1
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López-Gandul L, Morón-Blanco A, García F, Sánchez LL. Supramolecular Block Copolymers from Tricarboxamides. Biasing Co-assembly by the Incorporation of Pyridine Rings. Angew Chem Int Ed Engl 2023; 62:e202308749. [PMID: 37483088 DOI: 10.1002/anie.202308749] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2023] [Revised: 07/17/2023] [Accepted: 07/21/2023] [Indexed: 07/25/2023]
Abstract
The synthesis of a series of triangular-shaped tricarboxamides endowed with three picoline or nicotine units (compounds 2 and 3, respectively) or just one nicotine unit (compound 4) is reported, and their self-assembling features investigated. The pyridine rings make compounds 2-4 electronically complementary with our previously reported oligo(phenylene ethynylene)tricarboxamides (OPE-TA) 1 to form supramolecular copolymers. C3 -symmetric tricarboxamide 2 forms highly stable intramolecular five-membered pseudocycles that impede its supramolecular polymerization into poly-2 and the co-assembly with 1 to yield copolymer poly-1-co-2. On the other hand, C3 -symmetric tricarboxamide 3 readily forms poly-3 with great stability but unable to form helical supramolecular polymers despite the presence of the peripheral chiral side chains. The copolymer poly-1-co-3 can only be obtained by a previous complete disassembly of the constitutive homopolymers in CHCl3 . Helical poly-1-co-3 arises in a process involving the transfer of the helicity from racemic poly-1 to poly-3, and the amplification of asymmetry from chiral poly-3 to poly-1. Importantly, C2v -symmetric 4, endowed with only one nicotinamide moiety and three chiral side chains, self-assembles into a P-type helical supramolecular polymer (poly-4) in a thermodynamically controlled cooperative process. The combination of poly-1 and poly-4 generates chiral supramolecular copolymer poly-1-co-4, whose blocky microstructure has been investigated by applying the previously reported supramolecular copolymerization model.
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Affiliation(s)
- Lucía López-Gandul
- Departamento de Química Orgánica, Facultad de Ciencias Químicas, Universidad Complutense de Madrid Ciudad Universitaria, s/n, 28040-, Madrid, Spain
| | - Adrián Morón-Blanco
- Departamento de Química Orgánica, Facultad de Ciencias Químicas, Universidad Complutense de Madrid Ciudad Universitaria, s/n, 28040-, Madrid, Spain
| | - Fátima García
- Departamento de Química Orgánica, Facultad de Ciencias Químicas, Universidad Complutense de Madrid Ciudad Universitaria, s/n, 28040-, Madrid, Spain
| | - L Luis Sánchez
- Departamento de Química Orgánica, Facultad de Ciencias Químicas, Universidad Complutense de Madrid Ciudad Universitaria, s/n, 28040-, Madrid, Spain
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2
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Abstract
We consider a conventional α -Ω -dynamo model with meridional circulation that exhibits typical features of the solar dynamo, including a Hale-cycle period of around 20 years and a reasonable shape of the butterfly diagram. With regard to recent ideas of a tidal synchronization of the solar cycle, we complement this model by an additional time-periodic α -term that is localized in the tachocline region. It is shown that amplitudes of some decimeters per second are sufficient for this α -term to become capable of entraining the underlying dynamo. We argue that such amplitudes of α may indeed be realistic, since velocities in the range of m s-1 are reachable, e.g., for tidally excited magneto-Rossby waves. Supplementary Information The online version contains supplementary material available at 10.1007/s11207-023-02173-y.
