Jürgens, Sascha-René

[["dc.bibliographiccitation.firstpage","309"],["dc.bibliographiccitation.issue","3"],["dc.bibliographiccitation.journal","Environmental and Experimental Botany"],["dc.bibliographiccitation.lastpage","313"],["dc.bibliographiccitation.volume","68"],["dc.contributor.author","Hauck, Markus"],["dc.contributor.author","Juergens, Sascha-Rene"],["dc.contributor.author","Leuschner, Christoph"],["dc.date.accessioned","2018-11-07T08:43:30Z"],["dc.date.available","2018-11-07T08:43:30Z"],["dc.date.issued","2010"],["dc.description.abstract","The depsidone norstictic acid is a widespread secondary metabolite produced by lichen-forming fungi. Like other lichen substances, most of the norstictic acid is deposited as crystals in the apoplast of lichens, whereas only a small proportion is soluble in water. Since recent studies suggested a role of lichen substances in shaping the preferences of lichens for specific pH conditions and metal availabilities in their environment, we studied physico-chemical properties of norstictic acid to test the hypothesis that the dissociation and metal-binding behavior of this substance could explain the ecological characteristics of norstictic acid-producing lichens with respect to pH and metal availability. UV spectroscopy was used to study the dissociation and the pH dependence of the metal-binding behavior of isolated norstictic acid in methanol. Metals applied were selected macro- and micro-nutrients (Ce2+, Fe2+, Fe3+, Mg2+, Mn2+, Zn2+). The first dissociation constant (pK(a1)) of norstictic acid amounts to 4.0. It is higher than that of other lichen substances produced by lichens at strongly acidic sites but equals that of the dibenzofuran usnic acid. In solutions containing norstictic acid and Cu2+, Mn2+ or Zn2+ increasing absorbance was observed at pH > 7.5 indicating increasing affinity of the metal ions for the norstictic acid along with pH. Fe2+ and Mg2+ do not form complexes with norstictic acid. The relative high pK(a1) value of norstictic acid is probably responsible for the lack of norstictic acid-producing lichens on strongly acidic substrata. At pH << 4, norstictic acid is thought to damage lichens by shuttling protons into the cytoplasm. Moderate affinity of norstictic acid to Cu2+, Fe3+, Mn2+ and Zn2+ suggests a potential role at controlling the uptake of these ions at slightly alkaline conditions. (C) 2010 Elsevier B.V. All rights reserved."],["dc.description.sponsorship","Deutsche Forschungsgemeinschaft [Ha 3152/8-1]"],["dc.identifier.doi","10.1016/j.envexpbot.2010.01.003"],["dc.identifier.isi","000276741400010"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/19979"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Pergamon-elsevier Science Ltd"],["dc.relation.issn","0098-8472"],["dc.title","Norstictic acid: Correlations between its physico-chemical characteristics and ecological preferences of lichens producing this depsidone"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["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","1"],["dc.bibliographiccitation.issue","1"],["dc.bibliographiccitation.journal","The Bryologist"],["dc.bibliographiccitation.lastpage","7"],["dc.bibliographiccitation.volume","113"],["dc.contributor.author","Hauck, Markus"],["dc.contributor.author","Juergens, Sascha-Rene"],["dc.contributor.author","Leuschner, Christoph"],["dc.date.accessioned","2018-11-07T08:45:15Z"],["dc.date.available","2018-11-07T08:45:15Z"],["dc.date.issued","2010"],["dc.description.abstract","UV spectroscopy confirmed that the lichen-derived pulvinic acid derivative epanorin forms complexes with metal ions (Cu(2+), Fe(2+), Fe(3+), Mg(2+), Mg(2+), Mn(2+), Zn(2+),) at two binding sites both under acidic and alkaline conditions. Similar observations in rhizocarpic acid suggest that the amino acid moieties in both epanorin and rhizocarpic acid are responsible for metal binding at low pH, whereas pulvinic acids without an amino acid moiety bind only to metal ions under alkaline conditions. Metal complexation at low pH is thought to enable lichens with epanorin or rhizocarpic acid to colonize acidic, nutrient-poor substrata, whereas lichens with pulvinic acids without an amino acid moiety prefer either neutral to alkaline or acidic but nutrient-rich substrata. High dissociation constants of epanorin (pK(a)=4.9) and rhizocarpic acid (pK(a)=4.5) in methanol suggest that the amino acid groups in these substances prevent them from acting as a protonophore. Otherwise the relatively high pK(a) values of epanorin and rhizocarpic acid would result in damage of lichens containing these substances at low pH, which is not observed."],["dc.description.sponsorship","German Science Foundation [DFG Ha 3152/8-1]"],["dc.identifier.doi","10.1639/0007-2745-113.1.1"],["dc.identifier.isi","000275979900001"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/20392"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Amer Bryological Lichenological Soc Inc"],["dc.relation.issn","0007-2745"],["dc.title","Effect of amino acid moieties on metal binding in pulvinic acid derivatives and ecological implications for lichens producing these compounds"],["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"]]