A membraneless starch/O2 biofuel cell based on bacterial surface regulable displayed sequential enzymes of glucoamylase and glucose dehydrogenase.

Enzymatic biofuel cells (EBFCs) provide a new strategy to enable direct biomass-to-electricity conversion, posing considerable demand on sequential enzymes. However, artificial blend of multi-enzyme systems often suffer biocatalytic inefficiency due to the rambling mixture of catalytic units. In an attempt to construct a high-performance starch/O2 EBFC, herein we prepared a starch-oxidizing bioanode based on displaying a sequential enzyme system of glucoamylase (GA) and glucose dehydrogenase (GDH) on E.coli cell surfaces in a precise way using cohesin-dockerin interactions. The enzyme stoichiometry was optimized, with GA&GDH (3:1)-E.coli exhibiting the highest catalytic reaction rate. The bioanode employed polymerized methylene blue (polyMB) to collect electrons from the oxidation of NADH into NAD+, which jointly oxidized starch together with co-displayed GA and GDH. The bioanode was oxygen-insensitive, which can be combined with a laccase based biocathode, resulting in a membranless starch/O2 EBFC in a non-compartmentalized configuration. The optimal EBFC exhibited an open-circuit voltage (OCV) of 0.74 V, a maximum power density of 30.1 ± 2.8 µW cm-2, and good operational stability.

Investigation of Notch-Induced Precise Splitting of Different Bar Materials under High-Speed Load.

A notch-induced high-speed splitting method was developed for high-quality cropping of metal bars using a new type of electric-pneumatic counter hammer. Theoretical equations and FE models were established to reveal the crack initiation and fracture mode. Comparative tests were conducted for notched and unnotched bars of four types of steels, i.e., AISI 1020, 1045, 52100, and 304, and the section quality and microfracture mechanism were further investigated. The results show that damage initiates at the bilateral notch tips with peak equivalent plastic strain, and propagates through the plane induced by the notch tip; the stress triaxiality varies as a quasi-sine curve, revealing that the material is subjected to pure shearing at the notch tip, and under compression at the adjacent region. High precision chamfered billets were obtained with roundness errors of 1.1-2.8%, bending deflections of 0.5-1.5mm, and angles of inclination of 0.7°-3.4°. Additionally, the notch effectively reduced the maximum impact force by 21.6-23.9%, splitting displacement by 7.6-18.6%, and impact energy by 27.8-39.1%. The crack initiation zone displayed quasi-parabolic shallow dimples due to shear stress, and the pinning effect was larger in AISI 52100 and 1045 steel; the final rupture zone was characterized by less elongated and quasi-equiaxial deeper dimples due to the combination of shear and normal stress.

Controllable Display of Sequential Enzymes on Yeast Surface with Enhanced Biocatalytic Activity toward Efficient Enzymatic Biofuel Cells.

A precisely localized enzyme cascade was constructed by integrating two sequential enzymes, glucoamylase (GA) and glucose oxidase (GOx), on a yeast cell surface through an a-agglutinin receptor as the anchoring motif with cohesin-dockerin interaction. The overall catalytic activities of the combinant strains were significantly dependent on the assembly method, enzyme molecular size, enzyme order, and enzyme stoichiometry. The combinant strain with GA-DocC initially bound scaffoldin prior to GOx-DocT exhibited a higher overall reaction rate. The highest overall reaction rate (29.28 ± 1.15 nmol H2O2 min-1mL-1) was achieved when GA/GOx ratio was 2:1 with enzyme order: yeast-GA-GOx-GA, 4-fold enhancement compared to free enzyme mixture. Further, the first example of starch/O2 enzymatic biofuel cells (EBFCs) using codisplayed GA/GOx based bioanodes were assembled, demonstrating excellent direct biomass-to-electricity conversion. The optimized EBFC registered an open-circuit voltage of 0.78 V and maximum power density (Pmax) of 36.1 ± 2.5 µW cm-2, significantly higher than the Pmax for other starch/O2 EBFCs reported so far. Therefore, this work highlights rational organization of sequential enzymes for enhanced biocatalytic activity and stability, which would find applications in biocatalysis, enzymatic biofuel cells, biosensing, and bioelectro-synthesis.

Sex Differences in Prodromal Symptoms and Individual Responses to Acute Coronary Syndrome.

