pH-Responsive Phase Transition of Supramolecular Hydrogel Consisting of Glycosylated Amino Acetate and Carboxylic Acid Derivative

By addition of a carboxylated amino acetate (2) to a low-molecular-weight hydrogel (1) which has a unique thermally induced volume-phase transition character, a macroscopic pH-responsive feature is newly conferred on the supramolecular hydrogel. The direct observation of temperature-dependent behavior of the mixed hydrogel clearly showed that the thermally induced swelling-shrinkage type of the volume phase transition at pH 4 is shifted to the gel–sol transition at pH 7 by 10?mol% addition of 2 to the hydrogel 1. On the basis of the measurements by TEM, SEM, XRD and FT-IR, it is conceivable that incorporation of the anionic carboxylate of 2 slightly disturbs the packing of the hydrogen bond belt of the mixed hydrogel. Such a slight disturbance greatly leads to the sol–gel transition by elevating temperature, instead of the volume-phase transition. Introduction of dynamic characteristics to supramolecular systems in a macroscopic level may extend the potential of these materials in various fields.     

Synthesis, structure, and activity evaluation of two silver(I) complexes as Helicobacter pylori urease inhibitors

Two silver(I) compounds, [Ag(R,R-hxn)](C₇H₄BrO₂) · 2H₂O (I) (Chxn = 1,2-diaminocyclohexane) and [Ag(C₅H₆N₂)₂]₂(C₈H₄O₄) · 10H₂O (II), were synthesized and complex I was structurally characterized by X-ray crystallography. Compound I contains a catena-(trans-1,2-diaminocyclohexane) silver polycation ([Ag(Chxn)]_∞) in a roughly linear fashion, while II possesses a linear-type silver monocation. Compounds I and II were evaluated for their inhibitory activities against Helicobacter pylori urease in vitro. Both were found to have strong inhibitory activities against H. pylori urease comparable to that of acetohydroxamic acid.     

Study on thermodynamic properties of glyphosate by oxygen-bomb calorimeter and DSC

The combustion enthalpy of glyphosate was determined by XRY-1C oxygen-bomb calorimeter at a constant volume. The standard mole combustion enthalpy and the standard mole formation enthalpy have been calculated to be ?1702.19 and ?1478.36 kJ mol^?1, respectively. For testing the reliability of instrument, glycine and naphthalene were used as reference materials by comparing the measured values with the literature values, the absolute error and relative error are 2.58 kJ mol^?1 and 0.26 % for glycine, respectively, and these of naphthalene are 4.08 kJ mol^?1 and 0.08 %, respectively. Moreover, the constant-pressure heat capacities c _p of glyphosate were measured by differential scanning calorimetry in the temperature range 303.15–365.15 K, and the relationship between c _p and temperature was established. These related studies can provide a thermodynamic basis for their further application.     

Magnesium boride sintered as high-energy fuel

Boron was chosen as fuel owing to its excellent thermodynamic values for combustion. The difficulty of the boron in combustion is the formation of a surface oxide layer, which postpones the combustion process, reducing the performance of the rocket engine. In this paper, magnesium boride was sintered as high-energy fuel as a substitute for boron. The combustion heat and efficiency of magnesium boride and boron were determined using oxygen bomb calorimeter. The combustion characteristics of magnesium boride were investigated by thermal analysis, chemical analysis, XRD, and EDS. Results show that the combustion performance of magnesium boride are better than that of amorphous boron in oxygenated environments. The evaporation of magnesium in magnesium boride combustion process prevent the formation of a closed oxide layer, leading to higher combustion efficiency.     

Excellent electrochemical performance of nitrogen-enriched hierarchical porous carbon electrodes prepared using nano-CaCO3 as template

Recently, tremendous research efforts have been concentrated on developing high-performance electrode materials to meet the ever-increasing energy and power demands in supercapacitors. Herein, we presented a high-capacity supercapacitor material based on nitrogen-enriched hierarchical porous carbons (NHPCs) synthesized by the carbonization of melamine formaldehyde resins using eco-friendly and inexpensive nano-CaCO₃ as template. The effects of carbonization temperature and template content on the porous structure and electrochemical characteristics were compared and discussed in detail. The prepared NHPCs possessed large surface area up to 834 m² g^?1 and high nitrogen content up to 20.94 wt %. As electrode material for supercapacitors, NHPCs exhibited superior electrochemical performances with high specific capacitance (190 F g^?1 at 20 A g^?1), outstanding rate capability (80 %), and excellent cycling stability (over 2,000 cycles at 5 A g^?1) in 1 M sulfuric acid media. The excellent electrochemical performances are due to the synergic effects of unique hierarchical porous microstructure, abundant nitrogen and oxygen functionalities, as well as high degree of graphitization framework.     

