Proteins Breaking Bad: A Free Energy Perspective

Valle-Orero, Jessica; Tapia‐Rojo, Rafael; Eckels, Edward C.; Rivas‐Pardo, Jaime Andrés; Popa, Ionel; Fernández, Julio M.

doi:10.1021/acs.jpclett.7b01509

Cited by 24 publications

(23 citation statements)

References 50 publications

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“…We demonstrate the goodness of our calibration by reproducing the folding/unfolding properties of protein L (SI Appendix, Fig. S9), which match those previously measured (10,22). As we demonstrated previously (11), the bead-to-bead variation in the M-270 is very small (just 1.4% of dispersion in size; SI Appendix).…”

Section: Magneticsupporting

confidence: 83%

Ephemeral states in protein folding under force captured with a magnetic tweezers design

Tapia‐Rojo

Eckels

Fernández

2019

Proc. Natl. Acad. Sci. U.S.A.

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Magnetic tape heads are ubiquitously used to read and record on magnetic tapes in technologies as diverse as old VHS tapes, modern hard-drive disks, or magnetic bands on credit cards. Their design highlights the ability to convert electric signals into fluctuations of the magnetic field at very high frequencies, which is essential for the high-density storage demanded nowadays. Here, we twist this conventional use of tape heads to implement one in a magnetic tweezers design, which offers the unique capability of changing the force with a bandwidth of ∼10 kHz. We calibrate our instrument by developing an analytical expression that predicts the magnetic force acting on a superparamagnetic bead based on the Karlqvist approximation of the magnetic field created by a tape head. This theory is validated by measuring the force dependence of protein L unfolding/folding step sizes and the folding properties of the R3 talin domain. We demonstrate the potential of our instrument by carrying out millisecond-long quenches to capture the formation of the ephemeral molten globule state in protein L, which has never been observed before. Our instrument provides the capability of interrogating individual molecules under fast-changing forces with a control and resolution below a fraction of a piconewton, opening a range of force spectroscopy protocols to study protein dynamics under force. dynamic force spectroscopy | protein mechanics | protein folding | molten globule state | magnetic tape head M agnetic head recording systems have been perfected over decades, resulting in a deep understanding of the physical features of magnetic tape heads, which evolved to create strong magnetic fields that can change very rapidly in time (1, 2). Hence, it becomes natural that we explore the use of this technology in its application to force spectroscopy. Magnetic tweezers force spectroscopy uses magnetic field gradients to apply pulling forces on biomolecules tethered to superparamagnetic beads (3-9). Due to the extreme compliance of the magnetic trap, magnetic tweezers offer intrinsic force-clamp conditions and an exquisite control of the pulling force, which, combined with HaloTag covalent chemistry, provides an inherent stability and gives access to long timescales, of several hours or even days (10-13). However, in standard magnetic tweezers instruments, the force change is limited by the mechanical movement of the pair of magnets, which can take up to 100 ms, and impedes capturing early molecular events occurring upon fast force quenches or applying force protocols where the force changes rapidly, motivating the need to implement fast-changing magnetic fields.In this article, we present magnetic tape head tweezers, a force spectrometer capable of changing the force on a microsecond timescale, while maintaining an impeccable control of it. According to the Karlqvist description of the magnetic field created by a tape head (14), we provide a full analytic description of the pulling force, which allows us to calibrate our instrument over a ...

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Section: Magneticsupporting

confidence: 83%

Ephemeral states in protein folding under force captured with a magnetic tweezers design

Tapia‐Rojo

Eckels

Fernández

2019

Proc. Natl. Acad. Sci. U.S.A.

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“…We demonstrate the goodness of our calibration by reproducing the folding/unfolding properties of protein L (SI Appendix, Fig. S9), which match those previously measured [10,24]. As we demonstrated previously [11], the bead-to-bead variation in the M-270 is very small (just 1.4% of dispersion in size, see SI Appendix).…”

Section: Calibration Of the Magnetic Tape Head Tweezers Using Proteinsupporting

confidence: 83%

Ephemeral states in protein folding under force captured with a novel magnetic tweezers design

Tapia‐Rojo¹,

Eckels²,

Fernández³

2018

Preprint

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Magnetic heads are ubiquitously used to record and read on magnetic tapes in technologies as diverse as old cassettes or VHS tapes, modern hard drive disks, or magnetic bands in credit/debit or subway cards. They are designed to convert electric signals into fluctuations on the magnetic field at very high frequencies, crucial for the high density storage which is demanded nowadays. Here, we twist this traditional use of magnetic heads and implement one in a new force spectrometer design, where the magnetic field is used to pull on proteins tethered to superparamagnetic beads.Our instrument offers the same features as magnetic tweezers-intrinsic force-clamp conditions, with accurate control of the force, and intrinsic stability-, but with the novel ability of changing the force instantaneously, which allows to investigate protein dynamics at very short timescales, or under arbitrary force signals. We calibrate our instrument by relying on Karlqvist approximation of the field created by a magnetic head-the first building block of magnetic recording theory-through the force scaling of the unfolding/folding step-sizes of protein L, used as a molecular template. This results in a force range between 0 and 50 pN, when working at distances above 250 µm, and electric currents up to 1 A. We illustrate the potential of our instrument by studying the folding mechanism of protein L upon ultra-fast force quenches. This allows us to describe that, in a short timescale of 50 ms, the unfolded protein L evolves to an

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“…S4), which make them canonical models for stochastic resonance to occur [28]. By contrast, other proteins that have been characterized under force, such as protein L or the titin I91 domain, have very shallow force-dependencies of their unfolding rates, which leads to short distances to transition state from the folded state and very asymmetric folding landscapes [36,37]. Hence, it is unclear if proteins with these characteristics would exhibit entrained folding dynamics, given that their folding landscapes do not fulfill the ideal conditions to undergo stochastic resonance.…”

Section: Discussionmentioning

confidence: 99%

Talin Folding as the Tuning Fork of Cellular Mechanotransduction

Tapia‐Rojo

Fernández²

2020

Preprint

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Cells continually sample their mechanical environment using exquisite force sensors such as talin, whose folding status triggers mechanotransduction pathways by recruiting binding partners. Mechanical signals in biology change quickly over time and are often embedded in noise; however, the mechanics of force-sensing proteins have only been tested using simple force protocols, such as constant or ramped forces. Here, using our magnetic tape head tweezers design, we measure the folding dynamics of single talin proteins in response to mechanical noise and cyclic force perturbations. Our experiments demonstrate that talin filters out mechanical noise but detects periodic force signals over a finely-tuned frequency range. Hence, talin operates as a mechanical bandpass filter, able to read and interpret frequency-dependent mechanical information through its folding dynamics. We describe our observations in the context of stochastic resonance, which we propose as a mechanism by which mechanosensing proteins could respond accurately to force signals in the naturally noisy biological environment. *

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Proteins Breaking Bad: A Free Energy Perspective

Cited by 24 publications

References 50 publications

Ephemeral states in protein folding under force captured with a magnetic tweezers design

Ephemeral states in protein folding under force captured with a magnetic tweezers design

Ephemeral states in protein folding under force captured with a novel magnetic tweezers design

Talin Folding as the Tuning Fork of Cellular Mechanotransduction

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