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ABSTRACT: We report here the characterization of twelve halobenzoquinones (HBQs) using electrospray ionization (ESI) high resolution quadrupole time-of-flight mass spectrometry. The high resolution negative ESI spectra of the twelve HBQs formed two parent ions, [M+H++2e-], and the radical M-.. The intensities of these two parent ions are dependent on their chemical structures and on instrumental parameters such as the source temperature and flow rate. The characteristic ions of the HBQs were used to develop an ultra pressure liquid chromatography ─ tandem mass spectrometry (UPLC-MS/MS) method. At the UPLC flow rate (400 µL/min) and under the optimized ESI conditions, eleven HBQs showed the stable and abundant transitions [M+H++2e-] →X- (X- representing Cl-, Br-, or I-), while dibromo-dimethyl-benzoquinone (DBDMBQ) showed only the transition of M-.→Br-. The UPLC efficiently separates all HBQs including some HBQ isomers, while the MS/MS offers exquisite limits of detection (LODs) at sub-ng/mL levels for all HBQs except DBDMBQ. Combined with solid phase extraction (SPE), the method LOD is down to ng/L. The results from analysis of authentic samples demonstrated that the SPE-UPLC-MS/MS method is reliable, fast, and sensitive for the identification and quantification of the twelve HBQs in drinking water.
Analytical Chemistry 04/2013; · 5.86 Impact Factor
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ABSTRACT: Halobenzoquinones (HBQs) are a group of emerging disinfection byproducts (DBPs) found in treated drinking water. Because the use of UV treatment for disinfection is becoming more widespread, it is important to understand how the HBQs may be removed or changed due to UV irradiation. Water samples containing four HBQs, 2,6-dichloro-1,4-benzoquinones (DCBQ), 2,3,6-trichloro-1,4-benzoquinone (TCBQ), 2,6-dichloro- 3-methyl-1,4-benzoquinone (DCMBQ), and 2,6-dibromo-1,4- benzoquinone (DBBQ) were treated using a modified bench scale collimated beam device, mimicking UV treatment. Water samples before and after UV irradiation were analyzed for the parent compounds and products using a high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) method. As much as 90% of HBQs (0.25 nmol L-1) in both pure water and tap water were transformed to other products after UV254 irradiation at 1000 mJ cm-2. The major products of the four HBQs were identified as 3-hydroxyl-2,6-dichloro-1,4-benzoquinone (OH-DCBQ) from DCBQ, 5-hydroxyl-2,6-dichloro-3-methyl-1,4-benzoquinone (OH-DCMBQ) from DCMBQ, 5-hydroxyl-2,3,6-trichloro-1,4-benzoquinone (OH-TCBQ) from TCBQ and 3-hydroxyl-2,6-dibromo-1,4-benzoquinone (OH-DBBQ) from DBBQ. These four OH-HBQs were further modified to mono-halogenated benzoquinones when the UV dose was higher than 200 mJ cm-2. These results suggested possible pathways of UV-induced transformation of HBQs to other compounds. Under the UV dose commonly used in water treatment plants, it is likely that HBQs are partially converted to other halo-DBPs. The occurrence and toxicity of these mixed DBPs warrant further investigation to understand whether they pose a health risk.
Environmental Science & Technology 04/2013; · 4.80 Impact Factor
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ABSTRACT: Halobenzoquinones (HBQs) are a class of disinfection byproducts (DBPs) of health relevance. In this study, we aimed to uncover which HBQs were present in swimming pools. To achieve this goal, we developed a new method capable of determining eight HBQs while overcoming matrix effects to achieve reliable quantification. The method provided reproducible and quantitative recovery (67-102%) and detection limits of 0.03-1.2 ng/L for all eight HBQs. Using this new method, we investigated water samples from ten swimming pools and found 2,6-dichloro-1,4-benzoquinone (2,6-DCBQ) in all the pools at concentrations of 19─299 ng/L, which was as much as 100 times higher than its concentration in the input tap water (1-6 ng/L). We also identified 2,3,6-trichloro-(1,4)benzoquinone (TriCBQ), 2,3-dibromo-5,6-dimethyl-(1,4)benzoquinone (DMDBBQ), and 2,6-dibromo-(1,4)benzoquinone (2,6-DBBQ) in some swimming pools at concentrations of <0.1─11.3, <0.05─0.7, and <0.05─3.9 ng/L, respectively, but not in the input tap water. We examined several factors to determine why HBQ concentrations in pools were much higher than in the input tap water. Higher dissolved organics (DOC), higher doses of chlorine and higher temperatures enhanced the formation of HBQs in the pools. In addition, we conducted laboratory disinfection experiments and discovered that personal care products (PCPs) such as lotions and sunscreens can serve as precursors to form additional HBQs, such as TriCBQ, 2,6-dichloro-3-methyl-(1,4)benzoquinone (DCMBQ), and 2,3,5,6-tetrabromo-(1,4)benzoquinone (TetraB-1,4-BQ). These results explained why some HBQs existed in swimming pools but not in the input water. This study presents the first set of occurrence data, identification of new HBQ DBPs, and the factors for their enhanced formation in the swimming pools.
