PREDAVANJA ODRŽANA U ORGANIZACIJI HRVATSKOG BIOFIZIČKOG DRUŠTVA U 2005.

Clarendon Laboratory, Department of Physics, University of Oxford, UK

Kolokvij Hrvatskog biofizičkog društva

Optical trapping is a technique that has facilitated much of the progress made in the study of the biophysics of molecular motors at the level of single molecules. A 3-D optical trap can be used to push single motors around, via "handles" such as micron-sized polystyrene spheres. It can also be used to measure the position of such handles with nanometre resolution. To this end we developed an optical trap with back-focal plane detection and fast programmable feedback. A helium-neon laser (632 nm) is used for position detection and a solid-state fibre laser (1064 nm, 3W  CW) forms the trap. Acousto-optic deflectors (AODs) controlled by a digital signal processing board are used to achieve programmable feedback loops with flexible control options and speeds up to 8 kHz.

The system is designed for studies of two rotary molecular motors: the bacterial flagellar motor and the F1Fo-ATPase. The flagellar motor of bacteria is ~50nm in diameter. It is located in the cell membrane and enables the cell to swim by coupling ion-flow across the membrane through the MotA and MotB stator proteins to rotation of the FliF, FliG, FliM and FliN rotor proteins. The motor can rotate in both clockwise and counter-clockwise directions. Recently sub-steps in rotation have been observed. Rotation of the motor drives a helical filament via a universally-jointed hook, providing a propulsive force for bacterial cells to swim. The bacterial flagellar motor is extremely efficient and powerful, and can drive the filament to rotate at speeds of up to 1700 Hz.

Sloan School, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA

Kolokvij Instituta Ruđer Bošković i Hrvatskog biofizičkog društva

Department of Biochemistry and Molecular Biology, J. Stefan Institute, Ljubljana, Slovenia

Kolokvij Instituta Ruđer Bošković

Fizički odsjek, Prirodoslovno-matematički fakultet,  Zagreb

Izvještaj o sudjelovanju na 14th International Conference on Biomagnetism, Boston, 8-12. kolovoza 2004.

Cjelovitu prezentaciju u .pdf formatu možete preuzeti s ovih stranica putem linka: biomagnetizam - prezentacija (veličina: cca 9MB).

Institute of Biophysics, Faculty of Medicine, University of Ljubljana and J. Stefan Institute, Ljubljana, Slovenia

Kolokvij Instituta Ruđer Bošković

Vesicles are physico-chemical objects characterized by a closed boundary that separates their aqueous inside from their aqueous outside. Typical but not unique vesicle boundaries are lipid membranes. 
During the last few decades, different classes of vesicle shapes have been revealed both experimentally and theoretically. In this presentation it will first be shown which aspects of vesicle 
shape behavior are independent and which depend on the material properties of vesicle membranes. The second part of the talk will be devoted to the mechanism of the formation of narrow membrane tubes, to the usage of such tubes for the determination of membrane material constants, and to the role of membrane tubes in different cellular processes. Finally, it will be shown that in a population of growing vesicles, vesicle self-reproduction can occur efficiently only for vesicles in which their growth rate is properly related to certain properties of their membranes. The hypothesis will be put forward about a possible role of vesicles in prebiotic evolution that was derived on the basis of 
their abilities to compartmentalize, to self-replicate in the indicated selective manner, and to increase the complexity of the system by the way of vesicle fusion.