1
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Fernando KS, Jahanmir G, Unarta IC, Chau Y. Multiscale Computational Framework for the Liquid-Liquid Phase Separation of Intrinsically Disordered Proteins. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:7607-7619. [PMID: 38546977 DOI: 10.1021/acs.langmuir.4c00209] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/10/2024]
Abstract
The reversible assembly of intrinsically disordered proteins (IDPs) to form membraneless organelles (MLOs) is a fundamental process involved in the spatiotemporal regulation in living cells. MLOs formed via liquid-liquid phase separation (LLPS) serve as molecule-enhancing hubs to regulate cell functions. Owing to the complexity and dynamic nature of the protein assembly via a network of weak inter- and intra-molecular interactions, it is challenging to describe and predict the LLPS behavior. We have developed a multiscale computational model for IDPs, using the fused in sarcoma (FUS) protein and its variants as illustrative examples. To simplify the description of protein, FUS is represented as a linear chain of stickers interspaced by spacers, as inspired by the associative polymer theory. Low-complexity aromatic-rich kinked segments (LARKS) available in FUS were identified using LARKSdb and represented as "stickers". The pairwise potential energies of each pair of stickers and their β-sheet-forming propensity were estimated via molecular docking and all atomistic molecular dynamics (AA-MD) simulations. Subsequently, FUS chains were randomly positioned in a cubic lattice as coarse-grained (CG) beads, with the bead assignment based on the Kuhn length estimation of stickers and spacers. Stochastic FUS movements were modeled by Monte Carlo (MC) simulations. In addition to the Metropolis algorithm, discretized pair potential distributions between stickers were considered in the move acceptance criteria. The chosen pair potential represents one of the possible binding energy states, with its probability determined by the frequency of the binding energy distribution histogram. The fluctuations of averaged radial distribution functions (RDFs) in successive MC trial move intervals of equilibrated lattice MC simulations were used to indicate the dynamic nature of assembly/disassembly of the protein chains. This multiscale computational framework provides an economical and efficient way of predicting and describing the LLPS behavior of IDPs.
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Affiliation(s)
- Kalindu S Fernando
- Department of Chemical and Biological Engineering, The Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, Hong Kong SAR, China
| | - Ghodsiehsadat Jahanmir
- Department of Chemical and Biological Engineering, The Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, Hong Kong SAR, China
| | - Ilona C Unarta
- Department of Chemistry, University of Wisconsin─Madison, Madison, Wisconsin 53706, United States
| | - Ying Chau
- Department of Chemical and Biological Engineering, The Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, Hong Kong SAR, China
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2
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Khare E, Grewal DS, Buehler MJ. Bond clusters control rupture force limit in shear loaded histidine-Ni 2+ metal-coordinated proteins. NANOSCALE 2023; 15:8578-8588. [PMID: 37092811 DOI: 10.1039/d3nr01287e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Dynamic noncovalent interactions are pivotal to the structure and function of biological proteins and have been used in bioinspired materials for similar roles. Metal-coordination bonds, in particular, are especially tunable and enable control over static and dynamic properties when incorporated into synthetic materials. Despite growing efforts to engineer metal-coordination bonds to produce strong, tough, and self-healing materials, the systematic characterization of the exact contribution of these bonds towards mechanical strength and the effect of geometric arrangements is missing, limiting the full design potential of these bonds. In this work, we engineer the cooperative rupture of metal-coordination bonds to increase the rupture strength of metal-coordinated peptide dimers. Utilizing all-atom steered molecular dynamics simulations on idealized bidentate histidine-Ni2+ coordinated peptides, we show that histidine-Ni2+ bonds can rupture cooperatively in groups of two to three bonds. We find that there is a strength limit, where adding additional coordination bonds does not contribute to the additional increase in the protein rupture strength, likely due to the highly heterogeneous rupture behavior exhibited by the coordination bonds. Further, we show that this coordination bond limit is also found natural metal-coordinated biological proteins. Using these insights, we quantitatively suggest how other proteins can be rationally designed with dynamic noncovalent interactions to exhibit cooperative bond breaking behavior. Altogether, this work provides a quantitative analysis of the cooperativity and intrinsic strength limit for metal-coordination bonds with the aim of advancing clear guiding molecular principles for the mechanical design of metal-coordinated materials.
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Affiliation(s)
- Eesha Khare
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
- Laboratory for Atomistic and Molecular Mechanics, Massachusetts Institute of Technology, 33 Massachusetts Avenue, Cambridge, MA 02139, USA.
| | - Darshdeep S Grewal
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
- Laboratory for Atomistic and Molecular Mechanics, Massachusetts Institute of Technology, 33 Massachusetts Avenue, Cambridge, MA 02139, USA.
| | - Markus J Buehler
- Laboratory for Atomistic and Molecular Mechanics, Massachusetts Institute of Technology, 33 Massachusetts Avenue, Cambridge, MA 02139, USA.
