胡椒基咪唑盐类化合物的合成及生物活性研究

从胡椒酸出发,通过还原、甲磺酸酯化、偶联和成盐四步反应合成了-系列新型的胡椒基咪唑盐类化合物,其结构经1H NMR,13C NMR,HRMS以及X射线单晶衍射确定.对合成的新化合物进行了体外抗肿瘤细胞毒活性筛选,结果表明,1-((苯并[d][1,3]二氧杂环戊烯-5-基甲基)-3-(2-萘甲基))-5,6-二甲基-1H-苯并[d]咪唑-3-溴盐(30)具有显著的细胞毒活性,对HL-60、SMMC-7721、A-549、MCF-7和SW-480肿瘤细胞株的活性均优于顺铂(DDP),尤其对HL-60肿瘤细胞株表现出较好的选择性细胞毒活性,其IC50值约为顺铂的7.2倍.进一步研究表明,化合物30具有诱导SMMC-7721细胞株在细胞周期G0/G1期阻滞和细胞凋亡的作用.     

Effects of charging and doping on orbital hybridizations and distributions in TiO2 clusters

Charging and doping are two important strategies used in TiO₂ quantum dots for photocatalysis and photovoltaics. Using small clusters as the prototypes for quantum dots, we have carried out density functional calculations to study the size-specific effects of charging and doping on geometry, electronic structure, frontier orbital distribution, and orbital hybridization. We find that in neutral (TiO₂)_n clusters the charge transfer from Ti to O is almost size independent, while for the anionic (TiO₂)_n clusters the corresponding charge transfer is reduced but it increases with size. When one O atom is substituted with N, the charge transfer is also reduced due to the smaller electron affinity of N. As the cluster size increases, the populations of 3d and 4s orbitals of Ti decrease with size, while the populations of the 4p orbital increase, suggesting size dependence of spd hybridizations. The present study clearly shows that charging and doping are effective ways for tailoring the energy gap, orbital distributions, and hybridizations.     

Highly sensitive disposable nucleic acid biosensors for direct bioelectronic detection in raw biological samples

The development of rapid, low-cost and reliable diagnostic methods is crucial for the identification and treatment of many diseases. Screen-printed gold electrodes (Au/SPEs), coated with a ternary monolayer interface, involving hexanedithiol (HDT), a specific thiolated capture probe (SHCP), and 6-mercapto-1 hexanol (MCH) (SHCP/HDT/MCH) are shown here to offer direct and sensitive detection of nucleic acid hybridization events in untreated raw biological samples (serum, urine and crude bacterial lysate solutions). The composition of the ternary monolayer was modified and tailored to the surface of the Au/SPE. The resulting SHCP/HDT/MCH monolayer has demonstrated to be extremely useful for enhancing the performance of disposable nucleic acid sensors based on screen-printed electrodes. Compared to common SHCP/MCH binary interfaces, the new ternary self-assembled monolayer (SAM) resulted in a 10-fold improvement in the signal (S)-to-noise (N) ratio (S/N) for 1 nM target DNA. The SHCP/HDT/MCH-modified Au/SPEs allowed the direct quantification of the target DNA down to 25 pM (0.25 fmol) and 100 pM (1 fmol) in undiluted/untreated serum and urine samples, respectively, and of 16S rRNA Escherichia coli (E. coli) corresponding to 3000 CFU μL⁻¹ in raw cell lysate samples. The new SAM-coated screen-printed electrodes also displayed favorable non-fouling properties after a 24 h exposure to raw human serum and urine samples, offering great promise as cost-effective nucleic acid sensors for a wide range of decentralized genetic tests.     

Determination for Enterobacter cloacae based on a europium ternary complex labeled DNA probe

The fast detection and accurate diagnosis of the prevalent pathogenic bacteria is very important for the treatment of disease. Nowadays, fluorescence techniques are important tools for diagnosis. A two-probe tandem DNA hybridization assay was designed for the detection of Enterobacter cloacae based on time-resolved fluorescence. In this work, the authors synthesized a novel europium ternary complex Eu(TTA)₃(5-NH₂-phen) with intense luminescence, high fluorescence quantum yield and long lifetime before. We developed a method based on this europium complex for the specific detection of original extracted DNA from E. cloacae. In the hybridization assay format, the reporter probe was labeled with Eu(TTA)₃(5-NH₂-phen) on the 5′-terminus, and the capture probe capture probe was covalent immobilized on the surface of the glutaraldehyde treated glass slides. The original extracted DNA of samples was directly used without any DNA purification and amplification. The detection was conducted by monitoring the fluorescence intensity from the glass surface after DNA hybridization. The detection limit of the DNA was 5 × 10⁻¹⁰ mol L⁻¹. The results of the present work proved that this new approach was easy to operate with high sensitivity and specificity. It could be conducted as a powerful tool for the detection of pathogen microorganisms in the environment.     

