1
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Zhou H, Jung W, Farhana TI, Fujimoto K, Kim T, Yokokawa R. Durability of Aligned Microtubules Dependent on Persistence Length Determines Phase Transition and Pattern Formation in Collective Motion. ACS NANO 2022; 16:14765-14778. [PMID: 36098647 DOI: 10.1021/acsnano.2c05593] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Collective motion is a ubiquitous phenomenon in nature. The collective motion of cytoskeleton filaments results mainly from dynamic collisions and alignments; however, the detailed mechanism of pattern formation still needs to be clarified. In particular, the influence of persistence length, which is a measure of filament flexibility, on collective motion is still unclear and lacks experimental verifications although it is likely to directly affect the orientational flexibility of filaments. Here, we investigated the collective motion of microtubules with different persistence lengths using a microtubule-kinesin motility system. We showed that local interactions between microtubules significantly vary depending on their persistence length. We demonstrated that the bundling of microtubules is enhanced by more durable alignment, rather than by greater likelihood of alignment. An agent-based computational model confirmed that the rigidity-dependent durability of microtubule alignment dominates their collective behavior.
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Affiliation(s)
- Hang Zhou
- Department of Micro Engineering, Kyoto University, Kyoto daigaku-katsura, Nishikyo-ku, Kyoto 615-8540, Japan
| | - Wonyeong Jung
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana 47907, United States
| | - Tamanna Ishrat Farhana
- Department of Micro Engineering, Kyoto University, Kyoto daigaku-katsura, Nishikyo-ku, Kyoto 615-8540, Japan
| | - Kazuya Fujimoto
- Department of Micro Engineering, Kyoto University, Kyoto daigaku-katsura, Nishikyo-ku, Kyoto 615-8540, Japan
| | - Taeyoon Kim
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana 47907, United States
| | - Ryuji Yokokawa
- Department of Micro Engineering, Kyoto University, Kyoto daigaku-katsura, Nishikyo-ku, Kyoto 615-8540, Japan
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2
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Soppina P, Patel N, Shewale DJ, Rai A, Sivaramakrishnan S, Naik PK, Soppina V. Kinesin-3 motors are fine-tuned at the molecular level to endow distinct mechanical outputs. BMC Biol 2022; 20:177. [PMID: 35948971 PMCID: PMC9364601 DOI: 10.1186/s12915-022-01370-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2022] [Accepted: 07/06/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Kinesin-3 family motors drive diverse cellular processes and have significant clinical importance. The ATPase cycle is integral to the processive motility of kinesin motors to drive long-distance intracellular transport. Our previous work has demonstrated that kinesin-3 motors are fast and superprocessive with high microtubule affinity. However, chemomechanics of these motors remain poorly understood. RESULTS We purified kinesin-3 motors using the Sf9-baculovirus expression system and demonstrated that their motility properties are on par with the motors expressed in mammalian cells. Using biochemical analysis, we show for the first time that kinesin-3 motors exhibited high ATP turnover rates, which is 1.3- to threefold higher compared to the well-studied kinesin-1 motor. Remarkably, these ATPase rates correlate to their stepping rate, suggesting a tight coupling between chemical and mechanical cycles. Intriguingly, kinesin-3 velocities (KIF1A > KIF13A > KIF13B > KIF16B) show an inverse correlation with their microtubule-binding affinities (KIF1A < KIF13A < KIF13B < KIF16B). We demonstrate that this differential microtubule-binding affinity is largely contributed by the positively charged residues in loop8 of the kinesin-3 motor domain. Furthermore, microtubule gliding and cellular expression studies displayed significant microtubule bending that is influenced by the positively charged insert in the motor domain, K-loop, a hallmark of kinesin-3 family. CONCLUSIONS Together, we propose that a fine balance between the rate of ATP hydrolysis and microtubule affinity endows kinesin-3 motors with distinct mechanical outputs. The K-loop, a positively charged insert in the loop12 of the kinesin-3 motor domain promotes microtubule bending, an interesting phenomenon often observed in cells, which requires further investigation to understand its cellular and physiological significance.
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Affiliation(s)
- Pushpanjali Soppina
- Discipline of Biological Engineering, Indian Institute of Technology Gandhinagar, Gandhinagar, Gujarat, 382355, India.,Department of Biotechnology and Bioinformatics, Sambalpur University, Sambalpur, Orissa, 768019, India
| | - Nishaben Patel
- Discipline of Biological Engineering, Indian Institute of Technology Gandhinagar, Gandhinagar, Gujarat, 382355, India.,Department of Genetics, Cell Biology and Development, University of Minnesota, Minnesota, MN, 55455, USA
| | - Dipeshwari J Shewale
- Discipline of Biological Engineering, Indian Institute of Technology Gandhinagar, Gandhinagar, Gujarat, 382355, India
| | - Ashim Rai
- Department of Genetics, Cell Biology and Development, University of Minnesota, Minnesota, MN, 55455, USA
| | - Sivaraj Sivaramakrishnan
- Department of Genetics, Cell Biology and Development, University of Minnesota, Minnesota, MN, 55455, USA
| | - Pradeep K Naik
- Department of Biotechnology and Bioinformatics, Sambalpur University, Sambalpur, Orissa, 768019, India
| | - Virupakshi Soppina
- Discipline of Biological Engineering, Indian Institute of Technology Gandhinagar, Gandhinagar, Gujarat, 382355, India.
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3
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Unksov IN, Korosec CS, Surendiran P, Verardo D, Lyttleton R, Forde NR, Linke H. Through the Eyes of Creators: Observing Artificial Molecular Motors. ACS NANOSCIENCE AU 2022; 2:140-159. [PMID: 35726277 PMCID: PMC9204826 DOI: 10.1021/acsnanoscienceau.1c00041] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/13/2021] [Revised: 12/20/2021] [Accepted: 12/20/2021] [Indexed: 11/28/2022]
Abstract
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Inspired by molecular
motors in biology, there has been significant
progress in building artificial molecular motors, using a number of
quite distinct approaches. As the constructs become more sophisticated,
there is also an increasing need to directly observe the motion of
artificial motors at the nanoscale and to characterize their performance.
