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Sökning: WFRF:(Tegenfeldt Fredrik)

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1.
  • Alizadehheidari, Mohammadreza, 1987, et al. (författare)
  • Nanoconfined Circular and Linear DNA: Equilibrium Conformations and Unfolding Kinetics
  • 2015
  • Ingår i: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 48:3, s. 871-878
  • Tidskriftsartikel (refereegranskat)abstract
    • Studies of circular DNA confined to nanofluidic channels are relevant both from a fundamental polymer-physics perspective and due to the importance of circular DNA molecules in vivo. We here observe the unfolding of confined DNA from the circular to linear configuration as a light-induced double-strand break occurs, characterize the dynamics, and compare the equilibrium conformational statistics of linear and circular configurations. This is important because it allows us to determine to what extent existing statistical theories describe the extension of confined circular DNA. We find that the ratio of the extensions of confined linear and circular DNA configurations increases as the buffer concentration decreases. The experimental results fall between theoretical predictions for the extended de Gennes regime at weaker confinement and the Odijk regime at stronger confinement. We show that it is possible to directly distinguish between circular and linear DNA molecules by measuring the emission intensity from the DNA. Finally, we determine the rate of unfolding and show that this rate is larger for more confined DNA, possibly reflecting the corresponding larger difference in entropy between the circular and linear configurations.
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2.
  • Alizadehheidari, Mohammadreza, et al. (författare)
  • Nanoconfined Circular DNA
  • 2014
  • Ingår i: Biophysical Journal. - : Elsevier BV. - 0006-3495 .- 1542-0086. ; 106:2, s. 274A-274A
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • Nanofluidic channels have become a versatile tool to manipulate single DNA molecules. They allow investigation of confined single DNA molecules from a fundamental polymer physics perspective as well as for example in DNA barcoding techniques.
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3.
  • Alizadehheidari, Mohammadreza, 1987, et al. (författare)
  • Unfolding of nanoconfined circular DNA
  • 2015
  • Ingår i: BIOPHYSICAL JOURNAL. - : Elsevier BV. - 0006-3495 .- 1542-0086. ; 108:2 Supplement 1, s. 231A-231A
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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4.
  • Fritzsche, Joachim, 1977, et al. (författare)
  • A lipid-based passivation scheme for nanofluidics
  • 2012
  • Ingår i: 16th International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2012; Okinawa; Japan; 28 October 2012 through 1 November 2012. - 9780979806452 ; , s. 1876-1878
  • Konferensbidrag (refereegranskat)abstract
    • Stretching DNA in nanochannels allows for direct, visual studies of genomic DNA at the single molecule level. In order to facilitate the study of the interaction of linear DNA with proteins in nanochannels, we have implemented a highly effective passivation scheme based on lipid bilayers. We show long-term passivation of nanochannel surfaces to several relevant reagents and demonstrate that the performance of the lipid bilayer is significantly better compared to standard bovine serum albumin-based passivation. Moreover, we demonstrate how the passivated devices allow us to monitor single DNA cleavage events during enzymatic degradation.
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5.
  • Kesarimangalam, Sriram, 1983, et al. (författare)
  • Fluorescence Microscopy of Nanochannel-Confined DNA
  • 2024
  • Ingår i: Methods in Molecular Biology. - 1940-6029 .- 1064-3745. - 9781071633762 - 9781071633779 ; , s. 175-202
  • Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
    • Stretching of DNA in nanoscale confinement allows for several important studies. The genetic contents of the DNA can be visualized on the single DNA molecule level, and the polymer physics of confined DNA and also DNA/protein and other DNA/DNA-binding molecule interactions can be explored. This chapter describes the basic steps to fabricate the nanostructures, perform the experiments, and analyze the data.
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6.
  • Nyberg, Lena, 1979, et al. (författare)
  • A single-step competitive binding assay for mapping of single DNA molecules
  • 2012
  • Ingår i: Biochemical and Biophysical Research Communications - BBRC. - : Elsevier BV. - 0006-291X .- 1090-2104. ; 417:1, s. 404-408
  • Tidskriftsartikel (refereegranskat)abstract
    • Optical mapping of genomic DNA is of relevance for a plethora of applications such as scaffolding for sequencing and detection of structural variations as well as identification cif pathogens like bacteria and viruses. For future clinical applications it is desirable to have a fast and robust mapping method based on as few steps as possible. We here demonstrate a single-step method to obtain a DNA barcode that is directly visualized using nanofluidic devices and fluorescence microscopy. Using a mixture of YOYO-1, a bright DNA dye, and netropsin, a natural antibiotic with very high AT specificity, we obtain a DNA map with a fluorescence intensity profile along the DNA that reflects the underlying sequence. The netropsin binds to AT-tetrads and blocks these binding sites from YOYO-1 binding which results in lower fluorescence intensity from AT-rich regions of the DNA. We thus obtain a DNA barcode that is dark in AT-rich regions and bright in GC-rich regions with kilobasepair resolution. We demonstrate the versatility of the method by obtaining a barcode on DNA from the phage T4 that captures its circular permutation and agrees well with its known sequence.
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7.
