| 1. |
- Coelho, Miguel, et al.
(författare)
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Fusion of Protein Aggregates Facilitates Asymmetric Damage Segregation
- 2014
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Ingår i: PLoS biology. - : Public Library of Science (PLoS). - 1544-9173 .- 1545-7885. ; 12:6, s. e1001886-
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Tidskriftsartikel (refereegranskat)abstract
- Asymmetric segregation of damaged proteins at cell division generates a cell that retains damage and a clean cell that supports population survival. In cells that divide asymmetrically, such as Saccharomyces cerevisiae, segregation of damaged proteins is achieved by retention and active transport. We have previously shown that in the symmetrically dividing Schizosaccharomyces pombe there is a transition between symmetric and asymmetric segregation of damaged proteins. Yet how this transition and generation of damage-free cells are achieved remained unknown. Here, by combining in vivo imaging of Hsp104-associated aggregates, a form of damage, with mathematical modeling, we find that fusion of protein aggregates facilitates asymmetric segregation. Our model predicts that, after stress, the increased number of aggregates fuse into a single large unit, which is inherited asymmetrically by one daughter cell, whereas the other one is born clean. We experimentally confirmed that fusion increases segregation asymmetry, for a range of stresses, and identified Hsp16 as a fusion factor. Our work shows that fusion of protein aggregates promotes the formation of damage-free cells. Fusion of cellular factors may represent a general mechanism for their asymmetric segregation at division.
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| 2. |
- Lade, Steven J., et al.
(författare)
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Effectiveness of beads for tracking small-scale molecular motor dynamics
- 2011
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Ingår i: Physical Review E (Statistical, Nonlinear, and Soft Matter Physics). - 1539-3755. ; 84:2
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Tidskriftsartikel (refereegranskat)abstract
- Investigations into molecular motor dynamics are increasingly focused on small-scale features of the motor's motion. We define performance measures of a common type of single-molecule motility assay, the bead assay, for its ability to detect such features. Using numerical models, we explore the dependence of assay performance on a number of experimentally controllable parameters, including bead size, optical force, and the method of attaching the bead to the motor. We find that the best parameter choice depends on the objective of the experiments, and give a guide to parameter selection. Comparison of the models against experimental data from a recent bead assay of myosin V exemplifies how our methods can also be used to extract additional information from bead assays, particularly that related to small-scale features. By analyzing the experimental data we find evidence for previously undetected multiple waiting states of the bead-motor complex. Furthermore, from numerical simulations we find that equilibrium bead dynamics display features previously attributed to aborted motor steps, and that bead dynamics alone can produce multiple subphases during a step.
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| 3. |
- Lade, Steven J., et al.
(författare)
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Regime shifts in a social-ecological system
- 2013
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Ingår i: Theoretical Ecology. - : Springer Science and Business Media LLC. - 1874-1738 .- 1874-1746. ; 6:3, s. 359-372
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Tidskriftsartikel (refereegranskat)abstract
- Ecological regime shifts are rarely purely ecological. Not only is the regime shift frequently triggered by human activity, but the responses of relevant actors to ecological dynamics are often crucial to the development and even existence of the regime shift. Here, we show that the dynamics of human behaviour in response to ecological changes can be crucial in determining the overall dynamics of the system. We find a social-ecological regime shift in a model of harvesters of a common-pool resource who avoid over-exploitation of the resource by social ostracism of non-complying harvesters. The regime shift, which can be triggered by several different drivers individually or also in combination, consists of a breakdown of the social norm, sudden collapse of co-operation and an over-exploitation of the resource. We use the approach of generalized modeling to study the robustness of the regime shift to uncertainty over the specific forms of model components such as the ostracism norm and the resource dynamics. Importantly, the regime shift in our model does not occur if the dynamics of harvester behaviour are not included in the model. Finally, we sketch some possible early warning signals for the social-ecological regime shifts we observe in the models.
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| 4. |
- Rocha, Juan Carlos, 1984-
(författare)
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Regime Shifts in the Anthropocene
- 2013
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Regime shifts are large, abrupt and often hard to reverse changes in the function and structure of socal-ecological systems. These regime shifts have been documented in a broad range of systems and scales both in marine, terrestrial and polar ecosystems. Regime shifts have attracted the attention of scientists, managers and policy makers because they substantially affect the flow of ecosystem services that society relies on. Despite their re|evance in the face of climate change or increasing pressure of the anthropocene, little is understood about the overall patterns of regime shifts causation and impacts for human well being. This licentiate thesis summarises the first steps towards a global assessment of regime shifts. Paper I is a literature review that attempts to synthesise the state of the art of regime shifts theory, its application in different disciplines, and frontiers of research. Paper II outlines a framework developed to study and compare regime shifts across different systems and scales, namely the Regime Shifts Database. Paper III investigates the patterns of drivers co-occurrence, and outlines the opportunities and challenges for management of regime shifts. The three papers together propose a new approach to study regime shifts that combines system thinking and tools from network science to analyze phenomena where knowledge about causal mechanisms, opportunities for experimentation and time series data are limited or unavailable. The discussion reflects upon the limitation and opportunities of our approach and outlines the guidelines for future developments of my PhD project.
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