Here, we review the most used methods that tackle those tasks. We
aim to help experimentalists with an overview of the available tools
used for different types of synthetic motors and to choose the method
most suited for the size of a motor and the desired measurements,
such as the generated force or distances in the moving system. Furthermore,
for many envisioned applications of synthetic motors, it will be a
requirement to guide and control directed motions. We therefore also
provide a perspective on how motors can be observed on structures
that allow for directional guidance, such as nanowires and microchannels.
Thus, this Review facilitates the future research on synthetic molecular
motors, where observations at a single-motor level and a detailed
characterization of motion will promote applications.
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Affiliation(s)
- Ivan N. Unksov
- Solid State Physics and NanoLund, Lund University, Box 118, SE-221 00 Lund, Sweden
| | - Chapin S. Korosec
- Department of Physics, Simon Fraser University, V5A 1S6 Burnaby, British Columbia, Canada
| | | | - Damiano Verardo
- Solid State Physics and NanoLund, Lund University, Box 118, SE-221 00 Lund, Sweden
- AlignedBio AB, Medicon Village, Scheeletorget 1, 223 63 Lund, Sweden
| | - Roman Lyttleton
- Solid State Physics and NanoLund, Lund University, Box 118, SE-221 00 Lund, Sweden
| | - Nancy R. Forde
- Department of Physics, Simon Fraser University, V5A 1S6 Burnaby, British Columbia, Canada
| | - Heiner Linke
- Solid State Physics and NanoLund, Lund University, Box 118, SE-221 00 Lund, Sweden
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4
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Hydrothermal Synthesis of β-Nb 2ZnO 6 Nanoparticles for Photocatalytic Degradation of Methyl Orange and Cytotoxicity Study. Int J Mol Sci 2022; 23:ijms23094777. [PMID: 35563173 PMCID: PMC9105501 DOI: 10.3390/ijms23094777] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2022] [Revised: 04/05/2022] [Accepted: 04/24/2022] [Indexed: 02/01/2023] Open
Abstract
β-Nb2ZnO6 nanoparticles were synthesized by a hydrothermal process and calcined at two temperatures, 500 °C and 700 °C, and assigned as A and B, respectively. X-ray diffraction, together with transmission electron microscopy, revealed that the β-Nb2ZnO6 nanoparticles calcined at 700 °C (B) were more crystalline than the β-Nb2ZnO6 calcined at 500 °C (A) with both types of nanoparticles having an average size of approximately 100 nm. The physiochemical, photocatalytic, and cytotoxic activities of both types of β-Nb2ZnO6 nanoparticles (A and B) were examined. Interestingly, the photodegradation of methyl orange, used as a standard for environmental pollutants, was faster in the presence of the β-Nb2ZnO6 nanoparticles calcined at 500 °C (A) than in the presence of those calcined at 700 °C (B). Moreover, the cytotoxicity was evaluated against different types of cancer cells and the results indicated that both types of β-Nb2ZnO6 nanoparticles (A and B) exhibited high cytotoxicity against MCF-7 and HCT116 cells but low cytotoxicity against HeLa cells after 24 and 48 h of treatment. Overall, both products expressed similar EC50 values on tested cell lines and high cytotoxicity after 72 h of treatment. As a photocatalyst, β-Nb2ZnO6 nanoparticles (A) could be utilized in different applications including the purification of the environment and water from specific pollutants. Further biological studies are required to determine the other potential impacts of utilizing β-Nb2ZnO6 nanoparticles in the biomedical application field.
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5
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VanDelinder V, Bachand GD. Characterizing the Number of Kinesin Motors Bound to Microtubules in the Gliding Motility Assay Using FLIC Microscopy. Methods Mol Biol 2022; 2430:93-104. [PMID: 35476327 DOI: 10.1007/978-1-0716-1983-4_6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Intracellular transport by kinesin motors moving along their associated cytoskeletal filaments, microtubules, is essential to many biological processes. This active transport system can be reconstituted in vitro with the surface-adhered motors transporting the microtubules across a planar surface. In this geometry, the kinesin-microtubule system has been used to study active self-assembly, to power microdevices, and to perform analyte detection. Fundamental to these applications is the ability to characterize the interactions between the surface tethered motors and microtubules. Fluorescence Interference Contrast (FLIC) microscopy can illuminate the height of the microtubule above a surface, which, at sufficiently low surface densities of kinesin, also reveals the number, locations, and dynamics of the bound motors.
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Affiliation(s)
- Virginia VanDelinder
- Center for Integrated Nanotechnologies, Sandia National Laboratories, Albuquerque, NM, Mexico
| | - George D Bachand
- Center for Integrated Nanotechnologies, Sandia National Laboratories, Albuquerque, NM, Mexico.
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6
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Tsitkov S, Song Y, Rodriguez JB, Zhang Y, Hess H. Kinesin-Recruiting Microtubules Exhibit Collective Gliding Motion while Forming Motor Trails. ACS NANO 2020; 14:16547-16557. [PMID: 33054177 DOI: 10.1021/acsnano.0c03263] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Microtubules gliding on surfaces coated with kinesin motors are minimalist experimental systems for studying collective behavior. Collective behavior in these systems arises from interactions between filaments, for example, from steric interactions, depletion forces, or cross-links. To maximize the utilization of system components and the production of work, it is desirable to achieve mutualistic interactions leading to the congregations of both types of agents, that is, cytoskeletal filaments and molecular motors. To this end, we used a microtubule-kinesin system, where motors reversibly bind to the surface via an interaction between a hexahistidine (His6) tag on the motor and a Ni(II)-nitrilotriacetic acid (Ni-NTA) moiety on the surface. The surface density of binding sites for kinesin motors was increased relative to our earlier work, driving the motors from the solution to the surface. Characterization of the motor-surface interactions in the absence of microtubules yielded kinetic parameters consistent with previous data and revealed the capacity of the surface to support two-dimensional motor diffusion. The motor density gradually fell over 2 h, presumably due to the stripping of Ni(II) from the NTA moieties on the surface. Microtubules gliding on these reversibly bound motors were unable to cross each other and at high enough densities began to align and form long, dense bundles. The kinesin motors accumulated in trails surrounding the microtubule bundles and participated in microtubule transport.
