Thymine Groups Research Articles

Simultaneously enhancing the mechanical and thermoelectric properties of diketopyrrolopyrrole-thiophene based conjugated polymers through dynamic hydrogen-bonding

Remarkable progress has been made in the development of thermoelectric materials based on diketonepyrrolopyrrole-thiophene (DPPT). However, achieving DPPT polymers with both high thermoelectric and mechanical properties remain a challenge. In this study, thymine groups, which are beneficial for the formation of intermolecular hydrogen bonds, were introduced into the side chains of DPPT, and a series of polymers (PDPPT-x) with different amount of thymine groups (x is the molar ratio of thymine side chains) were synthesized and characterized. The introducing thymine groups can regulate the self-assembly of conjugated polymers, effectively enhancing the crystallinity and molecular packing order, and thereby improve the charge carrier mobility. Additionally, the formed dynamic hydrogen-bonding networks by the thymine groups possess a moderate strength that can alleviate applied pressure and enhance the flexibility. Among these polymers, PDPPT-5 exhibited superior performance with excellent flexibility demonstrated by its elongation at break (up to 19.8 %), surpassing that of PDPPT-0 by a power factor of 2.2. In addition, the incorporation of 5 % amount of thymine groups can enhance the interchain interactions, thereby improving the crystallinity of the polymers and consequently enhancing the carrier mobility (4.26 × 10-3 cm2 V−1 s−1 for PDPPT-5 compared to 1.14 × 10-3 cm2 V−1 s−1 for PDPPT-0). Upon doping with FeCl3 at room temperature, the power factor of PDPPT-5 is about twice that of PDPPT-0. These results suggest that incorporating hydrogen bonding is a highly effective strategy for enhancing both the thermoelectric and mechanical properties of conjugated polymer-based thermoelectric materials.

Side-chain engineering by thymine groups enables hydrogen bond in P-type donor-acceptor polymers with enhanced optoelectronic properties

Realizing ordered structures at the molecular level is a key approach to increase the charge mobility of organic semiconductors. However, the typical solution-based methods employed for the processing make the achievement of well-organized organic nanostructures difficult with the favored formation of disordered assemblies. To realize well-ordered thin films, one needs to design conjugated materials with the ability of self-assembling. In this work, two alternating donor-acceptor copolymers based on the carbazole and diketopyrrolopyrrole (DPP) units, namely P1 and P2, are successfully synthesized. Compared to P1, the polymer P2 contains an extra thymine group at the end of the alkyl chain, through which the hydrogen bonding (CO⋯NH) can be formed between the amide (NH) and carbonyl units (CO), as verified by the fourier transform infrared (FTIR) and differential scanning calorimetry (DSC) study. The electrochemical analysis shows that the hydrogen bonding association influences the carbazole donor ability, resulting in a higher HOMO energy level of P2 compared to P1. In addition, the as-formed hydrogen bonds promote the assembling of the molecules into highly ordered structures by enabling strong aggregation as well as a narrow distance between adjacent molecules with long-range ordering packing and large nanocrystalline grains. As a result, the intermolecular charge transfer is enhanced. Consequently, the organic field-effect transistors (OFETs) constructed with P2 as the semiconductor layer present a p-type behavior with maximum hole mobility up to 1.32 cm2 V−1 s−1 upon annealing, which is almost 5 times higher than that of the pristine P2 (0.26 cm2 V−1 s−1), while the hole mobility of the annealed P1 is only 0.23 cm2 V−1 s−1. Our results indicate that the alkyl chain engineering, with the introduction of a thymine group into the donor units of the polymer, is responsible for the formation of hydrogen-bonded superstructures. This is a facile approach to enhance the optoelectronic properties of organic semiconductors.

Enhanced Triplex Hybridization of DNA and RNA via Syndiotactic Side Chain Presentation in Minimal bPNAs.