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3
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Zhang T, Peruch F, Weber A, Bathany K, Fauquignon M, Mutschler A, Schatz C, Garbay B. Solution behavior and encapsulation properties of fatty acid-elastin-like polypeptide conjugates. RSC Adv 2023; 13:2190-2201. [PMID: 36712617 PMCID: PMC9835928 DOI: 10.1039/d2ra06603c] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2022] [Accepted: 12/21/2022] [Indexed: 01/13/2023] Open
Abstract
Developing new biomaterials is an active research area owing to their applications in regenerative medicine, tissue engineering and drug delivery. Elastin-like polypeptides (ELPs) are good candidates for these applications because they are biosourced, biocompatible and biodegradable. With the aim of developing ELP-based micelles for drug delivery applications we have synthesized 15 acyl-ELP compounds by conjugating myristic, palmitic, stearic, oleic or linoleic acid to the N-terminus of three ELPs differing in molar mass. The ELP-fatty acid conjugates have interesting solution behavior. They form micelles at low temperatures and aggregate above the cloud point temperature (Tcp). The critical micelle concentration depends on the fatty acid nature while the micelle size is mainly determined by the ELP block length. We were able to show that ELPs were better hydrated in the micelles than in their individual state in solution. The micelles are stable in phosphate-buffered saline at temperatures below the Tcp, which can vary between 20 °C and 38 °C depending on the length or hydrophilicity of the ELP. Acyl-ELP micelles were loaded with the small hydrophobic molecule Nile red. The encapsulation efficiency and release kinetics showed that the best loading conditions were achieved with the largest ELP conjugated to stearic acid.
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Affiliation(s)
- Tingting Zhang
- Univ. Bordeaux, CNRS, Bordeaux INP, LCPO UMR 5629F-33600 PessacFrance
| | - Frédéric Peruch
- Univ. Bordeaux, CNRS, Bordeaux INP, LCPO UMR 5629F-33600 PessacFrance
| | - Amélie Weber
- Univ. Bordeaux, CNRS, Bordeaux INP, LCPO UMR 5629F-33600 PessacFrance
| | - Katell Bathany
- Univ. Bordeaux, CNRS, Bordeaux INP, CBMN UMR 5248F-33600 PessacFrance
| | - Martin Fauquignon
- Univ. Bordeaux, CNRS, Bordeaux INP, LCPO UMR 5629F-33600 PessacFrance
| | - Angela Mutschler
- Univ. Bordeaux, CNRS, Bordeaux INP, LCPO UMR 5629F-33600 PessacFrance
| | - Christophe Schatz
- Univ. Bordeaux, CNRS, Bordeaux INP, LCPO UMR 5629F-33600 PessacFrance
| | - Bertrand Garbay
- Univ. Bordeaux, CNRS, Bordeaux INP, LCPO UMR 5629F-33600 PessacFrance
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4
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Structural Breakdown of Collagen Type I Elastin Blend Polymerization. Polymers (Basel) 2022; 14:polym14204434. [PMID: 36298012 PMCID: PMC9611167 DOI: 10.3390/polym14204434] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Revised: 10/17/2022] [Accepted: 10/18/2022] [Indexed: 11/17/2022] Open
Abstract
Biopolymer blends are advantageous materials with novel properties that may show performances way beyond their individual constituents. Collagen elastin hybrid gels are a new representative of such materials as they employ elastin’s thermo switching behavior in the physiological temperature regime. Although recent studies highlight the potential applications of such systems, little is known about the interaction of collagen and elastin fibers during polymerization. In fact, the final network structure is predetermined in the early and mostly arbitrary association of the fibers. We investigated type I collagen polymerized with bovine neck ligament elastin with up to 33.3 weight percent elastin and showed, by using a plate reader, zeta potential and laser scanning microscopy (LSM) experiments, that elastin fibers bind in a lateral manner to collagen fibers. Our plate reader experiments revealed an elastin concentration-dependent increase in the polymerization rate, although the rate increase was greatest at intermediate elastin concentrations. As elastin does not significantly change the structural metrics pore size, fiber thickness or 2D anisotropy of the final gel, we are confident to conclude that elastin is incorporated homogeneously into the collagen fibers.
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5
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Dautel DR, Champion JA. Self-Assembly of Functional Protein Nanosheets from Thermoresponsive Bolaamphiphiles. Biomacromolecules 2022; 23:3612-3620. [PMID: 36018255 DOI: 10.1021/acs.biomac.2c00525] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Nanosheets are two-dimensional materials, less than 100 nm thick, that can be used for separations, biosensing, and biocatalysis. Nanosheets can be made from inorganic and organic materials such as graphene, polymers, and proteins. Here, we report the self-assembly of nanosheets under aqueous conditions from functional proteins. The nanosheets are synthesized from two fusion proteins held together by high-affinity interactions of two leucine zippers to form bolaamphiphiles. The hydrophobic domain, ZR-ELP-ZR, contains the thermoresponsive elastin-like peptide (ELP) flanked by arginine-rich leucine zippers (ZR), each of which binds the hydrophilic fusion protein, globule-ZE, via the glutamate-rich leucine zipper (ZE) fused to a functional, globular protein. Nanosheets form when the proteins are mixed at 4 °C in aqueous solutions and then heated to 25 °C as the container is rotated end-over-end causing expansion and contraction of the air-water interface. The nanosheets are robust with respect to the choice of globular protein and can incorporate small fluorescent proteins that are less than 30 kDa as well as large enzymes, such as 80 kDa malate synthase G. Upon incorporation into nanosheets, enzymes retain more than 70% of their original activity, demonstrating the potential of protein nanosheets to be used for biosensing or biocatalytic applications.
