Effect of charge trapping species of cupric ions on the photocatalytic oxidation of resorcinol

The photocatalytic oxidation of resorcinol, a potent endocrine disrupting chemical, in oxygenated aqueous suspensions of pure and cupric ions modified Degussa P25 titanium dioxide has been investigated at pH 3.0 ± 0.5. The initial rate of photocatalytic oxidation of resorcinol increased until an optimum dissolved cupric ions concentration was reached at 1.04 mM. At the optimum concentration of cupric ions, the initial rate of photocatalytic mineralisation and degradation of resorcinol was improved by 400%. The observed beneficial effect of cupric ions on the initial rate of resorcinol oxidation could be attributed to the formation of complex and its participation in the photoredox cyclic reaction.Two of the initial oxidation intermediates detected were 1,2,3-trihydroxybenzene and 1,2,4-trihydroxybenzene. These intermediates were formed via hydroxylation of the aromatic ring of resorcinol. Evidences have revealed that 1,2,4-trihydroxybenzene interacted strongly with cupric ions forming copper(II)-trihydroxybenzoate complexes that possessed good adsorption onto TiO₂ surface. These dual-effects help to draw the metal ions closer to the photocatalyst surface and subsequently trigger the electron trapping mechanism by cupric ions. As a result, this improved the charge carriers’ separation. Furthermore, in the presence of oxygen, reoxidation of photoreduced cupric ions occurred and this eliminated the possibility of copper photodeposition, while inducing a photoredox cyclic reaction to regenerate copper species that may potentially act as co-catalyst for the oxidation of 1,2,4-trihydroxybenzene. In contrast, no obvious complex formation was seen between 1,2,3-trihydroxybenzene and cupric ions. This pointed to an intriguing finding which indicates that the positioning of functional group on benzene ring influences the role of cupric ions.     

Enzymatic hydrolysis of lysine diisocyanate based polyurethanes and segmented polyurethane ureas by various proteases

This work studies the enzymatic degradation of polyurethanes (PUs) and segmented polyurethane ureas (SPUUs) derived from lysine diisocyanate (LDI) by various proteases. Thiol proteases, such as papain, bromelain, and ficin, showed high activity on PUs. Protease K and chymotrypsin also hydrolyzed the PUs. For almost all SPUUs, papain showed high activity. For example, LDI/poly(caprolactone) diol (M_w = 1250)/ethylene diamine (2/1/1) was hydrolyzed to 43% under the same conditions. The water-soluble degradation products of a polyurethane, LDI/BD (1/1), and two model compounds treated with papain were studied with NMR and GPC analysis. From the results, it was evident that the pendant methyl ester group in LDI was rapidly hydrolyzed, followed by slow hydrolysis of urethane bonds in the backbone chain.     

应用基因组重排技术提高普那霉素产量

将普那霉素产生菌——始旋链霉菌ND-23的孢子和原生质体经紫外线诱变后获得高产突变菌株,其中高产突变株SP-S73的产量达到356 mg/L,比出发菌株提高了31%.在上述增产突变株中选取4株作为基因组重排的出发亲本,对它们进行了4轮基因组重排育种,筛选得到了高产重排菌株,其中1株重排菌株G-211的普那霉素产量为832 mg/L,比产量最高的亲本菌株提高了134%,比原始出发菌株ND-23(272 mg/L)提高了206%.通过研究高产菌株和出发菌株ND-23在5 L罐上的发酵过程,发现普那霉素产生菌的生物合成属于非生长耦合型;其高产菌株G-211在合成产物的时期对还原糖和氨基氮的消耗量均大于原始菌株ND-23,这些结果将为高产菌株发酵条件优化和发酵放大研究提供有价值的参考.     

