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1.
The kinetic method was applied to differentiate and quantify mixtures of regioisomeric triacylglycerols (TAGs) by generating and mass selecting alkali ion bound metal dimeric clusters with a TAG chosen as reference (ref) and examining their competitive dissociations in a quadrupole ion trap mass spectrometer. This methodology readily distinguished pairs of regioisomers (AAB/ABA) such as LLO/LOL, OOP/OPO and SSP/SPS and consequently distinguished sn-1/sn-3, sn-2 substituents on the glycerol backbone. The dimeric complex ions [ref, Li, TAG(AAB and/or ABA)]+ generated by electrospray ionization mass spectrometry were subjected to collision induced dissociation causing competitive loss of either the neutral TAG reference (ref) leading to [Li(AAB and/or ABA)]+ or the neutral TAG molecule (TAG(AAB and/or ABA)) leading to [ref, Li]+. The ratio of the two competitive dissociation rates, defined by the product ion branching ratio (Riso), was related via the kinetic method to the regioisomeric composition of the investigated TAG mixture. In this work, a linear correlation was established between composition of the mixture of each TAG regioisomer and the logarithm of the branching ratio for competitive fragmentation. Depending on the availability of at least one TAG regioisomer as standard, the kinetic method and the standard additions method led to the quantitative analysis of natural TAG mixtures. 相似文献
2.
Ren C Tzoufras M Tsung FS Mori WB Amorini S Fonseca RA Silva LO Adam JC Heron A 《Physical review letters》2004,93(18):185004
A comprehensive examination of the interaction of a picosecond-long ignition pulse on high-density (40 times critical density) pellets using a two-dimensional particle-in-cell model is described. The global geometry consists of a 50 mum diameter pellet surrounded by a corona which is isolated by a vacuum region from the boundary. For cone-attached targets, as much as 67% of the incident laser energy is absorbed with 12% sent forward as fast electrons in a 23 degrees cone. The current filaments are driven by the Weibel instability of the forward-going fast electron flux and its return current with the ions playing an important role of neutralizing the space charge. No global current filament coalescence has been observed. The electron distribution function obeys a power law, which begins at E approximately 0.2 MeV and falls off as E-(2-3). 相似文献
3.
Sieck L. Wayne Heron John T. Green David S. 《Plasma Chemistry and Plasma Processing》2000,20(2):235-258
Reliable kinetic and thermodynamic data are required to model the evolution of electric discharge or electron-beam decomposition chemistry of gases in humid air streams. In this first segment of a continuing series, we provide a core database describing the initially dominant ion-neutral molecule reactions in humid air plasmas. Recommended reaction rate data and extrapolation tools are presented in a manner to facilitate prediction of reactivities and reaction channels as a function of temperature, pressure, and applied electric field. 相似文献
4.
Gabbutt CD Heron BM Kilner C Kolla SB 《Chemical communications (Cambridge, England)》2010,46(44):8481-8483
Novel, highly coloured benzopentalenonaphthalenones result from a cascade process initiated by the thermally-induced ring-opening of diarylmethanol substituted 2H-naphtho[1,2-b]pyrans in the presence of acid. 相似文献
5.
Gross LC Heron AJ Baca SC Wallace MI 《Langmuir : the ACS journal of surfaces and colloids》2011,27(23):14335-14342
By making dynamic changes to the area of a droplet interface bilayer (DIB), we are able to measure the specific capacitance of lipid bilayers with improved accuracy and precision over existing methods. The dependence of membrane specific capacitance on the chain-length of the alkane oil present in the bilayer is similar to that observed in black lipid membranes. In contrast to conventional artificial bilayers, DIBs are not confined by an aperture, which enables us to determine that the dependence of whole bilayer capacitance on applied potential is predominantly a result of a spontaneous increase in bilayer area. This area change arises from the creation of new bilayer at the three phase interface and is driven by changes in surface tension with applied potential that can be described by the Young-Lippmann equation. By accounting for this area change, we are able to determine the proportion of the capacitance dependence that arises from a change in specific capacitance with applied potential. This method provides a new tool with which to investigate the vertical compression of the bilayer and understand the changes in bilayer thickness with applied potential. We find that, for 1,2-diphytanoyl-sn-glycero-3-phosphocholine membranes in hexadecane, specific bilayer capacitance varies by 0.6-1.5% over an applied potential of ±100 mV. 相似文献
6.
7.
Method development for a quantitative analysis performed without any standard using an evaporative light-scattering detector 总被引:1,自引:0,他引:1
Heron S Maloumbi MG Dreux M Verette E Tchapla A 《Journal of chromatography. A》2007,1161(1-2):152-156
A new method for quantitative analyses using an evaporative light-scattering detector (ELSD) is proposed. It is based on the preliminary determination of the calibration curve of an ELSD which correlates coefficient b and loga, the two coefficients from the equation: A=am(b), that characterize the law of the quantitative response for an ELSD. Dilutions of the mixture to be analyzed allow the determination of coefficient b for each component of the mixture. The knowledge of the b value and the experimental relationship correlating b with loga allows to determine the loga value and consequently to quantify each compound of the mixture. This method is an alternative to the quantitative method which uses an internal normalization without any response coefficient. This internal normalization method used with an ELSD provides inaccurate results and this inaccuracy increases when the analytes are in very different proportions. The relevance of the new method proposed in this work lies in the quantification of all the components present in a complex mixture when some of them are not available as standards. 相似文献
8.
Christopher D. Gabbutt B. Mark Heron Carley Poyner Peter N. Horton 《Tetrahedron》2006,62(47):10945-10953
The oxidation of 3-[bis-(diaryl)methyl]chromones 2 with p-chloranil affords novel acetals, 3-[bis-(diaryl)methylene]-2-methoxychroman-4-ones, 4 through interception of a pyrylium type intermediate. Oxidation of 3-(2-hydroxyphenyl)-4-[bis-(diaryl)methyl]pyrazoles 8, derived from 2 and hydrazines, gave 4,4-diarylbenzopyrano[4,3-c]pyrazoles 15. The electronic absorption spectra of 4 and 15 upon protonation are comparable with those of triarylmethine cationic dyes. 相似文献
9.
Heron AJ Thompson JR Mason AE Wallace MI 《Journal of the American Chemical Society》2007,129(51):16042-16047
We form planar lipid bilayers between an aqueous droplet and a hydrogel support immersed in a lipid-oil solution. By scanning the bilayer over the surface of an SDS-PAGE gel, we are able to directly detect membrane proteins from gels using single-channel recording. Using this technique, we are able to examine low levels of endogenous protein from cell extracts without the need for over-expression. We also use droplet bilayers to detect small molecules from hydrogels. The bilayers show enhanced stability compared to conventional planar lipid bilayers, and both bilayer size and position can be controlled during an experiment. Hydrogel scanning with droplet bilayers provides a new method for the discovery and characterization of ion channels with the potential for high-throughput screening. 相似文献
10.
Simple 2H-chromenes and 2H-thiochromenes form the [2+2]-adducts, tetrahydro[1]benzo(thio)pyrano[3,4-c] [1,2]diazeto[1,2-a][1,2,4]triazoles, with triazolinediones, whereas their 3- and 4-bromo and the corresponding cycloalkylamino derivatives undergo an overall etectrophilic substitution sequence. 相似文献