36 research outputs found
Four Groups of New Aromatic Halogenated Disinfection Byproducts: Effect of Bromide Concentration on Their Formation and Speciation in Chlorinated Drinking Water
Bromide is naturally present in source waters worldwide.
Chlorination
of drinking water can generate a variety of chlorinated and brominated
disinfection byproducts (DBPs). Although substantial efforts have
been made to examine the effect of bromide concentration on the formation
and speciation of halogenated DBPs, almost all previous studies have
focused on trihalomethanes and haloacetic acids. Given that about
50% of total organic halogen formed in chlorination remains unknown,
it is still unclear how bromide concentration affects the formation
and speciation of the new/unknown halogenated DBPs. In this study,
chlorinated drinking water samples with different bromide concentrations
were prepared, and a novel approachî¸precursor ion scan using
ultra performance liquid chromatography/electrospray ionization-triple
quadrupole mass spectrometryî¸was adopted for the detection
and identification of polar halogenated DBPs in these water samples.
With this approach, 11 new putative aromatic halogenated DBPs were
identified, and they were classified into four groups: dihalo-4-hydroxybenzaldehydes,
dihalo-4-hydroxybenzoic acids, dihalo-salicylic acids, and trihalo-phenols.
A mechanism for the formation of the four groups of new aromatic halogenated
DBPs was proposed. It was found that increasing the bromide concentration
shifted the entire polar halogenated DBPs as well as the four groups
of new DBPs from being less brominated to being more brominated; these
new aromatic halogenated DBPs might be important intermediate DBPs
formed in drinking water chlorination. Moreover, the speciation of
the four groups of new DBPs was modeled: the speciation patterns of
the four groups of new DBPs well matched those determined from the
model equations, and the reactivity differences between HOBr and HOCl
in reactions forming the four groups of new DBPs were larger than
those in reactions forming trihalomethanes and haloacetic acids
Online Study on the Pyrolysis of Polypropylene over the HZSMâ5 Zeolite with Photoionization Time-of-Flight Mass Spectrometry
The production of hydrocarbons through
the pyrolysis of polyolefins
is a promising way of fuel recycling. In this work, online single-photon
ionization time-of-flight mass spectrometry (SPIâTOFMS) was
used to study both thermal and catalytic decompositions of polypropylene
(PP) in a tubular furnace. SPI produces few or no fragments of molecular
ions, making the identification and interpretation of complex pyrolysis
products in real time possible. The mass spectra at different reaction
temperatures and time-evolved profiles of selected species during
the pyrolysis processes were measured. The pyrolysis products can
be classified into three groups: alkenes, dienes, and aromatics. As
the coke precursors, aromatics mainly composed of benzene, toluene,
and xylene (BTX) were observed at a very low temperature of 300 °C
with the presence of HZSM-5, which cannot be detected for pure PP
until 700 °C, indicating that HZSM-5 can accelerate the coke
formation. Because of the secondary reactions, different tendencies
of product intensities were exhibited as the reaction temperature
increased. In addition, in comparison of the time-evolved profiles
of the alkenes and BTX under high temperatures, a two-stage catalytic
degradation process taking place on the external surface and the micropores
of HZSM-5 was verified. A degradation mechanism was also proposed
for the pyrolysis of PP with a low HZSM-5 content based on the time-evolved
profiles performed at a low temperature. This work demonstrates the
good performance of SPIâTOFMS for the online study of the polymer
pyrolysis as well as the evaluation of the catalyst
Binding States of ProteinâMetal Complexes in Cells
The
identification of endogenous proteins as well as their binding
to metal ions in living cells is determined by combining pulsed electrophoretic
separations with nanoelectrospray ionization followed by mass spectrometric
detection. This approach avoids problems resulting from the complicated
cellular environment. In this manner, we demonstrate the rapid identification
(300 ms or less) of intact proteins from living E.
coli cells including the complexation of calmodulin
with calcium ion. The latter showed different binding states from
those observed in in vitro studies. These observations also reveal
in vitro measurements do not necessarily represent the actual situation
in living cells. We conclude that the attempted in situ measurement
of intracellular proteins with minimal sampling processes should be
preferred
Data_Sheet_1_Detection of Alternaria solani with high accuracy and sensitivity during the latent period of potato early blight.docx
Early blight (EB) disease, caused mainly by Alternaria solani, is an economic threat to potato and tomato production worldwide. Thus, accurate and sensitive detection of the fungal pathogen of this disease in plants at the early infection stage is important for forecasting EB epidemics. In this study, we developed an RNA-based method that enables highly accurate and sensitive A. solani detection in a whole potato leaf at a single spore level based on quantitative real-time polymerase chain reaction (qPCR). We discovered jg1677, a highly expressed gene whose full-length coding sequence is very specific for A. solani, by analyzing A. solani transcripts isolated from enhanced high throughput transcriptome of infected potato leaves by A. solani and using the National Center for Biotechnology Informationâs basic local alignment search tool. The specificity of the primers derived from jg1677 was determined using 22 isolates of common potato pathogens, including seven Alternaria isolates. Detecting jg1677 transcripts with qPCR is 1,295 times more sensitive than detecting genomic DNA. In addition, the expression pattern of jg1677 at different infection stages was determined by qPCR. What is more, jg1677 was expressed relatively stable between 15 and 35°C in infected leaves, and its expression was virtually unaffected in isolated leaves left at room temperature for 24 h. Our work provides a much more sensitive and accurate method compared to conditional DNA-based ones, permitting a very early diagnosis of EB and lowering the risk of EB epidemics.</p
Forest plot from meta-analysis of ACE I/D polymorphism and restenosis risk after PTCA-stent.
