SYNTHESIS OF POLYMERIC β-CYCLODEXTRIN SUPPORTED BY CROSSLINKED POLY(ACRYLAMIDE-co-VINYLAMINE)AND ITS CATALYSIS OF THE HYDROLYSIS OF p-NITROPHENYL ACETATE

Polymeric β-cyclodextrin (β-CD) supported by crosslinked poly(acrylamide-co-vinylamine) was synthesized as anartificial analog of hydrolytic enzyme and its catalysis of the hydrolysis of p-nitrophenyl acetate (p-NPA) was theninvestigated. The result showed that the polymer-supported β-CD could accelerate the hydrolytic reaction of p-NPA morequickly than β-CD itself and crosslinked poly(acrylamide-co-vinylamine) alone. The acceleration rate of the polymer-supported β-CD was about 10 times as fast as that of free β-CD in 0.01 mol/L phosphate buffer (pH 7.4) containing 32%DMSO at 37±0.1℃ when the molar amount of β-CD units in the polymer was equal to that of free β-CD in the experiments.The enhanced acceleration of thc polymer-supported β-CD should be ascribed to the cooperative contribution of theinclusion effect of β-CD ring and the nucleophilic effect of amino groups on the polymeric support.

Synthesis and Crystal Structure of N,N′-Bis(p-nitrophenyl)-2,2′-(p-phenylene-dioxy)diacetamide DMF Monohydrate

A new complex of N,N?-bis(p-nitrophenyl)-2,2?-(p-phenylene-dioxy) diacetamide DMF monohydrate, C25H25N5O9·H2O (Mr = 557.52), has been synthesized and its structure was determined by X-ray crystallography method. The crystal belongs to monoclinic system, space group P21/c with a = 7.2812, b = 25.5894, c = 14.3434 ?, β = 91.110(1)o, V = 2672.0(2) ?3, Dc = 1.386 g/cm3, F(000) = 1168, μ = 0.109 mm-1 and Z = 4. The final R = 0.0493 and wR = 0.1173 for 3389 observed reflections with I > 2σ(I). The asymmetric unit of the title complex consists of monomeric N,N?-bis(p-nitrophenyl)-2,2?-(p-phenyleneioxy)diacetamide 1, one DMF and one water molecule, which are incorporated during recrystallization. The molecules are linked into a three-dimensional network by π…π interactions as well as intermolecular interactions among DMF, water molecule and 1.

Chiral Phosphine Ligands Derived from Sugars 4.Crystal Structure of Methyl 4,6-O-Benzylidene-3-Deoxy-3-(Diphenylphosphino)-α-D-Altropyranoside (3-MBPA)

The crystal structure of the title compound 3--MBPA, C26H27O5P (Mr.= 450. 44 ). has been determined by single--crystal X-ray diffraction. The crystal ismonoclinic with space group P21, a= 9. 294(l), b= 7. 999(1), c= 15. 925(2) A,β=96. 17(5)°, V= 1176. 9 A 3, Dc=l. 271 g/cm3, F(000)=476, μ=12. 99 cm-1,Z=', Z=2, and final R = 0. 045 and Ru= 0. 057 for 1882 reflections (I≥3a(I) ). Structureanalysis revealed that the pyranose and 4, 6--O--benzylidene ring of the title compoundadopt a distorted chair conformation and the diphenylphosphino, OH and OMe groupsare in pseudo--axial position.

A New Voltammetric Enzyme Immunoassay System for the Detection of Alkaline Phosphatase

A new voltammetric enzyme immunoassay system was investigated based on p-nitrophenyl phosphate (PNPP) as the substrate for alkaline phosphatase (ALP). PNPP is enzymatically hydrolyzed and the product p-nitrophenol (PNP) is detected by differential pulse voltammetry (DPV), which can be oxidized at +1.02 V (vs. Ag/AgCl) on bare glass carbon electrode (GCE). The conditions for enzymatic reaction and electrochemical detection were studied. According to this method, ALP can be detected with a detection limit of 2.8102 mU/L and a linear range of 4.0102 ~ 1.0106 mU/L.

Reactivity of Schiff Base Manganese（Ill） Complexes with Different Pendants toward the Hydrolysis of p-Nitrophenyl Picolinate

This paper describes the catalytic performance of two manganese（III） complexes with mono-Schiff base ligands as artificial hydrolases towards the hydrolysis of p-nitrophenyl picolinate （PNPP）. Observations reveal that the one complex （ MnL22C1 ） containing morpholine pendants exhibits 1.2-1.7 fold kinetic advantage over the other one （MnL12C1） containing benzoaza-15-crown-5 group. Especially, optimum molecule structures using a Gaussian 03 software confirm that MnL2CI indeed possesses a relatively open linked site for the approaching of PNPP, result- ing in higher efficiency due to a convenient association between substrate （PNPP） and MnL2C1. In addition, the steric hindrance of two pendants, i.e., benzoaza-15-crown-5 and morpholine, may be a main influencing factor for tuning catalytic activities of the synthesized Mn（III） catalysts. Both Mn（III） catalysts used here were found to have fine tolerance to the operated temperature and pH. Related kinetic and thermodynamic analyses were also given to demonstrate their structure-activity relationships （SAR） of both catalysts used.