Environmental Science & Technology 02/2013; · 4.80 Impact Factor
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ABSTRACT: Four halobenzoquinones (HBQs), 2,6-dichloro-1,4-benzoquinone (DCBQ), 2,6-dichloro-3-methyl-1,4-benzoquinone (DCMBQ), 2,3,6-trichloro-1,4-benzoquinone (TCBQ), and 2,6-dibromobenzoquinone (DBBQ), have been recently confirmed as disinfection byproducts (DBPs) in drinking water; however, their toxicological information is scarce. Here, we report that HBQs are cytotoxic to T24 bladder cancer cells and that the IC50 values are 95 µM for DCBQ, 110 µM for DCMBQ, 151 µM for TCBQ, and 142 µM for DBBQ, after a 24 h exposure. The antioxidant N-acetyl-L-cysteine (NAC) significantly reduces the cytotoxicity induced by the four HBQs, supporting the hypothesis that oxidative stress contributes to the cytotoxicity of HBQs. To further explore oxidative mechanisms of cytotoxicity, we examined HBQ-induced production of reactive oxygen species (ROS) in T24 cells, and measured 8-hydroxydeoxyguanosine (8-OHdG), protein carbonyls, and malondialdehyde (MDA) adducts of proteins, markers of oxidative damage to DNA, proteins, and lipids, respectively. All four HBQs generated intracellular ROS in T24 cells in a concentration-dependent manner. HBQs also produced 8-OHdG in genomic DNA of T24 cells, with the highest levels of 8-OHdG induced by DCMBQ. Protein carbonylation was significantly increased in T24 cells that were incubated with each of the four HBQs for 24 h. However, MDA adduct formation, a marker of lipid peroxidation, was not affected by any of the four HBQs tested. These results suggest that the ROS-induced oxidative damage to DNA and protein carbonylation is involved in the observed toxicity of HBQs in T24 cells.
Environmental Science & Technology 02/2013; · 4.80 Impact Factor
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ABSTRACT: Dynamic DNA assemblies, including catalytic DNA circuits, DNA nanomachines, molecular translators, and reconfigurable nanostructures, have shown promising potentials to regulate cell functions, deliver therapeutic reagents, and amplify detection signals for molecular diagnostic and imaging. However, such applications of dynamic DNA assembly systems have been limited to nucleic acids and a few small molecules, due to the limited approaches to trigger the DNA assemblies. Herein, we describe a binding-induced DNA strand displacement strategy that can convert protein binding to the release of a pre-designed output DNA at room temperature with high conversion efficiency and low background. This strategy allows us to construct dynamic DNA assembly systems that are able to respond to specific protein binding, opening an opportunity to initiate dynamic DNA assemblies by proteins.
Journal of the American Chemical Society 01/2013; · 9.91 Impact Factor
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ABSTRACT: A simple, novel "one-pot" approach was developed for the preparation of organic-silica hybrid monoliths. Two clickable monoliths functionalized with either azido or alkynyl moieties were prepared. The clickable monoliths were further used for the fabrication of enzyme reactors via "click chemistry".
