Inhibition of cysteine protease papain by metal ions and polysulfide complexes,especially mercuric ion

Aim Cysteine proteases are closely associated with many human and non-human pathological processes and are potential targets for metal ions especially Hg^2＋ and the related species. In the present work, on the basis of to the general study on the effects of some metal ions on the activity of papain, a well-known representative of cysteine protease family, the inhibitory effects of Hg^2＋ and polysulfide complexes were studied. Results All the metal ions tested （Hg^2＋, Cu^2＋, Ag^＋, Au^3＋, Zn^2＋, Cd^2＋, Fe^3＋, Mn^2＋, Pb^2＋, Yb^3＋） inhibit the activity of papain anda good correlation between the inhibitory potency and softness-and-hardness was observed. Among the metals, Hg^2＋ was shown to be a potent inhibitor of papain with a Kiof 2 × 10^-7 mol·L^-1 among. Excessive amounts of glutathione and cysteine could reactivate the enzyme activity of papain deactivated by Hg^2＋. These evidences supported that Hg^2＋ might bind to the catalytic site of papain. Interestingly, Hg （Ⅱ） polysulfide complexes were for the first time found to inhibit papain with a Ki of 7 × 10^-6 mol·L^-1, whose potency is close to a well known mercury compound, thimerosal （Ki=2.7 × 10^-6）. In addition, Hg （Ⅱ） polysulfide complexes exhibit good permeability （ 1.9 × 10-5 cm· s^-1） to caco-2 monolayer. Conclusion These results suggested that mercury polysulfide complexes might be potential bioactive species in the interaction with cysteine proteases and other- SH-content proteins, providing a new clue to understand the mechanism of the toxicological and pharmacological actions of cinnabar and other insoluble mercury compounds.

1-Pyrenecarboxaldehyde thiosemicarbazone:A novel fluorescent molecular sensor towards mercury(Ⅱ) ion

A novel and simple fluorescent molecular sensor,1-pyrenecarboxaldehyde thiosemicarbazone（Hpytsc）,was synthesized.Its higher sensitivity and selectivity to mercury（Ⅱ） ion were studied through absorption and emission channels.The UV-vis spectra show that the increasing mercury（Ⅱ） ion concentrations result in the decreasing absorption intensity.The fluorescence monomer emission of Hpytsc is enhanced upon binding mercury（Ⅱ） ion,which should be due to the 1：1 complex formation between Hpytsc and metal ion.

Effects of 1,2,4-Trichlorobenzene and Mercury Ion Stress on Ca^2+ Fluxion and Protein Phosphorylation in Rice

The effects of 5 mg/L 1,2,4-trichlorobenzene （TCB） and 0.1 mmol/L mercury ion （Hg^2＋） stresses on Ca^2＋ fluxion and protein phosphorylation in rice seedlings were investigated by isotope exchange kinetics and in vitro phosphorylation assay. The Ca^2＋ absorption in rice leaves and Ca^2＋ transportation from roots to leaves were promoted significantly in response to Hg^2＋ and TCB treatments for 4-48 h. The Ca^2＋ absorption peaks presented in the leaves when the rice seedlings were exposed to Hg^2＋ for 8-12 h or to TCB for 12-24 h. Several Ca^2＋ absorption peaks presented in the roots during rice seedlings being exposed to Hg^2＋ and TCB, and the first Ca^2＋ absorption peak was at 8 h after being exposed to Hg^2＋ and TCB The result of isotope exchange kinetic analysis confirmed that short-term （8 h） Hg^2＋ and TCB stresses caused Ca^2＋ channels or pumps located on plasmalemma to open transiently. The phosphorylation assay showed that short-term TCB stress enhanced protein phosphorylation in rice roots （TCB treatment for 4-8 h） and leaves （TCB treatment for 4-24 h）, and short-term （4-8 h） Hg^2＋ stress also enhanced protein phosphorylation in rice leaves. The enhancement of protein phosphorylation in both roots and leaves corresponded with the first Ca^2＋ absorption peak, which confirmed that the enhancement of protein phosphorylation caused by TCB or Hg^2＋ stress might be partly triggered by the increases of cytosolic calcium. TCB treatment over 12 h inhibited protein phosphorylation in rice roots, which might be partly due to that TCB stress suppressed the protein kinase activity. Whereas, Hg^2＋ treatment inhibited protein phosphorylation in rice roots, and Hg^2＋ treatment over 12 h inhibited protein phosphorylation in rice leaves. This might be attributed to that not only the protein kinase activity, but also the expressions of phosphorylation proteins were restrained by Hg^2＋ stress.

