title: Liquid crystal assemblies in biologically inspired systems.
abstract: In this paper, which is part of a collection in honor of Noel Clark's remarkable career on liquid crystal and soft matter research, we present examples of biologically inspired systems, which form liquid crystal (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). Here, we describe studies on neurofilaments (NFs), the intermediate filaments of neurons, which form open network nematic liquid crystal hydrogels in axons. Synchrotron small-angle-x-ray scattering studies of NF-protein dilution experiments and NF hydrogels subjected to osmotic stress show that neurofilament networks are stabilized by competing long-range repulsion and attractions mediated by the neurofilament's polyampholytic sidearms. The attractions are present both at very large interfilament spacings, in theweak sidearm-interpenetrating regime, and at smaller interfilament spacings, in thestrong 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 nucleic acid (DNA, RNA) in therapeutic applications.
authors.affiliation: Materials, Physics, and Molecular, Cellular, & Developmental Biology Departments, University of California, Santa Barbara, CA 93106, USA.
authors.forename: Cyrus R
authors.initials: CR
authors.lastname: Safinya
authors.affiliation: Materials, Physics, and Molecular, Cellular, & Developmental Biology Departments, University of California, Santa Barbara, CA 93106, USA ; Chemistry and Biochemistry Department, University of California, Santa Barbara, CA 93106, USA.
authors.forename: Joanna
authors.initials: J
authors.lastname: Deek
authors.affiliation: Materials, Physics, and Molecular, Cellular, & Developmental Biology Departments, University of California, Santa Barbara, CA 93106, USA.
authors.forename: Roy
authors.initials: R
authors.lastname: Beck
authors.affiliation: Materials, Physics, and Molecular, Cellular, & Developmental Biology Departments, University of California, Santa Barbara, CA 93106, USA.
authors.forename: Jayna B
authors.initials: JB
authors.lastname: Jones
authors.affiliation: Materials, Physics, and Molecular, Cellular, & Developmental Biology Departments, University of California, Santa Barbara, CA 93106, USA.
authors.forename: Cecilia
authors.initials: C
authors.lastname: Leal
authors.affiliation: Materials, Physics, and Molecular, Cellular, & Developmental Biology Departments, University of California, Santa Barbara, CA 93106, USA.
authors.forename: Kai K
authors.initials: KK
authors.lastname: Ewert
authors.affiliation: Materials Research Laboratory, University of California, Santa Barbara, CA 93106, USA.
authors.forename: Youli
authors.initials: Y
authors.lastname: Li
keywords: DNA; Neurofilaments; RNA; gyroid cubic phases; hexagonal liquid crystals; lamellar liquid crystals; lipids; nematic hydrogels; small-angle-x-ray-scattering (SAXS)