BACKGROUND: Although researchers have shown that prodromal symptoms can predict acute coronary events, the ability of patients with acute coronary syndrome (ACS) to identify these symptoms in a timely manner is limited. OBJECTIVES: We aimed to assess prodromal symptoms in Chinese patients with ACS and their responses to symptoms by sex. DESIGN: This cross-sectional, multicenter study involved 5 teaching hospitals in China and included 806 patients admitted for ACS between June 2013 and February 2014. The McSweeney Acute and Prodromal Myocardial Infarction Symptom Survey (Chinese version) was used to gather data. RESULTS: Among 806 patients (including 483 women), 688 (85.4%) experienced at least 1 prodromal symptom before ACS onset. Using adjusted logistic regression models, we determined that women were significantly more likely than men to report back pain, between- or under-shoulder blade pain/discomfort, sleep disturbances, anxiousness, or heart racing. The prevalence of generalized chest pain and loss of appetite was higher among men than women. Only 41% of patients attributed their prodromal symptoms to the heart, and women were more likely than men to attribute prodromal symptoms to a heart attack. CONCLUSIONS: More than two-thirds of patients with ACS reported at least 1 prodromal symptom, with some significant sex differences. Most patients do not attribute their symptoms to an impending ACS event.

Gender difference of symptoms of acute coronary syndrome among Chinese patients: a cross-sectional study.

BACKGROUND: The incidence of acute coronary syndrome is increasing in China. OBJECTIVE: To investigate gender differences in Chinese patients' acute coronary syndrome symptoms, attribution of symptoms and reasons for seeking medical service. METHODS: This was a cross-sectional, multicentre study. Acute coronary syndrome patients were recruited from five university hospitals located in four cities, between June 2013 and February 2014. Data were collected using the McSweeney acute and prodromal myocardial infarction symptom survey. RESULTS: A total of 806 patients with acute coronary syndrome (323 men, 483 women) participated in the study. Adjusted (diabetes, smoking, age) logistic regression models revealed that women were significantly more likely to have pain or discomfort in the: central high chest; back, between, or under the shoulder blades; neck or throat; or arms relative to men. Women were also more likely to have unusual fatigue, weakness, shortness of breath or difficulty breathing, or dizziness relative to men. Conversely, women were significantly less likely to have generalised chest pain relative to men. Gender difference in the attribution of symptoms was largely driven by women's attribution to having a heart attack more frequently than men. Finally, women were more often told by a friend to seek medical help or they knew their symptoms were different, while men more frequently sought medical help because their symptoms did not go away. CONCLUSIONS: There were gender differences in pain, discomfort and other symptoms. Both potential patients and healthcare providers need to be more aware of potential gender differences in acute coronary syndrome symptoms and decisions to seek care to ensure quick access.

Molecular Evidence for the Fitness of Cotton Aphid, Aphis gossypii in Response to Elevated CO2 From the Perspective of Feeding Behavior Analysis.

Rising atmospheric carbon dioxide (CO2) concentration is likely to influence insect-plant interactions. Aphid, as a typical phloem-feeding herbivorous insect, has shown consistently more positive responses in fitness to elevated CO2 concentrations than those seen in leaf-chewing insects. But, little is known about the mechanism of this performance. In this study, the foliar soluble constituents of cotton and the life history of the cotton aphid Aphis gossypii and its mean relative growth rate (MRGR) and feeding behavior were measured, as well as the relative transcript levels of target genes related appetite, salivary proteins, molting hormone (MH), and juvenile hormone, to investigate the fitness of A. gossypii in response to elevated CO2 (800 ppm vs. 400 ppm). The results indicated that elevated CO2 significantly stimulated the increase in concentrations of soluble proteins in the leaf and sucrose in seedlings. Significant increases in adult longevity, lifespan, fecundity, and MRGR of A. gossypii were found under elevated CO2 in contrast to ambient CO2. Furthermore, the feeding behavior of A. gossypii was significantly affected by elevated CO2, including significant shortening of the time of stylet penetration to phloem position and significant decrease in the mean frequency of xylem phase. It is presumed that the fitness of A. gossypii can be enhanced, resulting from the increases in nutrient sources and potential increase in the duration of phloem ingestion under elevated CO2 in contrast to ambient CO2. In addition, the qPCR results also demonstrated that the genes related to appetite and salivary proteins were significantly upregulated, whereas, the genes related to MH were significantly downregulated under elevated CO2 in contrast to ambient CO2, this is in accordance with the performance of A. gossypii in response to elevated CO2. In conclusion, rise in atmospheric CO2 concentration can enhance the fitness of A. gossypii by increasing their ingestion of higher quantity and higher quality of host plant tissues and by simultaneously upregulating the transcript expression of the genes related to appetite and salivary proteins, and then this may increase the control risk of A. gossypii under conditions of climate change in the future.

Microbial surface displayed enzymes based biofuel cell utilizing degradation products of lignocellulosic biomass for direct electrical energy.

