scholarly journals 48-spot single-molecule FRET setup with periodic acceptor excitation

2017 ◽  
Author(s):  
Antonino Ingargiola ◽  
Maya Segal ◽  
Angelo Gulinatti ◽  
Ivan Rech ◽  
Ivan Labanca ◽  
...  
Keyword(s):  
Real Time ◽  
High Throughput ◽  
Single Molecule ◽  
Conformational Changes ◽  
High Throughput Screening ◽  
Acquisition Time ◽  
Enzymatic Reactions ◽  
Single Molecule Fret ◽  
Array Detectors ◽  
Donor And Acceptor

Single-molecule FRET (smFRET) allows measuring distances between donor and acceptor fluorophores on the 3-10 nm range. Solution-based smFRET allows measurement of binding-unbinding events or conformational changes of dye-labeled biomolecules without ensemble averaging and free from surface perturbations. When employing dual (or multi) laser exci-tation, smFRET allows resolving the number of fluorescent labels on each molecule, greatly enhancing the ability to study heterogeneous samples. A major drawback to solution-based smFRET is the low throughput, which renders repetitive measurements expensive and hin-ders the ability to study kinetic phenomena in real-time.Here we demonstrate a high-throughput smFRET system which multiplexes acquisition by using 48 excitation spots and two 48-pixel SPAD array detectors. The system employs two excitation lasers allowing separation of species with one or two active fluorophores. The performance of the system is demonstrated on a set of doubly-labeled double-stranded DNA oligonucleotides with different distances between donor and acceptor dyes along the DNA duplex. We show that the acquisition time for accurate subpopulation identification is reduced from several minutes to seconds, opening the way to high-throughput screening applications and real-time kinetics studies of enzymatic reactions such as DNA transcription by bacterial RNA polymerase.

scholarly journals Real-time analysis of RAG complex activity in V(D)J recombination

2016 ◽  
Vol 113 (42) ◽  
pp. 11853-11858 ◽  
Author(s):  
Jennifer Zagelbaum ◽  
Noriko Shimazaki ◽  
Zitadel Anne Esguerra ◽  
Go Watanabe ◽  
Michael R. Lieber ◽  
...  
Keyword(s):  
Real Time ◽  
Single Molecule ◽  
Conformational Changes ◽  
Signal Sequence ◽  
High Mobility ◽  
Time Analysis ◽  
Complex Activity ◽  
Synaptic Complex ◽  
Single Molecule Fret ◽  
Real Time Analysis

Single-molecule FRET (smFRET) and single-molecule colocalization (smCL) assays have allowed us to observe the recombination-activating gene (RAG) complex reaction mechanism in real time. Our smFRET data have revealed distinct bending modes at recombination signal sequence (RSS)-conserved regions before nicking and synapsis. We show that high mobility group box 1 (HMGB1) acts as a cofactor in stabilizing conformational changes at the 12RSS heptamer and increasing RAG1/2 binding affinity for 23RSS. Using smCL analysis, we have quantitatively measured RAG1/2 dwell time on 12RSS, 23RSS, and non-RSS DNA, confirming a strict RSS molecular specificity that was enhanced in the presence of a partner RSS in solution. Our studies also provide single-molecule determination of rate constants that were previously only possible by indirect methods, allowing us to conclude that RAG binding, bending, and synapsis precede catalysis. Our real-time analysis offers insight into the requirements for RSS–RSS pairing, architecture of the synaptic complex, and dynamics of the paired RSS substrates. We show that the synaptic complex is extremely stable and that heptamer regions of the 12RSS and 23RSS substrates in the synaptic complex are closely associated in a stable conformational state, whereas nonamer regions are perpendicular. Our data provide an enhanced and comprehensive mechanistic description of the structural dynamics and associated enzyme kinetics of variable, diversity, and joining [V(D)J] recombination.

scholarly journals FRETBursts: An Open Source Toolkit for Analysis of Freely-Diffusing Single-Molecule FRET

