| 1. |
- Alsufyani, Maryam, et al.
(författare)
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Lactone Backbone Density in Rigid Electron-Deficient Semiconducting Polymers Enabling High n-type Organic Thermoelectric Performance
- 2022
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Ingår i: Angewandte Chemie International Edition. - : WILEY-V C H VERLAG GMBH. - 1433-7851 .- 1521-3773. ; 61:7
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Tidskriftsartikel (refereegranskat)abstract
- Three lactone-based rigid semiconducting polymers were designed to overcome major limitations in the development of n-type organic thermoelectrics, namely electrical conductivity and air stability. Experimental and theoretical investigations demonstrated that increasing the lactone group density by increasing the benzene content from 0 % benzene (P-0), to 50 % (P-50), and 75 % (P-75) resulted in progressively larger electron affinities (up to 4.37 eV), suggesting a more favorable doping process, when employing (N-DMBI) as the dopant. Larger polaron delocalization was also evident, due to the more planarized conformation, which is proposed to lead to a lower hopping energy barrier. As a consequence, the electrical conductivity increased by three orders of magnitude, to achieve values of up to 12 S cm and Power factors of 13.2 mu Wm(-1) K-2 were thereby enabled. These findings present new insights into material design guidelines for the future development of air stable n-type organic thermoelectrics.
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| 2. |
- Aronsson, Henrik, 1971, et al.
(författare)
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In vivo assessment of the significance of phosphorylation of the Arabidopsis chloroplast protein import receptor, atToc33
- 2006
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Ingår i: FEBS Letters. - : Wiley. - 0014-5793. ; 580:2, s. 649-655
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Tidskriftsartikel (refereegranskat)abstract
- atToc33 is a transit peptide receptor of the chloroplast outer envelope membrane, and possesses GTPase activity. In vitro, its transit peptide- and GTP-binding properties are abrogated by its phosphorylation at serine 181, which was proposed to represent an important regulatory mechanism. We mutated S181 to alanine (to prevent phosphorylation), and to aspartate and glutamate (to mimic the effects of phosphoserine), and expressed all three proteins in ppi1 (atToc33 knockout) plants using the native promoter. The mutants complemented ppi1 with equal efficiency in respect of all criteria tested, including protein import efficiency and light stress tolerance. The data suggest that atToc33 phosphorylation may not play an important role in vivo.
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| 3. |
- Aronsson, Henrik, 1971, et al.
(författare)
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Nucleotide binding and dimerization at the chloroplast pre-protein import receptor, atToc33, are not essential in vivo but do increase import efficiency
- 2010
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Ingår i: PLANT JOURNAL. - 0960-7412. ; 63:2, s. 297-311
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Tidskriftsartikel (refereegranskat)abstract
- P>The atToc33 protein is one of several pre-protein import receptors in the outer envelope of Arabidopsis chloroplasts. It is a GTPase with motifs characteristic of such proteins, and its loss in the plastid protein import 1 (ppi1) mutant interferes with the import of photosynthesis-related pre-proteins, causing a chlorotic phenotype in mutant plants. To assess the significance of GTPase cycling by atToc33, we generated several atToc33 point mutants with predicted effects on GTP binding (K49R, S50N and S50N/S51N), GTP hydrolysis (G45R, G45V, Q68A and N101A), both binding and hydrolysis (G45R/K49N/S50R), and dimerization or the functional interaction between dimeric partners (R125A, R130A and R130K). First, a selection of these mutants was assessed in vitro, or in yeast, to confirm that the mutations have the desired effects: in relation to nucleotide binding and dimerization, the mutants behaved as expected. Then, activities of selected mutants were tested in vivo, by assessing for complementation of ppi1 in transgenic plants. Remarkably, all tested mutants mediated high levels of complementation: complemented plants were similar to the wild type in growth rate, chlorophyll accumulation, photosynthetic performance, and chloroplast ultrastructure. Protein import into mutant chloroplasts was also complemented to > 50% of the wild-type level. Overall, the data indicate that neither nucleotide binding nor dimerization at atToc33 is essential for chloroplast import (in plants that continue to express the other TOC receptors in native form), although both processes do increase import efficiency. Absence of atToc33 GTPase activity might somehow be compensated for by that of the Toc159 receptors. However, overexpression of atToc33 (or its close relative, atToc34) in Toc159-deficient plants did not mediate complementation, indicating that the receptors do not share functional redundancy in the conventional sense.
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