Monitoring the Hydrolysis of p-Nitrophenyl Acetate Catalyzed by Seryl-histidine with Electrospray Ionization Mass Spectrometry

The hydrolysis of p-nitrophenyl acetate (p-NPA) catalyzed by seryl-histidine or histidine has been monitored by electrospray ionization mass spectrometry in the presence of the internal calibration, 8-anilino-1-naphthalenesulfonic acid ammonium salt (ANS). The half-life of p-NPA in the presence of 10 mmol·L -1 seryl-histidine or histidine at 25 ℃ was 370 min and 70 min respectively. With the occurrence of acetyl seryl-histidine and acetyl histidine in the reaction, and the fact that p-NPA was stable in the presence of 10 mmol·L -1 serine, an imidazolysis mechanism has been proposed, which is in accordance with the reported work.

p-Nitrophenyl Picolinate Cleavage by Unsymmetrical Bis-Schiff Base Manganese（Ⅲ） and Cobalt（Ⅱ） Complexes with Aza-Crown Ether or Morpholino Pendants

The unsymmetrical bis-Schiff base manganese（III） and cobalt（II） complexes with either benzo-10-aza-crown ether pendants （MnL1Cl, MnLZCl） or morpholino pendant （MnL3Cl, CoL3） have been employed as models for hy- drolase by studying the kinetics of their hydrolysis reactions with p-nitrophenyl picolinate （PNPP）. A kinetic model of PNPP cleavage catalyzed by these complexes is proposed. The effects of complex structures and reaction temperature on the rate of PNPP hydrolysis have been examined. All four complexes exhibit high catalytic activity and the rate increases with pH under 25℃. The complexes of ligands containing a crown ether group exhibit higher catalytic activities than the non-crown analogues. The catalytic activity of the complexes follows the order Mn（III） 〉 Co（II） under the same ligands.

Role of Mononuclear Rare Earth Metal Complexes in Promoting the Hydrolysis of 2-Hydroxypropyl p-Nitrophenyl Phosphate

Two long-chain multidentate ligands： 2,9-di-（n-2＇,5＇,8＇-triazanonyl）-1,10-phenanthroline （L^1） and 2,9-di- （n-4＇,7＇,10＇-triazaundecyl）-1,10-phenanthroline （L^2） were synthesized. The hydrolytic kinetics of 2-hydroxypropyl p-nitrophenyl phosphate （HPNP） catalyzed by the complexes of L^1 or L^2 with La（Ⅲ） or Gd（Ⅲ） have been studied in aqueous solution at （298.2±0.1） K, I=0.10 mol·dm^-3 KNO3 in pH 7.5-9.1, respectively, finding that the catalytic effect of GdL^1 was the best among the four complexes for hydrolysis of HPNP. Its kLnLH-1, kLnLand pKa are 0.047 mol^-1·L·s^-1, 0.000074 mol^-1·L·s^-1 and 8.90, respectively. This paper expounded the studied result with the structure of the ligands and the properties of the metal ions, and deduced the catalysis mechanism.

Structural changes of cellobiohydrolase I (1,4-β-D-glucan-cellobiohydrolase I, CBHI) and PNPC (p-nitro-phenyl-β-D-cellobioside) during the binding process

Conformational changes to 1,4-β-D-glucan cellobiohydrolase I (CBHI) in response to its binding with p-nitrophenyl β-D-cellobioside (PNPC) were analyzed by second-derivative fluorescence spectrometry at the saturation binding point. Irreversible changes to the configuration of PNPC during the course of the binding process were characterized by UV spectral analysis. Isothermal titration calorimetry (ITC) was used to determine the stoichiometry of binding (i.e. the number of molar binding sites) of PNPC to CBHI. Two points on the surface of the CBHI molecule interact with PNPC, and irreversible changes to the configuration of PNPC occur during its conversion to p-nitrophenyl (PNP). The ITC studies demonstrated that the binding of PNPC to CBHI is an irreversible process, in which heat is released, but where there is no reversible equilibrium between PNPC-CBHI and CBHI and PNPC. On the other hand, PNP and cellobiose need to be released from the PNPC-CBHI complex to facilitate the repeated binding of new PNPC molecules to the renewable CBHI molecules. Therefore, we speculate that the energy, which powers the configurational change of PNPC as it is converted to PNP, is generated from cyclic changes in the conformation of CBHI during the binding/de-sorption process. These new insights may provide a basis for a better understanding of the binding mechanism in enzyme-substrate interactions.