Phytochelatins (PCs) are thiol-rich peptides, enzymatically synthesized by plants and algae under exposure to certain metals (Cd, Pb, Zn, Ag, As, Cu). Due to their ability to bind metal ions, they play an important role in the cellular detoxification, forming stable metal–PC complexes that minimize the intracellular deleterious effects of metals. The aim of the present work was to evaluate the efficiency of PC–Cd chelation in the freshwater diatom Nitzschia palea under 0, 0.1 and 0.2 mg Cd L−1, which induced different levels of oxidative stress. This objective was accomplished by the isolation of PC–Cd complexes through size exclusion chromatography. Two peaks were identified, corresponding to high molecular weight (HMW) and low molecular weight (LMW) complexes. In each of the complexes, Cd was quantified by inductively coupled plasma-mass spectrometry, thiol composition was determined by HPLC analysis and the efficiency of Cd chelation calculated by –SH/Cd ratios in HMW and LMW complexes at both Cd concentrations. Results showed that the majority of intracellular Cd was complexed with PCs (75.2–91.2 %). PCs-binding efficiency in this diatom species was higher at HMW than at LMW complexes and enhanced with the increase of Cd concentration exposure. Our work evidenced the important role of PCs as the main intracellular tolerance mechanism in this species. The efficiency increase of Cd–PC binding is related to the increment of PCs synthesis and to the number of Cd ions coordinately bonded to –SH groups in LMW and HMW complexes.
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The authors declare that they have no conflict of interest.
Author information Authors and AffiliationsDepartment of Biology and CESAM, University of Aveiro, Campus Universitário de Santiago, 3810-193, Aveiro, Portugal
Etelvina Figueira & Rosa Freitas
Institute of Aquatic Ecology, University of Girona, Campus de Montilivi, 17071, Girona, Spain
Helena Guasch
Department of Biology and GEOBIOTEC, University of Aveiro, 3810-193, Aveiro, Portugal
Salomé F. P. Almeida
Correspondence to Etelvina Figueira.
About this article Cite this articleFigueira, E., Freitas, R., Guasch, H. et al. Efficiency of cadmium chelation by phytochelatins in Nitzschia palea (Kützing) W. Smith. Ecotoxicology 23, 285–292 (2014). https://doi.org/10.1007/s10646-013-1172-8
Accepted: 26 December 2013
Published: 08 January 2014
Issue Date: March 2014
DOI: https://doi.org/10.1007/s10646-013-1172-8
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