Cinnamic acid derivatives as matrices for ultraviolet laser desorption mass spectrometry of proteins

The paper reports the discovery of three new matrices for the matrix-assisted laser desorption of proteins. These new matrices (sinapinic, ferulic and caffeic acids) are cinnamic acid derivatives that have several practical advantages over the nicotinic acid matrices previously used. These materials form much less intense photochemically generated adduct peaks in the protein quasimolecular ion signal and the adduct peaks that are present are easier to resolve. These matrices produce intense protonated-molecule ions from all of the proteins (over 50) so far examined. These new matrices are also very stable in a vacuum, allowing for their convenient use in very high vacuum applications (e.g., Fourier transform ion cyclotron resonance mass spectrometry).     

Synthesis of Highly Charged, Monodisperse Polystyrene Colloidal Particles for the Fabrication of Photonic Crystals

We have developed a series of emulsion polymerization recipes for the synthesis of highly charged, monodisperse polystyrene colloids of diameters between 100-400 nm. These spherical colloidal particles were crosslinked with divinyl benzene and functionalized with 1-allyloxy-2-hydroxypropane sulfonate. These highly charged, monodisperse colloidal particles readily self-assemble into robust three-dimensionally ordered crystalline colloidal arrays (CCAs). These CCAs operate as photonic crystals that Bragg diffract light in the ultraviolet, visible, and infrared regions of the spectrum. Copyright 2000 Academic Press.     

Self-assembly of poly(9,9'-dihexylfluorene) to form highly ordered isoporous films via blending

Highly ordered hexagonal arrays of isoporous films prepared from poly(9,9'-dihexylfluorene) and polystyrene-grafted silica nanoparticles (Si-graft-PS) are presented. These close-packed arrays were formed in areas of many square millimeters. The pore size varied from 3.6 to 8.5 microm, depending on the concentration of Si-graft-PS and the processing conditions. Solid-state photoluminescence resulted in a significant red shift of up to 30 nm in these films compared to that in conventional processing techniques. These differences are attributed to enhanced aggregation of the polymers caused by polymer-solvent interactions. These highly ordered polymer films may find use in microelectronic and biological and/or chemical sensor applications.     

Dérivés de la dihydro-2,4 triazole-1,2,4 thione-3 et de l'amino-2 thiadiazole-1,3,4 à partir de nouvelles thiosemicarbazones d'esters

A new general synthesis of 4,5-disubstituted 2,4-dihydro-1,2,4-triazole-3-thiones is proposed. These heterocycles are obtained by the action of primary amines, arylhydrazines or aroylhydrazines on the thiosemicarbazones of eaters. These last compounds are prepared by action of chlorhydrates of iminoethers on thiosemicarbazide in dimethylformamide. These thiosemicarbazones react also with strong acids, acid anhydrides and chlorides; by thermolysis and they give 2-amino-1,3,4-thiadiazole derivatives. Also, two derivatives of 1,2,4-triazolo[3,4-b]-1,3,4-thiadiazole have been prepared.     

Electroactive supramolecular self-assembled fibers comprised of doped tetrathiafulvalene-based gelators

New electroactive supramolecular fibers have been formed by self-assembly of the derivatives of tetrathiafulvalene (TTF) in liquid crystals. These derivatives are designed and prepared by introducing the TTF moiety to the scaffold derived from amino acids such as L-isoleucine whose derivatives function as organogelators. These TTF-based gelators form stable fibrous aggregates in liquid crystals. These fibers are the first example of hydrogen-bonded one-dimensional aggregates having electroactive moieties whose electrical conductivities were measured after doping. Their electronic states have also been characterized by spectroscopic methods. Unidirectionally aligned fibers are formed in the oriented liquid crystal solvents on the rubbed polyimide surface for further functionalization of the fibers.     

Cycloaddition reactions of benzyne with olefins

Some novel cycloaddition reactions based on benzyne and olefins have been developed.These reactions were performed in the absence of a transition metal catalyst,and they displayed good yields.These cycloaddition reactions of benzyne with olefins provide effective routes for synthesizing benzocyclobutenes,biaryl compounds and 9,10-dihydrophenanthrene derivatives.     

分析化学样品前处理技术研究进展

综述分析化学中样品前处理技术的重要地位、分类及研究进展情况,并对超临界流体萃取等几种近年来发展较快的样品前处理新方法的原理及特点作了介绍。这些技术能够有效地减少分析过程中由样品前处理过程带来的误差,具有前处理快速、简便的优点,同时可与分析仪器联用,实现分析的自动化。     

A totally synthetic, self-assembling, adjuvant-free MUC1 glycopeptide vaccine for cancer therapy

In the development of vaccines for epithelial tumors, the key targets are MUC1 proteins, which have a variable number of tandem repeats (VNTR) bearing tumor-associated carbohydrate antigens (TACAs), such as Tn and STn. A major obstacle in vaccine development is the low immunogenicity of the short MUC1 peptide. To overcome this obstacle, we designed, synthesized, and evaluated several totally synthetic self-adjuvanting vaccine candidates with self-assembly domains. These vaccine candidates aggregated into fibrils and displayed multivalent B-cell epitopes under mild conditions. Glycosylation of Tn antigen on the Thr residue of PDTRP sequence in MUC1 VNTR led to effective immune response. These vaccines elicited a high level antibody response without any adjuvant and induced antibodies that recognized human breast tumor cells. These vaccines appeared to act through a T-cell independent pathway and were associated with the activation of cytotoxic T cells. These fully synthetic, molecularly defined vaccine candidates had several features that hold promise for anticancer therapy.     

