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Berlin Brandenburg

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  • 1
    Language: English
    In: Journal of the American Chemical Society, 10 September 2014, Vol.136(36), pp.12516-9
    Description: The identification of effective polypeptide ligands for magnetic iron oxide nanoparticles (IONPs) could considerably accelerate the high-throughput analysis of IONP-based reagents for imaging and cell labeling. We developed a procedure for screening IONP ligands and applied it to compare candidate peptides that incorporated carboxylic acid side chains, catechols, and sequences derived from phage display selection. We found that only l-3,4-dihydroxyphenylalanine (DOPA)-containing peptides were sufficient to maintain particles in solution. We used a DOPA-containing sequence motif as the starting point for generation of a further library of over 30 peptides, each of which was complexed with IONPs and evaluated for colloidal stability and magnetic resonance imaging (MRI) contrast properties. Optimal properties were conferred by sequences within a narrow range of biophysical parameters, suggesting that these sequences could serve as generalizable anchors for formation of polypeptide-IONP complexes. Differences in the amino acid sequence affected T1- and T2-weighted MRI contrast without substantially altering particle size, indicating that the microstructure of peptide-based IONP coatings exerts a substantial influence and could be manipulated to tune properties of targeted or responsive contrast agents. A representative peptide-IONP complex displayed stability in biological buffer and induced persistent MRI contrast in mice, indicating suitability of these species for in vivo molecular imaging applications.
    Keywords: Contrast Media -- Chemistry ; Ferric Compounds -- Chemistry ; Magnetite Nanoparticles -- Chemistry ; Peptides -- Chemistry
    ISSN: 00027863
    E-ISSN: 1520-5126
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  • 2
    Language: English
    In: Bioorganic & Medicinal Chemistry, 15 January 2012, Vol.20(2), pp.769-774
    Description: Magnetic resonance imaging (MRI) contrast agents are effective tools in both medical diagnosis and life science research. Various smart contrast agents have been developed for the visualization of biological phenomena. These contrast agents have molecular switches that increase or reduce MRI signal intensity in response to the target biological reaction. Therefore, novel approaches to the design of molecular switches for versatile in vivo studies using MRI are eagerly anticipated. Here, we report one such approach for the development of molecular switches based on morphological changes of pH-responsive polymers. We designed and synthesized three types of contrast agents based on a linear homopolymer or spherical copolymers with two different cross-linking degrees. The relaxivity measurements showed that these agents have molecular switches that respond to pH changes, and fluorescence studies indicated that these switches are based on the alteration of the molecular tumbling caused by pH-responsive morphological changes. As a result, the spherical polymers possess promising characteristics for the development of switchable MRI contrast agents.
    Keywords: Mri ; Contrast Agent ; Ph-Responsive Polymer ; Rotational Correlation Time ; Molecular Switch ; Medicine ; Chemistry ; Anatomy & Physiology
    ISSN: 0968-0896
    E-ISSN: 1464-3391
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  • 3
    Language: English
    In: The Lancet, 20 October 2012, Vol.380(9851), pp.1444-1444
    Description: At our hospital, he had an immediate reduction in systolic blood pressure of 40 mm Hg and loss of consciousness after standing up after lying in a supine position for 5 min. The differential diagnosis for persistent hiccups includes CNS disease, and gastrointestinal, thoracic, cardiac, and toxic-metabolic or drug-related disorders.4,5 Neuromyelitis optica should be considered and anti-AQP4 antibody tested for in patients with unexplained persistent hiccups, even if findings from CNS MRI are normal.
