Control Method of Cold and Hot Shock Test of Sensors in Medium.

In order to meet the latest requirements for sensor quality test in the industry, the sample sensor needs to be placed in the medium for the cold and hot shock test. However, the existing environmental test chamber cannot effectively control the temperature of the sample in the medium. This paper designs a control method based on the support vector machine (SVM) classification algorithm and K-means clustering combined with neural network correction. When testing sensors in a medium, the clustering SVM classification algorithm is used to distribute the control voltage corresponding to temperature conditions. At the same time, the neural network is used to constantly correct the temperature to reduce overshoot during the temperature-holding phase. Eventually, overheating or overcooling of the basket space indirectly controls the rapid rise or decrease in the temperature of the sensor in the medium. The test results show that this method can effectively control the temperature of the sensor in the medium to reach the target temperature within 15 min and stabilize when the target temperature is between 145 °C and -40 °C. The steady-state error is less than 0.31 °C in the high-temperature area and less than 0.39 °C in the low-temperature area, which well solves the dilemma of the current cold and hot shock test.

Deep Learning-Based Segmentation of Airway Morphology from Endobronchial Optical Coherence Tomography.

BACKGROUND: Manual measurement of endobronchial optical coherence tomography (EB-OCT) images means a heavy workload in the clinical practice, which can also introduce bias if the subjective opinions of doctors are involved. OBJECTIVE: We aim to develop a convolutional neural network (CNN)-based EB-OCT image analysis algorithm to automatically identify and measure EB-OCT parameters of airway morphology. METHODS: The ResUNet, MultiResUNet, and Siamese network were used for analyzing airway inner area (Ai), airway wall area (Aw), airway wall area percentage (Aw%), and airway bifurcate segmentation obtained from EB-OCT imaging, respectively. The accuracy of the automatic segmentations was verified by comparing with manual measurements. RESULTS: Thirty-three patients who were diagnosed with asthma (n = 13), chronic obstructive pulmonary disease (COPD, n = 13), and normal airway (n = 7) were enrolled. EB-OCT was performed in RB9 segment (lateral basal segment of the right lower lobe), and a total of 17,820 OCT images were collected for CNN training, validation, and testing. After training, the Ai, Aw, and airway bifurcate were readily identified in both normal airway and airways of asthma and COPD. The ResUNet and the MultiResUNet resulted in a mean dice similarity coefficient of 0.97 and 0.95 for Ai and Aw segmentation. The accuracy Siamese network in identifying airway bifurcate was 96.6%. Bland-Altman analysis indicated there was a negligible bias between manual and CNN measurements for Ai (bias = -0.02 to 0.01, 95% CI = -0.12 to 0.14) and Aw% (bias = -0.06 to 0.12, 95% CI = -1.98 to 2.14). CONCLUSION: EB-OCT imaging in conjunction with ResUNet, MultiResUNet, and Siamese network could automatically measure normal and diseased airway structure with an accurate performance.

[Advance in insect phototaxis and the development and application of colored sticky boards]. / æ˜†è™«è¶‹è‰²æ€§åŠè¯±è™«è‰²æ¿çš„ç ”ç©¶å’Œåº”ç”¨è¿›å±•.

The visual communication between insect and plant is one of the key sensory signal channels for the survival, reproduction and defense of insects. The colored sticky boards, which are developed based on insects positive phototaxis and as one of the effective green pest control measures, have been widely applied for monitoring, forecasting and mass-trapping of many diurnal agricultural and forestry insect pests. In addition, they could be used to attract beneficial insects to the target areas to prey on or parasitize harmful insects, and to aid in pollination. Here, we discussed the insect phototaxis theory and the "attract and kill" mechanism of colored sticky boards and reviewed the effects of color, shape, size, height, density, facing direction, working duration of the sticky boards, as well as plant morphological characters and insect physiological status on trapping efficacy. We summarized various application techniques of the color sticky boards on different target pest insects in tea plantations, vegetable fields and greenhouses, etc. We analyzed various application technologies of combining colored sticky boards with synthetic sex pheromone attractants and/or botanical attractants and their efficacy; then evaluated the pros and cons of using the colored sticky boards for pest control or monitoring. Accordingly, we provided suggestions for improvements and discussed the trapping efficacy assessment and cost-benefit analysis. Finally, we proposed the RD directions of next generation colored sticky boards, especially its combination with synthetic pheromones/kairomones as an important integrated pest management (IPM) measure, and the future of the colored sticky board industry.

