Ignas Gaska, Mason E. Armstrong, April Alfieri, Scott Forth
Cell division in eukaryotes requires the regulated assembly of the spindle apparatus. The proper organization of microtubules within the spindle is driven by motor proteins that exert forces to slide filaments, whereas non-motor proteins crosslink filaments into higher-order motifs, such as overlapping bundles. It is not clear how active and passive forces are integrated to produce regulated mechanical outputs within spindles. Here, we employ simultaneous optical trapping and total internal reflection fluorescence (TIRF) microscopy to directly measure the frictional forces produced by the mitotic crosslinking protein PRC1 that resist microtubule sliding. These forces scale with microtubule sliding velocity and the number of PRC1 crosslinks but do not depend on overlap length or PRC1 density within overlaps. Our results suggest that PRC1 ensembles act similarly to a mechanical dashpot, producing significant resistance against fast motions but minimal resistance against slow motions, allowing for the integration of diverse motor activities into a single mechanical outcome.
DOI
Monday, September 7, 2020
Optical trapping in the presence of laser-induced thermal effects
J. A. Zenteno-Hernandez, J. Vázquez Lozano, J. A. Sarabia-Alonso, J. Ramírez-Ramírez, and R. Ramos-García
The inclusion of thermal effects in optical manipulation has been explored in diverse experiments, increasing the possibilities for applications in diverse areas. In this Letter, the results of combined optical and thermal manipulation in the vicinity of a highly absorbent hydrogenated amorphous silicon layer, which induces both the generation of convective currents and thermophoresis, are presented. In combination with the optical forces, thermal forces help reduce the optical power required to trap and manipulate micrometric polystyrene beads. Moreover, the inclusion of these effects allows the stacking and manipulation of multiple particles with a single optical trap along with the beam propagation, providing an extra tool for micromanipulation of a variety of samples.
DOI
The inclusion of thermal effects in optical manipulation has been explored in diverse experiments, increasing the possibilities for applications in diverse areas. In this Letter, the results of combined optical and thermal manipulation in the vicinity of a highly absorbent hydrogenated amorphous silicon layer, which induces both the generation of convective currents and thermophoresis, are presented. In combination with the optical forces, thermal forces help reduce the optical power required to trap and manipulate micrometric polystyrene beads. Moreover, the inclusion of these effects allows the stacking and manipulation of multiple particles with a single optical trap along with the beam propagation, providing an extra tool for micromanipulation of a variety of samples.
DOI
Single-Cell Multimodal Analytical Approach by Integrating Raman Optical Tweezers and RNA Sequencing
Teng Fang, Wenhao Shang, Chang Liu, Yaoyao Liu, and Anpei Ye
Single-cell analysis has become a state-of-art approach to heterogeneity profiling in tumor cells. Herein, we realize a kind of single-cell multimodal analytical approach by combining single-cell RNA sequencing (scRNA-seq) with Raman optical tweezers (ROT), a label-free single-cell identification and isolation technique, and apply it to investigate drug sensitivity. The drug sensitivity of human BGC823 gastric cancer cells toward different drugs, paclitaxel and sodium dichloroacetate, was distinguished in the conjoint analytical way including morphology monitoring, Raman identification, and transcriptomic profiling. Each individual BGC823 cancer cell was measured by Raman spectroscopy, then nondestructively isolated out by ROT, and finally RNA-sequenced. Our results demonstrate each analytical mode can reflect cell response to the drugs from different perspectives and is consistent and complementary with each other. Therefore, we believe the multimodal analytical approach offers an access to comprehensive characterizations of the unicellular complexity, which especially makes sense for studying tumor heterogeneity or a desired special cell from a mixture cell sample such as whole blood.
DOI
Single-cell analysis has become a state-of-art approach to heterogeneity profiling in tumor cells. Herein, we realize a kind of single-cell multimodal analytical approach by combining single-cell RNA sequencing (scRNA-seq) with Raman optical tweezers (ROT), a label-free single-cell identification and isolation technique, and apply it to investigate drug sensitivity. The drug sensitivity of human BGC823 gastric cancer cells toward different drugs, paclitaxel and sodium dichloroacetate, was distinguished in the conjoint analytical way including morphology monitoring, Raman identification, and transcriptomic profiling. Each individual BGC823 cancer cell was measured by Raman spectroscopy, then nondestructively isolated out by ROT, and finally RNA-sequenced. Our results demonstrate each analytical mode can reflect cell response to the drugs from different perspectives and is consistent and complementary with each other. Therefore, we believe the multimodal analytical approach offers an access to comprehensive characterizations of the unicellular complexity, which especially makes sense for studying tumor heterogeneity or a desired special cell from a mixture cell sample such as whole blood.
