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Table 3.1: Vertical excitation energies (eV) and oscillator strengths of the pp states
of the doublet HBDI radical. The values of hS2i are also shown.
Method D1 hS2i D2 hS2i
SOS-CIS(D)/cc-pVDZa 1.64 (0.02) 1.04 3.53 (1.35) 0.90
SOS-CIS(D)/cc-pVTZa 1.52 (0.02) 1.01 3.37 (1.34) 0.89
EOM-SF-CCSD/6-311G*b 1.93 (0.01) 0.79 4.14 (1.04) 0.81
XMCQDTP2/6-311G*c 1.80 (0.01) 3.27 (0.66)
a Using O2 orbitals. Oscillator strength are computed at the CIS level. b Using B3LYP
orbitals. c Based on SA(8)-CASSCF(12/11).
3.3 Results and discussion
Relevant MOs and electronic states of the gas-phase HBDI anion are shown in Figs. 3.2
and 3.3. Gas-phase photodestruction spectra show the absorption maximum of the
anionic GFP chromophore at 2.59 eV29, 30, which is remarkably close to the absorption
of wild-type GFP at 2.61 eV. Most of the electronic structure studies agree on the char-acter
of the bright state14–17, 19, 21–23, 49, which is of a p ! p type (Fig. 3.2), although
there is a spread in reported excitation energies. Our recent theoretical study revealed
that the bright state is, in fact, a resonance state embedded in a photodetachment con-tinuum.
These calculations determined that the vertical detachment energy (VDE) of
the HBDI anion is 2.4–2.5 eV, which is below the bright state. A recent experimental
study50, which also employed electronic action spectroscopy, reported the vertical exci-tation
energy of 2.60 eV and determined VDE to lie within 2.48–2.8 eV, in excellent
agreement with our computational predictions.
89
Object Description
| Title | Development of predictive electronic structure methods and their application to atmospheric chemistry, combustion, and biologically relevant systems |
| Author | Epifanovskiy, Evgeny |
| Author email | epifanov@usc.edu; epifanov@usc.edu |
| Degree | Doctor of Philosophy |
| Document type | Dissertation |
| Degree program | Chemistry |
| School | College of Letters, Arts and Sciences |
| Date defended/completed | 2011-03-21 |
| Date submitted | 2011 |
| Restricted until | Unrestricted |
| Date published | 2011-04-28 |
| Advisor (committee chair) | Krylov, Anna I. |
| Advisor (committee member) |
Wittig, Curt Johnson, Clifford |
| Abstract | This work demonstrates electronic structure techniques that enable predictive modeling of the properties of biologically relevant species. Chapters 2 and 3 present studies of the electronically excited and detached states of the chromophore of the green fluorescent protein, the mechanism of its cis-trans isomerization, and the effect of oxidation. The bright excited ππ∗ state of the chromophore in the gas phase located at 2.6 eV is found to have an autoionizing resonance nature as it lies above the electron detachment level at 2.4 eV. The calculation of the barrier for the ground-state cis-trans isomerization of the chromophore yields 14.8 kcal/mol, which agrees with an experimental value of 15.4 kcal/mol; the electronic correlation and solvent stabilization are shown to have an important effect. In Chapter 3, a one-photon two-electron mechanism is proposed to explain the experimentally observed oxidative reddening of the chromophore. Chapter 4 considers the excited states of uracil. It demonstrates the role of the one-electron basis set and triples excitations in obtaining the converged values of the excitation energies of the nπ∗ and ππ∗ states. The effects of the solvent and protein environment are included in some of the models.; Chapter 5 describes an implementation of the algorithm for locating and exploring intersection seams between potential energy surfaces. The theory is illustrated with examples from atmospheric and combustion chemistry. |
| Keyword | electronic structure theory; coupled clusters theory; equation of motion theory; organic chromophore; green fluorescent protein; uracil |
| Language | English |
| Part of collection | University of Southern California dissertations and theses |
| Publisher (of the original version) | University of Southern California |
| Place of publication (of the original version) | Los Angeles, California |
| Publisher (of the digital version) | University of Southern California. Libraries |
| Provenance | Electronically uploaded by the author |
| Type | texts |
| Legacy record ID | usctheses-m3801 |
| Contributing entity | University of Southern California |
| Rights | Epifanovskiy, Evgeny |
| Repository name | Libraries, University of Southern California |
| Repository address | Los Angeles, California |
| Repository email | cisadmin@lib.usc.edu |
| Filename | etd-Epifanovskiy-4557 |
| Archival file | uscthesesreloadpub_Volume14/etd-Epifanovskiy-4557.pdf |
Description
| Title | Page 99 |
| Contributing entity | University of Southern California |
| Repository email | cisadmin@lib.usc.edu |
| Full text | Table 3.1: Vertical excitation energies (eV) and oscillator strengths of the pp states of the doublet HBDI radical. The values of hS2i are also shown. Method D1 hS2i D2 hS2i SOS-CIS(D)/cc-pVDZa 1.64 (0.02) 1.04 3.53 (1.35) 0.90 SOS-CIS(D)/cc-pVTZa 1.52 (0.02) 1.01 3.37 (1.34) 0.89 EOM-SF-CCSD/6-311G*b 1.93 (0.01) 0.79 4.14 (1.04) 0.81 XMCQDTP2/6-311G*c 1.80 (0.01) 3.27 (0.66) a Using O2 orbitals. Oscillator strength are computed at the CIS level. b Using B3LYP orbitals. c Based on SA(8)-CASSCF(12/11). 3.3 Results and discussion Relevant MOs and electronic states of the gas-phase HBDI anion are shown in Figs. 3.2 and 3.3. Gas-phase photodestruction spectra show the absorption maximum of the anionic GFP chromophore at 2.59 eV29, 30, which is remarkably close to the absorption of wild-type GFP at 2.61 eV. Most of the electronic structure studies agree on the char-acter of the bright state14–17, 19, 21–23, 49, which is of a p ! p type (Fig. 3.2), although there is a spread in reported excitation energies. Our recent theoretical study revealed that the bright state is, in fact, a resonance state embedded in a photodetachment con-tinuum. These calculations determined that the vertical detachment energy (VDE) of the HBDI anion is 2.4–2.5 eV, which is below the bright state. A recent experimental study50, which also employed electronic action spectroscopy, reported the vertical exci-tation energy of 2.60 eV and determined VDE to lie within 2.48–2.8 eV, in excellent agreement with our computational predictions. 89 |