Highly stable hole-conductor-free perovskite solar cells based upon ammonium chloride and a carbon electrode.

Organic-inorganic hybrid perovskite solar cells (PSCs) have become a research hotspot due to the impressive photovoltaic performance. The perovskite film plays an extremely important role in the light-to-electricity conversion, meanwhile, the stability of PSCs is also an important factor affecting the application of devices. Here we demonstrate a kind of stable PSCs by using simple solution-process in an air enviroment with about 45% relative humidity. Firstly, the NH4Cl was added to the perovskite precursor solution to adjust the kinetics of crystallization and growth of active layer, and then obtain high-quality CH3NH3PbI3 perovskite films. Hydrophobic carbon electrode was used to protect the perovskite active layers and further improve the stability of PSCs, which optimized the structure of the devices at the same time. We adjusted the amount of NH4Cl in the perovskite precursor solution (PbI2: CH3NH3I: NH4Cl = 1: 1: x (x = 0 ∼ 1), and investigated the effect of that on the properties of perovskite active layers and PSCs. The above results showed that the devices achieved fully covered perovskite thin films and improved the photovoltaic performance of PSCs when the NH4Cl additive was x  = 0.8. The short-circuit current density (Jsc), fill factor (FF) and power conversion efficiency (PCE) were significantly enhenced. Under the condition of ambient air and no encapsulation, the PSCs exhibited good stability after 576 h test, and the PCE was still about 96% of the initial efficiency.

Clinical characteristics of papillary thyroid microcarcinoma less than or equal to 5 mm / 中国医师进修杂志

Objective To summarize the clinical characteristics of papillary thyroid microcarcinoma with diameter ≤ 5 mm. Methods The clinical data of 259 papillary thyroid microcarcinoma patients who had underwent radical thyroidectomy from January 2015 to December 2017 were retrospectively analyzed. The patients were divided into 2 groups according to the preoperative tumor diameter: ＞5 mm group (88 cases) and ≤ 5 mm group (171 cases); then according to the lymph node metastasis, the 2 groups were divided into non-lymph node metastasis sub-group and lymph node metastasis sub-group. The reason of lymph node metastasis was analyzed. Results There were no statistical difference in gender composition, age and combined Hashimoto thyroiditis rate between ＞5 mm group and≤5 mm group (P＞0.05). The rates of T3-4 stage, N1a-1b stage and multifocal tumors in＞5 mm group were significantly higher than those in ≤ 5 mm group: 34.1% (30/88) vs. 18.7% (32/171), 45.5% (40/88) vs. 22.8% (39/171) and 39.8% (35/88) vs. 22.8% (39/171), and there were statistical differences (P＜0.05 or＜0.01). In＞5 mm group, lymph node metastasis sub-group had 40 cases, non-lymph node metastasis sub-group had 48 cases; the rate of T3-4 stage in lymph node metastasis sub-group was significantly higher than that in non-lymph node metastasis sub-group: 55.0% (22/40) vs. 16.7% (8/48), and there was statistical difference (P＜0.01). In≤5 mm group, lymph node metastasis sub-group had 39 cases, and non-lymph node metastasis sub-group had 132 cases; the rate of T3-4 stage in lymph node metastasis sub-group was significantly higher than that in non-lymph node metastasis sub-group:51.3% (20/39) vs. 9.1% (12/132), and there was statistical difference (P＜0.01). In＞5 mm group and≤5 mm group, there were no statistical difference in gender composition, age, combined Hashimoto thyroiditis rate and multifocal tumors rate between 2 sub-groups (P＞0.05). Conclusions The clinical behavior of papillary thyroid microcarcinoma with diameter ≤ 5 mm has a less aggressive nature compared to that＞5 mm. Tumor capsular invasion or extra thyroidal extension has a great influence on lymph node metastasis in thyroid papillary microcarcinoma of different diameter.

