Biodegradable Interpolyelectrolyte Complexes Based on Methoxy Poly(ethylene glycol)-b-poly(alpha,L-glutamic acid) and Chitosan

We synthesized methoxy poly(ethylene glycol)-b-poly(alpha,L-glutamic acid) (mPEGGA) diblock copolymer by ring-opening polymerization of N-carboxy anhydride of gamma-benzyl-L-glutamate (NCA) using amino-terminated methoxy polyethylene glycol (mPEG) as macroinitiator. Polyelectrolyte complexation between mPEGGA as neutral-block-polyanion and chitosan (CS) as polycation has been scrutinized in aqueous solution as well as in the solid state.

Ethylene polymerization by (alpha-diimine)nickel(II) complexes bearing different substituents on para-position of imines activated with MMAO

A series of (alpha-diimine)nickel(II) complexes [ArN = C(Nap)C = NAr]NiBr2 (Nap = 1,8-naphthdiyl, Ar = 2,6-Me2C6H3, 3a; Ar = 2,4,6-Me3C6H2 3b; Ar = 2,6-Me-2-4-tBuC(6)H(2), 3c; Ar 2,6-Me-2-4-BrC6H2, 3d; Ar = 2,6-Me-2-4-ClC6H2, 3e; Ar 2,6-iPr(2)C(6)H(3), 3f; Ar = 2,4,6-iPr(3)C(6)H(2), 3g; Ar = 2,6-iPr-4-BrC6H2, 3h) have been synthesized, characterized, and investigated as precatalysts for ethylene polymerization in the presence of modified methylaluminoxane (MMAO).

Polymerization of ethylene to branched polyethylene with silica and Merrifield resin supported nickel(II) catalysts with alpha-diimine ligands

Silica and Merrifield resin were used as carriers for the support of alpha-diimine nickel(II) precatalysts for ethylene polymerization. The alpha-diimine ligands containing allyl were modified by introducing the reactive Si-Cl end-group, allowing their immobilization via a direct reaction of the Si-Cl groups with the silanols on silica surface or the hydroxyls on the ethanolamine-modified Merrifield resin. The resulting supported alpha-diimine ligands were characterized by analytical and spectroscopic techniques (NMR and Fr-IR).

Refinement of edge-to-edge matching model and its application in the Mg17Al12/alpha-Mg and alpha-Y/alpha-Mg systems

A refined version of the edge-to-edge matching model is described here. In the original model, the matching directions were obtained from the planes with all the atomic centers that were exactly in the plane, or the distance from the atomic center to the plane which was less than the atomic radius. The direction-matching pairs were the match of straight rows-straight rows and zigzag rows-zigzag rows. In the refined model, the matching directions were obtained from the planes with all the atomic centers that were exactly in the plane.

Hollow DNA/PLL microcapsules with tunable degradation property as efficient dual drug delivery vehicles by alpha-chymotrypsin degradation

Hollow deoxyribonucleic acid (DNA)/poly-L-lysine (PLL) capsules were successfully fabricated through a layer-by-layer (LbL) self-assembly of DNA and PLL on porous CaCO3 microparticles, followed by removal of templates with ethylenediamine tetraacetic acid disodium salt (EDTA). The enzymatic degradation of the capsules in the presence of alpha-chymotrypsin was explored. The higher the enzyme concentration, the higher is the degradation rate of hollow capsules. in addition, glutaric dialdehyde (GA) cross-linking was found to be another way to manipulate degradation rate of hollow capsules.

Screening and Structural Characterization of alpha-Glucosidase Inhibitors from Hawthorn Leaf Flavonoids Extract by Ultrafiltration LC-DAD-MSn and SORI-CID FTICR MS

In vitro a-glucosidase inhibition assays and ultrafiltration liquid chromatography with photodiode array detection coupled to electrospray ionization tandem mass spectrometry (ultrafiltration LC-DAD-ESI-MSn) were combined to screen a-glucosidase inhibitors from hawthorn leaf flavonoids extract (HLFE). As a result, four compounds were identified as alpha-glucosidase inhibitors in the HLFE, and their structures were confirmed to be quercetin-3-O-rha-(1-4)-glc-rha and C-glycosylflavones (vitexin-2 ''-O-glucoside, vitexin-2 ''-O-rhamnoside and vitexin) by high-resolution sustained off resonance irradiation collision-induced dissociation (SORI-CID) data obtained by Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS).