2016 ◽  
Author(s):  
Antonino Ingargiola ◽  
Eitan Lerner ◽  
SangYoon Chung ◽  
Shimon Weiss ◽  
Xavier Michalet
Keyword(s):  
Open Source ◽  
Single Molecule ◽  
Conformational Changes ◽  
Single Photon ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Widespread Application ◽  
Single Molecule Fret ◽  
Donor And Acceptor ◽  
Burst Analysis

AbstractSingle-molecule Förster Resonance Energy Transfer (smFRET) allows probing intermolecular interactions and conformational changes in biomacromolecules, and represents an invaluable tool for studying cellular processes at the molecular scale. smFRET experiments can detect the distance between two fluorescent labels (donor and acceptor) in the 3–10 nm range. In the commonly employed confocal geometry, molecules are free to diffuse in solution. When a molecule traverses the excitation volume, it emits a burst of photons, which can be detected by single-photon avalanche diode (SPAD) detectors. The intensities of donor and acceptor fluorescence can then be related to the distance between the two fluorophores.While recent years have seen a growing number of contributions proposing improvements or new techniques in smFRET data analysis, rarely have those publications been accompanied by so.ware implementation. In particular, despite the widespread application of smFRET, no complete so.ware package for smFRET burst analysis is freely available to date.In this paper, we introduce FRETBursts, an open source software for analysis of freely-diffusing smFRET data. FRETBursts allows executing all the fundamental steps of smFRET bursts analysis using state-of-the-art as well as novel techniques, while providing an open, robust and welldocumented implementation. Therefore, FRETBursts represents an ideal platform for comparison and development of new methods in burst analysis.We employ modern software engineering principles in order to minimize bugs and facilitate long-term maintainability. Furthermore, we place a strong focus on reproducibility by relying on Jupyter notebooks for FRETBursts execution. Notebooks are executable documents capturing all the steps of the analysis (including data files, input parameters, and results) and can be easily shared to replicate complete smFRET analyzes. Notebooks allow beginners to execute complex workflows and advanced users to customize the analysis for their own needs. By bundling analysis description, code and results in a single document, FRETBursts allows to seamless share analysis workflows and results, encourages reproducibility and facilitates collaboration among researchers in the single-molecule community.

Highly Sensitive Detection of Paraquat with Pillar[5]arene as an aptamer in α-Hemolysin Nanopore

2021 ◽  
Author(s):  
Xiaojia Jiang ◽  
Mingsong Zang ◽  
Fei Li ◽  
Chunxi Hou ◽  
Quan Luo ◽  
...  
Keyword(s):  
Real Time ◽  
High Throughput ◽  
Single Molecule ◽  
Single Molecule Detection ◽  
Sensitive Detection ◽  
High Throughput Analysis ◽  
Throughput Analysis ◽  
The Real ◽  
Highly Sensitive ◽  
Highly Sensitive Detection

Biological nanopore-based techniques have attracted more and more attention recently in the field of single-molecule detection, because they allow the real-time, sensitive, high-throughput analysis. Herein, we report an engineered biological...

Volume Cytometry:  Microfluidic Sensor for High-Throughput Screening in Real Time

2005 ◽  
Vol 77 (5) ◽  
pp. 1290-1294 ◽  
Author(s):  
Daniel A. Ateya ◽  
Frederick Sachs ◽  
Philip A. Gottlieb ◽  
Steve Besch ◽  
Susan Z. Hua
Keyword(s):  
Real Time ◽  
High Throughput ◽  
High Throughput Screening

scholarly journals Massively parallel single-molecule telomere length measurement with digital real-time PCR

2020 ◽  
Vol 6 (34) ◽  
pp. eabb7944 ◽  
Author(s):  
Yongqiang Luo ◽  
Ramya Viswanathan ◽  
Manoor Prakash Hande ◽  
Amos Hong Pheng Loh ◽  
Lih Feng Cheow
Keyword(s):  
Telomere Length ◽  
Real Time ◽  
High Throughput ◽  
Single Molecule ◽  
Real Time Pcr ◽  
Length Distribution ◽  
Telomere Maintenance ◽  
Massively Parallel ◽  
Primary Tumors ◽  
Absolute Length