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Affiliation(s)
- Stanislav Tsitkov
- Department of Biomedical Engineering, Columbia University, New York, New York 10027, United States
| | - Yuchen Song
- Department of Biomedical Engineering, Columbia University, New York, New York 10027, United States
- Department of Biomedical Engineering, Hong Kong Polytechnic University, Hong Kong SAR, China
| | - Juan B Rodriguez
- Department of Biomedical Engineering, Columbia University, New York, New York 10027, United States
| | - Yifei Zhang
- Department of Biomedical Engineering, Columbia University, New York, New York 10027, United States
| | - Henry Hess
- Department of Biomedical Engineering, Columbia University, New York, New York 10027, United States
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7
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Martinez H, Martinez NJD, Guo J, Lujan VR, Depoy J, Brumbach MT, Brinker CJ, Bachand GD. Effects of Surface Chemistry and Topology on the Kinesin-Driven Motility of Microtubule Shuttles. ACS APPLIED BIO MATERIALS 2020; 3:7908-7918. [DOI: 10.1021/acsabm.0c01035] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Affiliation(s)
- Haneen Martinez
- Sandia National Laboratories, Albuquerque, New Mexico 87185, United States
| | | | - Jimin Guo
- Department of Chemical and Biological Engineering, University of New Mexico, Albuquerque, New Mexico 87131, United States
| | - Victoria R. Lujan
- Sandia National Laboratories, Albuquerque, New Mexico 87185, United States
| | - Jessica Depoy
- Sandia National Laboratories, Albuquerque, New Mexico 87185, United States
| | | | - C. Jeffrey Brinker
- Sandia National Laboratories, Albuquerque, New Mexico 87185, United States
- Department of Chemical and Biological Engineering, University of New Mexico, Albuquerque, New Mexico 87131, United States
| | - George D. Bachand
- Sandia National Laboratories, Albuquerque, New Mexico 87185, United States
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8
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Bassir Kazeruni NM, Rodriguez JB, Saper G, Hess H. Microtubule Detachment in Gliding Motility Assays Limits the Performance of Kinesin-Driven Molecular Shuttles. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:7901-7907. [PMID: 32551689 DOI: 10.1021/acs.langmuir.0c01002] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The creation of complex active nanosystems integrating cytoskeletal filaments propelled by surface-adhered motor proteins often relies on the filaments' ability to glide over up to meter-long distances. While theoretical considerations support this ability, we show that microtubule detachment (either spontaneous or triggered by a microtubule crossing event) is a non-negligible phenomenon that has been overlooked until now. The average gliding distance before spontaneous detachment was measured to be 30 ± 10 mm for a functional kinesin-1 density of 500 μm-2 and 9 ± 4 mm for a functional kinesin-1 density of 100 μm-2 at 1 mM ATP. Even microtubules longer than 3 μm detached, suggesting that spontaneous detachment is not caused by the stochastic absence of motors or their stochastic release due to a limited run length.
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Affiliation(s)
- Neda M Bassir Kazeruni
- Columbia University, 351L Engineering Terrace, MC 8904 1210 Amsterdam Avenue, New York, New York 10027, United States
| | - Juan B Rodriguez
- Columbia University, 351L Engineering Terrace, MC 8904 1210 Amsterdam Avenue, New York, New York 10027, United States
| | - Gadiel Saper
- Columbia University, 351L Engineering Terrace, MC 8904 1210 Amsterdam Avenue, New York, New York 10027, United States
| | - Henry Hess
- Columbia University, 351L Engineering Terrace, MC 8904 1210 Amsterdam Avenue, New York, New York 10027, United States
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9
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Affiliation(s)
- Gadiel Saper
- Department of Biomedical Engineering, Columbia University, New York, New York 10027, United States
| | - Henry Hess
- Department of Biomedical Engineering, Columbia University, New York, New York 10027, United States
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10
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Fluorescence Interference Contrast-enabled structures improve the microarrays performance. Biosens Bioelectron 2019; 123:251-259. [PMID: 30224286 DOI: 10.1016/j.bios.2018.09.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2018] [Revised: 08/18/2018] [Accepted: 09/01/2018] [Indexed: 11/22/2022]
Abstract
Continuous improvements of the fluorescence-based sensitivity and specificity, required for high throughput screening, diagnostics, and molecular biology studies, are usually addressed by better readout systems, or better reporting elements. However, while Fluorescence Interference Contrast (FLIC), which modulates the fluorescence by materials-based parameters, has been used for decades to measure biomolecular interactions at nanometer-precision, e.g., for the study of molecular motors and membrane processes, it has been seldom used for high throughput or diagnostic microdevices. Moreover, the amplification of both the fluorescence signal, modulated by vertically-nano-calibrated structures, and the signal/background, modulated by laterally-micro-calibrated structures, has not been explored. To address this synergy, structures comprising optically transparent silicon oxide, tens of micrometers-wide and with thicknesses in the low hundreds of nanometers, which are able to promote the formation of standing waves if patterned on a reflective material, have been designed, fabricated and tested, for the use in DNA- and protein arrays. The light emitted by a fluorophore placed on top of the structures and reflected by a bottom mirror surface, e.g., silicon, platinum, is physically constrained to a region defined lithographically, both vertically and laterally, i.e., micro-pillars and -wells, resulting in an accurate identification and quantification of fluorescence. The signal/noise ratio on micro-/nano-structured substrates is comparable to that measured on planar substrates, but the physical confinement of the microarray spots results in a considerable increase of the intra-feature uniformity.
