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Seaton RA, Ritchie ND, Robb F, Stewart L, White B, Vallance C. From 'OPAT' to 'COpAT': implications of the OVIVA study for ambulatory management of bone and joint infection. J Antimicrob Chemother 2020; 74:2119-2121. [PMID: 30989175 DOI: 10.1093/jac/dkz122] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Bone and joint infection contributes significantly to clinical activity within outpatient parenteral antimicrobial therapy (OPAT) services. The OVIVA (oral versus intravenous antibiotics for bone and joint infection) randomized study has challenged the practice of prolonged intravenous therapy, because non-inferiority of oral antibiotic therapy was demonstrated, thereby implying that early transition to oral therapy is an appropriate alternative to prolonged intravenous therapy. We examine the caveats to the study and discuss the implications for OPAT practice, highlighting the importance of careful oral antibiotic selection with attention to bioavailability, bone penetration, drug interactions, compliance and toxicity monitoring. We emphasize that ambulatory antibiotic therapy (whether intravenous or oral) in this patient group requires expert multidisciplinary management, monitoring and follow-up, and ideally should be undertaken within existing OPAT or, more accurately, complex outpatient antibiotic therapy (COpAT) services.
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Köckert H, Heathcote D, Lee JWL, Vallance C. Covariance-map imaging study into the fragmentation dynamics of multiply charged CF3I formed in electron-molecule collisions. Mol Phys 2020. [DOI: 10.1080/00268976.2020.1811909] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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De Maria GL, Lee R, Alkhalil M, Borlotti A, Kotronias R, Langrish J, Lucking A, Dawkins S, Choudhury RP, Kharbanda R, Banning AP, Vallance C, Channon KM. Reflectance spectral analysis for novel characterization and clinical assessment of aspirated coronary thrombi in patients with ST elevation myocardial infarction. Physiol Meas 2020; 41:045001. [PMID: 32197256 DOI: 10.1088/1361-6579/ab81de] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
OBJECTIVE The visual appearance of coronary thrombi may be clinically informative in ST elevation myocardial infarction (STEMI) patients undergoing primary percutaneous coronary intervention (pPCI). However, subjective assessment is poorly reproducible and cannot provide an objective basis for treatment decisions or patient stratification. We have assessed the feasibility of a novel reflectance spectroscopy technique to systematically characterize coronary artery thrombi retrieved by aspiration during pPCI in patients with STEMI, and the clinical utility for predicting distal microvascular obstruction. APPROACH Patients with STEMI treated with pPCI and thrombus aspiration (n = 288) were recruited from the Oxford Acute Myocardial Infarction (OxAMI) Study. Of these, 158 patients underwent cardiac magnetic resonance imaging within 48 h for assessment of microvascular obstruction (MVO). Coronary thrombi were imaged by reflectance spectroscopy across wavelengths 500-800 nm. MAIN RESULTS Spectral data were analysed using function fitting and multivariate models. The coefficient 'c red' determined from the fitting procedure correlated with the visually-assessed colour of thrombi ('red' or 'white') and with MVO. When applied to a reduced data set, consisting of spectra from 20 patients with the largest MVO and from 20 propensity-score-matched patients with no MVO, three multivariate analysis methods were able to discriminate spectra of thrombi from patients without MVO and with the largest MVO. SIGNIFICANCE Reflectance spectral analysis of coronary thrombus provides new insights into the pathology of STEMI, with potential clinical implications for emergency patient care. Further studies are warranted for validation as a point-of-care stratification tool in predicting the degree of microvascular injury and clinical outcomes in STEMI.
