A NEW ONE-STEP REDUCTIVE N-ALKYLATION OF AMINO ACIDS AND THEIR ESTERS

The reductive alkylation of amine with carbonyl compounds usingsodium hydrogen telluride has been investigated in recent years.Application of this method to the synthesis of N-alkyl derivativesof biologically important amino acids and their esters is described.     

Study of conical columns with 10 degrees opening angle for preparative liquid chromatography

The efficiency and sample capacity of conical liquid chromatographic columns with 10 degrees opening angle were studied at different ratio of cross section areas of inlet to outlet (A(in)/A(out)) and column dimension. As the A(in)/A(out) ratio changed from 4 to 2.25, the reduced plate height (h) was reduced and the h value decreased 12% when the column dimension was scaled up proportionally because of relatively smaller dead volume on both end of the column. Compared to cylindrical columns having corresponding lengths and volumes, the conical columns with 10 degrees opening angle were superior in column efficiency, resolution and the maximum peak concentration at column outlet; the loadability of conical column was improved 30-40% on injection volume and 50-60% on sample mass, respectively, over cylindrical columns.     

Unexpected cycloisomerizations of nonclassical carbocation intermediates in gold(I)-catalyzed homo-Rautenstrauch cyclizations

An unexpected gold(I)-catalyzed homo-Rautenstrauch rearrangement of 1-cyclopropyl propargylic esters to cyclohexenones is disclosed. This rearrangement represents new evidence for the recently discussed gold-stabilized nonclassical carbocation character of intermediates in gold catalysis. A mechanistic study proved partial chirality transfer from optically active propargyl acetates.     

Sulfopeptide fragmentation in electron-capture and electron-transfer dissociation

Sulfopeptides can be misassigned as phosphopeptides because of the isobaric nature of the sulfo- and the phosphomoieties. Instruments having the ability to measure mass with high accuracy may be employed to distinguish these moieties based on their mass defect (the sulfo-group is 9 mmu lighter than the phosphomoiety). However, the assignment of the exact site(s) of post-translational modification is required to probe biological function. We have reported earlier that peptides with identical sequences containing either O-sulfo- or O-phospho-modifications display different fragmentation behavior (K. F. Medzihradszky et al., Mol. Cell. Proteom.2004, 3, 429-440). We have also established that O-sulfo moieties are susceptible to side-chain fragmentation during collision-induced dissociation. Our present study provides evidence that neutral SO(3) losses can also occur in electron capture dissociation and electron-transfer dissociation experiments. We also report that such neutral losses may be reduced by fragmenting peptide-alkali metal adducts, such as sodiated or potassiated peptides.     

Spiral coils for counter-current chromatography using aqueous polymer two-phase systems

Retention properties of polyethylene glycol-phosphate aqueous two-phase systems in a spiral coil (5 mm I.D.) on Type-J synchronous counter-current chromatographic devices have been compared for the elution mode where the lower phase is the mobile phase and flows from the inside head terminal. This was achieved with the aid of digital imaging under stroboscopic illumination, an image analysis and measurement of the displaced volume of the stationary phase. For the spiral coil, high and stable stationary phase retention at mobile phase flow rates up to 64 ml/min has been obtained. Wave-like disturbance of the interface near the proximal point was observed and analyses have been made for possible use in protein separation.     

Study on physicochemical properties of ionic liquids based on alanine [Cnmim][Ala] (N=2,3,4,5,6)

According to Fukumoto's method, a new series of ionic liquids (ILs) based on alanine, [Cnmim][Ala] ( n=2,3,4,5,6), which comprise 1-alkyl-3-methylimidazolium cation ([Cnmim](+)) and alanine anions ([Ala] (-)), were prepared and characterized. In terms of standard addition method, the density and surface tension of amino acid ILs [Cnmim][Ala] (1-alkyl-3-methylimidazolium alpha-aminopropionic acid salt) were measured in the temperature range 293.15-343.15+/-0.05 K. The volume and surface properties of the ILs [Cnmim][Ala] were discussed. A new method of determining parachor of ionic compound was proposed and was applied to estimate the physicochemical properties of amino acid ionic liquids (AAILs): molecular volume, surface tension, molar enthalpy of vaporization, and thermal expansion coefficient. In comparison with Deetlefs's method of using neutral parachor contribution, the method proposed in this work makes smaller error in estimating properties of AAILs.     

Controllable size, shape and morphology of molybdic acid self-aggregated with rhodamine B to construct functional material

Controllable size, shape and morphology of rhodamine B/molybdic acid (RBMA) aggregates were prepared from a self-aggregation reaction in a molybdic acid and rhodamine B (RhB) coexisting solution. Nanodisks, as well as microcrystal rods and polyhexagonal microcrystal rods, have been obtained in conventional bulk solutions at different temperatures. Large-sized network microcrystal rods and branched fractal aggregates constructed with nanosubunits after the nucleation duration of an ice-water-cooled process have also been achieved under the evaporation-enhanced conditions on glass substrates. The factors affecting the size, shape and morphology of RBMA aggregates including temperature, nucleation and growth, and processing conditions are discussed. The results show that photofunctional molecules (RhB) modified the surface of the molybdic acid particles and influenced their self-aggregation. The temperature and nucleation play key roles in the formation of RBMA aggregates. The structures of RBMA aggregates were characterized by X-ray diffraction, infrared spectra and elemental dispersive spectroscopy. The results indicate that the aggregates show the characteristics of RhB-mediated hydrated ammonium molybdenum bronze with the metastable hexagonal phase. Visible-light-induced electrons transfer reactions in the RBMA aggregates from rhodamine B molecules to MoO3 matrixes were measured by UV-vis spectra and X-ray photoelectron spectra, and the fluorescent image was observed by laser scanning confocal microscopy.     

Frequency-locking phenomena of propagating wave fronts in reaction-diffusion systems

We observe N:(N-1)(N>/=2) frequency-locking phenomena of propagating wave fronts when increasing the light intensity in a spatially extended system. The experiments were carried out using the light-sensitive form of the Belousov-Zhabotinsky reaction with Ru(bpy)(2+)3 as a catalyst. By constructing a mapping function, the characteristic devil's staircase can be reproduced when plotting wave period versus light intensity, in agreement with the experimental data.     

Direct imaging of the alkali metal site in K-doped fullerene peapods

The structure of K-doped fullerene peapods has been investigated by means of high-resolution transmission electron microscopy and electron energy-loss spectroscopy (EELS). It is proven that the potassium atoms can be doped at the intermolecular sites within C60 peapods. The EELS spectrum of potassium (K) L edge clearly exhibits the feature of K+ in the doped peapod and consequently suggests n-type doping. These results encourage the realization of a one-dimensional superconducting wire based on the nanotube peapods.