Synthetic analogues of chromophores of green fluorescent protein were synthesised. The chromophore, which is highly fluorescent in the protein, is nearly non-fluorescent in solution. The spectral properties of the. model chromophores (absorption coefficients, oscillator strengths and effect of pH), were compared with those of the corresponding proteins. The measurements compared well with the results of theoretical calculations. Some important differences between chromophore and protein spectra were noted. The effects of solvent polarity on absorption and emission spectra were studied and analysed using the rc* and the reaction field factor measures of solvent effects. The spectral shifts were small and more dependent on hydrogen bonding interactions than solvent polarity. The low temperature excitation and emission spectra were recorded and compared to room temperature spectra. The effect of excitation wavelength on the emission spectra was investigated at low temperature and revealed an edge excitation red shift. The spectral properties of the model chromophores were investigated as a function of temperature. The fluorescence increased dramatically as the temperature decreased, even into the supercooled liquid and glass phases. This suggests that the mechanism of radiationless decay is not strongly coupled to solvent viscosity, but may be thermally activated. An isoviscosity analysis to separate these two mechanisms gave inconclusive results. The ultrafast polarisation spectroscopy of the model chromophores was then investigated as a function of protonation state, viscosity and temperature. The ground state recovery time has two components. An ultrafast recovery time of <5ps is assigned to internal conversion followed by vibrational relaxation. A slower time (>50ps) was assigned to rotational relaxation. A second isoviscosity analysis suggested that the mechanism of radiationless decay above room temperature was nearly barrierless, and only weakly coupled to viscosity. These data are most consistent with internal conversion due to cooperative intramolecular rotation of the chromophore.

The photophysics of highly electronically excited states of a set of d0 and d10 metallated tetrapyrroles, which have different peripheral substituents and central metal atoms, macrocycle substitution patterns and macrocycle conformations, have been investigated both theoretically and experimentally. Theoretically, the energies of ground state molecular orbitals and the energies and rank in energy of the excited states have been calculated using density functional theory and time-dependent density functional theory methods. Experimentally, the steady-state absorption and fluorescence spectra have been measured. Temporal fluorescence profiles have been measured using a time correlated single photon counting system for the S1 state and a fluorescence upconversion system for the S2 state.<p> The decay mechanisms of highly electronically excited states are governed by the nonradiative S2 S1 internal conversion. The possible existence of any excited state (such as S2' or dark state) lying close to the S2 state and its participation in the nonradiative decay processes of the S2 state has been discussed. The ultrafast nonradiative decay rates of the S2 S1 internal conversion were interpreted on the basis of the energy gap law of radiationless transition theory. For magnesium tetraphenylporphyrin (MgTPP), the radiationless rates (knr)of its S2 state follows the prediction of the energy gap law for the weak coupling statistical limit case. However, the S2 S1 electronic coupling energies of the other metalloporphyrins investigated fall within the inermediate to strong coupling range. The difference of knr relative to the weak coupling limit can be rationalized by the different magnitudes of electronic coupling energies. The magnitude of electronic coupling energies is the major factor in determining the radiationless depopulation rate constants of the S2 states in metallated tetrapyrroles which have S2 S1 electronic coupling energies exceeding the weak coupling limit. In some cases, such as ZnOEP, the magnitude of Frack-Condon factor has only minor effect.<p> The photophysics of Soret-excited metallated corroles have also been investigated in this study. Primary work has shown that two metallated corroles examined have similar S2 S1 interstate electronic coupling energies to that of CdTPP and thus the radiationless decay rates of Soret-excited S2 state are also determined by the magnitude of electronic coupling energies.

The photophysics of highly electronically excited states of a set of d0 and d10 metallated tetrapyrroles, which have different peripheral substituents and central metal atoms, macrocycle substitution patterns and macrocycle conformations, have been investigated both theoretically and experimentally. Theoretically, the energies of ground state molecular orbitals and the energies and rank in energy of the excited states have been calculated using density functional theory and time-dependent density functional theory methods. Experimentally, the steady-state absorption and fluorescence spectra have been measured. Temporal fluorescence profiles have been measured using a time correlated single photon counting system for the S1 state and a fluorescence upconversion system for the S2 state.<p> The decay mechanisms of highly electronically excited states are governed by the nonradiative S2 S1 internal conversion. The possible existence of any excited state (such as S2' or dark state) lying close to the S2 state and its participation in the nonradiative decay processes of the S2 state has been discussed. The ultrafast nonradiative decay rates of the S2 S1 internal conversion were interpreted on the basis of the energy gap law of radiationless transition theory. For magnesium tetraphenylporphyrin (MgTPP), the radiationless rates (knr)of its S2 state follows the prediction of the energy gap law for the weak coupling statistical limit case. However, the S2 S1 electronic coupling energies of the other metalloporphyrins investigated fall within the inermediate to strong coupling range. The difference of knr relative to the weak coupling limit can be rationalized by the different magnitudes of electronic coupling energies. The magnitude of electronic coupling energies is the major factor in determining the radiationless depopulation rate constants of the S2 states in metallated tetrapyrroles which have S2 S1 electronic coupling energies exceeding the weak coupling limit. In some cases, such as ZnOEP, the magnitude of Frack-Condon factor has only minor effect.<p> The photophysics of Soret-excited metallated corroles have also been investigated in this study. Primary work has shown that two metallated corroles examined have similar S2 S1 interstate electronic coupling energies to that of CdTPP and thus the radiationless decay rates of Soret-excited S2 state are also determined by the magnitude of electronic coupling energies.

京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第21428号 / 農博第2306号 / 学位論文||H30||N5156(農学部図書室) / 京都大学大学院農学研究科地域環境科学専攻 / (主査)教授 近藤 直, 准教授 小川 雄一, 教授 飯田 訓久 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DGAM