8 research outputs found
Competitive Inhibition Mechanism of Acetylcholinesterase without Catalytic Active Site Interaction: Study on Functionalized C<sub>60</sub> Nanoparticles via in Vitro and in Silico Assays
Acetylcholinesterase
(AChE) activity regulation by chemical agents or, potentially, nanomaterials
is important for both toxicology and pharmacology. Competitive inhibition
via direct catalytic active sites (CAS) binding or noncompetitive
inhibition through interference with substrate and product entering
and exiting has been recognized previously as an AChE-inhibition mechanism
for bespoke nanomaterials. The competitive inhibition by peripheral
anionic site (PAS) interaction without CAS binding remains unexplored.
Here, we proposed and verified the occurrence of a presumed competitive
inhibition of AChE without CAS binding for hydrophobically functionalized
C<sub>60</sub> nanoparticles (NPs) by employing both experimental
and computational methods. The kinetic inhibition analysis distinguished
six competitive inhibitors, probably targeting the PAS, from the pristine
and hydrophilically modified C<sub>60</sub> NPs. A simple quantitative
nanostructureâactivity relationship (QNAR) model relating the
pocket accessible length of substituent to inhibition capacity was
then established to reveal how the geometry of the surface group decides
the NP difference in AChE inhibition. Molecular docking identified
the PAS as the potential binding site interacting with the NPs via
a T-shaped plug-in mode. Specifically, the fullerene core covered
the enzyme gorge as a lid through ÏâÏ stacking
with Tyr72 and Trp286 in the PAS, while the hydrophobic ligands on
the fullerene surface inserted into the AChE active site to provide
further stability for the complexes. The modeling predicted that inhibition
would be severely compromised by Tyr72 and Trp286 deletions, and the
subsequent site-directed mutagenesis experiments proved this prediction.
Our results demonstrate AChE competitive inhibition of NPs without
CAS participation to gain further understanding of both the neurotoxicity
and the curative effect of NPs
Spatiotemporal Distribution and Alpine Behavior of Short Chain Chlorinated Paraffins in Air at Shergyla Mountain and Lhasa on the Tibetan Plateau of China
Pristine
high-altitude mountains are ideal areas for studying the
potential mechanism behind the long-range transport and environmental
behavior of persistent organic pollutants in remote areas. Short chain
chlorinated paraffins (SCCPs) are the most complex halogenated contaminants
in the environment, and have attracted extensive worldwide interest
in recent years. In this study, the spatiotemporal concentrations
and distributions of SCCPs in air collected from Shergyla Mountain
(located in the southeast of the Tibetan Plateau) and Lhasa were investigated
during 2012â2015. Generally, the total SCCP levels at Shergyla
Mountain and Lhasa were between 130 and 1300 pg/m<sup>3</sup> and
1100â14440 pg/m<sup>3</sup>, respectively. C<sub>10</sub> and
C<sub>11</sub> components were the most abundant homologue groups,
indicating that lighter SCCP homologue groups are capable of relatively
long-range atmospheric transport. Relatively high but insignificant
atmospheric SCCP concentrations at Shergyla Mountain area and Lhasa
were observed from 2013 to 2015 compared with 2012. At Shergyla Mountain,
SCCP concentrations on the eastern and western slopes increased with
altitude, implying that âmountain cold-trappingâ might
occur for SCCPs. A back-trajectory model showed that SCCP sources
at Shergyla Mountain and Lhasa were primarily influenced by the tropical
monsoon from Southwest and South Asia
Influence of EâWaste Dismantling and Its Regulations: Temporal Trend, Spatial Distribution of Heavy Metals in Rice Grains, and Its Potential Health Risk
Enhanced
regulations, centralized dismantling processes, and sophisticated
recycling technologies have been implemented in some e-waste dismantling
areas in China with regard to environmental and economic aspects since
2005. In this study, rice grain samples were collected from 2006 to
2010 in an e-waste dismantling area to investigate the temporal trends
and spatial distribution of As, Cd, Cu, and Pb. Geometric means of
As, Cd, Cu, and Pb in rice samples from the e-waste dismantling area
were 111, 217, 4676, and 237 ng g<sup>â1</sup>, respectively.