Virtual screening of eighteen million compounds against dengue virus: Combined molecular docking and molecular dynamics simulations study

Dengue virus is a major issue of tropical and sub-tropical regions. Dengue virus has been the cause behind the major alarming epidemics in the history with mass causalities from the decades. Unavailability of on-shelf drugs for the prevention of further proliferation of virus inside the human body results in immense number of deaths each year. This issue necessitates the design of novel anti-dengue drug. The protease enzyme pathway is the critical target for drug design due to its significance in the replication, survival and other cellular activities of dengue virus. Therefore, approximately eighteen million compounds from the ZINC database have been virtually screened against nonstructural protein 3 (NS3). The incremental construction algorithm of Glide docking program has been used with its features high throughput virtual screening (HTVS), standard precision (SP), extra precision (XP) and in combination of Prime module, induced fit docking (IFD) approach has also been applied. Five top-ranked compounds were then selected from the IFD results with better predicted binding energies with the catalytic triad residues (His51, Asp75, and Ser135) that may act as potential inhibitors for the underlying target protease enzyme. The top-ranked compounds ZINC95518765, ZINC44921800, ZINC71917414, ZINC39500661, ZINC36681949 have shown the predicted binding energies of −7.55, −7.36, −8.04, −8.41, −9.18 kcal/mol, respectively, forming binding interactions with three catalytically important amino acids. Top-docking poses of compounds are then used in molecular dynamics (MD) simulations. In computational studies, our proposed compounds confirm promising results against all the four serotypes of dengue virus, strengthening the opportunity of these compounds to work as potential on-shelf drugs against dengue virus. Further experimentation on the proposed compounds can result in development of strong inhibitors.     

接种氧化亚氮(N2O)还原细菌YSQ030对复垦土壤N2O排放和氮循环关键功能基因的影响

复垦土地是重要的后备土地资源,但通常土壤结构差、有机质和养分含量低;增施有机肥是快速提升地力的关键途径,但会造成温室气体如氧化亚氮(N₂O)的大量排放.接种具有N₂O还原功能的植物根际促生菌(PGPR)不仅能够减少温室气体排放,还能促进作物生长.本研究以一株具有N₂O还原功能的PGPR反硝化无色杆菌(Achromobacter denitrificans) YSQ030为供试菌株,明确接种YSQ030对施用有机肥的复垦土壤N₂O排放和氮循环关键功能基因的影响.通过设置施用有机无机复混肥和羊粪有机肥的土壤微宇宙试验,利用气相色谱仪分析接种YSQ030后土壤N₂O排放通量,进一步计算累积排放量;在试验结束后分析土壤pH、EC(电导率)、硝态氮和铵态氮含量,并利用实时荧光定量PRC分析土壤硝化功能基因(AOA amoA和AOB amoA)和反硝化功能基因(nirS、nirK、nosZ Ⅰ 和nosZ Ⅱ)的丰度.结果显示,施用有机无机复混肥和羊粪有机肥的土壤中接种YSQ030明显减少复垦土壤N₂O排放,N₂O排放量最大减少分别达90.4％和30.6％.施用有机无机复混肥处理的N₂O排放量远高于施用羊粪有机肥处理,这可能是由于施用有机无机复混肥的土壤与施用羊粪有机肥的土壤相比,土壤中编码反硝化细菌N₂O还原酶基因nosZ Ⅰ 和非典型反硝化细菌N₂O还原酶基因nosZ Ⅱ 基因丰度较低.施用有机无机复混肥均显著降低土壤硝化和反硝化功能基因丰度,而施用羊粪有机肥对土壤硝化和反硝化功能基因丰度大多没有明显影响.本研究表明,接种YSQ030能够减少施用有机肥土壤的N₂O排放,将为复垦土壤地力提升和N₂O减排提供科学依据,也将为研发新型微生物肥料或生物有机肥提供核心菌种资源.     

Electrochemical generation of reactive nitrogen species—VIII. Anodic N,N-coupling of N-aminophthalimides

Anodic N,N-coupling of N-aminophthalimides (1) was investigated in dry acetonitrile by cyclic voltammetry and preparative electrolysis. The compound 1 showed mainly three anodic peaks in the voltammogram. Anodic oxidation of 1 at the first peak potential provided 1,4-diphthalyltetrazane (3) together with 1,4-diphthalyltetrazene (4) and phthalimide (5), whereas the oxidation at the second peak potential gave 4 and 5. It was found that 3 could be anodically converted into 4 in a high current efficiency and a reasonable yield. On the basis of the results, N,N-coupling mechanism was discussed.     