Investigation of Chemical Bond Characteristics, Thermal Expansion Coefficients and Bulk Moduli of alpha-R2MoO6 and R2Mo2O7 (R = rare earths) by Using a Dielectric Chemical Bond Method

Theoretical researches are performed on the alpha-R2MoO6 (R = Y, Gd, Tb Dy, Ho, Er, Tm and Yb) and pyrochlore-type R2Mo2O7 (R = Y, Nd, Sm, Gd, Tb and Dy) rare earth molybdates by using chemical bond theory of dielectric description. The chemical bonding characteristics and their relationship with thermal expansion property and compressibility are explored. The calculated values of linear thermal expansion coefficient (LTEC) and bulk modulus agree well with the available experimental values. The calculations reveal that the LTECs and the bulk moduli do have linear relationship with the ionic radii of the lanthanides: the LTEC decreases from 6.80 to 6.62 10(-6)/K and the bulk modulus increases from 141 to 154 GPa when R goes in the order Gd, Tb Dy, Ho, Er, Tm, and Yb in the alpha-R2MoO6 series; while in the R2Mo2O7 series, the LTEC ranges from 6.80 to 6.61 10(-6)/K and the bulk modulus ranges from 147 to 163 GPa when R varies in the order Nd, Sm, Gd, Tb and Dy.

Copolymerizations of ethylene with alpha-olefin-omega-ols by highly active vanadium(III) catalysts bearing [N,O] bidentate chelated ligands

The copolymerizations of ethylene with polar hydroxyl monomers such as 10-undecen-1-ol, 5-hexen-1-ol and 3-buten-1-ol were investigated by the vanadium(III) catalysts bearing bidentate [N,O] ligands (1, [PhN=C(CH3)CHC(Ph)O]VCl2(THF)(2): 2, [PhN=CHC6H4O]VCl2(THF)(2); 3, [PhN=CHC(Ph)CHO]VCl2(THF)(2)). The polar monomers were pretreated by alkylaluminum before the polymerization. High catalytic activities and efficient comonomer incorporations can be easily obtained by changing monomer masking reagents and polymerization conditions in the presence of diethylaluminium chloride as a cocatalyst. The longer the spacer group, the higher the incorporation of the monomer. Under the mild conditions, the incorporation level of 10-undecen-1-ol reached 13.9 mol% in the resultant copolymers was obtained. The reactivity ratios of copolymerization (r(1) = 41.4, r(2) = 0.02, r(1)r(2) = 0.83) were evaluated by Fineman-Ross method. According to C-13 NMR spectra, polar units were located both on the main chain and at the chain end.

A Facile and Efficient One-Pot Synthesis of Substituted Quinolines from alpha-Arylamino Ketones Under Vilsmeier Conditions

An efficient one-pot synthesis of substituted quinolines from alpha-arylamino ketones in the presence of PBr3 in DMF has been developed. This general protocol provides a novel and facile access to substituted quinolines by sequential Vilsmeier-Haack reaction, intramolecular cyclization and aromatization reactions of alpha-arylamino ketones. PBr3 plays a dual role in the quinoline synthesis: as a key component of the Vilsmeier reagent (PBr3/DMF) and as a reducing reagent.

Photoinduced DNA Cleavage by alpha-, beta-, and gamma-Cyclodextrin-Bicapped C-60 Supramolecular Complexes

Water-soluble supramolecular inclusion complexes of alpha-, beta-, and gamma-cyclodextrin-bicapped C-60 (CD/C-60) have been investigated for their photoinduced DNA cleavage activities, with the aim to assess the potential health risks of this class of compounds and to understand the effect of host cyclodextrins having different cavity dimensions. Factors such as incubation temperature, irradiation time, and concentration of NADH or CDs/C-60 supramolecular inclusion complexes have been examined. The results show that alpha-, beta-, and gamma-CDs/C-60 are all able to cleave double-stranded DNA under visible light irradiation in the presence of NADH. However, a difference in the photoinduced DNA cleavage efficiency is observed, where the cleavage efficiency increases in the order of alpha-, beta-, and gamma-CD/C-60. The difference is attributed to the different aggregation behavior of the inclusion complexes in aqueous solution, which is correlated to the cavity dimension of the host cyclodextrin molecules.

