Abstract
In this study, transmission electron microscopy atomic force microscopy, and surface enhanced Raman spectroscopy are combined through a direct imaging approach, to gather structural and chemical information of complex molecular systems such as ion channels in their original plasma membrane. Customized microfabricated sample holder allows to characterize Nav channels embedded in the original plasma membrane extracted from neuronal cells that are derived from healthy human induced pluripotent stem cells. The identification of the channels is accomplished by using two different approaches, one of them widely used in cryo-EM (the particle analysis method) and the other based on a novel Zernike Polynomial expansion of the images bitmap. This approach allows to carry out a whole series of investigations, one complementary to the other, on the same sample, preserving its state as close as possible to the original membrane configuration.
The authors acknowledge financial support from King Abdullah University of Science and Technology for OCRF-2014-CRG and OCRF-2016-CRG grants; SHAHEEN cluster to provide machine time; Professor Charlotte A. E. Hauser for providing access to SHAHEEN, and from Piedmont Region through European Funds for Regional Development (“Food Digital Monitoring” project); European Research Council Synergy grant ASTRA (n. 855923).