Synthesis,structure, and evaluation of the effect of multiple stacking on the electron-donor properties of pi-stacked polyfluorenes

A versatile synthesis of pi-stacked polyfluorenes is described. These polyfluorenes retain their cofacial conformations both in solution and in the solid state as was judged by NMR spectroscopy and X-ray crystallography. The experimental electron-detachment energies of F1-F4 showed linear correlations with the quantity 1/n, where n is the number of fluorene moieties. These correlations allowed the estimation of the vertical ionization potential (IP) of 7.10 eV and the oxidation potential (Eox) of 0.97 V versus SCE for the multiply stacked polyfluorene donor with an infinite number of fluorene moieties. These observations with pi-stacked polyfluorenes may prove to be highly relevant to the electron-transport phenomenon observed in DNA through pi-stacked bases.     

New 3-hydroxyflavone derivatives for probing hydrophobic sites in microheterogeneous systems

Nine new 3-hydroxyflavone derivatives as fluorescent molecular sensors having two well-separated emission bands were synthesized. These sensors can occupy well-determined locations and orientations in macromolecular ensembles, such as micelles due to their finely-tuned designs. These polarity-sensitive dyes can incorporate into the anhydrous hydrophobic core of aqueous micelles.     

Catalyst-free and atom-economic synthesis of substituted 1-acetyl and 1-hydroxyl carbazoles

The first-ever Diels-Alder reactions of 3-alkenyl indoles with a conjugated alkynyl ketone are reported. These reactions proceed in an atom-economic manner without a catalyst and give various substituted 1-acetyl carbazoles in moderate to excellent yields. These products can be converted to 1-hydroxyl carbazoles in high yields under mild reaction conditions.     

化妆品中铅的测定方法研究进展

综述近年来化妆品中铅的测定方法研究进展.介绍使用各种方法测定化妆品中铅含量的特点,包括分光光度法、原子吸收光谱法、原子发射光谱法、原子荧光法和电位溶出法.这些方法能够有效地减少分析过程中由样品的复杂性带来的误差,具有快速、简便的特点.     

Molecular modeling of bifunctional chelate peptide conjugates. 1. Copper and indium parameters for the AMBER force field

In this work we describe the development of parameters for In(III) and Cu(II) for the AMBER force field as found in the modeling package MacroModel. These parameters were developed using automated procedures from a combination of crystallographic structures and ab initio calculations. The new parameters were added in the form of AMBER substructures containing specific metal-ligand parameters to the existing force field. These new parameters have produced results in good agreement with experiment without requiring additional changes to the existing AMBER parameters. These parameters were then utilized to examine the conformational effects caused by the conjugation of InDTPA (DTPA = diethylenetriaminepentaacetic acid) and CuDOTA (DOTA = 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) to the cyclic octapeptide octreotide.     

Hydrogen bonding and anaesthesia

General anaesthetics act by perturbing intermolecular associations without breaking or forming covalent bonds. These associations might be due to a variety of van der Waals interactions or hydrogen bonding. Neurotransmitters all contain OH or NH groups, which are prone to form hydrogen bonds with those of the neurotransmitter receptors. These could be perturbed by anaesthetics.

Aromatic rings in amino acids can act as weak hydrogen bond acceptors. On the other hand the acidic hydrogen in halothane type anaesthetics are weak proton donors. These two facts together lead to a probable mechanism of action for all general anaesthetics.     

Dendrimers with both polar and apolar nanocontainer characteristics

Amphiphilic dendrimers with a custom-designed biaryl repeat unit have been synthesized. These dendrimers afford hydrophobic nanocontainers in polar solvents and hydrophilic nanocontainers in apolar solvents. These container properties were investigated using dye incorporation studies. The aggregation states of these dendrimers are also reported using DLS studies.     

Synthesis and use of chiral substituted benzenes containing 1,2-diols protected as cyclic acetals

1,2-Dihydroxy benzenes have been protected as cyclic diacetals using 2,3-butane dione. These diacetals are extremely robust and can be further chemically diversified and resolved with chirality embedded in the 1,4-dioxane ring attached to the aromatic back bone as a result of the anomeric effect. These systems can serve as ligands, auxiliaries or organocatalysts for asymmetric synthesis.     

Trace elements in human cancerous and healthy tissues: A comparative study by EDXRF,TXRF, synchrotron radiation and PIXE

It is known that trace elements play an important role in a number of biological processes. These include the activation or inhibition of enzymatic reactions, competition between elements and metal proteins for binding positions and modifications in the permeability of cellular membranes. These elements may also influence carcinogenic processes, thus the knowledge of trace element concentrations in healthy and neoplastic tissues might help in diagnostic and in the etiology and development of cancer.     

The colligative properties of certain electrolytes and non-electrolytes in methanol

Osmotic coefficients for methanol solutions of sodium iodide are calculated from recently published vapor pressure data. These data furnish a reference solute for other isopiestic studies in this solvent. Data are reported for three additional electrolytes and two non-electrolytes. These data are compared with the osmotic coefficients of the same solutes in water to illustrate and in some instances to elucidate the relative importance of various interactions in solutions.