Ligand binding and unfolding of tryptophan synthase revealed by ion mobility-tandem mass spectrometry employing collision and surface induced dissociation

Understanding protein tertiary and quaternary structures is crucial to a better understanding of their biological functions. Here we illustrate for tryptophan synthase that tandem mass spectrometry (MS/MS) reveals not only protein subunit architectures, but also protein unfolding behavior when coupled with ion mobility (IM). In the present study, we verified the subunit arrangement with surface induced dissociation (SID). We are able to correlate experimental results by IM with those obtained in unfolding simulations for the hetero-tetramer Tryptophan Synthase (TS) protein complex by identifying the presence of at least three stable intermediates (I₁, I₂, and I₃) during the unfolding process in collision induced dissociation (CID). We illustrate that the unfolding of the TS complex is likely due to the initial unfolding of an α-monomer subunit, followed by the unfolding of the second α-monomers. We also illustrate the ability of this combination of techniques to not only identify conformational changes of TS upon addition of D,L-α-glycerol phosphate (GP), but also to determine the location of the ligand, which is buried within the α-monomer of the TS.     

Characterizing the Role of Iodine Doping in Improving Photovoltaic Performance of Dye‐Sensitized Hierarchically Structured ZnO Solar Cells

We report two novel types of hierarchically structured iodine‐doped ZnO (I? ZnO)‐based dye‐sensitized solar cells (DSCs) using indoline D205 and the ruthenium complex N719 as sensitizers. It was found that iodine doping boosts the efficiencies of D205 I? ZnO and N719 I? ZnO DSCs with an enhancement of 20.3 and 17.9 %, respectively, compared to the undoped versions. Transient absorption spectra demonstrated that iodine doping impels an increase in the decay time of I? ZnO, favoring enhanced exciton life. Mott–Schottky analysis results indicated a negative shift of the flat‐band potential (V_fb) of ZnO, caused by iodine doping, and this shift correlated with the enhancement of the open circuit voltage (V_oc). To reveal the effect of iodine doping on the effective separation of e^?‐h⁺ pairs which is responsible for cell efficiency, direct visualization of light‐induced changes in the surface potential between I? ZnO particles and dye molecules were traced by Kelvin probe force microscopy. We found that potential changes of iodine‐doped ZnO films by irradiation were above one hundred millivolts and thus significantly greater. In order to correlate enhanced cell performance with iodine doping, electrochemical impedance spectroscopy, incident‐photon‐current efficiency, and cyclic voltammetry investigations on I? ZnO cells were carried out. The results revealed several favorable features of I? ZnO cells, that is, longer electron lifetime, lower charge‐transfer resistance, stronger peak current, and extended visible light harvest, all of which serve to promote cell performance.     

Self‐Assembly of Anionic Porphyrins and Alkaline or Alkaline Earth Metal Ions Mediated by Cucurbit[7,8]uril

Nanoscaled coordination polymers based on biologically prevalent ions have potential applications in drug delivery and biomedical imaging. Herein, coordination polymer nanoparticles of anionic porphyrins, including meso‐tetra(4‐carboxyphenyl)‐porphyrin (H₂TCPP^4?) and meso‐tetra(4‐sulfonatophenyl)‐porphyrin (H₂TPPS^4?), and alkaline or alkaline earth metal cations, such as K⁺ and Ca²⁺, were constructed in aqueous solution in the presence of cucurbit[7]uril (CB7) or cucurbit[8]uril (CB8). UV/Vis absorption and fluorescence spectroscopy, dynamic light scattering (DLS), scanning electron spectroscopy (SEM), and atomic force microscopy (AFM) were applied to explore the assembly and particle formation of porphyrin anions and metal cations mediated by CBn. The particle size depends on the kinds of CBn and metal cations and their concentrations. The uptake of H₂TPPS^4? particles by tumor cells (A549 cells) was found to be more efficient than H₂TPPS^4? at 37 °C, showing the application potential of such assembled particles in biology and medicine.     

Enantiomeric separations of four basic drugs containing N-alkyl groups by a RP-HPLC system using SBE-β-CD as chiral mobile phase additive

The chiral separations of four pharmaceutical racemates which contain N-alkyl groups were satisfactorily resolved using SBE-β-CD as a chiral mobile phase additive(CMPA)in a RP-HPLC system(the resolution is 2.701 for ondansetron hydrochloride,1.996 for sulpiride,1.293 for clenbuterol hydrochloride and 0.816 for omeprazole).In addition,the effects of different parameters such as CD type and CD concentration were investigated.The separation mechanism arises through the combination of several potential interactions,including electrostatic interactions as well as hydrogen bonding interactions and hydrophobic inclusion interactions,which allow for the SBE-β-CD–drug complexation with strong stereoselectivity and stability.The resolution also relates to the number and location of N atoms in the enantiomers.This method will be applicable to the isolation of various types of biologically important enantiomers containing N-alkyl groups.