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Single-particle tracking
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<h2 id="applications">Applications</h2> <p>In life sciences, single-particle tracking is broadly used to quantify the dynamics of molecules/proteins in live cells (of bacteria, yeast, mammalian cells and live <i>Drosophila</i> embryos).<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a><a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a><a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a><a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a><a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a> It has been extensively used to study the transcription factor dynamics in live cells.<a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a><a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a><a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a> This method has been extensively used in the last decade to understand the target-search mechanism of proteins in live cells. It addresses fundamental biological questions such as how a protein of interest finds its target in the complex cellular environment? how long does it take to find its target site for binding? what is the residence time of proteins binding to DNA?<a class="footnote-ref" id="fnref:12" href="#fn:12"><sup>12</sup></a> Recently, SPT has been used to study the kinetics of protein translating and processing in vivo. For molecules which bind large structures such as ribosomes, SPT can be used to extract information about the binding kinetics. As ribosome binding increases the effective size of the smaller molecule, the diffusion rate decreases upon binding. By monitoring these changes in diffusion behavior, direct measurements of binding events are obtained.<a class="footnote-ref" id="fnref:13" href="#fn:13"><sup>13</sup></a><a class="footnote-ref" id="fnref:14" href="#fn:14"><sup>14</sup></a> Furthermore, exogenous particles are employed as probes to assess the mechanical properties of the medium, a technique known as passive <a href="/facts/Microrheology/nSPhRoyN">microrheology</a>.<a class="footnote-ref" id="fnref:15" href="#fn:15"><sup>15</sup></a> This technique has been applied to investigate the motion of lipids and proteins within membranes,<a class="footnote-ref" id="fnref:16" href="#fn:16"><sup>16</sup></a><a class="footnote-ref" id="fnref:17" href="#fn:17"><sup>17</sup></a> molecules in the nucleus <a class="footnote-ref" id="fnref:18" href="#fn:18"><sup>18</sup></a> and cytoplasm,<a class="footnote-ref" id="fnref:19" href="#fn:19"><sup>19</sup></a> organelles and molecules therein,<a class="footnote-ref" id="fnref:20" href="#fn:20"><sup>20</sup></a> lipid granules,<a class="footnote-ref" id="fnref:21" href="#fn:21"><sup>21</sup></a><a class="footnote-ref" id="fnref:22" href="#fn:22"><sup>22</sup></a><a class="footnote-ref" id="fnref:23" href="#fn:23"><sup>23</sup></a> vesicles, and particles introduced in the cytoplasm or the nucleus. Additionally, single-particle tracking has been extensively used in the study of reconstituted lipid bilayers,<a class="footnote-ref" id="fnref:24" href="#fn:24"><sup>24</sup></a> intermittent diffusion between 3D and either 2D (e.g., a membrane) <a class="footnote-ref" id="fnref:25" href="#fn:25"><sup>25</sup></a> or 1D (e.g., a DNA polymer) phases, and synthetic entangled actin networks.<a class="footnote-ref" id="fnref:26" href="#fn:26"><sup>26</sup></a><a class="footnote-ref" id="fnref:27" href="#fn:27"><sup>27</sup></a> </p> <h2 id="methods">Methods</h2> <p>The most common type of particles used in single particle tracking are based either on <a href="/facts/Scatterer/nMou7lEH">scatterers</a>, such as polystyrene beads or gold <a href="/facts/Nanoparticle/k8kNxX4E">nanoparticles</a> that can be tracked using bright field illumination, or <a href="/facts/Fluorescence/qsJVT2qP">fluorescent</a> particles. For <a href="/facts/Fluorescent_tag/vKVEgb0v">fluorescent tags</a>, there are many different options with their own advantages