DOI
Optical trapping of antihydrogen towards an atomic anti-clock
P. Crivelli & N. Kolachevsky
The unprecedented flux of low energy antiprotons delivered by the Extra Low ENergy Antiprotons (ELENA) ring, being under commissioning at CERN, will open a new era for precision tests with antimatter including laser and microwave spectroscopy and tests ofits gravitational behaviour. Here we present an alternative to magnetic trapping to perform ultra-high precision laser spectroscopy of antihydrogen. The proposed scheme is to load the ultra cold anti-hydrogen atoms produced by the GBAR experiment in an optical trap tuned at the magicwavelength of the 1S–2S transition in order to measure this interval at a level comparable or even better than its matter counter part. This will provide a very accurate test of Lorentz/CPT violating effects which can be parametrised in the framework of the Standard Model Extension.
DOI
The unprecedented flux of low energy antiprotons delivered by the Extra Low ENergy Antiprotons (ELENA) ring, being under commissioning at CERN, will open a new era for precision tests with antimatter including laser and microwave spectroscopy and tests ofits gravitational behaviour. Here we present an alternative to magnetic trapping to perform ultra-high precision laser spectroscopy of antihydrogen. The proposed scheme is to load the ultra cold anti-hydrogen atoms produced by the GBAR experiment in an optical trap tuned at the magicwavelength of the 1S–2S transition in order to measure this interval at a level comparable or even better than its matter counter part. This will provide a very accurate test of Lorentz/CPT violating effects which can be parametrised in the framework of the Standard Model Extension.
DOI
Tuesday, September 1, 2020
Metallic particle manipulation with adjustable trapping range through customized field
Zhidong Bai, Shuoshuo Zhang, Yudong Lyu, Rui Zhao, Xifu Yue, Xiaolu Ge, Shenggui Fu, Zhongsheng Man
Since the invention of optical tweezers, optical manipulation has advanced significantly in many applications, including atomic physics, biochemistry and soft matter physics. Here, we propose a method to trap metallic particles with adjustable trapping range in the transverse plane with the help of customized field. By tailoring the polarization state of the incident field, the focal field with elongation in the direction perpendicular to optical axis can be turned in the 4 focusing system. As a result, optical trapping with tunable trapping range is possible when the metallic particle is interacted with such customized field.
DOI
Since the invention of optical tweezers, optical manipulation has advanced significantly in many applications, including atomic physics, biochemistry and soft matter physics. Here, we propose a method to trap metallic particles with adjustable trapping range in the transverse plane with the help of customized field. By tailoring the polarization state of the incident field, the focal field with elongation in the direction perpendicular to optical axis can be turned in the 4 focusing system. As a result, optical trapping with tunable trapping range is possible when the metallic particle is interacted with such customized field.
DOI
Femtosecond laser trapping dynamics of two-photon absorbing hollow-core nanoparticles
Liping Gong, Xiaohe Zhang, Zhuqing Zhu, Guanghao Rui, Jun He, Yiping Cui, and Bing Gu
We investigate femtosecond laser trapping dynamics of two-photon absorbing hollow-core nanoparticles with different volume fractions and two-photon absorption (TPA) coefficients. Numerical simulations show that the hollow-core particles with low and high-volume fractions can easily be trapped and bounced by the tightly focused Gaussian laser pulses, respectively. Further studies show that the hollow-core particles with and without TPA can be identified, because the TPA effect enhances the radiation force, and subsequently the longitudinal force destabilizes the trap by pushing the particle away from the focal point. The results may find direct applications in particle sorting and characterizing the TPA coefficient of single nanoparticles.
DOI
We investigate femtosecond laser trapping dynamics of two-photon absorbing hollow-core nanoparticles with different volume fractions and two-photon absorption (TPA) coefficients. Numerical simulations show that the hollow-core particles with low and high-volume fractions can easily be trapped and bounced by the tightly focused Gaussian laser pulses, respectively. Further studies show that the hollow-core particles with and without TPA can be identified, because the TPA effect enhances the radiation force, and subsequently the longitudinal force destabilizes the trap by pushing the particle away from the focal point. The results may find direct applications in particle sorting and characterizing the TPA coefficient of single nanoparticles.
