Imaging single DNA molecules for high precision NIPT.

Cell-free DNA analysis is becoming adopted for first line aneuploidy screening, however for most healthcare programs, cost and workflow complexity is limiting adoption of the test. We report a novel cost effective method, the Vanadis NIPT assay, designed for high precision digitally-enabled measurement of chromosomal aneuploidies in maternal plasma. Reducing NIPT assay complexity is achieved by using novel molecular probe technology that specifically label target chromosomes combined with a new readout format using a nanofilter to enrich single molecules for imaging and counting without DNA amplification, microarrays or sequencing.

Rapid identification of bio-molecules applied for detection of biosecurity agents using rolling circle amplification.

Detection and identification of pathogens in environmental samples for biosecurity applications are challenging due to the strict requirements on specificity, sensitivity and time. We have developed a concept for quick, specific and sensitive pathogen identification in environmental samples. Target identification is realized by padlock- and proximity probing, and reacted probes are amplified by RCA (rolling-circle amplification).

Proximity ligation assays: a recent addition to the proteomics toolbox.

An essential skill for every researcher is to learn how to select and apply the most appropriate methods for the questions they are trying to answer. With the extensive variety of methods available, it is increasingly important to scrutinize the advantages and disadvantages of these techniques prior to making a decision on which to use. In this article, we describe an approach to evaluate methods by reducing them into subcomponents.

Glycosylases and AP-cleaving enzymes as a general tool for probe-directed cleavage of ssDNA targets.

The current arsenal of molecular tools for site-directed cleavage of single-stranded DNA (ssDNA) is limited. Here, we describe a method for targeted DNA cleavage that requires only the presence of an A nucleotide at the target position. The procedure involves hybridization of a complementary oligonucleotide probe to the target sequence.

A single molecule array for digital targeted molecular analyses.

We present a new random array format together with a decoding scheme for targeted multiplex digital molecular analyses. DNA samples are analyzed using multiplex sets of padlock or selector probes that create circular DNA molecules upon target recognition. The circularized DNA molecules are amplified through rolling-circle amplification (RCA) to generate amplified single molecules (ASMs).

A dual-tag microarray platform for high-performance nucleic acid and protein analyses.

DNA microarrays serve to monitor a wide range of molecular events, but emerging applications like measurements of weakly expressed genes or of proteins and their interaction patterns will require enhanced performance to improve specificity of detection and dynamic range. To further extend the utility of DNA microarray-based approaches we present a high-performance tag microarray procedure that enables probe-based analysis of as little as 100 target cDNA molecules, and with a linear dynamic range close to 10(5). Furthermore, the protocol radically decreases the risk of cross-hybridization on microarrays compared to current approaches, and it also allows for quantification by single-molecule analysis and real-time on-chip monitoring of rolling-circle amplification.

Detection of DNA hybridization using induced fluorescence resonance energy transfer.

Induced fluorescence resonance energy transfer (iFRET) is a variation of resonance energy transfer that is particularly well-suited for the detection of DNA hybridization. The underlying mechanism involves monitoring changes in fluorescence that are the result of an energy transfer reaction between a specific pair of donor and acceptor moieties. In iFRET, the donor is a dye that only fluoresces while interacting with double-stranded DNA and the acceptor is dye that is covalently linked to an oligonucleotide probe.

Scoring insertion-deletion polymorphisms by dynamic allele-specific hybridization.

Genome variation provides researchers with thousands of markers with which to study human demographic history and phenotypes. Insertion-deletion (indel) polymorphism is an important and abundant form of human genome variation, and convenient methods for genotyping indels are therefore needed. Here we evaluate dynamic allele-specific hybridization (DASH) for its ability to score indels.

DASH-2: flexible, low-cost, and high-throughput SNP genotyping by dynamic allele-specific hybridization on membrane arrays.

Genotyping technologies need to be continually improved in terms of their flexibility, cost-efficiency, and throughput, to push forward genome variation analysis. To this end, we have leveraged the inherent simplicity of dynamic allele-specific hybridization (DASH) and coupled it to recent innovations of centrifugal arrays and iFRET. We have thereby created a new genotyping platform we term DASH-2, which we demonstrate and evaluate in this report.

iFRET: an improved fluorescence system for DNA-melting analysis.

Fluorescence resonance energy transfer (FRET) is a powerful tool for detecting spatial relationships between macromolecules, one use of which is the tracking of DNA hybridization status. The process involves measuring changes in fluorescence as FRET donor and acceptor moieties are brought closer together or moved farther apart as a result of DNA hybridization/denaturation. In the present study, we introduce a new version of FRET, which we term induced FRET (iFRET), that is ideally suited for melting curve analysis.

Evaluation of multiple presenilin 2 SNPs for association with early-onset sporadic Alzheimer disease.

The presenilin genes encode proteins that modify, mediate, or perform similar functions to gamma-secretase, the enzyme responsible for converting amyloid beta precursor protein (APP) into beta-amyloid. Mutations in the presenilin genes cause an increased production of Abeta42, the aberrant form of beta-amyloid found in the neural plaques of Alzheimer disease patients. Previously reported association studies of presenilin 2 (PSEN2) polymorphisms with early-onset Alzheimer disease (EOAD) have produced contradictory results.

Creating arrays by centrifugation.

We describe afast, low-cost, and reliable way of creating arrays from sample molecules of interest present within microformatted sample vessels (such as 1536-well microplates). The principle involves simple centrifugal transfer of molecules of interest onto a solid planar or membrane surfaces placed over the initial sample vessel. Tools and procedures are presented that validate the robustness and precision of this facile solution to an otherwise difficult problem in modern molecular genetics.