Co-intensification of cyanide leaching gold by mercury ions and oxidant

The effects of mercury ions on gold cyanidation were studied. The results show that under low cyanide concentration, gold cyanide process is controlled by CN- transfer, while at higher cyanide concentration, there forms passivation on gold surface. Therefore, chemical oxidation of gold in cyanide solution of higher concentration is controlled by surface reaction. Small quantity of additions of mercury ions bring about great increases in anodic gold dissolution rate, decreases the passivation and reduces the equilibrium activated energy. In addition, they also markedly change the effect pattern of cyanide concentration. Mercury ions show positive effects on cathodic reduction of oxygen and raise the rate of electrochemical step of the cathodic reduction of oxygen. Addition of a certain amount of hydrogen peroxide is confirmed to be an effective way for intensification of cathodic process on gold electrode. Active potential range and current peak on anodic dissolution are enlarged when being co-intensified with Hg^2＋ and hydrogen peroxide. Co-intensifying effect may be obtained and gold from gold concentrates. gold leaching rate is considerably increased on cyanide leaching of

Thiol-functionalized MCM-48: an Effective Absorbent of Mercury Ions

Mercaptopropyl groups were grafted onto the pore walls of mesoporous molecular sieves MCM-48. The pore structures were characterized by powder X-ray diffraction and N2 adsorption analYSiS. Elemental analysis confirmed that the material with high organic moiety （2.2 mmol/g） had been obtained. ^13C MAS NMR verified the tethered organic groups. The thiol-functionalized MCM-48 showed effective capture of mercury ions, and all of the organic ligands were accessible for the binding of mercury ions.

Generation of Continuous-Wave 194 nm Laser for Mercury Ion Optical Frequency Standard

A 194-nm cw laser is an essential part in the mercury ion optical frequency standard. We report the generation of over 2mW continuous-wave radiation at 194nm in a beta barium borate crystal using a simple sum frequency mixing （SFM） system. One source beams at 718nm is resonantly enhanced with a cavity and the other at 266mn makes a single pass. Considering the walk-off effect in SFM, the source beam waists are designed to be elliptical, thus the conversion efficiency can be promoted. The 266-nm beam produced by frequency doubling of 532-nm laser is shaped close to the diffraction limit to achieve better mode matching.

Optimal Microwave Radiation Field Parameters for Mercury Ion Microwave Frequency Standards

We propose a method to determine the optimal power of the microwave resonance transition that simultaneously improves the signal-to-noise ratio and reduces line width based on saturation broadening theory and experiment. Saturation broadening spectra of the ground state hyperfine transition of trapped 199Hg＋ ions are measured and analyzed. The value of the optimal microwave power is obtained by using the proposed method and is verified. Rabi oscillations decay spectra of trapped 199Hg＋ ions are observed and the optimal microwave irradiation time for the maximum transition signal intensity is determined. This work will help to improve the short-term frequency stability of the mercury ion microwave frequency standard.

High extraction ability of 1,3-dialkynyl calixarene towards mercury(Ⅱ) ion

The reaction of 1,3-dipropyn-2-yloxycalix[4]arene with mercury（U） acetate could give mercury-containing alkynyl calixarene polymer. The extraction behavior of 1,3-dipropyn-2-yl-oxycalix[4]arene towards mercury（Ⅱ） ion was examined. When the mole ratio of Hg^2＋/calixarene was 1：1, the extractive percent can reach to 99.1%, and the extraction capacity was up to 431 mg/g. It could also decrease the Hg^2＋ concentration from 5 to 0.85 mg/L, which was only 17% of the national standard of effluent and satisfied the national standard of drinking water. The extraction process included chemical reaction.