Levels of Pb showed a significant decreasing trend during the sampling
period, whereas the other three elements remained relatively constant
or even increased. Concentrations of Cd, Cu, and Pb in the e-waste
dismantling area were significantly higher than those in the non-e-waste
dismantling area (<i>p</i> < 0.05), which showed a close
connection between e-waste dismantling activities and elevated Pb,
Cu, and Cd contents. Risk assessment for human via rice consumption
indicated that over 60% of the hazard quotient of Cd exceeded 1 in
the e-waste dismantling area. Our study implied that stricter implementation
of regulatory measures might lead to positive effects in controlling
the release of some heavy metals to the environment. However, environmental
behaviors differed with geochemical characteristics of individual
elements. Further remediation actions to reduce heavy metal pollution
to the surrounding environment might still be needed
Differential Accumulation and Elimination Behavior of Perfluoroalkyl Acid Isomers in Occupational Workers in a Manufactory in China
In
this study, serum and urine samples were collected from 36 occupational
workers in a fluorochemical manufacturing plant in China from 2008
to 2012 to evaluate the body burden and possible elimination of linear
and branched perfluoroalkyl acids (PFAAs). Indoor dust, total suspended
particles (TSP), diet, and drinking water samples were also collected
to trace the occupational exposure pathway to PFAA isomers. The geometric
mean concentrations of perfluorooctanesulfonate (PFOS), perfluorooctanoate
(PFOA), and perfluorohexanesulfonate (PFHxS) isomers in the serum
were 1386, 371, and 863 ng mL<sup>â1</sup>, respectively. The
linear isomer of PFOS, PFOA, and PFHxS was the most predominant PFAA
in the serum, with mean proportions of 63.3, 91.1, and 92.7% respectively,
which were higher than the proportions in urine. The most important
exposure routes to PFAA isomers in the occupational workers were considered
to be the intake of indoor dust and TSP. A renal clearance estimation
indicated that branched PFAA isomers had a higher renal clearance
rate than did the corresponding linear isomers. Molecular docking
modeling implied that linear PFOS (<i>n</i>-PFOS) had a
stronger interaction with human serum albumin (HSA) than branched
isomers did, which could decrease the proportion of <i>n</i>-PFOS in the blood of humans via the transport of HSA
Short Chain Chlorinated Paraffins in Mollusks from Coastal Waters in the Chinese Bohai Sea
As an extremely complex group of persistent organic pollutants
(POPs) candidates in the Stockholm Convention, short chain chlorinated
paraffins (SCCPs) have been of extensive concern in recent years.
In this study, nine bivalve and two gastropod species were collected
in 2009 to evaluate the spatial distributions and potential factors
influencing the bioaccumulation of SCCPs in mollusks in the Chinese
Bohai Sea. The concentrations of â SCCPs in the mollusks were
in the range 64.9â5510 ng/g (dry weight) with an average chlorine
content of 61.1%. C<sub>10</sub> and C<sub>11</sub> were the predominant
homologue groups of SCCPs, which accounted for about 29.7% and 34.9%
of â SCCPs, respectively. Six and seven chlorinated substituents
were the main congener groups. Mya arenaria (Mya), Mactra veneriformis (Mac),
and Crassostrea talienwhanensis (Oyster,
Ost) had higher average concentrations of SCCPs than other species,
implying that these bivalves could be used as sentinels to indicate
SCCPs contamination in this coastal region. A significant positive
linear relationship was found between SCCP concentrations and lipid
content of the mollusks, whereas the lipid-normalized SCCP concentrations
were negatively linear-related to the trophic levels (TL), which implied
that SCCPs did not show biomagnification in mollusks in this region
Remarkable Contamination of Short- and Medium-Chain Chlorinated Paraffins in Free-Range Chicken Eggs from Rural Tibetan Plateau
Rapid social-economic development introduces modern lifestyles
into rural areas, not only bringing numerous modern products but also
new pollutants, such as chlorinated paraffins (CPs). The rural Tibetan
Plateau has limited industrial activities and is a unique place to
investigate this issue. Herein we collected 90 free-range chicken
egg pool samples across the rural Tibetan Plateau to evaluate the
pollution status of CPs. Meanwhile, CPs in related soils, free-range
chicken eggs from Jiangxi, and farmed eggs from markets were also
analyzed. The median concentrations of SCCPs (159 ng gâ1 wet weight (ww)) and MCCPs (1390 ng gâ1 ww) in
Tibetan free-range chicken eggs were comparable to those from Jiangxi
(259 and 938 ng gâ1 ww) and significantly higher
than those in farmed eggs (22.0 and 81.7 ng gâ1 ww).
