1
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Voorspoels A, Gevers J, Santermans S, Akkan N, Martens K, Willems K, Van Dorpe P, Verhulst AS. Design Principles of DNA-Barcodes for Nanopore-FET Readout, Based on Molecular Dynamics and TCAD Simulations. J Phys Chem A 2024. [PMID: 38712508 DOI: 10.1021/acs.jpca.4c01772] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/08/2024]
Abstract
Nanopore field-effect transistor (NP-FET) devices hold great promise as sensitive single-molecule sensors, which provide CMOS-based on-chip readout and are also highly amenable to parallelization. A plethora of applications will therefore benefit from NP-FET technology, such as large-scale molecular analysis (e.g., proteomics). Due to its potential for parallelization, the NP-FET looks particularly well-suited for the high-throughput readout of DNA-based barcodes. However, to date, no study exists that unravels the bit-rate capabilities of NP-FET devices. In this paper, we design DNA-based barcodes by labeling a piece of double-stranded DNA with dumbbell-like DNA structures. We explore the impact of both the size of the dumbbells and their spacing on achievable bit-rates. The conformational fluctuations of this DNA-origami, as observed by molecular dynamics (MD) simulation, are accounted for when selecting label sizes. An experimentally informed 3D continuum nanofluidic-nanoelectronic device model subsequently predicts both the ionic current and FET signals. We present a barcode design for a conceptually generic NP-FET, with a 14 nm diameter pore, operating in conditions corresponding to experiments. By adjusting the spacing between the labels to half the length of the pore, we show that a bit-rate of 78 kbit·s-1 is achievable. This lies well beyond the state-of-the-art of ≈40 kbit·s-1, with significant headroom for further optimizations. We also highlight the advantages of NP-FET readout based on the larger signal size and sinusoidal signal shape.
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Affiliation(s)
- Aderik Voorspoels
- Imec, Kapeldreef 75, B-3001 Leuven, Belgium
- Department of Physics and Astronomy, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven, Belgium
| | - Juliette Gevers
- Imec, Kapeldreef 75, B-3001 Leuven, Belgium
- Department of Physics and Astronomy, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven, Belgium
| | | | - Nihat Akkan
- Imec, Kapeldreef 75, B-3001 Leuven, Belgium
- Department of Physics and Astronomy, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven, Belgium
| | - Koen Martens
- Imec, Kapeldreef 75, B-3001 Leuven, Belgium
- Department of Physics and Astronomy, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven, Belgium
| | | | - Pol Van Dorpe
- Imec, Kapeldreef 75, B-3001 Leuven, Belgium
- Department of Physics and Astronomy, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven, Belgium
| | - Anne S Verhulst
- Imec, Kapeldreef 75, B-3001 Leuven, Belgium
- Department of Electrical Engineering (ESAT), KU Leuven, Kasteelpark Arenberg 10, B-3001 Leuven, Belgium
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2
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Huang G, Voorspoels A, Versloot RCA, van der Heide NJ, Carlon E, Willems K, Maglia G. PlyAB Nanopores Detect Single Amino Acid Differences in Folded Haemoglobin from Blood. Angew Chem Int Ed Engl 2022; 61:e202206227. [PMID: 35759385 PMCID: PMC9541544 DOI: 10.1002/anie.202206227] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Indexed: 01/04/2023]
Abstract
The real‐time identification of protein biomarkers is crucial for the development of point‐of‐care and portable devices. Here, we use a PlyAB biological nanopore to detect haemoglobin (Hb) variants. Adult haemoglobin (HbA) and sickle cell anaemia haemoglobin (HbS), which differ by just one amino acid, were distinguished in a mixture with more than 97 % accuracy based on individual blockades. Foetal Hb, which shows a larger sequence variation, was distinguished with near 100 % accuracy. Continuum and Brownian dynamics simulations revealed that Hb occupies two energy minima, one near the inner constriction and one at the trans entry of the nanopore. Thermal fluctuations, the charge of the protein, and the external bias influence the dynamics of Hb within the nanopore, which in turn generates the unique ionic current signal in the Hb variants. Finally, Hb was counted from blood samples, demonstrating that direct discrimination and quantification of Hb from blood using nanopores, is feasible.
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Affiliation(s)
- Gang Huang
- Groningen Biomolecular Sciences & Biotechnology Institute, University of Groningen, 9747 AG, Groningen, The Netherlands
| | - Aderik Voorspoels
- Soft Matter and Biophysics Unit, KU Leuven, Celestijnenlaan 200D, 3001, Leuven, Belgium
| | | | - Nieck Jordy van der Heide
- Groningen Biomolecular Sciences & Biotechnology Institute, University of Groningen, 9747 AG, Groningen, The Netherlands
| | - Enrico Carlon
- Soft Matter and Biophysics Unit, KU Leuven, Celestijnenlaan 200D, 3001, Leuven, Belgium
| | | | - Giovanni Maglia
- Groningen Biomolecular Sciences & Biotechnology Institute, University of Groningen, 9747 AG, Groningen, The Netherlands
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3
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Lucas FLR, Willems K, Tadema MJ, Tych KM, Maglia G, Wloka C. Unbiased Data Analysis for the Parameterization of Fast Translocation Events through Nanopores. ACS Omega 2022; 7:26040-26046. [PMID: 35936408 PMCID: PMC9352258 DOI: 10.1021/acsomega.2c00871] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Single-molecule nanopore electrophysiology is an emerging technique for the detection of analytes in aqueous solutions with high sensitivity. These detectors have proven applicable for the enzyme-assisted sequencing of oligonucleotides. There has recently been an increased interest in the use of nanopores for the fingerprinting of peptides and proteins, referred to as single-molecule nanopore spectrometry. However, the analysis of the resulting electrophysiology traces remains complicated due to the fast unassisted translocation of such analytes, usually in the order of micro- to milliseconds, and the small ion current signal produced (in the picoampere range). Here, we present the application of a generalized normal distribution function (gNDF) for the characterization of short-lived ion current signals (blockades). We show that the gNDF can be used to determine if the observed blockades have adequate time to reach their maximum current plateau while also providing a description of each blockade based on the open pore current (I O), the difference caused by the pore blockade (ΔI B), the position in time (μ), the standard deviation (σ), and a shape parameter (β), leaving only the noise component. In addition, this method allows the estimation of an ideal range of low-pass filter frequencies that contains maximum information with minimal noise. In summary, we show a parameter-free and generalized method for the analysis of short-lived ion current blockades, which facilitates single-molecule nanopore spectrometry with minimal user bias.
