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Development and applications of atomic force microscopy for the study of proteins and cancer cells

Jorge R. Ramos (Instituto de Ciencia de Materiales de Madrid, Espagne)
When May 26, 2015
from 02:00 PM to 03:00 PM
Where room 116
Attendees Jorge R. Ramos
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Atomic force microscopy (AFM) has a wide range of applications in biophysics. Nowadays it is possible to study from DNA strands, proteins and viruses to cells and tissues. In the first part of this talk I discuss some experimental factors we should consider to operate an AFM in amplitude modulation (AM-AFM) while imaging biomolecules. The second part is related to the determination of elastic properties of cell’s cytoskeleton by AFM spectroscopy.

AM-AFM is commonly used to image single biomolecules. However, to achieve high resolution we must select operation parameters that guarantee the tip shape preservation [1]. The suggested protocol was used to visualize IgG antibodies and the extracellular region of the epidermal growth factor receptor, two proteins of 150 kDa and 100 kDa, respectively. The measured volume of the protein was used to identify both types of molecules and their complex when measured together.

In the other hand, in AM-AFM the phase channel have been related the material properties and the tip-sample dissipated energy. To correlate the measured phase with the dissipated and the material properties we should include the contribution of higher harmonics generated during the tip-sample interaction [2].

Regarding to the force spectroscopy, it is well known that cancer cells are usually softer than non-malignant ones.  Cancer cells can be classified according to their malignancy degree. In our work we compare the elastic properties of the actin cytoskeleton of four cell lines with epithelial origin, one non-malignant and three cell lines with malignancy degree from 2 to 4. Surprisingly, the malignancy degree of the cancer cell lines doesn’t seem to affect the cell elasticity [3].

[1]  Ramos, J.R., Tip radius preservation for high resolution imaging in amplitude modulation atomic force microscopy. Applied Physics Letters, 2014. 105(4): p. 043111.

[2]  Payam, A.F., J.R. Ramos, and R. Garcia, Molecular and Nanoscale Compositional Contrast of Soft Matter in Liquid: Interplay between Elastic and Dissipative Interactions. ACS Nano, 2012. 6(6): p. 4663-4670.

[3]  Ramos, J.R., et al., The softening of human bladder cancer cells happens at an early stage of the malignancy process. Beilstein Journal of Nanotechnology, 2014. 5: p. 447-457.