ABSTRACT
Ion mobility spectrometry (IMS) is a compact and sensitive trace gas analysis instrument that ionizes the sample into ions for detection. Typically, an ion gate is used to cut the continuous ion beam into ion packets for separation and detection. However, commonly used ion gates suffer from complex structures or low ion transmission rates, making the gateless IMS a viable alternative. In this study, an IMS based on a pulsed photoelectric effect ionization source was designed. The photoelectrons were generated by irradiating a photoelectric material with a back-illuminated pulsed xenon lamp. This allows for low-energy photoelectron generation and the production of simple reactant ions (O2-(H2O)n) and thus negative product ions. The photoelectron current generated by this ionization source was analyzed, which can reach an intensity of a few microamperes and can be converted into an ion signal exceeding 10 nA. The introduction of the pulsed photoelectric effect ionization source makes it possible to generate separate ion packets and complete ion injection when a constant electric field is maintained in the ionization region. And with an assisted pulsed electric field in the ionization region, the resolving power of the system can be effectively improved to 1.85 times that of the constant electric field. The IMS developed in this study was used for the detection of common volatile hazardous chemicals, yielding effective results. The detection limit for phenol was below 1 ppb, and the dynamic response range exceeded 1 order of magnitude, which implies the potential applications of this IMS to detect substances with high electron affinity, such as explosives detection in public safety.
ABSTRACT
The pandemic of COVID-19 challenges the global health system and raises our concerns on the next waves of other emerging infectious diseases. Considering the lessons from the failure of world's pandemic warning system against COVID-19, many scientists and politicians have mentioned different strategies to improve global biodefense system, among which Sheet, Surveillance, Strategy, Salvage and Shield (5S) are frequently discussed. Nevertheless, the current focus is mainly on the optimization and management of individual strategy, and there are limited attempts to combine the five strategies as an integral global biodefense system. Sheet represents the biosafety datasheet for biohazards in natural environment and human society, which helps our deeper understanding on the geographical pattern, transmission routes and infection mechanism of pathogens. Online surveillance and prognostication network is an environmental Surveillance tool for monitoring the outbreak of pandemic diseases and alarming the risks to take emergency actions, targeting aerosols, waters, soils and animals. Strategy is policies and legislations for social distancing, lockdown and personal protective equipment to block the spread of infectious diseases in communities. Clinical measures are Salvage on patients by innovating appropriate medicines and therapies. The ultimate defensive Shield is vaccine development to protect healthy crowds from infection. Fighting against COVID-19 and other emerging infectious diseases is a long rocky journey, requiring the common endeavors of scientists and politicians from all countries around the world. 5S in global biodefense system bring a ray of light to the current darkest and future road from environmental and geographical perspectives.
Subject(s)
COVID-19 , Pandemics , COVID-19/epidemiology , COVID-19/prevention & control , Communicable Disease Control , Humans , Pandemics/prevention & control , Public Health , SARS-CoV-2ABSTRACT
A cellulase producing strain was newly isolated from soil samples and identified as Paenibacillus sp. LLZ1. A novel aqueous-dimethyl sulfoxide (DMSO)/1-ethyl-3-methylimidazolium diethyl phosphate ([Emin]DEP)-cellulase system was designed and optimized. In the pretreatment, DMSO was found to be a low-cost substitute of up to 70% ionic liquid to enhance the cellulose dissolution. In the enzymatic saccharification, the optimum pH and temperature of the Paenibacillus sp. LLZ1 cellulase were identified as 6.0 and 40°C, respectively. Under the optimized reaction condition, the conversion of microcrystalline cellulose and bagasse cellulose increased by 39.3% and 37.6%, compared with unpretreated cellulose. Compared to current methods of saccharification, this new approach has several advantages including lower operating temperature, milder pH, and less usage of ionic liquid, indicating a marked progress in environmental friendly hydrolysis of biomass-based materials.