General design principles for recognition at noncanonical interfaces of DNA and RNA remain elusive. Triplex hybridization of bifacial peptide nucleic acids (bPNAs) with oligo-T/U DNAs and RNAs is a robust recognition platform that can be used to define structure-function relationships in synthetic triplex formation. To this end, a set of minimal (mw < 1 kD) bPNA variants was synthesized to probe the impact of amino acid secondary structural propensity, stereochemistry, and backbone cyclization on hybridization with short, unstructured T-rich DNA and U-rich RNAs. Thermodynamic parameters extracted from optical melting analyses of bPNA variant hybrids indicated that there are two bPNA backbone modifications that significantly improve hybridization: alternating (d, l) configuration in open-chain dipeptides and homochiral dipeptide cyclization to diketopiperazine. Further, binding to DNA is preferred over RNA for all bPNA variants. Thymine-uracil substitutions in DNA substrates revealed that the methyl group of thymine accounts for 71% of ΔΔGDNA-RNA for open-chain bPNAs but only 40% of ΔΔGDNA-RNA for diketopiperazine bPNA, suggesting a greater sensitivity to RNA conformation and more optimized stacking in the cyclic bPNA. Together, these data reveal pressure points for tuning triplex hybridization at the chiral centers of bPNA, backbone conformation, stacking effects at the base triple, and the nucleic acid substrate itself. A structural blueprint for enhancing bPNA targeting of both DNA and RNA substrates includes syndiotactic base presentation (as found in homochiral diketopiperazines and d, l peptides), expansion of base stacking, and further investigation of bPNA backbone preorganization.

Biomimetic Polymer-Templated Copper Nanoparticles Stabilize a Temozolomide Intermediate for Chemotherapy against Glioblastoma Multiforme.

The short half-life of temozolomide (TMZ) limits its therapeutic effect on highly aggressive glioblastoma (GBM). Few approaches attempting to intervene the metabolic kinetics of TMZ are successful. Herein, we designed anionic copolymers via radical polymerization to prepare polymer-coated small copper nanoclusters, taking advantage of the role of pendent thymine groups as a template. The active and key intermediate of TMZ, typically called 3-methyl-(triazen-1-yl)imidazole-4-carboxamide (MTIC), was stabilized by copper under physiological (slightly alkaline) conditions, alleviating concerns associated with spontaneous drug degradation and nonspecific drug activation. Importantly, the complexes formed by MTIC and copper nanoclusters could catalyze the Fenton reaction to generate hydroxyl radicals and also respond to pH and glutathione to release therapeutic MTIC, which allows combined chemotherapy and chemodynamic therapy against GBM cells and paves a way for circumventing the complication of TMZ resistance.

Development of a Healable Bulk Heterojunction Using Conjugated Donor Polymers Based on Thymine-Functionalized Side Chains

Developing intrinsically self-healable semiconducting polymers is particularly important for realizing stretchable electronic devices which can spontaneously recover their mechanical damage. We synthesized a series of conjugated donor polymers (PTO2-tm series) functionalized with a thymine group at the terminal of the side chain. Bulk heterojunction (BHJ) films of PTO2-tm polymers blended with an IT-4F acceptor achieved power conversion efficiencies up to 11.9% from the BHJ-based organic photovoltaics, which are comparable with that of unfunctionalized PTO2 and, however, exhibited much improved stretchability by virtue of stress dissipation in the BHJ films during mechanical deformation. More importantly, the corresponding BHJ film prepared with a melamine additive efficiently recovered their packing structures after being mechanically damaged by stretching. As a result, reversible multiple hydrogen bonding of the melamine molecule with thymine in PTO2-tm polymers showed much improved crack onset strain and maximum recoverable strain compared with PTO2.