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Affiliation(s)
- M. Klevs
- Helmholtz-Zentrum Dresden – Rossendorf, Bautzner Landstr. 400, D-01328 Dresden, Germany
- Institute for Numerical Modelling, University of Latvia, 3 Jelgavas street, Riga, LV-1004 Latvia
| | - F. Stefani
- Helmholtz-Zentrum Dresden – Rossendorf, Bautzner Landstr. 400, D-01328 Dresden, Germany
| | - L. Jouve
- Univ. Toulouse, IRAP, CNRS, UMR 5277, CNES, UPS, F-31400 Toulouse, France
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3
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Oba M, Nakajima S, Misao K, Yokoo H, Tanaka M. Effect of helicity and hydrophobicity on cell-penetrating ability of arginine-rich peptides. Bioorg Med Chem 2023; 91:117409. [PMID: 37441862 DOI: 10.1016/j.bmc.2023.117409] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2023] [Revised: 07/03/2023] [Accepted: 07/04/2023] [Indexed: 07/15/2023]
Abstract
Arginine (Arg)-rich peptides are one of the typical cell-penetrating peptides (CPPs), which can deliver membrane-impermeable compounds into intracellular compartments. Guanidino groups in Arg-rich peptides are critical for their high cell-penetrating ability, although it remains unclear whether peptide secondary structures contribute to this ability. In the current study, we designed four Arg-rich peptides containing α,α-disubstituted α-amino acids (dAAs), which prefer to adopt a helical structure. The four dAA-containing peptides adopted slightly different peptide secondary structures, from a random structure to a helical structure, with different hydrophobicities. In these peptides, dipropylglycine-containing peptide exhibited the highest helicity and hydrophobicity, and showed the best cell-penetrating ability. These findings suggested that the helicity and hydrophobicity of Arg-rich peptides contributes to their high cell-penetrating ability.
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Affiliation(s)
- Makoto Oba
- Medical Chemistry, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, 1-5 Shimogamohangi-cho, Sakyo-ku, Kyoto 606-0823, Japan.
| | - Shun Nakajima
- Graduate School of Biomedical Sciences, Nagasaki University, 1-14 Bunkyo-machi, Nagasaki 852-8521, Japan
| | - Kurumi Misao
- Graduate School of Biomedical Sciences, Nagasaki University, 1-14 Bunkyo-machi, Nagasaki 852-8521, Japan
| | - Hidetomo Yokoo
- Medical Chemistry, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, 1-5 Shimogamohangi-cho, Sakyo-ku, Kyoto 606-0823, Japan
| | - Masakazu Tanaka
- Graduate School of Biomedical Sciences, Nagasaki University, 1-14 Bunkyo-machi, Nagasaki 852-8521, Japan
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4
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Espinosa YR, Barrera Valderrama DI, Carlevaro CM, Llanos EJ. Molecular basis of the anchoring and stabilization of human islet amyloid polypeptide in lipid hydroperoxidized bilayers. Biochim Biophys Acta Gen Subj 2022; 1866:130200. [PMID: 35820640 DOI: 10.1016/j.bbagen.2022.130200] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Revised: 06/25/2022] [Accepted: 07/02/2022] [Indexed: 01/18/2023]
Abstract
The molecular structure of membrane lipids is formed by mono- or polyunsaturations on their aliphatic tails that make them susceptible to oxidation, facilitating the incorporation of hydroperoxide (R-OOH) functional groups. Such groups promote changes in both composition and complexity of the membrane significantly modifying its physicochemical properties. Human Langerhans islets amyloid polypeptide (hIAPP) is the main component of amyloid deposits found in the pancreas of patients with type-2 diabetes (T2D). hIAPP in the presence of membranes with oxidized lipid species accelerates the formation of amyloid fibrils or the formation of intermediate oligomeric structures. However, the molecular bases at the initial stage of the anchoring and stabilization of the hIAPP in a hydroperoxidized membrane are not yet well understood. To shed some light on this matter, in this contribution, three bilayer models were modeled: neutral (POPC), anionic (POPS), and oxidized (POPCOOH), and full atom Molecular Dynamics (MD) simulations were performed. Our results show that the POPCOOH bilayer increases the helicity in hIAPP when compared to POPC or POPS bilayer. The modification in the secondary structure covers the residues of the so-called amyloidogenic core of the hIAPP. Overall, the hydroperoxidation of the neutral lipids modifies both the anchoring and the stabilization of the peptide hIAPP by reducing the random conformations of the peptide and increasing of hydrogen bond population with the hydroperoxidized lipids.
