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Pan XH, Chen M, Cao SH, Xu ZQ, Li Z, Li YQ. Plasmon Coupling Enhanced Micro-Spectroscopy and Imaging for Sensitive Discrimination of Membrane Domains of a Single Cell. Chemistry 2021; 27:17331-17335. [PMID: 34609776 DOI: 10.1002/chem.202103018] [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: 08/18/2021] [Indexed: 11/08/2022]
Abstract
Different cell membrane domains play different roles in many cell processes, and the discrimination of these domains is of considerable importance for the elucidation of cellular functions. However, the strategies available for distinguishing these cell membrane domains are limited. A novel technique called plasmon coupling enhanced micro-spectroscopy and imaging to discriminate basal and lateral membrane domains of a single cell combines the application of an additional plasmonic silver film for surface plasmon (SP) excitation to selectively excite and enhance the basal membranes in the near-field with directional enhanced microscopic imaging and spectroscopy. The SP and critical evanescent fields are induced upon excitation through a silver-coated semitransparent coverslip at the surface plasmon resonance and critical angles, respectively. The basal and lateral membrane domains located within the SP and critical evanescent fields can be selectively excited and distinguished by adjusting the incident angle of laser irradiation. Moreover, the brighter images and more intense spectra of membrane-targeting fluorescence-Raman probes under directional excitation than in conventional EPI mode allow clear identification of the membrane domains.
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Affiliation(s)
- Xiao-Hui Pan
- Department of Chemistry and, the MOE Key Laboratory of Spectrochemical Analysis & Instrumentation, College of Chemistry and Chemical Engineering, Xiamen University, 422 Siming South Road, Siming District, Xiamen, 361005, P. R. China
| | - Min Chen
- Department of Chemistry and, the MOE Key Laboratory of Spectrochemical Analysis & Instrumentation, College of Chemistry and Chemical Engineering, Xiamen University, 422 Siming South Road, Siming District, Xiamen, 361005, P. R. China
| | - Shuo-Hui Cao
- Department of Chemistry and, the MOE Key Laboratory of Spectrochemical Analysis & Instrumentation, College of Chemistry and Chemical Engineering, Xiamen University, 422 Siming South Road, Siming District, Xiamen, 361005, P. R. China
| | - Zi-Qian Xu
- Department of Chemistry and, the MOE Key Laboratory of Spectrochemical Analysis & Instrumentation, College of Chemistry and Chemical Engineering, Xiamen University, 422 Siming South Road, Siming District, Xiamen, 361005, P. R. China
| | - Zhao Li
- Department of Chemistry and, the MOE Key Laboratory of Spectrochemical Analysis & Instrumentation, College of Chemistry and Chemical Engineering, Xiamen University, 422 Siming South Road, Siming District, Xiamen, 361005, P. R. China
| | - Yao-Qun Li
- Department of Chemistry and, the MOE Key Laboratory of Spectrochemical Analysis & Instrumentation, College of Chemistry and Chemical Engineering, Xiamen University, 422 Siming South Road, Siming District, Xiamen, 361005, P. R. China
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Su Q, Jiang C, Gou D, Long Y. Surface Plasmon-Assisted Fluorescence Enhancing and Quenching: From Theory to Application. ACS APPLIED BIO MATERIALS 2021; 4:4684-4705. [PMID: 35007020 DOI: 10.1021/acsabm.1c00320] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The integration of surface plasmon resonance and fluorescence yields a multiaspect improvement in surface fluorescence sensing and imaging, leading to a paradigm shift of surface plasmon-assisted fluorescence techniques, for example, surface plasmon enhanced field fluorescence spectroscopy, surface plasmon coupled emission (SPCE), and SPCE imaging. This Review aims to characterize the unique optical property with a common physical interpretation and diverse surface architecture-based measurements. The fundamental electromagnetic theory is employed to comprehensively unveil the fluorophore-surface plasmon interaction, and the associated surface-modification design is liberally highlighted to balance the surface plasmon-induced fluorescence-enhancement efforts and the surface plasmon-caused fluorescence-quenching effects. In particular, all types of surface structures, for example, silicon, carbon, protein, DNA, polymer, and multilayer, are systematically interrogated in terms of component, thickness, stiffness, and functionality. As a highly interdisciplinary and expanding field in physics, optics, chemistry, and surface chemistry, this Review could be of great interest to a broad readership, in particular, among physical chemists, analytical chemists, and in surface-based sensing and imaging studies.
