Dopant-assisted atmospheric pressure chemical ionization (dAPCI) is a soft ionization method rarely used for gas chromatography-mass spectrometry (GC-MS). The current study combines GC-dAPCI with tandem mass spectrometry (MS/MS) for analysis of a complex mixture such as lignin pyrolysis analysis. To identify the structures of volatile lignin pyrolysis products, collision-induced dissociation (CID) MS/MS using a quadrupole time-of-flight mass spectrometer (QTOFMS) and pseudo MS/MS through in-source collision-induced dissociation (ISCID) using a single stage TOFMS are utilized. To overcome the lack of MS/MS database, Compound Structure Identification (CSI):FingerID is used to interpret CID spectra and predict best matched structures from PubChem library. With this approach, a total of 59 compounds were positively identified in comparison to only 22 in NIST database search of GC-EI-MS dataset. This study demonstrates the effectiveness of GC-dAPCI-MS/MS to overcome the limitations of traditional GC-EI-MS analysis when EI-MS database is not sufficient.
The HgX1(B) states were excited by photodissociation of HgX2 by a powerful VUV xenon laser. Saturation of the photodissociation process produces very short excitation pulses and has enabled accurate measurements of radiative lifetimes and collisional quenching rate with argon and xenon to be made. 相似文献
The reaction of sodium 2-amino-3-cyanoquinoline-4-carboxylate and 2-methyl-3-cyanoquino-line-4-carboxylic acid in polyphosphoric acid led to 2-amino- and 2-methylquinoline-3,4-dicar-boximide, respectively. Both of these compounds undergo imide N-alkylation reactions with methyl iodide and various chloroalkylaminodialkyl amines, while the latter also condenses with 3,4-dichlorobenzaldehyde to form styryl derivatives. Although some of these compounds may be considered structural analogs of the antimalarial 4-quinolinemethanols, none exhibited antimalarial activity. 相似文献
The capability of assembling biomotors onto specific locations of solid substrates is a key for development of biomotor-based nanomechanical systems. We developed a method to direct the assembly of the heavy meromyosin fragment from rabbit skeletal muscle myosin onto specific locations of Au substrates utilizing surface molecular patterns. In this strategy, chemically directed patterns of streptavidin were achieved to direct highly specific assembly of biotinylated heavy meromyosin on the substrates--a strategy applicable for patterning a variety of biotinylated molecules--while BSA was utilized to avoid nonspecific adsorption. In vitro motility assays of filament sliding were used to confirm functionality of assembled actomyosin. 相似文献
Structural relaxation in different epoxy-anhydride and epoxy-diamine resins has been investigated by differential scanning calorimetry using annealing and cooling rate experiments. The annealing experiments lead to the determination of enthalpy loss,H, at an equivalent annealing temperatureTa=Tg-20, and for periods of annealing time, ta, between 1 h and 4 months. The variation ofH with logta, defines a relaxation rate per decade,rrpd, which is very sensitive to changes of the epoxy network. The cooling rate experiments allow the determination of the apparent activation energy,h*. The effect of the degree of crosslinking, the addition of a reactive diluent, which acts as flexibilizer, and the length of cross-link onrrpd and h* was studied.Financial support has been provided by DGICYT (Project no.PB93/1241). The authors are grateful to CIBA-GEIGY for supplying the epoxies and hardeners, and to HUNTSMAN CORPORATION EUROPE for supplying the JEFFAMINE*, J.M.H. wishes to acknowledge assistance for a sabbatical period from theMinisterio de Education y Ciencia. 相似文献
The use of an optical cavity containing a stimulated Brillouin scattering (SBS) phase-conjugate reflector to control the spatial and spectral output of a long pulse (>100 ns) X-ray preionized XeCl laser is reported. The divergence of the 3×4 cm2 output beam has been improved by a factor of 20 to <150 rad. The temporal form of the output depends on the acoustic decay times of the liquid and gaseous SBS media used. Four-wave mixing via gain saturation has been observed within the discharge volume, leading to depolarisation of the output beam. 相似文献