Potentiometric Determination of Trace Amounts of Mercury (II) in Water Sample Using a New Modified Palm Shell Activated Carbon Paste Electrode Based on Kryptofix 5

A new modified palm shell activated carbon paste electrode based on 1,13-Bis(8-quinolyl)-1,4,7,10,13-pentaoxat-ride-cane ,8,8-(1,4,7,10,13-Pentaoxatridecylene)-diquinoline (Kryptofix?5) and plasticizing agent was prepared and studied as Hg2+ selective electrode. The best performance was observed with the electrode composition having the iono-phore-palm shell activated carbon-plasticizer composition 10%:50%:40% with Nernstian response over the concentration range of 1.0 × 10–8 - 1.0 × 10–2 M with a slope of 42 ± 1.5 mV per decade of concentration. The detection limit as determined from the calibration plot is 1.0 × 10–7 M. The proposed electrode shows good selectivity for Hg(II) with interfering ions. The response time of the electrode is fast (≤10 s), and can be used in the pH range of 3 - 11. The electrode was used to determine mercury in drinking water.

Adsorption of Hg(Ⅱ) from aqueous solution using thiourea functionalized chelating fiber

A fast and selective adsorbent for Hg（ll） from aqueous solutions using thiourea （TU） functionalized polypropylene fiber grafted acrylic acid （PP-g-AA）, PP-g-AA-TU fibers, was characterized by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The adsorption behavior of the functionalized chelating fibers for Hg（Ⅱ） was investigated by static adsorption experiments, and the effects of some essential factors on adsorption of Hg（Ⅱ） were examined, such as pH, initial concentration, adsorption time, coexisting cations, and temperature, The results showed that the adsorptive equilibrium could be achieved in 10 min, and the equilibrium adsorption quantity of PP-g-AA-TU fibers was 20 times that of PP-g-AA fibers. The PP-g-AA-TU fibers showed a very high adsorption rate and a good selectivity for Hg（Ⅱ） over a wide range of pH. The adsorption isotherm can be well described with Langmuir model, with the maximum adsorption capacity for Hg（Ⅱ） up to 52.04 mg.g-1 and the removal of Hg（Ⅱ） more than 97%. The kinetic data indicate that the adsorption process is best-fitted into the pseudo-second-order model.

Fabrication of Excitation-Independent Green Emissive Graphene Quantum Dots for Selective Detection of Hg^(2+) and Fluorescence Imaging of Biothiols in Living Cells

Nitrogen-doped graphene quantum dots( N-GQDs)exhibiting excitation-independent green fluorescence emission( 536 nm) was facilely synthesized. The as-prepared N-GQDs showed a highly selective fluorescence quenching response toward Hg2 + with a linear range of 0. 1-30. 0 μmol/L and detection limit of50 nmol/L. Based on the high affinity of biothiols( such as cysteine)toward Hg2 +, the quenched fluorescence of N-GQDs could be recovered upon addition of biothiols,and thereby a new fluorescence turn-on probe for cysteine detection was further developed. The linear range and detection limit for cysteine were found to be 0. 1-12. 5 μmol/L and 46 nmol/L,respectively. The present fluorescent probe worked well in a physiological pure water medium,allowing a fluorescence imaging of cysteine in living cells.

The Effect of Mix-Design and Corrosion Inhibitors on the Durability of Concrete

The deterioration of concrete over time is the result of various mechanical, physical, chemical and biological processes, with the corrosion of reinforcement being the most serious problem of durability of reinforced concrete structures. Over the last 50 years, a tremendous effort has been spent by the international scientific community with laboratory research and experimental field studies in order to increase the resistance of concrete over corrosion. This paper presents an experimental study of the corrosion behavior of 5 different concrete mix designs. The compositions were developed as per the latest concrete regulations and International Standards which are as follows: conventional concrete C30/37, conventional concrete with corrosion inhibitor as an additive, conventional concrete with surface spray sealant, fine aggregate concrete and self-compacting concrete. Their behavior against corrosion was determined via the following tests: water absorption test, water permeability test, mercury intrusion porosimetry, rapid chloride penetration test (RCPT), and accelerated carbonation test. The experimental results showed that the corrosion systems examined in the study provide anti-corrosion protection on steel rebars against corrosion comparing with the reference group. Also, an inversely proportional relationship of the water/cement ratio of a composition with its corrosion behavior was observed. Smaller w/c values (0.4 instead of 0.5) lead to better anti-corrosion resistance. In addition, an analogous relationship between the cement content of a composition and its corrosion behavior was observed.