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Affiliation(s)
- Qiang Su
- Shenzhen Key Laboratory of Microbial Genetic Engineering, College of Life Sciences and Oceanography, Carson International Cancer Center, Shenzhen University, 1066 Xueyuan Street, Nanshan District, Shenzhen 518055, Guangdong, China.,School of Chemistry, University of Birmingham, Edgbaston B15 2TT, Birmingham, United Kingdom
| | - Cheng Jiang
- Department of Chemistry, University of Oxford, Oxford OX1 3QZ, United Kingdom.,Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford OX3 9DU, United Kingdom
| | - Deming Gou
- Shenzhen Key Laboratory of Microbial Genetic Engineering, College of Life Sciences and Oceanography, Carson International Cancer Center, Shenzhen University, 1066 Xueyuan Street, Nanshan District, Shenzhen 518055, Guangdong, China
| | - Yi Long
- Clinical Research Center, Southern University of Science and Technology Hospital, 6019 Liuxian Street, Xili Avenue, Nanshan District, Shenzhen 518055, Guangdong, China
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3
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Chen M, Cao SH, Li YQ. Surface plasmon-coupled emission imaging for biological applications. Anal Bioanal Chem 2020; 412:6085-6100. [PMID: 32300846 DOI: 10.1007/s00216-020-02635-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2019] [Revised: 03/08/2020] [Accepted: 03/31/2020] [Indexed: 11/28/2022]
Abstract
Fluorescence imaging technology has been extensively applied in chemical and biological research profiting from its high sensitivity and specificity. Much attention has been devoted to breaking the light diffraction-limited spatial resolution. However, it remains a great challenge to improve the axial resolution in a way that is accessible in general laboratories. Surface plasmon-coupled emission (SPCE), generated by the interactions between surface plasmons and excited fluorophores in close vicinity of the thin metal film, offers an opportunity for optical imaging with potential application in analysis of molecular and biological systems. Benefiting from the highly directional and distance-dependent properties, SPCE imaging (SPCEi) has displayed excellent performance in bioimaging with improved sensitivity and axial confinement. Herein, we give a brief overview of the development of SPCEi. We describe the unique optical characteristics and constructions of SPCEi systems and highlight recent advances in the use of SPCEi for biological applications. We hope this review provides readers with both the insights and future prospects of SPCEi as a new promising imaging platform for potentially widespread applications in biological research and medical diagnostics. Graphical abstract.
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Affiliation(s)
- Min Chen
- Department of Chemistry and the MOE Key Laboratory of Spectrochemical Analysis & Instrumentation, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, Fujian, China
| | - Shuo-Hui Cao
- Department of Chemistry and the MOE Key Laboratory of Spectrochemical Analysis & Instrumentation, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, Fujian, China
| | - Yao-Qun Li
- Department of Chemistry and the MOE Key Laboratory of Spectrochemical Analysis & Instrumentation, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, Fujian, China.
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4
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Hao R, Fan Y, Anderson TJ, Zhang B. Imaging Single Nanobubbles of H 2 and O 2 During the Overall Water Electrolysis with Single-Molecule Fluorescence Microscopy. Anal Chem 2020; 92:3682-3688. [PMID: 32024359 DOI: 10.1021/acs.analchem.9b04793] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
In this work, we describe the preparation and use of a thin metal film modified Indium Tin Oxide (ITO) electrode as a highly conductive, transparent, and electrocatalytically active electrode material for studying nanobubbles generated at the electrode/solution interface. Hydrogen and oxygen nanobubbles were generated from water electrolysis on the surface of a Au/Pd alloy modified ITO electrode. The formation of single H2 and O2 nanobubbles was imaged in real time during a potential scan using single-molecule fluorescence microscopy. Our results show that while O2 nanobubbles can be detected at an early stage in the oxygen evolution reaction (OER), the formation of H2 nanobubbles requires a significant overpotential. Our study shows that thin-film-coated ITO electrodes are simple to make and can be useful electrode substrates for (single molecule) spectroelectrochemistry research.
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Affiliation(s)
- Rui Hao
- Department of Chemistry, University of Washington, Seattle, Washington 98115, United States
| | - Yunshan Fan
- Department of Chemistry, University of Washington, Seattle, Washington 98115, United States
| | - Todd J Anderson
- Department of Chemistry, University of Washington, Seattle, Washington 98115, United States
| | - Bo Zhang
- Department of Chemistry, University of Washington, Seattle, Washington 98115, United States
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Chen M, Pan XH, Liu Q, Huo SX, Cao SH, Zhai YY, Zhao Y, Li YQ. Variable-Angle Nanoplasmonic Fluorescence Microscopy: An Axially Resolved Method for Tracking the Endocytic Pathway. Anal Chem 2019; 91:13658-13664. [DOI: 10.1021/acs.analchem.9b02845] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Min Chen
- Department of Chemistry and the MOE Key Laboratory of Spectrochemical Analysis & Instrumentation, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, P.R. China
| | - Xiao-Hui Pan
- Department of Chemistry and the MOE Key Laboratory of Spectrochemical Analysis & Instrumentation, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, P.R. China
| | - Qian Liu
- Department of Chemistry and the MOE Key Laboratory of Spectrochemical Analysis & Instrumentation, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, P.R. China
| | - Si-Xin Huo
- Department of Chemistry and the MOE Key Laboratory of Spectrochemical Analysis & Instrumentation, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, P.R. China
| | - Shuo-Hui Cao
- Department of Chemistry and the MOE Key Laboratory of Spectrochemical Analysis & Instrumentation, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, P.R. China
| | - Yan-Yun Zhai
- Department of Chemistry and the MOE Key Laboratory of Spectrochemical Analysis & Instrumentation, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, P.R. China
| | - Yan Zhao
- Department of Chemistry and the MOE Key Laboratory of Spectrochemical Analysis & Instrumentation, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, P.R. China
| | - Yao-Qun Li
- Department of Chemistry and the MOE Key Laboratory of Spectrochemical Analysis & Instrumentation, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, P.R. China
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Cai WP, Zhai YY, Cao SH, Liu Q, Weng YH, Xie KX, Lin GC, Li YQ. High performance dual-mode surface plasmon coupled emission imaging apparatus integrating Kretschmann and reverse Kretschmann configurations for flexible measurements. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2016; 87:013705. [PMID: 26827326 DOI: 10.1063/1.4940193] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
A Kretschmann (KR) and reverse Kretschmann (RK) dual-mode surface plasmon coupled emission (SPCE) imaging apparatus based on prism coupling was built up. Highly directional and polarized fluorescence images for both RK and KR configurations were obtained. Besides, surface plasmon field-enhanced fluorescence and free space imaging can also be measured conveniently from this apparatus. Combining the high sensitivity of KR mode and the simplicity of RK mode, the multifunctional imaging system is flexible to provide different configurations for imaging applications. Compared to the free space imaging, SPCE imaging provides enhanced fluorescence, especially large enhancement up to about 50 fold in KR configuration. Additionally, the degree of evanescent field enhancement effect was easily estimated experimentally using the apparatus to compare the different imaging configurations. We believed that the dual-mode SPCE imaging apparatus will be useful in fundamental study of plasmon-controlled fluorescence and be a powerful tool for optical imaging, especially for microarray and biological applications.
