Interactions between biomolecules studied on the
single molecular scale.
Malte Bussiek, Chandreshekar Murade, Dessy Nikova, Kim Sweers,
Martin L. Bennink, Vinod Subramaniam
Nanobiophysics Group, department of Science and Technology and MESA+ Institute for
Nanotechnology, University of Twente, Enschede, Netherlands, m.l.bennink@utwente.nl
In this paper I will present and discuss our results we have obtained using two different
single molecule techniques, namely the force-measuring optical tweezers and atomic
force microscopy.
After a short introduction of the optical tweezers as a force-measuring tool, I will
present the experiments in which we have measured in an accurate way the forces that
are involved in stretching DNA and chromatin fibers. The sudden opening of individual
nucleosomes, which constitute the first level of compaction of DNA into chromatin,
were observed and the force needed was recorded. In a follow-up study we have
investigated the influence of specific alpha-satellite sequences of DNA on the stability of
the nucleosomes. These sequences are part of the centromeric DNA and are known to
be involved in the definition of the kinetocore during cell division. From the data we
were able to conclude that the nucleosomes formed on these sequences are indeed
more stable and moreover we also found that the DNA itself was more flexible as
compared to a random sequence DNA fragment, which was used as a control.
In the second part of the presentation I will discuss the work we have done with atomic
force microscopy. This includes determination of the bending rigidity of DNA fragments,
derived from the curvature it has in the 2D AFM images. DNA-protein interaction will be
demonstrated both in static as well as in dynamic conditions. Since recently we have
been using the AFM to look more in detail to the structure of protein fibrils, and more
specifically those formed by alpha-synuclein, which is related to the development of
Parkinson’s disease. Initial results show that different fibrils are being formed,
indicating polymorphism. In order to shed more light on this we also have extended this
study with nano-indentation type measurements on these individual protein fibrils.