Compositional Characterization of Bitumen/Water Emulsion Films by Negative- and Positive-Ion Electrospray Ionization and Field Desorption/Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry
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Abstract:
By means of electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT−ICR MS) and automated field desorption/ionization (FD) FT−ICR MS, we identify nonvolatile nonpolar, polar acidic, and basic water-in-bitumen emulsion film stabilizers. Highly condensed aromatic basic, nonpolar, and acidic asphaltene multilayered films stabilize emulsions near or at critical bitumen concentration for asphaltene flocculation. Solvent diluent added beyond the critical dilution concentration precipitates highly condensed acidic, all basic, and most neutral species from the oil/water interface. The most abundant classes in high bitumen concentration emulsion films include neutral pure hydrocarbons and S, acidic O2 and O2S, and basic N and NS heteroatom classes. Highly abundant low bitumen concentration emulsion film stabilizers include acidic O2, O4, and O3S classes.Keywords:
Asphaltene
In previous work, we demonstrated the use of electrospray ionization to analyze small differences in size or sequence of relatively small polymerase chain reaction (PCR) products of 114 base pairs or less. The sequence information required to answer a biological question may be only a single nucleotide substitution or deletion. In many cases, the regions where these sequence variations can occur are several hundred base pairs in length, and the analysis of large PCR products is therefore desirable. Therefore, we have attempted to expand the size range of PCR products that can be analyzed by electrospray ionization (ESI) Fourier transform ion cyclotron resonance (FTICR) mass spectrometry. Previous work has shown that the difficulties associated with PCR product analysis increase with product size. A revised cleanup scheme was employed to target the removal of detergents with ethanol wash or precipitation steps, followed by additional desalting. Additionally, an in-trap cleanup to collisionally induce dissociation of noncovalent salt adducts was employed. This approach was extended to a 223 base pair PCR product yielding mass measurement accuracy within 26 ppM. The mass measurement accuracy obtained illustrates that a single base substitution could be identified at this size of PCR product with a 7 tesla ESI-FTICR.
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Formation and stabilities of four 14-mer intermolecular DNA triplexes, consisting of third strands with repeating sequence CTCT, CCTT, CTT, or TTT, were studied by electrospray ionization Fourier-transform ion cyclotron resonance mass spectrometry (ESI-FTICR-MS) in the gas phase. The gas-phase stabilities of the triplexes were compared with their CD spectra and melting behaviors in solution, and parallel correlation between two phases were obtained. In the presence of 20 mm NH4+ (pH 5.5), the formation of the TTT triplex was not detected in both solution and the gas phase.
Ion cyclotron resonance
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Electrospray ionization has made possible the transference of non-covalently bound complexes from solution phase to high vacuum. In the process, a complex acquires a net charge and becomes amenable to measurement by MS. FTICR (Fourier-transform ion cyclotron resonance) MS allows these ions to be measured with sufficiently high resolution for the isotopomers of complexes of small proteins to be resolved from each other (true for complexes up to about 100 kDa for the most powerful FTICR instruments), which is of crucial significance in the interpretation of spectra. Results are presented for members of the S100 family of proteins, demonstrating how non-covalently bound complexes can be distinguished unambiguously from covalently bound species. Consideration relevant both to determination of binding constants in solution from the gas-phase results and to the elucidation of protein folding and unfolding in solution are discussed. The caveats inherent to the basic approach of using electrospray and MS to characterize protein complexes are weighed and evaluated.
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Folding (DSP implementation)
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Biomolecule
Non-covalent interactions
Ion cyclotron resonance
Top-down proteomics
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Nano-electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (nano-ESI-FTICRMS) was employed for the analysis of the phytosiderophore 2'-deoxymugineic acid (DMA) and the candidate ligand for the intracellular iron transport in plants nicotianamine (NA). Due to the zwitterionic nature of NA and DMA, complementary mass spectra were obtained in positive and negative ionization modes. The technique was also used for speciation of their complexes with Fe(II) and Fe(III), respectively. The species observed at pH 7.3 are the 1:1 Fe-ligand complexes and no evidence for the existence of dimeric complexes was observed. NA and DMA differ only by one mass unit. Consequently, in the system NA + DMA + Fe(II)/Fe(III), there are pairs of iron species (i.e. NA-Fe(II) and DMA-Fe(III)) with the same nominal mass, which differ only by approximately 0.02 mass units. It is shown that high-resolution MS accompanied by accurate mass data analysis allows the unequivocal identification of all four iron species (NA-Fe(II), NA-Fe(III), DMA-Fe(II), DMA-Fe(III)) in one solution without separation. We also addressed the possible alteration of the oxidation state of chelated iron under nano-ESI conditions, but no redox reactions were observed under optimized conditions.
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Asphaltene,resin and polymer content have a great influence on the stability of emulsion.After obtaining resins and asphaltenes from crude oil by polarity separation,we confect simulated oil emulsion by referring to the crude oil property of SZ 36-1 oilfield. The relationship among asphaltene,resin and polymer content is investigated by orthogonal design method. The increase of whichever asphaltene,resin or polymer content will promote the stability of emulsion under a certain condition. The ratio of asphaltene and resin content also makes significant impact on the stability of emulsion. The synergy between asphaltenes and resins is obvious in the emulsion system. And the influence of this synergy is greater than that of asphaltene content on the stability of emulsion.
Asphaltene
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Complementary base paired complex formation of a thymidine-appended bolaamphiphile with adenosine derivatives was able to be detected with high resolution and high sensitivity in aqueous solutions by electrospray ionization-Fourier-transform ion cyclotron resonance mass (ESI-FTICR MS) spectrometry.
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Electrospray ionization (ESI) coupled with Fourier ion cyclotron resonance mass spectrometry (FTICR MS) has been successfully used for molecular characterization of petroleum. However, ESI can not ionize nonpolar components which generally are dominant in the petroleum fraction. Here, we introduce a novel approach for aromatic compounds molecular characterization. Aromatics in petroleum fractions were ionized to [M + H](+) by positive-ion ESI with HCOONH4 as an ionization promoter, and when ESI is combined with high resolution FTICR MS, aromatic hydrocarbons and heteroatoms in petroleum fractions can be simultaneously analyzed. The method is easily available and has potential for the characterization of aromatic compounds in any other matrix.
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Abstract Formation and stabilities of four 14‐mer intermolecular DNA triplexes, consisting of third strands with repeating sequence CTCT, CCTT, CTT, or TTT, were studied by electrospray ionization Fourier‐transform ion cyclotron resonance mass spectrometry (ESI‐FTICR‐MS) in the gas phase. The gas‐phase stabilities of the triplexes were compared with their CD spectra and melting behaviors in solution, and parallel correlation between two phases were obtained. In the presence of 20 m M NH 4 + (pH 5.5), the formation of the TTT triplex was not detected in both solution and the gas phase. Other triplexes showed the same order, CTCT > CCTT > CTT, of ion abundances in mass spectra and T m values in solution. The more stable triplexes are those that contained higher percentage of C + ·GC triplets and an alternating CT sequence. However, the CCTT with the same C + ·GC triplets as the CTCT showed a higher stability than the latter during the gas‐phase dissociation. Furthermore, a biphasic triplex‐to‐duplex‐to‐single transition was detected in the gas phase, while a monophasic triplex‐to‐single dissociation was observed in solution. The present results reveal that hydrogen bonds and electrostatic interactions dominate in the gas phase, while base stacking and hydrophobic interactions dominate in solution to stabilize the triplexes. Moreover, weak acidic conditions (pH 5–6) promote the formation of the parallel triplexes. Copyright © 2007 John Wiley & Sons, Ltd.
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