1,721,045 research outputs found
Can dispersion forces govern aromatic stacking in an organic solvent?
No full textExperimental support for the dominance of van der Waals dispersion forces in aromatic stacking interactions occurring in organic solution is surprisingly limited. Here, we have examined the size-dependence of aromatic stacking in an organic solvent. The interaction energy was found to vary by ~7.5 kJ mol–1 on going from a phenyl-phenyl to an anthracene-pyrene stack. Strikingly, the experimental data were highly correlated with dispersion energies determined using symmetry-adapted perturbation theory (SAPT), while the induction, exchange, electrostatic and solvation energy components correlated poorly. Both the experimental data and the SAPT-dispersion energies gave high-quality correlations with the change in solvent accessible area upon complexation. Thus, the size-dependence of aromatic stacking interactions is consistent with the dominance of van der Waals dispersion forces even in the presence of a competing polarizable solvent..xyx coordinates of minimised complex geometries, NMR characterisation and titration data
DNA modulates solvent isotope effects in a nanopore
No full textHere we investigate the modulation of solvent isotope effects by the entry of DNA molecules into individual α-haemolysin nanopores. Solvent isotope effects in D2O versus H2O were enhanced (kH/kD ≈ 1.6) compared to the bulk (kH/kD ≈ 1.2), except when the pore was most blocked (kH/kD ≤ 1.1).Ion current recordings, raw data as recorded in PClamp 10.2 software. NOTE: Some files are in Axon(TM) Binary Format (ABF), a format proprietary to Molecular Devices
DNA modulates solvent isotope effects in a nanopore
No full textIon current recordings, raw data as recorded in PClamp 10.2 software. NOTE: Some files are in Axon(TM) Binary Format (ABF), a format proprietary to Molecular Devices.Here we investigate the modulation of solvent isotope effects by the entry of DNA molecules into individual α-haemolysin nanopores. Solvent isotope effects in D2O versus H2O were enhanced (kH/kD ≈ 1.6) compared to the bulk (kH/kD ≈ 1.2), except when the pore was most blocked (kH/kD ≤ 1.1).Watson, Matthew; Cockroft, Scott. (2015). DNA modulates solvent isotope effects in a nanopore, 2013-2015 [dataset]. University of Edinburgh, EaStCHEM School of Chemistry. http://dx.doi.org/10.7488/ds/277
Structural evidence for the covalent modification of FabH by 4,5-dichloro-1,2-dithiol-3-one (HR45)
No full textWe use mass spectrometry analysis and molecular modelling to show the established antimicrobial inhibitor 4,5-dichloro-1,2-dithiol-3-one (HR45) acts by forming a covalent adduct with the target β-ketoacyl-ACP synthase III (FabH). The 5-chloro substituent directs attack of the essential active site thiol (C112) via a Michael-type addition elimination reaction mechanism.Ekström, Alex; Kelly, Van; Marles-Wright, Jon; Cockroft, Scott; Campopiano, Dominic. (2017). Structural evidence for the covalent modification of FabH by 4,5-dichloro-1,2-dithiol-3-one (HR45), [dataset]. University of Edinburgh. School of Chemistry. http://dx.doi.org/10.7488/ds/2103
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Robust capsules for biomedical applications
Full text linkMetallosupramolecular capsules represent a facile route to three-dimensional structures that possess
a central cavity. The synthetic accessibility is provided by self-assembly, which allows carefully
designed components to form complex three-dimensional structures under thermodynamic control.
The cavities allow the non-covalent binding of guests, changing their properties in a quick and
reversible manner, thereby making capsules promising for catalytic, storage, extraction and
biomedical applications.
However, the requirement for thermodynamic control makes capsules susceptible to degradation by
changes in conditions such as heat, dilution, pH, or the presence of nucleophiles, making them
insufficiently robust for biomedical applications. This project constitutes the continuation of a project
which sought to synthesise more robust capsules. This was achieved by exploiting the cobalt II/III
redox couple, assembling the tetrahedra with labile cobalt (II) and then oxidatively “locking” them as
inert cobalt (III). This led to the development of the tetrahedron C19, which proved stable over a range
of temperatures, dilutions and pH values. C19 was shown to bind the common SPECT imaging agent
precursor [99mTc]TcO4
-, suggesting radioimaging as a potential application of the cage.
During this project, C19 was found to be degraded in biological environments by reducing agents such
as glutathione. Therefore, a ligand with electron donating amine groups, L20, was developed to
increase the strength of interaction with metal centres, and overall stability. A two-step assembly
using C19 as a template and substituting L20 into this prearranged tetrahedron was required to
prevent kinetically trapped byproducts. The resulting cage, C20, was found to have increased
resistance to biological conditions relative to C19, and was able to significantly alter the uptake of
[99mTc]TcO4
- in vivo, proving the potential of the system to act as a delivery agent.
Further functionalisation of C20 was explored to allow bioconjugation and targeting. To this end, the
ligand was functionalised with a terminal alkyne to allow versatile Huisgen “click” functionalisation. A
methyl ether was trialled as an alternative to the amines of L20, and the resulting ligand, L38, was
found to confer similar properties onto its assemblies. Incorporation of alkyne Raman labels into a
cage allowed stimulated Raman scattering imaging of its interaction with cells.
Overall, a robust cage system capable of retaining and altering the uptake of a significant diagnostic
agent in vivo was developed. Progress was also made towards improving the properties, targeting and
monitoring of the system
Non-covalent interactions in solution
Full text linkNon-covalent interactions taking place in solution are essential in chemical and
biological systems. The solvent environment plays an important role in determining
the geometry and stability of interactions. This thesis examines aromatic stacking
interactions, alkyl-alkyl interactions, edge-to-face aromatic interactions, halogen
bonds and hydrogen…hydrogen interactions in solution.
Chapter 1 briefly introduces the different classes of non-covalent interactions, in
addition to the state-of-the-art models and methods for investigating these weak
interactions. The chapter finishes with a focus on dispersion interaction in alkanes
and arenes.
Chapter 2 investigates dispersion interactions between stacked aromatics in solution
using a new class of complexes and thermodynamic double mutant cycles (DMCs).
In extended aromatics, dispersion was detected as providing a small but significant
contribution to the overall stacking free energies.
Chapter 3 concerns the experimental measurement of alkyl-alkyl dispersion
interactions in a wide range of solvents using Wilcox torsion balances. The
contribution of dispersion interactions to alkyl-alkyl association was shown to be
very small, with DMC, QSPR method and Hunter's solvation model.
Chapter 4 studies edge-to-face aromatic interactions in series of solvents. In the open
system, edge-to-face aromatic interactions were found to be sensitive to the solvent
environment. The solvent effects were complicated and cannot be rationalised by a
single parameter. Further analysis is needed.
Chapter 5 describes a preliminary approach to investigate organic halogen…π
interactions in solution using supramolecular complexes and torsion balances.
Chapter 6 is a preliminary investigation of the ability of hydrogen atoms to act as H
bond acceptors in silane compounds. Computations and 1H NMR demonstrated a
weak interaction between silane and perfluoro-tert-butanol
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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