Chemical Communications 01/2013; · 6.17 Impact Factor
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ABSTRACT: Halo-benzoquinones (HBQs) have been previously detected as disinfection by-products in chlorinated drinking water. The current work investigates the link between natural organic matter (NOM) characteristics and HBQ formation during bench-scale coagulation of raw water. Three source waters (Lake Ontario, Otonabee River and Grand River) were subjected to jar testing using alum followed by chlorination. NOM fractions were analyzed via liquid chromatography-organic carbon detection (LC-OCD), while HBQs were quantified using liquid chromatography-triple quadrupole mass spectrometry. One HBQ, 2,6-dichloro-(1,4)benzoquinone (2,6-DCBQ), was identified in all waters after chlorination, and appeared to decrease with increased applied alum dose. 2,6-DCBQ exhibited high correlations with some humic NOM indicators: humic substance concentration (in Grand and Otonabee River waters only), UV absorbance at 254 nm, UV absorbance at 254 nm of the humic peak, and specific UV absorbance of humics (humic SUVA). With data pooled from the three waters, the biopolymer fraction of NOM was most strongly correlated with 2,6-DCBQ formation (R(2) = 0.78, p < 0.001); this may be due to co-removal of biopolymers with HBQ precursors during coagulation. These results indicate that coagulation processes can be effective for reduction, but not elimination, of HBQ precursors.
Water Research 01/2013; · 4.86 Impact Factor
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Chemical Reviews 12/2012; · 40.20 Impact Factor
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ABSTRACT: We describe a single-cycle DNA aptamer selection strategy that is able to obtain high affinity aptamers (K(d) of sub-nM) directly from a protein blotted on membrane. The key to the success of this strategy is the unique use of DNase I digestion to remove unwanted ssDNA from the membrane, leaving only the strongest bound aptamers. A crude Hepatitis B virus core protein (HBcAg) was separated using polyacrylamide gel electrophoresis (PAGE) and electro-blotted onto a polyvinylidene fluoride (PVDF) membrane. The membrane strip containing HBcAg and a second membrane strip containing human serum proteins were coincubated with a ssDNA library consisting of ∼10 copies each of 10(15) random sequences. Unbound and weakly bound sequences were efficiently removed from the membrane containing HBcAg using DNase I digestion and gradient wash with urea buffers. The remaining ssDNA bound to the target consisted of approximately 500 molecules, from which two aptamers with high affinity (K(d) ∼100 and 200 pM) were identified. This technique can be potentially used for selection of aptamers directly from multiple proteins that are separated by gel electrophoresis from a biological mixture.
Analytical Chemistry 08/2012; 84(18):7603-6. · 5.86 Impact Factor
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ABSTRACT: Protein in, DNA out: A "binding-induced molecular translator" is able to convert an input target protein into an output DNA that can be readily detected and potentially be used to assemble DNA nanodevices. Successful molecular translation is mediated by binding-induced DNA assembly on a gold nanoparticle (AuNP) scaffold, thereby achieving efficient target-dependent strand displacement.
Angewandte Chemie International Edition 08/2012; 51(37):9317-20. · 13.45 Impact Factor
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ABSTRACT: Nucleic-acid aptamers are promising affinity ligands in affinity chromatography. The relatively small size of aptamers and their ease of chemical conjugation to chromatographic supports make high-density aptamer columns useful for affinity separation. Other key features of aptamers pertinent to their applications in affinity chromatography include their good stability, high purity, and desirable binding properties. This article describes the current status of aptamer affinity chromatography (AAC) in separation, extraction, purification and detection of targets of interest, ranging from small molecules to proteins and cells. Further development and applications of AAC can benefit from the recent advances in aptamer-selection techniques, chromatographic stationary-phase supports, nanomaterials and microfluidic manipulations.
