Browsing by Author "Dura, JA"

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    A neutron reflectivity study of the interfacial and thermal behaviour of surface-attached hairpin DNA
    (Royal Society of Chemistry, 2011-01-01) Kjallman, THM; Nelson, A; James, M; Dura, JA; Travas-Sejdic, J; McGillivray, DJ
    Mixed self-assembled monolayers (mSAMs) have been successfully utilised as platforms for gene sensors, employing optical as well as electrochemical means of detection. Probe density is one of the most important parameters in the construction of such a sensor and thus a fundamental understanding of the structure within the mSAM is vital. In this work, the interfacial behaviour of mixed SAMs, where short PEG oligomers co-adsorbed to the surface with hairpin structured oligonucleotide (ODN) probes, has been investigated. The neutron reflectivity of the mixed SAMs was measured at differing HPP : PEG ratios, and through two routes of formation, to elucidate the effect of controlled HPP surface density on surface conformation of the probes and on the final hybridised ODN-HPP construct. General conclusions regarding the structure of the investigated SAMs could be drawn from determined thickness and volume fraction values and conformational changes in the mSAM, induced by hybridisation with complementary ODN, were also detected. An investigation of the melting behaviour of the surface-attached HPPs was also conducted with polarised neutron reflectivity and clear signs of melting were observed in the reflectivity and the SLD profiles around 45 [degree]C.© 2011, Royal Society of Chemistry
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    Round robin sample for neutron reflectometry
    (International Conference on Neutron Scattering, 2017-07-12) Nelson, A; Dura, JA; Majkrzak, CF; Newby, R
    Were a scientist to visit one of the many neutron and X-ray reflectometers in use around the world they would expect that if the same sample were measured on any of those instruments the results derived from the experiment would be comparable and reproducible. Each user measurement relies on many assumptions, including: good calibration of the instrument, valid measurement processes, valid data reduction algorithms, good knowledge of resolution functions, etc. It would be unfortunate if data measured across a class of instruments were not comparable and reproducible as a large body of research into interfaces is underpinned by these techniques. The small-angle neutron scattering community investigated this recently [1], with a series of measurements of a common sample at different facilities, spanning a range of instruments with different design characteristics. This round robin was able to verify the reproducibility and reliability of the instruments taking part, as well as highlighting areas for improvement. We have therefore decided to initiate a similar process for neutron and X-ray reflectometers. To date the project has identified, synthesised, and characterised two suitable samples that lie at opposite ends of the typical size range studied by reflectometry. Here we give a brief overview of these preliminary characterisations, and propose an experimental design and methodology for instruments taking part.