Partitioning of Arsenic (V) on Biomembrane
Le Quoc TUAN 1 , Tran Thi Thanh HUONG 2 , Pham Thi Anh HONG 3 , Tomonori KAWAKAMI 4 , Hiroshi UMAKOSHI 1 , Toshinori SHIMANOUCHI 1 , Ryoichi KUBOI 1*
1Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka 560-8531, JAPAN
2Faculty of Basic Science, Nong Lam University, Ho Chi Minh City, VIETNAM、,3University of Natural Sciences, Vietnam National University of Ho Chi Minh City, VIETNAM
4Toyama Prefectural University, 5180 Kurokawa, Imizu City, Toyama, 939-0398 JAPAN * msb@cheng.es.osaka-u.ac.jp
# Arsenic (As) is one of the most significant toxicants dispersed in the global environment. Humans can be exposed to As through the intake of air, food, and water.
# Some roles of biomembrane in As removal were specified but their mechanisms have been a little found out.
# The present research is aiming to determine the As partitioning on biomembrane when arsenic interacts with membranes.
Overview
Toxic Metals(Pb, Cd, Hg, As)
Damage To Antioxidant Defense System
Depletion Of Thiol Status
Reactive Oxygen Species (ROS)
Lipid Proteins DNA
Cell DeathFig.1 As Uptaken into Cell Fig.2 Toxicity of As
1. As Partitioning on Biomembrane and Its Response
2. As Partitioning on Model Biomembrane and Its Response
Fig. 4. Viability of algal cells in presence of arsenic (V) ions and arsenic adsorption on cell membrane.
0 20 40 60
0 50 100
0 20 40 60 1 10
Incubation Time, t [hr]
Relative Viability of Algae Cells, C [–]
0 mM
0.05 mM 0.1 mM
0.5 mM
kC 1 mM
ln (C0/C) [–]
t [hr]
Fig. 3 Variation of cell viability as a function of concentration of arsenic (V) and Fe (III)
Toxic Metals Induce Cell death, depending on Toxicant Concentration
300 400
0 200 400
Wavelength [nm]
F luo resc en c e [ -]
Control0.05mM
0.5mM 1.0mM 0.1mM Control
0.05mM
0.5mM 1.0mM 0.1mM
As Conc.
0.1mM 1mM
Control
As Conc.
0 0.5 1 1.5
50 100
Arsenic (V)
Iron (III)
Concentration of metals [mM]
N o rm al iz e d fl uor es c enc e i n tens it iv e [–]
Algal cell: 1010cell/l Proteos medium at 300C
10μm
0 0.5 1
40 60 80 100
0 0.02 0.04
0 0.2 0.4 0.6 0.8
Cell Viability [%]
Concentration of Arsenate [mM]
Kinetic Constant of Cell Death, kCD[hr–1]
Mode II Mode III
As Partitioning on Cell Membrane [mM]
1
stStep: Slight Decrease of Viability (can be Repaired)
2
ndStep: Significant Reduction in Viability (>0.5mM)
# Typical Toxicity of As # Relation with As Partitioning
Fig. 5 RP-HPLC analysis of arsenic substituted POPC. Incubation of POPC 5 mM with As 50 μM in 30
0C in phosphate buffer pH 7.4.
0 2 4 6 00 0.02 0.04 0.06
50 100 P1
P1
P2
P1 Absorbance [–] P2
Column: C18–STR ODS–M Flow Rate: 1.0 ml/min POPC [5m M]
POPC +50μM As (12hr)
POPC +50μM As (48hr)
Retention Time [min]
Percentage of P2 Peak (As–Substituted POPC) [%]
48 hr
12 hr
As Conc. [mM]
Fig. 6 Model membrane (Liposome) experiment: The release of calcein in different incubation time; 5 mM POPC/50 μM As (100/1 molar)
Strong interaction between As and model biomembrane results in the substitution of phosphate head by arsenic.
Membrane fluidity was Extremely
Enhanced under Toxic Stress. Membrane Structure was Activated by As.
Incubation time [hour]
0 10 20
0 200 400 600
F luor es c enc e i n tens it y [a .u]
Addition
100%
As(V)
Triton X-100 As
Calcein As As
Calcein As
Conclusion
¾High affinity of As for phospholipid molecule and liposome membrane results in As partitioning on biomembrane.
¾Bio-membrane can recruit As with high efficiency in three phases: (1) binding, (2) partitioning and (3) substitution.
¾Bio-membrane can be useful for removing toxicants from environment.
Reference
J. Chemophere 60, 1550-1554 (2005).
J. Med. Chem. 43, 4617-4628 (2000).
Σ
•JSPS/MEXT科研費•21th COE: 自然共生化学の創成(大阪大学)
•GCOE：生命環境化学(大阪大学)
•Membrane Stress Biotechnology研究会
•リポソーム基礎工学研究会