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Livermore LJ, Isabelle M, Bell IM, Scott C, Walsby-Tickle J, Gannon J, Plaha P, Vallance C, Ansorge O. Rapid intraoperative molecular genetic classification of gliomas using Raman spectroscopy. Neurooncol Adv 2019; 1:vdz008. [PMID: 31608327 PMCID: PMC6777649 DOI: 10.1093/noajnl/vdz008] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
BACKGROUND The molecular genetic classification of gliomas, particularly the identification of isocitrate dehydrogenase (IDH) mutations, is critical for clinical and surgical decision-making. Raman spectroscopy probes the unique molecular vibrations of a sample to accurately characterize its molecular composition. No sample processing is required allowing for rapid analysis of tissue. The aim of this study was to evaluate the ability of Raman spectroscopy to rapidly identify the common molecular genetic subtypes of diffuse glioma in the neurosurgical setting using fresh biopsy tissue. In addition, classification models were built using cryosections, formalin-fixed paraffin-embedded (FFPE) sections and LN-18 (IDH-mutated and wild-type parental cell) glioma cell lines. METHODS Fresh tissue, straight from neurosurgical theatres, underwent Raman analysis and classification into astrocytoma, IDH-wild-type; astrocytoma, IDH-mutant; or oligodendroglioma. The genetic subtype was confirmed on a parallel section using immunohistochemistry and targeted genetic sequencing. RESULTS Fresh tissue samples from 62 patients were collected (36 astrocytoma, IDH-wild-type; 21 astrocytoma, IDH-mutated; 5 oligodendroglioma). A principal component analysis fed linear discriminant analysis classification model demonstrated 79%-94% sensitivity and 90%-100% specificity for predicting the 3 glioma genetic subtypes. For the prediction of IDH mutation alone, the model gave 91% sensitivity and 95% specificity. Seventy-nine cryosections, 120 FFPE samples, and LN18 cells were also successfully classified. Meantime for Raman data collection was 9.5 min in the fresh tissue samples, with the process from intraoperative biopsy to genetic classification taking under 15 min. CONCLUSION These data demonstrate that Raman spectroscopy can be used for the rapid, intraoperative, classification of gliomas into common genetic subtypes.
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Zhou W, Wilkinson L, Lee JWL, Heathcote D, Vallance C. Total electron ionization cross-sections for molecules of astrochemical interest. Mol Phys 2019. [DOI: 10.1080/00268976.2019.1583389] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Li HK, Rombach I, Zambellas R, Walker AS, McNally MA, Atkins BL, Lipsky BA, Hughes HC, Bose D, Kümin M, Scarborough C, Matthews PC, Brent AJ, Lomas J, Gundle R, Rogers M, Taylor A, Angus B, Byren I, Berendt AR, Warren S, Fitzgerald FE, Mack DJF, Hopkins S, Folb J, Reynolds HE, Moore E, Marshall J, Jenkins N, Moran CE, Woodhouse AF, Stafford S, Seaton RA, Vallance C, Hemsley CJ, Bisnauthsing K, Sandoe JAT, Aggarwal I, Ellis SC, Bunn DJ, Sutherland RK, Barlow G, Cooper C, Geue C, McMeekin N, Briggs AH, Sendi P, Khatamzas E, Wangrangsimakul T, Wong THN, Barrett LK, Alvand A, Old CF, Bostock J, Paul J, Cooke G, Thwaites GE, Bejon P, Scarborough M. Oral versus Intravenous Antibiotics for Bone and Joint Infection. N Engl J Med 2019; 380:425-436. [PMID: 30699315 PMCID: PMC6522347 DOI: 10.1056/nejmoa1710926] [Citation(s) in RCA: 470] [Impact Index Per Article: 94.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
BACKGROUND The management of complex orthopedic infections usually includes a prolonged course of intravenous antibiotic agents. We investigated whether oral antibiotic therapy is noninferior to intravenous antibiotic therapy for this indication. METHODS We enrolled adults who were being treated for bone or joint infection at 26 U.K. centers. Within 7 days after surgery (or, if the infection was being managed without surgery, within 7 days after the start of antibiotic treatment), participants were randomly assigned to receive either intravenous or oral antibiotics to complete the first 6 weeks of therapy. Follow-on oral antibiotics were permitted in both groups. The primary end point was definitive treatment failure within 1 year after randomization. In the analysis of the risk of the primary end point, the noninferiority margin was 7.5 percentage points. RESULTS Among the 1054 participants (527 in each group), end-point data were available for 1015 (96.3%). Treatment failure occurred in 74 of 506 participants (14.6%) in the intravenous group and 67 of 509 participants (13.2%) in the oral group. Missing end-point data (39 participants, 3.7%) were imputed. The intention-to-treat analysis showed a difference in the risk of definitive treatment failure (oral group vs. intravenous group) of -1.4 percentage points (90% confidence interval [CI], -4.9 to 2.2; 95% CI, -5.6 to 2.9), indicating noninferiority. Complete-case, per-protocol, and sensitivity analyses supported this result. The between-group difference in the incidence of serious adverse events was not significant (146 of 527 participants [27.7%] in the intravenous group and 138 of 527 [26.2%] in the oral group; P=0.58). Catheter complications, analyzed as a secondary end point, were more common in the intravenous group (9.4% vs. 1.0%). CONCLUSIONS Oral antibiotic therapy was noninferior to intravenous antibiotic therapy when used during the first 6 weeks for complex orthopedic infection, as assessed by treatment failure at 1 year. (Funded by the National Institute for Health Research; OVIVA Current Controlled Trials number, ISRCTN91566927 .).
