PhD (Durham University), Ramsay Memorial Fellow
Biography
Gareth obtained an MChem degree (Class I) from Warwick University in 2007 and then moved to Durham University where he earned his Ph.D. in 2010 under the supervision of Dr Jan R. R. Verlet. During his time in Durham he designed, constructed and commissioned a state-of-the-art spectrometer for studying the spectroscopy and ultrafast dynamics of molecular anions in the gas phase. This new spectrometer uniquely coupled together the experimental techniques of electrospray ionization, mass spectrometry and time-resolved photoelectron imaging.
Following his Ph.D. he moved back to Warwick University to undertake a postdoctoral research position for 3 years in the group of Dr Vas Stavros. Here he applied both theoretical (ab initio calculations) and experimental (time-resolved velocity map ion imaging) methods to studying ultrafast photodissociation processes in a wide range of heteroaromatic biomolecules and their UV chromophore subunits. During his time at Warwick he was also involved in establishing productive collaborations with the research groups of Prof. Mike Ashfold (Bristol), Prof. Martin Paterson (Heriot-Watt) and Dr Dave Townsend (Heriot-Watt), while continuing to collaborate with Dr Jan Verlet (Durham).
As of 2013, Gareth is a Ramsay Memorial Research Fellow at the University of Bristol where he works with Profs Andrew Orr-Ewing and Mike Ashfold.
Research: Understanding the Effects of UV Radiation on DNA
The motion of atoms (chemical dynamics) in photoexcited electronic states takes place on an ultrafast timeframe of tens to hundreds of femtoseconds (1 fs = 1×10–15 s),1 and these dynamics underpin a myriad of essential biological processes.2 This is exemplified by their pivotal role as ‘natural sunscreens’ in DNA, which protect against the potentially toxic effects of absorbed ultraviolet (UV) solar radiation.3 Until recently these ‘photoprotective’ mechanisms had remained poorly characterised. Only through cutting-edge laser spectroscopy and complementary theoretical modelling, has modern biophysics begun to reveal how these photoprotective mechanisms behave as front-line defences against genetic mutations and carcinogenesis.3,4
Over the last decade, these studies have shown that excited state dynamics are intimately influenced by specific structural motifs within DNA.3 As a result, photoprotective mechanisms in DNA have been broadly classified into dynamics localised to either the base stacking or base pairing arrangements. Within the latter, seminal theoretical models of base pairs imply that UV energy can be defused through proton (H+) exchange within an intermolecular hydrogen bond.5 In addition to activating these photoprotection mechanisms, the interaction of UV radiation with aqueous media inside our bodies cells can also lead to the generation of low energy electrons (0.1 – 2 eV). Upon reacting with DNA, these electrons produce single and double strand breaks in the sugar-phosphate backbones,6 ultimately leading to harmful mutations in our genetic code, although little is currently known about the timescales and mechanism of this process.
Using ultrafast solution-phase transient absorption spectroscopy techniques, the key aims of the research proposed for the duration of the Ramsay Fellowship are to: (i) Further investigate the excited photochemistry of DNA and its constituent building-blocks (e.g. the DNA nucleobases); (ii) Study proton transfer pathways between DNA base pairs and subsequently DNA duplexes; and (iii) Develop novel methods for investigating pathways to DNA damage via both UV radiation absorption and low energy electron attachment.