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Shiina Y, Inai K, Miyazaki S, Nagao M. Aortic Vorticity, Helicity, and Aortopathy in Adult Patients with Tetralogy of Fallot: Pilot Study Using Four-Dimensional Flow Magnetic Resonance Images. Pediatr Cardiol 2021; 42:169-77. [PMID: 32978672 DOI: 10.1007/s00246-020-02466-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/28/2020] [Accepted: 09/16/2020] [Indexed: 10/23/2022]
Abstract
To employ quantitative analysis in the vorticity and helicity of the aortic root and the ascending aorta (AAo) in adults with tetralogy of Fallot (TOF), and to evaluate aortopathy and the relevant factors. Prospectively, 51 consecutive adults with TOF underwent 4 dimensional flow magnetic resonance imaging study for the assessment of vorticity and helicity of the aortic root and AAo, wall shear stress (WSS), viscous energy loss (EL), and the left ventricular outflow tract - aortic root (LVOT-Ao) angle. Patients were divided into the two groups: dilated aortic root and/or AAo (indexed diameter > 25 mm/cm2), Group A (15 patients); non-dilated aortic patients, Group B (36 patients). Ten age-matched controls were also enrolled. Group A showed more acute LVOT-Ao angle, higher incidence of aortic regurgitation, and initial anatomy of pulmonary atresia, compared to Group B (P < 0.0001, 0.02, 0.043). Group A showed greater clockwise vorticity at the level of Valsalva, AAo, and proximal arch, sagittal vorticity, AAo helicity, WSS, and EL than in Group B (P < 0.001, < 0.001, < 0.001, 0.045, 0.049, 0.02, 0.026). More acute LVOT-Ao angle correlated with the diameter of the aortic root and AAo, AAo vorticity, helicity, WSS, and EL (P = 0.004, 0.023, 0.045, 0.004, 0.0004, 0.017). On a univariate logistic analysis, more acute LVOT-Ao angle, AAo vorticity, AAo helicity, and maximum WSS were relevant factors of AAo dilatation (P = 0.02, 0.02, 0.045, 0.03, 0.046). On a multivariate logistic analysis, more acute LVOT-Ao angle was the most important factor of AAo dilatation (odds ratio 0.66, 95% CI 0.46-0.95, P < 0.024). TOF adults presenting dilated AAo have greater vorticity, helicity, and acute LVOT-Ao angle. Flow eccentricity and these flow hemodynamic parameters may be adjunctive predictions of aortopathy in this population.
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Huizi-Rayo U, Gutierrez J, Seco JM, Mujica V, Diez-Perez I, Ugalde JM, Tercjak A, Cepeda J, San Sebastian E. An Ideal Spin Filter: Long-Range, High-Spin Selectivity in Chiral Helicoidal 3-Dimensional Metal Organic Frameworks. Nano Lett 2020; 20:8476-8482. [PMID: 33170013 DOI: 10.1021/acs.nanolett.0c02349] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
An enantiopure, conductive, and paramagnetic crystalline 3-D metal-organic framework (MOF), based on Dy(III) and the l-tartrate chiral ligand, is proved to behave as an almost ideal electron spin filtering material at room temperature, transmitting one spin component only, leading to a spin polarization (SP) power close to 100% in the ±2 V range, which is conserved over a long spatial range, larger than 1 μm in some cases. This impressive spin polarization capacity of this class of nanostructured materials is measured by means of magnetically polarized conductive atomic force microscopy and is attributed to the Chirality-Induced Spin Selectivity (CISS) effect of the material arising from a multidimensional helicity pattern, the inherited chirality of the organic motive, and the enhancing influence of Dy(III) ions on the CISS effect, with large spin-orbit coupling values. Our results represent the first example of a MOF-based and CISS-effect-mediated spin filtering material that shows a nearly perfect SP. These striking results obtained with our robust and easy-to-synthesize chiral MOFs constitute an important step forward in to improve the performance of spin filtering materials for spintronic device fabrication.