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Affiliation(s)
- Dylan R Dautel
- School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, 950 Atlantic Drive NW, Atlanta, Georgia 30332, United States
| | - Julie A Champion
- School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, 950 Atlantic Drive NW, Atlanta, Georgia 30332, United States
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6
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Sahin C, Østerlund EC, Österlund N, Costeira-Paulo J, Pedersen JN, Christiansen G, Nielsen J, Grønnemose AL, Amstrup SK, Tiwari MK, Rao RSP, Bjerrum MJ, Ilag LL, Davies MJ, Marklund EG, Pedersen JS, Landreh M, Møller IM, Jørgensen TJD, Otzen DE. Structural Basis for Dityrosine-Mediated Inhibition of α-Synuclein Fibrillization. J Am Chem Soc 2022; 144:11949-11954. [PMID: 35749730 PMCID: PMC9284551 DOI: 10.1021/jacs.2c03607] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
![]()
α-Synuclein
(α-Syn) is an intrinsically disordered
protein which self-assembles into highly organized β-sheet structures
that accumulate in plaques in brains of Parkinson’s disease
patients. Oxidative stress influences α-Syn structure and self-assembly;
however, the basis for this remains unclear. Here we characterize
the chemical and physical effects of mild oxidation on monomeric α-Syn
and its aggregation. Using a combination of biophysical methods, small-angle
X-ray scattering, and native ion mobility mass spectrometry, we find
that oxidation leads to formation of intramolecular dityrosine cross-linkages
and a compaction of the α-Syn monomer by a factor of √2.
Oxidation-induced compaction is shown to inhibit ordered self-assembly
and amyloid formation by steric hindrance, suggesting an important
role of mild oxidation in preventing amyloid formation.
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Affiliation(s)
- Cagla Sahin
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Gustav Wieds Vej 14, DK-8000 Aarhus C, Denmark.,Department of Molecular Biology and Genetics, Aarhus University, Universitetsbyen 81, DK-8000 Aarhus C, Denmark
| | - Eva Christina Østerlund
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark
| | - Nicklas Österlund
- Department of Biochemistry and Biophysics, Stockholm University, SE-114 18 Stockholm, Sweden
| | - Joana Costeira-Paulo
- Department of Chemistry - BMC, BMC - Uppsala University, Box 576, SE-751 23 Uppsala, Sweden
| | - Jannik Nedergaard Pedersen
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Gustav Wieds Vej 14, DK-8000 Aarhus C, Denmark
| | - Gunna Christiansen
- Department of Health Science and Technology, Medical Microbiology and Immunology, Aalborg University, Fredrik Bajers Vej 3b, DK-9220 Aalborg Ø, Denmark
| | - Janni Nielsen
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Gustav Wieds Vej 14, DK-8000 Aarhus C, Denmark
| | - Anne Louise Grønnemose
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Gustav Wieds Vej 14, DK-8000 Aarhus C, Denmark.,Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark
| | - Søren Kirk Amstrup
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Gustav Wieds Vej 14, DK-8000 Aarhus C, Denmark.,Department of Molecular Biology and Genetics, Aarhus University, Universitetsbyen 81, DK-8000 Aarhus C, Denmark
| | - Manish K Tiwari
- Department Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark
| | - R Shyama Prasad Rao
- Biostatistics and Bioinformatics Division, Yenepoya Research Center, Yenepoya University, Mangaluru-575018, Karnataka, India
| | - Morten Jannik Bjerrum
- Department Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark
| | - Leopold L Ilag
- Department of Materials and Environmental Chemistry, Stockholm University, SE-114 18 Stockholm, Sweden
| | - Michael J Davies
- Department of Biomedical Sciences, University of Copenhagen, Blegdamsvej 3B, DK-2200 Copenhagen N, Denmark
| | - Erik G Marklund
- Department of Chemistry - BMC, BMC - Uppsala University, Box 576, SE-751 23 Uppsala, Sweden
| | - Jan Skov Pedersen
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Gustav Wieds Vej 14, DK-8000 Aarhus C, Denmark.,Department of Chemistry, Aarhus University, Gustav Wieds Vej 14, DK-8000 Aarhus C, Denmark
| | - Michael Landreh
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Solnavägen 9, SE-171 65 Solna, Sweden
| | - Ian Max Møller
- Department of Molecular Biology and Genetics, Aarhus University, Forsøgsvej 1, DK-4200 Slagelse, Denmark
| | - Thomas J D Jørgensen
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark
| | - Daniel Erik Otzen
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Gustav Wieds Vej 14, DK-8000 Aarhus C, Denmark.,Department of Molecular Biology and Genetics, Aarhus University, Universitetsbyen 81, DK-8000 Aarhus C, Denmark
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7
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The Effects of Proline Isomerization on the Solvation Behavior of Elastin‐Like Polypeptides in Water‐Ethanol Mixtures. Macromol Rapid Commun 2022; 43:e2100907. [DOI: 10.1002/marc.202100907] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Revised: 02/02/2022] [Indexed: 11/07/2022]
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8
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Zhao Y, Kremer K. Proline Isomerization Regulates the Phase Behavior of Elastin-Like Polypeptides in Water. J Phys Chem B 2021; 125:9751-9756. [PMID: 34424695 PMCID: PMC8419842 DOI: 10.1021/acs.jpcb.1c04779] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Responsiveness of polypeptides and polymers in aqueous solution plays an important role in biomedical applications and in designing advanced functional materials. Elastin-like polypeptides (ELPs) are a well-known class of synthetic intrinsically disordered proteins (IDPs), which exhibit a lower critical solution temperature (LCST) in pure water and in aqueous solutions. Here, we compare the influence of cis/trans proline isomerization on the phase behavior of single ELPs in pure water. Our results reveal that proline isomerization tunes the conformational behavior of ELPs while keeping the transition temperature unchanged. We find that the presence of the cis isomers facilitates compact structures by preventing peptide-water hydrogen bonding while promoting intramolecular interactions. In other words, the LCST transition of ELPs with all proline residues in the cis state occurs with almost no noticeable conformational change.