References
[1] Zewail, J. Phys. Chem. A, 104 (2000) 5660; [2] Sundström, Annu. Rev. Phys. Chem., 59 (2008) 53; [3] Middleton et al., Annu. Rev. Phys. Chem., 60 (2009) 217; [4] Schreier et al., Science, 315 (2007) 625; [5] Abo-Riziq et al., Proc. Natl. Acad. Sci. USA, 102 (2005) 20; [6] J. Simons, Acc. Chem. Res., 39 (2006) 772
*Corresponding author
[29] A multi-pronged comparative study of the ultraviolet photochemistries of 2-, 3- and 4-chlorophenol. S. J. Harris, T. N. V. Karsili, D. Murdock, T. A. A. Oliver, A. M. Wenge, D. K. Zaouris, M. N. R. Ashfold, J. N. Harvey, J. D. Few, S. Gowrie, G. Hancock, G. Spighi, L. Poisson, B. Soep, D. J. Hadden, G. M. Roberts and V. G. Stavros. In preparation
[28]* On the participation of photo-induced N-H bond fission in aqueous adenine at 266 and 220 nm: a combined ultrafast transient electronic and vibrational absorption spectroscopy study. G. M. Roberts, H. J. B. Marroux, M. P. Grubb, M. N. R. Ashfold and A. J. Orr-Ewing. J. Phys. Chem. A, (2014) DOI:10.1021/jp508501w [Front cover article]
[27] Tunneling dynamics of the NH3(A) state observed by time-resolved photoelectron and H-atom kinetic energy spectroscopies. H. Yu, N. L. Evans, A. S. Chatterley, G. M. Roberts, V. G. Stavros and S. Ullrich. J. Phys. Chem. A, 118 (2014) 9438
[26]* Ultrafast photo-induced ligand solvolysis of cis-[Ru(bipyridine)2(nicotinamide)2]2+: experimental and theoretical insight into its photoactivation mechanism. S. E. Greenough, G. M. Roberts, N. A. Smith, M. D. Horbury, R. G. McKinlay, J. M. Zurek, M. J. Paterson, P. J. Sadler and V. G. Stavros. Phys. Chem. Chem. Phys., 16 (2014) 19141 [Front cover article]
[25] Solvent induced conformer specific photochemistry of guaiacol. S. E. Greenough, M. D. Horbury, J. O. F. Thompson, G. M. Roberts, T. N. V. Karsili, B. Marchetti, D. Townsend and V. G. Stavros. Phys. Chem. Chem. Phys., 16 (2014) 16187
[24] Towards understanding photodegradation pathways in lignins: the role of intramolecular hydrogen bonding in excited states. J. D. Young, M. Staniforth, J. C. Dean, G. M. Roberts, F. Mazzoni, T. N. V. Karsili, M. N. R. Ashfold, T. S. Zwier and V. G. Stavros. J. Phys. Chem. Lett., 5 (2014) 2138
[23] Relaxation dynamics of photoexcited dihydroxybenzenes: a comparative study. M. Staniforth, A. S. Chatterley, J. D. Young, G. M. Roberts and V. G. Stavros. Biomedical Spectroscopy and Imaging, 3 (2014) 271
[22] The role of πσ* states in the photochemistry of heteroaromatic biomolecules and their subunits: insights from gas-phase femtosecond spectroscopy. G. M. Roberts and V. G. Stavros. Chem. Sci., 5 (2014) 1698 [Invited perspective article]
[21] Mapping the ultrafast dynamics of adenine onto its nucleotide and oligonucleotides by time-resolved photoelectron imaging. A. S. Chatterley, C. W. West, G. M. Roberts, V. G. Stavros and J. R. R. Verlet. J. Phys. Chem. Lett., 5 (2014) 843
[20] Relaxation dynamics of photoexcited resorcinol: internal conversion versus H atom tunneling. J. D. Young, M. Staniforth, A. S. Chatterley, G. M. Roberts, M. J. Paterson and V. G. Stavros. Phys. Chem. Chem. Phys., 16 (2014) 550 [Imaging molecular dynamics themed issue]
[19]* Timescales for adiabatic photodissociation dynamics from the A state of ammonia. A. S. Chatterley, G. M. Roberts and V. G. Stavros. J. Chem. Phys., 139 (2013) 034318
[18] Probing ultrafast dynamics in photoexcited pyrrole: timescales for 1πσ* mediated H-atom elimination. G. M. Roberts, C. A. Williams, H. Yu, A. S. Chatterley, J. D. Young, S. Ullrich and V. G. Stavros. Faraday Discuss., 163 (2013) 95
[17]* Manipulating dynamics with chemical structure: probing vibrationally-enhanced tunnelling in photoexcited catechol. A. S. Chatterley, J. D. Young, D. Townsend, J. M. Żurek, M. J. Paterson, G. M. Roberts and V. G. Stavros. Phys. Chem. Chem. Phys., 15 (2013) 6879