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Affiliation(s)
- Uxua Huizi-Rayo
- Departamento de Química Aplicada, Facultad de Química, Universidad del País Vasco (UPV/EHU), 20018 Donostia, Spain
| | - Junkal Gutierrez
- Group "Materials+Technologies" (GMT), Department of Chemical and Environmental Engineering, Faculty of Engineering Gipuzkoa, University of the Basque Country (UPV/EHU), Plaza Europa 1, 20018 Donostia-San Sebastian, Spain
- Department of Chemical and Environmental Engineering, Faculty of Engineering Vitoria-Gasteiz, University of the Basque Country (UPV/EHU), C/Nieves Cano 12, 01006 Vitoria-Gasteiz, Spain
| | - Jose Manuel Seco
- Departamento de Química Aplicada, Facultad de Química, Universidad del País Vasco (UPV/EHU), 20018 Donostia, Spain
| | - Vladimiro Mujica
- School of Molecular Sciences, Arizona State University, Tempe, Arizona 85287, United States
- Ikerbasque, Basque Foundation for Science, 48011 Bilbao, Spain
- Kimika Fakultatea, Euskal Herriko Unibertsitatea and Donostia International Physics Center (DIPC), P. K. 1072, 20080 Donostia, Euskadi, Spain
| | - Ismael Diez-Perez
- Department of Chemistry, Faculty of Natural & Mathematical Sciences, King's College London, Britannia House, 7 Trinity Street, London SE1 1DB, U.K
| | - Jesus M Ugalde
- Kimika Fakultatea, Euskal Herriko Unibertsitatea and Donostia International Physics Center (DIPC), P. K. 1072, 20080 Donostia, Euskadi, Spain
| | - Agnieszka Tercjak
- Group "Materials+Technologies" (GMT), Department of Chemical and Environmental Engineering, Faculty of Engineering Gipuzkoa, University of the Basque Country (UPV/EHU), Plaza Europa 1, 20018 Donostia-San Sebastian, Spain
| | - Javier Cepeda
- Departamento de Química Aplicada, Facultad de Química, Universidad del País Vasco (UPV/EHU), 20018 Donostia, Spain
| | - Eider San Sebastian
- Departamento de Química Aplicada, Facultad de Química, Universidad del País Vasco (UPV/EHU), 20018 Donostia, Spain
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7
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Conti M, Ferrarini A, Finotello A, Salsano G, Auricchio F, Palombo D, Spinella G, Pane B. Patient-specific computational fluid dynamics of femoro-popliteal stent-graft thrombosis. Med Eng Phys 2020; 86:57-64. [PMID: 33261734 DOI: 10.1016/j.medengphy.2020.10.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2020] [Revised: 06/18/2020] [Accepted: 10/14/2020] [Indexed: 01/07/2023]
Abstract
Intra-stent thrombosis is one of the major failure modes of popliteal aneurysm endovascular repair, especially when the diseased arterial segment is long and requires overlapping stent-grafts having different nominal diameters in order to accommodate the native arterial tapering. However, the interplay between stent sizing, post-operative arterial tortuosity, luminal diameter, local hemodynamics, and thrombosis onset is not elucidated, yet. In the present study, a popliteal aneurysm was treated with endovascular deployment of two overlapped stent-grafts, showing intra-stent thrombosis at one-year follow-up examination. Patient-specific computational fluid-dynamics analyses including straight- and bent-leg position were performed. The computational fluid-dynamics analysis showed that the overlapping of the stent-grafts induces a severe discontinuity of lumen, dividing the stented artery in two regions: the proximal part, affected by thrombosis, is characterized by larger diameter, low tortuosity, low flow velocity, low helicity, and low wall shear stress; the distal part presents higher tortuosity and smaller lumen diameter promoting higher flow velocity, higher helicity, and higher wall shear stress. Moreover, leg bending induces an overall increase of arterial tortuosity and reduces flow velocity promoting furtherly the luminal area exposed to low wall shear stress.
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Affiliation(s)
- Michele Conti
- Department of Civil Engineering and Architecture, University of Pavia, Via Ferrata 3, 27100 Pavia, Italy.
| | - Anna Ferrarini
- Department of Civil Engineering and Architecture, University of Pavia, Via Ferrata 3, 27100 Pavia, Italy
| | - Alice Finotello
- Department of Surgical and Integrated Diagnostic Sciences, University of Genoa, Italy
| | - Giancarlo Salsano
- Department of Radiology, IRCCS Ospedale Policlinico San Martino, Genoa, Italy
| | - Ferdinando Auricchio
- Department of Civil Engineering and Architecture, University of Pavia, Via Ferrata 3, 27100 Pavia, Italy
| | - Domenico Palombo
- Vascular and Endovascular Surgery Unit, IRCCS Ospedale Policlinico San Martino, Genoa, Italy
| | - Giovanni Spinella
- Vascular and Endovascular Surgery Unit, IRCCS Ospedale Policlinico San Martino, Genoa, Italy
| | - Bianca Pane
- Vascular and Endovascular Surgery Unit, IRCCS Ospedale Policlinico San Martino, Genoa, Italy
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8
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Jamalidinan F, Hassanabad AF, François CJ, Garcia J. Four-dimensional-flow Magnetic Resonance Imaging of the Aortic Valve and Thoracic Aorta. Radiol Clin North Am 2020; 58:753-63. [PMID: 32471542 DOI: 10.1016/j.rcl.2020.02.008] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Blood flow through the heart and great vessels is sensitive to time and multiple velocity directions. The assessment of its three-dimensional nature has been limited. Recent advances in magnetic resonance imaging (MRI) allow the comprehensive visualization and quantification of in vivo flow dynamics using four-dimensional (4D)-flow MRI. In addition, the technique provides the opportunity to obtain advanced hemodynamic measures. This article introduces 4D-flow MRI as it is currently used for blood flow visualization and quantification of cardiac hemodynamic parameters. It discusses its advantages relative to other flow MRI techniques and describes its potential clinical applications.