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Affiliation(s)
- Yani Zhao
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Kurt Kremer
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
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9
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Hossain MS, Maller C, Dai Y, Nangia S, Mozhdehi D. Non-canonical lipoproteins with programmable assembly and architecture. Chem Commun (Camb) 2020; 56:10281-10284. [PMID: 32734969 DOI: 10.1039/d0cc03271a] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The substrate promiscuity of an acyltransferase is leveraged to synthesize artificial lipoproteins bearing a non-canonical PTM (ncPTM). The non-canonical functionality of these lipoproteins results in a distinctive hysteretic assembly-absent from the canonical lipoproteins-and is used to prepare hybrid multiblock materials with precise and programmable patterns of amphiphilicity. This study demonstrates the promise of expanding the repertoire of PTMs for the development of nanomaterials with a unique assembly and function.
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Affiliation(s)
- Md Shahadat Hossain
- Department of Chemistry, 1-014 Center for Science and Technology, Syracuse University, Syracuse, NY 13244, USA.
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10
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Dzuricky M, Rogers BA, Shahid A, Cremer PS, Chilkoti A. De novo engineering of intracellular condensates using artificial disordered proteins. Nat Chem 2020; 12:814-825. [PMID: 32747754 DOI: 10.1038/s41557-020-0511-7] [Citation(s) in RCA: 127] [Impact Index Per Article: 31.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2019] [Accepted: 06/18/2020] [Indexed: 11/09/2022]
Abstract
Phase separation of intrinsically disordered proteins (IDPs) is a remarkable feature of living cells to dynamically control intracellular partitioning. Despite the numerous new IDPs that have been identified, progress towards rational engineering in cells has been limited. To address this limitation, we systematically scanned the sequence space of native IDPs and designed artificial IDPs (A-IDPs) with different molecular weights and aromatic content, which exhibit variable condensate saturation concentrations and temperature cloud points in vitro and in cells. We created A-IDP puncta using these simple principles, which are capable of sequestering an enzyme and whose catalytic efficiency can be manipulated by the molecular weight of the A-IDP. These results provide a robust engineered platform for creating puncta with new, phase-separation-mediated control of biological function in living cells.
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Affiliation(s)
- Michael Dzuricky
- Department of Biomedical Engineering, Duke University, Durham, NC, USA
| | - Bradley A Rogers
- Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA, USA
| | - Abdulla Shahid
- Department of Computer Science, Duke University, Durham, NC, USA.,Department of Biology, Duke University, Durham, NC, USA
| | - Paul S Cremer
- Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA, USA
| | - Ashutosh Chilkoti
- Department of Biomedical Engineering, Duke University, Durham, NC, USA.
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11
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Baul U, Bley M, Dzubiella J. Thermal Compaction of Disordered and Elastin-like Polypeptides: A Temperature-Dependent, Sequence-Specific Coarse-Grained Simulation Model. Biomacromolecules 2020; 21:3523-3538. [DOI: 10.1021/acs.biomac.0c00546] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Upayan Baul
- Applied Theoretical Physics—Computational Physics, Physikalisches Institut, Albert-Ludwigs-Universität Freiburg, Hermann-Herder Strasse 3, D-79104 Freiburg, Germany
| | - Michael Bley
- Applied Theoretical Physics—Computational Physics, Physikalisches Institut, Albert-Ludwigs-Universität Freiburg, Hermann-Herder Strasse 3, D-79104 Freiburg, Germany
| | - Joachim Dzubiella
- Applied Theoretical Physics—Computational Physics, Physikalisches Institut, Albert-Ludwigs-Universität Freiburg, Hermann-Herder Strasse 3, D-79104 Freiburg, Germany
- Cluster of Excellence livMatS@FIT—Freiburg Center for Interactive Materials and Bioinspired Technologies, Albert-Ludwigs-Universität Freiburg, Georges-Köhler-Allee 105, D-79110 Freiburg, Germany
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12
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Goetzfried MA, Vogele K, Mückl A, Kaiser M, Holland NB, Simmel FC, Pirzer T. Periodic Operation of a Dynamic DNA Origami Structure Utilizing the Hydrophilic-Hydrophobic Phase-Transition of Stimulus-Sensitive Polypeptides. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2019; 15:e1903541. [PMID: 31531953 DOI: 10.1002/smll.201903541] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Revised: 08/20/2019] [Indexed: 06/10/2023]
Abstract
Dynamic DNA nanodevices are designed to perform structure-encoded motion actuated by a variety of different physicochemical stimuli. In this context, hybrid devices utilizing other components than DNA have the potential to considerably expand the library of functionalities. Here, the reversible reconfiguration of a DNA origami structure using the stimulus sensitivity of elastin-like polypeptides is reported. To this end, a rectangular sheet made using the DNA origami technique is functionalized with these peptides and by applying changes in salt concentration the hydrophilic-hydrophobic phase transition of these peptides actuate the folding of the structure. The on-demand and reversible switching of the rectangle is driven by externally imposed temperature oscillations and appears at specific transition temperatures. Using transmission electron microscopy, it is shown that the structure exhibits distinct conformational states with different occupation probabilities, which are dependent on structure-intrinsic parameters such as the local number and the arrangement of the peptides on the rectangle. It is also shown through ensemble fluorescence resonance energy transfer spectroscopy that the transition temperature and thus the thermodynamics of the rectangle-peptide system depends on the stimuli salt concentration and temperature, as well as on the intrinsic parameters.