Research progress on the underlying mechanisms of plant defense enzymes in response to pest stress.

Plants respond to herbivory through a series of physiological and biochemical defense mechanisms to counter the stress of herbivorous pests, including the dramatic changes in activities of various defense enzymes. Here, we reviewed the recent research progress on the response mechanisms of six common plant defense enzymes, SOD, CAT, POD, PPO, LOX and PAL, to insect stress, and compared their similarities and disparities. We sorted out their interactive sequences in response to the insect stress and analyzed the changes of defense enzyme activities and their associations with defense enzyme genes after being attacked by pests. Finally, we discussed the key problems/challenges in this area and proposed the prospects for studying the mechanisms of plant defense enzymes.

Interactions between artemisinins and other antimalarial drugs in relation to the cofactor model--a unifying proposal for drug action.

Artemisinins are proposed to act in the malaria parasite cytosol by oxidizing dihydroflavin cofactors of redox-active flavoenzymes, and under aerobic conditions by inducing their autoxidation. Perturbation of redox homeostasis coupled with the generation of reactive oxygen species (ROS) ensues. Ascorbic acid-methylene blue (MB), N-benzyl-1,4-dihydronicotinamide (BNAH)-MB, BNAH-lumiflavine, BNAH-riboflavin (RF), and NADPH-FAD-E. coli flavin reductase (Fre) systems at pH 7.4 generate leucomethylene blue (LMB) and reduced flavins that are rapidly oxidized in situ by artemisinins. These oxidations are inhibited by the 4-aminoquinolines piperaquine (PPQ), chloroquine (CQ), and others. In contrast, the arylmethanols lumefantrine, mefloquine (MFQ), and quinine (QN) have little or no effect. Inhibition correlates with the antagonism exerted by 4-aminoquinolines on the antimalarial activities of MB, RF, and artemisinins. Lack of inhibition correlates with the additivity/synergism between the arylmethanols and artemisinins. We propose association via π complex formation between the 4-aminoquinolines and LMB or the dihydroflavins; this hinders hydride transfer from the reduced conjugates to the artemisinins. The arylmethanols have a decreased tendency to form π complexes, and so exert no effect. The parallel between chemical reactivity and antagonism or additivity/synergism draws attention to the mechanism of action of all drugs described herein. CQ and QN inhibit the formation of hemozoin in the parasite digestive vacuole (DV). The buildup of heme-Fe(III) results in an enhanced efflux from the DV into the cytosol. In addition, the lipophilic heme-Fe(III) complexes of CQ and QN that form in the DV are proposed to diffuse across the DV membrane. At the higher pH of the cytosol, the complexes decompose to liberate heme-Fe(III) . The quinoline or arylmethanol reenters the DV, and so transfers more heme-Fe(III) out of the DV. In this way, the 4-aminoquinolines and arylmethanols exert antimalarial activities by enhancing heme-Fe(III) and thence free Fe(III) concentrations in the cytosol. The iron species enter into redox cycles through reduction of Fe(III) to Fe(II) largely mediated by reduced flavin cofactors and likely also by NAD(P)H-Fre. Generation of ROS through oxidation of Fe(II) by oxygen will also result. The cytotoxicities of artemisinins are thereby reinforced by the iron. Other aspects of drug action are emphasized. In the cytosol or DV, association by π complex formation between pairs of lipophilic drugs must adversely influence the pharmacokinetics of each drug. This explains the antagonism between PPQ and MFQ, for example. The basis for the antimalarial activity of RF mirrors that of MB, wherein it participates in redox cycling that involves flavoenzymes or Fre, resulting in attrition of NAD(P)H. The generation of ROS by artemisinins and ensuing Fenton chemistry accommodate the ability of artemisinins to induce membrane damage and to affect the parasite SERCA PfATP6 Ca(2+) transporter. Thus, the effect exerted by artemisinins is more likely a downstream event involving ROS that will also be modulated by mutations in PfATP6. Such mutations attenuate, but cannot abrogate, antimalarial activities of artemisinins. Overall, parasite resistance to artemisinins arises through enhancement of antioxidant defense mechanisms.

