{"669320":{"#nid":"669320","#data":{"type":"news","title":"Physicists Solve Mysteries of Microtubule Movers","body":[{"value":"\u003Cp\u003E\u003Cstrong\u003EActive matter\u003C\/strong\u003E is any collection of materials or systems composed of individual units that can move on their own, thanks to self-propulsion or autonomous motion. They can be of any size \u2014 think clouds of bacteria in a petri dish, or schools of fish.\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u003Ca href=\u0022https:\/\/physics.gatech.edu\/user\/roman-grigoriev\u0022\u003E\u003Cstrong\u003ERoman Grigoriev\u003C\/strong\u003E\u003C\/a\u003E is mostly interested in the emergent behaviors in active matter systems made up of units on a molecular scale \u2014 tiny systems that convert stored energy into directed motion, consuming energy as they move and exert mechanical force.\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u201cActive matter systems have garnered significant attention in physics, biology, and materials science due to their unique properties and potential applications,\u201d Grigoriev, a professor in the \u003Ca href=\u0022https:\/\/physics.gatech.edu\/\u0022\u003ESchool of Physics\u003C\/a\u003E at Georgia Tech, explains.\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u201cResearchers are exploring how active matter can be harnessed for tasks like designing new materials with tailored properties, understanding the behavior of biological organisms, and even developing new approaches to robotics and autonomous systems,\u201d he says.\u003C\/p\u003E\r\n\r\n\u003Cp\u003EBut that\u2019s only possible if scientists learn how the microscopic units making up active matter interact, and whether they can affect these interactions and thereby the collective properties of active matter on the macroscopic scale.\u003C\/p\u003E\r\n\r\n\u003Cp\u003EGrigoriev and his research colleagues have found a potential first step by developing a new model of active matter that generated new insight into the physics of the problem. They detail their methods and results in a new \u003Ca href=\u0022https:\/\/www.science.org\/doi\/10.1126\/sciadv.abq6120\u0022\u003Estudy\u003C\/a\u003E published in \u003Cem\u003EScience Advances\u003C\/em\u003E, \u201cPhysically informed data-driven modeling of active nematics.\u201d\u003C\/p\u003E\r\n\r\n\u003Cp\u003ESchool of Physics graduate researcher \u003Ca href=\u0022https:\/\/www.linkedin.com\/in\/matthew-golden-03ba99117?original_referer=https%3A%2F%2Fwww.google.com%2F\u0022\u003E\u003Cstrong\u003EMatthew Golden\u003C\/strong\u003E\u003C\/a\u003E is the study\u0027s lead author. Co-authors are graduate researcher \u003Cstrong\u003E\u003Ca href=\u0022https:\/\/physics.gatech.edu\/user\/jyothishraj-nambisan\u0022\u003EJyothishraj Nambisan\u003C\/a\u003E \u003C\/strong\u003Eand \u003Ca href=\u0022https:\/\/www.icrea.cat\/Web\/ScientificStaff\/alberto-fernandez-nieves-280811\u0022\u003E\u003Cstrong\u003EAlberto Fernandez-Nieves\u003C\/strong\u003E\u003C\/a\u003E, professor in the Department of Condensed Matter Physics at the \u003Cstrong\u003E\u003Ca href=\u0022https:\/\/web.ub.edu\/en\/\u0022\u003EUniversity of Barcelona\u003C\/a\u003E\u003C\/strong\u003E and a former associate professor of Physics at Georgia Tech.\u003C\/p\u003E\r\n\r\n\u003Ch4\u003EA two-dimensional \u0027solution?\u0027\u003C\/h4\u003E\r\n\r\n\u003Cp\u003EThe research team focused on one of the most common examples of active matter, a suspension of self-propelled particles, such as bacteria or synthetic microswimmers, in a liquid medium. These particles cluster, swarm, and otherwise form dynamic patterns due to their ability to move and interact with each other.\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u201cIn our paper, we use data from an experimental system involving suspensions of microtubules, which provide structural support, shape, and organization to eukaryotic cells (any cell with a clearly defined nucleus),\u201d Grigoriev explains.\u003C\/p\u003E\r\n\r\n\u003Cp\u003EMicrotubules, as well as actin filaments and some bacteria, are examples of nematics, rod-like objects whose \u0022heads\u0022 are indistinguishable from their \u0022tails.\u201d\u003C\/p\u003E\r\n\r\n\u003Cp\u003EThe motion of microtubules is driven by molecular motors powered by a protein, kinesin, which consumes adenosine triphosphate (ATP) dissolved in the liquid to slide a pair of neighboring microtubules past one another. The researcher\u2019s system used microtubules suspended between layers of oil and water, which restricted their movement to two dimensions.\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u201cThat makes it easier to visualize the microtubules and track their motion. By changing the kinesin or ATP concentrations, we could control the motion of the microtubules, making this experimental setup by far one of the most popular in the study of active nematics and even more generally, active matter,\u201d Grigoriev said.\u003C\/p\u003E\r\n\r\n\u003Ch4\u003E\u2018This is where the story gets interesting\u2019\u003C\/h4\u003E\r\n\r\n\u003Cp\u003EGetting a clearer picture of microtubular movements was just one discovery in the study.\u003C\/p\u003E\r\n\r\n\u003Cp\u003EAnother was learning more about the relationships between the characteristic patterns describing the orientation and motion of nematic molecules on a macroscopic scale. Those patterns, or topological defects, determine how the nematics orient themselves at the oil-water interface, that is in two spatial dimensions.\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u201cUnderstanding the relationship between the flow \u2014 the global property of the system, or the fluid \u2014 and the topological defects, which describe the local orientation of microtubules, is one of the key intellectual questions facing researchers in the field,\u201d Grigoriev said. \u201cOne needs to correctly identify the dominant physical effects which control the interaction between the microtubules and the surrounding fluid.