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Affiliation(s)
- Marisa A Goetzfried
- Physics of Synthetic Biological Systems-E14, Physics Department and ZNN, Technische Universität München, 85748, Garching, Germany
| | - Kilian Vogele
- Physics of Synthetic Biological Systems-E14, Physics Department and ZNN, Technische Universität München, 85748, Garching, Germany
| | - Andrea Mückl
- Physics of Synthetic Biological Systems-E14, Physics Department and ZNN, Technische Universität München, 85748, Garching, Germany
| | - Marcus Kaiser
- Operations Research, Department of Mathematics, Technische Universität München, 80333, München, Germany
| | - Nolan B Holland
- Department of Chemical and Biomedical Engineering, Cleveland State University, 2121 Euclid Avenue, Cleveland, OH, 44115, USA
| | - Friedrich C Simmel
- Physics of Synthetic Biological Systems-E14, Physics Department and ZNN, Technische Universität München, 85748, Garching, Germany
| | - Tobias Pirzer
- Physics of Synthetic Biological Systems-E14, Physics Department and ZNN, Technische Universität München, 85748, Garching, Germany
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13
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Kuna M, Mahdi F, Chade AR, Bidwell GL. Molecular Size Modulates Pharmacokinetics, Biodistribution, and Renal Deposition of the Drug Delivery Biopolymer Elastin-like Polypeptide. Sci Rep 2018; 8:7923. [PMID: 29784932 PMCID: PMC5962569 DOI: 10.1038/s41598-018-24897-9] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2018] [Accepted: 04/11/2018] [Indexed: 11/25/2022] Open
Abstract
Elastin-like polypeptides (ELP) are engineered proteins that consist of repetitions of a five amino acid motif, and their composition is easily modified to adjust their physical properties and attach therapeutics. Because of the repetitive nature of the ELP sequence, polymer size is particularly amenable to manipulation. ELP fusion proteins are being actively developed as therapeutics for many disease applications, and how the ELP size and shape affects its pharmacokinetics and biodistribution is a critical question for the general field of ELP drug delivery. To address this, we generated a library of ELPs ranging in size from 25 kDa to 110 kDa. Terminal plasma half-life was directly proportional to polymer size, and organ biodistribution was also size dependent. The kidneys accumulated the highest levels of ELP of all sizes, followed by the liver. Within the kidney, most ELP was found in the proximal tubule, but intra-renal localization shifted from exclusively cortical to a mixture of cortical and medullary as ELP size increased.
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Affiliation(s)
- Marija Kuna
- Department of Cell and Molecular Biology, University of Mississippi Medical Center, Jackson, MS, USA
| | - Fakhri Mahdi
- Department of Neurology, University of Mississippi Medical Center, Jackson, MS, USA
| | - Alejandro R Chade
- Department of Physiology and Biophysics, University of Mississippi Medical Center, Jackson, MS, USA.,Department of Medicine, University of Mississippi Medical Center, Jackson, MS, USA.,Department of Radiology, University of Mississippi Medical Center, Jackson, MS, USA
| | - Gene L Bidwell
- Department of Cell and Molecular Biology, University of Mississippi Medical Center, Jackson, MS, USA. .,Department of Neurology, University of Mississippi Medical Center, Jackson, MS, USA.
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14
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Costa SA, Simon JR, Amiram M, Tang L, Zauscher S, Brustad EM, Isaacs FJ, Chilkoti A. Photo-Crosslinkable Unnatural Amino Acids Enable Facile Synthesis of Thermoresponsive Nano- to Microgels of Intrinsically Disordered Polypeptides. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2018; 30:10.1002/adma.201704878. [PMID: 29226470 PMCID: PMC5942558 DOI: 10.1002/adma.201704878] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2017] [Revised: 10/01/2017] [Indexed: 05/20/2023]
Abstract
Hydrogel particles are versatile materials that provide exquisite, tunable control over the sequestration and delivery of materials in pharmaceutics, tissue engineering, and photonics. The favorable properties of hydrogel particles depend largely on their size, and particles ranging from nanometers to micrometers are used in different applications. Previous studies have only successfully fabricated these particles in one specific size regime and required a variety of materials and fabrication methods. A simple yet powerful system is developed to easily tune the size of polypeptide-based, thermoresponsive hydrogel particles, from the nano- to microscale, using a single starting material. Particle size is controlled by the self-assembly and unique phase transition behavior of elastin-like polypeptides in bulk and within microfluidic-generated droplets. These particles are then stabilized through ultraviolet irradiation of a photo-crosslinkable unnatural amino acid (UAA) cotranslationally incorporated into the parent polypeptide. The thermoresponsive property of these particles provides an active mechanism for actuation and a dynamic responsive to the environment. This work represents a fundamental advance in the generation of crosslinked biomaterials, especially in the form of soft matter colloids, and is one of the first demonstrations of successful use of UAAs in generating a novel material.