Subject(s)
Cellulase/chemistry , Cellulose/chemistry , Dimethyl Sulfoxide/chemistry , Paenibacillus/enzymology , Hydrolysis , Imidazoles/chemistry , Ionic Liquids/chemistry , Organophosphates/chemistry , Paenibacillus/isolation & purification , TemperatureABSTRACT
The study on the size distribution of water-stable aggregates (WSAs) in calcic kastanozem of Loess Plateau after 27 years fertilization showed that compared with those of natural soil, the contents of > 0.25 mm WSAs in 0-10 cm and 10-20 cm layers of cultivated soil decreased by 21.35% and 38.82%, respectively, and those of > or = 0.5 mm WSAs also had a decreasing trend, with the greatest decrement of > 5 mm and 5-2 mm WSAs. On the contrary, the contents of 0.5-0.25 mm WSAs in the two soil layers increased by 104.75% and 23.13%, respectively. All sizes WSAs had higher contents in 0-10 cm than in 10-20 cm soil layer. Fertilization had remarkable effects on the formation of WSAs. Under the applications of organic manure and its combination with chemical fertilizers, the content of 5-2 mm WSAs increased most, followed by that of > 5 mm WSAs. After applying organic manure, organic manure plus chemical fertilizers, and straws, the contents of larger sizes WSAs increased significantly, being beneficial to the improvement of soil structure. In all fertilization treatments, the mean mass diameter (MMD) of WSAs was larger in 0-10 cm than in 10-20 cm soil layer. Compared with non-fertilization, long-term fertilization increased the MMD of WSAs, and organic manure was superior to chemical fertilizers. The MMD of WSAs was positively correlated with the amount of > 0.25 mm WSAs.
Subject(s)
Fertilizers , Soil/analysis , Water Movements , Water/analysis , China , Crops, Agricultural/growth & development , Particle Size , Time FactorsABSTRACT
Murine N(1)-acetylated polyamine oxidase (mPAO) was treated with N,N'-bis-(prop-2-ynyl)-1,4-diaminobutane, a poor substrate and inhibitor for the enzyme, with K(m) and K(i) values in the millimolar range. Apparently, its oxidation produces prop-2-ynal, which reacts with amino acyl nucleophiles. Using a steady-state kinetic assay, four phases were identified, the first being the oxidation of the compound via Michealis-Menten-type kinetics. As prop-2-ynal accumulates, there is a biphasic reduction in the rate. This process leads to an mPAO form that is nearly inactive (fourth phase), but displays classical Michealis-Menten-type kinetics. The enzyme-bound flavin is not modified in this process. In contrast, micromolar concentrations of the MDL 72527 (N,N'-bis-[buta-2,3-dienyl]-1,4-diaminobutane) inhibited mPAO rapidly and completely. It inhibits by first binding tightly and apparently irreversibly, and then slowly converts to a species where the inhibitor is covalently bound to the N5-position of the flavin's isoalloxazine ring. The covalent adduct was identified as a flavocyanine.
Subject(s)
Enzyme Inhibitors/chemistry , Enzyme Inhibitors/pharmacology , Oxidoreductases Acting on CH-NH Group Donors/antagonists & inhibitors , Oxidoreductases Acting on CH-NH Group Donors/metabolism , Putrescine/analogs & derivatives , Putrescine/pharmacology , Acetylation , Animals , Flavins/chemistry , Flavins/metabolism , Kinetics , Mice , Molecular Structure , Oxidoreductases Acting on CH-NH Group Donors/chemistry , Putrescine/chemistry , Spectrum Analysis , Trichloroacetic Acid/pharmacology , Polyamine OxidaseABSTRACT
The research of soil organic matter (SOM) has been highlighted in soil science. In the past 50 years, new perspectives in the relationship between SOM and sustainability of atmosphere and biomosphere, and strong motivation to find a vivid index for soil quality variation induced the transformation in concepts and analytical techniques of SOM: the curiousness to humic substances faded off since they were dull to anthropogenic activities, and interests were focused on the light fraction of organic matter (LFOM), organic carbon associated with different mineral particles in size, particulate and intra-particulate organic matter (POM and iPOM), water soluble organic matter (WSOM), and microbial biomass carbon (MB-C). The relative fractionation procedures have been developed, and the main research activities on SOM are transformed from the products of microorganisms (humus) to the organic matter comprised in plant residues at their various decomposition stages and the organic carbon in microorganisms, since they are biologically active and immediately respond to soil cultivation and tillage, crop rotation, and fertilizer application, etc.
Subject(s)
Organic Chemicals/analysis , Soil/analysis , Carbon/analysis , Ecosystem , Fertilizers/analysis , Plant DevelopmentABSTRACT
According to the rotor size of Mandal RC5C and Stoks' law, a segregation procedure for soil particle size fractionation was designed, and used for the particle separation of Huangmian soil(Calcaric cambisols, FAO), Huihe soil (Haplic greyxems, FAO), and Helu soil(Calcic kastanozems, FAO) in the Loess Plateau of China, and of Orthic Brown Chernozem, and Orthic Black Chernozem in Canadian Prairie. The fractionation results of the 5 soils by using this procedure were in line with those of the standard pipette method.