The influence of iron on proton nuclear magnetic resonance measurements of coals

The extent to which paramagnetic iron ions contained in coals and solid coal residues can affect the proton nuclear magnetic resonance (¹H n.m.r.) properties is investigated. It is demonstrated that these dispersed paramagnetic ions even in large concentrations do not have a significant quantitative effect on proton spin populations determined by high-power pulsed ¹H n.m.r. measurements. It is further shown how magnetic ordering of such ions, which may occur naturally or be established during pyrolysis from iron pre-existing in other forms, can result in significant proportion of the proton populations being ‘n.m.r. invisible’.     

Solubilisation of calcium and magnesium from the marine red algae Lithothamnion calcareum

Marine minerals are a potential source of calcium and magnesium for nutritional supplementation. This study analysed the solubilisation of calcium and magnesium from the skeletal remains of Lithothamnion calcareum. Scanning electron microscopy analysis demonstrated a nonporous microstructure. Spectrophotometric determination showed that the calcium and magnesium contents were 30.01 and 6.22% (w/w), respectively. Solubilisation of calcium and magnesium was highly pH dependent. The temperature‐dependent solubilisation of calcium fitted the shrinking core model. The apparent activation energy for calcium solubilisation was 28.6 kJ mol^?1. Inclusion of caseinophosphopeptides (CPPs), casein‐derived mineral binding peptides, during the solubilisation of calcium and magnesium appeared to decrease the extent of calcium solubilisation at pH 6.0 and 8.0. The results herein have implications for the choice of optimal pH conditions for the sustained release of calcium and magnesium from marine mineral sources.     

Adsorption of butanol from aqueous solution onto a new type of macroporous adsorption resin: Studies of adsorption isotherms and kinetics simulation

BACKGROUND: Owing to the rapid depletion of petroleum fuel, the production of bio‐butanol has attracted much attention. However, low butanol productivity severely limits its potential industrial application. It is important to establish an approach for recovering low‐concentration butanol from fermentation broth. Experiments were conducted using batch adsorption mode under different conditions of initial butanol concentration and temperature. Batch adsorption data were fitted to Langmuir and Freundlich isotherms and the macropore diffusion, pseudo‐first‐ and second‐order models for kinetic study. RESULTS: The maximum adsorption capacity of butanol onto KA‐I resin increase with increasing temperature, ranged from 139.836 to 304.397 mg g^?1. The equilibrium adsorption data were well fitted by the Langmuir isotherm. The adsorption kinetics was more accurately represented by the macropore diffusion model, which also clearly predicted the intraparticle distribution of the concentration. The effective pore diffusivity (D_p) was dependent upon temperature, but independent of initial butanol concentration, and was 0.251 × 10^?10, 0.73 × 10^?10, 1.32 × 10^?10 and 4.31 × 10^?10 m² s^?1 at 283.13, 293.13, 303.13 and 310.13 K, respectively. CONCLUSION: This work demonstrates that KA‐I resin is an efficient adsorbent for the removal of butanol from aqueous solutions and available for practical applications for future in situ product recovery of butanol from ABE fermentation broth. Copyright © 2012 Society of Chemical Industry     

Identification of novel allosteric modulator binding sites in NMDA receptors: A molecular modeling study

The dysfunction of N-methyl-d-Aspartate receptors (NMDARs), a subtype of glutamate receptors, is correlated with schizophrenia, stroke, and many other neuropathological disorders. However, not all NMDAR subtypes equally contribute towards these disorders. Since NMDARs composed of different GluN2 subunits (GluN2A-D) confer varied physiological properties and have different distributions in the brain, pharmacological agents that target NMDARs with specific GluN2 subunits have significant potential for therapeutic applications. In our previous research, we have identified a family of novel allosteric modulators that differentially potentiate and/or inhibit NMDARs of differing GluN2 subunit composition. To further elucidate their molecular mechanisms, in the present study, we have identified four potential binding sites for novel allosteric modulators by performing molecular modeling, docking, and in silico mutations. The molecular determinants of the modulator binding sites (MBS), analysis of particular MBS electrostatics, and the specific loss or gain of binding after mutations have revealed modulators that have strong potential affinities for specific MBS on given subunits and the role of key amino acids in either promoting or obstructing modulator binding. These findings will help design higher affinity GluN2 subunit-selective pharmaceuticals, which are currently unavailable to treat psychiatric and neurological disorders.