![Sample our Physical Sciences journals, sign in here to start your FREE access for 14 days]({"type":"image" , "src" : "/sda/110819/TOC-Subject-Sample-2021-Physical-Sciences.jpg"})
Abstract
In this paper, which is part of a collection in honour of Noel Clark’s remarkable career on liquid crystal (LC) and soft matter research, we present examples of biologically inspired systems, which form LC phases with their LC nature impacting biological function in cells or being important in biomedical applications. One area focuses on understanding network and bundle formation of cytoskeletal polyampholytes (filamentous actin, microtubules and neurofilaments (NFs)). Here, we describe studies on NFs, the intermediate filaments of neurons, which form open network nematic LC hydrogels in axons. Synchrotron small-angle-X-ray scattering studies of NF protein dilution experiments and NF hydrogels subjected to osmotic stress show that NF networks are stabilised by competing long-range repulsion and attractions mediated by the NF’s polyampholytic sidearms. The attractions are present both at very large inter-filament spacings, in the weak sidearm-interpenetrating regime, and at smaller inter-filament spacings, in the strong sidearm-interpenetrating regime. A second series of experiments will describe the structure and properties of cationic liposomes (CLs) complexed with nucleic acids (NAs). CL-NA complexes form liquid crystalline phases, which interact in a structure-dependent manner with cellular membranes enabling the design of complexes for efficient delivery of NA (DNA and RNA) in therapeutic applications.
Funding
CRS, JD, KKE and YL acknowledge the support by the US Department of Energy-Basic Energy Sciences [grant number DOE-DE-FG02-06ER46314] (self-assembly and interactions in filamentous protein systems), the US National Institutes of Health [grant number GM-59288] (biological activity studies in CL-DNA complexes) and the US National Science Foundation [grant number DMR-1101900] (protein phase behaviour). CL was funded by the Swedish Research Council (VR) and in part by the US DOE-BES. RB was supported by the Human Frontier Science Program Organization, the Israeli Science Foundation (Individual Research Grant [grant number 571/11]), the European Community’s 7th Framework Programme (293402), and the Sackler Institute for Biophysics at Tel-Aviv University. The X-ray diffraction work was carried out at the Stanford Synchrotron Radiation Laboratory (SSRL) beam lines 7.2 and 4.2. CRS acknowledges useful discussions with KAIST faculty where he has a WCU (World Class University) Visiting Professor of Physics appointment supported by the National Research Foundation of Korea funded by the Ministry of Education, Science and Technology [grant number R33-2008-000-10163-0].