Mode-specific vibrational relaxation of photoexcited guanosine 5'-monophosphate and its acid form: a femtosecond broadband mid-IR transient absorption and theoretical study.

نویسندگان

  • Yuyuan Zhang
  • Roberto Improta
  • Bern Kohler
چکیده

UV-pump/broadband-mid-IR-probe transient absorption (TA) experiments and ab initio quantum mechanical (QM) calculations were used to investigate the photophysics in heavy water of the neutral and acid forms of guanosine 5'-monophosphate (GMP and GMPD(+), respectively). Excited GMP undergoes ultrafast internal conversion (IC) and returns to the electronic ground state in less than one picosecond with a large amount of excess vibrational energy. The spectroscopic signals are dominated by vibrational cooling - a process in which the solute dissipates vibrational energy to the solvent. For neutral GMP, cooling proceeds with a time constant of 3 ps. Following IC, at least some medium-frequency modes such as the carbonyl stretch and an in-plane ring vibration are excited, suggesting that the vibrational energy distribution is non-statistical. This is consistent with predicted structural changes upon passage through the S1/S0 conical intersection. GMPD(+) differs from GMP by a single deuteron at the N7 position, but has a dramatically longer lifetime of 200 ps. Vibrational cooling of the S1 state of GMPD(+) was monitored via several medium-frequency modes that were assigned using QM calculations. These medium-frequency modes are also vibrationally excited in a non-statistical fashion. Excitation of these modes is in line with the change in geometry at the S1 minimum of GMPD(+) predicted by QM calculations. Furthermore, these modes relax at different rates, fully consistent with QM calculations, which predict that excited vibrational states of the carbonyl stretch couple strongly to the D2O solvent and thus deactivate via intermolecular energy transfer (IET). In contrast, the ring stretch couples strongly to other ring modes of the guanine chromophore and appears to decay via intramolecular vibrational energy redistribution (IVR).

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

منابع مشابه

Coherent ultrafast torsional motion and isomerization of a biomimetic dipolar photoswitchw

Femtosecond fluorescence up-conversion, UV-Vis and IR transient absorption spectroscopy are used to study the photo-isomerization dynamics of a new type of zwitterionic photoswitch based on a N-alkylated indanylidene pyrroline Schiff base framework (ZW-NAIP). The system is biomimetic, as it mimics the photophysics of retinal, in coupling excited state charge translocation and isomerization. Whi...

متن کامل

Femtosecond UV-pump mid-IR probe spectroscopy of the ultrafast photodissociation of azide radicals from an azidoiron\(III\) complex

The ultrafast photolysis of the cation complex [(cyclam-ac)FeN3] is studied by femtosecond spectroscopy with ultraviolet excitation and mid-infrared probing. Immediately after UV absorption, the excited complex undergoes internal conversion and azide dissociation within 2 ps. The subsequent vibrational relaxation in the electronic ground state and geminate recombination of the fragments take pl...

متن کامل

Ultrafast photoprotective properties of the sunscreening agent octocrylene.

Today octocrylene is one of the most common molecules included in commercially available sunscreens. It provides broadband photoprotection for the skin from incident UV-A and UV-B radiation of the solar spectrum. In order to understand how octocrylene fulfils its role as a sunscreening agent, femtosecond pump-probe transient electronic UV-visible absorption spectroscopy is utilised to investiga...

متن کامل

Coherent ultrafast torsional motion and isomerization of a biomimetic dipolar photoswitch.

Femtosecond fluorescence up-conversion, UV-Vis and IR transient absorption spectroscopy are used to study the photo-isomerization dynamics of a new type of zwitterionic photoswitch based on a N-alkylated indanylidene pyrroline Schiff base framework (ZW-NAIP). The system is biomimetic, as it mimics the photophysics of retinal, in coupling excited state charge translocation and isomerization. Whi...

متن کامل

Ultrafast intramolecular electronic energy transfer in rigidly linked aminopyrenyl-aminobenzanthronyl dyads--a femtosecond study.

Ultrafast electronic excitation transfer (EET) followed by structural and vibrational relaxation (VER) of the acceptor have been characterised using transient absorption and transient lens techniques.

متن کامل

ذخیره در منابع من


  با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

عنوان ژورنال:
  • Physical chemistry chemical physics : PCCP

دوره 16 4  شماره 

صفحات  -

تاریخ انتشار 2014