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9
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Goto C, Hirano M, Hayashi K, Kikuchi Y, Hara-Kudo Y, Misawa T, Demizu Y. Development of Amphipathic Antimicrobial Peptide Foldamers Based on Magainin 2 Sequence. ChemMedChem 2019; 14:1911-1916. [PMID: 31667994 DOI: 10.1002/cmdc.201900460] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2019] [Revised: 09/27/2019] [Indexed: 11/07/2022]
Abstract
Magainin 2 (Mag 2), which is isolated from the skin of frogs, is a representative antimicrobial peptide (AMP), exerts its antimicrobial activity via microbial membrane disruption. It has been reported that both the amphipathicity and helical structure of Mag 2 play an important role in its antimicrobial activity. In this study, we revealed that the sequence of 17 amino acid residues in Mag 2 (peptide 7) is required to exert sufficient activity. We also designed a set of Mag 2 derivatives, based on enhancement of helicity and/or amphipathicity, by incorporation of α,α-disubstituted amino acid residues into the Mag 2 fragment, and evaluated their preferred secondary structures and their antimicrobial activities against both Gram-positive and Gram-negative bacteria. As a result, peptide 11 formed a stable helical structure in solution, and possessed potent antimicrobial activities against both Gram-positive and Gram-negative bacteria without significant cytotoxicity.
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Affiliation(s)
- Chihiro Goto
- National Institute of Health Sciences, 3-25-26, Tonomachi, Kawasaki-ku, Kawasaki-shi, Kanagawa, 210-9501, Japan.,Graduate School of Medical Health Sciences, Yokohama City University, Yokohama-shi, Kanagawa, 230-0045, Japan
| | - Motoharu Hirano
- National Institute of Health Sciences, 3-25-26, Tonomachi, Kawasaki-ku, Kawasaki-shi, Kanagawa, 210-9501, Japan
| | - Katsuhiko Hayashi
- National Institute of Health Sciences, 3-25-26, Tonomachi, Kawasaki-ku, Kawasaki-shi, Kanagawa, 210-9501, Japan
| | - Yutaka Kikuchi
- National Institute of Health Sciences, 3-25-26, Tonomachi, Kawasaki-ku, Kawasaki-shi, Kanagawa, 210-9501, Japan.,Department of Nutrition, Chiba Prefectural University of Health Sciences University, 2-10-1 Wakaba, Mihama-ku, Chiba, 261-0014, Japan
| | - Yukiko Hara-Kudo
- National Institute of Health Sciences, 3-25-26, Tonomachi, Kawasaki-ku, Kawasaki-shi, Kanagawa, 210-9501, Japan
| | - Takashi Misawa
- National Institute of Health Sciences, 3-25-26, Tonomachi, Kawasaki-ku, Kawasaki-shi, Kanagawa, 210-9501, Japan
| | - Yosuke Demizu
- National Institute of Health Sciences, 3-25-26, Tonomachi, Kawasaki-ku, Kawasaki-shi, Kanagawa, 210-9501, Japan.,Graduate School of Medical Health Sciences, Yokohama City University, Yokohama-shi, Kanagawa, 230-0045, Japan
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10
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Tu L, Wang D, Li Z. Design and Synthetic Strategies for Helical Peptides. Methods Mol Biol 2019; 2001:107-31. [PMID: 31134570 DOI: 10.1007/978-1-4939-9504-2_7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Abnormal protein-protein interactions (PPIs) are the basis of multiple diseases, and the large and shallow PPI interfaces make the target "undruggable" for traditional small molecules. Peptides, emerging as a new therapeutic modality, can efficiently mimic PPIs with their large scaffolds. Natural peptides are flexible and usually have poor serum stability and cell permeability, features that limit their further biological applications. To satisfy the clinical application of peptide inhibitors, many strategies have been developed to constrain peptides in their bioactive conformation. In this report, we describe several classic methods used to constrain peptides into a fixed secondary structure which could significantly improve their biophysical properties.