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11
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Biological active matter aggregates: Inspiration for smart colloidal materials. Adv Colloid Interface Sci 2019; 263:38-51. [PMID: 30504078 DOI: 10.1016/j.cis.2018.11.006] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Revised: 11/02/2018] [Accepted: 11/20/2018] [Indexed: 12/16/2022]
Abstract
Aggregations of social organisms exhibit a remarkable range of properties and functionalities. Multiple examples, such as fire ants or slime mold, show how a population of individuals is able to overcome an existential threat by gathering into a solid-like aggregate with emergent functionality. Surprisingly, these aggregates are driven by simple rules, and their mechanisms show great parallelism among species. At the same time, great effort has been made by the scientific community to develop active colloidal materials, such as microbubbles or Janus particles, which exhibit similar behaviors. However, a direct connection between these two realms is still not evident, and it would greatly benefit future studies. In this review, we first discuss the current understanding of living aggregates, point out the mechanisms in their formation and explore the vast range of emergent properties. Second, we review the current knowledge in aggregated colloidal systems, the methods used to achieve the aggregations and their potential functionalities. Based on this knowledge, we finally identify a set of over-arching principles commonly found in biological aggregations, and further suggest potential future directions for the creation of bio-inspired colloid aggregations.
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12
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Fujimoto K, Morita Y, Iino R, Tomishige M, Shintaku H, Kotera H, Yokokawa R. Simultaneous Observation of Kinesin-Driven Microtubule Motility and Binding of Adenosine Triphosphate Using Linear Zero-Mode Waveguides. ACS NANO 2018; 12:11975-11985. [PMID: 30418736 DOI: 10.1021/acsnano.8b03803] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Single-molecule fluorescence observation of adenosine triphosphate (ATP) is a powerful tool to elucidate the chemomechanical coupling of ATP with a motor protein. However, in total internal reflection fluorescence microscopy (TIRFM), available ATP concentration is much lower than that in the in vivo environment. To achieve single-molecule observation with a high signal-to-noise ratio, zero-mode waveguides (ZMWs) are utilized even at high fluorescent molecule concentrations in the micromolar range. Despite the advantages of ZMWs, the use of cytoskeletal filaments for single-molecule observation has not been reported because of difficulties in immobilization of cytoskeletal filaments in the cylindrical aperture of ZMWs. Here, we propose linear ZMWs (LZMWs) to visualize enzymatic reactions on cytoskeletal filaments, specifically kinesin-driven microtubule motility accompanied by ATP binding/unbinding. Finite element method simulation revealed excitation light confinement in a 100 nm wide slit of LZMWs. Single-molecule observation was then demonstrated with up to 1 μM labeled ATP, which was 10-fold higher than that available in TIRFM. Direct observation of binding/unbinding of ATP to kinesins that propel microtubules enabled us to find that a significant fraction of ATP molecules bound to kinesins were dissociated without hydrolysis. This highlights the advantages of LZMWs for single-molecule observation of proteins that interact with cytoskeletal filaments such as microtubules, actin filaments, or intermediate filaments.
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Affiliation(s)
- Kazuya Fujimoto
- Department of Micro Engineering , Kyoto University , Kyoto 615-8540 , Japan
| | - Yuki Morita
- Department of Micro Engineering , Kyoto University , Kyoto 615-8540 , Japan
| | - Ryota Iino
- Institute for Molecular Science , National Institutes of Natural Sciences , Okazaki , Aichi 444-8787 , Japan
| | - Michio Tomishige
- College of Science and Engineering , Aoyama Gakuin University , Kanagawa 252-5258 , Japan
| | - Hirofumi Shintaku
- Department of Micro Engineering , Kyoto University , Kyoto 615-8540 , Japan
| | - Hidetoshi Kotera
- Department of Micro Engineering , Kyoto University , Kyoto 615-8540 , Japan
| | - Ryuji Yokokawa
- Department of Micro Engineering , Kyoto University , Kyoto 615-8540 , Japan
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13
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Abstract
Biomolecular motors, such as the motor protein kinesin, can be used as off-the-shelf components to power hybrid nanosystems. These hybrid systems combine elements from the biological and synthetic toolbox of the nanoengineer and can be used to explore the applications and design principles of active nanosystems. Efforts to advance nanoscale engineering benefit greatly from biological and biophysical research into the operating principles of motor proteins and their biological roles. In return, the process of creating in vitro systems outside of the context of biology can lead to an improved understanding of the physical constraints creating the fitness landscape explored by evolution. However, our main focus is a holistic understanding of the engineering principles applying to systems integrating molecular motors in general. To advance this goal, we and other researchers have designed biomolecular motor-powered nanodevices, which sense, compute, and actuate. In addition to demonstrating that biological solutions can be mimicked in vitro, these devices often demonstrate new paradigms without parallels in current technology. Long-term trends in technology toward the deployment of ever smaller and more numerous motors and computers give us confidence that our work will become increasingly relevant. Here, our discussion aims to step back and look at the big picture. From our perspective, energy efficiency is a key and underappreciated metric in the design of synthetic motors. On the basis of an analogy to ecological principles, we submit that practical molecular motors have to have energy conversion efficiencies of more than 10%, a threshold only exceeded by motor proteins. We also believe that motor and system lifetime is a critical metric and an important topic of investigation. Related questions are if future molecular motors, by necessity, will resemble biomolecular motors in their softness and fragility and have to conform to the "universal performance characteristics of motors", linking the maximum force and mass of any motor, identified by Marden and Allen. The utilization of molecular motors for computing devices emphasizes the interesting relationship among the conversion of energy, extraction of work, and production of information. Our recent work touches upon these topics and discusses molecular clocks as well as a Landauer limit for robotics. What is on the horizon? Just as photovoltaics took advantage of progress in semiconductor fabrication to become commercially viable over a century, one can envision that engineers working with biomolecular motors leverage progress in biotechnology and drug development to create the engines of the future. However, the future source of energy is going to be electricity rather than fossil or biological fuels, a fact that has to be accounted for in our future efforts. In summary, we are convinced that past, ongoing, and future efforts to engineer with biomolecular motors are providing exciting demonstrations and fundamental insights as well as opportunities to wander freely across the borders of engineering, biology, and chemistry.