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Affiliation(s)
- Florian L. R. Lucas
- Groningen
Biomolecular Sciences and Biotechnology Institute, University of Groningen, 9712 CP Groningen, The Netherlands
- Lab
for Nanobiology, Department of Chemistry, KU Leuven, 3001 Leuven, Belgium
| | | | - Matthijs J. Tadema
- Groningen
Biomolecular Sciences and Biotechnology Institute, University of Groningen, 9712 CP Groningen, The Netherlands
| | - Katarzyna M. Tych
- Groningen
Biomolecular Sciences and Biotechnology Institute, University of Groningen, 9712 CP Groningen, The Netherlands
| | - Giovanni Maglia
- Groningen
Biomolecular Sciences and Biotechnology Institute, University of Groningen, 9712 CP Groningen, The Netherlands
| | - Carsten Wloka
- Groningen
Biomolecular Sciences and Biotechnology Institute, University of Groningen, 9712 CP Groningen, The Netherlands
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4
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Huang G, Voorspoels A, Versloot RCA, Van Der Heide NJ, Carlon E, Willems K, Maglia G. PlyAB Nanopores Detect Single Amino Acid Differences in Folded Haemoglobin from Blood. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202206227] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Gang Huang
- University of Groningen: Rijksuniversiteit Groningen Chemical Biology NETHERLANDS
| | - Aderik Voorspoels
- KU Leuven: Katholieke Universiteit Leuven Soft Matter and Biophysics BELGIUM
| | | | | | - Enrico Carlon
- KU Leuven University: Katholieke Universiteit Leuven Soft Matter and Biophysics NETHERLANDS
| | - Kherim Willems
- Imec Integrated photonics for microscopy and biomedical imaging BELGIUM
| | - Giovanni Maglia
- Rijksuniversiteit Groningen Chemical Biology Nijenborgh 7 9747 AG Groningen NETHERLANDS
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5
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Hoyer M, Crevenna AH, Kitel R, Willems K, Czub M, Dubin G, Van Dorpe P, Holak TA, Lamb DC. Analysis tools for single-monomer measurements of self-assembly processes. Sci Rep 2022; 12:4682. [PMID: 35304498 PMCID: PMC8933434 DOI: 10.1038/s41598-022-08245-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2021] [Accepted: 02/22/2022] [Indexed: 11/29/2022] Open
Abstract
Protein assembly plays an important role throughout all phyla of life, both physiologically and pathologically. In particular, aggregation and polymerization of proteins are key-strategies that regulate cellular function. In recent years, methods to experimentally study the assembly process on a single-molecule level have been developed. This progress concomitantly has triggered the question of how to analyze this type of single-filament data adequately and what experimental conditions are necessary to allow a meaningful interpretation of the analysis. Here, we developed two analysis methods for single-filament data: the visitation analysis and the average-rate analysis. We benchmarked and compared both approaches with the classic dwell-time-analysis frequently used to study microscopic association and dissociation rates. In particular, we tested the limitations of each analysis method along the lines of the signal-to-noise ratio, the sampling rate, and the labeling efficiency and bleaching rate of the fluorescent dyes used in single-molecule fluorescence experiments. Finally, we applied our newly developed methods to study the monomer assembly of actin at the single-molecule-level in the presence of the class II nucleator Cappuccino and the WH2 repeats of Spire. For Cappuccino, our data indicated fast elongation circumventing a nucleation phase whereas, for Spire, we found that the four WH2 motifs are not sufficient to promote de novo nucleation of actin.
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Affiliation(s)
- Maria Hoyer
- Department of Chemistry, Center for NanoScience, Nanosystems Initiative Munich (NIM) and Center for Integrated Protein Science Munich (CiPSM), Ludwig-Maximilians University Munich, Munich, Germany
| | - Alvaro H Crevenna
- Department of Chemistry, Center for NanoScience, Nanosystems Initiative Munich (NIM) and Center for Integrated Protein Science Munich (CiPSM), Ludwig-Maximilians University Munich, Munich, Germany.,Epigenetics and Neurobiology Unit, EMBL Rome, Monterotondo, Italy
| | - Radoslaw Kitel
- Department of Organic Chemistry, Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, 30-387, Krakow, Poland.,Malopolska Centre of Biotechnology, Jagiellonian University, Gronostajowa 7a, 30-387, Krakow, Poland
| | | | - Miroslawa Czub
- Department of Organic Chemistry, Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, 30-387, Krakow, Poland
| | - Grzegorz Dubin
- Malopolska Centre of Biotechnology, Jagiellonian University, Gronostajowa 7a, 30-387, Krakow, Poland
| | | | - Tad A Holak
- Department of Organic Chemistry, Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, 30-387, Krakow, Poland
| | - Don C Lamb
- Department of Chemistry, Center for NanoScience, Nanosystems Initiative Munich (NIM) and Center for Integrated Protein Science Munich (CiPSM), Ludwig-Maximilians University Munich, Munich, Germany.