<p>Forest plot from meta-analysis of ACE I/D polymorphism and restenosis risk after PTCA-stent.</p
Cysteine protects rabbit spermatozoa against reactive oxygen species-induced damages
<div><p>The process of cryopreservation results in over-production of reactive oxygen species, which is extremely detrimental to spermatozoa. The aim of this study was to investigate whether addition of cysteine to freezing extender would facilitate the cryosurvival of rabbit spermatozoa, and if so, how cysteine protects spermatozoa from cryodamages. Freshly ejaculated semen was diluted with Tris-citrate-glucose extender supplemented with different concentrations of cysteine. The motility, intact acrosomes, membrane integrity, mitochondrial potentials, 8-hydroxyguanosine level and sperm-zona pellucida binding capacity were examined. Furthermore, glutathione peroxidase (GPx) activity, glutathione content (GSH), and level of reactive oxygen species (ROS) and hydrogen peroxide of spermatozoa were analyzed. The values of motility, intact acrosomes, membrane integrity, mitochondrial potentials and sperm-zona pellucida binding capacity of the frozen-thawed spermatozoa in the treatment of cysteine were significantly higher than those of the control. Addition of cysteine to extenders improved the GPx activity and GSH content of spermatozoa, while lowered the ROS, DNA oxidative alterations and lipid peroxidation level, which makes spermatozoa avoid ROS to attack DNA, the plasma membrane and mitochondria. In conclusion, cysteine protects spermatozoa against ROS-induced damages during cryopreservation and post-thaw incubation. Addition of cysteine is recommended to facilitate the improvement of semen preservation for the rabbit breeding industry.</p></div
Boiling of Simulated Tap Water: Effect on Polar Brominated Disinfection Byproducts, Halogen Speciation, and Cytotoxicity
Tap water typically
contains numerous halogenated disinfection
byproducts (DBPs) as a result of disinfection, especially of chlorination.
Among halogenated DBPs, brominated ones are generally significantly
more toxic than their chlorinated analogues. In this study, with the
aid of ultra performance liquid chromatography/electrospray ionization-triple
quadrupole mass spectrometry by setting precursor ion scans of <i>m</i>/<i>z</i> 79/81, whole spectra of polar brominated
DBPs in simulated tap water samples without and with boiling were
revealed. Most polar brominated DBPs were thermally unstable and their
levels were substantially reduced after boiling via decarboxylation
or hydrolysis; the levels of a few aromatic brominated DBPs increased
after boiling through decarboxylation of their precursors. A novel
adsorption unit for volatile total organic halogen was designed, which
enabled the evaluation of halogen speciation and mass balances in
the simulated tap water samples during boiling. After boiling for
5 min, the overall level of brominated DBPs was reduced by 62.8%,
of which 39.8% was volatilized and 23.0% was converted to bromide;
the overall level of chlorinated DBPs was reduced by 61.1%, of which
44.4% was volatilized and 16.7% was converted to chloride; the overall
level of halogenated DBPs was reduced by 62.3%. The simulated tap
water sample without boiling was cytotoxic in a chronic (72 h) exposure
to mammalian cells; this cytotoxicity was reduced by 76.9% after boiling
for 5 min. The reduction in cytotoxicity corresponded with the reduction
in overall halogenated DBPs. Thus, boiling of tap water can be regarded
as a âdetoxificationâ process and may reduce human exposure
to halogenated DBPs through tap water ingestion
A New Group of Disinfection Byproducts in Drinking Water: Trihalo-hydroxy-cyclopentene-diones
We
report the detection, synthesis, preparative isolation, structure
characterization and identification, and formation of a new group
of drinking water disinfection byproducts (DBPs): trihalo-hydroxy-cyclopentene-diones (trihalo-HCDs).
