14^th International Conference on Structural Biology September 24-26, 2018 Berlin, Germany

Biography:

Igor Sokolov it is an expert in atomic force microscopy in studying cells and biological tissues.  Being initially trained as a physicist, he received postdoctoral training in microbiology. He is the recipient of the E.L. Ginzton International Fellowship Award from Stanford University for his work on atomic force microscopy, he Graham Research Award (Clarkson University), Simon Greenberg Foundation Scholarship for study of aging skin, etc.. In 2000 he joined Clarkson University, where he achieved the title of full professor and served as director of the Nanoengineering and Biotechnology Laboratories Center. He has 150+ refereed publications, including such journals as Nature, Nature Nanotechnology, Advanced Materials, etc.. He holds 20+ patents (issued and pending). His current research focuses on nanomechanics of soft material, molecules and cells; atomic force microscopy; nanophotonics, and the studies towards understanding of nature of cancer, early detection of cancer based on altered biophysical properties; self-assembly

Abstract:

Statement of the Problem: The pericellular brush/coat (PB) is a brush-like layer that covers cell body of all eukaryotic and the majority of prokaryotic cells. The PB layer plays an important role in physics of cells. The changes in the PB layer have been implicated in the pathogenesis of many diseases, including cardio-vascular disorders, inflammation, and cancer. Nevertheless, the PB layer is rather poorly studied.  The existing biochemical methods to study the pericellular coat are specific to a particular type of molecules (content of which is frequently unknown) and lack of spatial resolution.  

Methodology & Theoretical Orientation: We describe two novel methods based on the use of atomic force microscopy (AFM) to study the PB layer. One method is based on the analysis of force curves recorded during cell indentation. The PB layer can be studied by processing these curves with so-called brush model. One can obtain physical characteristics of the PB layer, the grafting density and the brush size. The second method, Ringing mode is based on the analysis of the ringing signal recorded with the AFM sub-resonance tapping mode. One of the channels recorded in the ringing mode, the length of the grafted-to-the-cell-surface molecules, the size of the PB layer.

Findings: The first method can work with viable cells. It detects all molecules present in the PB layer without any presumptions of the biochemical methods. However, the spatial resolution is restricted in this method by the size of the appropriate AFM probe, which would be of the order of a micron. The problem of spatial resolution is solved in the second method, ringing mode. Although this method can be applied to both viable and fixed cells, it works the best on fixed cells dried in air. The lateral resolution can be as small as a few nanometers, Figure1.

Biography:

Abstract:

Biography:

Dr. Zhou is a current Professor of Gordon Life Science Institute. He is also an Adjunct Professor of several academics in both USA and CHINA. He received his Ph.D in Biophysics from University of California at Davis, and completed his postdoctoral training at Stanford University and Harvard University, respectively. He has determined the 3D NMR structures of some important biomolecules, and successfully introduced the novel diagram approach to elucidate the mechanisms of the protein-biomolecule interactions, and protein misfolding diseases observed by NMR. His current research is focused on the molecular mechanism of Neural Cell Adhesion Molecule polysialylation using NMR and biophysical approaches. In addition, He has also edited some special issues on the fields of structural biology and medicinal chemistry for several influential scientific journals as an Editorial-Board Member and Guest Editor.

Abstract:

The conversion of a normal native-helix-rich prion protein (PrP^c) to an abnormal polymeric ß-sheet-rich configuration (PrP^sc) is a misfolding process. PrP^sc is a disease associated fibril-forming isoform such as transmissible spongiform encephalopathies (TSEs) or prion diseases, a deadly disease occurred in both humans and many vertebrate animals. Our NMR studies have indicated that the misfolding process from PrP^c to PrP^sc is related to the unwinding and stability of the original α-helix structures in PrPc protein. Recently, we have also built up the wenxiang diagrams of all three helices (H1-H2-H3) of PrP^c and  observed that most hydrophobic residues of the all three helices (H1-H2-H3) in PrP^c are distinctly distributed in one-half of the wenxiang diagram of each helix, and most hydrophilic residues are distributed in the other half of the wenxiang diagrams. Similarly, most residues formed salt bridges or ionic pairs in an-helical structure are close to each other in a wenxiang diagram plane. According to these features, the helix-helix interactions, stability of alpha-helical structure, as well as possible interactions between the helix and residues outside the helix (the residues in loops) can be quickly inferred and further verified incorporating NMR spectroscopy. Our results explain why H1 is the most stable helix, and H2 is the most unstable helix during the formation process of prion disease. Thus, the incorporation of the wenxiang diagrams into NMR may provide more insight on the molecular mechanisms of the protein misfolding diseases.