PRX LifePub Date : 2022-11-14DOI: 10.1103/prxlife.1.013003
C. Maggi, F. Saglimbeni, V. Sosa, R. Di Leonardo, B. Nath, A. Puglisi
{"title":"Thermodynamic Limits of Sperm Swimming Precision","authors":"C. Maggi, F. Saglimbeni, V. Sosa, R. Di Leonardo, B. Nath, A. Puglisi","doi":"10.1103/prxlife.1.013003","DOIUrl":"https://doi.org/10.1103/prxlife.1.013003","url":null,"abstract":"Sperm swimming is crucial to fertilise the egg, in nature and in assisted reproductive technologies. Modelling the sperm dynamics involves elasticity, hydrodynamics, internal active forces, and out-of-equilibrium noise. Here we demonstrate experimentally the relevance of energy dissipation for sperm beating fluctuations. For each motile cell, we reconstruct the time-evolution of the two main tail's spatial modes, which together trace a noisy limit cycle characterised by a maximum level of precision $p_{max}$. Our results indicate $p_{max} sim 10^2 s^{-1}$, remarkably close to the estimated precision of a dynein molecular motor actuating the flagellum, which is bounded by its energy dissipation rate according to the Thermodynamic Uncertainty Relation. Further experiments under oxygen deprivation show that $p_{max}$ decays with energy consumption, as it occurs for a single molecular motor. Both observations can be explained by conjecturing a high level of coordination among the conformational changes of dynein motors. This conjecture is supported by a theoretical model for the beating of an ideal flagellum actuated by a collection of motors, including a motor-motor nearest neighbour coupling of strength $K$: when $K$ is small the precision of a large flagellum is much higher than the single motor one. On the contrary, when $K$ is large the two become comparable.","PeriodicalId":420529,"journal":{"name":"PRX Life","volume":"40 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132415064","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
PRX LifePub Date : 2022-09-19DOI: 10.1103/prxlife.1.013012
W. LeCompte, Karin John
{"title":"Molecular Motors Enhance Microtubule Lattice Plasticity","authors":"W. LeCompte, Karin John","doi":"10.1103/prxlife.1.013012","DOIUrl":"https://doi.org/10.1103/prxlife.1.013012","url":null,"abstract":"Microtubules are key structural elements of living cells that are crucial for cell division, intracellular transport and motility. Recent experiments have shown that microtubule severing proteins and molecular motors stimulate the direct and localized incorporation of free tubulin into the shaft. However, a mechanistic picture how microtubule associated proteins affect the lattice is completely missing. Here we theoretically explore a potential mechanism of lattice turnover stimulated by processive molecular motors in which a weak transient destabilization of the lattice by the motor stepping promotes the formation of mobile vacancies. In the absence of free tubulin the defect rapidly propagates leading to a complete fracture. In the presence of free tubulin, the motor walk induces a vacancy drift in the direction opposite of the motor walk. The drift is accompanied by the direct and localized incorporation of free tubulin along the trajectory of the vacancy. Our results are consistent with experiments and strongly suggest that a weak lattice-motor interaction is responsible for an augmented microtubule shaft plasticity.","PeriodicalId":420529,"journal":{"name":"PRX Life","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124960889","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}