A partial convergence in action of methylene blue and artemisinins: antagonism with chloroquine, a reversal with verapamil, and an insight into the antimalarial activity of chloroquine.

Artemisinins rapidly oxidize leucomethylene blue (LMB) to methylene blue (MB); they also oxidize dihydroflavins such as the reduced conjugates RFH2 of riboflavin (RF), and FADH2 of the cofactor flavin adenine dinucleotide (FAD), to the corresponding flavins. Like the artemisinins, MB oxidizes FADH2, but unlike artemisinins, it also oxidizes NAD(P)H. Like MB, artemisinins are implicated in the perturbation of redox balance in the malaria parasite by interfering with parasite flavoenzyme disulfide reductases. The oxidation of LMB by artemisinin is inhibited by chloroquine (CQ), an inhibition that is abruptly reversed by verapamil (VP). CQ also inhibits artemisinin-mediated oxidation of RFH2 generated from N-benzyl-1,4-dihydronicotinamide (BNAH)-RF, or FADH2 generated from NADPH or NADPH-Fre, an effect that is also modulated by verapamil. The inhibition likely proceeds by the association of LMB or dihydroflavin with CQ, possibly involving donor-acceptor or π complexes that hinder oxidation by artemisinin. VP competitively associates with CQ, liberating LMB or dihydroflavin from their respective CQ complexes. The observations explain the antagonism between CQ-MB and CQ-artemisinins in vitro, and are reconcilable with CQ perturbing intraparasitic redox homeostasis. They further suggest that a VP-CQ complex is a means by which VP reverses CQ resistance, wherein such a complex is not accessible to the putative CQ-resistance transporter (PfCRT).

Stabilization of the second oxyanion intermediate by 1,4-dihydroxy-2-naphthoyl-coenzyme A synthase of the menaquinone pathway: spectroscopic evidence of the involvement of a conserved aspartic acid.

1,4-Dihydroxy-2-naphthoyl-coenzyme A (DHNA-CoA) synthase, or MenB, catalyzes an intramolecular Claisen condensation involving two oxyanion intermediates in the biosynthetic pathway of menaquinone, an essential respiration electron transporter in many microorganisms. Here we report the finding that the DHNA-CoA product and its analogues bind and inhibit the synthase from Escherichia coli with significant ultraviolet--visible spectral changes, which are similar to the changes induced by deprotonation of the free inhibitors in a basic solution. Dissection of the structure--affinity relationships of the inhibitors identifies the hydroxyl groups at positions 1 (C1-OH) and 4 (C4-OH) of DHNA-CoA or their equivalents as the dominant and minor sites, respectively, for the enzyme--ligand interaction that polarizes or deprotonates the bound ligands to cause the observed spectral changes. In the meantime, spectroscopic studies with active site mutants indicate that C4-OH of the enzyme-bound DHNA-CoA interacts with conserved polar residues Arg-91, Tyr-97, and Tyr-258 likely through a hydrogen bonding network that also includes Ser-161. In addition, site-directed mutation of the conserved Asp-163 to alanine causes a complete loss of the ligand binding ability of the protein, suggesting that the Asp-163 side chain is most likely hydrogen-bonded to C1-OH of DHNA-CoA to provide the dominant polarizing effect. Moreover, this mutation also completely eliminates the enzyme activity, strongly supporting the possibility that the Asp-163 side chain provides a strong stabilizing hydrogen bond to the tetrahedral oxyanion, which takes a position similar to that of C1-OH of the enzyme-bound DHNA-CoA and is the second high-energy intermediate in the intracellular Claisen condensation reaction. Interestingly, both Arg-91 and Tyr-97 are located in a disordered loop forming part of the active site of all available DHNA-CoA synthase structures. Their involvement in the interaction with the small molecule ligands suggests that the disordered loop is folded in interaction with the substrates or reaction intermediates, supporting an induced-fit catalytic mechanism for the enzyme.

[Monopolization of honeydew sources by Crematogaster macaoensis and its effects on lac production].

