Showing papers by "Jens H. Gundlach published in 2021"
TL;DR: The Newtonian Calibrator as mentioned in this paper uses a rotor consisting of both quadrupole and hexapole mass distributions to apply a time-varying gravitational force on one of the observatory's test masses.
Abstract: The precise calibration of the strain readout of the LIGO gravitational wave observatories is paramount to the accurate interpretation of gravitational wave events. This calibration is traditionally done by imparting a known force on the test masses of the observatory via radiation pressure. Here we describe the implementation of an alternative calibration scheme: the Newtonian Calibrator. This system uses a rotor consisting of both quadrupole and hexapole mass distributions to apply a time-varying gravitational force on one of the observatory's test masses. The force produced by this rotor can be predicted to $<1\%$ relative uncertainty and is well-resolved in the readout of the observatory. This system currently acts as a cross-check of the existing absolute calibration system.
9 citations
TL;DR: In this article, single-molecule picometer resolution nanopore tweezers (SPRNTs) are used to monitor the motion of individual enzymes along a nucleic acid template at unprecedented spatiotemporal resolution.
Abstract: Single-molecule picometer resolution nanopore tweezers (SPRNT) is a technique for monitoring the motion of individual enzymes along a nucleic acid template at unprecedented spatiotemporal resolution. We review the development of SPRNT and the application of single-molecule kinetics theory to SPRNT data to develop a detailed model of helicase motion along a single-stranded DNA substrate. In this review, we present three examples of questions SPRNT can answer in the context of the Superfamily 2 helicase Hel308. With Hel308, SPRNT's spatiotemporal resolution enables resolution of two distinct enzymatic substates, one which is dependent upon ATP concentration and one which is ATP independent. By analyzing dwell-time distributions and helicase back-stepping, we show, in detail, how SPRNT can be used to determine the nature of these observed steps. We use dwell-time distributions to discern between three different possible models of helicase backstepping. We conclude by using SPRNT's ability to discern an enzyme's nucleotide-specific location along a DNA strand to understand the nature of sequence-specific enzyme kinetics and show that the sequence within the helicase itself affects both step dwell-time and backstepping probability while translocating on single-stranded DNA.
6 citations
TL;DR: In this article, a torsion pendulum with a large mass-quadrupole moment and a resonant frequency of 2.8 mHz is described, whose angle is measured using a Michelson interferometer.
Abstract: We describe a torsion pendulum with a large mass-quadrupole moment and a resonant frequency of 2.8 mHz, whose angle is measured using a Michelson interferometer. The system achieved noise levels of ∼200prad/Hz between 0.2 and 30 Hz and ∼10prad/Hz above 100 Hz. Such a system can be applied to a broad range of fields from the study of rotational seismic motion and elastogravity signals to gravitational wave observation and tests of gravity.
6 citations
TL;DR: In this article, a torsion pendulum with a large mass-quadrupole moment and a resonant frequency of 2.8 mHz is described, whose angle is measured using a modified Michelson interferometer.
Abstract: We describe a torsion pendulum with a large mass-quadrupole moment and a resonant frequency of 2.8 mHz, whose angle is measured using a modified Michelson interferometer. The system achieved noise levels of $\sim200\ \text{prad}/\sqrt{\text{Hz}}$ between 0.2-30 Hz and $\sim10\ \text{prad}/\sqrt{\text{Hz}}$ above 100 Hz. Such a system can be applied to a broad range of fields from the study of rotational seismic motion and elastogravity signals to gravitational wave observation and tests of gravity.
4 citations
Posted Content•
TL;DR: The Newtonian Calibrator as discussed by the authors uses a rotor consisting of both quadrupole and hexapole mass distributions to apply a time-varying gravitational force on one of the observatory's test masses.