Transglutaminase-mediated synthesis of a DNA-(enzyme)n probe for highly sensitive DNA detection

A new synthetic strategy for DNA-enzyme conjugates with a novel architecture was explored using a natural cross-linking catalyst, microbial transglutaminase (MTG). A glutamine-donor substrate peptide of MTG was introduced at the 5-position on the pyrimidine of deoxyuridine triphosphate to prepare a DNA strand with multiple glutamine-donor sites by polymerase chain reaction (PCR). A substrate peptide that contained an MTG-reactive lysine residue was fused to the N terminus of a thermostable alkaline phoshatase from Pyrococcus furiosus (PfuAP) by genetic engineering. By combining enzymatically the substrate moieties of MTG introduced to the DNA template and the recombinant enzyme, a DNA-(enzyme)(n) conjugate with 1:n stoichiometry was successfully obtained. The enzyme/DNA ratio of the conjugate increased as the benzyloxycarbonyl-L-glutaminylglycine (Z-QG) moiety increased in the DNA template. The potential utility of the new conjugate decorated with signaling enzymes was validated in a dot blot hybridization assay. The DNA-(enzyme)(n) probe could clearly detect 10(4) copies of the target nucleic acid with the complementary sequence under harsh hybridization conditions, thereby enabling a simple detection procedure without cumbersome bound/free processes associated with a conventional hapten-antibody reaction-based DNA-detection system.     

CrAlGe: An itinerant ferromagnet with strong tunability by heat treatment

We present a comprehensive investigation on CrAlGe and realize that it is an itinerant ferromagnet with strong tunability of the Curie temperature $T_{\rm C}$ and the spontaneous moment $\mu_0$ depending on annealing heat treatment. While the value of $T_{\rm C}$ was previously reported to be 80 K with $\mu_0\approx$ 0.41$\mu_{\rm B}$, in this work the two quantities attain values as high as 170 K and 0.66$\mu_{\rm B}$, respectively. Heat treatment does not cause changes of the lattice parameters and symmetry, but results in a slight narrowing of the Bragg peaks. The strong tunability of the itinerant ferromagnetism indicates significantly tunable hybridization between the Cr 3d electrons and the conduction bands, in agreement with the dominant Cr-Al/Ge bonds of this compound. Further tuning along the same line towards even stronger or weaker itinerant ferromagnetism promises an interesting follow-up to clarify the localized-itinerant duality of the 3d electrons in this compound.     

One Mismatch Detection of DNA Hybridization Using Fluorescence Polarization

Abstract

The potential of fluorescent polarization analysis as a method for detection of mismatch DNA hybridization was investigated. The dependency of DNA hybridization rate on salt concentration was surveyed. In greater than 0.1 M NaCl, the hybridization of probe and target DNA proceeds rapidly and the reaction is complete within 3 min. Furthermore, the hybridization of probe DNA and one mismatch target DNAs was investigated. It was successfully shown that even one mismatch could be detected using fluorescence polarization analysis if the mismatch position was on the base that pairs with the probe DNA at the 5′ terminus where fluorescein isothiocyanate (FITC) is attached.     

Development of a Surface Plasmon Resonance-Based DNA Sensor and Its Application for Screening DNA-Targeted Anticancer Drugs

In this paper, we present a surface plasmon resonance (SPR)-based sensor for measuring DNA hybridization and DNA/small-molecule interactions. A mixed self-assembled monolayer (SAM) was used to optimize the biosensor sensitivity. It was observed that the mixed SAM formed by mixing 10 mM of 16-mercapto-1-hexadecanoic acid (16-MHA) and 6-mercapto-1-hexanol (6-MCH) at a 1:10 molar ratio showed the best results. Subsequently, avidin was attached to the carboxyl groups on the SAM to serve as a binding element for biotinylated single-stranded (ss)DNA. The ssDNA-coated sensor was first evaluated as a nucleic acid biosensor through a DNA-DNA hybridization assay for synthetic 28-mer ssDNA. A linear calibration curve was observed in the range of 0.25–2.5 µg/mL. Non-complementary DNA induced no significant SPR angle shift, which demonstrated the specificity of the assay. Secondly, the sensor was used to monitor the binding kinetics of DNA/small-molecule interactions in real time. The dissociation constant between immobilized DNA and sanguinarine was determined to be 8.0 × 10^?6 M. This complies with most data from the literature. In addition, the sensor could be regenerated with 0.01 M HCl and would be feasible for multiple testing. In conclusion, the experimental approach described in this study allows analysis of molecular interactions between DNA-binding drugs and selected targeted DNA sequences.     

Enhanced Electrochemical Detection of DNA Hybridization Based on Au/MWCNTs Nanocomposites

Abstract

The nanocomposites of gold nanoparticles and multi‐walled carbon nanotubes (MWCNTs) have been applied in the enhanced electrochemical detection of DNA hybridization. Gold nanoparticles coated on MWCNTs uniformly were synthesized by simply one step reaction. Target DNA was detected by the peak current difference of differential pulse voltammetry (DPV) signals of the electroactive indicator methylene blue (MB) before and after hybridization on the Au/MWCNTs modified glass carbon electrode (GCE). Due to the excellent electrical conductivity of the novel matrix, the biosensor revealed high sensitivity with the detection level down to 1.0 pM. Excellently selectivity and reproducibility were also discussed.     

Multistage isothermic sequencing by hybridization

Despite the impressive progress in many areas of biological sciences reading DNA sequences still remains one of the most important problems. One of the methods of DNA sequencing is sequencing by hybridization which is composed of two stages--the biochemical one and the computational one. Although this method is quite modern it suffers sensitivity to errors appearing in the biochemical stage. This is a motivation for developing some new variants of the method which should be more resistant to errors of these types. Two of such non-standard approaches are multistage and isothermic sequencing by hybridization. Each of the methods is less sensitive to some types of the errors appearing in the biochemical stage, in comparison to the standard version of the method, but on the other hand, they are more sensitive to remaining types of errors. However, a combination of the two approaches reduces the sensitivity of the components.