TY - JOUR
T1 - Adsorption mechanisms of microcystin variant conformations at water–mineral interfaces
T2 - A molecular modeling investigation
AU - Pochodylo, Amy L.
AU - Aoki, Thalia G.
AU - Aristilde, Ludmilla
N1 - Funding Information:
A.L.P. acknowledges a Cornell University Graduate School Fellowship. T.G.A.’s undergraduate research was supported by a grant from the U. S. National Science Foundation (Division of Earth Sciences, EAR 1343063). This work was funded by a start-up package from Cornell University.
PY - 2016/10/15
Y1 - 2016/10/15
N2 - Microcystins (MCs) are potent toxins released during cyanobacterial blooms. Clay minerals are implicated in trapping MCs within soil particles in surface waters and sediments. In the absence of molecular characterization, the relevance of previously proposed adsorption mechanisms is lacking. Towards obtaining this characterization, we conducted Monte Carlo simulations combined with molecular dynamics relaxation of two MC variants, MC-leucine-arginine (MC-LR) and MC-leucine-alanine (MC-LA), adsorbed on hydrated montmorillonite with different electrolytes. The resulting adsorbate structures revealed how MC conformations and aqueous conditions dictate binding interactions at the mineral surface. Electrostatic coupling between the arginine residue and a carboxylate in MC-LR excluded the participation of arginine in mediating adsorption on montmorillonite in a NaCl solution. However, in a CaCl2 solution, the complexation of Ca by two carboxylate moieties in MC-LR changed the MC conformation, which allowed arginine to mediate electrostatic interaction with the mineral. By contrast, due to the lack of arginine in MC-LA, complexation of Ca by only one carboxylate in MC-LA was required to favor Ca-bridging interaction with the mineral. Multiple water-bridged H-bonding interactions were also important in anchoring MCs at the mineral surface. Our modeling results offer molecular insights into the structural and chemical factors that can control the fate of MCs at water-mineral interfaces.
AB - Microcystins (MCs) are potent toxins released during cyanobacterial blooms. Clay minerals are implicated in trapping MCs within soil particles in surface waters and sediments. In the absence of molecular characterization, the relevance of previously proposed adsorption mechanisms is lacking. Towards obtaining this characterization, we conducted Monte Carlo simulations combined with molecular dynamics relaxation of two MC variants, MC-leucine-arginine (MC-LR) and MC-leucine-alanine (MC-LA), adsorbed on hydrated montmorillonite with different electrolytes. The resulting adsorbate structures revealed how MC conformations and aqueous conditions dictate binding interactions at the mineral surface. Electrostatic coupling between the arginine residue and a carboxylate in MC-LR excluded the participation of arginine in mediating adsorption on montmorillonite in a NaCl solution. However, in a CaCl2 solution, the complexation of Ca by two carboxylate moieties in MC-LR changed the MC conformation, which allowed arginine to mediate electrostatic interaction with the mineral. By contrast, due to the lack of arginine in MC-LA, complexation of Ca by only one carboxylate in MC-LA was required to favor Ca-bridging interaction with the mineral. Multiple water-bridged H-bonding interactions were also important in anchoring MCs at the mineral surface. Our modeling results offer molecular insights into the structural and chemical factors that can control the fate of MCs at water-mineral interfaces.
KW - Adsorption
KW - Algal toxins
KW - Environmental partitioning
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U2 - 10.1016/j.jcis.2016.07.016
DO - 10.1016/j.jcis.2016.07.016
M3 - Article
C2 - 27433998
AN - SCOPUS:84978272042
VL - 480
SP - 166
EP - 174
JO - Journal of Colloid and Interface Science
JF - Journal of Colloid and Interface Science
SN - 0021-9797
ER -