File Name: construction and calibration of an optical trap on a fluorescence optical microscope.zip
Authoritative and cutting-edge, Optical Tweezers: Methods and Protocols aims help to further expand the accessibility and use of optical traps by scientists of diverse disciplines.
These laser-based tweezers, or traps, have been employed in numerous biological experiments. Biological applications for optical tweezers include trapping viruses and bacteria, manipulating cellular structures, patterning of surfaces, and measuring forces of molecular motors and biological molecules such as DNA and proteins.
This design is based on a conventional, inverted microscope, operating under plain bright field illumination. A single laser beam enables standard optical trapping and the measurement of molecular displacements and forces, whereas digital image processing affords real-time sample visualization with reduced noise and enhanced contrast. We have tested our trapping and imaging instrument by measuring the persistence length of individual double-stranded DNA molecules, and by following the stepping of single kinesin motor proteins along clearly imaged microtubules. The approach presented here provides a straightforward alternative for studies of biomaterials and individual biomolecules. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing interests: The authors have declared that no competing interests exist.
Laser tweezers ; Optical trap. The technique of optical tweezers and manipulation of small neutral particles by lasers is based on the forces of radiation pressure. These forces arise from the momentum of the light itself. It has been first documented by Arthur Ashkin in that optical forces, or radiation pressure, could be used to trap and accelerate dielectric polarizable micron-sized particles [ 1 ]. For these experiments, a stable optical potential well was formed using two, slightly divergent, counter-propagating laser beams. This pioneering study established the groundwork for the well-known optical tweezers OT technique, where a single TEM 00 laser beam is focused by a high numerical aperture NA objective lens to a diffraction limited spot. Skip to main content Skip to table of contents.
Optical tweezers originally called single-beam gradient force trap are scientific instruments that use a highly focused laser beam to hold and move microscopic and sub-microscopic objects like atoms , nanoparticles and droplets, in a manner similar to tweezers. If the object is held in air or vacuum without additional support, it can be called optical levitation. The laser light provides an attractive or repulsive force typically on the order of pico newtons , depending on the relative refractive index between particle and surrounding medium. Levitation is possible if the force of the light counters the force of gravity. The trapped particles are usually micron -sized, or smaller.
Since the time of their introduction, optical tweezers OTs have grown to be a powerful tool in the hands of biologists. OTs use highly focused laser light to guide, manipulate, or sort target objects, typically in the nanoscale to microscale range. OTs have been particularly useful in making quantitative measurements of forces acting in cellular systems; they can reach inside living cells and be used to study the mechanical properties of the fluids and structures that they contain. As all the measurements are conducted without physically contacting the system under study, they also avoid complications related to contamination and tissue damage. From the manipulation of fluorescent nanodiamonds to chromosomes, cells, and free-swimming bacteria, OTs have now been extended to challenging biological systems such as the vestibular system in zebrafish.
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Клушар кивнул: - Со спутницей. Роскошной рыжеволосой девицей. Мой Бог.
В этой встрече было что-то нереальное - нечто, заставившее снова напрячься все его нервные клетки. Он поймал себя на том, что непроизвольно пятится от незнакомцев. Тот, что был пониже ростом, смерил его холодным взглядом. - Сюда, мистер Беккер. Быстрее.
Мидж. Ответа не последовало. Бринкерхофф подошел к кабинету. Голоса показались ему знакомыми.
Si, - сказал Беккер. - Solo.
Сьюзан, - начал он, - я не был с тобой вполне откровенен. ГЛАВА 73 У Дэвида Беккера было такое ощущение, будто его лицо обдали скипидаром и подожгли. Он катался по полу и сквозь мутную пелену в глазах видел девушку, бегущую к вращающейся двери. Она бежала короткими испуганными прыжками, волоча по кафельному полу туристскую сумку.