DOI
Precise capture and dynamic relocation of nanoparticulate biomolecules through dielectrophoretic enhancement by vertical nanogap architectures
Eui-Sang Yu, Hyojin Lee, Sun-Mi Lee, Jiwon Kim, Taehyun Kim, Jongsu Lee, Chulki Kim, Minah Seo, Jae Hun Kim, Young Tae Byun, Seung-Chul Park, Seung-Yeol Lee, Sin-Doo Lee & Yong-Sang Ryu
Toward the development of surface-sensitive analytical techniques for biosensors and diagnostic biochip assays, a local integration of low-concentration target materials into the sensing region of interest is essential to improve the sensitivity and reliability of the devices. As a result, the dynamic process of sorting and accurate positioning the nanoparticulate biomolecules within pre-defined micro/nanostructures is critical, however, it remains a huge hurdle for the realization of practical surface-sensitive biosensors and biochips. A scalable, massive, and non-destructive trapping methodology based on dielectrophoretic forces is highly demanded for assembling nanoparticles and biosensing tools. Herein, we propose a vertical nanogap architecture with an electrode-insulator-electrode stack structure, facilitating the generation of strong dielectrophoretic forces at low voltages, to precisely capture and spatiotemporally manipulate nanoparticles and molecular assemblies, including lipid vesicles and amyloid-beta protofibrils/oligomers. Our vertical nanogap platform, allowing low-voltage nanoparticle captures on optical metasurface designs, provides new opportunities for constructing advanced surface-sensitive optoelectronic sensors.
DOI
Toward the development of surface-sensitive analytical techniques for biosensors and diagnostic biochip assays, a local integration of low-concentration target materials into the sensing region of interest is essential to improve the sensitivity and reliability of the devices. As a result, the dynamic process of sorting and accurate positioning the nanoparticulate biomolecules within pre-defined micro/nanostructures is critical, however, it remains a huge hurdle for the realization of practical surface-sensitive biosensors and biochips. A scalable, massive, and non-destructive trapping methodology based on dielectrophoretic forces is highly demanded for assembling nanoparticles and biosensing tools. Herein, we propose a vertical nanogap architecture with an electrode-insulator-electrode stack structure, facilitating the generation of strong dielectrophoretic forces at low voltages, to precisely capture and spatiotemporally manipulate nanoparticles and molecular assemblies, including lipid vesicles and amyloid-beta protofibrils/oligomers. Our vertical nanogap platform, allowing low-voltage nanoparticle captures on optical metasurface designs, provides new opportunities for constructing advanced surface-sensitive optoelectronic sensors.
DOI
Large Submillimeter Assembly of Microparticles with Necklace-like Patterns Formed by Laser Trapping at Solution Surface
Jia-Syun Lu, Hsuan-Yin Wang, Tetsuhiro Kudo, and Hiroshi Masuhara
In colloidal solution, nanoparticles can be optically trapped by a tightly focused laser beam, and they are assembled in a focal spot whose diameter is typically about one micrometer. We herein report that a large submillimeter sized assembly of polystyrene microparticles with necklace-like patterns are prepared by laser trapping at a solution surface. The light propagation outside the focal spot is directly confirmed by 1064 nm backscattering images, and finite difference time domain simulation well supports the idea that an optical potential is expanded outside the focal spot based on light propagation through whispering gallery mode. This demonstration opens a new method for fabrication of a millimeter-order huge assembly by a single tightly focused laser beam.
DOI
In colloidal solution, nanoparticles can be optically trapped by a tightly focused laser beam, and they are assembled in a focal spot whose diameter is typically about one micrometer. We herein report that a large submillimeter sized assembly of polystyrene microparticles with necklace-like patterns are prepared by laser trapping at a solution surface. The light propagation outside the focal spot is directly confirmed by 1064 nm backscattering images, and finite difference time domain simulation well supports the idea that an optical potential is expanded outside the focal spot based on light propagation through whispering gallery mode. This demonstration opens a new method for fabrication of a millimeter-order huge assembly by a single tightly focused laser beam.
