Subcellular and molecular localization of rare earth elements and structural characterization of yttrium bound chlorophyll a in naturally grown fern Dicranopteris dichotoma

摘要

A rare earth element (REE) hyperaccumulator, Dicranopteris dichotoma, sampled from an REE mining area in South-Jiangxi region, was chosen for analysis of 15 REEs at subcellular and molecular levels by inductively coupled plasma-mass spectrometry (ICP-MS). The sum of the concentrations of 15 REEs (X:REEs) of D. dichotoma leaf was about 0.1% dry mass. Results indicated that the Sigma REEs of different subcellular fractions of D. dichotoma leaf were cell walls > organelles > the 'soluble' fraction (i.e., cytosol and vacuoles)> cell membranes. ICP-MS results also showed that REEs existed in chlorophylls and lutein, though REE concentrations in carotene and pheophytin were both lower than the procedural blank levels. The Sigma REEs of crude lipopolysaccharide and Ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) obtained from D. dichotoma leaf were 1200 and 343 mg/kg, respectively. The extended X-ray absorption fine structure (EXAFS) study of D. dichotoma chlorophyll a indicated that yttrium was bound to the porphyrin ring of chlorophyll a, and one yttrium atom was surrounded by four nitrogen atoms with the average yttrium-nitrogen bond length being 0.236 nm. These data might be useful for understanding of the physiological role of REEs in hyperaccumulator D. dichotoma. (c) 2004 Elsevier B.V. All rights reserved.