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- Crispin, Xavier, 1972-, et al.
(författare)
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Electronic delocalization in discotic liquid crystals : A joint experimental and theoretical study
- 2004
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 126:38, s. 11889-11899
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Tidskriftsartikel (refereegranskat)abstract
- Discotic liquid crystals emerge as very attractive materials for organic-based (opto)electronics as they allow efficient charge and energy transport along self-organized molecular columns. Here, angle-resolved photoelectron spectroscopy (ARUPS) is used to investigate the electronic structure and supramolecular organization of the discotic molecule, hexakis(hexylthio)diquinoxalino[2,3-a:2′,3′-c]phenazine, deposited on graphite. The ARUPS data reveal significant changes in the electronic properties when going from disordered to columnar phases, the main feature being a decrease in ionization potential by 1.8 eV following the appearance of new electronic states at low binding energy. This evolution is rationalized by quantum-chemical calculations performed on model stacks containing from two to six molecules, which illustrate the formation of a quasi-band structure with Bloch-like orbitals delocalized over several molecules in the column. The ARUPS data also point to an energy dispersion of the upper π-bands in the columns by some 1.1 eV, therefore highlighting the strongly delocalized nature of the π-electrons along the discotic stacks.
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- Lacombe, D, et al.
(författare)
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The EORTC and drug development
- 2002
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Ingår i: European Journal of Cancer. - 0959-8049 .- 1879-0852. ; 38, s. 19-23
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Tidskriftsartikel (refereegranskat)
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- Lehmann, Jean, et al.
(författare)
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Folding of small RNAs displaying the GNC base-pattern : implications for the self-organization of the genetic system
- 2004
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Ingår i: Journal of Theoretical Biology. - : Elsevier BV. - 0022-5193 .- 1095-8541. ; 227:3, s. 381-395
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Tidskriftsartikel (refereegranskat)abstract
- Theoretical arguments and statistical analyses of present-day coding sequences have long suggested the existence of primitive patterns in RNA sequences, which were thought to have been predominant at the time of the origin of the genetic code. The main propositions were centered around the base-patterns GNC and RNY, where R = A or G, Y = C or U and N = A, G, C or U. A theoretical model of the primitive process of translation explaining the origin of this type of pattern was recently published in the Journal of Theoretical Biology. On the basis of this previous analysis.. and on physico-chemical evidence supporting the idea of the GNC base-pattern as the most primitive one, the present paper shows the results of folding simulations of small RNA strands displaying this pattern, which enabled us to specify the characteristics of the suggested primitive form of tRNA. This analysis is notably based on a conjecture of Eigen and Schuster of an early structural (or pattern) similarity between mRNA and tRNA, and, more specifically, of a "joint function of messenger and adaptor". Working with this conjecture, we show that the convergence of the primitive pool of RNAs toward a system containing a high proportion of sequences displaying the GNC base-pattern (according to the evolutionary model) is accompanied by a significant gain in stability of the translation process. In particular, it is demonstrated how the reading frame would be automatically discriminated without the presence of a start codon.
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- Lehmann, O. J., et al.
(författare)
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Novel anterior segment phenotypes resulting from forkhead gene alterations: Evidence for cross-species conservation of function
- 2003
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Ingår i: Investigative Ophthalmology & Visual Science. - : Association for Research in Vision and Ophthalmology (ARVO). - 0146-0404 .- 1552-5783. ; 44:6, s. 2627-2633
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE. Mutations in murine and human Versions of an ancestrally related gene usually result in similar phenotypes. However, interspecics differences exist, and in the case of two forkhead transcription factor genes (FOXC1 and FOXC2), these differences include corneal or anterior segment phenotypes, respectively. This study was undertaken to determine whether such discrepancies provide an opportunity for identifying novel human-murine ocular phenotypes. METHODS. Four pedigrees with early-onset glaucoma phenotypes secondary to segmental chromosomal duplications or deletions encompassing FOXC1 and 18 individuals from 9 FOXC2 mutation pedigrees underwent detailed ocular phenotyping. Subsequently, mice with mutations in Foxc1 or a related forkhead gene, Foxe3, were assessed for features of the human phenotypes. RESULTS. A significant increase in central corneal thickness was present in affected individuals from the segmental duplication pedigrees compared with their unaffected relatives (mean increase 13%, maximum 35%, P < 0.05). Alterations in corneal thickness were present in mice heterozygous and homozygous for Foxe3 mutations but neither in Foxc1 heterozygotes nor the small human segmental deletion pedigree. Mutations in FOXC2 resulted in ocular anterior segment anomalies. These were more severe and prevalent with mutations involving the forkhead domain. CONCLUSIONS. Normal corneal development is dependent on the precise dose and levels of activity of certain forkhead transcription factors. The altered corneal thickness attributable to increased forkhead gene dosage is particularly important, because it may affect the clinical management of certain glaucoma subtypes and lead to excessive treatment. The FOXC1 and Foxe3 data, taken together with the novel ocular phenotypes of FOXC2 mutations, highlight the remarkable cross-species conservation of function among forkhead genes.
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- Stottrup, J. G., et al.
(författare)
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The use of releases of reared fish to enhance natural populations - A case study on turbot Psetta maxima (Linne, 1758)
- 2002
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Ingår i: Fisheries Research. - 0165-7836. ; 59:1-2, s. 161-180
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Tidskriftsartikel (refereegranskat)abstract
- Turbot Psetta maxima (Linne, 1758) were used as a model species to test if flatfish populations can be enhanced through regular release of reared fish. During 1991-1998, 10,000 I-group fish (11-16 cm) and during 1993-995 around 100,000 0-group fish (4-6 cm), were released each year in the Kattegat, off the northern coast of north Zealand, the most wind and wave exposed site in the inner Danish waters. The larger fish were tagged external, numbered, T-bar tags, whereas the smaller fish were marked with alizarin complexone. The size at release of the reared fish was similar to that of their wild counterparts, although the 0-group released fish were smaller than the average wild fish. The released fish showed a much narrower length distribution due to regular size sorting in the hatchery. The growth of released fish marked with alizarin was similar to or higher than that of their wild counterparts, whereas the externally marked fish grew slower, probably as a result of the external tag. The mortality of the released fish was very variable and relatively high, but was comparable to that of the wild turbot. The releases constituted around a third of the 0-group and almost half of the I-group wild counterparts. Most of the recaptures were close to the release area. Migration of the cultured 1-year-old turbot was less than 10 km and they remained close to the shore during the first 2 years after release. This was followed by a sharp increase in migration distance with an offshore direction, possibly related to spawning behaviour. No apparent difference in depth distribution between cultured and wild turbot was evident and both groups showed the same differences in depth distribution during night- and daytime. No evidence of displacement of the wild stock was found based on the findings of similar growth, similar size distribution in the later year classes and constant ratio of reared and wild fish in the catches. The results suggest that release of reared turbot may result in an increase in fishery recruitment. (C) 2002 Elsevier Science B.V. All rights reserved.
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