Computational study on the interactions of mustard gas with cucurbituril macrocycles

The study on the absorption of toxic gases such as mustard gas by organic host is essential to the development of inexpensive detection and decontamination equipments. Using quantum chemical methods, we propose cucurbituril as an effective host to capture mustard gas. It was found that stable complexes are formed with the inclusion of the toxic gas molecules inside the cucurbituril cavity, compared with the lateral and exterior interactions. Oxygen mustard has a comparable binding energy with sulfur mustard and hence can be used during experimental investigation. Additionally, during the inclusion complex formation, the presence of heteroatoms helps the guest molecules to undergo a larger structural reorganization to get accommodated inside the cucurbituril macromolecule. Atoms‐in‐molecules analysis shows the existence of strong intermolecular CH…O bonding between the guest molecules and cucurbituril macromolecule. The presence of an intramolecular CH…Cl type of bonding accounts for the higher stabilization of sulfur mustard inside the cucurbituril macromolecule. © 2015 Wiley Periodicals, Inc.     

Computational design of tetrahedral silsesquioxane-based porous frameworks with diamond-like structure as hydrogen storage materials

A novel type of three-dimensional (3D) tetrahedral silsesquioxane-based porous frameworks (TSFs) with diamond-like structure was computationally designed using the density functional theory (DFT) and classical molecular mechanics (MM) calculations. The hydrogen adsorption and diffusion properties of these TSFs were evaluated by the methods of grand canonical Monte Carlo (GCMC) and molecular dynamics (MD) simulations. The results reveal that all designed materials possess extremely high porosity (87–93 %) and large H₂ accessible surface areas (5,268–6,544 m² g^?1). Impressively, the GCMC simulation results demonstrate that at 77 K and 100 bar, TSF-2 has the highest gravimetric H₂ capacity of 29.80 wt%, while TSF-1 has the highest volumetric H₂ uptake of 65.32 g L^?1. At the same time, the gravimetric H₂ uptake of TSF-2 can reach up to 4.28 wt% at the room temperature. The extraordinary performances of these TSF materials in hydrogen storage made them enter the rank of the top hydrogen storage materials so far.     

Imaging mass spectrometry distinguished the cancer and stromal regions of oral squamous cell carcinoma by visualizing phosphatidylcholine (16:0/16:1) and phosphatidylcholine (18:1/20:4)

Most oral cancers are oral squamous cell carcinoma (OSCC). The anatomical features of OSCC have been histochemically evaluated with hematoxylin and eosin. However, the border between the cancer and stromal regions is unclear and large portions of the cancer and stromal regions are resected in surgery. To reduce the resected area and maintain oral function, a new method of diagnosis is needed. In this study, we tried to clearly distinguish the border on the basis of biomolecule distributions visualized by imaging mass spectrometry (IMS). In the IMS dataset, eleven signals were significantly different in intensity (p?<?0.01) between the cancer and stromal regions. Two signals at m/z 770.5 and m/z 846.6 were distributed in each region, and a clear border was revealed. Tandem mass spectrometric (MS/MS) analysis identified these signals as phosphatidylcholine (PC) (16:0/16:1) at m/z 770.5 in the cancer region and PC (18:1/20:4) at m/z 846.6 in the stromal region. Moreover, the distribution of PC species containing arachidonic acid in the stromal region suggests that lymphocytes accumulated in response to the inflammation caused by cancer invasion. In conclusion, the cancer and stromal regions of OSCCs were clearly distinguished by use of these PC species and IMS analysis, and this molecular identification can provide important information to elucidate the mechanism of cancer invasion.     

The Critical Effect of Niobium Doping on the Formation of Mesostructured TiO2: Single‐Crystalline Ordered Mesoporous Nb‐TiO2 and Plate‐like Nb‐TiO2 with Ordered Mesoscale Dimples

Highly ordered mesoporous niobium‐doped TiO₂ with a single‐crystalline framework was prepared by using silica colloidal crystals with ca. 30 nm in diameter as templates. The preparation of colloidal crystals composed of uniform silica nanoparticles is a key to obtain highly ordered mesoporous Nb‐doped TiO₂. The XPS measurements of Nb‐doped TiO₂ showed the presence of Nb⁵⁺ and correspondingly Ti³⁺. With the increase in the amount of doped Nb, the crystalline phase of the product was converted from rutile into anatase, and the lattice spacings of both rutile and anatase phases increased. Surprisingly, the increase in the amount of Nb led to the formation of plate‐like TiO₂ with dimpled surfaces on one side, which was directly replicated from the surfaces of the colloidal silica crystals.     