[16] Exploring quantum phenomena and vibrational control in σ* mediated photochemistry. G. M. Roberts, D. J. Hadden, L. T. Bergendahl, A. M. Wenge, S. J. Harris, T. N. V. Karsili, M. N. R. Ashfold, M. J. Paterson and V. G. Stavros. Chem. Sci., 4 (2013) 993
[15] Two-photon activated ligand exchange in platinum(II) complexes. Y. Zhao, G. M. Roberts, S. E. Greenough, N. J. Farrer, W. H. Powell, M. J. Paterson, V. G. Stavros and P. J. Sadler. Angew. Chem. Int. Ed., 51(2012) 11263
[14] Competing 1πσ* mediated dynamics in mequinol: O-H versus O-CH3 photodissociation pathways. D. J. Hadden, G. M. Roberts, T. N. V. Karsili, M. N. R. Ashfold and V. G. Stavros. Phys. Chem. Chem. Phys., 14 (2012) 13415
[13] Unraveling ultrafast dynamics in photoexcited aniline. G. M. Roberts, C. A. Williams, J. D. Young, S. Ullrich, M. J. Paterson and V. G. Stavros. J. Am. Chem. Soc., 134 (2012) 12578
[12] Velocity-map imaging at low extraction fields. D. A. Horke, G. M. Roberts, J. Lecointre and J. R. R. Verlet. Rev. Sci. Instrum., 83 (2012) 063101
[11] Observation of ultrafast NH3(A) state relaxation using a combination of time-resolved photoelectron and photoproduct detection. N. L. Evans, H. Yu, G. M. Roberts, V. G. Stavros and S. Ullrich. Phys. Chem. Chem. Phys., 14 (2012) 10401
[10] Direct observation of hydrogen tunneling dynamics in photoexcited phenol. G. M. Roberts, A. S. Chatterley, J. D. Young and V. G. Stavros. J. Phys. Chem. Lett., 3 (2012) 348
[9] Comparing the ultraviolet photostability of azole chromophores. G. M. Roberts, C. A. Williams, S. Ullrich, M. J. Paterson and V. G. Stavros. Chem. Sci., 3 (2012) 1192
[8] Exploring ultrafast H-atom elimination versus photofragmentation pathways in pyrazole following 200 nm excitation. C. A. Williams, G. M. Roberts, N. L. Evans, H. Yu, S. Ullrich and V. G. Stavros. J. Phys. Chem. A, 116 (2012) 2600 [Femto10: Madrid Conference on Femtochemistry special issue]
[7] Excited states in electron-transfer reaction products: ultrafast relaxation dynamics of an isolated acceptor anion. D. A. Horke, G. M. Roberts and J. R. R. Verlet. J. Phys. Chem. A, 115 (2011) 8369
[6] Time resolved velocity map imaging of H-atom elimination from photoexcited imidazole and its methyl substituted derivatives. D. J. Hadden, K. L.Wells, G. M. Roberts, L. T. Bergendahl, M. J. Paterson and V. G. Stavros. Phys. Chem. Chem. Phys., 13 (2011) 10342
[5] Time-resolved velocity map imaging of methyl elimination from photoexcited anisole. D. J. Hadden, C. A. Williams, G. M. Roberts and V. G. Stavros. Phys. Chem. Chem. Phys., 13 (2011) 4494
[4] Ultrafast relaxation dynamics observed through time-resolved photoelectron angular distributions. J. Lecointre, G. M. Roberts, D. A. Horke and J. R. R. Verlet. J. Phys. Chem. A, 114 (2010) 11216 [Klaus Müller-Dethlefs Festschrift special issue]
[3] Spectroscopy and dynamics of the 7,7,8,8-tetracyanoquinodimethane radical anion. G. M. Roberts, J. Lecointre, D. A. Horke and J. R. R. Verlet. Phys. Chem. Chem. Phys., 12 (2010) 6226
[2] Toward real-time charged-particle image reconstruction using polar onion-peeling. G. M. Roberts, J. L. Nixon, J. Lecointre, E. Wrede and J. R. R. Verlet. Rev. Sci. Instrum., 80 (2009) 503104
[1] Dynamics of H-loss in adenine via the πσ* state using a combined ns and fs laser approach. K. L. Wells, G. M. Roberts and V. G. Stavros. Chem. Phys. Lett., 446 (2007) 20
Book Chapters
Biomolecules, photostability and 1πσ* states: Linking these with femtochemistry. G. M. Roberts and V. G. Stavros in Ultrafast phenomena in molecular sciences (R. de Nalda and L. Bañares ed.), Springer series in chemical physics, vol. 107 (2014), pp 119-143
