Thermotropic liquid crystals from biomacromolecules

Abstract

Complexation of biomacromolecules (e.g., nucleic acids, proteins, or viruses) with surfactants containing flexible alkyl tails, followed by dehydration, is shown to be a simple generic method for the production of thermotropic liquid crystals. The anhydrous smectic phases that result exhibit biomacromolecular sublayers intercalated between aliphatic hydrocarbon sublayers at or near room temperature. Both this and low transition temperatures to other phases enable the study and application of thermotropic liquid crystal phase behavior without thermal degradation of the biomolecular components.L iquid crystals (LCs) play an important role in biology because their essential characteristic, the combination of order and mobility, is a basic requirement for self-organization and structure formation in living systems (1-3). Thus, it is not surprising that the study of LCs emerged as a scientific discipline in part from biology and from the study of myelin figures, lipids, and cell membranes (4). These and the LC phases formed from many other biomolecules, including nucleic acids (5, 6), proteins (7,8), and viruses (9, 10), are classified as lyotropic, the general term applied to LC structures formed in water and stabilized by the distinctly biological theme of amphiphilic partitioning of hydrophilic and hydrophobic molecular components into separate domains. However, the principal thrust and achievement of the study of LCs has been in the science and application of thermotropic materials, structures, and phases in which molecules that are only weakly amphiphilic exhibit LC ordering by virtue of their steric molecular shape, flexibility, and/or weak intermolecular interactions [e.g., van der Waals and dipolar forces (11)]. These characteristics enable thermotropic LCs (TLCs) to adopt a wide variety of exotic phases and to exhibit dramatic and useful responses to external forces, including, for example, the electro-optic effects that have led to LC displays and the portable computing revolution. This general distinction between lyotropic LCs and TLCs suggests there may be interesting possibilities in the development of biomolecular or bioinspired LC systems in which the importance of amphiphilicity is reduced and the LC phases obtained are more thermotropic in nature. Such biological TLC materials are very appealing for several reasons. Most biomacromolecules were extensively characterized in aqueous environments, but in TLC phases, their solvent-free properties and functions could be investigated in a state in which no or only traces of water are present. Water exhibits a high dielectric constant and has the ability to form hydrogen bonds, greatly influencing the structure and functions of biomacromolecules or compromising electronic properties such as charge transport (12-15). Indeed, anhydrous TLC systems containing glycolipids (16-19), ferritin (20), and polylysine have been reported (21-23). However, a general approach to fabricating TLCs based on nucleic acids, polypeptides, proteins, and protein assemblies of larg...

Nematic DNA Thermotropic Liquid Crystals with Photoresponsive Mechanical Properties

“…The viscoelastic properties (elastic moduli and viscosity) of the DNA–AZO complexes correlate with the structure of DNA. In comparison to previous reports involving smectic DNA TLCs containing another type of surfactant, which lacks an aromatic moiety, we conclude that the introduction of an appropriate surfactant is important to modulate the mesophase structure and mechanical performance of the resulting complexes. Remarkably, upon irradiation with UV‐light, the E ‐ to Z‐ isomerization of the azobenzene moiety was successfully realized in the solvent‐free DNA‐AZO TLC materials.…”

“…These seminal findings enabled the development of powerful tools for drug delivery and gene therapy applications . Although most investigations of DNA LCs are currently limited to aqueous solutions, research examining anhydrous DNA thermotropic liquid crystals (TLCs) is gaining momentum owing to its relevance in DNA‐based optoelectronic applications . Recently, for example, a new class of smectic DNA TLCs has been generated by electrostatic complexation of single stranded (ss) oligonucleotides with surfactants containing two flexible alkyl chains .…”

Liquefaction of Biopolymers: Solvent-free Liquids and Liquid Crystals from Nucleic Acids and Proteins

“…16,21 Instead of PEG residues, we employed ammonium surfactants substituted with aliphatic alkyl chains yielding either DNA–surfactant liquids or mesophases. For the analysis of the DNA LCs, polarized optical microscopy (POM) can be used revealing the characteristic focal-conic textures of lamellar structures (Figure 2a,b).…”

Genetically Engineered Supercharged Polypeptide Fluids: Fast and Persistent Self‐Ordering Induced by Touch

“…Ab iological fluid system is introduced in which anionic polypeptides are complexed with cationic surfactants.T he resulting fluids exhibited very sensitive isotropic-nematic transition triggered by shear.T he formed liquid crystal was preserved after cessation of mechanical stimulus.S elf-ordering behavior of the material was achieved through water flowa nd finger pressing. [15][16][17] Fori nstance,aseries of biopolymer LCs and disordered liquids made of nucleic acids, [18,19] polypeptides, [20,21] proteins, [22,23] and virus particles [24,25] have been reported. [8][9][10][11][12][13][14] Forinstance,isotropic-nematic (I-N) and isotropic-smectic (I-S) transitions were realized in amphiphile micellar solutions [8][9][10][11] and thermotropic liquid crystals (LCs) [12,13] under steady shear flow.H owever,i ti sh ard to stabilize the resulting ordered phases after cessation of shear, [8][9][10][11][12][13] which may limit harnessing their favorable properties.Therefore,maintaining an ordered state induced from an isothermal disordered phase in polymer fluids in absence of an applied shear force remains an important challenge.…”

“…[15][16][17] Fori nstance,aseries of biopolymer LCs and disordered liquids made of nucleic acids, [18,19] polypeptides, [20,21] proteins, [22,23] and virus particles [24,25] have been reported. [15][16][17] Fori nstance,aseries of biopolymer LCs and disordered liquids made of nucleic acids, [18,19] polypeptides, [20,21] proteins, [22,23] and virus particles [24,25] have been reported.…”