In the rural Tibetan Plateau, the median EDI of CPs via egg consumption
by adults and children were estimated to be 81.6 and 220.2 ng kgâ1 bw dayâ1 for SCCPs and 483.4 and
1291 ng kgâ1 bw dayâ1 for MCCPs,
respectively. MCCPs might pose potential health risks for both adults
and children in the worst scenario. Our study demonstrates that new
pollutants should not be ignored and need further attention in remote
rural areas
Tris(2,3-dibromopropyl) Isocyanurate, Hexabromocyclododecanes, and Polybrominated Diphenyl Ethers in Mollusks from Chinese Bohai Sea
A novel brominated flame retardant (BFR), trisÂ(2,3-dibromopropyl)
isocyanurate (TBC), as well as hexabromocyclododecanes (HBCDs) and
polybrominated diphenyl ethers (PBDEs), were analyzed in 11 species
of mollusks collected from nine coastal cities around the Chinese
Bohai Sea in 2009 and 2010. The detection frequencies were 100%, 99%,
and 77% for PBDEs, HBCDs, and TBC, respectively. Concentrations of
âHBCDs ranged from below detection limit (nd) to 28.8 ng g<sup>â1</sup> on a dry weight (dw) basis, followed by â<sub>12</sub>PBDE (0.01â20.4 ng g<sup>â1</sup> dw) and TBC
(ndâ12.1 ng g<sup>â1</sup> dw). Statistically significant
linear correlations were found among the three BFRs. Positive correlations
were found between BFRs concentrations and lipid content in mollusks.
The concentrations tend to decrease with increasing trophic levels
of the mollusks, implying trophic dilution rather than biomagnifications
of the BFRs in the aquatic food chains of the sampling area. Among
the 11 mollusks species, Mytilus edulis showed higher bioaccumulation capability than others and was therefore
considered to be an appropriate bioindicator of contamination by the
BFRs in the Chinese Bohai Sea, in agreement with its previous selection
for the biomonitoring of organochlorine pesticides (OCPs) and polychlorinated
biphenyls (PCBs). A dramatic decrease in PBDE concentrations in mollusks
of the area was found for the time period from 2003 to 2010, with
a half-life of only 2.3 ± 1.7 years, reflecting a rapid response
of mollusks to the change in pollution of the marine environment
Identification of Tetrabromobisphenol A Allyl Ether and Tetrabromobisphenol A 2,3-Dibromopropyl Ether in the Ambient Environment near a Manufacturing Site and in Mollusks at a Coastal Region
Tetrabromobisphenol A (TBBPA) is
one of the most widely used brominated
flame retardants (BFRs) and has been frequently detected in the environment
and biota. Recent studies have found that derivatives of TBBPA, such
as TBBPA bisÂ(allyl) ether (TBBPA BAE) and TBBPA bisÂ(2,3-dibromopropyl)
ether (TBBPA BDBPE) are present in various environmental compartments.
In this work, using liquid chromatography coupled with tandem mass
spectrometry (LCâMS/MS) and liquid chromatography coupled with
quadrupole time-of-flight mass spectrometry (LCâQ-TOF-MS),
TBBPA allyl ether (TBBPA AE) and TBBPA 2,3-dibromopropyl ether (TBBPA
DBPE) were identified in environmental samples and further confirmed
by synthesized standards. Soil, sediment, rice hull, and earthworm
samples collected near a BFR manufacturing plant were found to contain
these two compounds. In sediments, the concentrations of TBBPA AE
and TBBPA DBPE ranged from 1.0 to 346.6 ng/g of dry weight (dw) and
from 0.7 to 292.7 ng/g of dw, respectively. TBBPA AE and TBBPA DBPE
in earthworm and rice hull samples were similar to soil samples, which
ranged from below the method limit of detection (LOD, <0.002 ng/g
of dw) to 0.064 ng/g of dw and from below the LOD (<0.008 ng/g
of dw) to 0.58 ng/g of dw, respectively. Furthermore, mollusks collected
from the Chinese Bohai Sea were used as a bioindicator to investigate
the occurrence and distribution of these compounds in the coastal
environment. The detection frequencies of TBBPA AE and TBBPA DBPE
were 41 and 32%, respectively, and the concentrations ranged from
below LOD (<0.003 ng/g of dw) to 0.54 ng/g of dw, with an average
of 0.09 ng/g of dw, for TBBPA AE, and from below LOD (<0.008 ng/g
of dw) to 1.41 ng/g of dw, with an average of 0.15 ng/g of dw, for
TBBPA DBPE