Biomedical subjects

Jouko Korppi-Tommola

Publications and source records attributed to Jouko Korppi-Tommola.

7 recordsLinked to original sources

PubMed2006

A dye-sensitized solar cell driven electrochromic device.

A new dye-sensitized solar cell driven electrochromic device has been fabricated. The device consists of an electrochromic display and a solar cell in a single nanocrystalline film. The optimization of the electrochromic and the solar cell functions was carried out. An applied potential of 1.0 V was required for coloring and the best solar energy conversion efficiency 1.1% was achieved. The efficiency may be compared to an efficiency of 4.6% obtained in a similar dye-sensitized solar cell without the display property. Coloring and bleaching times of the device were less than one second and a transmittance change from 38.7% (bleached) to 15.9% (colored) at best was achieved. The optimization of the electrochromic property of the device lead to decreasing efficiency of the solar cell and vice versa.

Journal Article↗

PubMed2006

Excitation energy transfer in the LHC-II trimer: a model based on the new 2.72 A structure.

Energy transfer of the light harvesting complex LHC-II trimer, extracted from spinach, was studied in the Q(y) region at room temperature by femtosecond transient absorption spectroscopy. Configuration interaction exciton method [Linnanto et al. (1999) J Phys Chem B 103: 8739-8750] and 2.72 A structural information reported by Liu et al. was used to calculate spectroscopic properties and excitation energy transfer rates of the complex. Site energies of the pigments and coupling constants of pigment pairs in close contact were calculated by using a quantum chemical configuration interaction method. Gaussian random variation of the diagonal and off-diagonal exciton matrix elements was used to account for inhomogeneous broadening. Rate calculations included only the excitonic states initially excited and probed in the experiments. A kinetic model was used to simulate time and wavelength dependent absorption changes after excitation on the blue side of the Q(y) transition and compared to experimentally recorded rates. Analysis of excitonic wavefunctions allowed identification of pigments initially excited and probed into later. It was shown that excitation of the blue side of the Q(y) band of a single LHC-II complex results in energy transfer from chlorophyll b's of the lumenal side to chlorophyll a's located primarly on one of the monomers of the stromal side.

Absorption↗

PubMed2005

Quantum chemical simulation of excited states of chlorophylls, bacteriochlorophylls and their complexes.

The present review describes the use of quantum chemical methods in estimation of structures and electronic transition energies of photosynthetic pigments in vacuum, in solution and imbedded in proteins. Monomeric Mg-porphyrins, chlorophylls and bacteriochlorophylls and their solvent 1:1 and 1:2 complexes were studied. Calculations were performed for Mg-porphyrin, Mg-chlorin, Mg-bacteriochlorin, mesochlorophyll a, chlorophylls a, b, c(1), c(2), c(3), d and bacteriochlorophylls a, b, c, d, e, f, g, h, plus several homologues. Geometries were optimised with PM3, PM3/CISD, PM5, ab initio HF (6-31G*/6-311G**) and density functional B3LYP (6-31G*/6-311G**) methods. Spectroscopic transition energies were calculated with ZINDO/S CIS, PM3 CIS, PM3 CISD, ab initio CIS, time-dependent HF and time-dependent B3LYP methods. Estimates for experimental transition energies were obtained from linear correlations of the calculated transition energies of 1:1 solvent complexes against experimentally recorded solution energies (scaling). According to the calculations in five-coordinated solvent complexes the magnesium atom lies out of the porphyrin plane, while in six-coordinated complexes the porphyrin is nearly planar. Charge densities on magnesium and nitrogen atoms were strongly dependent on the computational method deployed. Several dark states of low oscillator strength below the main Soret band were predicted for solvent complexes and chlorophylls and bacteriochlorophylls in protein environment. Such states, though not yet identified experimentally, might serve as intermediate states for excitation energy transfer in photosynthetic complexes. Q(y), Q(x) and Soret transition energies were found to depend on the orientation of the acetyl group and external pressure. A method to estimate site energies and dimeric interaction energies and to simulate absorption and CD spectra of photosynthetic complexes is described. Simulations for the light harvesting complexes Rhodospirillum molischianum, chlorosomes of Chlorobium tepidum and Chloroflexus aurantiacus, and LHC-II of Spinacia oleracea are presented as examples.

Bacteriochlorophylls↗

PubMed2005

Study of mechanisms of light-induced dissociation of Ru(dcbpy)(CO)2I2 in solution down to 20 fs time resolution.

