TY - JOUR
T1 - Photodissociative decay pathways of the flavin mononucleotide anion and its complexes with tryptophan and glutamic acid
AU - Uleanya, Kelechi
AU - Dessent, Caroline Elizabeth Helen
AU - Anstoter, Cate Sara
N1 - © the Owner Societies 2023
PY - 2023/11/3
Y1 - 2023/11/3
N2 - Flavin mononucleotide (FMN) is a highly versatile biological chromophore involved in a range of biochemical pathways including blue-light sensing proteins and the control of circadian rhythms. Questions exist about the effect of local amino acids on the electronic properties and photophysics of the chromophore. Using gas-phase anion laser photodissociation spectroscopy, we have measured the intrinsic electronic spectroscopy (3.1–5.7 eV) and accompanying photodissociative decay pathways of the native deprotonated form of FMN, i.e. [FMN-H]− complexed with the amino acids tryptophan (TRP) and glutamic acid (GLU), i.e. [FMN-H]−·TRP and [FMN-H]−·GLU, to investigate the extent to which these amino acids perturb the electronic properties and photodynamics of the [FMN-H]− chromophore. The overall photodepletion profiles of [FMN-H]−·TRP and [FMN-H]−·GLU are similar to that of the monomer, revealing that amino acid complexation occurs without significant spectral shifting of the [FMN-H]− electronic excitations over this region. Both [FMN-H]−·TRP and [FMN-H]−·GLU are observed to decay by non-statistical photodecay pathways, although the behaviour of [FMN-H]−·TRP is closer to statistical fragmentation. Long-lived FMN excited states (triplet) are therefore relatively quenched when TRP binds to [FMN-H]−. Importantly, we find that [FMN-H]−, [FMN-H]−·TRP and [FMN-H]−·GLU all decay predominantly via electron detachment following photoexcitation of the flavin chromophore, with amino acid complexation appearing not to inhibit this decay channel. The strong propensity for electron detachment is attributed to excited-state proton transfer within FMN, with proton transfer from a ribose alcohol to the phosphate preceding electron detachment.
AB - Flavin mononucleotide (FMN) is a highly versatile biological chromophore involved in a range of biochemical pathways including blue-light sensing proteins and the control of circadian rhythms. Questions exist about the effect of local amino acids on the electronic properties and photophysics of the chromophore. Using gas-phase anion laser photodissociation spectroscopy, we have measured the intrinsic electronic spectroscopy (3.1–5.7 eV) and accompanying photodissociative decay pathways of the native deprotonated form of FMN, i.e. [FMN-H]− complexed with the amino acids tryptophan (TRP) and glutamic acid (GLU), i.e. [FMN-H]−·TRP and [FMN-H]−·GLU, to investigate the extent to which these amino acids perturb the electronic properties and photodynamics of the [FMN-H]− chromophore. The overall photodepletion profiles of [FMN-H]−·TRP and [FMN-H]−·GLU are similar to that of the monomer, revealing that amino acid complexation occurs without significant spectral shifting of the [FMN-H]− electronic excitations over this region. Both [FMN-H]−·TRP and [FMN-H]−·GLU are observed to decay by non-statistical photodecay pathways, although the behaviour of [FMN-H]−·TRP is closer to statistical fragmentation. Long-lived FMN excited states (triplet) are therefore relatively quenched when TRP binds to [FMN-H]−. Importantly, we find that [FMN-H]−, [FMN-H]−·TRP and [FMN-H]−·GLU all decay predominantly via electron detachment following photoexcitation of the flavin chromophore, with amino acid complexation appearing not to inhibit this decay channel. The strong propensity for electron detachment is attributed to excited-state proton transfer within FMN, with proton transfer from a ribose alcohol to the phosphate preceding electron detachment.
U2 - 10.1039/D3CP04359B
DO - 10.1039/D3CP04359B
M3 - Article
SN - 1463-9076
VL - 23
SP - 30697
EP - 30707
JO - Physical chemistry chemical physics : PCCP
JF - Physical chemistry chemical physics : PCCP
ER -