A New Synthetic Method for the Preparation of N,N-Dimethylformamide DI-Tert-Butyl Acetal

A new synthetic method for the preparation of N,N-dimethylformamide di-tert-butyl acetal by acid catalyzed transacetalization of readily available N,N-dimethylformamide dimethyl acetal is described.     

Reaction of t-butyl lithium with (±)-3-methoxy-N-chloromorphinan

Preparation of (±)-3-methoxy-16-t-butylmorphinan ( 4 ) by reaction of t-butyl lithium with (±)-3-methoxy-N-chloromorphinan ( 1 ) is described. The structure of 4 was confirmed by X-ray crystallography.     

Synthesis and stereochemistry of rac.-trans-tetrahydro-6-hydroxy-7-(4-methoxyphenyl)-1,4-thiazepin-5(2H)-one

The base catalyzed reaction of 2-aminoethanethiol ( 3 ) with trans-3-(p-methoxyphenyl)glycidate ( 4 ) gave a mixture of isomeric lactams 5 and 6 , and in addition, a by-product 7 . The structures of these isomers were proven by X-ray crystallography. The data revealed that both isomers adopt the chair conformation in the solid state and the size of the heterocyclic ring in compound 5 is a six- and in compound 6 is a seven-membered ring.     

Grafting of montmorillonite nano‐clay with butyl acrylate and methyl methacrylate by atom transfer radical polymerization: Blends with poly(BuA‐co‐MMA)

11‐(2‐Bromo‐2‐methyl)propionyl‐oxy‐undecyl trichlorosilane atom transfer radical polymerization (ATRP) initiator was covalently attached on montmorillonite clay platelets via silylation reactions. The initiator clay was used to polymerize butyl acrylate (BuA) and methyl methacrylate (MMA) on the clay surface. Polymerization was performed in bulk monomer solution or in DMSO. Polymer modified clay was mixed with a poly(BuA‐co‐MMA) matrix. Small angle X‐ray scattering (SAXS) and transmission electron microscopy (TEM) showed that clay modified in DMSO gave exfoliated composites when mixed with the matrix copolymer. Mechanical properties of the composites were studied by dynamic mechanical thermal analysis (DMTA). The results showed that the mechanical properties were improved as a function of clay content, as well with an increasing homogeneity of the nanocomposite. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3086–3097, 2009     

Vehicle vibrating on a soft compacting soil half-space: Ground vibrations, terrain damage, and vehicle vibrations

The point of departure of the present work may be either an interest in vehicle vibrations themselves, or in ground vibrations and terrain damage due to vehicles traveling off-road. The vibrations of a vehicle traversing dry, soft terrain, which is either rough or undulating, may be significantly modified by the dynamic interaction of the vehicle with the soil, particularly due to losses of energy by soil compaction and as elastic waves. The present work provides a prediction methodology for both vehicle and soil vibrations, accounting for the effects mentioned above. An expedient linear method is compared to a rheologically-based non-linear method. In the linear method, the soil compaction is incorporated as a loss factor in the dynamic stiffness of the otherwise elastic half-space; the imaginary part of that dynamic stiffness already includes the effects of wave damping. The non-linear model treats the compaction using a general rheological model for soils exhibiting both viscous and thixotropic effects, and requires iterative solution. A key feature of the latter model is the hypothesis that the stress distribution may be approximately regarded as quasi-static when calculating compaction losses; that approximation is expected to hold at low frequencies, since the P-wavelength in the soil is then much greater than the dimensions of the zone in which most compaction occurs. The methods predict that the soil compaction and excited ground vibrations have maxima at the vehicle bounce and hop resonances, and at high frequencies at which the Rayleigh wavelength approaches the order of the contact patch diameter. Moreover, sufficiently soft, compactable soils, but fully realizable in nature, control the vehicle response at the hop resonance, and possibly also at the bounce resonance.     

Application of multidimensional affinity high-performance liquid chromatography and electrospray ionization liquid chromatography-mass spectrometry to the characterization of glycosylation in single-chain plasminogen activator initial results

Preliminary results are presented using a combination of affinity chromatography, reversed-phase HPLC and electrospray ionization mass spectrometry to produced peptide maps for N-linked, O-linked and non-glycosylated peptides from an endoproteinase LysC digest of DSPA1, a recombinant DNA derived glycoprotein. Although the system was used to identify a number of major N-linked structures, notably complex biantennary structures attached to asparagine 362, no O-linked glycopeptides from the possible 4 attachment sites were identified. The system did, however, demonstrate the feasibility of the approach and the applicability of the instrumental system.     

