Biological Research

Only 15 years ago macromolecular crowding was still underappreciated. The last years have seen an increasing relevant number of crowding-regulated mechanisms coming to light; as the regulation of gene expression, the gating energies of membrane proteins or the regulation of the membrane protein conformation landscape.

The cell membrane is crowded with proteins, protein content reaches area fractions of 0.55 and even crystalline densities in extreme cases.

High Speed Atomic Force Microsocopy has brought new possibilities to study macromolecular crowding in membranes, providing location and structural information on unlabelled molecules with sub-second temporal resolution and full visualization of the local crowding of the molecular nanoenvironment.

The lateral organization of bacterial photosynthetic membranes is particularly important for their function because (i) the light transfer from light harvesting proteins to the reaction center depends on protein organization [1], and (ii) regulates the diffusion of quinone from the reaction center to the cytochrome bc1 complex.

Thanks to AFM we visualize and analyze the protein organization and function of bacterial photosynthetic membranes, this information is next combined with an optical spectroscopy photosynthetic energy flow assay to correlate funtion with the photosynthetic membrane supramolecular organisation. Moreover, the use of nanoscale engineering of the supramolecular organisation architecture entails a better comprehension of the photosynthetic membrane functioning.

The study of the mechanical properties of viruses has become fundamental in physical virology. It is crucial not only to know the structure of viral-nucleic acid complexes, but also the physical properties at the nanoscale such as the mechanical stability, elasticity, and dynamical responses of viruses to changes in the environmental conditions, lile pH, and to the interaction with target molecules like the host cell membranes. Only the Atomic Force Microscopy can provide this sort of information. Structural Biology techniques such as Electron-microscopy or X-Ray diffraction cannot assess this information.

The pathogenicity of Salmonella is based on its ability to replicate in eukaryotic host cells. The bacterium lives there in a membrane compartment, the vacuole. Salmonella targets host proteins using effector proteins. The biology of the host cell is altered to guarantee the success of the infection. Tubules emerge from the vacuoles and extend towards the periphery of the cell. Mechanical mapping is bringing new insights in the study of Salmonella pathogenesis.