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- Burman, Robert, et al.
(författare)
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Distribution of circular proteins in plants : large-scale mapping of cyclotides in the Violaceae
- 2015
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Ingår i: Frontiers in Plant Science. - : Frontiers Media SA. - 1664-462X. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- During the last decade there has been increasing interest in small circular proteins found in plants of the violet family (Violaceae). These so-called cyclotides consist of a circular chain of approximately 30 amino acids, including six cysteines forming three disulfide bonds, arranged in a cyclic cystine knot (CCK) motif. In this study we map the occurrence and distribution of cyclotides throughout the Violaceae. Plant material was obtained from herbarium sheets containing samples up to 200 years of age. Even the oldest specimens contained cyclotides in the preserved leaves, with no degradation products observable, confirming their place as one of the most stable proteins in nature. Over 200 samples covering 17 of the 23-31 genera in Violaceae were analyzed, and cyclotides were positively identified in 150 species. Each species contained a unique set of between one and 25 cyclotides, with many exclusive to individual plant species. We estimate the number of different cyclotides in the Violaceae to be 5000-25,000, and propose that cyclotides are ubiquitous among all Violaceae species. Twelve new cyclotides from six phylogenetically dispersed genera were sequenced. Furthermore, the first glycosylated derivatives of cyclotides were identified and characterized, further increasing the diversity and complexity of this unique protein family.
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- El-Seedi, Hesham R., et al.
(författare)
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Naturally occurring xanthones; latest investigations : isolation, structure elucidation and chemosystematic significance
- 2009
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Ingår i: Current Medicinal Chemistry. - : Bentham Science Publishers Ltd.. - 0929-8673 .- 1875-533X. ; 16:20, s. 2581-2626
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Forskningsöversikt (refereegranskat)abstract
- In this review, an updated literature survey covering the reports of naturally occurring xanthones in the period of 2005-2008 is presented. In some 143 studies, the isolation of 264 different xanthones from 36 plant species (representing 15 genera in 6 families of higher plants), 7 species of fungi, and 1 lichen species were reported. Of these, 122 compounds were isolated for the first time from nature. We discuss plant origin, the way of separation, and spectral analysis done for structure elucidation, along with a brief discussion of the chemosystematic significance.
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- Larsson, Sonny, 1975-
(författare)
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Mistletoes and Thionins : as Selection Models in Natural Products Drug Discovery
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The process of drug discovery from natural products starts with the selection of study object. In this project recent knowledge and methods are incorporated to investigate the process of such selection for pharmacognostic investigations. As the model and object of study mistletoes and their content of the small cytotoxic peptides thionins are chosen.The thionins are compared in silico to other proposed plant innate defense peptides. Utilizing analysis of amino acid sequences and secondary structures, the thionins are shown to be one of eight distinct groups of cystein-rich plant polypeptides analysed. Common features of thionins are exploited in an investigation of isolation methods, where a simple acidic extraction is equally efficient to isolate thionins as the laborious methods hitherto used. An effort to study the relationships of the order Santalales was done. To infer phylogenetic relationships from DNA sequences, we increased the taxon sampling for utilized genes and regions such as rbcL, atpB and ribosomal 18S and 26S rDNA sequences within the Santalales. Analysing these together with published sequences for other tricolpate taxa a position for Santalales as sister to caryophyllids and basal to asterids is implied. This indication is supported by chemical characters such as the presence of cyclopeptide alkaloids of a kind only known from Gentianales.To validate the chemosystematic implications from thionin distribution extracts of mistletoes collected in Panama, Taiwan and Madagascar, and the relative Osyris alba (Santalaceae) collected in Spain, were screened with the established fluorescence microculture cytotoxicity assay using the thionin-sensitive human lymphoma cell-line U937GTB. Bioassay guided isolation concludes that the cytotoxic compounds in Loranthaceae may however constitute another group of peptides.In conclusion this work shows that the incorporation of informatic techniques may aid prediction and decision making when planning pharmacognostic research.
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