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6
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Bayoumi M, Nomidis SK, Willems K, Carlon E, Maglia G. Autonomous and Active Transport Operated by an Entropic DNA Piston. Nano Lett 2021; 21:762-768. [PMID: 33342212 PMCID: PMC7809690 DOI: 10.1021/acs.nanolett.0c04464] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
We present a synthetic nanoscale piston that uses chemical energy to perform molecular transport against an applied bias. Such a device comprises a 13 by 5 nm protein cylinder, embedded in a biological membrane enclosing a single-stranded DNA (ssDNA) rod. Hybridization with DNA cargo rigidifies the rod, allowing for transport of a selected DNA molecule across the nanopore. A strand displacement reaction from ssDNA fuel on the other side of the membrane then liberates the DNA cargo back into solution and regenerates the initial configuration. The entropic penalty of ssDNA confinement inside the nanopore drives DNA transport regardless of the applied bias. Multiple automated and reciprocating cycles are observed, in which the DNA piston moves through the 10 nm length of the nanopore. In every cycle, a single DNA molecule is transported across the nanopore against an external bias force, which is the hallmark of biological transporters.
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Affiliation(s)
- Mariam Bayoumi
- Department
of Chemistry, KU Leuven, Celestijnenlaan 200G, Leuven 3001, Belgium
- Center for
Brain & Disease Research, VIB-KU Leuven, Leuven 3000, Belgium
| | - Stefanos K. Nomidis
- Flemish
Institute for Technological Research (VITO), Boeretang 200, Mol B-2400, Belgium
- KU Leuven, Soft Matter and Biophysics Unit,
Department of Physics
and Astronomy, Celestijnenlaan
200D, 3001 Leuven, Belgium
| | | | - Enrico Carlon
- KU Leuven, Soft Matter and Biophysics Unit,
Department of Physics
and Astronomy, Celestijnenlaan
200D, 3001 Leuven, Belgium
| | - Giovanni Maglia
- Groningen
Biomolecular Sciences & Biotechnology Institute, University of Groningen, Groningen 9747 AG , The Netherlands
- Department
of Chemistry, KU Leuven, Celestijnenlaan 200G, Leuven 3001, Belgium
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7
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Willems K, Ruić D, L R Lucas F, Barman U, Verellen N, Hofkens J, Maglia G, Van Dorpe P. Accurate modeling of a biological nanopore with an extended continuum framework. Nanoscale 2020; 12:16775-16795. [PMID: 32780087 DOI: 10.1039/d0nr03114c] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Despite the broad success of biological nanopores as powerful instruments for the analysis of proteins and nucleic acids at the single-molecule level, a fast simulation methodology to accurately model their nanofluidic properties is currently unavailable. This limits the rational engineering of nanopore traits and makes the unambiguous interpretation of experimental results challenging. Here, we present a continuum approach that can faithfully reproduce the experimentally measured ionic conductance of the biological nanopore Cytolysin A (ClyA) over a wide range of ionic strengths and bias potentials. Our model consists of the extended Poisson-Nernst-Planck and Navier-Stokes (ePNP-NS) equations and a computationally efficient 2D-axisymmetric representation for the geometry and charge distribution of the nanopore. Importantly, the ePNP-NS equations achieve this accuracy by self-consistently considering the finite size of the ions and the influence of both the ionic strength and the nanoscopic scale of the pore on the local properties of the electrolyte. These comprise the mobility and diffusivity of the ions, and the density, viscosity and relative permittivity of the solvent. Crucially, by applying our methodology to ClyA, a biological nanopore used for single-molecule enzymology studies, we could directly quantify several nanofluidic characteristics difficult to determine experimentally. These include the ion selectivity, the ion concentration distributions, the electrostatic potential landscape, the magnitude of the electro-osmotic flow field, and the internal pressure distribution. Hence, this work provides a means to obtain fundamental new insights into the nanofluidic properties of biological nanopores and paves the way towards their rational engineering.
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Affiliation(s)
- Kherim Willems
- KU Leuven, Department of Chemistry, Celestijnenlaan 200F, B-3001 Leuven, Belgium
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8
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Huang G, Willems K, Bartelds M, van Dorpe P, Soskine M, Maglia G. Electro-Osmotic Vortices Promote the Capture of Folded Proteins by PlyAB Nanopores. Nano Lett 2020; 20:3819-3827. [PMID: 32271587 PMCID: PMC7227020 DOI: 10.1021/acs.nanolett.0c00877] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2020] [Revised: 04/06/2020] [Indexed: 05/19/2023]
Abstract
Biological nanopores are emerging as powerful tools for single-molecule analysis and sequencing. Here, we engineered the two-component pleurotolysin (PlyAB) toxin to assemble into 7.2 × 10.5 nm cylindrical nanopores with a low level of electrical noise in lipid bilayers, and we addressed the nanofluidic properties of the nanopore by continuum simulations. Surprisingly, proteins such as human albumin (66.5 kDa) and human transferrin (76-81 kDa) did not enter the nanopore. We found that the precise engineering of the inner surface charge of the PlyAB induced electro-osmotic vortices that allowed the electrophoretic capture of the proteins. Once inside the nanopore, two human plasma proteins could be distinguished by the characteristics of their current blockades. This fundamental understanding of the nanofluidic properties of nanopores provides a practical method to promote the capture and analysis of folded proteins by nanopores.