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Affiliation(s)
- Simone A Costa
- NSF Research Triangle Materials Research Science and Engineering Center, Department of Biomedical Engineering, Duke University, Durham, NC, 27708, USA
| | - Joseph R Simon
- NSF Research Triangle Materials Research Science and Engineering Center, Department of Biomedical Engineering, Duke University, Durham, NC, 27708, USA
| | - Miriam Amiram
- The Avram and Stella Goldstein-Goren Department of Biotechnology Engineering, Ben-Gurion University, P.O 653, Beer-Sheva, 8410501, Israel
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT, 06520, USA
| | - Lei Tang
- NSF Research Triangle Materials Research Science and Engineering Center, Department of Mechanical Engineering and Materials Science, Duke University, Durham, NC, 27708, USA
| | - Stefan Zauscher
- NSF Research Triangle Materials Research Science and Engineering Center, Department of Mechanical Engineering and Materials Science, Duke University, Durham, NC, 27708, USA
| | - Eric M Brustad
- NSF Research Triangle Materials Research Science and Engineering Center, Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Farren J Isaacs
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT, 06520, USA
| | - Ashutosh Chilkoti
- NSF Research Triangle Materials Research Science and Engineering Center, Department of Biomedical Engineering, Duke University, Durham, NC, 27708, USA
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15
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Luginbuhl KM, Mozhdehi D, Dzuricky M, Yousefpour P, Huang FC, Mayne NR, Buehne KL, Chilkoti A. Recombinant Synthesis of Hybrid Lipid-Peptide Polymer Fusions that Self-Assemble and Encapsulate Hydrophobic Drugs. Angew Chem Int Ed Engl 2017; 56:13979-13984. [PMID: 28879687 PMCID: PMC5909378 DOI: 10.1002/anie.201704625] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2017] [Revised: 08/14/2017] [Indexed: 11/06/2022]
Abstract
Inspired by biohybrid molecules that are synthesized in Nature through post-translational modification (PTM), we have exploited a eukaryotic PTM to recombinantly synthesize lipid-polypeptide hybrid materials. By co-expressing yeast N-myristoyltransferase with an elastin-like polypeptide (ELP) fused to a short recognition sequence in E. coli, we show robust and high-yield modification of the ELP with myristic acid. The ELP's reversible phase behavior is retained upon myristoylation and can be tuned to span a 30-60 °C. Myristoylated ELPs provide a versatile platform for genetically pre-programming self-assembly into micelles of varied size and shape. Their lipid cores can be loaded with hydrophobic small molecules by passive diffusion. Encapsulated doxorubicin and paclitaxel exhibit cytotoxic effects on 4T1 and PC3-luc cells, respectively, with potencies similar to chemically conjugated counterparts, and longer plasma circulation than free drug upon intravenous injection in mice.
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Affiliation(s)
- Kelli M Luginbuhl
- Department of Biomedical Engineering, Duke University, 1427 FCIEMAS, Box 90281, USA
- NSF Research Triangle Materials Research Science and Engineering Center, Department of Biomedical Engineering, Duke University, Durham, NC, 27708, USA
| | - Davoud Mozhdehi
- Department of Biomedical Engineering, Duke University, 1427 FCIEMAS, Box 90281, USA
- NSF Research Triangle Materials Research Science and Engineering Center, Department of Biomedical Engineering, Duke University, Durham, NC, 27708, USA
| | - Michael Dzuricky
- Department of Biomedical Engineering, Duke University, 1427 FCIEMAS, Box 90281, USA
- NSF Research Triangle Materials Research Science and Engineering Center, Department of Biomedical Engineering, Duke University, Durham, NC, 27708, USA
| | - Parisa Yousefpour
- Department of Biomedical Engineering, Duke University, 1427 FCIEMAS, Box 90281, USA
| | - Fred C Huang
- Department of Biomedical Engineering, Duke University, 1427 FCIEMAS, Box 90281, USA
| | - Nicholas R Mayne
- Department of Biomedical Engineering, Duke University, 1427 FCIEMAS, Box 90281, USA
| | - Kristen L Buehne
- Department of Biomedical Engineering, Duke University, 1427 FCIEMAS, Box 90281, USA
| | - Ashutosh Chilkoti
- Department of Biomedical Engineering, Duke University, 1427 FCIEMAS, Box 90281, USA
- NSF Research Triangle Materials Research Science and Engineering Center, Department of Biomedical Engineering, Duke University, Durham, NC, 27708, USA
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16
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Luginbuhl KM, Mozhdehi D, Dzuricky M, Yousefpour P, Huang FC, Mayne NR, Buehne KL, Chilkoti A. Recombinant Synthesis of Hybrid Lipid–Peptide Polymer Fusions that Self‐Assemble and Encapsulate Hydrophobic Drugs. Angew Chem Int Ed Engl 2017. [DOI: 10.1002/ange.201704625] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Kelli M. Luginbuhl
- Department of Biomedical Engineering Duke University 1427 FCIEMAS, Box 90281 USA
- NSF Research Triangle Materials Research Science and Engineering Center Department of Biomedical Engineering Duke University Durham NC 27708 USA
| | - Davoud Mozhdehi
- Department of Biomedical Engineering Duke University 1427 FCIEMAS, Box 90281 USA
- NSF Research Triangle Materials Research Science and Engineering Center Department of Biomedical Engineering Duke University Durham NC 27708 USA
| | - Michael Dzuricky
- Department of Biomedical Engineering Duke University 1427 FCIEMAS, Box 90281 USA
- NSF Research Triangle Materials Research Science and Engineering Center Department of Biomedical Engineering Duke University Durham NC 27708 USA
| | - Parisa Yousefpour
- Department of Biomedical Engineering Duke University 1427 FCIEMAS, Box 90281 USA
| | - Fred C. Huang
- Department of Biomedical Engineering Duke University 1427 FCIEMAS, Box 90281 USA
| | - Nicholas R. Mayne
- Department of Biomedical Engineering Duke University 1427 FCIEMAS, Box 90281 USA
| | - Kristen L. Buehne
- Department of Biomedical Engineering Duke University 1427 FCIEMAS, Box 90281 USA
| | - Ashutosh Chilkoti
- Department of Biomedical Engineering Duke University 1427 FCIEMAS, Box 90281 USA
- NSF Research Triangle Materials Research Science and Engineering Center Department of Biomedical Engineering Duke University Durham NC 27708 USA
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17
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Dong Z, Kennedy E, Hokmabadi M, Timp G. Discriminating Residue Substitutions in a Single Protein Molecule Using a Sub-nanopore. ACS NANO 2017; 11:5440-5452. [PMID: 28538092 DOI: 10.1021/acsnano.6b08452] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
It is now possible to create, in a thin inorganic membrane, a single, sub-nanometer-diameter pore (i.e., a sub-nanopore) about the size of an amino acid residue. To explore the prospects for sequencing protein with it, measurements of the force and current were performed as two denatured histones, which differed by four amino acid residue substitutions, were impelled systematically through the sub-nanopore one at a time using an atomic force microscope. The force measurements revealed that once the denatured protein, stabilized by sodium dodecyl sulfate (SDS), translocated through the sub-nanopore, a disproportionately large force was required to pull it back. This was interpreted to mean that the SDS was cleaved from the protein during the translocation. The force measurements also exposed a dichotomy in the translocation kinetics: either the molecule slid nearly frictionlessly through the pore or it slipped-and-stuck. When it slid frictionlessly, regardless of whether the molecule was pulled N-terminus or C-terminus first through the pore, regular patterns were observed intermittently in the force and blockade current fluctuations that corresponded to the distance between stretched residues. Furthermore, the amplitude of the fluctuations in the current blockade were correlated with the occluded volume associated with the amino acid residues in the pore. Finally, a comparison of the patterns in the current fluctuations associated with the two practically identical histones supported the conclusion that a sub-nanopore was sensitive enough to discriminate amino acid substitutions in the sequence of a single protein molecule by measuring volumes of 0.1 nm3 per read.