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Affiliation(s)
- Wei-Peng Cai
- Department of Chemistry and the MOE Key Laboratory of Spectrochemical Analysis & Instrumentation, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
| | - Yan-Yun Zhai
- Department of Chemistry and the MOE Key Laboratory of Spectrochemical Analysis & Instrumentation, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
| | - Shuo-Hui Cao
- Department of Chemistry and the MOE Key Laboratory of Spectrochemical Analysis & Instrumentation, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
| | - Qian Liu
- Department of Chemistry and the MOE Key Laboratory of Spectrochemical Analysis & Instrumentation, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
| | - Yu-Hua Weng
- Department of Chemistry and the MOE Key Laboratory of Spectrochemical Analysis & Instrumentation, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
| | - Kai-Xin Xie
- Department of Chemistry and the MOE Key Laboratory of Spectrochemical Analysis & Instrumentation, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
| | - Guo-Chun Lin
- School of Physics and Mechanical & Electrical Engineering, Xiamen University, Xiamen 361005, China
| | - Yao-Qun Li
- Department of Chemistry and the MOE Key Laboratory of Spectrochemical Analysis & Instrumentation, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
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7
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Ge B, Zhu L, Kuang C, Zhang D, Fang Y, Ma Y, Liu X. Fluorescence emission difference with defocused surface plasmon-coupled emission microscopy. OPTICS EXPRESS 2015; 23:32561-32572. [PMID: 26699046 DOI: 10.1364/oe.23.032561] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
A novel fluorescence emission difference method is proposed to improve the lateral resolution of SPCEM without increasing instrument complexity. We discovered the profile of transverse PSF in SPCEM will dramatically change from a hollow spot to a solid spot, when the axial position of sample varies within one wavelength in the vicinity of the focal plane. The subtraction of an image whose PSF is hollow spot and an image with solid PSF will greatly enhance the resolution and contrast of SPCEM images. The mechanism of the distinctive PSF is demonstrated through basic optics theories, and the improvement of lateral resolution is verified by theoretical simulations and experimental results. It is believed that our method will stand out for its pleasant resolution enhancement and its instruments' simplicity to facilitate many biological cellular observations.
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Ge B, Ma Y, Kuang C, Zhang D, Toussaint KC, You S, Liu X. Resolution-enhanced surface plasmon-coupled emission microscopy. OPTICS EXPRESS 2015; 23:13159-13171. [PMID: 26074569 DOI: 10.1364/oe.23.013159] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
A novel fluorescence emission difference technique is proposed for further enhancements of the lateral resolution in surface plasmon-coupled emission microscopy (SPCEM). In the proposed method, the difference between the image with phase modulation by using a 0-2π vortex phase plate (VPP) along with a diaphragm and the original image obtained from SPCEM is used to estimate the spatial distribution of the analyzed sample. By optimizing the size of the diaphragm and the subtractive factor, the lateral resolution can be enhanced by about 20% and 33%, compared with that in SPCEM with a single 0-2π VPP and conventional wide-field fluorescence microscopy, respectively. Related simulation results are presented to verify the capability of the proposed method for improving lateral resolution and reducing imaging distortion. It is believed that the proposed method has potentials to improve the performance of SPCEM, thus facilitating biological observation and research.
