TY - JOUR
T1 - Biomedicine in the environment
T2 - sorption of the cyclotide kalata B2 to montmorillonite, goethite, and humic acid
AU - Ovesen, Rikke Gleerup
AU - Nielsen, John
AU - Hansen, Hans Chr. Bruun
PY - 2011/8
Y1 - 2011/8
N2 - Cyclotides are bioactive, stable mini-proteins produced in high amounts in Violaceae and Rubiaceae with promising pharmaceutical and agrochemical applications. Environmental issues must be addressed before large-scale plant cultivation of cyclotides for pharmaceutical or pesticidal purposes can commence. The objective of the present study was to investigate sorption of the cyclotide kalata B2 (kB2), because knowledge of cyclotide biogeochemistry will aid our understanding of environmental fate. The octanol-water partitioning coefficient was determined to be 2.8±0.6 (logKOW=0.4±0.1). Sorption of kB2 by montmorillonite, goethite, and humic acid was investigated at different concentrations and under varying acidity and reached equilibrium within minutes. The kB2 sorption at a solution concentration of 0.2mg/L to montmorillonite was high (120mg/g) compared to humic acid (0.60mg/g) and goethite (0.03mg/g). Kalata B2 intercalated the interlayer space of montmorillonite. The sorption isotherm for humic acid was linear up to a solution concentration of 0.8mg/L and concave for montmorillonite and goethite up to an equilibrium solution concentration of 1.5mg/L. Sorption to goethite was unaffected by pH, but sorption to montmorillonite and humic acid at pH near the isoelectric point (pI) was threefold the sorption when pH>the isoelectric point, suggesting that electrostatic interaction/repulsion between kB2 and sorbents play an important role. The strong sorption to montmorillonite reduces exposure to below toxic threshold values. In addition, the transport risk of soluble cyclotides is reduced, but particle-bound cyclotides may be transported to recipient aquatic sediments with the associated risk of adversely affecting sediment-dwelling organisms.
AB - Cyclotides are bioactive, stable mini-proteins produced in high amounts in Violaceae and Rubiaceae with promising pharmaceutical and agrochemical applications. Environmental issues must be addressed before large-scale plant cultivation of cyclotides for pharmaceutical or pesticidal purposes can commence. The objective of the present study was to investigate sorption of the cyclotide kalata B2 (kB2), because knowledge of cyclotide biogeochemistry will aid our understanding of environmental fate. The octanol-water partitioning coefficient was determined to be 2.8±0.6 (logKOW=0.4±0.1). Sorption of kB2 by montmorillonite, goethite, and humic acid was investigated at different concentrations and under varying acidity and reached equilibrium within minutes. The kB2 sorption at a solution concentration of 0.2mg/L to montmorillonite was high (120mg/g) compared to humic acid (0.60mg/g) and goethite (0.03mg/g). Kalata B2 intercalated the interlayer space of montmorillonite. The sorption isotherm for humic acid was linear up to a solution concentration of 0.8mg/L and concave for montmorillonite and goethite up to an equilibrium solution concentration of 1.5mg/L. Sorption to goethite was unaffected by pH, but sorption to montmorillonite and humic acid at pH near the isoelectric point (pI) was threefold the sorption when pH>the isoelectric point, suggesting that electrostatic interaction/repulsion between kB2 and sorbents play an important role. The strong sorption to montmorillonite reduces exposure to below toxic threshold values. In addition, the transport risk of soluble cyclotides is reduced, but particle-bound cyclotides may be transported to recipient aquatic sediments with the associated risk of adversely affecting sediment-dwelling organisms.
U2 - 10.1002/etc.579
DO - 10.1002/etc.579
M3 - Journal article
C2 - 21590795
SN - 0730-7268
VL - 30
SP - 1785
EP - 1792
JO - Environmental Toxicology and Chemistry
JF - Environmental Toxicology and Chemistry
IS - 8
ER -