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Affiliation(s)
- Henry Hess
- Department of Biomedical Engineering, Columbia University, New York, New York 10027, United States
| | - Gadiel Saper
- Department of Biomedical Engineering, Columbia University, New York, New York 10027, United States
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14
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Chaudhuri S, Korten T, Korten S, Milani G, Lana T, Te Kronnie G, Diez S. Label-Free Detection of Microvesicles and Proteins by the Bundling of Gliding Microtubules. NANO LETTERS 2018; 18:117-123. [PMID: 29202578 DOI: 10.1021/acs.nanolett.7b03619] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Development of miniaturized devices for the rapid and sensitive detection of analyte is crucial for various applications across healthcare, pharmaceutical, environmental, and other industries. Here, we report on the detection of unlabeled analyte by using fluorescently labeled, antibody-conjugated microtubules in a kinesin-1 gliding motility assay. The detection principle is based on the formation of fluorescent supramolecular assemblies of microtubule bundles and spools in the presence of multivalent analytes. We demonstrate the rapid, label-free detection of CD45+ microvesicles derived from leukemia cells. Moreover, we employ our platform for the label-free detection of multivalent proteins at subnanomolar concentrations, as well as for profiling the cross-reactivity between commercially available secondary antibodies. As the detection principle is based on the molecular recognition between antigen and antibody, our method can find general application where it identifies any analyte, including clinically relevant microvesicles and proteins.
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Affiliation(s)
- Samata Chaudhuri
- B CUBE - Center for Molecular Bioengineering, TU Dresden , 01069 Dresden, Germany
- Max Planck Institute of Molecular Cell Biology and Genetics , 01307 Dresden, Germany
| | - Till Korten
- B CUBE - Center for Molecular Bioengineering, TU Dresden , 01069 Dresden, Germany
- Max Planck Institute of Molecular Cell Biology and Genetics , 01307 Dresden, Germany
| | - Slobodanka Korten
- B CUBE - Center for Molecular Bioengineering, TU Dresden , 01069 Dresden, Germany
- Max Planck Institute of Molecular Cell Biology and Genetics , 01307 Dresden, Germany
| | - Gloria Milani
- Department of Women's and Children's Health, University of Padova , 35128 Padova, Italy
| | - Tobia Lana
- Department of Women's and Children's Health, University of Padova , 35128 Padova, Italy
| | - Geertruy Te Kronnie
- Department of Women's and Children's Health, University of Padova , 35128 Padova, Italy
| | - Stefan Diez
- B CUBE - Center for Molecular Bioengineering, TU Dresden , 01069 Dresden, Germany
- Max Planck Institute of Molecular Cell Biology and Genetics , 01307 Dresden, Germany
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15
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Hess H, Ross JL. Non-equilibrium assembly of microtubules: from molecules to autonomous chemical robots. Chem Soc Rev 2017; 46:5570-5587. [PMID: 28329028 PMCID: PMC5603359 DOI: 10.1039/c7cs00030h] [Citation(s) in RCA: 131] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Biological systems have evolved to harness non-equilibrium processes from the molecular to the macro scale. It is currently a grand challenge of chemistry, materials science, and engineering to understand and mimic biological systems that have the ability to autonomously sense stimuli, process these inputs, and respond by performing mechanical work. New chemical systems are responding to the challenge and form the basis for future responsive, adaptive, and active materials. In this article, we describe a particular biochemical-biomechanical network based on the microtubule cytoskeletal filament - itself a non-equilibrium chemical system. We trace the non-equilibrium aspects of the system from molecules to networks and describe how the cell uses this system to perform active work in essential processes. Finally, we discuss how microtubule-based engineered systems can serve as testbeds for autonomous chemical robots composed of biological and synthetic components.
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Affiliation(s)
- H Hess
- Department of Biomedical Engineering, Columbia University, USA.
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Transport efficiency of membrane-anchored kinesin-1 motors depends on motor density and diffusivity. Proc Natl Acad Sci U S A 2016; 113:E7185-E7193. [PMID: 27803325 DOI: 10.1073/pnas.1611398113] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
In eukaryotic cells, membranous vesicles and organelles are transported by ensembles of motor proteins. These motors, such as kinesin-1, have been well characterized in vitro as single molecules or as ensembles rigidly attached to nonbiological substrates. However, the collective transport by membrane-anchored motors, that is, motors attached to a fluid lipid bilayer, is poorly understood. Here, we investigate the influence of motors' anchorage to a lipid bilayer on the collective transport characteristics. We reconstituted "membrane-anchored" gliding motility assays using truncated kinesin-1 motors with a streptavidin-binding peptide tag that can attach to streptavidin-loaded, supported lipid bilayers. We found that the diffusing kinesin-1 motors propelled the microtubules in the presence of ATP. Notably, we found the gliding velocity of the microtubules to be strongly dependent on the number of motors and their diffusivity in the lipid bilayer. The microtubule gliding velocity increased with increasing motor density and membrane viscosity, reaching up to the stepping velocity of single motors. This finding is in contrast to conventional gliding motility assays where the density of surface-immobilized kinesin-1 motors does not influence the microtubule velocity over a wide range. We reason that the transport efficiency of membrane-anchored motors is reduced because of their slippage in the lipid bilayer, an effect that we directly observed using single-molecule fluorescence microscopy. Our results illustrate the importance of motor-cargo coupling, which potentially provides cells with an additional means of regulating the efficiency of cargo transport.
