Mechanical Properties of Individual Molecules : An Interface between the Structure and the Function of the Molecules

Optical tweezers with a 3D position detection were used to investigate the mechanical properties of individual molecules. The molecular receptor-ligand pair of avidin and biotin was used as a model system to establish our technique. Optical tweezers created the possibility to position the microsphere into close proximity of the surface and to define the local boundary conditions for the interaction. Under these experimental conditions we measured the average binding time of the bead to the surface as a function of the density of biotin on the surface. A diffusion based model was used to estimate the effective size of the molecular binding center from the average reaction time. The size of the molecular binding center as determined by our method is in good agreement with the size of an individual Bovine Serum Albumin molecule. The lateral position fluctuations of the bound bead were also used to determine the type of the contact. It was possible to distinguish between individual and multiple molecular bonds. The same method was applied to the study of mechanical properties of the SNARE-complex. The SNARE-complex consists of three proteins: syntaxin, synaptobrevin and SNAP-25. We measured and analyzed the mechanical properties of the interactions between four combinations between the building blocks of the SNARE-complex. Altogether, four different protein combinations were measured. The molecular binding assay showed qualitative differences between different molecules. In particular, the interaction between two syntaxin molecules and a single SNAP-25 molecule showed a unique pattern: a continuous decrease in lateral position fluctuations was accompanied by a rotation. This spiralling was interpreted in terms of an individual SNARE-complex formation.

Level thesis:degree_level

thesis.doctoral

Grantor dc:publisher

Universität Heidelberg

Year

2003

Author dc:creator

• Fisinger, Samo

Contributors dc:contributor

• Povh, Bogdan

Repository record source_url

http://www.ub.uni-heidelberg.de/archiv/4565

OAI identifier oai:identifier

oai:archiv.ub.uni-heidelberg.de:4565