Evaluation of flavonoids binding to DNA duplexes by electrospray ionization mass spectrometry

In this study, electrospray ionization mass spectrometry (ESI-MS) was used to investigate the binding interactions of ten flavonoid aglycones and ten flavonoid glycosides with DNA duplexes. Relative binding affinities of the flavonoids toward DNA duplexes were estimated based on the fraction of bound DNA. The results revealed that the 4'-OH group of flavonoid aglycones was essential for their DNA-binding properties. Flavonoid glycosides with sugar chain linked on ring A or ring B showed enhanced binding toward the duplexes over their aglycone counterparts, whereas glycosylation of the flavonol quercetin on ring C exhibited a less pronounced effect.

Qualitative and semi-quantitative analysis of quaternary alkaloids in Coptis-scute herb couple by Electrospray mass Spectrometry

A practical solution of qualitatively analyzing quaternary alkaloids in coptis-scute herb couple by electrospray ionization mass spectrometry(ESI-MS) was developed. Without the complicated pretreatment of sample, the active ingredients including berberine, palmatine, coptisine, jatrorrhizine, epiberberine, and columbamine were identified and some relative content changing rules of alkaloids in coptis-scute couple were summarized in this article. The overall profiles of the complex extracts were obtained.

Studies on alkaloids binding to GC-rich human survivin promoter DNA using positive and negative ion electrospray ionization mass spectrometry

Electrospray ionization mass spectrometry (ESI-MS) was used to investigate the binding of 13 alkaloids to two GC-rich DNA duplexes which are critical sequences in human survivin promoter. Negative ion ESI-MS was first applied to screen the binding of the alkaloids to the duplexes. Six alkaloids (including berberine, jatrorrhizine, palmatine, reserpine, berbamine, and tetrandrine) show complexation with the target DNA sequences. Relative binding affinities were estimated from the negative ion ESI data, and the alkaloids show a binding preference to the duplex with higher GC content. Positive ion ESI mass spectra of the complexes were also recorded and compared with those obtained in negative ion mode.

Interactions of mitoxantrone with duplex and triplex DNA studied by electrospray ionization mass spectrometry

We have examined interactions between mitoxantrone (MXT) and DNA duplexes or triplexes with different base compositions by using electrospray ionization mass spectrometry (ESI-MS), respectively. MXT interacts preferentially with DNA duplexes compared to the triplexes. In the mass spectrum of the duplex-MXT mixture, the complex peaks dominated in the ratios of duplex/MXT of 1:1, 1:2 and 1:3, and the 1:2 duplex/MXT peak was the most abundant. In contrast, only 1:1 triplex-MXT complexes were observed in the mass spectrum of the triplex-MXT mixture, and the most intensive peak was a free triplex ion without MXT.

A study of the non-covalent interaction between flavonoids and DNA triplexes by electrospray ionization mass spectrometry

The binding interactions of 22 flavonoids (9 aglycones and 13 glycosides) with DNA triplexes were investigated using electrospray ionization mass spectrometry (ESI-MS). The results revealed that the hydroxyl positions of aglycones. the locations and numbers of saccharide, as well as the aglycone skeletons play roles in the triplex-binding properties of flavonoids. The presence of 3-OH, or 3'-OH, or replacement of 4'-OH with methoxy group in aglycones decreased the fraction of bound DNA sharply. Flavonoid glycosides exhibit higher binding affinities towards the DNA triplexes than their aglycone counterparts. Glycosylations of flavones at the 8-C position and isoflavones at the 7-O position show higher binding affinities than those on the other positions of ring A of aglycones. Glycosylation with a disaccharide on 0 position of flavonol results in higher binding affinity than that with monosaccharide. Flexibility of the ring B is favorable for its interaction with DNA triplex. According to sustained off-resonance irradiation collision-induced dissociation (SORI-CID) experiments, glycosylation and non-planarity of flavonoid aglycones lead to different dissociation pathways of the flavonoid/triplex complexes.

Structural elucidation and identification of alkaloids in Rhizoma Coptidis by electrospray ionization tandem mass spectrometry

Simple, convenient, sensitive and accurate analytical methods are needed for the structural characterization and identification of alkaloid components in Rhizoma Coptidis in traditional Chinese herbal medicine, which has important bioactivity. In this work, the identification of alkaloid compounds in Rhizoma Coptidis was investigated by obtaining molecular mass information using electrospray ionization mass spectrometry (ESI-MS). Multi-stage tandem mass spectrometric (ESI-MSn) data for the alkaloid compounds were used for detailed structural characterization, then structure information was obtained by comparison of the fragmentation mechanisms of both alkaloids in Rhizoma Coptidis and standard samples of berberine, palmatine, coptisine and jatrorrhizine by MS. Based on the results obtained, the structure of a novel compound was elucidated. The results of the experiments demonstrate that ESI-MSn is a sensitive, selective and effective tool for the rapid determination of alkaloids in Rhizoma Coptidis.