TrAC Trends in Analytical Chemistry 08/2012; · 6.27 Impact Factor
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ABSTRACT: Consumption of chlorinated drinking water has shown somewhat consistent association with increased risk of bladder cancer in a series of epidemiological studies, but plausible causative agents have not been identified. Halobenzoquinones (HBQs) have been recently predicted as putative disinfection byproducts (DBPs) that might be of toxicological relevance. This study reports the occurrence frequencies and concentrations of HBQs in plant effluents from nine drinking water treatment plants in the USA and Canada, where four common disinfection methods, chlorination, chloramination, chlorination with chloramination, and ozonation with chloramination, are used. In total, 16 water samples were collected and analyzed for eight HBQs: 2,6-dichloro-1,4-benzoquinone (2,6-DCBQ), 2,6-dibromo-1,4-benzoquinone (2,6-DBBQ), 2,6-dichloro-3-methyl-1,4-benzoquinone (2,6-DC-3-MBQ), 2,3,6-trichloro-1,4-benzoquinone (2,3,6-TriCBQ), 2,5-dibromo-1,4-benzoquinone (2,5-DBBQ), 2,3-dibromo-5,6-dimethyl-1,4-benzoquinone (2,3-DB-5,6-DM-BQ), tetrabromo-1,4-benzoquinone (TetraB-1,4-BQ), and tetrabromo-1,2-benzoquinone (TetraB-1,2-BQ). Of these, 2,6-DCBQ, 2,6-DBBQ, 2,6-DC-3-MBQ and 2,3,6-TriCBQ were detected in 16, 11, 6, and 3 of the 16 samples with the method detection limit (DL) of 1.0, 0.5, 0.9 and 1.5 ng/L, respectively, using a solid phase extraction and high performance liquid chromatography-tandem mass spectrometry method. The concentrations were in the ranges of 4.5-274.5 ng/L for 2,6-DCBQ, below DL to 37.9 ng/L for 2,6-DBBQ, below DL to 6.5 ng/L for 2,6-DC-3-MBQ, and below DL to 9.1 ng/L for 2,3,6-TriCBQ. These authentic samples show DCBQ and DBBQ as the most abundant and frequently detectable HBQs. In addition, laboratory controlled experiments were performed to examine the formation of HBQs and their subsequent stability toward hydrolysis when the disinfectants, chlorine, chloramine, or ozone followed by chloramines, reacted with phenol (a known precursor) under various conditions. The controlled reactions demonstrate that chlorination produces the highest amounts of DCBQ, while pre-ozonation increases the formation of DBBQ in the presence of bromide. At pH < 6.8, 2,6-DCBQ was observed to be stable, but it was easily hydrolyzed to form mostly 3-hydroxyl-2,6-DCBQ at pH 7.6 in drinking water.
Water Research 06/2012; 46(14):4351-60. · 4.86 Impact Factor
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ABSTRACT: Peptide profiles: The use of mesoporous materials, such as ordered mesoporous carbon, improves the efficiency and selectivity of peptide extraction for profiling complicated samples. Controling the pore size of such mesoporous materials during synthesis allows specific molecular weight cut-offs to be introduced, which can eliminate a large number of interfering entities, such as serum proteins.
Angewandte Chemie International Edition 02/2012; 51(15):3518-9. · 13.45 Impact Factor
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ABSTRACT: We describe the binding-induced DNA assembly principle and strategy that enable ultrasensitive detection of molecular targets and potential construction of unique nanostructures/nanoreactors. Two DNA motifs that are conjugated to specific affinity ligands assemble preferentially only when a specific target triggers a binding event. The binding-induced assembly of the DNA motifs results in the formation of a highly stable closed-loop structure, raising the melting temperature (T(m)) of the hybrid by >30 °C and enabling effective differentiation of the target-specific assembly from the background. The ability to detect as few as a hundred molecules (yoctomole) of streptavidin, platelet derived growth factor, and prostate specific antigen represents an improvement of detection limits by 10(3)-10(5)-fold over traditional immunoassays. The assay is performed in a single tube, eliminating separation, immobilization, and washing steps of conventional assays. By incorporating unique signaling and structural features into the DNA motifs, we envision diverse applications in biosensing and nanotechnology.
Analytical Chemistry 01/2012; 84(2):877-84. · 5.86 Impact Factor
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ABSTRACT: Activity and specificity of enzyme molecules are important to enzymatic reactions and enzyme assays. We describe an aptamer capturing approach that improves the specificity and the sensitivity of enzyme detection. An aptamer recognizing the target enzyme molecule is conjugated on a magnetic bead, increasing the local concentration, and serves as an affinity probe to capture and separate minute amounts of the enzyme. The captured enzymes catalyze the subsequent conversion of fluorogenic substrate to fluorescent products, enabling a sensitive measure of the active enzyme. The feasibility of this technique is demonstrated through assays for human alpha thrombin and human neutrophil elastase (HNE), two important enzymes. Thrombin (2 fM) and 100 fM HNE can be detected. The incorporation of two binding events, substrate recognition and aptamer binding, greatly improves assay specificity. With its simplicity, this approach is applicable to biosensing and detection of disease biomarkers.