Peptide nucleic acid Hoogsteen strand linker design for major groove recognition of DNA thymine bases

Sequence-specific targeting of double-stranded DNA and non-coding RNA via triple-helix-forming peptide nucleic acids (PNAs) has attracted considerable attention in therapeutic, diagnostic and nanotechnological fields. An E-base (3-oxo-2,3-dihydropyridazine), attached to the polyamide backbone of a PNA Hoogsteen strand by a side-chain linker molecule, is typically used in the hydrogen bond recognition of the 4-oxo group of thymine and uracil nucleic acid bases in the major groove. We report on the application of quantum chemical computational methods, in conjunction with spatial constraints derived from the experimental structure of a homopyrimidine PNA·DNA-PNA hetero-triplex, to investigate the influence of linker flexibility on binding interactions of the E-base with thymine and uracil bases in geometry-optimised model systems. Hydrogen bond formation between the N2 E-base atom and target pyrimidine base 4-oxo groups in model systems containing a β-alanine linker (J Am Chem Soc 119:11116, 1997) was found to incur significant internal strain energy and the potential disruption of intra-stand aromatic base stacking interactions in an oligomeric context. In geometry-optimised model systems containing a 3-trans olefin linker (Bioorg Med Chem Lett 14:1551, 2004) the E-base swung out away from the target pyrimidine bases into the solvent. These findings are in qualitative agreement with calorimetric measurements in hybridisation experiments at T-A and U-A inversion sites. In contrast, calculations on a novel 2-cis olefin linker design indicate that it could permit simultaneous E-base hydrogen bonding with the thymine 4-oxo group, circumvention and solvent screening of the thymine 5-methyl group, and maintenance of triplex intra-stand base stacking interactions.

Supernucleation, crystalline structure and thermal stability of bacterially synthesized poly(3-hydroxybutyrate) polyester tailored by thymine as a biocompatible nucleating agent

Naturally occurring thymine (TM) was incorporated into bacterial poly(3-hydroxybutyrate) (PHB) polyester to fabricate a novel and green biocomposite. Both 0.5% and 1% TM exhibit supernucleation effect on PHB, and crystallization kinetics suggests TM significantly increased Tc and Xc, and substantially shortened t1/2 of PHB. Epitaxial nucleation caused by a perfect crystal lattice matching between PHB and TM, was proposed to elucidate nucleation mechanism of PHB. Hydrogen bond interaction exists between CO, C–O–C groups of PHB and –CH3 (or –CH)/–NH– group of TM. TM interacted with CO group of PHB crystalline phase rather than that of amorphous one. In addition, two new IR crystalline bands assigned to C–O–C group of PHB appeared in the presence of TM, which arises from shift of two amorphous ones, respectively. TM enhanced onset thermal degradation temperature of PHB, mainly attributed to increased degree of crystallinity of PHB and flame retardance effect of TM.

A new light-responsive resistive random-access memory device containing hydrogen-bonded complexes

In the search to obtain new and more efficient components of memory devices, we report the photochromic, dielectric and electrochemical response of a light-responsive organic compound, and its memory performance under electrical fields. The so-called N(1)-[12-(4-(4′-isobutyloxyphenyldiazo)phenoxy)dodecyloxy)]thymine, tAZOi, molecule contains one azobenzene group, which provides with photochromic character, and one terminal thymine group, capable to form hydrogen bonds and assemble supramolecular dimers, (tAZOi)2. We have calculated the optical absorption coefficient, extinction coefficient and refractive index of tAZOi, which obeys the single oscillator Wemple–DiDomenico model. An ITO/tAZOi/Al device has been prepared and presents two switchable conductance states with preservation of memory performance. The mechanism linked to the resistive random-access memory (RRAM) has been evaluated by molecular modelling and is controlled by p-type conduction, possibly involving hydrogen-bonding. Upon UV irradiation at ∼ 365 nm, tAZOi displays an increase in the complex permittivity driven by trans-to-cis (E-to-Z) isomerisation of the azobenzene groups. Molecular simulations suggest that conductivity and device performance can be enhanced (and controlled) by light exposure through the formation of activated Z isomers that could transfer charge to other neighbouring molecules, resulting in photo-electric responsive devices.

Efficient Co-delivery of Doxorubicin and Methotrexate by pH-Sensitive Dual-Functional Nanomicelles for Enhanced Synergistic Antitumor Efficacy.