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Affiliation(s)
- Gang Huang
- Groningen
Biomolecular Sciences & Biotechnology Institute, University of Groningen, 9747 AG Groningen, The Netherlands
| | - Kherim Willems
- Department
of Chemistry, KU Leuven, Celestijnenlaan 200G, 3001 Leuven, Belgium
- imec, Kapeldreef 75, 3001 Leuven, Belgium
| | - Mart Bartelds
- Groningen
Biomolecular Sciences & Biotechnology Institute, University of Groningen, 9747 AG Groningen, The Netherlands
| | - Pol van Dorpe
- imec, Kapeldreef 75, 3001 Leuven, Belgium
- Department
of Physics and Astronomy, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium
| | - Misha Soskine
- Groningen
Biomolecular Sciences & Biotechnology Institute, University of Groningen, 9747 AG Groningen, The Netherlands
| | - Giovanni Maglia
- Groningen
Biomolecular Sciences & Biotechnology Institute, University of Groningen, 9747 AG Groningen, The Netherlands
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9
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Willems K, Ruić D, Biesemans A, Galenkamp N, Van Dorpe P, Maglia G. Electrophoretic Trapping of a Single Protein Inside a Nanopore. Biophys J 2020. [DOI: 10.1016/j.bpj.2019.11.1723] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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10
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Lasat E, Willems K, Huysmans S. [Autistic female with anxiety disorder and superior mesenteric artery syndrome]. Tijdschr Psychiatr 2020; 62:805-809. [PMID: 32910453] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
An anxiety disorder can manifest in multiple ways. We saw a 21-year-old woman with an anxiety disorder in combination with superior mesenteric artery syndrome. For we know, this is the first description of this combination. There was also hypersensitivity to certain foods and rigid thinking patterns, and an autism spectrum disorder was discovered later. The recognition of the influence of autism on comorbid disorders is important in order to create an individual adapted treatment protocol.
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11
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Willems K, Ruić D, Biesemans A, Galenkamp NS, Van Dorpe P, Maglia G. Engineering and Modeling the Electrophoretic Trapping of a Single Protein Inside a Nanopore. ACS Nano 2019; 13:9980-9992. [PMID: 31403770 PMCID: PMC6764111 DOI: 10.1021/acsnano.8b09137] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
The ability to confine and to study single molecules has enabled important advances in natural and applied sciences. Recently, we have shown that unlabeled proteins can be confined inside the biological nanopore Cytolysin A (ClyA) and conformational changes monitored by ionic current recordings. However, trapping small proteins remains a challenge. Here, we describe a system where steric, electrostatic, electrophoretic, and electro-osmotic forces are exploited to immobilize a small protein, dihydrofolate reductase (DHFR), inside ClyA. Assisted by electrostatic simulations, we show that the dwell time of DHFR inside ClyA can be increased by orders of magnitude (from milliseconds to seconds) by manipulation of the DHFR charge distribution. Further, we describe a physical model that includes a double energy barrier and the main electrophoretic components for trapping DHFR inside the nanopore. Simultaneous fits to the voltage dependence of the dwell times allowed direct estimates of the cis and trans translocation probabilities, the mean dwell time, and the force exerted by the electro-osmotic flow on the protein (≅9 pN at -50 mV) to be retrieved. The observed binding of NADPH to the trapped DHFR molecules suggested that the engineered proteins remained folded and functional inside ClyA. Contact-free confinement of single proteins inside nanopores can be employed for the manipulation and localized delivery of individual proteins and will have further applications in single-molecule analyte sensing and enzymology studies.
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Affiliation(s)
- Kherim Willems
- Department
of Chemistry, KU Leuven, Celestijnenlaan 200F, B-3001 Leuven, Belgium
- imec, Kapeldreef 75, B-3001 Leuven, Belgium
| | - Dino Ruić
- imec, Kapeldreef 75, B-3001 Leuven, Belgium
- Department
of Physics and Astronomy, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven, Belgium
| | - Annemie Biesemans
- Department
of Chemistry, KU Leuven, Celestijnenlaan 200F, B-3001 Leuven, Belgium
| | - Nicole Stéphanie Galenkamp
- Groningen
Biomolecular Sciences & Biotechnology Institute, University of Groningen, 9747 AG Groningen, The Netherlands
| | - Pol Van Dorpe
- imec, Kapeldreef 75, B-3001 Leuven, Belgium
- Department
of Physics and Astronomy, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven, Belgium
| | - Giovanni Maglia
- Groningen
Biomolecular Sciences & Biotechnology Institute, University of Groningen, 9747 AG Groningen, The Netherlands
- E-mail:
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12
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Abstract
Biological nanopores are a class of membrane proteins that open nanoscale water conduits in biological membranes. When they are reconstituted in artificial membranes and a bias voltage is applied across the membrane, the ionic current passing through individual nanopores can be used to monitor chemical reactions, to recognize individual molecules and, of most interest, to sequence DNA. In addition, a more recent nanopore application is the analysis of single proteins and enzymes. Monitoring enzymatic reactions with nanopores, i.e. nanopore enzymology, has the unique advantage that it allows long-timescale observations of native proteins at the single-molecule level. Here, we describe the approaches and challenges in nanopore enzymology.This article is part of the themed issue 'Membrane pores: from structure and assembly, to medicine and technology'.
