Dresden 2014 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 40: Poster - Quantum Systems/ Stat. Phys./ Diffusive Process

DY 40.31: Poster

Donnerstag, 3. April 2014, 17:00–19:00, P3

Investigating Chlamydomonas reinhardtii's gears of motion by means of holographic optical tweezers and micropipettes — •Christian Ruloff, Thomas John, and Christian Wagner — Dynamics of Fluids, Wagner Group, Saarland University

Chlamydomonas reinhardtii (CR) is an approximately twelve micron sized unicellular green algae which uses two beating flagella for locomotion. The light-sensing eyespot is used to detect the incident light and stears its motion to control the distance between the algae itself and the light source for ideal photosynthesis: At low light intensities the algae is swimming towards the light source while at strong illumination CR increases its distance to it. Both flagella are not beating in the same plane leading to a superposition of foreward movement with a slight rotation mandatory for phototaxis. Besides the wild type there exist many mutants like blind or deflagellated ones. Therefore, CR is used as a model organism for research on basic questions like "How do cells move?" or "How do cells respond to light?". Using holographic optical tweezers (HOT) we generate two counterrotating optical vortices at the same spatial position which form a cogwheel potential whose radius is chosen to match the algae's body size. With this technique it is possible to partially suppress out-of-plane movement of the CR to reduce the problem to two dimensions. This is necessary because with our setup it is only possible to observe movements in the focal plane of the microscope objective. Furthermore, we want to compare our results for an almost free-swimming CR with measurements of CR in a totally body-fixed state when held by a micropipette.