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- Friedlein, Rainer, et al.
(author)
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Role of electronic localization and charge-vibrational coupling in resonant photoelectron spectra of polymers : Application to poly(para-phenylenevinylene)
- 2004
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In: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 69:12
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Journal article (peer-reviewed)abstract
- A combination of x-ray absorption and resonant photoemission (RPE) spectroscopy has been used to study the electronic structure of the one-dimensional conjugated polymer poly (para-phenylenevinylene) in nonordered (as prepared) thin films. The dispersion of RPE features for the decay to localized and delocalized bands are qualitatively different. A theory for band dispersion of RPE in polymers is given, showing the important roles of electronic state localization and vibrational (phonon) excitations for the character of the dispersion.
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- Gustavsson, Niklas, et al.
(author)
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A peptide methionine sulfoxide reductase highly expressed in photosynthetic tissue in Arabidopsis thaliana can protect the chaperone-like activity of a chloroplast-localized small heat shock protein.
- 2002
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In: Plant Journal. - 1365-313X. ; 29:5, s. 545-553
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Journal article (peer-reviewed)abstract
- The oxidation of methionine residues in proteins to methionine sulfoxides occurs frequently and protein repair by reduction of the methionine sulfoxides is mediated by an enzyme, peptide methionine sulfoxide reductase (PMSR, EC 1.8.4.6), universally present in the genomes of all so far sequenced organisms. Recently, five PMSR-like genes were identified in Arabidopsis thaliana, including one plastidic isoform, chloroplast localised plastidial peptide methionine sulfoxide reductase (pPMSR) that was chloroplast-localized and highly expressed in actively photosynthesizing tissue (Sadanandom A et al., 2000). However, no endogenous substrate to the pPMSR was identified. Here we report that a set of highly conserved methionine residues in Hsp21, a chloroplast-localized small heat shock protein, can become sulfoxidized and thereafter reduced back to methionines by this pPMSR. The pPMSR activity was evaluated using recombinantly expressed pPMSR and Hsp21 from Arabidopsis thaliana and a direct detection of methionine sulfoxides in Hsp21 by mass spectrometry. The pPMSR-catalyzed reduction of Hsp21 methionine sulfoxides occurred on a minute time-scale, was ultimately DTT-dependent and led to recovery of Hsp21 conformation and chaperone-like activity, both of which are lost upon methionine sulfoxidation (Härndahl et al., 2001). These data indicate that one important function of pPMSR may be to prevent inactivation of Hsp21 by methionine sulfoxidation, since small heat shock proteins are crucial for cellular resistance to oxidative stress.
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- Friedlein, Rainer, et al.
(author)
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Electronic structure of conjugated polymers and interfaces in polymer-based electronics
- 2003
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In: Synthetic Metals (Proceedings of the International Conference on Science and Technology of Synthetic Metals). - 0379-6779. ; 135:1-3, s. 275-277
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Conference paper (peer-reviewed)abstract
- The electronic structure of conjugated polymers and interfaces in polymer-based electronics were analyzed. Fine structure were observed in the region of the first resonance with pi-final state symmetry, between 284.1 eV and 285.8 eV. The electronic transitions from the non-dispersed C(1s) level to specific parts of the unoccupied band structure were generated. It was found that for a dispersing valence band, in the presence of a core-hole, a given photon energy corresponded to an excitation into a state with a distinct wave vectors.
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