From October 2008 to May 2010, an investigation was made in a lac plantation in Yayi region of Mojiang County, Yunnan Province, China, aimed to understand the behavior of the monopolization of honeydew sources by ant Crematogaster macaoensis, and its effects on the sex ratio, mortality, fecundity, and lac production of Yunnan lac insect Kerria yunnanensis. The results showed that C. macaoensis fed and monopolized the honeydews around the clock during the whole life cycle of K. yunnanensis on the stick-lac, and the average number of visiting C. macaoensis ranged from 16.8 +/- 2.3 to 39.3 +/- 10.0 per 10 cm length of the stick-lac. C. macaoensis constructed shelters to prevent other animals from visiting the lac insect. C. macaoensis monopolization reduced the lac production of individual K. yunnanensi significantly, but had no significant effects on the lac production of whole lac insect colony. In addition, C. macaoensis monopolization reduced the mortality of K. yunnanensis significantly, and increased the percentage of K. yunnanensis females and the adult female fecundity. It was concluded that ant monopolization of the lac insect honeydew seemed to be beneficial to the lac production by the Yunnan lac insect.

Reactions of antimalarial peroxides with each of leucomethylene blue and dihydroflavins: flavin reductase and the cofactor model exemplified.

Flavin adenine dinucleotide (FAD) is reduced by NADPH-E. coli flavin reductase (Fre) to FADH(2) in aqueous buffer at pH 7.4 under argon. Under the same conditions, FADH(2) in turn cleanly reduces the antimalarial drug methylene blue (MB) to leucomethylene blue. The latter is rapidly re-oxidized by artemisinins, thus supporting the proposal that MB exerts its antimalarial activity, and synergizes the antimalarial action of artemisinins, by interfering with redox cycling involving NADPH reduction of flavin cofactors in parasite flavin disulfide reductases. Direct treatment of the FADH(2) generated from NADPH-Fre-FAD by artemisinins and antimalaria-active tetraoxane and trioxolane structural analogues under physiological conditions at pH 7.4 results in rapid reduction of the artemisinins, and efficient conversion of the peroxide structural analogues into ketone products. Comparison of the relative rates of FADH(2) oxidation indicate optimal activity for the trioxolane. Therefore, the rate of intraparastic redox perturbation will be greatest for the trioxolane, and this may be significant in relation to its enhanced in vitro antimalarial activities. (1)H NMR spectroscopic studies using the BNAH-riboflavin (RF) model system indicate that the tetraoxane is capable of using both peroxide units in oxidizing the RFH(2) generated in situ. Use of the NADPH-Fre-FAD catalytic system in the presence of artemisinin or tetraoxane confirms that the latter, in contrast to artemisinin, consumes two reducing equivalents of NADPH. None of the processes described herein requires the presence of ferrous iron. Ferric iron, given its propensity to oxidize reduced flavin cofactors, may play a role in enhancing oxidative stress within the malaria parasite, without requiring interaction with artemisinins or peroxide analogues. The NADPH-Fre-FAD system serves as a convenient mimic of flavin disulfide reductases that maintain redox homeostasis in the malaria parasite.

A bicarbonate cofactor modulates 1,4-dihydroxy-2-naphthoyl-coenzyme a synthase in menaquinone biosynthesis of Escherichia coli.

1,4-Dihydroxy-2-naphthoyl coenzyme A (DHNA-CoA) synthase is a typical crotonase-fold protein catalyzing an intramolecular Claisen condensation in the menaquinone biosynthetic pathway. We have characterized this enzyme from Escherichia coli and found that it is activated by bicarbonate in a concentration-dependent manner. The bicarbonate binding site has been identified in the crystal structure of a virtually identical ortholog (96.8% sequence identity) from Salmonella typhimurium through comparison with a bicarbonate-insensitive orthologue. Kinetic properties of the enzyme and its site-directed mutants of the bicarbonate binding site indicate that the exogenous bicarbonate anion is essential to the enzyme activity. With this essential catalytic role, the simple bicarbonate anion is an enzyme cofactor, which is usually a small organic molecule derived from vitamins, a metal ion, or a metal-containing polyatomic anionic complex. This finding leads to classification of the DHNA-CoA synthases into two evolutionarily conserved subfamilies: type I enzymes that are bicarbonate-dependent and contain a conserved glycine at the bicarbonate binding site; and type II enzymes that are bicarbonate-independent and contain a conserved aspartate at the position similar to the enzyme-bound bicarbonate. In addition, the unique location of the enzyme-bound bicarbonate allows it to be proposed as a catalytic base responsible for abstraction of the α-proton of the thioester substrate in the enzymatic reaction, suggesting a unified catalytic mechanism for all DHNA-CoA synthases.