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Vallance C. Multi-mass velocity-map imaging studies of photoinduced and electron-induced chemistry. Chem Commun (Camb) 2019; 55:6336-6352. [PMID: 31099379 DOI: 10.1039/c9cc02426c] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Multi-mass velocity-map imaging (VMI) is becoming established as a promising method for probing the dynamics of a variety of gas-phase chemical processes. We provide an overview of velocity-map imaging and multi-mass velocity-map imaging techniques, highlighting examples in which these approaches have been used to provide mechanistic insights into a range of photoinduced and electron-induced chemical processes. Multi-mass detection capabilities have also led to the development of two new tools for the chemical dynamics toolbox, in the form of Coulomb-explosion imaging and covariance-map imaging. These allow details of molecular structure to be followed in real time over the course of a chemical reaction, offering the tantalising prospect of recording real-time 'molecular movies' of chemical dynamics. As these new methods become established within the reaction dynamics community, they promise new mechanistic insights into chemistry relevant to fields ranging from atmospheric chemistry and astrochemistry through to synthetic organic photochemistry and biology.
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Köckert H, Heathcote D, Lee JWL, Zhou W, Richardson V, Vallance C. C–I and C–F bond-breaking dynamics in the dissociative electron ionization of CF3I. Phys Chem Chem Phys 2019; 21:14296-14305. [DOI: 10.1039/c8cp06682e] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We present a comprehensive experimental study into the dissociative electron ionization dynamics of CF3I at energies ranging from 20 to 100 eV.
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Allum F, Burt M, Amini K, Boll R, Köckert H, Olshin PK, Bari S, Bomme C, Brauße F, Cunha de Miranda B, Düsterer S, Erk B, Géléoc M, Geneaux R, Gentleman AS, Goldsztejn G, Guillemin R, Holland DMP, Ismail I, Johnsson P, Journel L, Küpper J, Lahl J, Lee JWL, Maclot S, Mackenzie SR, Manschwetus B, Mereshchenko AS, Mason R, Palaudoux J, Piancastelli MN, Penent F, Rompotis D, Rouzée A, Ruchon T, Rudenko A, Savelyev E, Simon M, Schirmel N, Stapelfeldt H, Techert S, Travnikova O, Trippel S, Underwood JG, Vallance C, Wiese J, Ziaee F, Brouard M, Marchenko T, Rolles D. Coulomb explosion imaging of CH3I and CH2ClI photodissociation dynamics. J Chem Phys 2018; 149:204313. [DOI: 10.1063/1.5041381] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Livermore LJ, Isabelle M, Bell I, Plaha P, Vallance C, Ansorge O. RAPID GENETIC CLASSIFICATION OF GLIOMAS USING RAMAN SPECTROSCOPY. Neuro Oncol 2018. [DOI: 10.1093/neuonc/noy129.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Lipciuc ML, Gardiner SH, Karsili TNV, Lee JWL, Heathcote D, Ashfold MNR, Vallance C. Photofragmentation dynamics of N,N-dimethylformamide following excitation at 193 nm. J Chem Phys 2018; 147:013941. [PMID: 28688414 DOI: 10.1063/1.4983704] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
N,N-dimethylformamide, HCON(CH3)2, is a useful model compound for investigating the peptide bond photofragmentation dynamics. We report data from a comprehensive experimental and theoretical study into the photofragmentation dynamics of N,N-dimethylformamide in the gas phase at 193 nm. Through a combination of velocity-map imaging and hydrogen atom Rydberg tagging photofragment translational spectroscopy we have identified two primary fragmentation channels, namely, fission of the N-CO "peptide" bond and N-CH3 bond fission leading to the loss of CH3. The possible fragmentation channels leading to the observed products are rationalised with recourse to CASPT2 calculations of the ground and first few excited-state potential energy curves along the relevant dissociation coordinates, and the results are compared with the data from previous experimental and theoretical studies on the same system.