Combination therapy by co-delivering multiple drugs using a single delivery carrier is a promising strategy to achieve a synergistic antitumor effect. In this study, a novel dual-functional block copolymer mPEG-b-poly(TAC-co-ATMC-g-S(CH2)10COOH) was designed and synthesized for co-delivering two kinds of anticancer drugs, methotrexate (MTX) and doxorubicin (DOX). This biodegradable amphiphilic copolymer could spontaneously self-assemble into electronegative nanomicelles with higher micelle stability and lower hemolysis ratio. Besides hydrophobic interactions, electrostatic interactions between the carboxyl groups of 5-allyloxy-1,3-dioxan-2-one (ATMC) with amine groups of DOX, as well as complementary multiple hydrogen-bonding interactions between thymine groups of thymine-functional six-membered cyclic carbonate (TAC) and 2,6-diaminopyridine (DAP) groups of MTX, could contribute to co-delivering DOX/MTX simultaneously with high-efficiency loading without interference with each other. For comparison, DOX alone and MTX alone were also encapsulated into mPEG-b-poly(TAC-co-ATMC-g-S(CH2)10COOH) nanomicelles. All drug-loaded nanomicelles exhibited sustained release properties with a pH sensitivity. Confocal laser scanning microscopy revealed an efficient cell uptake of DOX and MTX delivered by mPEG-b-poly(TAC-co-ATMC-g-S(CH2)10COOH) nanomicelles, while DOX mainly accumulated in nuclei and MTX in cytoplasm after 8 h of incubation. MTT assay further demonstrated an enhanced synergistic antitumor efficacy of DOX/MTX co-loaded nanomicelles. Therefore, DOX/MTX co-loaded mPEG-b-poly(TAC-co-ATMC-g-S(CH2)10COOH) nanomicelles might have attractive potentials in clinical implications for efficient combination chemotherapy.

Conjugated Semiconducting Polymer with Thymine Groups in the Side Chains: Charge Mobility Enhancement and Application for Selective Field-Effect Transistor Sensors toward CO and H2S

Conjugated polymers with both high charge mobilities and responsive functionality have received increasing attention because of their promising applications in organic electronic devices and chemo-/biosensors. We successfully incorporated thymine groups in the side chains of diketopyrrolopyrrole (DPP)-based conjugated polymer PDPP4T-T. Our studies reveal that thin films of PDPP4T-T exhibit improved crystallinity and higher charge mobility compared with analogous polymers with pure alkyl chains. This is attributed to the formation of H-bonding among thymine groups, which could strengthen interchain interactions and thus facilitate an ordered packing of polymer chains. Importantly, thin films of PDPP4T-T containing either Pd(II) or Hg(II) ions were successfully fabricated via air–water interface coordination reactions of thymine groups with ions. Thin-film field-effect transistors (FETs) of PDPP4T-T containing Pd(II) ions exhibit a sensitive and selective response toward CO even at a low concentration of 10...

Controlling the Two-Dimensional Self-Assembly of Functionalized Porphyrins via Adenine–Thymine Quartet Formation

The development of supramolecular synthons capable of driving hierarchical two-dimensional (2D) self-assembly is an important step toward the growth of complex and functional molecular surfaces. In this work, the formation of nucleobase quartets consisting of adenine and thymine groups was used to control the 2D self-assembly of porphyrins. Tetra-(phenylthymine) zinc porphyrin (Zn-tetra-TP) and tetra-(phenyladenine) porphyrin (tetra-AP) were synthesized, and scanning tunneling microscopy (STM) experiments were performed to visualize their self-assembly at the liquid–solid interface between an organic solvent and a graphite surface. Monocomponent solutions of both Zn-tetra-TP and tetra-AP form stable 2D structures with either thymine–thymine or adenine–adenine hydrogen bonding. Structural models based on STM data were validated using molecular mechanics (MM) simulations. In contrast, bicomponent mixtures showed the formation of a structure with p4 symmetry consisting of alternating Zn-tetra-TP and tetra-AP...