In this work, a bacterial surface displaying enzyme based two-compartment biofuel cell for the direct electrical energy conversion from degradation products of lignocellulosic biomass is reported. Considering that the main degradation products of the lignocellulose are glucose and xylose, xylose dehydrogenase (XDH) displayed bacteria (XDH-bacteria) and glucose dehydrogenase (GDH) displayed bacteria (GDH-bacteria) were used as anode catalysts in anode chamber with methylene blue as electron transfer mediator. While the cathode chamber was constructed with laccase/multi-walled-carbon nanotube/glassy-carbon-electrode. XDH-bacteria exhibited 1.75 times higher catalytic efficiency than GDH-bacteria. This assembled enzymatic fuel cell exhibited a high open-circuit potential of 0.80 V, acceptable stability and energy conversion efficiency. Moreover, the maximum power density of the cell could reach 53 µW cm(-2) when fueled with degradation products of corn stalk. Thus, this finding holds great potential to directly convert degradation products of biomass into electrical energy.

Biofuel cell based self-powered sensing platform for L-cysteine detection.

L-cysteine (L-Cys) detection is of great importance because of its crucial roles in physiological and clinical diagnoses. In this study, a glucose/O2 biofuel cell (BFC) was assembled by using flavin adenine dinucleotide-dependent glucose dehydrogenase (FAD-GDH)-based bioanode and laccase-based biocathode. Interestingly, the open circuit potential (OCP) of the BFC could be inhibited by Cu(2+) and subsequently activated by L-Cys, by which a BFC-based self-powered sensing platform for the detection of L-Cys was proposed. The FAD-GDH activity can be inhibited by Cu(2+) and, in turn, subsequent reversible activation by L-Cys because of the binding preference of L-Cys toward Cu(2+) by forming the Cu-S bond. The preferential interaction between L-Cys and Cu(2+) facilitated Cu(2+) to remove from the surface of the bioanode, and thus, the OCP of the system could be turned on. Under optimized conditions, the OCP of the BFC was systematically increased upon the addition of the L-Cys. The OCP increment (ΔOCP) was linear with the concentration of L-Cys within 20 nM to 3 µM. The proposed sensor exhibited lower detection limit of 10 nM L-Cys (S/N = 3), which is significantly lower than those values for other methods reported so far. Other amino acids and glutathione did not affect L-Cys detection. Therefore, this developed approach is sensitive, facile, cost-effective, and environmental-friendly, and could be very promising for the reliable clinically detecting of L-Cys. This work would trigger the interest of developing BFCs based self-powered sensors for practical applications.

Systemicity of chlorantraniliprole in velvetleaf (Abutilon theophrasti).

The systemicity of chlorantraniliprole was investigated and evidence was collected for formulating strategies in controlling vegetable or rice pests. Systemicity of chlorantraniliprole was investigated through chlorantraniliprole application on velvetleaf (Abutilon theophrasti) leaves as well as through hydroponic experiments. The roots of velvetleaf were incubated in chlorantraniliprole solution with a concentration of 50 microg/mL; the concentrations of chlorantraniliprole in xylem above the solution parts were 3.14, 5.67, and 6.89 microg/g at 24, 48, and 72 h after treatment. When the roots were incubated in chlorantraniliprole solution with a concentration of 200 microg/mL, the concentrations of chlorantraniliprole in xylem above the solution reached 6.48, 8.76, and 10.55 microg/g at 24, 48, and 72 h after treatment. Chlorantraniliprole was not detected in the phloem above the solution after these two treatments. When chlorantraniliprole solution with a concentration of 100 microg/mL was applied on mature leaves, chlorantraniliprole was found in xylem above the mature leaves at concentrations of 0.55, 0.74, and 0.92 microg/g at 24, 48, and 72 h after the treatment. No chlorantraniliprole was detected in the leaves below the mature leaves or the phloem above them. When chlorantraniliprole solution with a concentration of 100 microg/mL was applied on apical leaves, no chlorantraniliprole was detected in the xylem or phloem below them. These results indicated that chlorantraniliprole can be transported through xylem only upward, but chlorantraniliprole has no phloem mobility in velvetleaf.

Determination of residual flubendiamide in the cabbage by QuEChERS-liquid chromatography-tandem mass spectrometry.

Flubendiamide, which belongs to the new chemical class of phthalic acid diamides, is widely used against lepidopteron pests in a variety of vegetable and rice pests. It provides superior plant protection against a broad range of economically important lepidopterous pests, including Spodoptera exigua and Plutella xylostella. A determination method of flubendiamide in the cabbage was established in this paper. Flubendiamide in the cabbage was extracted with acetonitrile and ultrasonic extraction, and was purified by QuEChERS and analyzed by LC-MS/MS (liquid chromatography-tandem mass spectrometry). The results indicated that the average recovery of flubendiamide in the cabbage was 81.27%-91.45%, the coefficient of variation was 1.79%-4.81%, and the lowest detection concentration was 0.3 µg/kg. The extraction of flubendiamide from the cabbage and its analysis was in accordance with the pesticide residue criterion, i.e., simple, rapid, accurate, reproducible, stable, separatory, and convenient. It identifies and quantifies trace-level flubendiamide residues in the cabbage extracts using LC-MS/MS in the ESI negative mode coupled with the QuEChERS method.