title: 'Venus trapped, Mars transits': Cu and Fe redox chemistry, cellular topography and in situ ligand binding in terrestrial isopod hepatopancreas.
abstract: Woodlice efficiently sequester copper (Cu) in 'cuprosomes' within hepatopancreatic 'S' cells. Binuclear 'B' cells in the hepatopancreas form iron (Fe) deposits; these cells apparently undergo an apocrine secretory diurnal cycle linked to nocturnal feeding. Synchrotron-based µ-focus X-ray spectroscopy undertaken on thin sections was used to characterize the ligands binding Cu and Fe in S and B cells of Oniscus asellus (Isopoda). Main findings were: (i) morphometry confirmed a diurnal B-cell apocrine cycle; (ii) X-ray fluorescence (XRF) mapping indicated that Cu was co-distributed with sulfur (mainly in S cells), and Fe was co-distributed with phosphate (mainly in B cells); (iii) XRF mapping revealed an intimate morphological relationship between the basal regions of adjacent S and B cells; (iv) molecular modelling and Fourier transform analyses indicated that Cu in the reduced Cu(+) state is mainly coordinated to thiol-rich ligands (Cu-S bond length 2.3 Å) in both cell types, while Fe in the oxidized Fe(3+) state is predominantly oxygen coordinated (estimated Fe-O bond length of approx. 2 Å), with an outer shell of Fe scatterers at approximately 3.05 Å; and (v) no significant differences occur in Cu or Fe speciation at key nodes in the apocrine cycle. Findings imply that S and B cells form integrated unit-pairs; a functional role for secretions from these cellular units in the digestion of recalcitrant dietary components is hypothesized.
authors.affiliation: Cardiff School of Biosciences, Cardiff University, Park Place, Cardiff CF10 3US, UK.
authors.forename: P
authors.initials: P
authors.lastname: Kille
authors.affiliation: Cardiff School of Biosciences, Cardiff University, Park Place, Cardiff CF10 3US, UK.
authors.forename: A J
authors.initials: AJ
authors.lastname: Morgan
authors.affiliation: Cardiff School of Biosciences, Cardiff University, Park Place, Cardiff CF10 3US, UK kille@cardiff.ac.uk.
authors.forename: K
authors.initials: K
authors.lastname: Powell
authors.affiliation: Diamond Light Source Ltd, Harwell Science and Innovation Campus, Didcot, UK.
authors.forename: J F W
authors.initials: JF
authors.lastname: Mosselmans
authors.affiliation: Cardiff School of Biosciences, Cardiff University, Park Place, Cardiff CF10 3US, UK.
authors.forename: D
authors.initials: D
authors.lastname: Hart
authors.affiliation: Smith and Nephew, Heslington, York Science Park, York YO10 5DF, UK.
authors.forename: P
authors.initials: P
authors.lastname: Gunning
authors.affiliation: Cardiff School of Biosciences, Cardiff University, Park Place, Cardiff CF10 3US, UK.
authors.forename: A
authors.initials: A
authors.lastname: Hayes
authors.affiliation: Cardiff School of Biosciences, Cardiff University, Park Place, Cardiff CF10 3US, UK.
authors.forename: D
authors.initials: D
authors.lastname: Scarborough
authors.affiliation: School of Earth and Ocean Sciences, Cardiff University, Park Place, Cardiff CF10 3AT, UK.
authors.forename: I
authors.initials: I
authors.lastname: McDonald
authors.affiliation: School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Williamson Building, Oxford Road, Manchester M13 9PL, UK.
authors.forename: J M
authors.initials: JM
authors.lastname: Charnock
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000166:cytology / Q000378:metabolism; D001665:Binding Sites; D003300:Copper / Q000032:analysis / Q000378:metabolism*; D043143:Hepatopancreas / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D007501:Iron / Q000032:analysis / Q000378:metabolism*; D033321:Isopoda / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D010084:Oxidation-Reduction; D010710:Phosphates / Q000032:analysis / Q000378:metabolism; D013052:Spectrometry, X-Ray Emission; D013455:Sulfur / Q000032:analysis / Q000378:metabolism
chemical_list: D010710:Phosphates; D013455:Sulfur; D003300:Copper; D007501:Iron
keywords: copper; iron; isopod; speciation; synchrotron; µ-focus