Structural change of the enterobactin synthetase in crowded solution and its relation to crowding-enhanced product specificity in nonribosomal enterobactin biosynthesis.

Significant conformational change is detected by circular dichroism and fluorimetry for the major component of the enterobactin synthetase in crowded solutions mimicking the intracellular environment. The structural change correlates well with the extent of the crowding-induced side product suppression in nonribosomal enterobactin synthesis. In contrast, protein-stabilizing solvophobic agents such as glycerol have no effect on the formation of side products, excluding crowding-induced protein stability as a cause for the observed enhancement of the product specificity of the synthetase. These results strongly support that macromolecular crowding is an indispensable physiological factor for normal functioning of the nonribosomal enterobactin synthetase by altering the active sites to increase its product specificity.

[Predictive value of endometrial receptivity and pregnancy outcome by hysteroscopy examination at the phase of implantation window in unexplained infertile women].

OBJECTIVE: To explore predictive value of endometrial receptivity and pregnancy outcome by hysteroscopy examination at the phase of implantation window in unexplained infertile women. METHODS: From Oct. 2007 to Mar. 2009, 93 unexplained infertile women underwent hysteroscopy examination at 7 approximately 9 days after a spontaneous ovulation in Family Planning Research Institute of Guangdong Province. According to the endometrial glandular openings and vascular shape, 79 cases without pathological endometrial changes were divided into 60 cases in good endometrium group and 19 cases in poor endometrium group. The following clinical parameters were analyzed and compared between two groups, including endometrial configuration, thickness, secretion, the development and number of pinopodes, vascular distribution, and the level of sex hormone, leukemia inhibitory factor (LIF) and glycodelin in the uterine flushing, and pregnancy outcome. RESULTS: (1) There was no statistical difference in the level of serum estrogen and progesterone at the phase of implantation window, which were (518 +/- 176) pmol/L, (40 +/- 20) nmol/L in good group and (513 +/- 244) pmol/L, (37 +/- 19) nmol/L in poor group (P < 0.05). The endometrium thickness at periovulatroy and implantation window days (1.06 +/- 0.10) cm/(1.16 +/- 0.08) cm in good group did not show significant difference with (0.93 +/- 0.12) cm/(1.02 +/- 0.10) cm in poor group (P > 0.05). The proportion of type A, B and C endometrium at periovulatory days were 63% (12/19), 37% (7/19) and 0 (0/19) in good group and 23% (14/60), 77% (46/60) and 0 (0/60) in poor group. When compared with those of type A or B between two groups respectively, it all showed statistical difference (P < 0.05). However, at phase of implantation window, endometrium configurations were all type B at both groups. (2) 90% (17/19) of women in good group and 7% (4/60) of women in poor group showed normal endometrial secretion function, which showed significant differences (P < 0.01). (3) The percentage of fully developed pinopodes and abundant pinopodes [84% (16/19) and 90% (17/19)] in good group were significantly higher than 42% (25/60) and 57% (34/60) in poor group (P < 0.05). (4) The level of CD(34) expression and microvessel density [MVD; (40.1 +/- 1.2) positive unit (PU) and (21.7 +/- 4.0)/high power field (HP)] in good group were significantly higher than (18.1 +/- 1.3) PU and (8.5 +/- 1.3)/HP in poor group (P < 0.01). (5) The level of LIF and glycodelin in uterine flushing [(72 +/- 54) ng/L and (196 +/- 20) microg/L] in good group were significantly higher than (15 +/- 16) ng/L and (116 +/- 26) microg/L in poor group (P < 0.05). (6) The rate of clinical pregnancy, spontaneous abortion and term delivery were 74% (14/19), 0 (0/14) and 100% (14/14) in good group and 23% (14/60), 14% (2/14) and 86% (12/14) in poor group, the rate of clinical pregnancy and term delivery in good group were significantly increased when compared with those in poor group (P < 0.01). CONCLUSIONS: Hysteroscopy examination at the phase of implantation window could reflect the development of glandular openings and vasculature. It is a preferable method to evaluate the endometrial receptivity and predict pregnancy outcome.