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Lu T, Wang L, Jiang Y, Liu Q, Huang C. Hexagonal boron nitride nanoplates as emerging biological nanovectors and their potential applications in biomedicine. J Mater Chem B 2016; 4:6103-6110. [PMID: 32263498 DOI: 10.1039/c6tb01481j] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The application of nanomaterials in the biological and medical areas has attracted great attention. Cytotoxicity, stability and solubility are the prerequisites for a nanomaterial to be considered for application in the field of biomedicine. Here, we suggest a simple method to produce highly dispersed water-soluble ultrathin h-BN nanoplates whose size measures ca. 30-60 nm in diameter and 1.6 nm in thickness. Moreover, we demonstrate that h-BN nanoplates can act as a reliable biological nanovector to carry proteins by cross-linking immobilization. Furthermore, the biocompatibility of h-BN nanoplates has also been explored via an apoptosis assay. In addition, a successful attempt has been made to investigate the potency of h-BN nanoplates as an immunostimulating adjuvant in a mouse immunization experiment. Preliminary results show that the level of antibody response stimulated by an antigen protein (bovine serum albumin) linked with h-BN is ca. 4 times higher than that by the antigen protein alone. This work gives evidence that water-soluble h-BN nanoplates are of high biocompatibility and low reactogenicity and therefore they can serve as an excellent biomedical platform for nanoparticle-biomolecular interactions. They preserve and even enhance the bioacitivities of the cross-linked antigen proteins, which strongly suggests their use in nanoparticle vaccine design.
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Affiliation(s)
- Tun Lu
- College of Biological Science and Engineering, Fuzhou University, Fuzhou 350002, China
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18
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Ishigure Y, Nitta T. Simulating an Actomyosin in Vitro Motility Assay: Toward the Rational Design of Actomyosin-Based Microtransporters. IEEE Trans Nanobioscience 2015; 14:641-8. [PMID: 26087497 DOI: 10.1109/tnb.2015.2443373] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
We present a simulation study of an actomyosin in vitro motility assay. In vitro motility assays have served as an essential element facilitating the application of actomyosin in nanotechnology; such applications include biosensors and biocomputation. Although actomyosin in vitro motility assays have been extensively investigated, some ambiguities remain, as a result of the limited spatio-temporal resolution and unavoidable uncertainties associated with the experimental process. These ambiguities hamper the rational design of nanodevices for practical applications. Here, with the aim of moving toward a rational design process, we developed a 3D computer simulation method of an actomyosin in vitro motility assay, based on a Brownian dynamics simulation. The simulation explicitly included the ATP hydrolysis cycle of myosin. The simulation was validated by the reproduction of previous experimental results. More importantly, the simulation provided new insights that are difficult to obtain experimentally, including data on the number of myosin motors actually binding to actin filaments, the mechanism responsible for the guiding of actin filaments by chemical edges, and the effect of the processivity of motor proteins on the guiding probabilities. The simulations presented here will be useful in interpreting experimental results, and also in designing future nanodevices integrated with myosin motors.
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Ishigure Y, Nitta T. Understanding the guiding of kinesin/microtubule-based microtransporters in microfabricated tracks. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:12089-12096. [PMID: 25238638 DOI: 10.1021/la5021884] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Microtransporters using cargo-laden microtubules propelled by kinesin motors are attractive for numerous applications in nanotechnology. To improve the efficiency of transport, the movement of microtubules must be guided by microfabricated tracks. However, the mechanisms of the guiding methods used are not fully understood. Here, using computer simulation, we systematically studied the guiding of such microtransporters by three different types of guiding methods: a chemical boundary, a physical barrier, and their combination. The simulation reproduced the probabilities of guiding previously observed experimentally for the three methods. Moreover, the simulation provided further insight into the mechanisms of guiding, which overturn previous assumptions and models.
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Affiliation(s)
- Yuki Ishigure
- Department of Mathematical Design and Engineering and ‡Applied Physics Course, Gifu University , Gifu 501-1193, Japan
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20
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Steuerwald D, Früh SM, Griss R, Lovchik RD, Vogel V. Nanoshuttles propelled by motor proteins sequentially assemble molecular cargo in a microfluidic device. LAB ON A CHIP 2014; 14:3729-3738. [PMID: 25008788 DOI: 10.1039/c4lc00385c] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Nanoshuttles powered by the molecular motor kinesin have the potential to capture and concentrate rare molecules from solution as well as to transport, sort and assemble them in a high-throughput manner. One long-thought-of goal has been the realisation of a molecular assembly line with nanoshuttles as workhorses. To harness them for this purpose might allow the community to engineer novel materials and nanodevices. The central milestone towards this goal is to expose nanoshuttles to a series of different molecules or building blocks and load them sequentially to build hierarchical structures, macromolecules or materials. Here, we addressed this challenge by exploiting the synergy of two so far mostly complementary techniques, nanoshuttle-mediated active transport and pressure-driven passive transport, integrated into a single microfluidic device to demonstrate the realisation of a molecular assembly line. Multiple step protocols can thus be miniaturised to a highly parallelised and autonomous working lab-on-a-chip: in each reaction chamber, analytes or building blocks are captured from solution and are then transported by nanoshuttles across fluid flow boundaries in the next chamber. Cargo can thus be assembled, modified, analysed and eventually unloaded in a procedure that requires only one step by its operator.
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Affiliation(s)
- Dirk Steuerwald
- Laboratory of Applied Mechanobiology, Department of Health Sciences and Technology, ETH Zürich, 8093 Zürich, Switzerland.