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Affiliation(s)
- Kherim Willems
- Department of Chemistry, KU Leuven, Celestijnenlaan 200G, 3001 Leuven, Belgium.,Department of Life Sciences and Imaging, IMEC, Kapeldreef 75, 3001 Leuven, Belgium
| | - Veerle Van Meervelt
- Department of Chemistry, KU Leuven, Celestijnenlaan 200G, 3001 Leuven, Belgium.,Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - Carsten Wloka
- Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - Giovanni Maglia
- Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
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13
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Huang G, Willems K, Soskine M, Wloka C, Maglia G. Electro-osmotic capture and ionic discrimination of peptide and protein biomarkers with FraC nanopores. Nat Commun 2017; 8:935. [PMID: 29038539 PMCID: PMC5715100 DOI: 10.1038/s41467-017-01006-4] [Citation(s) in RCA: 153] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2017] [Accepted: 08/09/2017] [Indexed: 12/13/2022] Open
Abstract
Biological nanopores are nanoscale sensors employed for high-throughput, low-cost, and long read-length DNA sequencing applications. The analysis and sequencing of proteins, however, is complicated by their folded structure and non-uniform charge. Here we show that an electro-osmotic flow through Fragaceatoxin C (FraC) nanopores can be engineered to allow the entry of polypeptides at a fixed potential regardless of the charge composition of the polypeptide. We further use the nanopore currents to discriminate peptide and protein biomarkers from 25 kDa down to 1.2 kDa including polypeptides differing by one amino acid. On the road to nanopore proteomics, our findings represent a rationale for amino-acid analysis of folded and unfolded polypeptides with nanopores. Biological nanopore–based protein sequencing and recognition is challenging due to the folded structure or non-uniform charge of peptides. Here the authors show that engineered FraC nanopores can overcome these problems and recognize biomarkers in the form of oligopeptides, polypeptides and folded proteins.
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Affiliation(s)
- Gang Huang
- Groningen Biomolecular Sciences & Biotechnology Institute, University of Groningen, 9747 AG, Groningen, The Netherlands
| | - Kherim Willems
- KU Leuven Department of Chemistry, Celestijnenlaan 200G, 3001, Leuven, Belgium.,Imec, Kapeldreef 75, 3001, Leuven, Belgium
| | - Misha Soskine
- Groningen Biomolecular Sciences & Biotechnology Institute, University of Groningen, 9747 AG, Groningen, The Netherlands
| | - Carsten Wloka
- Groningen Biomolecular Sciences & Biotechnology Institute, University of Groningen, 9747 AG, Groningen, The Netherlands.
| | - Giovanni Maglia
- Groningen Biomolecular Sciences & Biotechnology Institute, University of Groningen, 9747 AG, Groningen, The Netherlands.
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14
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Kokkinos P, Kozyra I, Lazic S, Söderberg K, Vasickova P, Bouwknegt M, Rutjes S, Willems K, Moloney R, de Roda Husman AM, Kaupke A, Legaki E, D'Agostino M, Cook N, von Bonsdorff CH, Rzeżutka A, Petrovic T, Maunula L, Pavlik I, Vantarakis A. Virological Quality of Irrigation Water in Leafy Green Vegetables and Berry Fruits Production Chains. Food Environ Virol 2017; 9:72-78. [PMID: 27709435 DOI: 10.1007/s12560-016-9264-2] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Accepted: 09/28/2016] [Indexed: 05/21/2023]
Abstract
This study condenses data acquired during investigations of the virological quality of irrigation water used in production of fresh produce. One hundred and eight samples of irrigation water were collected from five berry fruit farms in Finland (1), the Czech Republic (1), Serbia (2), and Poland (1), and sixty-one samples were collected from three leafy green vegetable farms in Poland, Serbia, and Greece. Samples were analyzed for index viruses of human or animal fecal contamination (human and porcine adenoviruses, and bovine polyoma viruses), and human pathogenic viruses (hepatitis A virus, hepatitis E virus, and noroviruses GI/GII). Both index and pathogenic viruses were found in irrigation water samples from the leafy green vegetables production chain. The data on the presence of index viruses indicated that the highest percentage of fecal contamination was of human origin (28.1 %, 18/64), followed by that of porcine (15.4 %, 6/39) and bovine (5.1 %, 2/39) origins. Hepatitis E virus (5 %, 1/20) and noroviruses GII (14.3 %, 4/28) were also detected. Samples from berry fruit production were also positive for both index and pathogenic viruses. The highest percentage of fecal contamination was of human origin (8.3 %, 9/108), followed by that of porcine, 4.5 % (4/89) and bovine, 1.1 % (1/89) origins. Norovirus GII (3.6 %, 2/56) was also detected. These data demonstrate that irrigation water used in primary production is an important vehicle of viral contamination for fresh produce, and thus is a critical control point which should be integrated into food safety management systems for viruses. The recommendations of Codex Alimentarius, as well as regulations on the use of water of appropriate quality for irrigation purposes, should be followed.