    Keywords: Medicine
    ISSN: 0140-6736
    E-ISSN: 1474-547X
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  • 4
    Language: English
    In: Journal of Power Sources, Feb 1, 2014, Vol.247, p.391(5)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jpowsour.2013.08.123 Byline: Ayuko Kitajou, Junpei Yamaguchi, Satoshi Hara, Shigeto Okada Abstract: The structure changes of iron disulfide (FeS.sub.2) during discharge/charge process were investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and synchrotron-based X-ray adsorption near the edge structure (XANES). Although the cyclability of the FeS.sub.2/Na battery is poor, FeS.sub.2/Na battery has a large first discharge capacity of 758 mA h g.sup.-1. It corresponds to 85% of the theoretical capacity based on the 4.0 Na reaction per FeS.sub.2 (893 mA h g.sup.-1). According to the Fe K-edge XANES spectra of discharged FeS.sub.2 pellets, there were no clear traces of iron valence change. However, the clear S K-edge jump shifted to lower energy with increasing Na content in FeS.sub.2. This is because the binding energy of S 1s electrons decrease as the oxidation number of S decreases, suggesting that the charge neutrality of the cathode after 2.0 Na discharge is kept by an S valence change from (S-S).sup.2- to S.sup.2-. Moreover, Na.sub.2S diffraction peaks were detected at the 3.0 Na discharged state as a trace of Na conversion reaction in the FeS.sub.2 cathode. Author Affiliation: (a) Research and Education Center of Carbon Resources, Kyushu University, 6-1 Kasuga-koen, Kasuga 816-8580, Japan (b) Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, 6-1 Kasuga-koen, Kasuga 816-8580, Japan (c) Institute for Materials Chemistry and Engineering, Kyushu University, 6-1 Kasuga-koen, Kasuga 816-8580, Japan Article History: Received 24 June 2013; Revised 21 August 2013; Accepted 26 August 2013
    Keywords: Sulfur Compounds ; X-ray Spectroscopy ; Batteries ; Adsorption
    ISSN: 0378-7753
    Source: Cengage Learning, Inc.
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  • 5
    Language: English
    In: Journal of the American Chemical Society, 18 February 2015, Vol.137(6), pp.2247-52
    Description: A solid solution of a 75:25 mixture of tetrabenzoporphyrin (BP) and dichloroacenaphtho[q]tribenzo[b,g,l]porphyrin (CABP) forms when they are generated in a matrix of (dimethyl(o-anisyl)silylmethyl)(dimethylphenylsilylmethyl)[60]fullerene. This solid solution provides structural and optoelectronic properties entirely different from those of either pristine compounds or a mixture at other blending ratios. The use of this BP:CABP solid solution for organic solar cell (OSC) devices resulted in a power conversion efficiency (PCE) value higher by 16 and 300% than the PCE values obtained for the devices using the single donor BP and CABP, respectively, in a planar heterojunction architecture. This increase originates largely from the increase in short circuit current density, and hence by enhanced charge carrier separation at the donor/acceptor interface, which was probably caused by suitable energy level for the solid solution state, where electronic coupling between the two porphyrins occurred. The results suggest that physical and chemical modulation in solid solution is beneficial as an operationally simple method to enhance OSC performance.
    Keywords: Feste Lösung ; Porphyrin ; Fulleren ; Organische Solarzelle ; Energieumwandlung ; Separation ; Heteroübergang ; Energieniveau ; Mischungsverhältnis ; Kurzschlussstrom ; Chemistry;
    ISSN: 00027863
    E-ISSN: 1520-5126
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  • 6
    Language: English
    In: Journal of the American Chemical Society, 21 July 2010, Vol.132(28), pp.9524-5
    Description: A novel photocontrolled compound release system using liposomes and a caged antimicrobial peptide was developed. The caged antimicrobial peptide was activated by UV irradiation, resulting in the formation of pores on the liposome surface to release the contained fluorophores. The compound release could be observed using fluorescence measurements and time-lapse fluorescence microscopy. UV irradiation resulted in a quick release of the inclusion compounds (within 1 min in most cases) under simulated physiological conditions. The proposed system is expected to be applicable in a wide range of fields from cell biology to clinical sciences.
