/mol) > EA(1)-T(II) (14.98 kcal/mol) > EA(3)-T(II) (14.68 kcal/mol) > epsilonA(2)-T(I) (14.54 kcal/mol) > epsilonA(3)-T(II) (14.22 kcal/mol) > epsilonA(3)-T(II) (13.64 kcal/mol) > A-T (13.62 kcal/mol). The calculated reaction enthalpy value for epsilonA(2)-T(I) is 10.05 kcal/mol, which is the highest among the etheno adduct-thymine complexes and about 1.55 kcal/mol more than those obtained for Watson-Crick A-T base pair and the reaction enthalpy value for EA(1)- T(II) is 10.22 kcal/mol, which is highest among the ethano addcut-thymine complexes and about 1.72 kcal/mol more than those obtained for Watson-Crick A-T base pair. The aim of this research is to provide fundamental understanding of adenine adduct and thymine interaction at the molecular level and to aid in future experimental studies toward finding the possible cause of DNA damage.     

Spectroscopic assessment of argon gas discharge induced radiolysis of aqueous adenine and thymine

Ionizing radiation influences life profoundly for it can modify genetic materials. It is a long-standing task to investigate the interaction between energetic particles and DNA together with its components such as nucleotides, nucleosides and bases so as to predict and assess the potential biological effects. In this study, argon gas discharge was employed to produce energetic ions and electrons. The gas discharge caused the radiolysis of aqueous bases and the involved reactions were analyzed by means of spectroscopic tools including UV–vis absorption, fluorescence and Fourier transformation infrared (FTIR) spectroscopy, also assisted by liquid chromatography/mass spectrometry (LC/MS). It was found that the discharge resulted in the adenine-derived lesions such as 4,6-diamino-5-formamidopyrimidine, 8-OH-Ade and 2-OH-Ade in the radiolysis of aqueous adenine, as well as the thymine-derived lesions such as thymine glycol, 5-hydroxy-6-hydrothymine and/or 6-hydroxy-5-hydrothymine, 5-hydroxymethyluracil and 5-formyluracil in the radiolysis of aqueous thymine. The study of radio-sensitivity showed that adenine was more resistant to the discharge. The mechanisms of the involved reactions were studied in detail, confirming that the hydroxyl radical played a dominant role.     

Interaction of superhydrophobic materials with aqueous solutions and organic solvents

The interaction of a fluorine-containing superhydrophobic (SHP) coating on the surface of a siloxane rubber with aqueous solutions and organic solvents was studied by wettability analysis. The long-term durability of the coating against the damaging action of atmosperic precipitates saturated with salt ions, acid rains, as well as a number of organic solvents was demonstrated. The resistance of the coating to highly alkaline media is lower than to a neutral medium because of the hydrolysis of Si—O—Si bonds and amide groups. The low resistance of the fluorine-containing SHP coating to acetone is due to the swelling of the substrate and mechanical destruction of the fluoroorganic component.     

Regioselective synthesis of 1-allyl- and 1-arylmethyl uracil and thymine derivatives

2,4-Bis(trimethylsiloxy) pyrimidines 1 with allyl halides and arylmethyl halides in 1,2-dichloroethane in the presence of I₂ regioselectively provide 1-allyl-/1-arylmethyl-uracil and thymine derivatives. The secondary aryl alkyl and diaryl methyl halides with 1 provide chiral 1-arylalkyl/1-(diarylmethyl) uracil/thymine derivatives. The procedure has been extended to the synthesis of fluorescent uracil/thymine derivatives.     

Interaction of amino acids, N-acetyl amino acid esters, thymine and adenine with sephadex LH-20 gel.

N-Acetyl aromatic amino acid esters, tryptophan, adenine and thymine show strong retention in Sephadex LH-20 gel in an aqueous phase. The decreased retention in 6 M urea, the absence of retention in absolute methanol and the increased retention at higher temperatures in the aqueous phase indicate that hydrophobic interaction is responsible for the observed retention of the amino acids and their esters in the gel. Adenine was found to be retained by polar interaction in the gel. The increased retention of the solutes in the presence of different electrolytes suggests that the lyotropic effect is more important than the ionic strength effect. The relevance of the results obtained with amino acids and esters to the conformational aspects of proteins in aqueous solution is discussed.     

Interaction of ampicillin with zinc and cadmium ions in aqueous solutions

In weakly acidic and neutral media, Zn²⁺ and Cd²⁺ ions form 1: 1 chelates with ampicillin in the anionic form; the ligand is coordinated through amino and anionic carboxylate groups.     