Subject(s)
Soil/analysis , Centrifugation , Particle SizeABSTRACT
The aminoacyl sequences of three regions of pure bovine N1-acetylated polyamine oxidase (PAO) were obtained and used to search GenBankTM. This led to the cloning and sequencing of a complete coding cDNA for murine PAO (mPAO) and the 5'-truncated coding region of the bovine pao (bpao) gene. A search of GenBankTM indicated that mpao maps to murine chromosome 7 as seven exons. The translated amino acid sequences of mpao and bpao have a -Pro-Arg-Leu peroxisomal targeting signal at the extreme C termini. A beta-alpha-beta FAD-binding motif is present in the N-terminal portion of mPAO. This and several other regions of mPAO and bPAO are highly similar to corresponding sections of other flavoprotein amine oxidases, although the overall identity of aligned sequences indicates that PAO represents a new subfamily of flavoproteins. A fragment of mpao was used as a probe to establish the relative transcription levels of this gene in various mature murine tissues and murine embryonic and breast tissues at different developmental stages. An Escherichia coli expression system has been developed for manufacturing mPAO at a reasonable level. The mPAO so produced was purified to homogeneity and characterized. It was demonstrated definitively that PAO oxidizes N1-acetylspermine to spermidine and 3-acetamidopropanal and that it also oxidizes N1-acetylspermidine to putrescine and 3-acetamidopropanal. Thus, this is the classical polyamine oxidase (EC 1.5.3.11) that is defined as the enzyme that oxidizes these N1-acetylated polyamines on the exo-side of their N4-amino groups. This enzyme is distinguishable from the plant polyamine oxidase that oxidizes spermine on the endo-side of the N4-nitrogen. It differs also from mammalian spermine oxidase that oxidizes spermine (but not N1-acetylspermine or N1-acetylspermidine) at the exo-carbon of its N4-amino group. This report provides details of the biochemical, spectral, oxidation-reduction, and steady-state kinetic properties of pure mPAO.
Subject(s)
Gene Expression Regulation, Enzymologic , Oxidoreductases Acting on CH-NH Group Donors/genetics , Oxidoreductases Acting on CH-NH Group Donors/metabolism , Peroxisomes/enzymology , Spermidine/analogs & derivatives , Spermine/analogs & derivatives , Amino Acid Sequence , Animals , Base Sequence , Cattle , Cloning, Molecular , Escherichia coli , Flavoproteins/genetics , Kinetics , Mice , Molecular Sequence Data , Oxidation-Reduction , Oxidoreductases Acting on CH-NH Group Donors/isolation & purification , RNA, Messenger/analysis , Species Specificity , Spermidine/metabolism , Spermine/metabolism , Polyamine OxidaseABSTRACT
The dynamics of organic carbon in 3 soils of China Loess Plateau and Canada Prairies was significantly different: in China, the Huangmian soil (Calcaric Cambisols, FAO) lost 77% of total organic carbon (0-20 cm) within 5 years of cultivation, with a decrease rate of 2.11 tons C.hm-2.yr-1, which was mainly caused by water erosion and tillage erosion; and the Huihe soil (haplic greyxems, FAO) lost 70% of total organic carbon (0-20 cm layer) at the rate of 0.961.06 tons C.hm-2.yr-1, because of water erosion and decomposition over 42 years. However, the orthic brown chernozem in Canada lost 11% and 44% of the total soil organic carbon (0-20 cm layer) after 40 and 80 years of cultivation, respectively, with a corresponding rate of 0.17 tons C hm-2.yr-1 and 0.45 tons C hm-2.yr-1. The improvement in tillage and rotation system, which prevented soil from wind erosion and increased current residues into soil, was responsible for the decrease of the loss rate. The dynamics of soil light fraction organic carbon (LFOC) was similar to that of total organic carbon: Huangmian and Heilu soil lost 73% and 90% of LFOC, while orthic brown chernozem lost 74% and 70% of LFOC after breaked in 1920 and 1960, respectively. Among the test soils, Huangmian and Huihe soil had the fast SOC depletion due to the difference in the allocation of organic carbon between LFOC and HFOC.