Molecules use intracellular water-filled nano-cavities to efficiently move across the cellular environment

Cover Art-01Pisa, 19 February 2015. Researchers at the Center for Nanotechnology Innovation (CNI) of the Istituto Italiano di Tecnologia, in collaboration with the NEST Laboratory of Scuola Normale Superiore of Pisa and the University of California at Irvine have recently published a work on ‘Nature Communications’, one of the most prestigious scientific journals in the world, which could in principle revolutionize cell biology. The study describes a new microscopy technique capable of investigating the movement of molecules, such as proteins, nucleic acids, and even ions, within the cell at unprecedented spatial and temporal resolution. The new technique has allowed identifying hitherto elusive intracellular water-filled nano-cavities used by molecules to efficiently move across the cellular environment and reach their destination.

This new approach is based on the use of genetically encoded fluorescent proteins that freely explore the 3D cellular environment. The obtained results depict the pattern of protein diffusion regulation with a time resolution of 1 microsecond (one millionth of a second, 100 times faster than possible with current techniques) and with spatial resolution of few nanometers (one billionth of a meter). “Through this unprecedented resolution we could reveal how life is organized within the cell. It is like being in the place of the protein, and see what the protein sees as it moves within the cell” explains Francesco Cardarelli, CNI researcher and coordinator of the study. “In such a way, we were able to reveal the existence of hitherto elusive nano-cavities containing water, in which the proteins freely diffuse in search for their targets.” The developed technique, in addition to opening a new frontier for the understanding of the fundamental mechanisms that regulate the inner life cells, will allow studying the interactions of living cells with drugs, nanoparticles and natural pathogens. “In principle, we shall be able to follow the path of a virus, for instance, within the cell” – says Cardarelli – “but also we shall learn how to predict the path of a drug, and consequently optimize related therapies.”
The type of motion observed for proteins in the nano-cavities here is the same as Einstein already described in 1905 for molecules in dilute solutions: the Brownian motion. Thus far, however, such a universal paradigm was not applied to the intracellular environment, where a different phenomenology has been always observed, i.e. a suppressed molecular diffusion as compared to dilute solutions. It is now clear that this apparent discrepancy is linked to the lack of appropriate methods of investigation of the nano-world in cells, thus far. The proposed new approach tackles this issue for the first time, and demonstrates that molecules follow the behavior described for diluted solutions by the laws of Einstein.
The structural and functional organization of the cell will now be further investigated by this powerful approach. This will in turn open the way to a new era of studies for the rational engineering of more approapriate and effective intervention tools for diagnostic and/or therapeutic purposes.