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21
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Kerssemakers JWJ, Blosser TR, Dekker C. A simple self-calibrating method to measure the height of fluorescent molecules and beads at nanoscale resolution. NANO LETTERS 2014; 14:4469-4475. [PMID: 25014485 DOI: 10.1021/nl501434v] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We describe a simple self-calibrating technique, incident-beam interference sweeping, for measuring the height of fluorescent labels. Using a tilted back-reflecting mirror and a scanning laser beam, a modulated fluorescence emission allows height determination of a label from a surface with a resolution of ∼ 3 nm. In addition, we show that the absolute distance of a label from the top-mounted mirror can be determined with a resolution of a few tens of nanometers over a micrometer range.
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Affiliation(s)
- Jacob W J Kerssemakers
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology , Lorentzweg 1, 2628 CJ Delft, The Netherlands
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22
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Dumont ELP, Belmas H, Hess H. Observing the mushroom-to-brush transition for kinesin proteins. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:15142-5. [PMID: 24266641 DOI: 10.1021/la4030712] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
The height of polymers grafted to a surface is predicted to be constant at low densities ("mushroom" regime) and increase with the third root of the polymer surface density at high densities ("brush" regime). This mushroom-to-brush transition is explored with kinesin-1 proteins adhered to a surface at controlled densities. The kinesin height is measured by attaching fluorescently labeled microtubules to the kinesins and determining their elevation using fluorescence interference contrast microscopy. Our measurements are consistent with a mushroom regime and a brush regime and a transition near the theoretically predicted density. The mushroom-to-brush transition may play a role in protein behavior in crowded cellular environments and may be exploited as a signal in intracellular regulation and mechanotransduction.
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Affiliation(s)
- Emmanuel L P Dumont
- Department of Biomedical Engineering, Columbia University , 1210 Amsterdam Avenue, New York, New York 10027, United States
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23
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Mojarad N, Sandoghdar V, Krishnan M. Measuring three-dimensional interaction potentials using optical interference. OPTICS EXPRESS 2013; 21:9377-9389. [PMID: 23609648 DOI: 10.1364/oe.21.009377] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We describe the application of three-dimensional (3D) scattering interferometric (iSCAT) imaging to the measurement of spatial interaction potentials for nano-objects in solution. We study electrostatically trapped gold particles in a nanofluidic device and present details on axial particle localization in the presence of a strongly reflecting interface. Our results demonstrate high-speed (~kHz) particle tracking with subnanometer localization precision in the axial and average 2.5 nm in the lateral dimension. A comparison of the measured levitation heights of trapped particles with the calculated values for traps of various geometries reveals good agreement. Our work demonstrates that iSCAT imaging delivers label-free, high-speed and accurate 3D tracking of nano-objects conducive to probing weak and long-range interaction potentials in solution.
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Affiliation(s)
- Nassir Mojarad
- Laboratory for Micro- and Nanotechnology, Paul Scherrer Institut, 5232 Villigen, Switzerland
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Agayan RR, Tucker R, Nitta T, Ruhnow F, Walter WJ, Diez S, Hess H. Optimization of isopolar microtubule arrays. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:2265-2272. [PMID: 23330965 DOI: 10.1021/la303792v] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Isopolar arrays of aligned cytoskeletal filaments are components in a number of designs of hybrid nanodevices incorporating biomolecular motors. For example, a combination of filament arrays and motor arrays can form an actuator or a molecular engine resembling an artificial muscle. Here, isopolar arrays of microtubules are fabricated by flow alignment, and their quality is characterized by their degree of alignment. We find, in agreement with our analytical models, that the degree of alignment is ultimately limited by thermal forces, while the kinetics of the alignment process are influenced by the flow strength, the microtubule stiffness, the gliding velocity, and the tip length. Strong flows remove microtubules from the surface and reduce the filament density, suggesting that there is an optimal flow strength for the fabrication of ordered arrays.
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Affiliation(s)
- Rodney R Agayan
- Department of Biomedical Engineering, Columbia University, New York, New York 10027, United States
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25
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Effect of Path Persistence Length of Molecular Shuttles on Two-stage Analyte Capture in Biosensors. Cell Mol Bioeng 2012. [DOI: 10.1007/s12195-012-0262-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
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26
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Düselder A, Thiede C, Schmidt CF, Lakämper S. Neck-linker length dependence of processive Kinesin-5 motility. J Mol Biol 2012; 423:159-68. [PMID: 22789568 DOI: 10.1016/j.jmb.2012.06.043] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2012] [Revised: 06/14/2012] [Accepted: 06/28/2012] [Indexed: 01/14/2023]
Abstract
Processive motility of individual molecules is essential for the function of many kinesin motors. Processivity for kinesins relies on communication between the two heads of a dimeric molecule, such that binding strictly alternates. The main communicating elements are believed to be the two neck linkers connecting the motors' stalks and heads. A proposed mechanism for coordination is the transmission of stress through the neck linkers. It is believed that the efficiency of gating depends on the length of the neck linker. Recent studies have presented support for a simple model in which the length of the neck linker directly controls the degree of processivity. Based on a previously published Kinesin-1/Kinesin-5 chimera, Eg5Kin, we have analyzed the motility of 12 motor constructs: we have varied the length of the neck linker in the range between 9 and 21 amino acids using the corresponding native Kinesin-5 sequence (Xenopus laevis Eg5). We found, surprisingly, that neither velocity nor force generation depended on neck-linker length. We also found that constructs with short neck linkers, down to 12 amino acids, were still highly processive, while processivity was lost at a length of 9 amino acids. Run lengths were maximal with neck linkers close to the native Kinesin-5 length and decreased beyond that length. This finding generally confirms the coordinating role of the neck linker for kinesin motility but challenges the simplest model postulating a motor-type-independent optimal length. Instead, our results suggest that different kinesins might be optimized for different neck-linker lengths.
