Conformational Locks Research Articles

A conformational locking strategy in linked-acceptor type polymers for organic solar cells

The concept of introducing intramolecular noncovalent conformational locks into the polymer main chain was implemented to improve the coplanarity of the linked-acceptor polymers. As a result, the novel polymer shows the best power conversion efficiency of 8.18%.

Highly planar cross-conjugated alternating polymers with multiple conformational locks: synthesis, characterization and their field-effect properties

Two highly planar cross-conjugated polymers with multiple conformational locks were designed and synthesized, and their charge transport properties were investigated.

Synthetic Tailoring of Solid-State Order in Diketopyrrolopyrrole-Based Copolymers via Intramolecular Noncovalent Interactions

Understanding the microstructures of semiconducting polymers is critical for improving the charge transport properties of polymer field-effect transistors (PFETs). A series of diketopyrrolopyrrole-based copolymers designed by implementing the concept of intramolecular noncovalent conformational locks through the functionalization of polymer backbones with fluorine atoms or methoxy groups were synthesized and compared with their unfunctionalized analogue. In contrast to the bimodal texture of the unfunctionalized polymer, the thin films of the polymer with fluorine atoms exhibit predominantly edge-on texture with much improved crystalline ordering. The thin films of the polymer modified with methoxy groups have a principally face-on texture. These dramatic differences in thin-film texture can be correlated with the polymers’ solubilities. Furthermore, the improved crystalline ordering of these semiconductor polymers enables the fabrication of high-performance PFETs: the hole mobility of the methoxy-modified polymer is reduced by half with respect to that of the unmodified polymer, whereas the hole mobility values of the fluorine-modified polymer are up to ∼6 times higher, approximately 1.32 cm2 V–1 s–1, and exhibit pronounced thermal stability. These results provide new guidelines for the molecular design of semiconducting polymers with noncovalent conformational locks.

Convenient synthesis of 1,3-dithiolane-2-thiones: cyclic trithiocarbonates as conformational locks

Convenient synthesis of 1,3-dithiolane-2-thiones: cyclic trithiocarbonates as conformational locks

Benzotriazole-Containing Planar Conjugated Polymers with Noncovalent Conformational Locks for Thermally Stable and Efficient Polymer Field-Effect Transistors

We report a series of benzotriazole-based semicrystalline π-conjugated polymers with noncovalent conformational locks for applications in polymer field-effect transistors. The benzotriazole moiety is a versatile electron-deficient building block that offers two chemically functionalizable sites, 2(N) and 5, 6(C) positions, allowing easy modulation of the solution processability and electronic structures of the resulting polymers. Fluorine or alkoxy substituents were introduced to the benzotriazole unit to enhance the molecular ordering through intra- and intermolecular F···S, F···H–C, C–F···πF, or S···O attractive interactions. The fluorinated polymer (PTBTz-F) showed remarkably enhanced hole mobility (μh = 1.9 cm2/(V·s), on/off ratio = 8 × 107) upon thermal annealing at 305 °C, compared to the unsubstituted one (PTBTz) (μh = 7.0 × 10–3 cm2/(V·s), on/off ratio = 3 × 106). Alkoxy unit substitution (PTBTz-OR) also improved the carrier mobility up to 0.019 cm2/(V·s) with an on/off ratio of 4 × 105. Fluorine ...

Trapping the dynamic acyl carrier protein in fatty acid biosynthesis

Acyl carrier protein (ACP) transports the growing fatty acid chain between enzymatic domains of fatty acid synthase (FAS) during biosynthesis. Because FAS enzymes operate on ACP-bound acyl groups, ACP must stabilize and transport the growing lipid chain. ACPs have a central role in transporting starting materials and intermediates throughout the fatty acid biosynthetic pathway. The transient nature of ACP-enzyme interactions impose major obstacles to obtaining high-resolution structural information about fatty acid biosynthesis, and a new strategy is required to study protein-protein interactions effectively. Here we describe the application of a mechanism-based probe that allows active site-selective covalent crosslinking of AcpP to FabA, the Escherichia coli ACP and fatty acid 3-hydroxyacyl-ACP dehydratase, respectively. We report the 1.9 Å crystal structure of the crosslinked AcpP-FabA complex as a homodimer in which AcpP exhibits two different conformations, representing probable snapshots of ACP in action: the 4'-phosphopantetheine group of AcpP first binds an arginine-rich groove of FabA, then an AcpP helical conformational change locks AcpP and FabA in place. Residues at the interface of AcpP and FabA are identified and validated by solution nuclear magnetic resonance techniques, including chemical shift perturbations and residual dipolar coupling measurements. These not only support our interpretation of the crystal structures but also provide an animated view of ACP in action during fatty acid dehydration. These techniques, in combination with molecular dynamics simulations, show for the first time that FabA extrudes the sequestered acyl chain from the ACP binding pocket before dehydration by repositioning helix III. Extensive sequence conservation among carrier proteins suggests that the mechanistic insights gleaned from our studies may be broadly applicable to fatty acid, polyketide and non-ribosomal biosynthesis. Here the foundation is laid for defining the dynamic action of carrier-protein activity in primary and secondary metabolism, providing insight into pathways that can have major roles in the treatment of cancer, obesity and infectious disease.

