1,229 research outputs found

    Highly birefringent TiO2 nanocylinders : characterization and application in the optical torque wrench

    Get PDF
    Recent advances in optical tweezers have enabled the direct manipulation and measurement of optical torque using light spin momentum transferred to trapped birefringent particles. This powerful technique, termed Optical Torque Wrench (OTW), relies on trapping of quartz (SiO2) microcylinders which have become a standard and convenient probe for single-molecule studies. Here, we explore an alternative photonic probe based on rutile (TiO2) which has almost thirty-fold larger birefringence compared to quartz particles. By employing this promising material to fabricate rutile nanocylinders whose sizes can be easily tuned, we significantly enhance the accessible range of optical torques and angular frequencies in the OTW. In future, these novel photonic probes will allow us to study not only slowly processing torque-generating biological systems, as the genome processing machinery, but also fast rotating motors, including ATP-synthase and the bacterial flagellar motor

    Trapping of highly birefringent rutile nanocylinders in the optical torque wrench

    Get PDF
    The optical torque wrench (OTW) is a powerful technique to measure the torsional properties of different biomolecules, including DNA, DNA- processing protein complexes and rotary motors. To date, quartz has proven to be a convenient birefringent material out of which to synthesize the micron-sized particles essential for this technique. However, the relatively low birefringence of quartz, which limits the maximal torque that can be applied in OTW, hampers the study of certain biological systems. A more attractive material is rutile, which has a thirty-fold higher birefringence. To date, however, the application of rutile in the trapping has been restricted due to its high refractive index, which results in low trapping efficiency. Here, we have employed finite element method calculations to determine the optimal dimensions of sub-micron-sized rutile cylinders for tight stable optical trapping. Using these calculations as a guideline, we have designed and devel- oped a nanofabrication protocol that allows us to produce rutile cylinders with the desired sizes at high yield. We have characterized the fabricated cylinders in the OTW setup and quantified both their linear and angular trapping proper- ties. In addition, we demonstrate full translational and rotational control of these functionalized cylinders tethered to individual DNA molecules for use in single-molecule applications

    Analgesic effect of highly reversible ω-conotoxin FVIA on N type Ca2+ channels

    Get PDF
    <p>Abstract</p> <p>Background</p> <p>N-type Ca<sup>2+ </sup>channels (Ca<sub>v</sub>2.2) play an important role in the transmission of pain signals to the central nervous system. ω-Conotoxin (CTx)-MVIIA, also called ziconotide (Prialt<sup>®</sup>), effectively alleviates pain, without causing addiction, by blocking the pores of these channels. Unfortunately, CTx-MVIIA has a narrow therapeutic window and produces serious side effects due to the poor reversibility of its binding to the channel. It would thus be desirable to identify new analgesic blockers with binding characteristics that lead to fewer adverse side effects.</p> <p>Results</p> <p>Here we identify a new CTx, FVIA, from the Korean <it>Conus Fulmen </it>and describe its effects on pain responses and blood pressure. The inhibitory effect of CTx-FVIA on N-type Ca<sup>2+ </sup>channel currents was dose-dependent and similar to that of CTx-MVIIA. However, the two conopeptides exhibited markedly different degrees of reversibility after block. CTx-FVIA effectively and dose-dependently reduced nociceptive behavior in the formalin test and in neuropathic pain models, and reduced mechanical and thermal allodynia in the tail nerve injury rat model. CTx-FVIA (10 ng) also showed significant analgesic effects on writhing in mouse neurotransmitter- and cytokine-induced pain models, though it had no effect on acute thermal pain and interferon-γ induced pain. Interestingly, although both CTx-FVIA and CTx-MVIIA depressed arterial blood pressure immediately after administration, pressure recovered faster and to a greater degree after CTx-FVIA administration.</p> <p>Conclusions</p> <p>The analgesic potency of CTx-FVIA and its greater reversibility could represent advantages over CTx-MVIIA for the treatment of refractory pain and contribute to the design of an analgesic with high potency and low side effects.</p

    Optimasi Portofolio Resiko Menggunakan Model Markowitz MVO Dikaitkan dengan Keterbatasan Manusia dalam Memprediksi Masa Depan dalam Perspektif Al-Qur`an

    Full text link
    Risk portfolio on modern finance has become increasingly technical, requiring the use of sophisticated mathematical tools in both research and practice. Since companies cannot insure themselves completely against risk, as human incompetence in predicting the future precisely that written in Al-Quran surah Luqman verse 34, they have to manage it to yield an optimal portfolio. The objective here is to minimize the variance among all portfolios, or alternatively, to maximize expected return among all portfolios that has at least a certain expected return. Furthermore, this study focuses on optimizing risk portfolio so called Markowitz MVO (Mean-Variance Optimization). Some theoretical frameworks for analysis are arithmetic mean, geometric mean, variance, covariance, linear programming, and quadratic programming. Moreover, finding a minimum variance portfolio produces a convex quadratic programming, that is minimizing the objective function ðð¥with constraintsð ð 𥠥 ðandð´ð¥ = ð. The outcome of this research is the solution of optimal risk portofolio in some investments that could be finished smoothly using MATLAB R2007b software together with its graphic analysis

    Search for supersymmetry in events with one lepton and multiple jets in proton-proton collisions at root s=13 TeV