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Affiliation(s)
- Zhuxin Dong
- Department of Electrical Engineering and ‡Departments of Electrical Engineering and Biological Science, University of Notre Dame , Notre Dame, Indiana 46556, United States
| | - Eamonn Kennedy
- Department of Electrical Engineering and ‡Departments of Electrical Engineering and Biological Science, University of Notre Dame , Notre Dame, Indiana 46556, United States
| | - Mohammad Hokmabadi
- Department of Electrical Engineering and ‡Departments of Electrical Engineering and Biological Science, University of Notre Dame , Notre Dame, Indiana 46556, United States
| | - Gregory Timp
- Department of Electrical Engineering and ‡Departments of Electrical Engineering and Biological Science, University of Notre Dame , Notre Dame, Indiana 46556, United States
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18
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Hassouneh W, Zhulina EB, Chilkoti A, Rubinstein M. Elastin-like Polypeptide Diblock Copolymers Self-Assemble into Weak Micelles. Macromolecules 2015; 48:4183-4195. [PMID: 27065492 DOI: 10.1021/acs.macromol.5b00431] [Citation(s) in RCA: 78] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The self-assembly of synthetic diblock copolymers has been extensively studied experimentally and theoretically. In contrast, self-assembly of polypeptide diblock copolymers has so far been mostly studied experimentally. We discovered that the theory developed for synthetic diblock copolymer does not fully explain the self-assembly of elastin-like polypeptide diblock copolymers, leading us to generalize the theory to make it applicable for these polypeptides. We demonstrated that elastin-like polypeptide diblocks self-assemble into weak micelles with dense cores and almost unstretched coronas, a state not previously observed for synthetic diblock copolymers. Weak micelles form if the surface tension at the core-corona interface is low compared to that expected of a micelle with a dense core. The predictions of the theory of weak micelles for the critical micelle temperature, hydrodynamic radius, and aggregation number of elastin-like polypeptide diblocks are in reasonable agreement with the experimentally measured values. The unique and unprecedented control of amphiphilicity in these recombinant peptide polymers reveals a new micellar state that has not been previously observed in synthetic diblock copolymer systems.
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Affiliation(s)
- Wafa Hassouneh
- Department of Biomedical Engineering, Duke University, Durham, North Carolina 27708, United States
| | - Ekaterina B Zhulina
- Institute of Macromolecular Compounds, Russian Academy of Sciences, St. Petersburg, Russia; ITMO-University, St. Petersburg, Russia
| | - Ashutosh Chilkoti
- Department of Biomedical Engineering, Duke University, Durham, North Carolina 27708, United States
| | - Michael Rubinstein
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599, United States
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19
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Walker CR, Pushpavanam K, Nair DG, Potta T, Sutiyoso C, Kodibagkar VD, Sapareto S, Chang J, Rege K. Generation of polypeptide-templated gold nanoparticles using ionizing radiation. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:10166-10173. [PMID: 23786455 DOI: 10.1021/la400567d] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Ionizing radiation, including γ rays and X-rays, are high-energy electromagnetic radiation with diverse applications in nuclear energy, astrophysics, and medicine. In this work, we describe the use of ionizing radiation and cysteine-containing elastin-like polypeptides (C(n)ELPs, where n = 2 or 12 cysteines in the polypeptide sequence) for the generation of gold nanoparticles. In the presence of C(n)ELPs, ionizing radiation doses higher than 175 Gy resulted in the formation of maroon-colored gold nanoparticle dispersions, with maximal absorbance at 520 nm, from colorless metal salts. Visible color changes were not observed in any of the control systems, indicating that ionizing radiation, gold salt solution, and C(n)ELPs were all required for nanoparticle formation. The hydrodynamic diameters of nanoparticles, determined using dynamic light scattering, were in the range of 80-150 nm, while TEM imaging indicated the formation of gold cores 10-20 nm in diameter. Interestingly, C2ELPs formed 1-2 nm diameter gold nanoparticles in the absence of radiation. Our results describe a facile method of nanoparticle formation in which nanoparticle size can be tailored based on radiation dose and C(n)ELP type. Further improvements in these polypeptide-based systems can lead to colorimetric detection of ionizing radiation in a variety of applications.
