Bulletin of the American Physical Society
Mid-Atlantic Section Fall Meeting 2020
Volume 65, Number 20
Friday–Sunday, December 4–6, 2020; Virtual
Session J01: Biomolecular Assemblies |
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Chair: Brigita Urbanc, Drexel University |
Sunday, December 6, 2020 9:00AM - 9:36AM |
J01.00001: Development of multimodal microscope and its application to single-molecule study of mitochondrial transcription initiation Invited Speaker: Sang-Hyuk Lee Optical microscopy can be largely classified into two groups according to how light illuminates specimen: 'wide-field' or 'focused-beam' illumination microscopy. The two microscopy modalities are often integrated into the same instrument, especially for the purpose of combining optical tweezers and fluorescence imaging, with typically employing separate lasers for the two distinct illumination schemes. We have developed a new microscope platform that enables operation of the same laser for the both modalities either interchangeably or even simultaneously in a way scalable to multiple lasers. In this talk, I will present the details of the instrument and its application to single-molecule FRET study of mitochondrial transcription initiation. [Preview Abstract] |
Sunday, December 6, 2020 9:36AM - 10:12AM |
J01.00002: Monomeric structures of the disordered amyloid-beta protein: an all-atom computational study. Invited Speaker: Cristiano Dias The aggregation of disordered peptides into oligomers and amyloid fibrils is a hallmark of several neurodegenerative diseases including Alzheimer's and Parkinson's. The interaction of these aggregates with the cell membrane accounts for an important mechanism of cell toxicity wherein annular shaped oligomers can form pores in the lipid bilayer and amyloid fibrils can induce lipid loss through a detergent-like mechanism. As monomeric amyloid peptides have been found to be mostly non-toxic, the development of strategies to inhibit aggregation has a strong potential to translate into new preventive treatments for diseases. These efforts require, however, a deep understanding of the atomic interactions and pathways accounting for amyloid aggregation. Here, I will discuss ongoing efforts in my lab to determine the set of structures adopted by monomers of the disordered amyloid-beta (A$\beta )$ protein and to identify the ones preceding aggregation. This protein is the main component of plaques in Alzheimer's disease and the existence of monomeric structures that are precursor to aggregation could have important implications in the development of new treatments. In particular, these structures could serve as targets for drugs aimed at reducing aggregation before the irreversible formation of fibrils. If time permits, I will also discuss efforts in my group to understand pathways of aggregation of small amyloid-like peptides. These efforts make use of enhanced sampling methods and very long all-atom computer simulations in explicit solvent. [Preview Abstract] |
Sunday, December 6, 2020 10:12AM - 10:24AM |
J01.00003: Binding of amyloid peptides to lipid bilayers: effects of ions and lipid content Yanxing Yang, Sharareh Jalali, Cristiano.L Dias In amyloid diseases, cell toxicity can emerge from interactions of peptides with the cell membrane. In particular, amyloid peptides can form pores in the cell membrane and/or induce lipid loss through a detergent-like mechanism. Several factors have been shown to modulate the magnitude of these peptides-bilayer interactions, which can enhance or inhibit cell toxicity. These factors include lipid composition and the presence of ions in the solution. Here, we perform all-atom molecular dynamics simulations to provide an understanding at the atomic level of peptide-bilayer interactions and their modulation by Ca and selected lipids. Simulations are performed using amphipathic sequences inspired by amyloid peptides and bilayers make from palmitoyloleoyl-phosphatidycholine lipids. We find that both electrostatic and hydrophobic interactions contribute to peptide-bilayer binding. Specifically, binding is initiated with positively charged residues interacting with lipid head groups. Hydrophobic interactions sustain this bound state. The latter accounts for an irreversible bound state at room temperature. I will discuss these mechanisms in detail as well as how they are affected by Ca and selected lipid content of the bilayer. [Preview Abstract] |
Sunday, December 6, 2020 10:24AM - 11:00AM |
J01.00004: Amyloid aggregation: numerical challenges to understanding the onset of oligomerisation Invited Speaker: Normand Mousseau Amyloid aggregation is associated with a number of degenerative diseases such as Alzheimer’s and Parkinson’s diseases. During amyloid formation, various proteins, that are often disordered as monomers, assemble into toxic beta-sheet dominated oligomers. This off-equilibrium dynamical process is difficult to characterize experimentally and even the basic properties of these oligomers remain unknown although some universal structural features have been demonstrated indirectly. To go beyond experimental limitations, it is useful to turn to computational atomistic simulations. These can provide much needed insights about the microscopic nature of the oligomerization process as well as provide support for interpreting experimental results. Yet, challenges are numerous in the computational side too, associate both with limitations of the computational tools and the gaps in the basic physics of this process. Building on work done within my group and numerous collaborators, I will discuss these challenges and identify some way to address them. [Preview Abstract] |
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