Anti-obesity effects of escins extracted from the seeds of Aesculus turbinata BLUME (Hippocastanaceae)

To investigate the anti-obesity effects of escins extracted from the seeds of Aesculus turbinata BLUME, anti-obesity models in vitro and in vivo were employed. In a preliminary experiment, different solvent fractions of Aesculus turbinata BlUME as well as two isolated compounds were tested for their effects on pancreatic lipase (PL) in vitro. Subsequently, female ICR mice were fed a high fat diet with or without different concentrations of total escins for 11 weeks to examine body weight, parametrial adipose tissue weight, and hepatic triacylglycerol (TG) and total cholesterol (TC) contents. Plasma triacylglycerol levels (TG) after oral administration of lipid emulsions to rats were also investigated. The results showed that total escins (1 mg/ml) as well as two compounds isolated from total escins, namely escin Ib and IIa, showed inhibitory effects on PL activity. In vivo, total escins suppressed the increase in body weight, parametrial adipose tissue weight, TG content, and TC content in mice's liver; TG content in rat plasma was also reduced at 1, 2 and 3 h after oral administration of the lipid emulsion plus different concentrations of escins compared to those in the lipid emulsion groups. Meanwhile, mice fed a high fat diet plus 2% total escins for 3 d had an increased TG level in the feces compared to the HF group. The reason for this may be due to a delay in the intestinal absorption of dietary fat by inhibiting PL activity.     

Electron transport through carbon nanotube intramolecular heterojunctions with peptide linkages

We present a systematic analysis of electron transport characteristics of carbon nanotube (CNT) intramolecular heterojunctions with peptide linkages, MM, SS, SM1, and SM2 where M and S stand for metallic and semiconducting CNT electrodes, respectively. Our theoretical investigations show that the incorporation of peptide linkages and their associated dipole moments play an important role in determining the electron transport characteristics and lead to materials with unique properties, such as Schottky-like behavior. Furthermore, we show that the Schottky-like behavior is observed in our SM1 junction but not in the SM2 junction because of the different effects that arise from both the direction and strength of their dipole moments. We believe that our results will pave the way towards the design and implementation of various electronic logic functions based on carbon nanotubes for applications in the field of nanoelectronics.     

Starter units of the biosynthesis of blepharismins: self-defense pigments of Blepharisma japonicum

The heterotrich ciliate Blepharisma japonicum produces red pigment blepharismins, which function as self-defense toxin against predators and as a photoreceptor for step-up photonegativity. The dibenzoperylenequinone moiety of blepharismins was shown to be biosynthesized via the polyketide pathway. In this paper, the starter units of the biosynthetic pathway of blepharismins were determined to be isovaleryl-CoA and butyryl-CoA by HPLC, LC/ESI-MS, and ¹H and ²H NMR analyses of the pigments obtained from feeding experiment of l-leucine or sodium butyrate in excess and deuterium-labeled l-leucine.     

Reaction of germabenzenylpotassium with TBDMSCl: Unusual trimerization of germabenzene skeletons

Abstract

The reaction of 2-t-Bu-germabenzenylpotassium with Me₂(t-Bu)SiCl (TBDMSCl) resulted in the coupling among two TBDMS-substituted germabenzenes and the germabenzenylpotassium. The structure of the product was determined by X-ray crystallographic analysis. Its formation mechanism was proposed with the help of theoretical calculations.     

Copper‐Free Huisgen Cycloaddition for the 14‐3‐3‐Templated Synthesis of Fusicoccin‐Peptide Conjugates

Mid‐sized molecules have emerged as an attractive chemical space and potentially provide a robust basis for the development of synthetic agents to control intracellular protein interactions. However, the limited cell permeability and chemical tractability of such agents remain to be addressed. We envisioned that target‐templated synthesis of such mid‐sized molecules might provide a solution. Here, we exploited a copper‐free Huisgen cycloaddition for template synthesis using a peptide fragment containing a 4,8‐diazacyclononyne (DACN) moiety and an azide‐containing fusicoccin derivative in the presence or absence of recombinant 14‐3‐3ζ protein in vitro. Time‐course changes in the yield of products demonstrated that the reaction was accelerated in the presence of 14‐3‐3 and one of the regioisomers was generated predominantly, supporting the template effect.     

Population study of sizes and components of self-reproducing giant multilamellar vesicles

Population analysis of a system of self-reproducing giant multilamellar vesicles (GMVs) was carried out by means of flow cytometry. The multidimensional distribution of forward light scattering (FS), side light scattering (SS), and fluorescence (FL) intensities originating from each GMV provided information about changes in a population composed of 104 vesicles. FS-FL dot plots indicated that, after the addition of the membrane precursor, the size distribution of the newly generated vesicles was nearly the same as that of the original, but the catalyst content was reduced. This result can be interpreted as evidence for the occurrence of the self-reproduction of GMVs. Moreover, the new GMVs recovered the amount of catalyst to the initial value, keeping their size distribution constant, when a solution of the catalyst was added to the new GMVs. These results are the first experimental evidence for a novel phenomenon on GMV size distribution during their self-reproducing cycle.