Browsing by Author "Katsaras, John"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Biomembrane Structure and Material Properties Studied With Neutron Scattering
    Kinnun, Jacob J.; Scott, Haden L.; Ashkar, Rana; Katsaras, John (Frontiers, 2021-04-27)
    Cell membranes and their associated structures are dynamical supramolecular structures where different physiological processes take place. Detailed knowledge of their static and dynamic structures is therefore needed, to better understand membrane biology. The structure–function relationship is a basic tenet in biology and has been pursued using a range of different experimental approaches. In this review, we will discuss one approach, namely the use of neutron scattering techniques as applied, primarily, to model membrane systems composed of lipid bilayers. An advantage of neutron scattering, compared to other scattering techniques, is the differential sensitivity of neutrons to isotopes of hydrogen and, as a result, the relative ease of altering sample contrast by substituting protium for deuterium. This property makes neutrons an ideal probe for the study of hydrogen-rich materials, such as biomembranes. In this review article, we describe isotopic labeling studies of model and viable membranes, and discuss novel applications of neutron contrast variation in order to gain unique insights into the structure, dynamics, and molecular interactions of biological membranes. We specifically focus on how small-angle neutron scattering data is modeled using different contrast data and molecular dynamics simulations. We also briefly discuss neutron reflectometry and present a few recent advances that have taken place in neutron spin echo spectroscopy studies and the unique membrane mechanical data that can be derived from them, primarily due to new models used to fit the data.
  • Thumbnail Image
    Uncovering Structure-Property Relations in Biomimetic Lipid Membranes with Molecular Additives
    Lihiniya Kumarage, Teshani Omanthika (Virginia Tech, 2024-08-15)
    The lipid bilayer, the fundamental structure of cell membranes, exemplifies a highly adaptable molecular assembly with characteristics that have been fine-tuned through evolution to meet the diverse functional needs of cells. These bilayers must strike a delicate balance: they need to be sufficiently rigid to act as protective barriers, yet fluid enough to facilitate the diffusion of proteins and molecular clusters crucial for various biological processes. Owing to their multifunctional nature, lipid membranes are not only vital in biological contexts but also in numerous practical applications, such as artificial cells, drug-delivery nanocarriers, and biosensors. Both biological and synthetic lipid membranes frequently incorporate molecular or nanoscale additives that modify their properties through a range of mechanisms. Gaining a comprehensive understanding of how lipid membranes interact with these additives is an area of active research, particularly with the advent of advanced high-resolution characterization techniques that reveal both the static and dynamic behaviors of these systems. This dissertation investigates the impact of small molecular additives – specifically natural and synthetic sterols – on the structure, elasticity, and organization of biomimetic lipid membranes. Utilizing advanced scattering techniques and other methods, the research elucidates the intricate interplay between the membrane composition, structure, and elasticity. Key findings demonstrate that, unlike previous observations, cholesterol significantly affects the bending rigidity of lipid membranes regardless of chain unsaturation, when measured on mesoscopic length and time scales. Interestingly, the replacement of cholesterol with engineered molecules, comprised of a sterol unit that is chemically conjugated to one or both of the lipid chains, results in further enhancement in the membrane bending rigidity and mechanical stability, making them a promising additive for advanced liposomal drug delivery systems. Further studies on phase-separating membranes illustrate the effective use of sterol-modified lipids in regulating the formation and size of distinct lipid domains implicated in protein recruitment and biological function. This work advances the current understanding of membrane biophysics and paves the way for novel therapeutic strategies and biomaterial designs.