A facile method to construct cyclic α,α-difluoromethylenephosphonate—A novel cyclic phosphate mimic

A facile and efficient synthesis of cyclic α,α-difluoromethylenephosphonates by halogen-induced intramolecular cyclization of β-allenic α,α-difluoromethylenephosphonates is described. The protocol gives multi-substituted six-membered phosphonates with high regioselectivity, providing a new entry to the cyclic phosphate mimics which is still an unexplored but promising area.     

Peroxidase-like activity of mesoporous silica encapsulated Pt nanoparticle and its application in colorimetric immunoassay

Nanomaterial-based artificial enzymes have received great attention in recent year due to their potential application in immunoassay techniques. However, such potential is usually limited by poor dispersion stability or low catalytic activity induced by the capping agent essentially required in the synthesis. In an attempt to address these challenges, here, we studied the novel Pt nanoparticles (NPs) based peroxidase-like mimic by encapsulating Pt NP in mesoporous silica (Pt@mSiO₂ NPs). Compared with other nanomaterial-based artificial enzymes, the obtained Pt@mSiO₂ NPs not only exhibit high peroxidase-like activity but also have good dispersion stability in buffer saline solution when grafted with spacer PEG. Results show that when the thickness of silica shell is about 9 nm the resulting Pt@mSiO₂ NPs exhibit the catalytic activity similar to that of Pt NPs, which is approximately 26 times higher than that of Fe₃O₄ NPs (in terms of K_cat for H₂O₂). Due to the protection of silica shell, the subsequent surface modification with antibody has little effect on their catalytic activity. The analytical performance of this system in detecting hCG shows that after 5 min incubation the limit of detection can reach 10 ng mL⁻¹ and dynamic linear working range is 5–200 ng mL⁻¹. Our findings pave the way for design and development of novel artificial enzyme labeling.     

Hydrolysis of BNPP Catalyzed by the Crowned Schiff Base Co(II) Complex Containing Benzoaza‐15‐Crown‐5 in Micellar Solution

It has been reported that three aza crowned Schiff base cobalt (II) complexes were synthesized and characterized, and the metallomicelle made up of the cobalt (II) complexes and surfactants(Brij35, CTAB, LSS), as mimic hydrolytic metalloenzyme, was used in catalytic hydrolysis of bis(4‐nitrophenyl) phosphate (BNPP). The analysis of specific absorption spectrums of the hydrolytic reaction systems indicated that key intermediates made up of BNPP and Co (II) complexes are formed in the reaction process of BNPP catalytic hydrolysis. The mechanism of BNPP catalytic hydrolysis proposed is based on the analytic result of specific absorption spectra. Based on the mechanism proposed, a kinetic mathematical model for the calculation of the kinetic parameter of BNPP catalytic hydrolysis has been established. The acid effect of reaction system, structure effect of the complexes, effect of temperature and effect of micelles on the rate of BNPP hydrolysis catalyzed by the complexes have been discussed.     

Oxidative chlorination of 4-pentenols and other functionalized hydrocarbons

Substituted 4-pentenols undergo regio- and stereoselective chlorocyclization, when treated in solutions of dimethyl carbonate with chloride, a terminal oxidant, and a buffered proton source. Effective oxidants for liberating chlorine-like reactivity from chloride in the temperature range between 20 and 40 °C are tert-butyl hydroperoxide, activated by a titanium(IV) or a molybdenum(VI) ONO-chelate complex, and potassium monoperoxysulfate from the ternary salt 2KHSO₅·KHSO₄·K₂SO₄ (oxone^®). Substituents in the flexible part of the alkenol direct oxidative chlorocyclization 2,5-trans- and 2,4-cis-selectively. (E)-Configuration at the alkene translates anti-specifically into relative configuration of substituents at the β-chlorohydrin ether entity. A phenyl group bound to the terminal alkene carbon alters the inherent 5-exo-specificity for chlorocyclization of terminal 4-pentenols toward 6-endo-selectivity, as exemplified by synthesis of trans-3-chloro-2-phenyltetrahydropyran from (E)-5-phenyl-4-penten-1-ol in up to 74% yield. Competition kinetics show that 5-exo-chlorocyclization of 1-phenyl-4-penten-1-ol occurs at 40 °C 600 times faster than electrophilic aromatic chlorosubstitution of anisole. Prenyl-type alkenols undergo allylic chlorination with an ene-type selectivity, as exemplified in synthesis of a building block for the fragrance component rose oxide from citronellol.     