Abstract: The precise calibration of the strain readout of the LIGO gravitational wave observatories is paramount to the accurate interpretation of gravitational wave events. This calibration is traditionally done by imparting a known force on the test masses of the observatory via radiation pressure. Here we describe the implementation of an alternative calibration scheme: the Newtonian Calibrator. This system uses a rotor consisting of both quadrupole and hexapole mass distributions to apply a time-varying gravitational force on one of the observatory's test masses. The force produced by this rotor can be predicted to $<1\%$ relative uncertainty and is well-resolved in the readout of the observatory. This system currently acts as a cross-check of the existing absolute calibration system.
1 citations
Posted Content•
TL;DR: In this paper, the authors used a stationary torsion balance with a beryllium-aluminum composition dipole to search for ultra low-mass bosonic dark matter coupled to baryon minus lepton number.
Abstract: We used a stationary torsion balance with a beryllium-aluminum composition dipole to search for ultra low-mass bosonic dark matter coupled to baryon minus lepton number. We set 95% confidence limits on the coupling constant $g_{\rm B-L}$ for bosons with masses between $10^{-18}$ and $10^{-16}$ eV/$c^2$ with the best performance at $m_{\rm DM} = 8\times 10^{-18}$ eV/$c^2$ constraining $g_{B-L}(\hbar c)^{-1/2} < 1 \times 10^{-25}$. This provides a complimentary limit to equivalence-principle experiments that search for ultra low-mass bosons as force-mediating particles.
TL;DR: In this paper, the authors showed that α-Synuclein (αSyn), an intrinsically disordered, membrane-active, neuronal protein implicated in Parkinson disease, can be reversibly captured by the VDAC nanopore.
Abstract: Nanopore sensing is based on detection and analysis of nanopore transient conductance changes induced by analyte capture. We have recently shown that α-Synuclein (αSyn), an intrinsically disordered, membrane-active, neuronal protein implicated in Parkinson disease, can be reversibly captured by the VDAC nanopore. The capture process is a highly voltage dependent complexation of the two proteins where transmembrane potential drives the polyanionic C-terminal domain of αSyn into VDAC--exactly the mechanism by which generic nanopore-based interrogation of proteins and polynucleotides proceeds. The complex formation, and the motion of αSyn in the nanopore, thus may be expected to be only indirectly dependent on the pore identity. Here, we confirm this prediction by demonstrating that when VDAC is replaced with a different transmembrane pore, the engineered mycobacterial porin M2MspA, all the qualitative features of the αSyn/nanopore interaction are preserved. The rate of αSyn capture by M2MspA rises exponentially with the applied field, while the residence time displays a crossover behavior, indicating that at voltages >50 mV M2MspA-bound αSyn largely undergoes translocation to the other side of the membrane. The translocation is directly confirmed using the selectivity tag method, in which the polyanionic C-terminal and neutral N-terminal regions of αSyn alter the selectivity of the M2MspA channel differently, allowing direct discrimination of translocation vs retraction for single αSyn molecules. We thus prove that the physical model of the motion of disordered protein chains in the nanopore confinement and the selectivity tag technique are not limited to VDAC but are broadly applicable to nanopore-based protein detection, analysis, and separation technologies.
TL;DR: In this paper, the authors used Nanopore Tweezers to observe the small, fast steps taken by single RecQ helicases as they step along and unwind DNA at ultrahigh spatiotemporal resolution.
Abstract: Helicases are essential for nearly all nucleic acid processes across the tree of life. Using Nanopore Tweezers we observed the small, fast steps taken by single RecQ helicases as they step along and unwind DNA at ultrahigh spatiotemporal resolution. By directly measuring conformational substates of RecQ we determine the coupling between helicase domain motions and chemical reactions that together produce forward motion along the DNA. Application of assisting and opposing forces shows that RecQ has a highly asymmetric energy landscape that reduces its sensitivity to opposing mechanical forces that could be encountered in vivo by molecular roadblocks such as DNA bound proteins. This energy landscape enables RecQ to maintain speed against an opposing load.