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Liu Q, Cao SH, Cai WP, Liu XQ, Weng YH, Xie KX, Huo SX, Li YQ. Surface Plasmon Coupled Emission in Micrometer-Scale Cells: A Leap from Interface to Bulk Targets. J Phys Chem B 2015; 119:2921-7. [DOI: 10.1021/jp512031r] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Qian Liu
- Department of Chemistry and the MOE Key Laboratory of Spectrochemical Analysis & Instrumentation, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
| | - Shuo-Hui Cao
- Department of Chemistry and the MOE Key Laboratory of Spectrochemical Analysis & Instrumentation, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
| | - Wei-Peng Cai
- Department of Chemistry and the MOE Key Laboratory of Spectrochemical Analysis & Instrumentation, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
| | - Xiao-Qing Liu
- Department of Chemistry and the MOE Key Laboratory of Spectrochemical Analysis & Instrumentation, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
| | - Yu-Hua Weng
- Department of Chemistry and the MOE Key Laboratory of Spectrochemical Analysis & Instrumentation, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
| | - Kai-Xin Xie
- Department of Chemistry and the MOE Key Laboratory of Spectrochemical Analysis & Instrumentation, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
| | - Si-Xin Huo
- Department of Chemistry and the MOE Key Laboratory of Spectrochemical Analysis & Instrumentation, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
| | - Yao-Qun Li
- Department of Chemistry and the MOE Key Laboratory of Spectrochemical Analysis & Instrumentation, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
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10
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Cai WP, Liu Q, Cao SH, Weng YH, Liu XQ, Li YQ. Prism-Based Surface Plasmon Coupled Emission Imaging. Chemphyschem 2012; 13:3848-51. [DOI: 10.1002/cphc.201200569] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2012] [Indexed: 11/06/2022]
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Lu G, Liu J, Zhang T, Li W, Hou L, Luo C, Lei F, Manfait M, Gong Q. Plasmonic near-field in the vicinity of a single gold nanoparticle investigated with fluorescence correlation spectroscopy. NANOSCALE 2012; 4:3359-3364. [PMID: 22569965 DOI: 10.1039/c2nr12137a] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We proposed the estimation of the plasmonic near-field volume in the vicinity of a single gold nanoparticle, and observed experimentally the near-field variation due to a change in the polarization of the illuminating light. Under total-internal-reflection illumination, the plasmonic near-field volume is varied by tuning the polarization of the excitation light. The variation in the optical near-field around a single gold nanoparticle was simulated theoretically with a finite-difference time domain method, and was characterized experimentally employing a fluorescence correlation spectroscopy technique. The experimental results are in agreement quantitatively with the theoretical analysis. These results are highly relevant to important efforts to clarify the interaction between the emitter and the plasmonic antenna, and should be helpful in developing a plasmonic-enhanced total-internal-reflection fluorescence imaging microscope.
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Affiliation(s)
- Guowei Lu
- Department of Physics, State Key Laboratory for Mesoscopic Physics, Peking University, 100871 Beijing, China.
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12
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Abstract
AbstractThe ability of metal surfaces and nanostructures to localize and enhance optical fields is the primary reason for their application in biosensing and imaging. Local field enhancement boosts the signal-to-noise ratio in measurements and provides the possibility of imaging with resolutions significantly better than the diffraction limit. In fluorescence imaging, local field enhancement leads to improved brightness of molecular emission and to higher detection sensitivity and better discrimination. We review the principles of plasmonic fluorescence enhancement and discuss applications ranging from biosensing to bioimaging.
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13
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Mesoscopic analysis of motion and conformation of cross-bridges. Biophys Rev 2012; 4:299-311. [PMID: 28510208 DOI: 10.1007/s12551-012-0074-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2012] [Accepted: 03/15/2012] [Indexed: 01/03/2023] Open
Abstract
The orientation of a cross-bridge is widely used as a parameter in determining the state of muscle. The conventional measurements of orientation, such as that made by wide-field fluorescence microscopy, electron paramagnetic resonance (EPR) or X-ray diffraction or scattering, report the average orientation of 1012-109 myosin cross-bridges. Under conditions where all the cross-bridges are immobile and assume the same orientation, for example in normal skeletal muscle in rigor, it is possible to determine the average orientation from such global measurements. But in actively contracting muscle, where a parameter indicating orientation fluctuates in time, the measurements of the average value provide no information about cross-bridge kinetics. To avoid problems associated with averaging information from trillions of cross-bridges, it is necessary to decrease the number of observed cross-bridges to a mesoscopic value (i.e. the value affected by fluctuations around the average). In such mesoscopic regimes, the averaging of the signal is minimal and dynamic behavior can be examined in great detail. Examples of mesoscopic analysis on skeletal and cardiac muscle are provided.
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14
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Vasdekis AE, Laporte GP. Enhancing single molecule imaging in optofluidics and microfluidics. Int J Mol Sci 2011; 12:5135-56. [PMID: 21954349 PMCID: PMC3179156 DOI: 10.3390/ijms12085135] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2011] [Revised: 05/23/2011] [Accepted: 07/25/2011] [Indexed: 12/25/2022] Open
Abstract
Microfluidics and optofluidics have revolutionized high-throughput analysis and chemical synthesis over the past decade. Single molecule imaging has witnessed similar growth, due to its capacity to reveal heterogeneities at high spatial and temporal resolutions. However, both resolution types are dependent on the signal to noise ratio (SNR) of the image. In this paper, we review how the SNR can be enhanced in optofluidics and microfluidics. Starting with optofluidics, we outline integrated photonic structures that increase the signal emitted by single chromophores and minimize the excitation volume. Turning then to microfluidics, we review the compatible functionalization strategies that reduce noise stemming from non-specific interactions and architectures that minimize bleaching and blinking.
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Affiliation(s)
- Andreas E. Vasdekis
- Optics Laboratory, School of Engineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne CH-1015, Switzerland; E-Mail:
| | - Gregoire P.J. Laporte
- Optics Laboratory, School of Engineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne CH-1015, Switzerland; E-Mail:
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15
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Burghardt TP, Ajtai K. Single-molecule fluorescence characterization in native environment. Biophys Rev 2010; 2:159-167. [PMID: 21179385 PMCID: PMC3004222 DOI: 10.1007/s12551-010-0038-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2010] [Accepted: 10/12/2010] [Indexed: 11/29/2022] Open
Abstract
Single-molecule detection (SMD) with fluorescence is a widely used microscopic technique for biomolecule structure and function characterization. The modern light microscope with high numerical aperture objective and sensitive CCD camera can image the brightly emitting organic and fluorescent protein tags with reasonable time resolution. Single-molecule imaging gives an unambiguous bottom-up biomolecule characterization that avoids the "missing information" problem characteristic of ensemble measurements. It has circumvented the diffraction limit by facilitating single-particle localization to ~1 nm. Probes developed specifically for SMD applications extend the advantages of single-molecule imaging to high probe density regions of cells and tissues. These applications perform under conditions resembling the native biomolecule environment and have been used to detect both probe position and orientation. Native, high density SMD may have added significance if molecular crowding impacts native biomolecule behavior as expected inside the cell.
