Photoexcitation of Adenosine 5'-Triphosphate Anions in Vacuo: Probing the Influence of Charge State on the UV Photophysics of Adenine

TY - JOUR

T1 - Photoexcitation of Adenosine 5'-Triphosphate Anions in Vacuo

T2 - Probing the Influence of Charge State on the UV Photophysics of Adenine

AU - Cercola, Rosaria

AU - Matthews, Edward

AU - Dessent, Caroline E H

N1 - © 2017 American Chemical Society. This is an author-produced version of the published paper. Uploaded in accordance with the publisher’s self-archiving policy. Further copying may not be permitted; contact the publisher for details.

PY - 2017/6/8

Y1 - 2017/6/8

N2 - We report the first UV laser photodissociation spectra (4.0-5.8 eV) of gas-phase deprotonated adenosine 5'-triphosphate, diphosphate and monophosphate anions. The photodepletion spectra of these anions display strong absorption bands across the region of 4.6-5.2 eV, consistent with excitation of a primarily adenine-centered π-π* transition. The spectra appear insensitive to the charge of the species (i.e., the spectrum of [ATP-2H](2-) closely resembles that of [ATP-H](-)), while the spectral profile is affected to a greater extent by the variation of the molecular structure, i.e. the [AMP-H](-) and [ADP-H](-) photodepletion spectra display similar profiles while the [ATP-H](-) spectrum is distinctive. The photodepletion cross-section also decreases for the ATP anions compared to both the AMP and ADP anions, reflecting a high intrinsic photostability of ATP versus both AMP and ADP. A range of photofragments are produced across the 4.0-5.8 eV spectral range for all of the ATP analogues studied. These fragments are primarily associated with fragmentation on the ground-state electronic surface, indicative of a statistical decay process where ultrafast decay is followed by ergodic dissociation. However, while the photofragments observed following photoexcitation of the monoanionic species, [AMP-H](-) to [ADP-H](-) to [ATP-H](-) are entirely consistent with statistical decay, an additional group of photofragments are observed for the dianionic species, [ADP-2H](2-) and [ATP-2H](2-), that we associate with electron detachment, and subsequent fragmentation of the resulting electron-detached photofragment. TDDFT calculations are presented to support the interpretation of the experimental data, and confirm that the electronic structure of the adenine moiety is relatively unperturbed by varying the overall charge.

AB - We report the first UV laser photodissociation spectra (4.0-5.8 eV) of gas-phase deprotonated adenosine 5'-triphosphate, diphosphate and monophosphate anions. The photodepletion spectra of these anions display strong absorption bands across the region of 4.6-5.2 eV, consistent with excitation of a primarily adenine-centered π-π* transition. The spectra appear insensitive to the charge of the species (i.e., the spectrum of [ATP-2H](2-) closely resembles that of [ATP-H](-)), while the spectral profile is affected to a greater extent by the variation of the molecular structure, i.e. the [AMP-H](-) and [ADP-H](-) photodepletion spectra display similar profiles while the [ATP-H](-) spectrum is distinctive. The photodepletion cross-section also decreases for the ATP anions compared to both the AMP and ADP anions, reflecting a high intrinsic photostability of ATP versus both AMP and ADP. A range of photofragments are produced across the 4.0-5.8 eV spectral range for all of the ATP analogues studied. These fragments are primarily associated with fragmentation on the ground-state electronic surface, indicative of a statistical decay process where ultrafast decay is followed by ergodic dissociation. However, while the photofragments observed following photoexcitation of the monoanionic species, [AMP-H](-) to [ADP-H](-) to [ATP-H](-) are entirely consistent with statistical decay, an additional group of photofragments are observed for the dianionic species, [ADP-2H](2-) and [ATP-2H](2-), that we associate with electron detachment, and subsequent fragmentation of the resulting electron-detached photofragment. TDDFT calculations are presented to support the interpretation of the experimental data, and confirm that the electronic structure of the adenine moiety is relatively unperturbed by varying the overall charge.

KW - Journal Article

UR - http://www.scopus.com/inward/record.url?scp=85021405725&partnerID=8YFLogxK

U2 - 10.1021/acs.jpcb.7b03435

DO - 10.1021/acs.jpcb.7b03435

M3 - Article

C2 - 28521097

SN - 1520-6106

VL - 121

SP - 5553

EP - 5561

JO - Journal of Physical Chemistry B

JF - Journal of Physical Chemistry B

IS - 22

ER -