With ultra performance liquid chromatography (UPLC)/electrospray ionization-triple quadruple mass spectrometry
analyses (full scans, multiple reaction monitoring, and product ion
scans) and high-resolution mass spectrometry analyses (full scans),
the new group of DBPs was identified with formulae and proposed with
structures. However, due to a lack of commercially available standard
compounds, structure identification of this new group of DBPs was
challenging. 2,4,6-Trihydroxybenzaldehyde was found to be a good precursor
for the synthesis of the tribromo species (<i>m</i>/<i>z</i> 345/347/349/351) in the new group of DBPs by reacting
with bromine at a 2,4,6-trihydroxybenzaldehyde-to-bromine molar ratio
of 1:8. With UPLC/photodiode array analysis (simultaneous 2-
and 3-dimensional operations), the new DBP was determined to have
a maximum UV absorption at the wavelength of 280 nm. Through isolation
with high performance liquid chromatography/UV-triggered collections
followed by lyophilization, the pure standard of the new DBP was obtained.
Characterized with Fourier transform infrared spectroscopy, the pure
standard of the new DBP was finally identified to be tribromo-HCD,
and thus the new group of DBPs was identified to be trihalo-HCDs.
On the basis of the disclosed structure, formation pathways of tribromo-HCD
through reactions of three different precursors and bromine were proposed
and partially verified. Moreover, increasing the bromide level in
source water shifted the formation of trihalo-HCDs from being more
chlorinated to being more brominated; with an increase in the contact
time from 1 h to 5 d, the formation of trihalo-HCDs kept increasing
in chloramination, whereas they kept decreasing in chlorination; with
an increase in the pH from 6.0 to 8.5, the formation of trihalo-HCDs was
decreased by âź80%. Notably, the concentrations of tribromo-HCD
in eight Chinese tap water samples were from below the detection limit
to 0.53 Îźg/L
Annexin VâConjugated Mixed Micelles as a Potential Drug Delivery System for Targeted Thrombolysis
To
alleviate the hemorrhagic side effect of thrombolysis therapy,
a thrombus targeted drug delivery system based on the specific affinity
of Annexin V to phosphatidylserine exposed on the membrane surface
of activated platelet was developed. The amphiphilic and biodegradable
biomaterial, polycaprolactone-<i>block</i>-polyÂ(2-(dimethylamino)Âethyl
methacrylate)-<i>block</i>-polyÂ(2-hydroxyethyl methacrylate)
(PCL-<i>b</i>-PDMAEMA-<i>b</i>-PHEMA (PCDH)) triblock
polymer, was synthesized via ring opening polymerization (ROP) and
atom transfer radical polymerization (ATRP) to use as the nanocarriers
of thrombolytic drug. In order to conjugate Annexin V to the polymer,
PCDH was modified by succinic anhydride via ring-opening reaction
to introduce the carboxyl group (PCDH-COOH). After preparation of
PCDH/PCDH-COOH (9/1, m/m) mixed micelles, Annexin V was coupled with
the micelles using carbodiimide chemistry. The blood clot lysis assay
in vitro confirmed that lumbrokinase-loaded targeted micelles (LKTM)
had stronger thrombolysis potency than free lumbrokinase (LK) and
LK-loaded nontargeted micelles (LKM, <i>P</i> < 0.05).
In vivo thrombolytic assay, multispectral, optoacoustic tomography
(MSOT) was used to assess the target ability of LKTM. The results
of MSOT images indicated the fluorescence intensity of the LKTM group
located in the blood clot position were significantly stronger than
the LKM group. A 5 mm of carotid artery containing blood clot was
cut out 24 h later after administration to assess the degree of thrombolysis.
The results of thrombolytic assay in vivo were consistent with the
assay in vitro, which the differences between LK, LKM, and LKTM groups
were both statistically significant. All the results of thrombolysis
assays above proved that the capacity of thrombolysis in the LKTM
group was optimal. It suggested that Annexin V-conjugated micelles
will be a potential drug delivery system for targeted thrombolysis
Facile Synthesis of a Highly Efficient, Halogen-Free, and Intumescent Flame Retardant for Epoxy Resins: Thermal Properties, Combustion Behaviors, and Flame-Retardant Mechanisms
A novel
branched polyÂ(phosphonamidate-phosphonate) (BPPAPO) oligomer
was synthesized from the polycondensation of phenylphosphonic dichloride
and triÂhydroxyÂmethylÂphosphine oxide followed by
end-capping with aniline in a one-pot synthesis. BPPAPO exhibited
excellent flame-retardant efficiency in epoxy resins (EP). With only
5.0 wt % loading, the EP composite reached UL-94 V-0 rating with a
limiting oxygen index (LOI) value of 35.5%. BPPAPO catalyzed the early
degradation of EP and promoted the formation of more char residue.
Glass transition temperatures were partially lowered. When 7.5 wt
% BPPAPO was incorporated, the peak heat release rate and total heat
release were decreased by 66.2% and 37.3%, respectively, with a delayed
ignition and the formation of a highly intumescent char residue. Combination
of gas-phase and condensed-phase flame-retardant mechanisms was verified