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Burt M, Amini K, Lee JWL, Christiansen L, Johansen RR, Kobayashi Y, Pickering JD, Vallance C, Brouard M, Stapelfeldt H. Communication: Gas-phase structural isomer identification by Coulomb explosion of aligned molecules. J Chem Phys 2018. [DOI: 10.1063/1.5023441] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Amini K, Savelyev E, Brauße F, Berrah N, Bomme C, Brouard M, Burt M, Christensen L, Düsterer S, Erk B, Höppner H, Kierspel T, Krecinic F, Lauer A, Lee JWL, Müller M, Müller E, Mullins T, Redlin H, Schirmel N, Thøgersen J, Techert S, Toleikis S, Treusch R, Trippel S, Ulmer A, Vallance C, Wiese J, Johnsson P, Küpper J, Rudenko A, Rouzée A, Stapelfeldt H, Rolles D, Boll R. Photodissociation of aligned CH 3I and C 6H 3F 2I molecules probed with time-resolved Coulomb explosion imaging by site-selective extreme ultraviolet ionization. STRUCTURAL DYNAMICS (MELVILLE, N.Y.) 2018; 5:014301. [PMID: 29430482 PMCID: PMC5785297 DOI: 10.1063/1.4998648] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Accepted: 11/09/2017] [Indexed: 06/08/2023]
Abstract
We explore time-resolved Coulomb explosion induced by intense, extreme ultraviolet (XUV) femtosecond pulses from a free-electron laser as a method to image photo-induced molecular dynamics in two molecules, iodomethane and 2,6-difluoroiodobenzene. At an excitation wavelength of 267 nm, the dominant reaction pathway in both molecules is neutral dissociation via cleavage of the carbon-iodine bond. This allows investigating the influence of the molecular environment on the absorption of an intense, femtosecond XUV pulse and the subsequent Coulomb explosion process. We find that the XUV probe pulse induces local inner-shell ionization of atomic iodine in dissociating iodomethane, in contrast to non-selective ionization of all photofragments in difluoroiodobenzene. The results reveal evidence of electron transfer from methyl and phenyl moieties to a multiply charged iodine ion. In addition, indications for ultrafast charge rearrangement on the phenyl radical are found, suggesting that time-resolved Coulomb explosion imaging is sensitive to the localization of charge in extended molecules.
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Amini K, Boll R, Lauer A, Burt M, Lee JWL, Christensen L, Brauβe F, Mullins T, Savelyev E, Ablikim U, Berrah N, Bomme C, Düsterer S, Erk B, Höppner H, Johnsson P, Kierspel T, Krecinic F, Küpper J, Müller M, Müller E, Redlin H, Rouzée A, Schirmel N, Thøgersen J, Techert S, Toleikis S, Treusch R, Trippel S, Ulmer A, Wiese J, Vallance C, Rudenko A, Stapelfeldt H, Brouard M, Rolles D. Alignment, orientation, and Coulomb explosion of difluoroiodobenzene studied with the pixel imaging mass spectrometry (PImMS) camera. J Chem Phys 2017; 147:013933. [DOI: 10.1063/1.4982220] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Forbes R, Makhija V, Veyrinas K, Stolow A, Lee JWL, Burt M, Brouard M, Vallance C, Wilkinson I, Lausten R, Hockett P. Time-resolved multi-mass ion imaging: Femtosecond UV-VUV pump-probe spectroscopy with the PImMS camera. J Chem Phys 2017; 147:013911. [DOI: 10.1063/1.4978923] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Ingle RA, Hansen CS, Elsdon E, Bain M, King SJ, Lee JWL, Brouard M, Vallance C, Turchetta R, Ashfold MNR. Ultraviolet photochemistry of 2-bromothiophene explored using universal ionization detection and multi-mass velocity-map imaging with a PImMS2 sensor. J Chem Phys 2017; 147:013914. [DOI: 10.1063/1.4979559] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Trichet AAP, Dolan PR, James D, Hughes GM, Vallance C, Smith JM. Nanoparticle Trapping and Characterization Using Open Microcavities. NANO LETTERS 2016; 16:6172-6177. [PMID: 27652604 DOI: 10.1021/acs.nanolett.6b02433] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Characterization and trapping of nanoparticles in solution is of great importance for lab-on-a-chip applications in biomedical, environmental, and materials sciences. Devices are now starting to emerge allowing such manipulations and investigations in real-time. Better insights into the interaction between the nanoparticle and the optical trap is therefore necessary in order to move forward in this field. In this work, we present a new kind of nanotweezers based on open microcavities. We show that by monitoring the cavity mode wavelength shift as the particle diffuses through the cavity, it is possible to establish both the nanoparticle polarizability and its coefficient of friction. Additionally, our experiment provides a deep insight in the interaction between the nanoparticle and the cavity mode. The technique has built-in calibration of the trap strength and spring constant, making it attractive for practical applications. This work illustrates the potential of such optical microcavities for future developments in nanoparticle sensors and lab-on-a-chip devices.