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Affiliation(s)
- Thomas P. Burghardt
- Department of Biochemistry and Molecular Biology, Mayo Clinic Rochester, Rochester, MN 55905 USA
- Department of Physiology and Biomedical Engineering, Mayo Clinic Rochester, Rochester, MN 55905 USA
| | - Katalin Ajtai
- Department of Biochemistry and Molecular Biology, Mayo Clinic Rochester, Rochester, MN 55905 USA
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Kim K, Choi JW, Ma K, Lee R, Yoo KH, Yun CO, Kim D. Nanoisland-based random activation of fluorescence for visualizing endocytotic internalization of adenovirus. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2010; 6:1293-1299. [PMID: 20517876 DOI: 10.1002/smll.201000058] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Affiliation(s)
- Kyujung Kim
- Department of Electrical and Electronic Engineering, Yonsei University, Seoul, Korea
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17
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Sun W, Marchuk K, Wang G, Fang N. Autocalibrated Scanning-Angle Prism-Type Total Internal Reflection Fluorescence Microscopy for Nanometer-Precision Axial Position Determination. Anal Chem 2010; 82:2441-7. [DOI: 10.1021/ac902789z] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Wei Sun
- Ames Laboratory−USDOE and Department of Chemistry, Iowa State University, Ames, Iowa, 50011
| | - Kyle Marchuk
- Ames Laboratory−USDOE and Department of Chemistry, Iowa State University, Ames, Iowa, 50011
| | - Gufeng Wang
- Ames Laboratory−USDOE and Department of Chemistry, Iowa State University, Ames, Iowa, 50011
| | - Ning Fang
- Ames Laboratory−USDOE and Department of Chemistry, Iowa State University, Ames, Iowa, 50011
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Tang WT, Chung E, Kim YH, So PTC, Sheppard CJR. Surface-plasmon-coupled emission microscopy with a spiral phase plate. OPTICS LETTERS 2010; 35:517-9. [PMID: 20160803 PMCID: PMC5775480 DOI: 10.1364/ol.35.000517] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
The surface plasmon-coupled emission microscope provides high sensitivity for surface imaging. However, it suffers from a distorted donut-shape point-spread function (PSF). Here we report an effective yet simple method to correct for the distortion by introducing a spiral phase plate. This modification converts the donut PSF into one that is single lobed, which is preferable for imaging. The optical performance of the system is characterized and compared with previous publications. This technique provides more than twofold lateral resolution enhancement.
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Affiliation(s)
- Wai Teng Tang
- Computation and Systems Biology, Singapore-MIT Alliance, National University of Singapore, 4 Engineering Drive 3, Singapore 117576, Singapore
- Division of Bioengineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117576, Singapore
| | - Euiheon Chung
- Edwin L. Steele Laboratory, Department of Radiation Oncology, Massachusetts General Hospital, Boston, Massachusetts 02114, USA
| | - Yang-Hyo Kim
- Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
| | - Peter T. C. So
- Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
- Department of Biological Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
| | - Colin J. R. Sheppard
- Division of Bioengineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117576, Singapore
- Department of Biological Science, National University of Singapore, 9 Science Drive 1, Singapore 117576, Singapore
- Corresponding author:
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Burghardt TP, Hipp AD, Ajtai K. Around-the-objective total internal reflection fluorescence microscopy. APPLIED OPTICS 2009; 48:6120-31. [PMID: 19904308 PMCID: PMC2802224 DOI: 10.1364/ao.48.006120] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Total internal reflection fluorescence (TIRF) microscopy uses the evanescent field on the aqueous side of a glass/aqueous interface to selectively illuminate fluorophores within approximately 100 nm of the interface. Applications of the method include epi-illumination TIRF, where the exciting light is refracted by the microscope objective to impinge on the interface at incidence angles beyond critical angle, and prism-based TIRF, where exciting light propagates to the interface externally to the microscope optics. The former has higher background autofluorescence from the glass elements of the objective where the exciting beam is focused, and the latter does not collect near-field emission from the fluorescent sample. Around-the-objective TIRF, developed here, creates the evanescent field by conditioning the exciting laser beam to propagate through the submillimeter gap created by the oil immersion high numerical aperture objective and the glass coverslip. The approach eliminates background light due to the admission of the laser excitation to the microscopic optics while collecting near-field emission from the dipoles excited by the approximately 50 nm deep evanescent field.
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Affiliation(s)
- Thomas P Burghardt
- Department of Biochemistry and Molecular Biology, Mayo Clinic Rochester, Rochester, Minnesota 55905, USA.