Telomere length is a promising biomarker for age-associated diseases and cancer, but there are still substantial challenges to routine telomere analysis in clinics because of the lack of a simple and rapid yet scalable method for measurement. We developed the single telomere absolute-length rapid (STAR) assay, a novel high-throughput digital real-time PCR approach for rapidly measuring the absolute lengths and quantities of individual telomere molecules. We show that this technique provides the accuracy and sensitivity to uncover associations between telomere length distribution and telomere maintenance mechanisms in cancer cell lines and primary tumors. The results indicate that the STAR assay is a powerful tool to enable the use of telomere length distribution as a biomarker in disease and population-wide studies.

scholarly journals Using single-molecule FRET to probe the nucleotide-dependent conformational landscape of polymerase β-DNA complexes

2020 ◽  
Vol 295 (27) ◽  
pp. 9012-9020
Author(s):  
Carel Fijen ◽  
Mariam M. Mahmoud ◽  
Meike Kronenberg ◽  
Rebecca Kaup ◽  
Mattia Fontana ◽  
...  
Keyword(s):  
Dna Repair ◽  
Single Molecule ◽  
Conformational Changes ◽  
Dna Complexes ◽  
Single Molecule Fret ◽  
Nucleotide Incorporation ◽  
Eukaryotic Dna ◽  
Cellular Dna ◽  
Dna Complex ◽  
Gapped Dna

Eukaryotic DNA polymerase β (Pol β) plays an important role in cellular DNA repair, as it fills short gaps in dsDNA that result from removal of damaged bases. Since defects in DNA repair may lead to cancer and genetic instabilities, Pol β has been extensively studied, especially its mechanisms for substrate binding and a fidelity-related conformational change referred to as “fingers closing.” Here, we applied single-molecule FRET to measure distance changes associated with DNA binding and prechemistry fingers movement of human Pol β. First, using a doubly labeled DNA construct, we show that Pol β bends the gapped DNA substrate less than indicated by previously reported crystal structures. Second, using acceptor-labeled Pol β and donor-labeled DNA, we visualized dynamic fingers closing in single Pol β-DNA complexes upon addition of complementary nucleotides and derived rates of conformational changes. We further found that, while incorrect nucleotides are quickly rejected, they nonetheless stabilize the polymerase-DNA complex, suggesting that Pol β, when bound to a lesion, has a strong commitment to nucleotide incorporation and thus repair. In summary, the observation and quantification of fingers movement in human Pol β reported here provide new insights into the delicate mechanisms of prechemistry nucleotide selection.

scholarly journals Receptor-Ligand Interactions Studied with Homogeneous Fluorescence-Based Assays Suitable for Miniaturized Screening

2001 ◽  
Vol 6 (1) ◽  
pp. 11-18
Author(s):  
Andreas A. Scheel ◽  
Bettina Funsch ◽  
Michael Busch ◽  
Gabriele Gradl ◽  
Johannes Pschorr ◽  
...  
Keyword(s):  
High Throughput ◽  
Single Molecule ◽  
High Throughput Screening ◽  
Free Ligand ◽  
Membrane Vesicles ◽  
Membrane Receptors ◽  
Receptor Expression ◽  
Model Systems ◽  
Fluorescence Signal ◽  
Distribution Analysis

Cell membrane receptors play a central role in controlling cellular functions, making them the target of drugs for a wide variety of diseases. This report describes how a recently developed method, fluorescence intensity distribution analysis (FIDA), can be used to develop homogeneous, nonradioactive high throughput screening assays for membrane receptors. With FIDA, free ligand and ligand accumulated on receptor-bearing membrane vesicles can be distinguished on the basis of their particle brightness. This allows the concentration of both bound and free ligand to be determined reliably from a single measurement, without any separation. We demonstrate that ligand affinity, receptor expression level, and potency of inhibitors can be determined using the epidermal growth factor and β2-adrenergic receptors as model systems. Highly focused confocal optics enable single-molecule sensitivity, and sample volumes can thus be reduced to 1,IL without affecting the quality of the fluorescence signal. Our results demonstrate that FIDA is an ideal method for membrane receptor assays offering substantial benefits for assay development and high throughput pharmaceutical screening.

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