Removal of some commercial pesticides from aqueous dispersions using as flocculant a thymine-containing chitosan derivative

A novel thymine-containing chitosan derivative has been designed, synthesized, and used for the first time in this work for removal of some commercial pesticides from synthetic wastewater by coagulation/flocculation. The chitosan-thymine conjugate was characterized by 1H NMR and FT-IR spectroscopy, and its flocculation performance was evaluated by UV–Vis spectroscopy in comparison to non-modified chitosan. The commercial pesticides used in this investigation were Fastac 10 EC and Karate Zeon (with alpha-Cypermethrin and lambda- Cyhalothrin, respectively, as active pyrethroid ingredients), Novadim Progress (Dimethoate as active organophosphoric ingredient), and Bordeaux mixture. The experimental results demonstrate good removal efficiency for Karate Zeon (between 80 and 85%), a maximum of around 90% for Fastac 10EC and Novadim Progress, and more than 95% for the Bordeaux mixture, irrespective of the polycation structure. According to the zeta potential values recorded in the optimum dose interval, the flocculation of pyrethroid pesticides particles took place mainly by means of the charge neutralization mechanism (close to zero), whereas the flocculation of Novadim Progress and Bordeaux mixture particles has been achieved by the synergistic effect of charge neutralization and hydrogen bonding (Novadim Progress) or copper ion binding by the amine and thymine groups (Bordeaux Mixture) (negative values).

Self-healing epoxy nanocomposites via reversible hydrogen bonding

The development of high performance self-healing composites is still at an early stage due to the difficulty to integrate self-healing mechanisms in their structure by applying current manufacturing processes. Here, the authors propose structural self-healing resins based on dynamic hydrogen bonds capable to overcome many current industrial limitations. Hydrogen bonding moieties, such as barbiturate and thymine, able to act as reversible healing-elements by their simultaneous donor and acceptor character, can be covalently linked to multi-wall carbon nanotubes (MWCNTs) to generate self-healing nanocomposites. The so functionalized MWCNTs, embedded in a rubber-toughened epoxy formulation, lead to reversible MWCNTs-bridges through the matrix due to strong attractive interactions between the rubber phase, finely dispersed in the matrix, and MWCNT walls. Healing efficiencies have been assessed for the nanocharged epoxy formulation loaded with 0.5% wt/wt of MWCNTs decorated with barbituric acid and thymine groups. For both functional groups, healing efficiencies higher than 50% have been found. Dynamic mechanical analysis (DMA) evidences an enhancement in epoxy chains movements due to micro/nano domains of the rubber phase enabling self-healing behavior by recovering the critical fracture load. Results from this study may promote the wide development of safe and cost-efficient self-healing composites in aeronautical, automotive, civil engineering and wind power industries.

Synthesis, X-ray structure and cytotoxicity evaluation of carbene-based gold(I) complexes of selenones

Abstract Gold(I)-carbene complexes containing a selenone ligand (L), [Au(IPr)(L)]PF6 {where, IPr = 1,3-Bis(2,6-di-isopropylphenyl)imidazol-2-ylidene and L = N-i-propyl-1,3-imidazolidine-2-selenone, i-PrImSe (1), 1,3-diazinane-2-selenone, DiazSe (2), N-methyl-1,3-diazinane-2-selenone, MeDiazSe (3), 5-hydroxy-1,3-diazinane-2-selenone, HO-DiazSe (4) and 1,3-diazepane-2-selenone, DiapSe (5)} were synthesized using [Au(IPr)Cl] (0) and selenones. The complexes (1–5) were characterized by elemental analysis, IR and NMR (1H, 13C & 77Se) spectroscopy. The crystal structure of complex 1 was determined by single crystal X-ray diffraction technique and the analysis reveals that the complex exhibits a distorted linear geometry around gold(I) atom. In vitro cytotoxic assays of the complexes were performed on three human cancer cell lines; HCT15 (colon cancer), A549 (lung cancer) and MCF7 (breast adenocarcinoma). Complexes 1 and 3 exhibited greater activities against HCT15 cells compared to the other complexes (2, 4 and 5). All complexes exhibited moderate to high IC50 values (less active) against A549 and MCF7 cell lines with respect to cisplatin. Molecular docking studies showed the potential inhibitory capacity of the gold complexes towards DNA topoisomerase 1 with complex 1 having the highest binding affinity with a score of −38.68. The distance between the gold atom in the complex and the oxygen atom of the carbonyl group of thymine was measured for all complexes. Complex 4 had the shortest bond distance of 3.64 A, while complex 5 had the longest one of 6.89 A.