Mechanisms of the light-induced ligand exchange reaction of (trans-I) Ru(dcbpy)(CO)2I2 (dcbpy = 4,4'-dicarboxylic acid-2,2'-bipyridine) in ethanol have been studied by transient absorption spectroscopy. Ultraviolet 20 fs excitation pulses centered at 325 nm were used to populate a vibrationally hot excited pi bipyridyl state of the reactant that quickly relaxes to a dissociative Ru-I state resulting in the release of one of the carbonyl groups. Quantum yield measurements have indicated that about 40% of the initially exited reactant molecules form the final photoproduct. A 62 fs rise component in the transient absorption (TA) signal was observed at all probe wavelengths in the visible region for the ongoing reaction, while the rise for the photoproduct was pulse limited (20 fs). We assign the observed 62 fs time component to the depopulation of the repulsive CO dissociative state. Vibrational coherences of the TA signals were observed at a wavenumber of 90 cm(-1). The resolved frequency, typical of I-Ru-I vibrational modes, is assigned to trans-cis isomerization of the iodines of the five-coordinated intermediate and damping of this oscillation in 500 fs to simultaneous solvent coordination. Cooling of the hot reactant and the product molecules occurs on a much slower time scale from 4 to 270 ps (Lehtovuori, V.; Aumanen, J.; Myllyperkiö, P.; Rini, M.; Nibbering, E. T. J.; Korppi-Tommola, J. J. Phys. Chem. A 2004, 108, 1644).

Journal Article↗

PubMed2004

Characterization of used mineral oil condition by spectroscopic techniques.

Optical absorption, fluorescence, and quantitative 13C NMR spectroscopy have been used to study the degradation of mineral gearbox oil. Samples of used oil were collected from field service. Measured absorption, fluorescence, and quantitative 13C NMR spectra of used oils show characteristic changes from the spectra of a fresh oil sample. A clearly observable, approximately 20-nm blueshift of the fluorescence emission occurs during the early stages of oil use and correlates with changes in intensity of some specific 13C NMR resonance lines. These changes correlate with oil age because of the connection between the blueshift and breaking of the larger conjugated hydrocarbons of oil as a result of use.

Journal Article↗

PubMed2004

Semiempirical PM5 molecular orbital study on chlorophylls and bacteriochlorophylls: comparison of semiempirical, ab initio, and density functional results.

The semiempirical PM5 method has been used to calculate fully optimized structures of magnesium-bacteriochlorin, magnesium-chlorin, magnesium-porphin, mesochlorophyll a, chlorophylls a, b, c(1), c(2), c(3), and d, and bacteriochlorophylls a, b, c, d, e, f, g, and h with all homologous structures. Hartree-Fock/6-31G* ab initio and density functional B3LYP/6-31G* methods were used to optimize structures of methyl chlorophyllide a, chlorophyll c(1), and methyl bacteriochlorophyllides a and c for comparison. Spectroscopic transition energies of the chromophores and their 1:1 or 1:2 solvent complexes were calculated with the Zindo/S CIS method. The self-consistent reaction field model was used to estimate solvent shifts. The PM5 calculations predict planar structure of the porphyrin ring and central position of the four coordinated magnesium atoms in all pigments studied, in accord with the experimental, ab initio, and density functional results, a significant improvement as compared to the older semiempirical PM3 approach. Only small differences in PM5 and B3LYP/6-31G* or Hartree-Fock/6-31G* minimum energy geometries of the reference molecules were observed. Calculations show that in 1:1 solvent complexes, where the magnesium atom is five coordinated, the magnesium atom is shifted out of the plane of the porphyrin ring towards the solvent molecule, while the hexa coordinated 1:2 complexes are again planar. The PM5 method gives atomic charges that are comparable with those obtained from the Hartree-Fock/6-31G* and B3LYP/6-31G* calculations. The single point ZINDO/S CIS calculations with PM5 minimum energy structure gave excellent correlations between calculated and experimental transition energies of the chlorophylls and bacteriochlorophylls studied. Such correlations may be used for prediction of transition energies of the chromophores in protein binding sites. Calculations also predict existence of dark electronic states below the main Soret absorption band in all chromophores studied. The results suggest that the semiempirical PM5 method is a fairly reliable and computationally efficient method in predicting molecular parameters of porphyrin-like molecules.

Bacteriochlorophylls↗

PubMed2003

Laser-induced plasma spectroscopy to as low as 130 nm when a gas-purged spectrograph and ICCD detection are used.

An experimental setup is described for measuring laser-induced plasma emission spectra in the near vacuum UV with a Czerny-Turner spectrograph and intensified charge-coupled device under atmospheric pressure. With a simple gas-purge technique, emission lines down to 130 nm could be recorded. The strongest emission lines of bromine, chlorine, and iodine in the near vacuum UV are easily detected.

Journal Article↗