Analysis of norditerpenoid alkaloids extracted from Aconitum sinomantanum Nakai by electrospray ionization tandem mass spectrometry

Electrospray ionization mass spectrometry (ESI-MS) was applied simultaneously in determining norditerpenoid alkaloids from the roots of Aconitum sinomantanum Nakai ( RAS) based on molecular mass information. The tandem mass spectra (ESI-MSn) provided the alkaloidal structural information, through which the existence of these alkaloids was further confirmed. Accordingly, six known norditerpenoid alkaloids were simultaneously determined on the basis of their ESI-MSn spectra. Furthermore, based on the diagnostic fragmentation pathways of alkaloidal MSn, a rapid method for direct detection and characterization of alkaloids from an ethanolic extract of RAS was described.

Structure identification of five unknown dilipo-alkaloids extracted from processed tuber of Aconitum carmiechaeli by electrospray ionization tandem mass spectrometry

The alkaloids in processed aconite tuber of Aconitum Carmiechaeli were studied, and five novel alkaloids in extract from processed aconite tuber were found. The first step involved the use of electrospray ionization mass spectrometry (ESI-MS), and then multi-stage tandem mass spectrometry (MSn) was used to provide structural information. Based on their MSn spectra, the structures of the five novel compounds were elucidated to be C3,C8-difatty acid esters of mesaconitine, aconitine and 10-hydroxyaconitine.

Evaluation and application of micro-sampling system for inductively coupled plasma mass spectrometry

Two Meinhard microconcentric nebulizers, model AR30-07-FM02 and AR 30-07-FM005, were employed as a self-installed micro-sampling system for inductively coupled plasma-mass spectrometry (ICP-MS). The FM02 nebulizer at 22 muL/min of solution uptake rate gave the relative standard deviations of 7.6%, 3.0%, 2.7%, 1.8% for determinations (n = 10) of 20 mug/L Be, Co, In and Bi, respectively, and the detection limits (3s) of 0.14, 0.10, 0.02 and 0.01 mug/L for Be, Co In and Bi, respectively. The mass intensity of In-115 obtained by this micro-sampling system was 60% of that by conventional pneumatic nebulizer system at 1.3 mL/min. The analytical results for La, Ce, Pr and Nd in 20 muL Wistar rat amniotic fluid obtained by the present micro-sampling system were precisely in good agreement with those obtained using conventional pneumatic nebulization system.

Rapid identification of saponins in plant extracts by electrospray ionization multi-stage tandem mass spectrometry and liquid chromatography/tandem mass spectrometry

Electrospray ionization multi-stage tandem mass spectrometry (ESI-MSn) and liquid chromatography coupled with on-line mass spectrometry (LC/MS/MS) were applied to characterize saponins in crude extracts from Panax ginseng. The MSn data of the [M - H](-) ions of saponins can provide structural information on the sugar sequences of the saccharide chains and on the sapogins of saponins. By ESI-MSn, non-isomeric saponins and isomeric saponins with different aglycones can be determined rapidly in plant extracts. LC/MS/MS is a good complementary analytical tool for determination of isomeric saponins. These approaches constitute powerful analytical tools far rapid screening and structural assignment of saponins in plant extracts. Copyright (C) 2000 John Wiley & Sons, Ltd.

Electrospray ionization mass spectrometry of cyclodextrin complexes with amino acids in incubated solutions and in eluates of gel permeation chromatography

1:1 complexes of beta-cyclodextrin (CD) with three amino acids (Gly, Phe and Trp) have been detected as ions in the gas phase using infusion positive and negative ion electrospray ionization mass spectrometry (ESI-MS). In contrast with the positive ion ESI mass spectra of simple aqueous solutions, the aggregates and adducts usually formed in the ESI process did not appear in the positive ion ESI spectra of solutions buffered with ammonium acetate (NH4Ac), even at higher analyte concentrations, These studies suggest that addition of buffer and/or use of a low analyte concentration should be used to overcome formation of aggregates and metal ion adducts in such mass spectrometry studies. Also, the deprotonated complexes are dissociated by collision induced dissociation (CID) to form an abundant product ion, the deprotonated CD, requiring transfer of a proton to the amino acid carboxyl group, To understand formation of complexes in the gas phase, gel permeation chromatography (GPC) was used to separate free amino acids (AAs) from complexes in an incubated solution. The ESI mass spectra of the GPC fractions show the presence of 1:1 complexes of both CD-aromatic amino acids and CD-aliphatic amino acids. Compared with CD-aliphatic amino acid complexes, CD-aromatic amino acid complexes appear to be destabilized in the gas phase, possibly because the hydrophobic interaction which binds the aromatic group of amino acids in the CD cavity in solution may become repulsive when solvent evaporates from the droplets during the electrospray process, whereas those complex ions formed as proton bound dimers are stabilized by electrostatic forces, the major binding force for such complexes in the gas phase. In addition, the GPC technique coupled with off-line ESI-MS can rapidly separate CD complexes by size, and provides some information on the character of the complexes in solution. (C) 1998 John Wiley & Sons, Ltd.