Stern-Layer Adsorption of Oligonucleotides on Lamellar Cationic Lipid Bilayer Investigated by Polarization-Resolved SFG-VS.

The molecular interaction between the oligonucleotides and lipid membranes is the key to the functions of virus, aptamer, and various oligonucleotide-based materials. In this study, the conformational changes of oligonucleotides (dT25) on lamellar cationic 1,2-dimyristoyl-3-trimethylammonium-propane (DMTAP) bilayer were investigated by polarization-resolved sum frequency generation vibrational spectroscopy (SFG-VS) in situ. The SFG-VS spectra within different wavenumber ranges were analyzed to give conformation details of thymine groups, phosphate groups, and OD/OH groups and to provide a comprehensive and fundamental understanding of the oligonucleotide adsorption on a model bilayer. It is shown that the adsorption of dT25 on DMTAP bilayer reaches maximum at CdT ≈ 500 nM. And the conformation of dT25 molecules change significantly when surface charge of DMTAP bilayer reaches the point of zero charge (PZC) at CdT ≈ 100 nM. Combined spectroscopic evidences also indicate that the formation of electric double layer at the DMTAP/dT25 surface follows the Gouy–Chapman–Stern model. The analysis results also show that the symmetric PO2– stretching mode of oligonucleotide molecules can serve as a sensitive vibration molecular probe for quantifying the oligonucleotide/lipid charge ratio and determine the point of zero charge (PZC) of lipid bilayer surface, which may help researchers to control the layer-by-layer assembly of oligonucleotide–lipid complexes and to improve the efficiency genetic therapy against cancer and viral infections.

Differences in fecal microbial metabolites and microbiota of children with autism spectrum disorders

Evidence supporting that gut problems are linked to ASD symptoms has been accumulating both in humans and animal models of ASD. Gut microbes and their metabolites may be linked not only to GI problems but also to ASD behavior symptoms. Despite this high interest, most previous studies have looked mainly at microbial structure, and studies on fecal metabolites are rare in the context of ASD. Thus, we aimed to detect fecal metabolites that may be present at significantly different concentrations between 21 children with ASD and 23 neurotypical children and to investigate its possible link to human gut microbiome. Using 1H-NMR spectroscopy and 16S rRNA gene amplicon sequencing, we examined metabolite profiles and microbial compositions in fecal samples, respectively. Of the 59 metabolites detected, isopropanol concentrations were significantly higher in feces of children with ASD after multiple testing corrections. We also observed similar trends of fecal metabolites to previous studies; children with ASD have higher fecal p-cresol and possibly lower GABA concentrations. In addition, Fisher Discriminant Analysis (FDA) with leave-out-validation suggested that a group of metabolites-caprate, nicotinate, glutamine, thymine, and aspartate-may potentially function as a modest biomarker to separate ASD participants from the neurotypical group (78% sensitivity and 81% specificity). Consistent with our previous Arizona cohort study, we also confirmed lower gut microbial diversity and reduced relative abundances of phylotypes most closely related to Prevotella copri in children with ASD. After multiple testing corrections, we also learned that relative abundances of Feacalibacterium prausnitzii and Haemophilus parainfluenzae were lower in feces of children with ASD. Despite a relatively short list of fecal metabolites, the data in this study support that children with ASD have altered metabolite profiles in feces when compared with neurotypical children and warrant further investigation of metabolites in larger cohorts.

Reversible cyanovinylcarbazole-based polymer gel via photo-cross-linking reaction

A polymeric gel was prepared from a bis(3-cyanovinylcarbazole)-based derivative and a thymine-bearing calix[4]arene derivative via photo-cross-linking between 3-cyanovinylcarbazole and thymine groups by irradiation with 365 nm UV light, a novel and facile method to obtain a soft material. Values for storage and loss moduli of the bis(3-cyanovinylcarbazole)-based derivative and the thymine-bearing calix[4]arene derivative gradually increased during photoirradiation. This gel was transformed back to the solution state by decomposition of the polymer network to the monomers via irradiation with 312 nm UV light.