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Livermore LJ, Lau K, Scott C, Larkin S, Plaha P, Vallance C, Ansorge O. P08.50 Raman spectroscopy for the identification of isocitrate dehydrogenase (IDH) mutated glioblastomas. Neuro Oncol 2016. [DOI: 10.1093/neuonc/now188.183] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Vallance C, Trichet AAP, James D, Dolan PR, Smith JM. Open-access microcavities for chemical sensing. NANOTECHNOLOGY 2016; 27:274003. [PMID: 27242174 DOI: 10.1088/0957-4484/27/27/274003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The recent development of open-access optical microcavities opens up a number of intriguing possibilities in the realm of chemical sensing. We provide an overview of the different possible sensing modalities, with examples of refractive index sensing, optical absorption measurements, and optical tracking and trapping of nanoparticles. The extremely small mode volumes within an optical microcavity allow very small numbers of molecules to be probed: our current best detection limits for refractive index and absorption sensing are around 10(5) and 10(2) molecules, respectively, with scope for further improvements in the future.
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Pandit S, Preston TJ, King SJ, Vallance C, Orr-Ewing AJ. Evidence for concerted ring opening and C–Br bond breaking in UV-excited bromocyclopropane. J Chem Phys 2016; 144:244312. [DOI: 10.1063/1.4954373] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
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Amini K, Blake S, Brouard M, Burt MB, Halford E, Lauer A, Slater CS, Lee JWL, Vallance C. Three-dimensional imaging of carbonyl sulfide and ethyl iodide photodissociation using the pixel imaging mass spectrometry camera. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2015; 86:103113. [PMID: 26520946 DOI: 10.1063/1.4934544] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The Pixel Imaging Mass Spectrometry (PImMS) camera is used in proof-of-principle three-dimensional imaging experiments on the photodissociation of carbonyl sulfide and ethyl iodide at wavelengths around 230 nm and 245 nm, respectively. Coupling the PImMS camera with DC-sliced velocity-map imaging allows the complete three-dimensional Newton sphere of photofragment ions to be recorded on each laser pump-probe cycle with a timing precision of 12.5 ns, yielding velocity resolutions along the time-of-flight axis of around 6%-9% in the applications presented.
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Gardiner SH, Lipciuc ML, Vallance C. Gas-Phase Retro-Diels–Alder Reactions of Cyclohexene, 1-Methylcyclohexene, and 4-Methylcyclohexene following Photoexcitation at 193 nm: A Velocity-Map Imaging Study. J Phys Chem A 2015; 119:12218-23. [DOI: 10.1021/acs.jpca.5b06185] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Bull JN, Lee JWL, Vallance C. Absolute electron total ionization cross-sections: molecular analogues of DNA and RNA nucleobase and sugar constituents. Phys Chem Chem Phys 2015; 16:10743-52. [PMID: 24756123 DOI: 10.1039/c4cp00490f] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Accurate ionization cross-sections for DNA and RNA constituents in the condensed or aqueous phase are important parameters for models simulating radiation damage to genetic material in living cells. In this work, absolute gas-phase electron total ionization cross-sections (TICSs) have been measured for a series of six aromatic and eight non-aromatic cyclic species that can be considered as prototype functional group analogues for the nucleobases and sugar backbone constituents of DNA and RNA. TICSs for water, hexane, and ethylacetamide (a peptide bond analogue) are also reported. The experimental apparatus utilizes a cylindrical ion collector that surrounds the ionization region, providing essentially unit detection efficiency. Two theoretical models, the polarizability-correlation method and binary-encounter Bethe theory, are able to reproduce the measured maximum TICS well for all species studied. An empirical energy-dependent correction is found to yield improvement in the agreement between experimental energy-dependent cross sections and the predictions of the BEB model. Having characterised and optimised the performance of both models, they are then used to predict TICSs for gas-phase DNA and RNA nucleobases and sugars. Direct experimental determinations of TICSs for these species are difficult because of their low volatility, which makes it difficult to prepare suitable gas-phase samples for measurement.
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