Self-Assembly of Polypeptide/π-Conjugated Polymer/Polypeptide Triblock Copolymers in Rod−Rod−Rod and Coil−Rod−Coil Conformations
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Abstract:
Self-assembly in the bulk of a series of hybrid triblock copolymers formed by a poly(9,9-dihexylfluorene-2,7-diyl) (PHF) middle block and two poly(γ-benzyl-l-glutamate) (PBLG) end blocks has been studied. Since the α-helical secondary structure of the PBLG block may be either maintained or suppressed depending on the solvent casting history, the PBLG−PHF−PBLG copolymers exhibit two different conformations: a rod−rod−rod or coil−rod−coil configuration, respectively. In order to provide insight into the influence of conformation on self-aggregation of these systems, three copolymers with different block ratio were investigated in both conformations using small- and wide-angle scattering techniques and transmission electron microscopy. Time-resolved photoluminescence measurements were performed on the same samples to explore the effect of morphology on photophysical properties. The observed photoluminescence spectra and dominant excited lifetimes of the poly(9,9-dihexylfluorene-2,7-diyl) block were found to differ markedly in rod−rod−rod and coil−rod−coil configurations and were correlated to the morphology of the self-assembled triblock copolymers.Keywords:
Polypeptide chain
Coiled coil
1,4‐Diethynylbenzene was used as conjugated all‐carbon and rigid spacer between the 2‐, 3‐ and 4‐positions of two 1‐methylquinolinium rings. Thus, for a systematic study, a series of dicationic salts with 2,2‐, 3,3‐, 4,4‐, 3,2‐, and 3,4‐interconnections of the two positive charges was prepared, in which all even‐numbered substitution patterns are conjugated, and all odd‐numbered substitution patterns are cross‐conjugated. As a consequence, conjugated/conjugated, cross‐conjugated/cross‐conjugated, and conjugated/cross‐conjugated dications have been prepared. The different combinations result in considerably different charge distributions of the positive charges within the π‐electron systems according to the rules of resonance which translate into different DFT‐calculated frontier orbital profiles and spectroscopic properties such as 13 C NMR chemical shifts, IR and Raman absorptions, and the measured as well as calculated UV/Vis spectra.
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Elongation
Molecular wire
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Abstract The 13 C NMR spectra of several conjugated polyyne‐aldehydes and ketones are compared with those of the corresponding alcohols. All data show considerable effects similar to those observed in conjugated polyenes.
Carbon fibers
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The first soluble conjugated poly(2,6-anthrylene) with 9,10-diphenyl-anthracene as the repeating unit is reported; photophysical studies reveal that this polymer represents a novel well-conjugated system.
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Abstract Treatment of conjugated enones having both α′- and γ -hydrogens with KN(SiMe3)2 (KHMSA) in a mixed solvent of DMF with THF at −78 °C afforded preferentially linear-conjugated dienolate anions, which were trapped by methyl chloroformate to give the corresponding dienyl methyl carbonates.
Chloroformate
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Tetramer
Coiled coil
Polypeptide chain
Structural motif
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Rules for designing 4-helix bundles are defined, tested, and used to generate de novo peptide assemblies and a single-chain protein.
Coiled coil
Helix (gastropod)
Single chain
Chain (unit)
Helix bundle
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Abstract Reaction of the title heterocycle (I) with 1,3‐butadienes such as (II) or (V) affords conjugated and/or non‐conjugated cyclopentenones such as (III), (IV), (VII) or (VIII) in a novel one‐pot procedure.
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A novel approach for the modeling of coiled coils through molecular dynamics is described and applied to the dimerization region of the yeast transcriptional activator GCN4. Initially, a model is created consisting of Cα atoms only, representing an idealized coiled coil with infinite pitch. Human bias in the placing of the other atoms is reduced by an automatic building procedure using simulated annealing with simple geometric restraints. The resulting all-atom model is then allowed to relax during a short molecular dynamics run using an empirical energy function and weak restraints which reflect the coiled coil assumption. These models are then further refined using unrestrained molecular dynamics in water. In this report we test the model-building procedure on the known dimerization region of catabolyte gene activator protein (CAP), part of which forms a coiled coil, and we predict the structure of the coiled coil dimerization region (the ‘leucine zipper’ domain) of GCN4. Several models are built, starting from different arrangements of the C° atoms in the initial structures. The final structures show similar crossing angles of the coiled coil, although this was not used as a restraint in the calculation. The leucines adopt a ladder-like conformation around the 2-fold axis of the coiled coil. A number of electrostatic interactions could be identified which may contribute to the stability of the helical structure of the monomers and of the dimer.
Coiled coil
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Kinesin is the founding member of a family of motor proteins. It translocates along microtubules in the direction of the plus or fast-growing end. Conventional kinesin consists of two identical heavy chains carrying the motor activity, and two light chains. Based on its amino acid sequence, the heavy chain can be divided into three separate domains: (1) an N-terminal head, or motor domain, (2) an elongated a-helical stretch forming a coiled coil with a second kinesin heavy-chain polypeptide, (3) a C-terminal globular domain responsible for cargo binding and regulation of the motor's activity (for reviews, see refs. 1–4).
Kinesin
Coiled coil
Polypeptide chain
Molecular motor
Chain (unit)
C-terminus
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