Biotic ligand model explains the effects of competition but not complexation for Sm biouptake by Chlamydomonas reinhardtii.
The applicability of the biotic ligand model (BLM) was tested with respect to the biouptake of the lanthanide Sm by the freshwater green alga, Chlamydomonas reinhardtii. In the absence of organic ligands, Sm uptake was well described by the Michaelis-Menten equation, consistent with the BLM assumption of single transporter, with the maximum influx rate (Jmax) of 1.5 × 10-14mol cm-2s-1and a binding constant (KSm) of 107.0M-1. The addition of organic ligands (i.e., malic acid, diglycolic acid and citric acid) decreased Sm influx rates, however, the decreases were much less than that predicted by the BLM, possibly due to the direct contribution of the Sm complexes. Competition effects of two major cations (Ca2+and Mg2+) and three lanthanide cations (La3+, Ce3+and Eu3+) were successfully modeled by the BLM, with binding constants corresponding to KCa= 104.0M-1, KMg= 102.7M-1, KLa= 106.8M-1, KCe= 106.9M-1and KEu= 107.0M-1. The binding constants and Jmaxwere very similar among the four investigated lanthanides and varied progressively with atomic number; therefore, the results obtained in the present study can probably be extrapolated to other rare earth metals.
College of the Environment and Ecology, Xiamen University, Xiamen, Fujian 361102, China; Department of Chemistry, University of Montreal, P.O. Box 6128, Succursale Centre-ville, Montréal, Québec H3C 3J7, Canada.
Qiao-Guo
QG
Tan
Department of Chemistry, University of Montreal, P.O. Box 6128, Succursale Centre-ville, Montréal, Québec H3C 3J7, Canada; College of Urban Construction, Hebei University of Engineering, Handan, Hebei, China.
Guang
G
Yang
Department of Chemistry, University of Montreal, P.O. Box 6128, Succursale Centre-ville, Montréal, Québec H3C 3J7, Canada. Electronic address: kj.wilkinson@umontreal.ca.
Kevin J
KJ
Wilkinson
D002118:Calcium / Q000378:metabolism; D016825:Chlamydomonas reinhardtii / Q000378:metabolism*; D019343:Citric Acid / Q000378:metabolism; D005618:Fresh Water; D006016:Glycolates / Q000378:metabolism; D028581:Lanthanoid Series Elements / Q000378:metabolism*; D008024:Ligands; D008274:Magnesium / Q000378:metabolism; D008293:Malates / Q000378:metabolism; D008962:Models, Theoretical
D006016:Glycolates; D028581:Lanthanoid Series Elements; D008024:Ligands; D008293:Malates; D019343:Citric Acid; C030298:malic acid; D008274:Magnesium; C571256:diglycolic acid; D002118:Calcium
Biotic ligand model; Free ion activity model; Lanthanide; Rare earth elements; Samarium