Effect of Catalase on Biocatalytic Synthesis of Pyruvate by Enzymes from Pseudomonas sp.

Pyruvate was produced from DL-lactate by a kind of green-chemical biocatalyst --cell-free extract from bacterial strain Pseudomonas sp. SM-6. Catalase in cell-free extract, whichcould stabilize the pyruvate formed by lactate oxidase, played an important role in pyruvatepreparation. The effect of catalase in conversion process was evaluated.     

模拟醛缩酶催化不对称直接Aldol反应新进展

对天然醛缩酶的作用机理进行了一般性阐述，在此基础上详细回顾了近几年对 两类醛缩酶的模拟催化不对称直接Aldol反应，并对其发展前景作了展望。     

模拟污水中氮、磷对水稻幼苗过氧化氢酶和乙醇酸氧化酶的影响

以水稻为材料，研究了不同浓度的模拟污水中Ｎ、Ｐ对幼苗过氧化氢酶（Ｃａｔａｌａｓｅ，ＣＡＴ，ＥＣ１．１１．１．６）、乙醇酸氧化酶（Ｇｌｅｃｏｌａｔｅｏｘｉｄａｓｅ，ＧＯ，ＥＣ１．３．３．１）、过氧化物酶（Ｐｅｒｏｘｉｄａｓｅ，ＰＯＤ，ＥＣ１．１１．１．７）和叶绿素含量的影响．结果表明：低浓度Ｎ、Ｐ（分别；在０～４．２８ｍｍｏｌ·Ｌ－１、０～０．２ｍｍｏｌ·Ｌ－１范围）可诱导ＣＡＴ活性增大，而后下降，Ｎ、Ｐ浓度分别超过８．５６ｍｍｏｌ·Ｌ－１和０．４ｍｍｏｌ·Ｌ－１后，活性又升高；ＰＯＤ的活性变化与ＣＡＴ变化很相似．Ｎ、Ｐ浓度分别在０～６．４２ｍｍｏｌ·Ｌ－１、０～０．３ｍｍｏｌ·Ｌ－１范围，ＧＯ活性随Ｎ、Ｐ浓度增高而活性下降，超过６．４２ｍｍｏｌ·Ｌ－１、０．３ｍｍｏｌ·Ｌ－１后，则随Ｎ、Ｐ浓度增大而增大．这可能是高浓度Ｎ、Ｐ可提高水稻的光呼吸的结果．另外，污水中Ｎ、Ｐ抑制叶绿素的合成，使叶绿素的含量降低；低浓度污水Ｎ、Ｐ促进根生长，高浓度Ｎ、Ｐ抑制根生长     

Tempo-activated manganese-based catalase mimics

Catalase-like activity of the TEMPO-activated (TEMPO: 2,2,6,6-tetramethyl-1-piperidinyloxyl) manganese(II) complex Mn(IndH)Cl₂·CH₃OH (IndH: 1,3-bis[(2′-pyridylimino)isoindoline] is reported. The title compound was a suitable catalyst for the disproportionation of H₂O₂ into water and dioxygen under ambient conditions. Kinetic measurements resulted in the third-order rate equation d[O₂]/dt = k[H₂O₂][Mn(IndH)Cl₂·CH₃OH][TEMPO].     

氮杂冠醚或吗啉基取代的单Schiff碱配合物催化α-吡啶甲酸对硝基苯酯水解

两种含5-取代苯并-10-氮杂-15-冠-5的Schiff碱锰(III)、钴(II)配合物( , )及其吗啉基取代的类似物( , ) 用于催化α-吡啶甲酸对硝基苯酯(PNPP)水解。探讨了氮杂冠醚Schiff 碱配合物催化PNPP水解的动力学和机理;提出了配合物催化PNPP水解的动力学模型;考察了配合物结构、反应温度、缓冲溶液pH值等对PNPP水解反应的影响。结果表明,在25℃条件下随着缓冲溶液pH值的增大,催化PNPP水解速率提高;含取代苯并-10-氮杂-15-冠-5的Schiff碱配合物表现出更高的催化活性。根据阿累尼乌斯公式和不同温度下的表观一级常数求出水解反应的表观活化能。     

Nanostructured FeS as a Mimic Peroxidase for Biocatalysis and Biosensing

Sheet‐like mimic enzyme : A novel nanostructure (see figure) of sheet‐like FeS with peroxidase‐like activity was synthesized as a mimic enzyme for the development of amperometric transducers and biocatalysts.