Large protein-based micellar aggregates (see Figure) are reversibly formed upon self-assembly of the amphiphilic diblock copolymer—based on elastin-mimetic peptide sequences—biosynthesized here. The biocompatibility, high recombinant protein yields, physiological stability, and tunable responsive properties of these polymers make them attractive candidates for controlled delivery and release applications.
Falsch gefaltet: Die epimeren N-Acetyl-(2R,3R)- und N-Acetyl-(2R,3S)-3-fluorprolinmethylester (1 und 2; siehe Schema) weisen entgegengesetzte Ringfaltungen auf, die die Vorzugskonformationen der 4-Fluorprolinderivate 3 und 4 umkehren. Der Einbau dieser Fluorproline in Proteine ist eine Möglichkeit, die lokale Konformation durch stereoelektronische und sterische Effekte zu steuern.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTRing-opening metathesis polymerization of substituted bicyclo[2.2.2]octadienes: a new precursor route to poly(1,4-phenylenevinylene)Vincent P. Conticello, Douglas L. Gin, and Robert H. GrubbsCite this: J. Am. Chem. Soc. 1992, 114, 24, 9708–9710Publication Date (Print):November 1, 1992Publication History Published online1 May 2002Published inissue 1 November 1992https://pubs.acs.org/doi/10.1021/ja00050a088https://doi.org/10.1021/ja00050a088research-articleACS PublicationsRequest reuse permissionsArticle Views843Altmetric-Citations135LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-AlertscloseSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts
Tandem repeat proteins exhibit native designability and represent potentially useful scaffolds for the construction of synthetic biomimetic assemblies. We have designed 2 synthetic peptides, HEAT_R1 and LRV_M3Δ1, based on the consensus sequences of single repeats of thermophilic HEAT (PBS_HEAT) and Leucine-Rich Variant (LRV) structural motifs, respectively. Self-assembly of the peptides afforded high-aspect ratio helical nanotubes. Cryo-electron microscopy with direct electron detection was employed to analyze the structures of the solvated filaments. The 3D reconstructions from the cryo-EM maps led to atomic models for the HEAT_R1 and LRV_M3Δ1 filaments at resolutions of 6.0 and 4.4 Å, respectively. Surprisingly, despite sequence similarity at the lateral packing interface, HEAT_R1 and LRV_M3Δ1 filaments adopt the opposite helical hand and differ significantly in helical geometry, while retaining a local conformation similar to previously characterized repeat proteins of the same class. The differences in the 2 filaments could be rationalized on the basis of differences in cohesive interactions at the lateral and axial interfaces. These structural data reinforce previous observations regarding the structural plasticity of helical protein assemblies and the need for high-resolution structural analysis. Despite these observations, the native designability of tandem repeat proteins offers the opportunity to engineer novel helical nanotubes. Moreover, the resultant nanotubes have independently addressable and chemically distinguishable interior and exterior surfaces that would facilitate applications in selective recognition, transport, and release.
Physically cross-linked protein-based materials possess a number of advantages over their chemically cross-linked counterparts, including ease of processing and the ability to avoid the addition or removal of chemical reagents or unreacted intermediates. The investigations reported herein sought to examine the nature of physical cross-links within two-phase elastin−mimetic protein triblock copolymer networks through an analysis of macroscopic viscoelastic properties. Given the capacity of solution processing conditions, including solvent type and temperature to modulate the microstructure of two-phase protein polymer networks, viscoelastic properties were examined under conditions in which interphase block mixing had been either accentuated or diminished during network formation. Protein networks exhibited strikingly different properties in terms of elastic modulus, hysteresis, residual deformability, and viscosity in response to interdomain mixing. Thus, two-phase protein polymer networks exhibit tunable responses that extend the range of application of these materials to a variety of tissue engineering applications.
Solid-state cross-linking of elastin−mimetic fibers was investigated. Through available lysine residues, an elastin−mimetic protein polymer, poly((Val-Pro-Gly-Val-Gly)4(Val-Pro-Gly-Lys-Gly))39, was modified to incorporate an acrylate moiety. The degree of acrylate functionalization could be varied by changing the reactant ratio of anhydride to elastin. Acrylate modified elastomeric (AME) proteins were associated with lower inverse transition temperatures than the unmodified recombinant protein. The inverse transition temperature in turn dictated the temperature for fiber formation. Fibers and fabric samples of AME were prepared by electrospinning at appropriate temperatures and cross-linked by visible-light-mediated photoirradiation. Fibers in the diameter range of 300 nm−1.5 μm were produced. Fabrics were found to have an average pore size of 78 μm. The occurrence of cross-linking was confirmed by 13C solid-state NMR with a commensurate increase in modulus.
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