Analytical Chemistry 11/2011; 83(24):9234-6. · 5.86 Impact Factor
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ABSTRACT: We report the use of electrospray ionization tandem mass spectrometry (ESI-MS/MS) as a tool for rapid screening of structurally related chemicals toward oligonucleotides using the binding of five bromobenzoquinones with single-stranded (ss) and double-stranded (ds) oligonucleotides (ODNs) as a model. We found that these compounds interact differentially with oligonucleotides depending on the extent of their bromination and methylation. Three dibromobenzoquinones, 2,6-dibromo-1,4-benzoquinone (2,6-DBBQ), 2,5-dibromo-1,4-benzoquinone (2,5-DBBQ), and 2,5-dimethyl-3,6-dibromo-1,4-benzoquinone (DMDBBQ), bound to ssODN to form 1:1 adducts, and the binding constant of DMDBBQ bound to ssODN was 100-fold lower than those of 2,6-DBBQ and 2,5-DBBQ to ssODN, indicating that methyl groups hindered interactions of the bromoquinones with ODNs. Collision-induced dissociation (CID) of the 1:1 and 1:2 adducts of ODN with 2,6-DBBQ and 2,5-DBBQ demonstrated neutral loss of DBBQ and charge separations. Incubation of two tetrabromobenzoquinones (TBBQ), 2,3,5,6-tetrabromo-1,4-benzoquinone and 3,4,5,6-tetrabromo-1,2-benzoquinone, with the same ODNs did not form any adducts of TBBQ with ssODN or dsODN; however, bromide-ODNs were detected. Fragmentation of the bromide-ODN adducts showed loss of the HBr molecule, supporting the presence of bromide on ODNs. High-resolution MS and MS/MS analysis of the mixtures of dinucleotides (AA, GG, CC, and TT) and TBBQ confirmed the presence of bromide on the dinucleotides, supporting the transfer of bromide to ODNs through interaction with TBBQ. This study presents evidence of differential interactions of structurally related bromo and methyl-benzoquinones with oligonucleotides and demonstrates a potential application of ESI-MS/MS analysis of chemical interactions with ODN for rapid screening of the reactivity of other structurally related environmental contaminants toward DNA.
Analytical Chemistry 09/2011; 83(21):8145-51. · 5.86 Impact Factor
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ABSTRACT: Functionalization and control of nanoparticle surface are critical to the desirable application of nanoparticles. We describe a DNA assembly method that dynamically protects aptamer-functionalized gold nanoparticles (apt-AuNP) from nondesirable binding to interfering molecules. Competitive protection of the apt-AuNP was achieved by using a carefully designed DNA that served two primary functions: reducing cross-reaction by competitive hybridization to the aptamer and overcoming nonspecific adsorption by restricted access to the AuNP surface. Tuning the length and sequence of the hybridization and the overhang components of the protection DNA allowed for control of the selectivity of apt-AuNP probes for the target protein. Alternating application of the protection DNA containing a polyA and polyT overhang enabled layer-by-layer formation of the supermolecular assembly. This directed assembly of apt-AuNP resulted in enhancement of signal for visual detection of minute amounts of proteins. This method was successfully demonstrated for Western blot analysis of thrombin, with an improved detection limit of 6 ng. This study demonstrates a unique dynamic protection strategy for achieving high specificity and sensitivity in the detection of protein.