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Affiliation(s)
- P Kokkinos
- Environmental Microbiology Unit, Department of Public Health, University of Patras, University Campus, 26500, Patras, Greece
| | - I Kozyra
- National Veterinary Research Institute, Al. Partyzantów 57, 24-100, Puławy, Poland
| | - S Lazic
- Scientific Veterinary Institute "Novi Sad", Rumenacki put 20, 21000, Novi Sad, Serbia
| | - K Söderberg
- Department of Food Hygiene and Environmental Health, Faculty of Veterinary Medicine, University of Helsinki, P.O. Box 66, 00014, Helsinki, Finland
| | - P Vasickova
- Veterinary Research Institute, Hudcova 70, 721 00, Brno, Czech Republic
| | - M Bouwknegt
- National Institute for Public Health and the Environment, RIVM, Utrecht, The Netherlands
| | - S Rutjes
- National Institute for Public Health and the Environment, RIVM, Utrecht, The Netherlands
| | - K Willems
- Laboratory for Process Microbial Ecology and Bioinspirational Management, Consortium for Industrial Microbiology and Biotechnology, Department of Microbial and Molecular Systems, KU Leuven, Leuven, Belgium
- Scientia Terrae Research Institute, Sint-Katelijne-Waver, Belgium
| | - R Moloney
- Environmental Health Service, Health Service Executive, Sandfield Centre, Ennis, Co., Clare, Ireland
| | - A M de Roda Husman
- National Institute for Public Health and the Environment, RIVM, Utrecht, The Netherlands
| | - A Kaupke
- National Veterinary Research Institute, Al. Partyzantów 57, 24-100, Puławy, Poland
| | - E Legaki
- Environmental Microbiology Unit, Department of Public Health, University of Patras, University Campus, 26500, Patras, Greece
| | - M D'Agostino
- Food and Environment Research Agency (FERA), Sand Hutton, York, UK
| | - N Cook
- Food and Environment Research Agency (FERA), Sand Hutton, York, UK
| | - C-H von Bonsdorff
- Department of Food Hygiene and Environmental Health, Faculty of Veterinary Medicine, University of Helsinki, P.O. Box 66, 00014, Helsinki, Finland
| | - A Rzeżutka
- National Veterinary Research Institute, Al. Partyzantów 57, 24-100, Puławy, Poland.
| | - T Petrovic
- Scientific Veterinary Institute "Novi Sad", Rumenacki put 20, 21000, Novi Sad, Serbia.
| | - L Maunula
- Department of Food Hygiene and Environmental Health, Faculty of Veterinary Medicine, University of Helsinki, P.O. Box 66, 00014, Helsinki, Finland.
| | - I Pavlik
- Veterinary Research Institute, Hudcova 70, 721 00, Brno, Czech Republic.
| | - A Vantarakis
- Environmental Microbiology Unit, Department of Public Health, University of Patras, University Campus, 26500, Patras, Greece.
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Abstract
This study examined the prevalence of appointment noncompliance in 101 heart transplant recipients and how appointment noncompliance is related to patient profile and clinical risk. Appointment noncompliance was defined as patients not showing up at 1 or more planned clinic appointments (at a minimal frequency of every 3 months) during the previous year. Clinical variables were collected from medical files. Psychosocial variables were measured using established instruments. Medication noncompliance was assessed using electronic event monitoring. Paired t test, Wilcoxon 2-sample test, chi-square test, or Fisher exact test were used for statistical analysis as appropriate. The prevalence of appointment noncompliance was 7%. Appointment noncompliers were significantly younger, were less likely to live in a stable relationship with a partner, were more depressed, perceived their health as poorer, experienced more symptom distress, and had significantly more drug holidays. Fifty-seven percent of the appointment noncompliers experienced 1 or more late acute rejection episodes, compared to 2% of the appointment compliers. Appointment noncompliance is a critical behavioral risk factor in the occurrence of late acute rejection episodes in heart transplant patients. Patient profiles allow the identification of patients at risk for appointment noncompliance.
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Affiliation(s)
- S De Geest
- Center for Health Services and Nursing Research, Catholic University Leuven, Belgium
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16
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Franceschini L, Brouns T, Willems K, Carlon E, Maglia G. DNA Translocation through Nanopores at Physiological Ionic Strengths Requires Precise Nanoscale Engineering. ACS Nano 2016; 10:8394-402. [PMID: 27513592 PMCID: PMC5221729 DOI: 10.1021/acsnano.6b03159] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Many important processes in biology involve the translocation of a biopolymer through a nanometer-scale pore. Moreover, the electrophoretic transport of DNA across nanopores is under intense investigation for single-molecule DNA sequencing and analysis. Here, we show that the precise patterning of the ClyA biological nanopore with positive charges is crucial to observe the electrophoretic translocation of DNA at physiological ionic strength. Surprisingly, the strongly electronegative 3.3 nm internal constriction of the nanopore did not require modifications. Further, DNA translocation could only be observed from the wide entry of the nanopore. Our results suggest that the engineered positive charges are important to align the DNA in order to overcome the entropic and electrostatic barriers for DNA translocation through the narrow constriction. Finally, the dependencies of nucleic acid translocations on the Debye length of the solution are consistent with a physical model where the capture of double-stranded DNA is diffusion-limited while the capture of single-stranded DNA is reaction-limited.
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17
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Li Y, Chen C, Willems K, Lagae L, Groeseneken G, Stakenborg T, Van Dorpe P. Asymmetric plasmonic induced ionic noise in metallic nanopores. Nanoscale 2016; 8:12324-12329. [PMID: 27273622 DOI: 10.1039/c6nr01837h] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We present distinct asymmetric plasmon-induced noise properties of ionic transport observed through gold coated nanopores. We thoroughly investigated the effects of bias voltage and laser illumination. We show that the potential drop across top-coated silicon nanocavity pores can give rise to a large noise asymmetry (∼2-3 orders of magnitude). Varying the bias voltage has an appreciable effect on the noise density spectra, typically in the Lorentzian components. The laser power is found to strongly affect the ionic noise level as well as the voltage threshold for light-induced noise generation. The asymmetric noise phenomenon is attributed to plasmon-induced interfacial reactions which promote light-induced charge fluctuation in the ion flow and allow voltage modulation of photo-induced carriers surmounting over such Schottky junctions. We further compare the ionic noise performances of gold nanocavities containing different material stacks, among which thermal oxide passivation of the silicon successfully mitigates the light-induced noise and is also fully CMOS-compatible. The understanding of the described noise characteristics will help to foster multiple applications using related structures including plasmonic-based sensing or plasmon-induced catalysis such as water splitting or solar energy conversion devices.
