Time-resolved photoelectron imaging of the isolated deprotonated nucleotides

Abstract

Publisher's copyright statement:Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Using time-resolved photoelectron spectroscopy, the excited state dynamics of gas-phase mass-selected nucleotide anions have been monitored following UV excitation at 4.66 eV. The spectra reveal that the dynamics of the 2'-deoxyguanosine 5'-monophosphate anion (dGMP -) are very similar to those of the adenosine nucleotide (dAMP -) and insensitive to a solvation environment. Comparison of our results with other literature suggest s that nucleotides of the two purine bases share a common relaxation pathway, whereby the initially populated 1 ππ* states relax to the ground electronic state without involvement of any other intermediary electronic states. In the analogous pyrimidine nucleotides of thymine and cytosine, dTMP -and dCMP -, no such unified mechanism is observed. Photoexcited dTMP -behaves much like the isolated nucleobase thymine, exhibiting rapid relaxation to the ground electronic state, although with a minor long-lived channel. On the other hand, isolated dCMP -is longer lived than its cytosine nucleobase, and hence it appears that the presence of the sugar and phosphate in the nucleotide arrangement leads to a modification of the available relaxation pathways. Nucleotides are the basic monomer building blocks of DNA and our results present important new benchmark data to develop an understanding of the molecular mechanism by which photodamage can be mediated when DNA is exposed to UV light.

Observing and Understanding the Ultrafast Photochemistry in Small Molecules: Applications to Sunscreens

“…It persists out to ∆t ∼100 ps and is attributed to stimulated emission from a 2 1 ππ * state, given the likely excited states involved based on similar molecular systems 27;53 . Quantitatively, the dynamical processes which occur with the TEA spectra are modelled using global nonlinear regression analysis 45 . With reference to Section 2.2 and Eq.…”

Assessment of the Potential Energy Hypersurfaces in Thymine within Multiconfigurational Theory: CASSCF vs. CASPT2

“…Several components in different time ranges have been detected over the years in time resolved experiments on DNA nucleobases: in the sub-ps regime, a bi-exponential decay was characterized for nucleobases, nucleosides or nucleotides [3,24,60,62], being mainly ascribed to ultrafast reactions along the initially accessed 1 (ππ*) PEH, whereas a single component has also been observed in the few-ps timescale and being ascribed to dark nπ* states [55], and a longer component closer to the ns regime has been attributed to the eventual involvement of triplet states [55,56]. Theoretically, most studies agree in the initial involvement of the 1 (ππ*) state for the sub-ps channels, having characterized a series of key structures in its PEH that rationalize its concrete role.…”

“…These not only provide the PEHs for mechanistic purposes, but can also yield excited state absorptions [49,50], cationic energies [41], and other related observables with direct experimental counterparts [51,52]. Experimentally, several techniques have been employed to study the photoinduced phenomena of DNA nucleobases, ranging from pump-probe [4,28,[53][54][55], time-resolved infrared [56][57][58][59], photoelectron [17,41,60,61] and recently even Auger spectroscopy [16]. This has allowed postulating different theoretical models to explain the photochemical decay paths of the canonical nucleobases and simulate a range of experimental spectroscopic observables, providing a molecular counterpart.…”

Time-Resolved Photodetachment Anisotropy: Gas-Phase Rotational and Vibrational Dynamics of the Fluorescein Anion

“…44,45 Simply measuring the total ion yield with two polarizations would eliminate such ambiguities. In cases where population dynamics are occurring on very different timescales as rotational dephasing, as is the case for nucleotides and oligonucleotides 46,47 for example, such complications are less important.…”