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11
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Priest ER, Longcope DW. Flux-Rope Twist in Eruptive Flares and CMEs: Due to Zipper and Main-Phase Reconnection. Sol Phys 2017; 292:25. [PMID: 32355368 PMCID: PMC7175706 DOI: 10.1007/s11207-016-1049-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2016] [Accepted: 12/29/2016] [Indexed: 05/23/2023]
Abstract
The nature of three-dimensional reconnection when a twisted flux tube erupts during an eruptive flare or coronal mass ejection is considered. The reconnection has two phases: first of all, 3D "zipper reconnection" propagates along the initial coronal arcade, parallel to the polarity inversion line (PIL); then subsequent quasi-2D "main-phase reconnection" in the low corona around a flux rope during its eruption produces coronal loops and chromospheric ribbons that propagate away from the PIL in a direction normal to it. One scenario starts with a sheared arcade: the zipper reconnection creates a twisted flux rope of roughly one turn ( 2 π radians of twist), and then main-phase reconnection builds up the bulk of the erupting flux rope with a relatively uniform twist of a few turns. A second scenario starts with a pre-existing flux rope under the arcade. Here the zipper phase can create a core with many turns that depend on the ratio of the magnetic fluxes in the newly formed flare ribbons and the new flux rope. Main phase reconnection then adds a layer of roughly uniform twist to the twisted central core. Both phases and scenarios are modeled in a simple way that assumes the initial magnetic flux is fragmented along the PIL. The model uses conservation of magnetic helicity and flux, together with equipartition of magnetic helicity, to deduce the twist of the erupting flux rope in terms the geometry of the initial configuration. Interplanetary observations show some flux ropes have a fairly uniform twist, which could be produced when the zipper phase and any pre-existing flux rope possess small or moderate twist (up to one or two turns). Other interplanetary flux ropes have highly twisted cores (up to five turns), which could be produced when there is a pre-existing flux rope and an active zipper phase that creates substantial extra twist.
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Affiliation(s)
- E. R. Priest
- School of Mathematics and Statistics, University of St. Andrews, Fife, KY16 9SS Scotland UK
| | - D. W. Longcope
- Dept. of Physics, Montana State University, Bozeman, MT USA
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12
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Abstract
Charged single alpha-helices (CSAHs) constitute a rare structural motif. CSAH is characterized by a high density of regularly alternating residues with positively and negatively charged side chains. Such segments exhibit unique structural properties; however, there are only a handful of proteins where its existence is experimentally verified. Therefore, establishing a pipeline that is capable of predicting the presence of CSAH segments with a low false positive rate is of considerable importance. Here we describe a consensus-based approach that relies on two conceptually different CSAH detection methods and a final filter based on the estimated helix-forming capabilities of the segments. This pipeline was shown to be capable of identifying previously uncharacterized CSAH segments that could be verified experimentally. The method is available as a web server at http://csahserver.itk.ppke.hu and also a downloadable standalone program suitable to scan larger sequence collections.
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Affiliation(s)
- Dániel Dudola
- Faculty of Information Technology and Bionics, Pázmány Péter Catholic University, Práter u. 50/A, Budapest, 1083, Hungary
| | - Gábor Tóth
- Department of Medical and Biological Sciences, National Research, Development and Innovation Office, Budapest, Hungary
| | - László Nyitray
- Department of Biochemistry, Eötvös Loránd University, Budapest, Hungary
| | - Zoltán Gáspári
- Faculty of Information Technology and Bionics, Pázmány Péter Catholic University, Práter u. 50/A, Budapest, 1083, Hungary.