  • Persson, Fredrik, et al. (författare)
  • Fluorescence microscopy of nanochannel-confined DNA
  • 2011
  • Ingår i: Single Molecule Analysis : Methods and Protocols - Methods and Protocols. - Totowa, NJ : Humana Press. - 1064-3745. - 9781617792816 ; 783, s. 159-179
  • Bokkapitel (refereegranskat)abstract
    • Stretching of DNA in nanoscale confinement allows for direct visualization of the genetic contents of the DNA on the single DNA molecule level. DNA stretched in nanoscale confinement also allows for studies of DNA-protein interactions and DNA polymer physics in confined environments. This chapter describes the basic steps to fabricate the nanostructures, to perform the experiments, and to analyze the data.
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8.
  • Persson, Fredrik, 1979, et al. (författare)
  • Lipid-Based Passivation in Nanofluidics
  • 2012
  • Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 12:5, s. 2260-2265
  • Tidskriftsartikel (refereegranskat)abstract
    • Stretching DNA in nanochannels is a useful tool for direct, visual studies of genomic DNA at the single molecule level. To facilitate the study of the interaction of linear DNA with proteins in nanochannels, we have implemented a highly effective passivation scheme based on lipid bilayers. We demonstrate virtually complete long-term passivation of nanochannel surfaces to a range of relevant reagents, including streptavidin-coated quantum dots, RecA proteins, and RecA-DNA complexes. We show that the performance of the lipid bilayer is significantly better than that of standard bovine serum albumin-based passivation. Finally, we show how the passivated devices allow us to monitor single DNA cleavage events during enzymatic degradation by DNase I. We expect that our approach will open up for detailed, systematic studies of a wide range of protein-DNA interactions with high spatial and temporal resolution.
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9.
  • Persson, Fredrik, 1979, et al. (författare)
  • Local conformation of confined DNA studied using emission polarization anisotropy
  • 2010
  • Ingår i: Biophysical Society 54th Annual Meeting.
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • When confined in nanochannels with dimensions smaller than the DNA radius of gyration, DNA will extend along the channel. We investigate long DNA confined in nanochannels, using fluorescence microscopy and intercalated dyes. Studies of the dynamics and statics of DNA in such nanoscale confinements as a function of e.g. degree of confinement and ionic strength have yielded new insights into the physical properties of DNA with relevance for applications in genomics as well as fundamental understanding of DNA packaging in vivo. Our work extends the field by not only studying the location of the emitting dyes along a confined DNA molecule but also monitoring the polarization of the emitted light. By measuring the emission polarized parallel and perpendicular to the extension axis of the stretched DNA, information on the local spatial distribution of the DNA backbone can be obtained. Comparing polarizations in two directions for DNA confined in channels of effective diameters of 85 nm and 170 nm reveals a striking difference. Whereas the DNA in the larger channels shows an isotropic polarization of the emitted light, the light is to a large extent polarized perpendicular to the elongation of the DNA in the smaller channels. We expect this technique to have a large impact on the studies of changes in DNA conformation induced by protein binding or during DNA compactation as well as in fundamental polymer physics studies of DNA in confined environments, for example in bacterial spores and viruses.
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10.
  • Persson, Fredrik, 1979, et al. (författare)
  • Local conformation of confined DNA studied using emission polarization anisotropy
  • 2010
  • Ingår i: NanoBioTech-Montreux 2009.
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • In nanochannels with dimensions smaller than the DNA radius of gyration, DNA will extend along the channel. We investigate long DNA confined in nanochannels using fluorescence microscopy and intercalated dyes. Studies of the dynamics and statics of the DNA extension or position in such nanoscale confinements as a function of e.g. DNA contour length, degree and shape of confinement as well as ionic strength have yielded new insights in the physical properties of DNA with relevance for applications in genomics as well as fundamental understanding of DNA packaging in vivo. Our work extends the field by not only studying the location of the emitting dyes along a confined DNA molecule but also monitoring the polarization of the emitted light. We use intercalating dyes (YOYO-1) whose emission is polarized perpendicular to the DNA extension axis, and by measuring the emission polarized parallel and perpendicular to the extension axis of the stretched DNA, information on the local spatial distribution of the DNA backbone can be obtained. The results obtained are analogous to linear dichroism (LD) but on a single-molecule level, and obtained in a highly parallel fashion. We will discuss results in shallow (60 nm) and deep (180 nm) channels and describe an example of how the technique can be used to investigate non-uniform stretching of DNA on the single molecule level. Comparing polarizations in two directions for DNA confined in channels of effective diameters of 85 nm and 170 nm reveals a striking difference. Whereas the DNA in the larger channels shows an isotropic polarization of the emitted light, the light is to a large extent polarized perpendicular to the elongation of the DNA in the smaller channels. The ratio of the polarization parallel and perpendicular to the elongation direction, I|| / I⊥, is a measure of the relative local orientation of the DNA backbone. We believe that this technique will have a large impact on the studies of changes in DNA conformation induced by protein binding or during DNA compactation as well as in fundamental polymer physics studies of DNA in confined environments, for example in bacterial spores and viruses.
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