Distinctive Klf4 mutants determine preference for DNA methylation status.

Reprogramming of mammalian genome methylation is critically important but poorly understood. Klf4, a transcription factor directing reprogramming, contains a DNA binding domain with three consecutive C2H2 zinc fingers. Klf4 recognizes CpG or TpG within a specific sequence. Mouse Klf4 DNA binding domain has roughly equal affinity for methylated CpG or TpG, and slightly lower affinity for unmodified CpG. The structural basis for this key preference is unclear, though the side chain of Glu446 is known to contact the methyl group of 5-methylcytosine (5mC) or thymine (5-methyluracil). We examined the role of Glu446 by mutagenesis. Substituting Glu446 with aspartate (E446D) resulted in preference for unmodified cytosine, due to decreased affinity for 5mC. In contrast, substituting Glu446 with proline (E446P) increased affinity for 5mC by two orders of magnitude. Structural analysis revealed hydrophobic interaction between the proline's aliphatic cyclic structure and the 5-methyl group of the pyrimidine (5mC or T). As in wild-type Klf4 (E446), the proline at position 446 does not interact directly with either the 5mC N4 nitrogen or the thymine O4 oxygen. In contrast, the unmethylated cytosine's exocyclic N4 amino group (NH2) and its ring carbon C5 atom hydrogen bond directly with the aspartate carboxylate of the E446D variant. Both of these interactions would provide a preference for cytosine over thymine, and the latter one could explain the E446D preference for unmethylated cytosine. Finally, we evaluated the ability of these Klf4 mutants to regulate transcription of methylated and unmethylated promoters in a luciferase reporter assay.

Hydrogen Bonding in a Reversible Comb Polymer Architecture: A Microscopic and Macroscopic Investigation

In this work, an investigation of the hydrogen-bonding mechanism in a transiently branched comb-like polymer system in the melt is reported. The system under investigation consists of a polybutylene oxide (PBO)-based backbone, randomly functionalized with thymine (thy) groups, in combination with shorter PBO graft chains, end-functionalized with diaminotriazine (DAT) groups. The functional groups are able to associate through hydrogen bonding. The heterocomplementary association of these groups leads to the formation of a transiently branched comb-like polymer system. Since recently virtually exclusive heterocomplementary association could be observed in the supramolecular association of telechelically modified oligomeric PEG chains, here we aim to extend the supramolecular assembly mechanism toward branched structures. The present work combines small angle neutron scattering (SANS) experiments on a selectively labeled system with macroscopic dynamics measured in linear rheology response. The association ...

Selective adsorption of modified nucleoside cancer biomarkers by hybrid molecularly imprinted adsorbents.

Modified adenosine nucleosides have been proposed to be potential DNA-based biomarkers for early diagnosis of tumor and a promising tool for the development of noninvasive prediction systems. However, the low concentration of modified adenosine nucleosides in physiological fluids makes them challenging for both quantitative and qualitative determination. Therefore, materials, which are potentially useful for selective adsorption of nucleobase-containing compounds, were obtained. To obtain the adsorbents, the silica gel particles were coated layer-by-layer with films of the polymers with different combinations of polymers containing thymine groups. Next, the microspheres were irradiated with UV light in the presence of 2'-deoxyadenosine or 5'-deoxy-5'-(methylthio)adenosine, as template molecules, which resulted in the photodimerization of thymine moieties and molecular imprinting of adsorbed modified adenosine compounds. The selectivity of the adsorption was significantly enhanced by the photoimprinting process. Eventually, the imprinted particles have shown an improved ability to recognize mainly 2'-deoxyadenosine and 5'-deoxy-5'-(methylthio)adenosine molecules. The best performing adsorbent was obtained using modified natural polysaccharides. The studied materials could serve as promising adsorbents of biomarkers for tumor diagnostics.