title: Selective binding of Ca2+, Zn2+, Cu2+ and K+ by the physodes of the green alga Mougeotia scalaris.
abstract: Cells of the zygnematophycean green alga Mougeotia contain numerous globules with polyphenolic matrix, which resemble physodes. In order to analyse the capability of this compartment to sequester various ions, trichomes of Mougeotia scalaris were either fixed for X-ray microanalysis simultaneously in 2% glutardialdehyde/1% OsO4 in phosphate buffers of different K+/Na(+)-ratios, or embedded directly (fresh material) in Nanoplast resin. In addition, fixed material was treated with potassium antimonate and Ca2+ localization was examined by electron microscopic cytochemistry. A Ca(2+)-depletion upon fixation at different K+/Na(+)-ratios resulted in selective uptake of potassium, but not sodium. Consistent with earlier findings, calcium-binding by the polyphenolic physode matrix does not depend merely on electric charge but also on the presence of protonated/deprotonated phenolic groups, together with ester-linked carbonyl oxygen, which seem to be good candidates for a co-ordinate type of calcium-binding. Nanoplast embedding turned out to be the most adequate and fastest preparation for X-ray microanalysis and, apart from retaining calcium, allowed the detection of zinc and copper inside the physodes.
authors.affiliation: Institute of Biology, Nicholas Copernicus University, Toruń, Poland.
authors.forename: A
authors.initials: A
authors.lastname: Tretyn
authors.forename: F
authors.initials: F
authors.lastname: Grolig
authors.forename: G
authors.initials: G
authors.lastname: Magdowski
authors.forename: G
authors.initials: G
authors.lastname: Wagner
mesh_terms: D002118:Calcium / Q000378:metabolism; D000460:Chlorophyta / Q000378:metabolism* / Q000648:ultrastructure; D003300:Copper / Q000378:metabolism; D004577:Electron Probe Microanalysis; D008670:Metals / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism; D015032:Zinc / Q000378:metabolism
chemical_list: D008670:Metals; D003300:Copper; D015032:Zinc; D011188:Potassium; D002118:Calcium