DOI
Specular-reflection photonic nanojet: physical basis and optical trapping application
I. V. Minin, Yu. E. Geints, A. A. Zemlyanov, and O. V. Minin
A specular-reflection photonic nanojet (s-PNJ) is a specific type of optical near-field subwavelength spatial localization originated from the constructive interference of direct and backward propagated optical waves focused by a transparent dielectric microparticle located near a flat reflecting mirror. The unique property of s-PNJ is reported for maintaining its spatial localization and high intensity when using microparticles with high refractive index contrast when a regular photonic nanojet is not formed. The physical principles of obtaining subwavelength optical focus in the specular-reflection mode of a PNJ are numerically studied and a comparative analysis of jet parameters obtained by the traditional schemes without and with reflection is carried out. Based on the s-PNJ, the physical concept of an optical tweezer integrated into the microfluidic device is proposed provided by the calculations of optical trapping forces of the trial gold nanosphere. Importantly, such an optical trap shows twice as high stability to Brownian motion of the captured nano-bead as compared to the conventional nanojet-based traps and can be relatively easy implemented.
DOI
A specular-reflection photonic nanojet (s-PNJ) is a specific type of optical near-field subwavelength spatial localization originated from the constructive interference of direct and backward propagated optical waves focused by a transparent dielectric microparticle located near a flat reflecting mirror. The unique property of s-PNJ is reported for maintaining its spatial localization and high intensity when using microparticles with high refractive index contrast when a regular photonic nanojet is not formed. The physical principles of obtaining subwavelength optical focus in the specular-reflection mode of a PNJ are numerically studied and a comparative analysis of jet parameters obtained by the traditional schemes without and with reflection is carried out. Based on the s-PNJ, the physical concept of an optical tweezer integrated into the microfluidic device is proposed provided by the calculations of optical trapping forces of the trial gold nanosphere. Importantly, such an optical trap shows twice as high stability to Brownian motion of the captured nano-bead as compared to the conventional nanojet-based traps and can be relatively easy implemented.
DOI
Monday, August 31, 2020
Molecular height measurement by cell surface optical profilometry (CSOP)
Sungmin Son, Sho C. Takatori, Brian Belardi, Marija Podolski, Matthew H. Bakalar, and Daniel A. Fletcher
The physical dimensions of proteins and glycans on cell surfaces can critically affect cell function, for example, by preventing close contact between cells and limiting receptor accessibility. However, high-resolution measurements of molecular heights on native cell membranes have been difficult to obtain. Here we present a simple and rapid method that achieves nanometer height resolution by localizing fluorophores at the tip and base of cell surface molecules and determining their separation by radially averaging across many molecules. We use this method, which we call cell surface optical profilometry (CSOP), to quantify the height of key multidomain proteins on a model cell, as well as to capture average protein and glycan heights on native cell membranes. We show that average height of a protein is significantly smaller than its contour length, due to thermally driven bending and rotation on the membrane, and that height strongly depends on local surface and solution conditions. We find that average height increases with cell surface molecular crowding but decreases with solution crowding by solutes, both of which we confirm with molecular dynamics simulations. We also use experiments and simulations to determine the height of an epitope, based on the location of an antibody, which allows CSOP to profile various proteins and glycans on a native cell surface using antibodies and lectins. This versatile method for profiling cell surfaces has the potential to advance understanding of the molecular landscape of cells and the role of the molecular landscape in cell function.
DOI
The physical dimensions of proteins and glycans on cell surfaces can critically affect cell function, for example, by preventing close contact between cells and limiting receptor accessibility. However, high-resolution measurements of molecular heights on native cell membranes have been difficult to obtain. Here we present a simple and rapid method that achieves nanometer height resolution by localizing fluorophores at the tip and base of cell surface molecules and determining their separation by radially averaging across many molecules. We use this method, which we call cell surface optical profilometry (CSOP), to quantify the height of key multidomain proteins on a model cell, as well as to capture average protein and glycan heights on native cell membranes. We show that average height of a protein is significantly smaller than its contour length, due to thermally driven bending and rotation on the membrane, and that height strongly depends on local surface and solution conditions. We find that average height increases with cell surface molecular crowding but decreases with solution crowding by solutes, both of which we confirm with molecular dynamics simulations. We also use experiments and simulations to determine the height of an epitope, based on the location of an antibody, which allows CSOP to profile various proteins and glycans on a native cell surface using antibodies and lectins. This versatile method for profiling cell surfaces has the potential to advance understanding of the molecular landscape of cells and the role of the molecular landscape in cell function.
DOI
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