Pattern‐Based Detection of Toxic Metals in Surface Water with DNA Polyfluorophores

Heavy metal contamination of water can be toxic to humans and wildlife; thus the development of methods to detect this contamination is of high importance. Here we describe the design and application of DNA‐based fluorescent chemosensors on microbeads to differentiate eight toxic metal ions in water. We developed and synthesized four fluorescent 2′‐deoxyribosides of metal‐binding ligands. A tetramer‐length oligodeoxy‐fluoroside (ODF) library of 6561 members was constructed and screened for sequences responsive to metal ions, of which seven sequences were selected. Statistical analysis of the response patterns showed successful differentiation of the analytes at concentrations as low as 100 nM . Sensors were able to classify water samples from 13 varied sites and quantify metal contamination in unknown specimens. The results demonstrate the practical potential of bead‐based ODF chemosensors to analyze heavy metal contamination in water samples by a simple and inexpensive optical method.     

Commutability of reference materials in clinical chemistry.

The term commutability applied to reference materials denotes the ability of the material to show interassay changes comparable to those observed in the measurement of the same analyte in human serum. In this study commutability was studied by first establishing the relationship between the results obtained on patient serum samples with two independent methods for a given analyte. Then, the calibration or control material was assayed with the same pair of methods, and its interassay bias was statistically compared with that shown by patient sera. The results obtained in 27 experiments showed that the frequencies of noncommutability in the measurement of some nonenzymic organic components, enzymes, and inorganic ions were, respectively, 25/83, 44/99, and 32/61. The impact of noncommutability of the materials on the results of external quality assessment schemes (EQAS), matrix interferences, and the behavior of particular components are considered. The conclusion drawn is that each material should be tested for commutability before it is used as a reference material.     

Organometallic activation of a fluorogen for templated nucleic acid detection

A nucleic acid detection scheme that employs DNA-mediated delivery of an organomercury activator to unmask a fluorophore is described. The approach relies on adjacent hybridization of two oligonucleotide conjugates containing organomercury and caged rhodamine functionalities. Postsynthetic conjugation of amino-modified DNAs enabled efficient preparation of these probes. Complementary DNA templates yielded fluorescence signals arising from metal-assisted rhodamine uncaging.     

Two successive reactions on a DNA template: a strategy for improving background fluorescence and specificity in nucleic acid detection

We report a new strategy for template-mediated fluorogenic chemistry that results in enhanced performance for the fluorescence detection of nucleic acids. In this approach, two successive templated reactions are required to induce a fluorescence signal, rather than only one. These novel fluorescein-labeled oligonucleotide probes, termed 2-STAR (STAR = Staudinger-triggered α-azidoether release) probes, contain two quencher groups tethered by separate reductively cleavable linkers. When a 2-STAR quenched probe successively binds adjacent to two mono-triphenylphosphine-(TPP)-DNAs or one dual-TPP-DNA, the two quenchers are released, resulting in a fluorescence signal. Because of the requirement for two consecutive reactions, 2-STAR probes display an unprecedented level of sequence specificity for template-mediated probe designs. At the same time, background emission generated by off-template reactions or incomplete quenching is among the lowest of any fluorogenic reactive probes for the detection of DNA or RNA.