A New Method for Analysis of Disulfide-Containing Proteins by Matrix-Assisted Laser Desorption Ionization (MALDI) Mass Spectrometry

A simple and high-throughput method for the identification of disulfide-containing peptides utilizing peptide-matrix adducts is described. Some commonly used matrices in MALDI mass spectrometry were found to specifically react with sulfhydryl groups within peptide, thus allowing the observation of the peptide-matrix adduct ion [M + n + n' matrix + H](+) or [M + n + n' matrix + Na](+) (n = the number of cysteine residues, n' = 1, 2, ..., n) in MALDI mass spectra after chemical reduction of disulfide-linked peptides. Among several matrices tested, alpha-cyano-4-hydroxycinnamic acid (CHCA, molecular mass 189 Da) and alpha-cyano-3-hydroxycinnamic acid (3-HCCA) were found to be more effective for MALDI analysis of disulfide-containing peptides/proteins. Two reduced cysteines involved in a disulfide bridge resulted in a mass shift of 189 Da per cysteine, so the number of disulfide bonds could then be determined, while for the other matrices (sinapinic acid, ferulic acid, and caffeic acid), a similar addition reaction could not occur unless the reaction was carried out under alkaline conditions. The underlying mechanism of the reaction of the matrix addition at sulfhydryl groups is proposed, and several factors that might affect the formation of the peptide-matrix adducts were investigated.

Biosynthesis of gold nanoparticles assisted by Escherichia coli DH5 alpha and its application on direct electrochemistry of hemoglobin

In this communication, biosynthesis of gold nanoparticles assisted by Escherichia coli DH5 alpha and its application on direct electrochemistry of hemoglobin are reported. The gold nanoparticles formed on the bacteria surface are mostly spherical. The direct electrochemistry of hemoglobin can be achieved by incorporated into the bio-nanocomposite films on a glassy carbon electrode.

Interaction between alpha-actinin and negatively charged lipids membrane investigated by surface plasmon resonance and electrochemical methods

alpha-Actinin has been shown to be capable of interacting with some special membrane phospholipids directly, which is important for its function. In this study, hybrid bilayer membranes composed of negatively charged lipids are constructed on the surface plasmon resonance gold substrate and on the gold electrode, respectively, and the interaction between alpha-actinin and negatively charged lipids membrane is investigated by surface plasmon resonance, cyclic voltammetry and electrochemical impedance spectroscopy methods. alpha-Actinin is proved to be able to interact with the negatively charged lipids membrane directly. It can also insert at least partly into the membrane or lead to some defect or lesion in the membrane, which increase the permeability of the membrane. This study would bring some insight on the interaction between the alpha-actinin and the cell membranes in vivo.

Extended application of edge-to-edge matching model to HCP/HCP (alpha-Mg/MgZn2) system in magnesium alloys

In the present work, the edge-to-edge matching model has been introduced to predict the orientation relationships (OR) between the MgZn2 phase which has hexagonal close packed (HCP) structure and the HCP a-Mg matrix. Based on the crystal structures and lattice parameters only, the model has predicted the two most preferred ORs and they are: (1) [1 1 2 3](alpha-Mg) vertical bar vertical bar]1 1 2 3](alpha-Mg), (0 0 0 1)(alpha-Mg) 0.27 degrees from (0 0 0 1)(MgZn2), (1 0 1 1)(alpha-Mg) 26.18 degrees from (1 1 2 2)(MgZn2), (2) [1 0 1 0](alpha-Mg),vertical bar vertical bar[1 1 2 0](MgZn2), (0 0 0 1)(alpha-Mg) vertical bar vertical bar(0 0 0 1)(MgZn2), (1 0 1 1)(alpha-Mg) 3.28 degrees from ( 1 1 2 2)(MgZn2). Four experimental ORs have been reported in the alpha-Mg/MgZn2 system, and the most frequently reported one is ideally the OR (2). The other three experimental ORs are near versions of the OR (2). The habit plane of the OR (2) has been predicted and it agrees well with the experimental results.

One-pot synthesis of substituted isothiazol-3(2H)-ones: Intramolecular annulation of alpha-carbamoyl ketene-S,S-acetals via PIFA-Mediated N-S bond formation

A facile and efficient synthetic route towards; highly substituted isothiazol-3(2H)-ones 2 from readily available U.-carbamoyl ketene-S,S-acetals 1 is presented. The key step features the formation of an N-acylnitrenium ion, generated from the oxidization of substituted amides with the hypervalent iodine reagent phenyliodine(III) bis(trifluoroacetate) (PIFA), and its succeeding intramolecular amidation to form a new N-S bond affording the title compounds.