Electron-vibration-vibration two-dimensional infrared spectroscopy as a structural probe of interactions in proteins and DNA

• Main Author: Sowley, Hugh Richard
• Other Authors: Klug, David ; Willison, Keith
• Published: Imperial College London 2017
• Subjects: 540
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.739673

Modern structural biology has a number of powerful tools but despite this there are a number of problems in structural biology that these methods are unable to address. Some of these pertain to the need for large number for precise comparative structures for the drug discovery process. EVV 2DIR has the potential to fill some of these gaps, having the potential to determine molecular binding geometry. This thesis presents the first steps in exploring the potential of EVV 2DIR to be applied to the analysis of the structure of inhibitor- protein binding and presents the first EVV spectra of an inhibitor-protein complex. For the inhibitor-protein complex studied, six vibrational couplings between seven vibrational modes were identified exclusively upon complex formation due to interactions between the two molecules. Experimental spectra were compared with ab initio calculations to assign these vibrations to specific motions on both the inhibitor and protein molecules. EVV 2DIR cross peaks can be sensitive to the geometry of the interacting groups which produce them. By measuring the spectra of the inhibitor-protein complex using two different polarisation schemes, quantitative comparison between calculated and experimental spectra was made possible. This allowed for the prospect of using calculation aided EVV 2DIR to determine the structure of protein-ligand complexes to be explored. This thesis also presents the first EVV spectra of DNA. EVV 2DIR spectra were measured of duplex and G-quadruplex structures and compared with those of unstructured controls. In the absence of calculated spectra, assignments were made to some of the spectral features observed. EVV 2DIR was shown to be sensitive to the structural form of the DNA samples, containing cross peaks indicative of WatsonCrick base pairing, G-quadruplex formation and glycosidic bond conformation. The DNA spectra contained many unassigned peaks leaving open the possibility to assign many more structural indicators.