TY - JOUR

T1 - Photophysics of 5,6,7,8-tetrahydrobiopterin on a femtosecond timescale

AU - Кубенко, Варвара Георгиевна

AU - Помогаев, Владимир Анатольевич

AU - Буглак, Андрей Андреевич

AU - Кононов, Алексей Игоревич

PY - 2025/4/1

Y1 - 2025/4/1

N2 - Pterins are naturally occurring compounds widespread in living organisms. 5,6,7,8-Tetrahydrobiopterin (H4Bip) is a cofactor of several key enzymes, including NO-synthases and phenylalanine hydroxylase, whereas tetrahydrocyanopterin is a photoreceptor molecule in cyanobacteria. In this regard, tetrahydropterins (H4pterins) photochemistry and photophysics have been attracting our attention. H4pterins photodegrade in presence of molecular oxygen yielding dihydropterins (H2pterins) and oxidized pterins. Meanwhile, the excited states dynamics of H4pterins on a femto- and picosecond time-scale remains unclear. To shed light on this area, we perform time-resolved spectroscopy of H4Bip using fluorescence up-conversion as well as transient absorption spectroscopy techniques along with TD-DFT non-adiabatic molecular dynamics. We show that the lowest H4Bip exited state has a lifetime of ca. 200 fs. Using the BHandHLYP functional and multireference spin-flip (MRSF) method we demonstrate that starting from the S4 state, H4Bip passes to the S1 state within 50 fs, and after 200 fs a conical intersection with the ground S0 state is achieved. As a whole, the excited state behavior of H4Bip is similar to DNA nucleobases, in particular guanine. These findings allow us to make some speculations about the biochemical role of H4pterins photophysics.

AB - Pterins are naturally occurring compounds widespread in living organisms. 5,6,7,8-Tetrahydrobiopterin (H4Bip) is a cofactor of several key enzymes, including NO-synthases and phenylalanine hydroxylase, whereas tetrahydrocyanopterin is a photoreceptor molecule in cyanobacteria. In this regard, tetrahydropterins (H4pterins) photochemistry and photophysics have been attracting our attention. H4pterins photodegrade in presence of molecular oxygen yielding dihydropterins (H2pterins) and oxidized pterins. Meanwhile, the excited states dynamics of H4pterins on a femto- and picosecond time-scale remains unclear. To shed light on this area, we perform time-resolved spectroscopy of H4Bip using fluorescence up-conversion as well as transient absorption spectroscopy techniques along with TD-DFT non-adiabatic molecular dynamics. We show that the lowest H4Bip exited state has a lifetime of ca. 200 fs. Using the BHandHLYP functional and multireference spin-flip (MRSF) method we demonstrate that starting from the S4 state, H4Bip passes to the S1 state within 50 fs, and after 200 fs a conical intersection with the ground S0 state is achieved. As a whole, the excited state behavior of H4Bip is similar to DNA nucleobases, in particular guanine. These findings allow us to make some speculations about the biochemical role of H4pterins photophysics.

KW - DFT

KW - Fluorescence upconversion

KW - Multireference spin-flip (MRSF)

KW - Pterins

KW - Tetrahydrobiopterin

UR - https://www.mendeley.com/catalogue/d7142f9a-4ad9-3798-bdb7-3a9ae8778c3f/

U2 - 10.1016/j.jphotobiol.2025.113134

DO - 10.1016/j.jphotobiol.2025.113134

M3 - Article

VL - 265

JO - Journal of Photochemistry and Photobiology B: Biology

JF - Journal of Photochemistry and Photobiology B: Biology

SN - 1011-1344

M1 - 113134

ER -