and disadvantages, including <a href="/facts/Quantum_dot/K5Ytv8Yw">quantum dots</a>, <a href="/facts/Fluorescent_protein/WQv6UQ7T">fluorescent proteins</a>, organic <a href="/facts/Fluorophore/wDWBmYhn">fluorophores</a>, and cyanine dyes. </p><p>On a fundamental level, once the images are obtained, single-particle tracking is a two step process. First the particles are detected and then the localized different particles are connected in order to obtain individual trajectories. </p><p>Besides performing particle tracking in 2D, there are several imaging modalities for 3D particle tracking, including <a href="/facts/Multifocal_plane_microscopy/a281jHlz">multifocal plane microscopy</a>,<a class="footnote-ref" id="fnref:28" href="#fn:28"><sup>28</sup></a> double helix point spread function microscopy,<a class="footnote-ref" id="fnref:29" href="#fn:29"><sup>29</sup></a> and introducing astigmatism via a cylindrical lens or adaptive optics. </p> <h2 id="brownian-diffusion">Brownian diffusion</h2> <p class="note">Main article: <a href="/facts/Brownian_motion/Th0g0wkr">Brownian motion</a></p> <h2 id="see-also">See also</h2> <ul><li><a href="/facts/Brownian_motion/Th0g0wkr">Brownian motion</a></li> <li><a href="/facts/Diffusion/KbAxroBa">Diffusion</a></li> <li><a href="/facts/Microrheology/nSPhRoyN">Microrheology</a></li> <li><a href="/facts/Nanoparticle_tracking_analysis/Q7VWg1BB">Nanoparticle tracking analysis</a></li> <li><a href="/facts/Single-molecule_experiment/R2UlIe8H">Single-molecule experiment</a></li> <li><a href="/facts/Single-particle_trajectory/xcIq66ec">Single particle trajectory</a></li> <li><a href="/facts/Tethered_particle_motion/SFzIzmG7">Tethered particle motion</a></li></ul> <h2 id="external-links">External links</h2> <ul><li><a href="https://imagej.net/TrackMate">TrackMate</a></li> <li><a href="https://www.utsouthwestern.edu/labs/danuser/software/#utrack_anc">U-Track</a></li> <li><a href="https://www.oxinst.com/learning/view/article/double-helix-and-super-resolution">Double helix PSF method (Andor)</a></li> <li><a href="http://inadilic.fr/data/">Examples of simulated or experimental single-particle trajectories</a></li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>Metzler, Ralf; Jeon, Jae-Hyung; Cherstvy, Andrey G.; Barkai, Eli (2014). "Anomalous diffusion models and their properties: non-stationarity, non-ergodicity, and ageing at the centenary of single particle tracking". Phys. Chem. Chem. Phys. 16 (44): 24128–24164. Bibcode:2014PCCP...1624128M. doi:10.1039/c4cp03465a. ISSN 1463-9076. PMID 25297814. <a href="https://doi.org/10.1039%2Fc4cp03465a" target="_blank">https://doi.org/10.1039%2Fc4cp03465a</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>Manzo, Carlo; Garcia-Parajo, Maria F (2015-10-29). "A review of progress in single particle tracking: from methods to biophysical insights". Reports on Progress in Physics. 78 (12): 124601. Bibcode:2015RPPh...78l4601M. doi:10.1088/0034-4885/78/12/124601. ISSN 0034-4885. PMID 26511974. S2CID 25691993. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>Anthony, Stephen; Zhang, Liangfang; Granick, Steve (2006). "Methods to Track Single-Molecule Trajectories". Langmuir. 22 (12): 5266–5272. doi:10.1021/la060244i. ISSN 0743-7463. PMID 16732651. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>Höfling, Felix; Franosch, Thomas (2013-03-12). "Anomalous transport in the crowded world of biological cells". Reports on Progress in Physics. 76 (4): 046602. arXiv:1301.6990. Bibcode:2013RPPh...76d6602H. doi:10.1088/0034-4885/76/4/046602. ISSN 0034-4885. PMID 23481518. S2CID 40921598. <a href="/wiki/ArXiv_(identifier)" target="_blank">/wiki/ArXiv_(identifier)</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>Podh, Nitesh Kumar; Paliwal, Sheetal; Dey, Partha; Das, Ayan; Morjaria, Shruti; Mehta, Gunjan (5 November 2021). "In-vivo Single-Molecule Imaging in Yeast: Applications and Challenges". Journal of Molecular Biology. 433 (22): 167250. doi:10.1016/j.jmb.2021.167250. 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