Solvent‐Free Liquid Crystals and Liquids Based on Genetically Engineered Supercharged Polypeptides with High Elasticity

Abstract

or traditional organic liquid crystals. Therefore, the development of a general strategy for fabricating solvent-free ELP fl uids (liquid crystals and liquids) is an attractive goal.Genetic engineering as a recombinant protein synthesis technology affords a powerful tool for the synthesis of ELPs with predictable properties and biofunctionality. Engineered ELPs allow fabrication of desired sequences with high molecular weights combined with monodispersity, well-defi ned structures and chain lengths that are impossible to be achieved by chemical synthesis. [31][32][33] We demonstrate here the creation of genetically engineered ELPs based on the common pentameric repeat sequence (VPG X G) n found in tropoelastin by taking advantage of the fl exibility of the amino acid composition at the fourth position of that peptide motif. First, glutamic acid was introduced at this site of the repeat to transform the ELPs into supercharged polypeptides (SUPs, (VPG E G) n ). Then, green fl uorescent protein (GFP) was fused to the SUP for an additional level of functionality. Thus, a series of GFP-SUPs (GFP-(VPG E G) n ) with negative charges ranging from 9, over 18, 36, 72 to 144 (GFP-E9, GFP-E18, GFP-E36, GFP-E72, and GFP-E144) were expressed in E. coli (details in Figure S1-S3, Supporting Information). The purity and molecular weights of the products were confi rmed by polyacrylamide gel electrophoresis and matrix-assisted laser desorption/ionization time-of-fl ight mass spectrometry, respectively ( Figure S4 and S5, Supporting Information). Subsequently, the GFP-SUPs were complexed with cationic surfactants. This was inspired by previous work dealing with polyelectrolyte-surfactant complexation via electrostatic interactions. [34][35][36][37][38] In the context of proteins, complexation between cationized ferritin and anionic polymer surfactants yielded mesophases with a narrow temperature range. [ 37 ] Here we propose that the combination of negatively charged GFP-SUP with positively charged surfactants, followed by dehydration, can act as a simple generic scheme for producing solventfree GFP-SUP fl uids. In the present experiments, electrostatic interactions as the driving force couple these GFP-SUPs and surfactants into hybrid lamellar assemblies ( Figure 1 ), where the fl exible alkyl chains of surfactants suppress crystallization. [ 34,35 ] The anhydrous SUP-surfactant complexes exhibit non-Newtonian (smectic liquid crystal) and Newtonian (isotropic liquid) fl uid behaviors. The lengths of the SUP and surfactant are found to be extremely important in tuning the physical properties of the fl uids. We fi nd a high elasticity in the SUP mesophases when they are ordered in smectic layers. The elastic moduli of these phases are larger than the ones reported Biologically inspired peptide-based materials are of increasing interest for applications where biological function and structure are used outside of the natural context. [1][2][3][4][5][6][7][8][9][10] Among them, a specifi c class of repetitive polypeptides termed elasti...

A Guide to Design Functional Molecular Liquids with Tailorable Properties using Pyrene-Fluorescence as a Probe

“…Recently, solvent-free, nonvolatile, room-temperature functional molecular liquids (FMLs) 7 have emerged as a new generation of liquid materials. With an excellent processability, free deformability, and high thermal stability, FMLs have gained extensive interest in wide areas, including luminescence 8–14 , photoconduction 15–18 , molecular recognition 19, 20 , energy storage 21, 22 , and biological systems 23, 24 . Aiming for applications in flexible and bendable optoelectronics, we 8–10, 15, 16, 25, 26 and others 11–13, 21, 27–32 have developed the alkyl-π engineering strategy 33 to prepare various alkylated-π FMLs by attaching bulky and flexible alkyl chains to optoelectronically active π-conjugated units.…”

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

“…19 (a) Negatively charged SUPs combined with cationic surfactants. (b) POM image of SUP-surfactant smectic LC.…”

“…(d) Rheological investigation of the solvent-free SUP-surfactant fluids. Adapted with permission from ref (19). Copyright 2015 John Wiley & Sons, Inc.…”

“…14−17 We will briefly outline design, preparation, and application of solvent-free liquids ranging from nucleic acids 14−16 to proteins 17−19 to whole viruses 20,21 that have become accessible employing this simple and general protocol. In addition, this protocol has yielded access to solvent-free liquid crystals (LCs) 21−24 introducing ordering and fluidity by ionic self-assembly while retaining biological function 25 for biocatalysis, 26 bioelectronics, 27,28 and potentially biomedicine.…”

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.…”