title: Effects of H+ concentration on amorphous mineral granules: structural stability and elemental mobilization.
abstract: Phosphate-rich amorphous mineral granules (AMG) have been studied in a number of organisms, and show different physical and chemical properties according to their organic and mineral composition. We studied AMG isolated from the hepatopancreas of the land crab Ucides cordatus, which were subjected to different pHs in order to mimic the possible effects of H(+) on these structures. We used scanning and transmission electron microscopy (SEM, TEM), energy-filtering transmission electron microscopy (EFTEM), energy-dispersive X-ray analysis (EDXA) and nuclear magnetic resonance (NMR). TEM showed that granules were structurally disrupted when subjected to pH 5. The granules contain a soluble fraction that is rich in orthophosphate, which was the most abundant form of phosphate, although pyrophosphate and glucose-6-phosphate were also detected by (31)P NMR analysis. The redistribution of elements in the structure and pH conditions is discussed, focusing on their possible implications for AMG structure, function and dynamics.
authors.affiliation: Departamento de Morfologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Antônio Carlos, 6627, 31270-901 Belo Horizonte, MG, Brazil. correajr@icb.ufmg.br
authors.forename: José Dias
authors.initials: JD
authors.lastname: Corrêa
authors.forename: Maria Inês
authors.initials: MI
authors.lastname: Bruno
authors.forename: Silvana
authors.initials: S
authors.lastname: Allodi
authors.forename: Marcos
authors.initials: M
authors.lastname: Farina
mesh_terms: D000818:Animals; D003386:Brachyura / Q000737:chemistry*; D002118:Calcium / Q000032:analysis; D002713:Chlorine / Q000032:analysis; D003300:Copper / Q000032:analysis; D003594:Cytoplasmic Granules / Q000737:chemistry* / Q000648:ultrastructure*; D004577:Electron Probe Microanalysis; D043143:Hepatopancreas / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000032:analysis; D008274:Magnesium / Q000032:analysis; D009682:Magnetic Resonance Spectroscopy; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D046032:Microscopy, Energy-Filtering Transmission Electron; D008903:Minerals / Q000737:chemistry*; D009532:Nickel / Q000032:analysis; D010100:Oxygen / Q000032:analysis; D010710:Phosphates / Q000032:analysis; D010758:Phosphorus / Q000032:analysis
chemical_list: D008903:Minerals; D010710:Phosphates; D010758:Phosphorus; D002713:Chlorine; D003300:Copper; D009532:Nickel; D007501:Iron; D008274:Magnesium; D010100:Oxygen; D002118:Calcium