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20
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Thompson NL, Wang X, Navaratnarajah P. Total internal reflection with fluorescence correlation spectroscopy: Applications to substrate-supported planar membranes. J Struct Biol 2009; 168:95-106. [PMID: 19269331 PMCID: PMC2785550 DOI: 10.1016/j.jsb.2009.02.013] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2008] [Revised: 02/24/2009] [Accepted: 02/25/2009] [Indexed: 10/21/2022]
Abstract
In this paper, the conceptual basis and experimental design of total internal reflection with fluorescence correlation spectroscopy (TIR-FCS) is described. The few applications to date of TIR-FCS to supported membranes are discussed, in addition to a variety of applications not directly involving supported membranes. Methods related, but not technically equivalent, to TIR-FCS are also summarized. Future directions for TIR-FCS are outlined.
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Affiliation(s)
- Nancy L Thompson
- Department of Chemistry, University of North Carolina at Chapel Hill, 27599-3290, USA.
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Kim K, Kim DJ, Moon S, Kim D, Byun KM. Localized surface plasmon resonance detection of layered biointeractions on metallic subwavelength nanogratings. NANOTECHNOLOGY 2009; 20:315501. [PMID: 19597249 DOI: 10.1088/0957-4484/20/31/315501] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Enhanced detection of multiple targets such as self-assembled monolayer (SAM) formation, DNA hybridization, and ethanol ambient changes was explored using localized surface plasmon resonance (LSPR) excited by metallic surface nanogratings. The sensitivity enhancement depends on the target as well as the nanostructure with a maximum at 242% over a conventional structure when detecting an 11-mercaptoundecanoic acid SAM with an LSPR structure of 200 nm period. The measured enhancement shows smaller target-dependent variance when detecting various layered biointeractions, while structure-dependent variance was much larger. The result suggests the feasibility of the efficient detection of multiple biointeractions at enhanced sensitivity and extends the applicability of a nanostructured LSPR biosensor for diverse biomolecular events.
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Affiliation(s)
- Kyujung Kim
- Program for Nanomedical Science and Technology, Yonsei University, Seoul 120-749, Korea
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22
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Chung E, Kim YH, Tang WT, Sheppard CJ, So PT. Wide-field extended-resolution fluorescence microscopy with standing surface-plasmon-resonance waves. OPTICS LETTERS 2009; 34:2366-8. [PMID: 19649099 PMCID: PMC5542923 DOI: 10.1364/ol.34.002366] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
The resolution of conventional surface-plasmon-resonance (SPR) imaging has been limited by the diffraction nature of light. A wide-field extended-resolution optical imaging technique, standing-wave SPR fluorescence (SW-SPRF) microscopy, has been developed. Based on evanescent SPR standing waves, SW-SPRF provides lateral resolution approaching 100 nm and offers the advantages of significant signal enhancement and background-noise reduction. SW-SPRF has the potential for sensitive biomolecular detection, nanoscale imaging, and lithographic applications.
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Affiliation(s)
- Euiheon Chung
- Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
- Edwin L. Steele Laboratory, Department of Radiation Oncology, Massachusetts General Hospital, Boston, Massachusetts 02114, USA
| | - Yang-Hyo Kim
- Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
| | - Wai Teng Tang
- Computation and Systems Biology, Singapore–MIT Alliance, National University of Singapore, 4 Engineering Drive 3, Singapore 117576, Singapore
| | - Colin J.R. Sheppard
- Division of Bioengineering, National University of Singapore, 9 Engineering, Drive 1, Singapore 117570, Singapore
| | - Peter T.C. So
- Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
- Department of Biological Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
- Corresponding author:
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23
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Burghardt TP, Ajtai K. Mapping microscope object polarized emission to the back focal plane pattern. JOURNAL OF BIOMEDICAL OPTICS 2009; 14:034036. [PMID: 19566329 PMCID: PMC2745092 DOI: 10.1117/1.3155520] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The back focal plane (BFP) intensity pattern from a high-aperture objective separately maps far- and near-field emission from dipoles near a bare glass or metal-film-coated glass/aqueous interface. Total internal reflection (TIR) excitation of a fluorescent sample gave a BFP pattern interpreted in terms of fluorescent dipole orientation and distance from the interface. Theoretical consideration of this system led to identification of emission characteristics that remove a dipole orientation degeneracy in conventional microscope fluorescence polarization measurements. BFP pattern inspection removes the degeneracy. Alternatively, a BFP mask blocking a small fraction of emitted light in a standard imaging microscope prevents uniform collection of the BFP intensity and also eliminates the degeneracy. The BFP pattern from a single photoactivated photoactivatable green fluorescent protein (PAGFP) tagged myosin in a muscle fiber was observed despite the large background light from the highly concentrated myosin tagged with unphotoactivated PAGFP. This was accomplished by imaging the pattern from a nontelecentric plane, where most of the background intensity's pattern was translated laterally from the single-molecule object's pattern. TIR/BFP pattern imaging requires a simple alteration of the fluorescence microscope and is consistent with single-molecule imaging in a fluorophore dense three-dimensional object like a muscle fiber.
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Affiliation(s)
- Thomas P Burghardt
- Mayo Clinic Rochester, Department of Biochemistry, 200 First Street South West, Rochester, Minnesota 55905, USA.