[Coexistence mechanism of ant community in lac plantation under habitat heterogeneity].

In order to reveal the coexistence mechanism of ant community in lac plantation, an investigation was made on the ant community composition and the ability of ant species in discovering and holding food resources in a lac plantation in Yayi Town of Mojiang County, Yunnan Province, with the relationships between ant body size and its ability of finding food under habitat heterogeneity probed. There were six dominant ant species in the plantation, i. e., Tetraponera allaborans (Walker), Crematogaster macaoensis Wheeler, Crematogasterferrarii Emery, Dolichoderus thoracicus (Smith), Polyrhachis proxima Roger, and Camponotus parius Emery. The hind leg length (y) of the six ant species increased allometrically with their head width (x), and the regression equation was y = 0.56 + 1.02x + 5.97x2 - 10.85x3. Different ant species had significant differences in their actual and relative frequency in discovering food resources in different habitats, but habitat type had no significant effects on the actual frequency in holding food resources by the ant species. The ant species with bigger head width and bigger body size index could discover more food resources in simple habitat. In contrast, the ant species with smaller head width, shorter hind leg length, and smaller body size index could discover more food resources in complex habitat. The heterogeneity of habitat caused the coexistence of ants: the smaller ant species lived in complex habitat, while the larger ones lived in simple habitat. In addition, numerically dominant ant species were unable to possess all resources, and thereby, could provide the opportunity to other ant species for resources acquisition, making the species coexistence come true.

Enzyme-instructed molecular self-assembly confers nanofibers and a supramolecular hydrogel of taxol derivative.

By covalently connecting taxol with a motif that is prone to self-assemble, we successfully generate the precursor (5a), the hydrogelator (5b), and hydrogel of a taxol derivative without compromising the cytotoxic activity of the taxol. This approach promises a general method to create nanofibers of therapeutic molecules that have a dual role, as both the delivery vehicle and the drug itself.

Preferential hydrolysis of aberrant intermediates by the type II thioesterase in Escherichia coli nonribosomal enterobactin synthesis: substrate specificities and mutagenic studies on the active-site residues.

The type II thioesterase EntH is a hotdog fold protein required for optimal nonribosomal biosynthesis of enterobactin in Escherichia coli. Its proposed proofreading activity in the biosynthesis is confirmed by its efficient restoration of enterobactin synthesis blocked in vitro by analogs of the cognate precursor 2,3-dihydroxybenzoate. Steady-state kinetic studies show that EntH recognizes the phosphopantetheine group and the pattern of hydroxylation in the aryl moiety of its thioester substrates. Remarkably, it is able to distinguish aberrant intermediates from the normal one in the enterobactin assembly line by demonstrating at least 10-fold higher catalytic efficiency toward thioesters derived from aberrant aryl precursors without a para-hydroxyl group, such as salicylate. By structural comparison and site-directed mutagenesis, the thioesterase is found to possess an active site closely resembling that of the 4-hydroxybenzoyl-CoA thioesterase from Arthrobacter sp. strain SU and to involve an acidic residue (glutamate-63) as the catalytic base or nucleophile like all other hotdog thioesterases. In addition, the EntH specificities toward the substrate hydroxylation pattern are found to depend on the active-site histidine-54, threonine-64, serine-67, and methionine-68 with the selectivity significantly reduced or even reversed when they are individually replaced by alanine. These residues are likely responsible for differential interaction of the enzyme with the substrates which leads to distinction between the normal and aberrant precursors in the enterobactin assembly line. These results show that the type II thioesterase evolves its distinctive ability to recognize the aberrant intermediates from the versatile catalytic platform of hotdog proteins and suggests an active search mechanism for type II thioesterases in nonribosomal peptide synthesis.