    Keywords: Photochemistry ; Anti-Infective Agents -- Administration & Dosage ; Peptides -- Administration & Dosage
    ISSN: 00027863
    E-ISSN: 1520-5126
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  • 7
    Language: English
    In: Journal of the American Chemical Society, 08 January 2014, Vol.136(1), pp.466-73
    Description: Whereas a statistical average of molecular ensembles has been the conventional source of information on molecular structures, atomic resolution movies of single organic molecules obtained by single-molecule real-time transmission electron microscopy have recently emerged as a new tool to study the time evolution of the structures of individual molecules. The present work describes a proof-of-principle study of the determination of the conformation of each C-C bond in single perfluoroalkyl fullerene molecules encapsulated in a single-walled carbon nanotube (CNT) as well as those attached to the outer surface of a carbon nanohorn (CNH). Analysis of 82 individual molecules in CNTs under a 120 kV electron beam indicated that 6% of the CF2-CF2 bonds and about 20% of the CH2-CH2 bonds in the corresponding hydrocarbon analogue are in the gauche conformation. This comparison qualitatively matches the known conformational data based on time- and molecular-average as determined for ensembles. The transmission electron microscopy images also showed that the molecules entered the CNTs predominantly in one orientation. The molecules attached on a CNH surface moved more freely and exhibited more diverse conformation than those in a CNT, suggesting the potential applicability of this method for the determination of the dynamic shape of flexible molecules and of detailed conformations. We observed little sign of any decomposition of the specimen molecules, at least up to 10(7) e·nm(-2) (electrons/nm(2)) at 120 kV acceleration voltage. Decomposition of CNHs under irradiation with a 300 kV electron beam was suppressed by cooling to 77 K, suggesting that the decomposition is a chemical process. Several lines of evidence suggest that the graphitic substrate and the attached molecules are very cold.
    Keywords: Chemistry;
    ISSN: 00027863
    E-ISSN: 1520-5126
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  • 8
    Language: English
    In: Advanced Materials, May 21, 2014, Vol.26(19), p.2989(4)
    Description: To purchase or authenticate to the full-text of this article, please visit this link: http://onlinelibrary.wiley.com/doi/10.1002/adma.201305018/abstract Byline: Satoshi Okada, Shin Mizukami, Takao Sakata, Yutaka Matsumura, Yoshichika Yoshioka, Kazuya Kikuchi Keywords: magnetic resonance imaging; ratiometric sensors; contrast agents; core-shell nanoparticles; pH-responsive polymers ***** No abstract is available for this article. ***** Supporting information: Additional Supporting Information may be found in the online version of this article As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. CAPTION(S): Supplementary Supplementary Supplementary Supplementary Supplementary
    Keywords: Polymers ; Nanoparticles ; Ph ; Magnetic Resonance Imaging ; Sensors
    ISSN: 0935-9648
    Source: Cengage Learning, Inc.
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  • 9
    In: Chemical Communications, 2010, Vol.46(14), pp.2462-2464
    Description: A strategy involving palladium-catalysed aromatic C–H functionalisation/intramolecular alkenylation provides a convenient and direct synthesis of 3-alkylideneoxindoles. In the presence of 5 mol% of PdCl 2 MeCN 2 and AgOCOCF 3 , a wide variety of N -cinnamoylanilines gave 3-alkylideneoxindoles in moderate to good yield.
    Keywords: Alkenes -- Chemistry ; Indoles -- Chemical Synthesis ; Palladium -- Chemistry;
    ISSN: 1359-7345
    E-ISSN: 1364-548X
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  • 10
    In: Chemical Communications, 2014, Vol.50(27), pp.3595-3598
    Description: Magnetic nanoparticle-based sensors for MRI have been accelerated to a timescale of seconds using densely-functionalized particles of small size. Parameters that increase response rates also result in large nuclear magnetic relaxation rate and light scattering changes, allowing signals to be detected almost immediately after changes in calcium concentration.
    Keywords: Parameters ; Time ; Calcium ; Sensors ; Self Assembly ; Nanoelectronics ; Magnetic Relaxation ; Nanostructure ; Miscellaneous Sciences (So) ; Components and Materials (General) (Ea);
    ISSN: 1359-7345
    E-ISSN: 1364-548X
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