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Affiliation(s)
- André Düselder
- Drittes Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
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Liu L, Tüzel E, Ross JL. Loop formation of microtubules during gliding at high density. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:374104. [PMID: 21862840 DOI: 10.1088/0953-8984/23/37/374104] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
The microtubule cytoskeleton, including the associated proteins, forms a complex network essential to multiple cellular processes. Microtubule-associated motor proteins, such as kinesin-1, travel on microtubules to transport membrane bound vesicles across the crowded cell. Other motors, such as cytoplasmic dynein and kinesin-5, are used to organize the cytoskeleton during mitosis. In order to understand the self-organization processes of motors on microtubules, we performed filament-gliding assays with kinesin-1 motors bound to the cover glass with a high density of microtubules on the surface. To observe microtubule organization, 3% of the microtubules were fluorescently labeled to serve as tracers. We find that microtubules in these assays are not confined to two dimensions and can cross one other. This causes microtubules to align locally with a relatively short correlation length. At high density, this local alignment is enough to create 'intersections' of perpendicularly oriented groups of microtubules. These intersections create vortices that cause microtubules to form loops. We characterize the radius of curvature and time duration of the loops. These different behaviors give insight into how crowded conditions, such as those in the cell, might affect motor behavior and cytoskeleton organization.
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Affiliation(s)
- Lynn Liu
- Department of Physics, University of Massachusetts Amherst, Amherst, MA 01003, USA
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Affiliation(s)
- Henry Hess
- Department of Biomedical Engineering, Columbia University, New York, NY 10027;
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Berndt M, Lorenz M, Enderlein J, Diez S. Axial nanometer distances measured by fluorescence lifetime imaging microscopy. NANO LETTERS 2010; 10:1497-1500. [PMID: 20218702 DOI: 10.1021/nl100593x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We present a novel fluorescence lifetime imaging microscopy technique to measure absolute positions of fluorescent molecules within 100 nm above a metalized surface based on distance-dependent fluorescence lifetime modulations. We apply this technique to fluorescently labeled microtubules as optical probes with various unlabeled proteins attached. By measuring the fluorescence lifetimes, we obtain the position of the microtubules and therefore determine the geometrical size of the attached proteins with nanometer precision.
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Affiliation(s)
- Michael Berndt
- Max-Planck-Institute of Molecular Cell Biology and Genetics, Dresden, Germany
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Sugita S, Murase T, Sakamoto N, Ohashi T, Sato M. Size sorting of kinesin-driven microtubules with topographical grooves on a chip. LAB ON A CHIP 2010; 10:755-61. [PMID: 20221564 DOI: 10.1039/b920164e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Gliding microtubules (MTs) on a surface coated with kinesin biomolecular motors have been suggested for the development of nanoscale transport systems. In order to establish a sorting function for gliding MTs, events for MTs approaching micro-scale grooves were investigated. MTs longer than the width of grooves fabricated on a Si substrate bridged the grooves (bridging) and many MTs shorter than the groove width almost began to bridge, but returned to the surface that they approached from (guiding). Occurrence probabilities for the events were analyzed with focus on the geometric conditions, such as length of the MTs, width of the grooves, and the incident angle (alpha) of the MTs approaching the grooves. The occurrence probability for bridging increased with an increase in the incident angle (16%, alpha = 0-30 degrees; 51%, alpha = 30-60 degrees; 75%, alpha = 60-90 degrees), and the probability for guiding decreased with an increase in the incident angle (79%, alpha = 0-30 degrees; 55%, alpha = 30-60 degrees; 5%, alpha = 60-90 degrees). The results indicate that an incident angle of 30-60 degrees is an effective condition for MT sorting, because the bridging and guiding events can sort MTs that are longer and shorter than the groove widths, respectively. Furthermore, the occurrence probabilities of both bridging and guiding in a higher concentration of methylcellulose (0.5%) increased up to approximately 70% at incident angles of 30-60 degrees, indicating good feasibility for the development of devices for the sorting of MTs on surfaces with topographical grooves.
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Affiliation(s)
- Shukei Sugita
- Department of Biomedical Engineering, Graduate School of Biomedical Engineering, Tohoku University, 6-6-01 Aramaki-aza-Aoba, Aoba, Sendai, 980-8579, Japan.
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Nitzsche B, Bormuth V, Bräuer C, Howard J, Ionov L, Kerssemakers J, Korten T, Leduc C, Ruhnow F, Diez S. Studying kinesin motors by optical 3D-nanometry in gliding motility assays. Methods Cell Biol 2010; 95:247-71. [PMID: 20466139 DOI: 10.1016/s0091-679x(10)95014-0] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Recent developments in optical microscopy and nanometer tracking have facilitated our understanding of microtubules and their associated proteins. Using fluorescence microscopy, dynamic interactions are now routinely observed in vitro on the level of single molecules, mainly using a geometry in which labeled motors move on surface-immobilized microtubules. Yet, we think that the historically older gliding geometry, in which motor proteins bound to a substrate surface drive the motion microtubules, offers some unique advantages. (1) Motility can be precisely followed by coupling multiple fluorophores and/or single bright labels to the surface of microtubules without disturbing the activity of the motor proteins. (2) The number of motor proteins involved in active transport can be determined by several strategies. (3) Multimotor studies can be performed over a wide range of motor densities. These advantages allow for studying cooperativity of processive as well as nonprocessive motors. Moreover, the gliding geometry has proven to be most promising for nanotechnological applications of motor proteins operating in synthetic environments. In this chapter we review recent methods related to gliding motility assays in conjunction with 3D-nanometry. In particular, we aim to provide practical advice on how to set up gliding assays, how to acquire high-precision data from microtubules and attached quantum dots, and how to analyze data by 3D-nanometer tracking.
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Affiliation(s)
- Bert Nitzsche
- Max Planck Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany
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32
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