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Affiliation(s)
- Yi Li
- IMEC, Kapeldreef 75, Leuven, B3001, Belgium. and Department of Electrical Engineering, KU Leuven, Kasteelpark Arenberg 10, 3001 Leuven, Belgium
| | - Chang Chen
- IMEC, Kapeldreef 75, Leuven, B3001, Belgium. and Department of Physics and Astronomy, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium
| | - Kherim Willems
- IMEC, Kapeldreef 75, Leuven, B3001, Belgium. and Department of Chemistry, KU Leuven, Celestijnenlaan 200G, 3001 Leuven, Belgium
| | - Liesbet Lagae
- IMEC, Kapeldreef 75, Leuven, B3001, Belgium. and Department of Physics and Astronomy, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium
| | - Guido Groeseneken
- IMEC, Kapeldreef 75, Leuven, B3001, Belgium. and Department of Electrical Engineering, KU Leuven, Kasteelpark Arenberg 10, 3001 Leuven, Belgium
| | | | - Pol Van Dorpe
- IMEC, Kapeldreef 75, Leuven, B3001, Belgium. and Department of Physics and Astronomy, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium
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18
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Busschaert P, Frans I, Crauwels S, Zhu B, Willems K, Bossier P, Michiels C, Verstrepen K, Lievens B, Rediers H. Comparative genome sequencing to assess the genetic diversity and virulence attributes of 15 Vibrio anguillarum isolates. J Fish Dis 2015; 38:795-807. [PMID: 25073650 DOI: 10.1111/jfd.12290] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2014] [Revised: 06/14/2014] [Accepted: 06/19/2014] [Indexed: 06/03/2023]
Abstract
Vibrio anguillarum is the causative agent of vibriosis, a deadly haemorrhagic septicaemic disease affecting various marine and fresh/brackish water fish, bivalves and crustaceans. However, the diversity and virulence mechanisms of this pathogen are still insufficiently known. In this study, we aimed to increase our understanding of V. anguillarum diversity and virulence through comparative genome analysis of 15 V. anguillarum strains, obtained from different hosts or non-host niches and geographical regions, among which 10 and 5 strains were found to be virulent and avirulent, respectively, against sea bass larvae. First, the 15 draft genomes were annotated and screened for putative virulence factors, including genes encoding iron uptake systems, transport systems and non-ribosomal peptide synthetases. Second, comparative genome analysis was performed, focusing on single nucleotide polymorphisms (SNPs) and small insertions and deletions (InDels). Five V. anguillarum strains showed a remarkably high nucleotide identity. However, these strains comprise both virulent and avirulent strains towards sea bass larvae, suggesting that differences in virulence may be caused by subtle nucleotide variations. Clearly, the draft genome sequence of these 15 strains represents a starting point for further genetic research of this economically important fish pathogen.
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Affiliation(s)
- P Busschaert
- Laboratory for Process Microbial Ecology and Bioinspirational Management, Cluster for Bioengineering Technology (CBeT), Department of Microbial and Molecular Systems (M2S), KU Leuven - Campus De Nayer, Sint-Katelijne-Waver, Belgium
| | - I Frans
- Laboratory for Process Microbial Ecology and Bioinspirational Management, Cluster for Bioengineering Technology (CBeT), Department of Microbial and Molecular Systems (M2S), KU Leuven - Campus De Nayer, Sint-Katelijne-Waver, Belgium
| | - S Crauwels
- Laboratory for Process Microbial Ecology and Bioinspirational Management, Cluster for Bioengineering Technology (CBeT), Department of Microbial and Molecular Systems (M2S), KU Leuven - Campus De Nayer, Sint-Katelijne-Waver, Belgium
| | - B Zhu
- VIB Lab for Systems Biology & Centre of Microbial and Plant Genetics (CMPG), Lab for Genetics and Genomics, M2S, KU Leuven, Leuven, Belgium
| | - K Willems
- Laboratory for Process Microbial Ecology and Bioinspirational Management, Cluster for Bioengineering Technology (CBeT), Department of Microbial and Molecular Systems (M2S), KU Leuven - Campus De Nayer, Sint-Katelijne-Waver, Belgium
| | - P Bossier
- Laboratory of Aquaculture & Artemia Reference Centre, Department of Animal Production, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
| | - C Michiels
- Centre for Food and Microbial Technology, M2S, KU Leuven, Leuven, Belgium
| | - K Verstrepen
- VIB Lab for Systems Biology & Centre of Microbial and Plant Genetics (CMPG), Lab for Genetics and Genomics, M2S, KU Leuven, Leuven, Belgium
| | - B Lievens
- Laboratory for Process Microbial Ecology and Bioinspirational Management, Cluster for Bioengineering Technology (CBeT), Department of Microbial and Molecular Systems (M2S), KU Leuven - Campus De Nayer, Sint-Katelijne-Waver, Belgium
| | - H Rediers
- Laboratory for Process Microbial Ecology and Bioinspirational Management, Cluster for Bioengineering Technology (CBeT), Department of Microbial and Molecular Systems (M2S), KU Leuven - Campus De Nayer, Sint-Katelijne-Waver, Belgium
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19
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Kokkinos P, Bouwknegt M, Verhaelen K, Willems K, Moloney R, de Roda Husman A, D'Agostino M, Cook N, Vantarakis A. Virological fit-for-purpose risk assessment in a leafy green production enterprise. Food Control 2015. [DOI: 10.1016/j.foodcont.2014.11.041] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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20