Correction to “Combining Electron-Neutral Building Blocks with Intramolecular ‘Conformational Locks’ Affords Stable, High-Mobility P- and N-Channel Polymer Semiconductors”

ADVERTISEMENT RETURN TO ISSUEPREVAddition/CorrectionORIGINAL ARTICLEThis notice is a correctionCorrection to “Combining Electron-Neutral Building Blocks with Intramolecular ‘Conformational Locks’ Affords Stable, High-Mobility P- and N-Channel Polymer Semiconductors”Hui Huang, Zhihua Chen, Rocio Ponce Ortiz, Christopher Newman, Hakan Usta, Sylvia Lou, Jangdae Youn, Yong-Young Noh, Kang-Jun Baeg, Lin X. Chen, Antonio Facchetti*, and Tobin J. Marks*Cite this: J. Am. Chem. Soc. 2013, 135, 10, 4160Publication Date (Web):March 4, 2013Publication History Published online4 March 2013Published inissue 13 March 2013https://doi.org/10.1021/ja400834jCopyright © 2013 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views1010Altmetric-Citations1LEARN 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 InReddit PDF (120 KB) Get e-Alerts Get e-Alerts

Thermal inactivation and conformational lock studies on glucose oxidase

In this study, the dissociative thermal inactivation and conformational lock theories are applied for the homodimeric enzyme glucose oxidase (GOD) in order to analyze its structure. For this purpose, the rate of activity reduction of glucose oxidase is studied at various temperatures using β-d-glucose as the substrate by incubation of enzyme at various temperatures in the wide range between 40 and 70 °C using UV–Vis spectrophotometry. It was observed that in the two ranges of temperatures, the enzyme has two different forms. In relatively low temperatures, the enzyme is in its dimeric state and has normal activity. In high temperatures, the activity almost disappears and it aggregates. The above achievements are confirmed by dynamic light scattering. The experimental parameter “n” as the obvious number of conformational locks at the dimer interface of glucose oxidase is obtained by kinetic data, and the value is near to two. To confirm the above results, the X-ray crystallography structure of the enzyme, GOD (pdb, 1gal), was also studied. The secondary and tertiary structures of the enzyme to track the thermal inactivation were studied by circular dichroism and fluorescence spectroscopy, respectively. We proposed a mechanism model for thermal inactivation of GOD based on the absence of the monomeric form of the enzyme by circular dichroism and fluorescence spectroscopy.

Thermal Inactivation and Conformational Lock of Bovine Carbonic Anhydrase

The kinetics of thermal inactivation of bovine carbonic anhydrase (BCA) was studied in a 50 mM Tris-HCl buffer, pH 7.8 using p-nitrophenyl acetate as substrate in absorbance of 400 nm by UV-VIS spectrophotometry. The number of conformational locks and inter-subunit amino acid residues of BCA were obtained by thermal inactivation analysis. The cleavage bonds between dimers of BCA during thermal dissociation and type of interactions between specific amino acid residues were also detected. The thermal inactivation curves were plotted in temperatures ranging between 40-70°C. It was shown several phases for inactivation of BCA at 65°C. Analyses of the curves were done by the conformational lock theory. The subunits are dissociated and several intermediates appear during inactivation through increasing the temperature in comparison with native state. Dynamic light scattering measurements was done to study the changes in hydrodynamic radius during thermal inactivation. Three distinct zones were shown in DLS data. Biochemical computation using ligplot is performed to find the inter-subunit amino acid residues for BCA.

