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A new reference material for UV-visible circular dichroism spectroscopy.

Damianoglou, A*; Crust, E J*; Hicks, M*; Howson, S E*; Knight, A E; Ravi, J; Scott, P*; Rodger, A* (2008) A new reference material for UV-visible circular dichroism spectroscopy. Chirality, 20 (9). pp. 1029-1038.

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In order to obtain accurate and consistent measurements from circular dichroism (CD) instruments, it is important that they are properly calibrated, and that this calibration is checked regularly. The comparability of circular dichroism data among laboratories is a recognised problem. This problem is partly due to the characteristics of the available reference materials, which typically only give peaks in one or two spectral regions, and often have issues concerning purity and stability. Currently either camphor sulfonic acid (CSA) or ammonium camphor sulfonate (ACS) are used for calibration of CD machines. The latter is an unstable, slightly hygroscopic secondary standard compound with only one characterized CD band. The former is the primary standard; it is the very hygroscopic acid. Only one enantiomer is readily available for these standards. We have synthesised a new reference material for CD, Na[Co(EDDS)].H2O (EDDS= N,N-ethylenediaminedisuccinic acid) which addresses these problems. The material is extremely stable and is available in both enantiomeric forms. The CD spectrum of Na[Co(EDDS)].H2O has nine distinct peaks between 180 nm and 599 nm. The two enantiomers R,R- and S,S- thus fulfil the principal requirements for CD calibration chemical standards and have the potential to be used to ensure good practice in the measurement of CD data providing two spectra, which are equal in magnitude and opposite in sign for a given concentration and path length. We have carried out an inter-laboratory comparison of measurements made using this material, and show how it can be used to improve CD comparability between laboratories. A fitting algorithm has been developed to assess CD spectropolarimeter performance between 750 nm and 178 nm against the standard data established in this work. This could be the basis of a formal quality assurance process once criteria for performance have been decided.

Item Type: Article
Keywords: circular dichroism, spectroscopy, protein structure, calibration
Subjects: Biotechnology
Biotechnology > Bio-Diagnostics
Last Modified: 02 Feb 2018 13:15
URI: http://eprintspublications.npl.co.uk/id/eprint/4208

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