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Burghardt TP, Li J, Ajtai K. Single myosin lever arm orientation in a muscle fiber detected with photoactivatable GFP. Biochemistry 2009; 48:754-65. [PMID: 19127992 PMCID: PMC2709297 DOI: 10.1021/bi8017703] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Myosin 2 is the molecular motor in muscle. It binds actin and executes a power stroke by rotating its lever arm through an angle of approximately 70 degrees to translate actin against resistive force. Myosin 2 has evolved to function optimally under crowded conditions where rates and equilibria of macromolecular reactions undergo major shifts relative to those measured in dilute solution. Hence, an important research objective is to detect in situ the lever arm orientation. Single-molecule measurements are preferred because they clarify ambiguities that are unavoidable with ensemble measurements; however, detecting single molecules in the condensed tissue medium where the myosin concentration exceeds 100 muM is challenging. A myosin light chain (MLC) tagged with photoactivatable green fluorescent protein (PAGFP) was constructed. The recombinant MLC physically and functionally replaced native MLC on the myosin lever arm in a permeabilized skeletal muscle fiber. Probe illumination volume was minimized using total internal reflection fluorescence microscopy, and PAGFP was sparsely photoactivated such that polarized fluorescence identified a single probe orientation. Several physiological states of the muscle fiber were characterized, revealing two distinct orientation populations in all states called straight and bent conformations. Conformation occupancy probability varies among fiber states with rigor and isometric contraction at extremes where straight and bent conformations predominate, respectively. Comparison to previous work on single rigor cross-bridges at the A-band periphery where the myosin concentration is low suggests molecular crowding in the A-band promotes occupancy of the straight myosin conformation [Burghardt, T. P., et al. (2007) Biophys. J. 93, 2226]. The latter may have a role in contraction because it provides additional free energy favoring completion of the cross-bridge power stroke.
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Affiliation(s)
- Thomas P Burghardt
- Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Rochester, Minnesota 55905, USA.
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Kim K, Kim DJ, Cho EJ, Suh JS, Huh YM, Kim D. Nanograting-based plasmon enhancement for total internal reflection fluorescence microscopy of live cells. NANOTECHNOLOGY 2009; 20:015202. [PMID: 19417244 DOI: 10.1088/0957-4484/20/1/015202] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We investigated evanescent field enhancement based on subwavelength nanogratings for improved sensitivity in total internal reflection microscopy of live cells. The field enhancement is associated with subwavelength-grating-coupled plasmon excitation. An optimum sample employed a silver grating on a silver film and an SF10 glass substrate. Field intensity was enhanced by approximately 90% when measured by fluorescent excitation of microbeads relative to that on a bare prism as a control, which is in good agreement with numerical results. The subwavelength-grating-mediated field enhancement was also applied to live cell imaging of quantum dots, which confirmed the sensitivity enhancement qualitatively.
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Affiliation(s)
- Kyujung Kim
- Program for Nanomedical Science and Technology, Yonsei University, Seoul 120-749, Korea
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Muthu P, Talent JM, Gryczynski I, Borejdo J. Cross-bridge duty cycle in isometric contraction of skeletal myofibrils. Biochemistry 2008; 47:5657-67. [PMID: 18426224 DOI: 10.1021/bi7023223] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
During interaction of actin with myosin, cross-bridges impart mechanical impulses to thin filaments resulting in rotations of actin monomers. Impulses are delivered on the average every tc seconds. A cross-bridge spends a fraction of this time (ts) strongly attached to actin, during which it generates force. The "duty cycle" (DC), defined as the fraction of the total cross-bridge cycle that myosin spends attached to actin in a force generating state (ts/ tc), is small for cross-bridges acting against zero load, like freely shortening muscle, and increases as the load rises. Here we report, for the first time, an attempt to measure DC of a single cross-bridge in muscle. A single actin molecule in a half-sarcomere was labeled with fluorescent phalloidin. Its orientation was measured by monitoring intensity of the polarized TIRF images. Actin changed orientation when a cross-bridge bound to it. During isometric contraction, but not during rigor, actin orientation oscillated between two values, corresponding to the actin-bound and actin-free state of the cross-bridge. The average ts and tc were 3.4 and 6 s, respectively. These results suggest that, in isometrically working muscle, cross-bridges spend about half of the cycle time attached to actin. The fact that 1/ tc was much smaller than the ATPase rate suggests that the bulk of the energy of ATP hydrolysis is used for purposes other than performance of mechanical work.
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Affiliation(s)
- P Muthu
- Department of Molecular Biology & Immunology and Center for Commercialization of Fluorescence Technology, the University of North Texas HSC, Fort Worth, Texas 76107, USA
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27
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Adsorption of a protein–porphyrin complex at a liquid–liquid interface studied by total internal reflection synchronous fluorescence spectroscopy. Anal Chim Acta 2008; 614:71-6. [DOI: 10.1016/j.aca.2008.03.017] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2008] [Revised: 03/06/2008] [Accepted: 03/09/2008] [Indexed: 11/23/2022]
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Abstract
Total internal reflection fluorescence microscopy (TIRFM), also known as evanescent wave microscopy, is used in a wide range of applications, particularly to view single molecules attached to planar surfaces and to study the position and dynamics of molecules and organelles in living culture cells near the contact regions with the glass coverslip. TIRFM selectively illuminates fluorophores only in a very thin (less than 100 nm deep) layer near the substrate, thereby avoiding excitation of fluorophores outside this subresolution optical section. This chapter reviews the history, current applications in cell biology and biochemistry, basic optical theory, combinations with numerous other optical and spectroscopic approaches, and a range of setup methods, both commercial and custom.