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Kokkinos P, Kozyra I, Lazic S, Bouwknegt M, Rutjes S, Willems K, Moloney R, de Roda Husman AM, Kaupke A, Legaki E, D'Agostino M, Cook N, Rzeżutka A, Petrovic T, Vantarakis A. Harmonised investigation of the occurrence of human enteric viruses in the leafy green vegetable supply chain in three European countries. Food Environ Virol 2012; 4:179-191. [PMID: 23412890 DOI: 10.1007/s12560-012-9087-8] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2012] [Accepted: 08/31/2012] [Indexed: 06/01/2023]
Abstract
Numerous outbreaks have been attributed to the consumption of raw or minimally processed leafy green vegetables contaminated with enteric viral pathogens. The aim of the present study was an integrated virological monitoring of the salad vegetables supply chain in Europe, from production, processing and point-of-sale. Samples were collected and analysed in Greece, Serbia and Poland, from 'general' and 'ad hoc' sampling points, which were perceived as critical points for virus contamination. General sampling points were identified through the analysis of background information questionnaires based on HACCP audit principles, and they were sampled during each sampling occasion where as-ad hoc sampling points were identified during food safety fact-finding visits and samples were only collected during the fact-finding visits. Human (hAdV) and porcine (pAdV) adenovirus, hepatitis A (HAV) and E (HEV) virus, norovirus GI and GII (NoV) and bovine polyomavirus (bPyV) were detected by means of real-time (RT-) PCR-based protocols. General samples were positive for hAdV, pAdV, HAV, HEV, NoV GI, NoV GII and bPyV at 20.09 % (134/667), 5.53 % (13/235), 1.32 % (4/304), 3.42 % (5/146), 2 % (6/299), 2.95 % (8/271) and 0.82 % (2/245), respectively. Ad hoc samples were positive for hAdV, pAdV, bPyV and NoV GI at 9 % (3/33), 9 % (2/22), 4.54 % (1/22) and 7.14 % (1/14), respectively. These results demonstrate the existence of viral contamination routes from human and animal sources to the salad vegetable supply chain and more specifically indicate the potential for public health risks due to the virus contamination of leafy green vegetables at primary production.
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Affiliation(s)
- P Kokkinos
- Environmental Microbiology Unit, Department of Public Health, Medical School, University of Patras, 26500, Patras, Greece.
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21
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Coene E, Willems K, Verbiest L, Wagner U, Schlebusch H, DePotter C. Expression patterns and functional activity of the human 14C5 cell substrate adhesion molecule. Eur J Cancer 1997. [DOI: 10.1016/s0959-8049(97)89443-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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22
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Coene E, Van Oostveldt P, Willems K, van Emmelo J, De Potter CR. BRCA1 is localized in cytoplasmic tube-like invaginations in the nucleus. Nat Genet 1997; 16:122-4. [PMID: 9171821 DOI: 10.1038/ng0697-122] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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23
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Peeters MC, Willems K, Swennen R. Protoplast-to-plant regeneration in cotton (Gossypium hirsutum L. cv. Coker 312) using feeder layers. Plant Cell Rep 1994; 13:208-211. [PMID: 24193653 DOI: 10.1007/bf00239894] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/1993] [Revised: 09/06/1993] [Indexed: 06/02/2023]
Abstract
We report the regeneration of protoplasts isolated from two embryogenic cell lines of Gossypium hirsutum L. cv. Coker 312 initiated from hypocotylderived callus. Protoplasts plated on cellulose nitrate filters and placed over feeder layers formed embryogenic callus from which plants were regenerated. Plating efficiency up to 12.8% depended upon the cell line. Addition of phytohormones to the protoplast medium had no stimulating effect on plating efficiency. The influence of feeder cells and conditioned medium on plating efficiency was significantly different for the two cell lines.
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Affiliation(s)
- M C Peeters
- Laboratory of Tropical Crop Husbandry, Catholic University of Leuven, Kardinaal Mercierlaan 92, B-3001, Heverlee, Belgium
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24
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Abstract
To evaluate the prevalence of antibodies to Chlamydia pneumoniae in a healthy adult Belgian population a study group of 150 medical students was chosen. Sera were collected in the period between March and October 1990 and assessed by the microimmunofluorescence test. Sixty-one per cent were found to have IgG antibodies to C. pneumoniae in a titre greater than or equal to 16, which showed evidence of past infection. Twenty-one per cent had IgA in a titre greater than or equal to 8. In none were antibodies of the IgM fraction detected. The same sera were tested for the presence of antibodies to Chlamydia trachomatis. One hundred and thirty-one sera with no or low titres of antibodies to C. pneumoniae tended to have low or no detectable antibodies to C. trachomatis. Nineteen sera with high (greater than 128) titres of antibodies to C. pneumoniae had IgG antibodies in a titre of greater than or equal to 32 to C. trachomatis. This prevalence (13%) is much higher than one would expect in a population at low risk for C. trachomatis infection. The problem of possible cross-reactions between the three species in the micro-immunofluorescence test is discussed.
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Affiliation(s)
- A M Van den Abeele
- Bacteriology and Virology Laboratory, University Hospital, Ghent, Belgium
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