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13
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Zhang H, Xin X, Sun J, Zhao L, Shen J, Song Z, Yuan S. Self-assembled chiral helical nanofibers by amphiphilic dipeptide derived from d- or l-threonine and application as a template for the synthesis of Au and Ag nanoparticles. J Colloid Interface Sci 2016; 484:97-106. [PMID: 27592190 DOI: 10.1016/j.jcis.2016.08.052] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2016] [Revised: 08/19/2016] [Accepted: 08/19/2016] [Indexed: 12/20/2022]
Abstract
The discovery of a class of self-assembling peptides that spontaneously undergo self-organization into well-ordered structures opened a new avenue for molecular fabrication of biological materials. In this paper, the structure controlled helical nanofibers were prepared by two artificial β-sheet dipeptides with long alkyl chains derived from l- and d-threonine (Thr) and sodium hydroxide (NaOH). These helical nanofibers have been characterized using transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), circular dichroism (CD), Fourier transform infrared (FT-IR) spectroscopy, and X-ray powder diffraction (XRD). It was demonstrated that the helicity of the nanofibers could be easily controlled by changing the chirality of the constituent amino acids in the peptide species (d- or l-threonine). Moreover, the hydrogen bonding interactions between the amide groups as well as the hydrophobic interactions among the alkyl chains play important roles in the self-assembly process. It also can be observed that with the passage of time, the hydrogen bonding interactions between the individual nanofiber induced the conversion from nanofibers to nanobelts. Particularly, gold and silver nanoparticles performed good catalytic ability were synthesized using the assembled nanofibers as template.
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Affiliation(s)
- Han Zhang
- Key Laboratory of Colloid and Interface Chemistry (Shandong University), Ministry of Education, Shanda Nanlu No. 27, Jinan 250100, PR China
| | - Xia Xin
- Key Laboratory of Colloid and Interface Chemistry (Shandong University), Ministry of Education, Shanda Nanlu No. 27, Jinan 250100, PR China; National Engineering Technology Research Center for Colloidal Materials, Shandong University, Shanda Nanlu No. 27, Jinan 250100, PR China.
| | - Jichao Sun
- Key Laboratory of Colloid and Interface Chemistry (Shandong University), Ministry of Education, Shanda Nanlu No. 27, Jinan 250100, PR China
| | - Liupeng Zhao
- Key Laboratory of Colloid and Interface Chemistry (Shandong University), Ministry of Education, Shanda Nanlu No. 27, Jinan 250100, PR China
| | - Jinglin Shen
- Key Laboratory of Colloid and Interface Chemistry (Shandong University), Ministry of Education, Shanda Nanlu No. 27, Jinan 250100, PR China
| | - Zhaohua Song
- National Engineering Technology Research Center for Colloidal Materials, Shandong University, Shanda Nanlu No. 27, Jinan 250100, PR China
| | - Shiling Yuan
- Key Laboratory of Colloid and Interface Chemistry (Shandong University), Ministry of Education, Shanda Nanlu No. 27, Jinan 250100, PR China.
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14
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Chiastra C, Iannaccone F, Grundeken MJ, Gijsen FJH, Segers P, De Beule M, Serruys PW, Wykrzykowska JJ, van der Steen AFW, Wentzel JJ. Coronary fractional flow reserve measurements of a stenosed side branch: a computational study investigating the influence of the bifurcation angle. Biomed Eng Online 2016; 15:91. [PMID: 27495804 PMCID: PMC4974683 DOI: 10.1186/s12938-016-0211-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Accepted: 07/20/2016] [Indexed: 12/31/2022] Open
Abstract
Background Coronary hemodynamics and physiology specific for bifurcation lesions was not well understood. To investigate the influence of the bifurcation angle on the intracoronary hemodynamics of side branch (SB) lesions computational fluid dynamics simulations were performed. Methods A parametric model representing a left anterior descending—first diagonal coronary bifurcation lesion was created according to the literature. Diameters obeyed fractal branching laws. Proximal and distal main branch (DMB) stenoses were both set at 60 %. We varied the distal bifurcation angles (40°, 55°, and 70°), the flow splits to the DMB and SB (55 %:45 %, 65 %:35 %, and 75 %:25 %), and the SB stenoses (40, 60, and 80 %), resulting in 27 simulations. Fractional flow reserve, defined as the ratio between the mean distal stenosis and mean aortic pressure during maximal hyperemia, was calculated for the DMB and SB (FFRSB) for all simulations. Results The largest differences in FFRSB comparing the largest and smallest bifurcation angles were 0.02 (in cases with 40 % SB stenosis, irrespective of the assumed flow split) and 0.05 (in cases with 60 % SB stenosis, flow split 55 %:45 %). When the SB stenosis was 80 %, the difference in FFRSB between the largest and smallest bifurcation angle was 0.33 (flow split 55 %:45 %). By describing the ΔPSB−QSB relationship using a quadratic curve for cases with 80 % SB stenosis, we found that the curve was steeper (i.e. higher flow resistance) when bifurcation angle increases (ΔP = 0.451*Q + 0.010*Q2 and ΔP = 0.687*Q + 0.017*Q2 for 40° and 70° bifurcation angle, respectively). Our analyses revealed complex hemodynamics in all cases with evident counter-rotating helical flow structures. Larger bifurcation angles resulted in more pronounced helical flow structures (i.e. higher helicity intensity), when 60 or 80 % SB stenoses were present. A good correlation (R2 = 0.80) between the SB pressure drop and helicity intensity was also found. Conclusions Our analyses showed that, in bifurcation lesions with 60 % MB stenosis and 80 % SB stenosis, SB pressure drop is higher for larger bifurcation angles suggesting higher flow resistance (i.e. curves describing the ΔPSB−QSB relationship being steeper). When the SB stenosis is mild (40 %) or moderate (60 %), SB resistance is minimally influenced by the bifurcation angle, with differences not being clinically meaningful. Our findings also highlighted the complex interplay between anatomy, pressure drops, and blood flow helicity in bifurcations.