On-line concentration of proteins in pressurized capillary electrochromatography coupled with electrospray ionization-mass spectrometry

Pressurized capillary electrochromatography (pCEC) and electrospray ionization-mass spectrometry (ESI-MS) have been hyphenated for protein analysis. Taken cytochrome c, lysozyme, and insulin as samples, the limits of detection (LODs) for absolute concentrations are 10(-11) mol (signal-to-noise ratio S/N = 3) with relative standard deviations (RSDs) of retention time and peak area, respectively, of less than 1.7% and 4.8%. In order to improve the detection sensitivity, on-line concentration by field-enhanced sample-stacking effect and chromatographic zone-sharpening effect has been developed, and parameters affecting separation and detection, such as pH and electrolyte concentration in the mobile phase, separation voltage, as well as enrichment voltage and time, have been studied systematically. Under the optimized conditions, the LODs of the three proteins could be decreased up to 100-fold. In addition, the feasibility of such techniques has been further demonstrated by the analysis of modified insulins at a concentration of 20 mu g/mL.

Quantitative determination of compounds in tobacco essential oils by comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry

A quantitative analysis of the individual compounds in tobacco essential oils is performed by comprehensive two-dimensional gas chromatography (GC x GC) combined with flame ionization detector (FID). A time-of-flight mass spectrometer (TOF/MS) was coupled to GC x GC for the identification of the resolved peaks. The response of a flame ionization detector to different compound classes was calibrated using multiple internal standards. In total, 172 compounds were identified with good match and 61 compounds with high probability value were reliably quantified. For comparative purposes, the essential oil sample was also quantified by one-dimensional gas chromatography-mass spectrometry (GC/MS) with multiple internal standards method. The results showed that there was close agreement between the two analysis methods when the peak purity and match quality in one-dimensional GC/MS are high enough. (c) 2005 Elsevier B.V. All rights reserved.

Studies on the persistence of estradiol benzoate and nortestosterone decanoate in hair of cattle following treatment with growth promoters, determined by ultra-high-performance liquid chromatography-tandem mass spectrometry

Measurement of steroid esters in bovine hair samples, using sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS), provides a powerful tool for identifying animals treated illicitly with growth promoters. The successful application of such testing requires appropriate sampling of hair from treated animals. This paper describes the results of hair analysis by LC-MS/MS for two animal studies in which animals were treated with estradiol-3-benzoate and nortestosterone decanoate. The results from the first animal study indicate that animals treated with these anabolic steroids may not always be identified from analysis of hair samples; positive test results occur sporadically and only for some of the treated animals. The results from the second animal study identify conditions attaching to positive hair samples, such as, that concentrations of steroid esters in hair are related to distance of sampling from point of injection and to time post-treatment, that concentrations of steroid esters in hair are related to dose given to the animal but that this relationship may vary over time post-treatment, and that steroid esters may be measured in regrowth hair taken some weeks after treatment. Steroid esters are determined along the length of the hair, confirming that accumulation of steroid esters into hair occurs from various sources, including blood, sweat and sebum. The reported research provides some useful insights into the mechanisms governing the persistence of steroid esters in bovine hair following illicit treatment with growth promoters. (C) 2009 Elsevier B.V. All rights reserved.

Thermodynamical studies of irreversible sorption of CO2 by Wyodak coal

Differential scanning calorimetry (DSC), temperature programmed desorption mass spectrometry (TPD-MS) and small angle neutron scattering (SANS) were used to investigate CO2 uptake by the Wyodak coal. The adsorption of carbon dioxide on Wyodak coal was studied by DSC. The exotherms evident at low temperatures are associated with the uptake of CO2 suggesting that carbon dioxide interacts strongly with the coal surface. The reduction in the value of the exotherms between the first and second runs for the Wyodak coal suggests that some CO2 is irreversibly bound to the structure even after heating to 200 °C DSC results also showed that adsorption of CO2 on the coal surface is an activated process and presumably at the temperature of the exotherms there is enough thermal energy to overcome the activation energy for adsorption. The adsorption process is instantly pursued by much slower diffusion of the gas molecules into the coal matrix (absorption). Structural rearrangement in coal by CO2 is examined by change in the glass transition temperature of coal after CO2 uptake at different pressures. The amount of gas dissolved in the coal increases with increasing CO2 pressure. TPD-MS showed that CO2 desorption from the Wyodak coal follows a first order kinetic model. Increase in the activation energy for desorption with pre-adsorbed CO2 pressure suggests that higher pressures facilitate the transport of CO2 molecules through the barriers therefore the amount of CO2 uptake by the coal is greater at higher pressures and more attempts are required to desorb CO2 molecules sorbed at elevated pressures. These conclusions were further confirmed by examining the Wyodak coal structure in high pressure CO 2 by SANS.