Analytical Chemistry 07/2011; 83(17):6464-7. · 5.86 Impact Factor
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ABSTRACT: This paper describes the selection of high affinity DNA aptamers binding to multiple M-types of the pathogenic species Streptococcus pyogenes (Group A Streptococcus or GAS). Unlike common aptamer selection techniques that use purified molecules of a monoclonal cell population as targets, this work has achieved the selection of aptamers against the various M-types of S. pyogenes. Cell mixtures containing equal numbers of the 10 most prevalent S. pyogenes M-types were incubated with 80-nucleotide DNA libraries, centrifuged, and washed to separate cell-bound from unbound DNA sequences. The DNA bound to the cells was amplified using the polymerase chain reaction, and the amplicons were tested for their binding to the target cells. The amplicons were also used as new DNA libraries for subsequent rounds of selection. Cloning, sequencing, and subsequent analysis of selected aptamers showed that they bind preferentially to GAS over other common and related bacteria. Resultant DNA aptamers showed strong and preferential binding to GAS, including the 10 most prevalent GAS M-types and another 10 minor M-types tested. Estimated K(d) values were in the range of 4 to 86 nM. Two aptamers, 20A24P and 15A3P (with estimated binding dissociation constants of 9 and 10 nM, respectively), are particularly promising. These aptamers could potentially be used to improve the detection of GAS, a pathogen that is the causative agent of many infectious diseases, most notably strep throat.
Analytical Chemistry 05/2011; 83(10):3640-7. · 5.86 Impact Factor
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ABSTRACT: Four halobenzoquinones, 2,6-dibromo-1,4-benzoquinone, 2,6-dichloro-1,4-benzoquinone, 2,6-dichloro-3-methyl-1,4-benzoquinone, and 2,3,6-trichloro-1,4-benzoquinone, were recently identified as drinking water disinfection byproducts. Understanding their interactions with biomolecules could provide useful insights into their potential toxic effects. We report here electrospray ionization mass spectrometry characterization of the interactions between these new halobenzoquinone disinfection byproducts and oligodeoxynucleotides. The study demonstrates that 2,6-dibromo-1,4-benzoquinone exhibits much stronger binding to single- and double-stranded oligodeoxynucleotides than chlorobenzoquinones. The binding affinity of 2,6-dibromo-1,4-benzoquinone to oligodeoxynucleotides is similar to that of ethidium bromide, a well-known intercalator and carcinogen. Tandem mass spectrometry characterization confirms the formation of 1:1 and 2:1 complexes of 2,6-dibromo-1,4-benzoquinone binding to oligodeoxynucleotides. Collision-induced dissociation analysis of these adducts demonstrates neutral loss and charge separation, suggesting that 2,6-dibromo-1,4-benzoquinone binds to oligodeoxynucleotides through partial intercalation and H-bonding modes. The three chlorobezoquinones also form 1:1 adducts with the oligodeoxynucleotides, but their binding to the oligodeoxynucleotides was much weaker compared to that of 2,6-dibromo-1,4-benzoquinone. The relative binding affinity of the studied disinfection byproducts to oligodeoxynucleotides is in the order of 2,6-dibromo-1,4-benzoquinone≫2,6-dichloro-1,4-benzoquinone > 2,6-dichloro-3-methyl-1,4-benzoquinone ∼ 2,3,6-trichloro-1,4-benzoquinone, indicating potential structural effects on the interactions of halobenzoquinones with oligodeoxynucleotides.
Environmental Science & Technology 11/2010; 44(24):9557-63. · 4.80 Impact Factor
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ABSTRACT: Biomarker assays may be useful for screening and diagnosis of cancer if a set of molecular markers can be quantified and statistically differentiated between cancerous cells and healthy cells. Markers of disease are often present at very low concentrations, so methods capable of low detection limits are required. Quantum dots (QDs) are nanoparticles that are emerging as promising probes for ultrasensitive detection of cancer biomarkers. QDs attached to antibodies, aptamers, oligonucleotides, or peptides can be used to target cancer markers. Their fluorescent properties have enabled QDs to be used as labels for in-vitro assays to quantify biomarkers, and they have been investigated as in-vivo imaging agents. QDs can be used as donors in assays involving fluorescence resonance energy transfer (FRET), or as acceptors in bioluminescence resonance energy transfer (BRET). The nanoparticles are also capable of electrochemical detection and are potentially useful for "lab-on-a-chip" applications. Recent developments in silicon QDs, non-blinking QDs, and QDs with reduced-size and controlled-valence further make these QDs bioanalytically attractive because of their low toxicity, biocompatibility, high quantum yields, and diverse surface modification flexibility. The potential of multiplexed sensing using QDs with different wavelengths of emission is promising for simultaneous detection of multiple biomarkers of disease.
Analytical and Bioanalytical Chemistry 08/2010; 397(8):3213-24. · 3.78 Impact Factor
