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In our experiment, a trace amount of an organic molecule (M = 1H-phenalen-1-one, 9-fluorenone, pyridine, or acridine) was seeded into a gas mix consisting of 3% O2 with a rare gas buffer (He or Ar) and then supersonically expanded. We excited the resulting molecular beam with ultraviolet light at either 355 nm (1H-phenalen-1-one, 9-fluorenone, or acridine) or 266 nm (pyridine) and used resonance enhanced multiphoton ionization (REMPI) spectroscopy to probe for formation of O2 in the a 1Δg state, 1O2. For all systems, the REMPI spectra demonstrates that ultraviolet excitation results in formation of 1O2 and the oxygen product is confirmed to be in the ground vibrational state and with an effective rotational temperature below 80 K. We then recorded the velocity map ion image of the 1O2 product. From the ion images we determined the center-of-mass translational energy distribution, P(ET), assuming photodissociation of a bimolecular M-O2 complex. We also report results from electronic structure calculations that allow for a determination of the M-O2 ground state binding energy. We use the complex binding energy, the energy to form 1O2, and the adiabatic triplet energy for each organic molecule to determine the available energy following photodissociation. For dissociation of a bimolecular complex, this available energy may be partitioned into either center-of-mass recoil or internal degrees of freedom of the organic moiety. We use the available energy to generate a Prior distribution, which predicts statistical energy partitioning during dissociation. For low available energies, less than 0.2 eV, we find the statistical prediction is in reasonable agreement with the experimental observations. However, at higher available energies the experimental distribution is biased to lower center-of-mass kinetic energies compared with the statistical prediction, which suggests the complex undergoes vibrational predissociation.
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Increased Photostability of the Integral mRNA Vaccine Component N 1 ‐Methylpseudouridine Compared to Uridine
Abstract N1‐Methylation of pseudouridine (m1ψ) replaces uridine (Urd) in several therapeutics, including the Moderna and BioNTech‐Pfizer COVID‐19 vaccines. Importantly, however, it is currently unknown if exposure to electromagnetic radiation can affect the chemical integrity and intrinsic stability of m1ψ. In this study, the photochemistry of m1ψ is compared to that of uridine by using photoirradiation at 267 nm, steady‐state spectroscopy, and quantum‐chemical calculations. Furthermore, femtosecond transient absorption measurements are collected to delineate the electronic relaxation mechanisms for both nucleosides under physiologically relevant conditions. It is shown that m1ψ exhibits a 12‐fold longer1ππ* decay lifetime than uridine and a 5‐fold higher fluorescence yield. Notably, however, the experimental results also demonstrate that most of the excited state population in both molecules decays back to the ground state in an ultrafast time scale and that m1ψ is 6.7‐fold more photostable than Urd following irradiation at 267 nm.
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- Award ID(s):
- 1800052
- PAR ID:
- 10362194
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Chemistry – A European Journal
- Volume:
- 28
- Issue:
- 6
- ISSN:
- 0947-6539
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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