Jürgens, Sascha-René

[["dc.bibliographiccitation.firstpage","13"],["dc.bibliographiccitation.issue","1"],["dc.bibliographiccitation.journal","Annals of Botany"],["dc.bibliographiccitation.lastpage","22"],["dc.bibliographiccitation.volume","103"],["dc.contributor.author","Hauck, Markus"],["dc.contributor.author","Juergens, Sascha-Rene"],["dc.contributor.author","Willenbruch, Karen"],["dc.contributor.author","Huneck, Siegfried"],["dc.contributor.author","Leuschner, Christoph"],["dc.date.accessioned","2018-11-07T08:33:47Z"],["dc.date.available","2018-11-07T08:33:47Z"],["dc.date.issued","2009"],["dc.description.abstract","Many species of lichen-forming fungi contain yellow or orange extracellular pigments belonging to the dibenzofurans (usnic acid), anthraquinones (e.g. parietin) or pulvinic acid group. These pigments are all equally efficient light screens, leading us to question the potential ecological and evolutionary significance of diversity in yellow and orange lichen substances. Here the hypothesis is tested that the different pigments differ in metal-binding characteristics, which suggest that they may contribute to adaptation to sites differing in pH and metal availability. UV spectroscopy was used to study the dissociation and the pH dependence of the metal-binding behaviour of seven isolated lichen substances in methanol. Metals applied were selected macro- and micro-nutrients (Cu(2+), Fe(2+), Fe(3+), Mg(2+), Mn(2+) and Zn(2+)). All the pigments studied are strong to moderate acids with pK(a1) values between 2.8 and 4.5. Metal complexation is common in the lichen substances studied. Complexation takes place under acidic conditions with usnic acid, but under alkaline conditions with parietin and most compounds of the pulvinic acid group. The pulvinic acid derivative rhizocarpic acid forms metal complexes both in the acidic and the alkaline range. Metal complexation by lichen substances could be a prerequisite for lichen substance-mediated control of metal uptake. Assuming such an effect at pH values where the affinity of the metal for the lichen substance is intermediate would explain the strong preference of lichens with usnic or rhizocarpic acids to acidic substrata. Moreover, it would explain the preference of lichens with parietin and some lichens with compounds of the pulvinic acid group either for nutrient-rich substrata at low pH or for calcareous substrata."],["dc.description.sponsorship","Deutsche Forschungsgemeinschaft [Ha 3152/8-1]"],["dc.identifier.doi","10.1093/aob/mcn202"],["dc.identifier.isi","000261678300003"],["dc.identifier.pmid","18977765"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/17668"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Oxford Univ Press"],["dc.relation.issn","0305-7364"],["dc.title","Dissociation and metal-binding characteristics of yellow lichen substances suggest a relationship with site preferences of lichens"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","2776"],["dc.bibliographiccitation.issue","10"],["dc.bibliographiccitation.journal","Environmental Pollution"],["dc.bibliographiccitation.lastpage","2780"],["dc.bibliographiccitation.volume","157"],["dc.contributor.author","Hauck, Markus"],["dc.contributor.author","Juergens, Sascha-Rene"],["dc.contributor.author","Huneck, Siegfried"],["dc.contributor.author","Leuschner, Christoph"],["dc.date.accessioned","2018-11-07T11:23:29Z"],["dc.date.available","2018-11-07T11:23:29Z"],["dc.date.issued","2009"],["dc.description.abstract","The depsidone fumarprotocetraric acid as well as the depsides perlatolic and thamnolic acids are lichen secondary metabolites. Their first dissociation constants (pK(a1)) in methanol were determined to be 2.7 for perlatolic acid and 2.8 for fumarprotocetraric and thamnolic acids by UV spectroscopy. Lower pK(a1) values are. so far, not known from lichen substances. Several lichens producing at least one of these compounds are known for their outstanding tolerance to acidic air pollution. This is demonstrated by evaluating published pH preferences for central European lichens. The low pK(a1) values suggest that strong dissociation of the studied lichen substances is a prerequisite for the occurrence of lichens with these compounds on very acidic substrata, as protonated lichen substances of different chemical groups, but not their conjugated bases, are known to shuttle protons into the cytoplasm and thereby apparently damage lichens. (C) 2009 Elsevier Ltd. All rights reserved."],["dc.description.sponsorship","Deutsche Forschungsgemeinschaft (DFG) [Ha 3152/8-1]"],["dc.identifier.doi","10.1016/j.envpol.2009.04.022"],["dc.identifier.isi","000269426500027"],["dc.identifier.pmid","19464777"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/56208"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Elsevier Sci Ltd"],["dc.relation.issn","0269-7491"],["dc.title","High acidity tolerance in lichens with fumarprotocetraric, perlatolic or thamnolic acids is correlated with low pK(a1) values of these lichen substances"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]