\u201d\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u201cAnd this is where the story gets interesting,\u201d Grigoriev adds. \u201cFor over a decade, it was believed that the key physics were well understood, with a large number of theoretical and computational studies relying on a generally accepted first principles model\u201d \u2014 that is, one based on established science \u2014 \u201cthat was originally derived for active nematics in three spatial dimensions.\u201d\u003C\/p\u003E\r\n\r\n\u003Cp\u003EIn the Georgia Tech model, though, the dynamics of active nematics \u2014 more specifically, the length and time scales of the emerging patterns \u2014 are controlled by a pair of physical constants describing those assumed dominant physical effects: the stiffness of the microtubules (their flexibility), and the activity describing the stress, or force, generated by the kinesin motors.\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u201cUsing a data-driven approach, we inferred the correct form of the model demonstrating that, for two-dimensional active nematics, the dominant physical effects are different from what was previously assumed,\u201d Grigoriev says. \u201cIn particular, the time scale is set by the rate at which bundles of microtubules are stretched by kinesin.\u201d It is this rate, rather than the stress, that is constant.\u003C\/p\u003E\r\n\r\n\u003Ch4\u003EThe danger of confirmation bias\u003C\/h4\u003E\r\n\r\n\u003Cp\u003EGrigoriev said the results of the study have important implications for understanding of active nematics and their emergent behaviors, explaining that they help rationalize a number of recent experimental results that were previously unexplained, such as how the density of topological defects scales with the concentration of kinesin and the viscosity of the fluid layers.\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u201cMore importantly, our results demonstrate the danger associated with traditional assumptions that established research communities often land on and have difficulty overcoming,\u201d Grigoriev said. \u201cWhile data-driven methods may have their own sources of bias, they offer a perspective which is different enough from more traditional approaches to become a valuable research tool in their own right.\u201d\u003C\/p\u003E\r\n\r\n\u003Ch4\u003EAbout Georgia Institute of Technology\u003C\/h4\u003E\r\n\r\n\u003Cp\u003EThe Georgia Institute of Technology, or Georgia Tech, is one of the top public research universities in the U.S., developing leaders who advance technology and improve the human condition. The Institute offers\u202fbusiness, computing, design, engineering, liberal arts,\u202fand\u202fsciences degrees. Its more than 45,000 undergraduate and graduate students, representing 50 states and more than 148 countries, study at the main campus in Atlanta, at campuses in France and China, and through distance and online learning. As a leading technological university, Georgia Tech is an engine of economic development for Georgia, the Southeast, and the nation, conducting more than $1 billion in research annually for government, industry, and society.\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u003Cstrong\u003EFunding:\u003C\/strong\u003E This study was funded by the National Science Foundation, grant no. CMMI-2028454. \u003Cem\u003E\u201cPhysically informed data-driven modeling of active nematics,\u201d DOI: 10.1126\/sciadv.abq6120\u003C\/em\u003E\u003C\/p\u003E\r\n","summary":"","format":"limited_html"}],"field_subtitle":[{"value":"Physicists have developed a new model and clearer picture of molecular movements within active matter \u2014 bringing science a step closer to designing specific functions into new materials, and understanding emergent behaviors."}],"field_summary":[{"value":"\u003Cp\u003EPhysicists have developed a new model and clearer picture of molecular movements within active matter \u2014 bringing science a step closer to designing specific functions into new materials, and understanding emergent behaviors.\u003C\/p\u003E\r\n","format":"limited_html"}],"field_summary_sentence":[{"value":"Physicists have developed a new model and clearer picture of molecular movements within active matter \u2014 bringing science a step closer to designing specific functions into new materials, and understanding emergent behaviors."}],"uid":"34434","created_gmt":"2023-08-31 17:30:35","changed_gmt":"2023-10-06 01:01:51","author":"Renay San Miguel","boilerplate_text":"","field_publication":"","field_article_url":"","dateline":{"date":"2023-09-01T00:00:00-04:00","iso_date":"2023-09-01T00:00:00-04:00","tz":"America\/New_York"},"extras":[],"hg_media":{"671575":{"id":"671575","type":"image","title":"Three noticeable out-of-plane microtubule bundles are misaligned with the rest of the microtubules at the bottom left of the image.","body":"\u003Cp\u003EThree noticeable out-of-plane microtubule bundles are misaligned with the rest of the microtubules at the bottom left of the image.\u003C\/p\u003E\r\n","created":"1693596313","gmt_created":"2023-09-01 19:25:13","changed":"1693596313","gmt_changed":"2023-09-01 19:25:13","alt":"Microtubules","file":{"fid":"254662","name":"sciadv-grigoriev.jpg","image_path":"\/sites\/default\/files\/2023\/09\/01\/sciadv-grigoriev_0.jpg","image_full_path":"http:\/\/hg.gatech.edu\/\/sites\/default\/files\/2023\/09\/01\/sciadv-grigoriev_0.jpg","mime":"image\/jpeg","size":963257,"path_740":"http:\/\/hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/2023\/09\/01\/sciadv-grigoriev_0.jpg?itok=t5-2wU6x"}},"671559":{"id":"671559","type":"image","title":"Left, a graphic showing microtubules orienting themselves in the experiment. 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