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Affiliation(s)
- Claudio Chiastra
- Department of Cardiology, Biomedical Engineering, Erasmus MC, Rotterdam, The Netherlands.,Laboratory of Biological Structure Mechanics (LaBS), Department of Chemistry, Materials and Chemical Engineering "Giulio Natta", Politecnico di Milano, Milan, Italy
| | - Francesco Iannaccone
- Department of Cardiology, Biomedical Engineering, Erasmus MC, Rotterdam, The Netherlands.,IbiTech-bioMMeda, Department of Electronics and Information Systems iMinds Medical IT, Ghent University, Ghent, Belgium
| | - Maik J Grundeken
- The Heart Center, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Frank J H Gijsen
- Department of Cardiology, Biomedical Engineering, Erasmus MC, Rotterdam, The Netherlands
| | - Patrick Segers
- IbiTech-bioMMeda, Department of Electronics and Information Systems iMinds Medical IT, Ghent University, Ghent, Belgium
| | - Matthieu De Beule
- IbiTech-bioMMeda, Department of Electronics and Information Systems iMinds Medical IT, Ghent University, Ghent, Belgium.,FEops bvba, Ghent, Belgium
| | - Patrick W Serruys
- International Centre for Circulatory Health, NHLI, Imperial College London, London, UK
| | - Joanna J Wykrzykowska
- The Heart Center, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | | | - Jolanda J Wentzel
- Department of Cardiology, Biomedical Engineering, Erasmus MC, Rotterdam, The Netherlands.
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Vorobtsova N, Chiastra C, Stremler MA, Sane DC, Migliavacca F, Vlachos P. Effects of Vessel Tortuosity on Coronary Hemodynamics: An Idealized and Patient-Specific Computational Study. Ann Biomed Eng 2016; 44:2228-39. [PMID: 26498931 DOI: 10.1007/s10439-015-1492-3] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2015] [Accepted: 10/16/2015] [Indexed: 01/09/2023]
Abstract
Although coronary tortuosity can influence the hemodynamics of coronary arteries, the relationship between tortuosity and flow has not been thoroughly investigated partly due to the absence of a widely accepted definition of tortuosity and the lack of patient-specific studies that analyze complete coronary trees. Using a computational approach we investigated the effects of tortuosity on coronary flow parameters including pressure drop, wall shear stress, and helical flow strength as measured by helicity intensity. Our analysis considered idealized and patient-specific geometries. Overall results indicate that perfusion pressure decreases with increased tortuosity, but the patient-specific results show that more tortuous vessels have higher physiological wall shear stress values. Differences between the idealized and patient-specific results reveal that an accurate representation of coronary tortuosity must account for all relevant geometric aspects, including curvature imposed by the heart shape. The patient-specific results exhibit a strong correlation between tortuosity and helicity intensity, and the corresponding helical flow contributes directly to the observed increase in wall shear stress. Therefore, helicity intensity may prove helpful in developing a universal parameter to describe tortuosity and assess its impact on patient health. Our data suggest that increased tortuosity could have a deleterious impact via a reduction in coronary perfusion pressure, but the attendant increase in wall shear stress could afford protection against atherosclerosis.
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