Removal of Some Toxic Ions from Seawater and Wastewater by Sorption onto Natural, Synthetic Hydroxyapatite and Alginate-Hydroxyapatite Composite Nanoparticles: A Comparative Study

The main objective of this paper is to study the removal of Cadmium(II), Lead(II), Chromium(VI), and Mercury(II) ions by sorption onto different natural and synthetic nanoparticles. Special attention has been given to the application of fish bone in nanoform as a useful, inexpensive and eco-friendly alternative material. A comparison between natural hydroxyapatite (fish bone), synthetic hydroxyapatite nanoparticles (HAP) and alginate-hydroxyapatite composite (Alg/Hap) to assess their removal efficiencies to remediate the selected heavy metals has been done. Surface characterization by using different techniques has also been performed to understand the influence of surface characteristics of the adsorbent materials in the removal process. Different parameters (pH, contact time, mass dose and metal ion concentration) have been examined to identify the optimum conditions for remediation of different metals from polluted water. The potential applications of the biosorbents for removal and sorption of these metal ions from seawater and wastewater samples were also investigated and evaluated.

Synthesis of Carbon dots from Biomass Chenpi for the Detection of Hg^(2+)

Biomass-derived carbon dots(C-dots)are considered a very important carbon material in metal ion detection of their small environmental impact,simple preparation process,and relatively low cost.A green approach for synthesizing biomass-derived C-dots from Chenpi using a hydrothermal method without further processing is proposed in the present study.The as-synthesized C-dots show excellent fluorescence properties,superior resistance to UV irradiation photobleaching,and high photostability in salt-containing solutions.The C-dots were used in the form of label-free fluorescent probes for sensitively detecting Hg^(2+)selectively.The outcome relationship behaved linearly and was established based on a given range between 10–300 nM concentration,with a detection limit of 7.0 nM.This green strategy obtains a high C-dot quantum yield of 10.8%and satisfactory results in detecting Hg^(2+)in actual water samples.

Determination of Hypoxanthine in the Presence of Copper by Adsorptive Stripping Voltammetry

A stripping method for the determination of hypoxanthine in the presence of copper at the submicromolar concentration levels is described. The method is based on controlled adsorptive accumulation of hypoxanthine-copper at the thin-film mercury electrode followed by a fast linear scan voltammetric measurement of the surface species. Optimum experimental conditions were found to be the use of 1.0 × 10﹣3 mol·L﹣1 NaOH solution as electrolyte supporting, an accumulation potential of ﹣0.50 V and a linear scan rate of 200 mV·s﹣1. The response of hypoxanthine-copper is linear over the concentration ranges of 10 - 60 ppb. For an accumulation time of 30 minutes, the detection limit was found to be 250 ppt (1.8 × 10﹣9 mol·L﹣1). Adequate conditions for measuring the hypoxanthine in the presence of metal ions, xanthine, uric acid and other nitrogenated bases were also investigated. The utility of the method is demonstrated by the presence of hypoxanthine associated in ATP or ssDNA.

缺陷型巯基功能化MOF的制备及其重金属离子吸附性能

水中的重金属离子对人体伤害巨大,特别是Pb(Ⅱ)和Hg(Ⅱ)离子,因此需要去除Pb(Ⅱ)和Hg(Ⅱ)离子。通过调节合成过程中浓盐酸的用量,合成了具有不同缺陷程度的巯基功能化锆基金属有机框架(zirconium-based metal-organic frameworks, Zr-MOF)材料,简称UiO-66-(SH)_2,并将其用于液相中Pb(Ⅱ)和Hg(Ⅱ)离子的吸附去除。通过UiO-66-(SH)_2对Pb(Ⅱ)和Hg(Ⅱ)离子的吸附实验,发现随着制备过程中盐酸用量的增大,MOF的缺陷程度升高,其对Pb(Ⅱ)和Hg(Ⅱ)离子的吸附能力也有所增强。缺陷型UiO-66-(SH)_2对较低质量浓度的Pb(Ⅱ)(50 mg/L)和Hg(Ⅱ)(70 mg/L)离子的最大吸附量分别可达45和259 mg/g,且对这2种重金属离子具有较好的吸附选择性。经过3次循环吸附后,缺陷型UiO-66-(SH)_2对Pb(Ⅱ)和Hg(Ⅱ)离子的吸附能力没有明显下降,表明该材料在水中重金属离子去除应用上具有一定的潜力。