Four cocrystals of thymine with phenolic coformers: influence of the coformer on hydrogen bonding

Cocrystals are molecular solids composed of at least two types of neutral chemical species held together by noncovalent forces. Crystallization of thymine [systematic name: 5‐methylpyrimidine‐2,4(1H,3H)‐dione] with four phenolic coformers resulted in cocrystal formation, viz. catechol (benzene‐1,2‐diol) giving thymine–catechol (1/1), C₅H₆N₂O₂·C₆H₆O₂, (I), resorcinol (benzene‐1,3‐diol) giving thymine–resorcinol (2/1), 2C₅H₆N₂O₂·C₆H₆O₂, (II), hydroquinone (benzene‐1,4‐diol) giving thymine–hydroquinone (2/1), 2C₅H₆N₂O₂·C₆H₆O₂, (III), and pyrogallol (benzene‐1,2,3‐triol) giving thymine–pyrogallol (1/2), C₅H₆N₂O₂·2C₆H₆O₃, (IV). The resorcinol molecule in (II) occupies a twofold axis, while the hydroquinone molecule in (III) is situated on a centre of inversion. Thymine–thymine base pairing is common across all four structures, albeit with different patterns. In (I)–(III), the base pair is propagated into an infinite one‐dimensional ribbon, whereas it exists as a discrete dimeric unit in (IV). In (I)–(III), the two donor N atoms and one carbonyl acceptor O atom of thymine are involved in thymine–thymine base pairing and the remaining carbonyl O atom is hydrogen bonded to the coformer. In contrast, in (IV), just one donor N atom and one acceptor O atom are involved in base pairing, and the remaining donor N atom and acceptor O atom of thymine form hydrogen bonds to the coformer molecules. Thus, the utilization of the donor and acceptor atoms of thymine in the hydrogen bonding is influenced by the coformers.     

Interaction of cyanocobalamin with sulfur-containing reducing agents in aqueous solutions

The kinetics and mechanism of cyanocobalamin reduction by sodium hydroxymethanesulfinate and dithionite in alkaline media are studied. It is established that the character of the rate-determining step depends on the concentration of the reducing agents: when they are in excess, it is a step of elimination of cyanocobalamin, at lower concentrations of reducing agents a rate-determining is a step of their addition to cobalamin.     

Interaction of benzene with water and aqueous solutions of alkali metal chlorides

The balance of potential energies of compression and expansion of a water cavity containing a benzene molecule is calculated in the quasi-spherical approximation. It is established that the cavity expands under the action of reactive electrostatic repulsion forces and is compressed under the action of forces of macroscopic surface tension and dispersion interaction. It is shown that in the presence of ions disrupting the water structure, the cavity increases in size.     

Identification of radiation-induced cross-linking between thymine and tryptophan by electrospray ionization-mass spectrometry

Upon exposure to ionizing radiation, DNA undergoes a variety of modifications including the production of a covalent bond between the nucleobase thymine and aromatic amino acids. In this work, electrospray ionization-mass spectrometry(ESI-MS) was used to identify the gamma radiation-induced covalent cross-linking of model peptides (sequence YPPW and pYPPW) with the nucleobase thymine. Tandem electrospray ionization-mass spectrometry (ESI-MSn) was employed to investigate the cross-linking sites. The results showed that irrespective of whether tyrosine was phosphorylated or not, the nucleobase thymine was cross-linked with the tryptophan residue. Possible cross-linking mechanisms are proposed by investigating the related mass peaks.     

Reactivities of hydroxyl and perhydroxyl radicals toward cytosine and thymine: A comparative study

As the hydroxyl (OH) and perhydroxyl (OOH) radicals are known to play important roles in biological systems, their reactions with cytosine and thymine were studied. Addition reactions of these radicals at different sites of cytosine and thymine, and hydrogen abstraction reactions by each of the two radicals from the different sites of the two molecules were studied at the B3LYP/6‐31G(d,p), B3LYP/AUG‐cc‐pVDZ and BHandHLYP/AUG‐cc‐pVDZ levels of density functional theory. Effect of solvation in aqueous media on the reactions was studied at all these levels of theory using single point energy calculations using the polarizable continuum model. The present study shows that whereas the OH radical would abstract H atoms from the various sites of cytosine and thymine efficiently, the OOH radical would have poor reactivity in this regard. The OH radical is also predicted to be much more reactive than the OOH radical with regard to addition reactions at the C5 and C6 sites of both thymine and cytosine, though the OOH radical is also predicted to have significant reactivity in this respect. © 2012 Wiley Periodicals, Inc.     

嘧啶及其异构体的密度泛函理论研究

胞嘧啶、尿嘧啶和胸腺嘧啶都有酮式和烯醇式互变异构。有人认为DNA的错配频率,与酮,烯醇或氨,亚氨的互变异构平衡有关。迄今,在相同理论水平上同时对三种嘧啶互变异构体进行理论计算研究的文献较少,     

Reactions of ·OH with thymine studied using density functional theory

We studied three possible reactions of a free ·OH radical with thymine by using density functional theory calculations. The results indicate that there is no energy barrier in the reactions of a free ·OH radical adding to the C₆ position of thymine, while the reactions of a free ·OH radical adding to the C₅ position of thymine and the reaction of an ·OH abstracting a hydrogen from the C₅ methyl group should overcome the energy barriers of ～0.70 kcal/mol and ～1.88 kcal/mol, respectively. The C₆‐hydroxylated radical formed is energetically more favorable than the C₅‐hydroxylated radical. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005