Combining Electron-Neutral Building Blocks with Intramolecular “Conformational Locks” Affords Stable, High-Mobility P- and N-Channel Polymer Semiconductors

Understanding the relationship between molecular/macromolecular architecture and organic thin film transistor (TFT) performance is essential for realizing next-generation high-performance organic electronics. In this regard, planar π-conjugated, electron-neutral (i.e., neither highly electron-rich nor highly electron-deficient) building blocks represent a major goal for polymeric semiconductors, however their realization presents synthetic challenges. Here we report that an easily accessible (minimal synthetic steps), electron-neutral thienyl-vinylene (TVT)-based building block having weak intramolecular S···O "conformational locks" affords a new class of stable, structurally planar, solution-processable, high-mobility, molecular, and macromolecular semiconductors. The attraction of merging the weak TVT electron richness with supramolecular planarization is evident in the DFT-computed electronic structures, favorable MO energetics, X-ray diffraction-derived molecular structures, experimental lattice coehesion metrics, and excellent TFT performance. TVT-based polymer TFTs exhibit stable carrier mobilities in air as high as 0.5 and 0.05 cm(2)/V·s (n- and p-type, respectively). All-TVT polymer-based complementary inverter circuitry exhibiting high voltage gains (~50) and ring oscillator circuitry with high f(osc)(~1.25 kHz) is readily fabricated from these materials by simple inkjet printing.

Aromatic residues link binding and function of intrinsically disordered proteins

We have searched for intermolecular aromatic pairs in 77 protein-protein complexes of intrinsically disordered proteins (IDPs) to understand the role of π-π interactions in protein-protein interactions involving IDPs. We found that 40% of the complexes possess at least one intermolecular pair of aromatic residues. Analysis of composition, characteristics, location and the contribution to the free energy of binding showed that π-π interactions substantially contribute to binding by working as anchor residues, conformational locks, and ready-made recognition motifs required for specific binding. By using available experimental data we show that π-π interactions play a variety of roles that link binding of IDPs and their function in the cell. The results presented in this study pave the way to understand in atomic detail the inner workings of IDPs interaction networks.

Antibody Locks Up West Nile Virus Cell-Entry Mechanism

Researchers identified a monoclonal antibody (MAB) that neutralizes West Nile virus (WNV) by binding and crosslinking viral surface proteins that are needed to infect host cells. “The antibody crosslinking causes the virus to become rigid, and this rigidity prevents conformational changes and locks up the infectious mechanism,” says Michael Rossmann, study leader at Purdue University in West Lafayette, Ind. Learning how antibodies neutralize this virus could prove important for developing vaccines against infections caused by this mosquito-borne virus or those caused by other flaviviruses.

Thermal Dissociation and Conformational Lock of Superoxide Dismutase

The kinetics of thermal dissociation of superoxide dismutase (SOD) was studied in 0.05 M Tris-HCl buffer at pH 7.4 containing 10(-4) M EDTA. The number of conformational locks and contact areas and amino acid residues of dimers of SOD were obtained by kinetic analysis and biochemical calculation. The cleavage bonds between dimers of SOD during thermal dissociation and type of interactions between specific amino acid residues were also simulated. Two identical contact areas between two subunits were identified. Cleavage of these contact areas resulted in dissociation of the subunits, with destruction of the active centers, and thus, lost of activity. It is suggested that the contact areas interact with active centers by conformational changes involving secondary structural elements.

Podand ionophores with dialkoxy conformational locks

Ionophores 2–4 which incorporate a novel + gauchel-gauche dialkoxy conformational locking mechanism were synthesized from D-mannitol. These new podands bound various chiral ammonium ions enantioselectively, but comparisons with related alkylated podands indicated that dialkyl and dialkoxy conformational locks are not completely interchangable.

A theoretical conformational study of substituted O-anisamides as models of a class of dopamine antagonists.

The quantum mechanical PCILO method has been used to investigate the conformational behaviour of N-(2-aminoethyl)- and N-(2-dimethylaminoethyl)-o-anisamide, two model molecules of substituted benzamides. The molecules are shown to have only limited conformational freedom due to the presence of two intramolecular hydrogen bonds acting as conformational locks. The molecules in their preferred conformation are characterized by a distance between the centre of the aromatic ring and the nitrogen atom of almost 6 A, i.e. almost 1 A longer than in the fully extended dopamine conformers. Some implications at the receptor level of this topographical dissimilarity are discussed.