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Affiliation(s)
- Candace Rae Walker
- School of Biological and Health Systems Engineering, Arizona State University, Tempe, Arizona 85287, United States
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20
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Weller D, McDaniel JR, Fischer K, Chilkoti A, Schmidt M. Cylindrical Polymer Brushes with Elastin-Like Polypeptide Side Chains. Macromolecules 2013. [DOI: 10.1021/ma400917t] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- Désirée Weller
- Institute of Physical Chemistry, University of Mainz, Jakob-Welder Weg 11, 55099 Mainz,
Germany
- Graduate School Materials Science in Mainz, Staudinger Weg 9, 55128 Mainz, Germany
| | - Jonathan R. McDaniel
- Department of Biomedical
Engineering, Duke University, Durham, North
Carolina 27708-0181,
United States
| | - Karl Fischer
- Institute of Physical Chemistry, University of Mainz, Jakob-Welder Weg 11, 55099 Mainz,
Germany
| | - Ashutosh Chilkoti
- Department of Biomedical
Engineering, Duke University, Durham, North
Carolina 27708-0181,
United States
| | - Manfred Schmidt
- Institute of Physical Chemistry, University of Mainz, Jakob-Welder Weg 11, 55099 Mainz,
Germany
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21
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Müller WEG, Schröder HC, Muth S, Gietzen S, Korzhev M, Grebenjuk VA, Wiens M, Schloßmacher U, Wang X. The silicatein propeptide acts as inhibitor/modulator of self-organization during spicule axial filament formation. FEBS J 2013; 280:1693-708. [DOI: 10.1111/febs.12183] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2012] [Revised: 02/02/2013] [Accepted: 02/06/2013] [Indexed: 11/29/2022]
Affiliation(s)
- Werner E. G. Müller
- ERC Advanced Grant Research Group at the Institute for Physiological Chemistry; University Medical Center of the Johannes Gutenberg University Mainz; Mainz; Germany
| | - Heinz C. Schröder
- ERC Advanced Grant Research Group at the Institute for Physiological Chemistry; University Medical Center of the Johannes Gutenberg University Mainz; Mainz; Germany
| | - Sandra Muth
- Institute for Physical Chemistry; Johannes Gutenberg University Mainz; Mainz; Germany
| | - Sabine Gietzen
- Institute for Physical Chemistry; Johannes Gutenberg University Mainz; Mainz; Germany
| | - Michael Korzhev
- ERC Advanced Grant Research Group at the Institute for Physiological Chemistry; University Medical Center of the Johannes Gutenberg University Mainz; Mainz; Germany
| | - Vlad A. Grebenjuk
- ERC Advanced Grant Research Group at the Institute for Physiological Chemistry; University Medical Center of the Johannes Gutenberg University Mainz; Mainz; Germany
| | - Matthias Wiens
- ERC Advanced Grant Research Group at the Institute for Physiological Chemistry; University Medical Center of the Johannes Gutenberg University Mainz; Mainz; Germany
| | - Ute Schloßmacher
- ERC Advanced Grant Research Group at the Institute for Physiological Chemistry; University Medical Center of the Johannes Gutenberg University Mainz; Mainz; Germany
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22
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Xu D, Asai D, Chilkoti A, Craig SL. Rheological properties of cysteine-containing elastin-like polypeptide solutions and hydrogels. Biomacromolecules 2012; 13:2315-21. [PMID: 22789001 PMCID: PMC3418688 DOI: 10.1021/bm300760s] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The rheological properties of cysteine-containing elastin-like polypeptide (Cys-ELP) solutions and Cys-ELP hydrogels are reported. The Cys-ELP solutions exhibit a surprisingly high apparent viscosity at low shear rate. The high viscosity is attributed to the formation of an interfacial cross-linked "skin" at the sample surface, rather than the bulk of the Cys-ELP solution. At higher shear rate, the interfacial cross-linked film breaks, and its influence on the viscosity of the Cys-ELP solution can be ignored. Cys-ELP hydrogels are formed by mixing Cys-ELP and hydrogen peroxide (H(2)O(2)). At fixed concentration of Cys-ELP, the gelation time can be tuned by the concentration of H(2)O(2). Cys-ELP hydrogels have the typical characteristics of covalent cross-linked networks, as the storage moduli are larger than the loss moduli and are independent of frequency in dynamic oscillatory frequency sweep experiments. The plateau moduli obtained from linear frequency sweep experiments are much lower than those estimated from the number of thiol groups along the Cys-ELP chain, indicating that only a small fraction of thiols form elastically active cross-links. From the small value of the fraction of elastically active cross-links, the Cys-ELP hydrogel is concluded to be an inhomogenous network. Under steady shear, a 2.5 wt % Cys-ELP hydrogel shear thickens at shear rates lower than that necessary for fracture.
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Affiliation(s)
- Donghua Xu
- Department of Chemistry and Center for Biologically Inspired Materials and Material Systems, Duke University, Durham, North Carolina 27708-0346, USA
- State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Science, Changchun 130022, P. R. China
| | - Daisuke Asai
- Department of Chemistry and Center for Biologically Inspired Materials and Material Systems, Duke University, Durham, North Carolina 27708-0346, USA
- Department of Biomedical Engineering, Duke University, Durham, North Carolina 27708-0281, USA
- Department of Microbiology, St. Marianna University School of Medicine, Kawasaki 216-8511, Japan
| | - Ashutosh Chilkoti
- Department of Chemistry and Center for Biologically Inspired Materials and Material Systems, Duke University, Durham, North Carolina 27708-0346, USA
- Department of Biomedical Engineering, Duke University, Durham, North Carolina 27708-0281, USA
| | - Stephen L. Craig
- Department of Chemistry and Center for Biologically Inspired Materials and Material Systems, Duke University, Durham, North Carolina 27708-0346, USA
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