Investigation of the antibacterial mechanism of aflatoxins in the BioArena system

The influence of monomethylated basic amino acids [NG-monomethyl-L-arginine (MMA) and Nepsilon-monomethyl-L-lysine (MML)] and ozone capturers (indigo carmine, d-limonene) on the antibacterial effect of the mycotoxins aflatoxins B1, B2, G1 and G2 was studied in BioArena, which is a complex bioautographic system especially suitable for investigating biochemical interactions. In the presence of the formaldehyde precursors MMA or MML, the antibacterial-toxic activity of all the aflatoxins against the phytopathogenic bacterium Pseudomonas savastanoi pv. phaseolicola was enhanced dose-dependently. Indigo carmine and d-limonene, in appropriate concentrations, decreased the inhibition zones of aflatoxins. These results support the original idea that HCHO and its derivative 03 may be involved in the antibacterial activity of aflatoxins and so, potentially, in their known toxic effect.     

Kinetics of the exchange reactions between Gd(DTPA)2-, Gd(BOPTA)2-, and Gd(DTPA-BMA) complexes, used as MRI contrast agents, and the triethylenetetraamine-hexaacetate ligand

The kinetics of ligand exchange reactions occurring between the Gd(DTPA), Gd(BOPTA), and Gd(DTPA-BMA) complexes, used as contrast agents in MRI, and the ligand TTHA, have been studied in the pH range 6.5-11.0 by measuring the water proton relaxation rates at 25 °C in 0.15 M NaCl. The rates of the reactions are directly proportional to the concentration of TTHA, indicating that the reactions take place with the direct attack of the H(i)TTHA((6-i)-) (i = 0, 1, 2 and 3) species on the Gd(3+) complexes, through the formation of ternary intermediates. The rates of the exchange reactions of the neutral Gd(DTPA-BMA) increase when the pH is increased from 6.5 to 9, because the less protonated H(i)TTHA((6-i)-) species can more efficiently attack the Gd(3+) complex. The rates of the exchange reactions of [Gd(DTPA)](2-) and [Gd(BOPTA)](2-) also increase from pH 8.5 to 11, but from 6.5 to 8.5 an unexpected decrease was observed in the reaction rates. The decrease has been interpreted by assuming the validity of general acid catalysis. The protons from the H(i)TTHA((6-i)-) species (i = 2 and 3) can be transferred to the coordinated DTPA or BOPTA in the ternary intermediates when the dissociation of the Gd(3+) complexes occurs faster. The kinetic inertness of Gd(DTPA), Gd(BOPTA), and Gd(DTPA-BMA) differs very considerably; the rates of the ligand exchange reactions of Gd(DTPA-BMA), thus the rates of its dissociation, are 2 to 3 orders of magnitude higher than those of Gd(DTPA) and Gd(BOPTA). The rates of the ligand exchange reactions increase with increasing concentration of the endogenous citrate, phosphate, or carbonate ions at a pH of 7.4, but the effect of citrate and phosphate is negligible at their physiological concentrations. The increase in the reaction rates at the physiological concentration of the carbonate ion is significant (20-60%), and the effect is the largest for the Gd(DTPA-BMA) complex.     

Surface initiated polymerization of a cationic monomer on inner surfaces of silica capillaries: Analyte separation by capillary electrophoresis versus polyelectrolyte behavior

[2‐(Methacryloyl)oxyethyl]trimethylammonium chloride was successfully polymerized by surface‐initiated atom transfer radical polymerization method on the inner surface of fused‐silica capillaries resulting in a covalently bound poly([2‐(methacryloyl)oxyethyl]trimethylammonium chloride) coating. The coated capillaries provided in capillary electrophoresis an excellent run‐to‐run repeatability, capillary‐to‐capillary and day‐to‐day reproducibility. The capillaries worked reliably over 1 month with EOF repeatability below 0.5%. The positively charged coated capillaries were successfully applied to the capillary electrophoretic separation of three standard proteins and five β‐blockers with the separation efficiencies ranging from 132 000 to 303 000 plates/m, and from 82 000 to 189 000 plates/m, respectively. In addition, challenging high‐ and low‐density lipoprotein particles could be separated. The hydrodynamic sizes of free polymer chains in buffers used in the capillary electrophoretic experiments were measured for the characterization of the coatings.