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Affiliation(s)
- Daniel Axelrod
- Departments of Physics and Biophysics, University of Michigan, Ann Arbor, Michigan 48109, USA
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Abstract
Total internal reflection-fluorescence correlation spectroscopy (TIR-FCS) is an emerging technique that is used to measure events at or near an interface, including local fluorophore concentrations, local translational mobilities and the kinetic rate constants that describe the association and dissociation of fluorophores at the interface. TIR-FCS is also an extremely promising method for studying dynamics at or near the basal membranes of living cells. This protocol gives a general overview of the steps necessary to construct and test a TIR-FCS system using either through-prism or through-objective internal reflection geometry adapted for FCS. The expected forms of the autocorrelation function are discussed for the cases in which fluorescent molecules in solution diffuse through the depth of the evanescent field, but do not bind to the surface of interest, and in which reversible binding to the surface also occurs.
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Affiliation(s)
- Nancy L Thompson
- Department of Chemistry, University of North Carolina at Chapel Hill, North Carolina 27599, USA.
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Gai H, Griess GA, Demeler B, Weintraub ST, Serwer P. Routine fluorescence microscopy of single untethered protein molecules confined to a planar zone. J Microsc 2007; 226:256-62. [PMID: 17535264 DOI: 10.1111/j.1365-2818.2007.01776.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
To bypass limitations of ensemble averaging biochemical analysis, microscopy-based detection and tracking are needed for single protein molecules that are diffusing in aqueous solution. Confining the molecules to a planar zone dramatically assists tracking. Procedures of microscopy should be routine enough so that effort is focused on the biochemistry. Fluorescence microscopy and partial planar confinement of single, untethered, aqueous protein molecules have been achieved here by use of a routine procedure. With this procedure, multiple thermally diffusing Alexa 488-stained bovine serum albumin molecules were observed during partial confinement to a thin aqueous zone next to a cover slip. The procedure produces confinement by partial re-swelling of a previously dried agarose gel on the microscope slide. Confinement was confirmed through analysis that revealed thermal motion lower in the third dimension than it was in the plane of observation.
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Affiliation(s)
- Hongwei Gai
- Department of Biochemistry, The University of Texas Health Science Center, 7703 Floyd Curl Drive, San Antonio, Texas 78229-3900, USA
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31
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Huang B, Yu F, Zare RN. Surface Plasmon Resonance Imaging Using a High Numerical Aperture Microscope Objective. Anal Chem 2007; 79:2979-83. [PMID: 17309232 DOI: 10.1021/ac062284x] [Citation(s) in RCA: 140] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We designed, constructed, and tested a surface plasmon resonance (SPR) microscope using a high numerical aperture objective from a commercially available inverted optical microscope. Such a configuration, combined with various methods to shorten the surface plasmon propagation length, achieves diffraction-limited spatial resolution in the transverse direction and near-diffraction-limited resolution in the longitudinal direction. A virtue of the objective-type SPR imaging is that we achieve distortion-free angle-resolved SPR imaging, allowing the angle-dependent reflectivity of the sample to be examined on a pixel-by-pixel basis, thus offering high-resolution information about surface properties.
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Affiliation(s)
- Bo Huang
- Department of Chemistry, Stanford University, Stanford, California 94305-5080, USA
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Borejdo J, Gryczynski Z, Calander N, Muthu P, Gryczynski I. Application of surface plasmon coupled emission to study of muscle. Biophys J 2006; 91:2626-35. [PMID: 16844757 PMCID: PMC1562373 DOI: 10.1529/biophysj.106.088369] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2006] [Accepted: 06/09/2006] [Indexed: 11/18/2022] Open
Abstract
Muscle contraction results from interactions between actin and myosin cross-bridges. Dynamics of this interaction may be quite different in contracting muscle than in vitro because of the molecular crowding. In addition, each cross-bridge of contracting muscle is in a different stage of its mechanochemical cycle, and so temporal measurements are time averages. To avoid complications related to crowding and averaging, it is necessary to follow time behavior of a single cross-bridge in muscle. To be able to do so, it is necessary to collect data from an extremely small volume (an attoliter, 10(-18) liter). We report here on a novel microscopic application of surface plasmon-coupled emission (SPCE), which provides such a volume in a live sample. Muscle is fluorescently labeled and placed on a coverslip coated with a thin layer of noble metal. The laser beam is incident at a surface plasmon resonance (SPR) angle, at which it penetrates the metal layer and illuminates muscle by evanescent wave. The volume from which fluorescence emanates is a product of two near-field factors: the depth of evanescent wave excitation and a distance-dependent coupling of excited fluorophores to the surface plasmons. The fluorescence is quenched at the metal interface (up to approximately 10 nm), which further limits the thickness of the fluorescent volume to approximately 50 nm. The fluorescence is detected through a confocal aperture, which limits the lateral dimensions of the detection volume to approximately 200 nm. The resulting volume is approximately 2 x 10(-18) liter. The method is particularly sensitive to rotational motions because of the strong dependence of the plasmon coupling on the orientation of excited transition dipole. We show that by using a high-numerical-aperture objective (1.65) and high-refractive-index coverslips coated with gold, it is possible to follow rotational motion of 12 actin molecules in muscle with millisecond time resolution.
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Affiliation(s)
- J Borejdo
- Department of Molecular Biology and Immunology, University of North Texas Health Science Center, Fort Worth, Texas 76107, USA.
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