N掺杂的红色荧光纳米碳点检测汞离子

以对苯二胺和多巴胺为原料,通过一步水热法合成表面富含氨基基团的氮掺杂碳点(N-CDs),经过离心、过滤以及柱层析对所制备碳点进行提纯。采用高分辨透射电子显微镜和荧光对其进行表征。结果表明:该碳点粒径均一,具有良好的红色发光特性,且在最佳实验条件下,Hg2+对该碳点进行选择性荧光猝灭,其荧光猝灭程度与Hg2+浓度在0.1μM~2.1μM范围内呈现良好的线性关系,检测限为0.01μM。最后,该碳点成功用于实际水样中Hg2+的测定,加标回收率为95.0%~103.1%。

机器学习预测食品重金属检测中铜离子对汞离子荧光信号的干扰

目的:构建一个人工智能预测模型,在存在Cu^(2+)干扰的复杂食品检测环境下预测荧光探针对Hg^(2+)的选择性。方法:采用荧光探针技术结合7种先进经典的机器学习模型,预测分析存在Cu^(2+)干扰时探针对Hg^(2+)的选择性,并比较各模型的预测效果,选择最优模型。结果:基于分子二维描述符(molecular 2D descriptors,Mol2D)和极端梯度提升算法成功建立了在交叉验证和测试集中准确度为0.786和0.810的高效模型,在Cu^(2+)干扰下准确预判Hg^(2+)的探针选择性。结论:该模型通过选择性预判对Hg^(2+)荧光分子探针的设计进行改进,使Hg^(2+)荧光探针的设计更加高效可靠。

电场调控激光诱导石墨烯基重金属电化学检测装置的研制

为了快速、精准分析农田重金属,该文设计了一款基于施加电场与激光诱导石墨烯(laser-inducedgraphene,LIG)电极阵列的功能核酸比率电化学检测装置,用于农田中典型重金属离子Hg^(2+)、Pb^(2+)的分析。该装置主要包括电场施加模块与LIG电极阵列传感器两个部分,前者以AT89S52单片机作为主控芯片、DAC0832作为电压输出端口,设计单片机控制电压输出的电场施加装置,实现了可编程电压的稳定输出;后者则通过结合CO_(2)激光直写和环氧树脂转印技术,提出了LIG电极阵列的快速制备方法,并进一步构建了LIG基功能核酸比率电化学传感器。在检测过程中,通过调控施加电场的性质,该装置实现了Hg^(2+)、Pb^(2+)在传感器表面的快速特异性富集以及响应信号的稳定获取,其对Hg^(2+)、Pb^(2+)检测限分别低至8.5×10^(-12)mol/L(4.25×10^(-11)mg/L)和4.6×10^(-13)mol/L(2.22×10^(-12)mg/L),实现了农田灌溉用水中Hg^(2+)、Pb^(2+)的现场精准检测。该装置利用施加电场与LIG阵列传感器,实现了重金属离子的快速、精准、现场分析需求,对于农田环境重金属污染的监测及治理具有重要意义。

弃土基可控性低强度材料静态力学特性及孔隙分布特征

针对大规模的水利水电项目通常需要一定量的土地用于建设水库、水电站等基础设施,导致产生大量的工程弃土,利用开挖弃土制备土基可控性低强度材料,采用数字图像相关技术(digitalimage correlation,DIC)和声发射技术(acoustic emission,AE)监测试件破坏特征以及损伤演化机制,通过压汞法(mercury intrusion porosimetry,MIP)和扫描电镜(scanning electron microscopy,SEM)观察试件内部孔隙分布特征。结果表明,试件受压破坏后呈现完全破碎形态,裂缝在贯穿试件的过程中沿着最初方向持续发展,荷载到达峰值后裂缝发展主要以延伸为主直至破坏,试件内部拉伸破坏和剪切破坏并无明显区别。试件内部孔隙率较高,孔隙较大,整体黏结性较低,部分孔隙有水化产物充填,在加载过程中起连结作用。本研究为科学调控弃土基可控性低强度材料力学性能提供参考。