MRM-BEM本征值计算中波数k初始值的预估算法

利用基于多重互易的边界元法计算二维声学谐振腔的本征值和本征频率.通过搜索包含未知波数k的高阶行列式值的0点,来确定系统的本征值.基于波的传播原理,提出一种波数k初始值的粗略估计算法.计算了几种模型的估计算法的效率.研究多重互易边界元法基本解的阶数对结果精度的影响,发现基本解至少采用七重互易结果才收敛.数值结果与解析解和文献符合的很好,证明了方法的有效性和可靠性.     

Analysis of Processing Effects on Glucosinolate Profiles in Red Cabbage by LC-MS/MS in Multiple Reaction Monitoring Mode

Red cabbage (Brassica oleracea L. var. capitata) continues to receive increasing attention on its health-promoting properties because of its high glucosinolate content. Glucosinolates are an unstable active substance; however, there are few studies on their changes in different cooking processes. In this study, we investigated the effects of processing methods (boiling, steaming, microwave heating, frying, stir-frying) and boiling time on glucosinolates in red cabbage. Ten glucosinolates, including 4-methoxyglucobrassicin, neoglucobrassicin, glucoalyssin, glucobrassicin, glucoraphanin, glucoiberin, progoitrin, gluconapin and sinigrin, in red cabbage were detected. Decreases of 32.36%, 24.83%, 25.27%, 81.11% and 84.29% for total glucosinolates were observed after boiling, microwaving, steaming, frying and stir-frying. Indole glucosinolates were more efficiently lost compared to aliphatic glucosinolates after boiling, while microwaving, steaming, frying and stir-frying also resulted in a greater reduction in indole glucosinolates than aliphatic glucosinolates. Glucoalyssin, glucoerucin and sinigrin were more thermal sensitive than other glucosinolates. It was confirmed that microwaving and steaming retained higher levels of glucosinolates than other methods and may be better for cooking red cabbage.     

Advanced separation methods of food anthocyanins,isoflavones and flavanols

In recent years, increasing knowledge of the positive health effects of food polyphenols has prompted the need to develop new separation techniques for their extraction, fractionation and analysis. This article provides an updated and exhaustive review of the application of counter-current chromatography, high performance liquid chromatography, capillary electrophoresis, and their hyphenation with mass spectrometry to the study of food polyphenols. Flavonoids constitute the largest class of polyphenols, widely spread in the plant kingdom and common in human diet which has been the most widely studied with respect to their antioxidant and biological activities. The main subgroups are anthocyanins, catechins, isoflavones, flavonols and flavones. They are reported to exhibit antioxidant, anti-carcinogenic, anti-inflammatory, anti-atherogenic, anti-thrombotic, and immune modulating functions, among others. Since red fruit anthocyanins, soy isoflavones and flavanols from grapes and teas are currently the most used phenolic compounds for producing new nutraceuticals and functional foods, this review is focused on these three flavonoid groups.     

Quantitative structure–ion intensity relationship strategy to the prediction of absolute levels without authentic standards

The lack of authentic standards represents a major bottleneck in the quantitative analysis of complex samples. Here we propose a quantitative structure and ionization intensity relationship (QSIIR) approach to predict the absolute levels of compounds in complex matrixes. An absolute quantitative method for simultaneous quantification of 25 organic acids was firstly developed and validated. Napierian logarithm (LN) of the relative slope rate derived from the calibration curves was applied as an indicator of the relative ionization intensity factor (RIIF) and serves as the dependent variable for building a QSIIR model via a multiple linear regression (MLR) approach. Five independent variables representing for hydrogen bond acidity, HOMO energy, the number of hydrogen bond donating group, the ratio of organic phase, and the polar solvent accessible surface area were found as the dominant contributors to the RIIF of organic acids. This QSIIR model was validated to be accurate and robust, with the correlation coefficients (R²), R² adjusted, and R² prediction at 0.945, 0.925, and 0.89, respectively. The deviation of accuracy between the predicted and experimental value in analyzing a real complex sample was less than 20% in most cases (15/18). Furthermore, the high adaptability of this model was validated one year later in another LC/MS system. The QSIIR approach is expected to provide better understanding of quantitative structure and ionization efficiency relationship of analogous compounds, and also to be useful in predicting the absolute levels of analogous analytes in complex mixtures.     

Optimization of multiple reaction monitoring mode for the trace analysis of veterinary sulfonamides by LC-MS/MS

One of the oldest groups of veterinary chemotherapeutic agents, sulfonamides have been widely used for more than 50 years, thanks to their low cost and their broad spectrum of activity in preventing or treating bacterial infections. Nowadays, those compounds are regularly detected in a wide variety of environmental samples, including natural waters, sediments and soils. Since the environmental concentrations of sulfonamides are usually very low and their occurrence multicomponental, their determination in these matrices still pose significant analytical problems. The present paper describes the optimization of ESI-MS/MS parameters and the chromatographic separation of 12 sulfonamides commonly used in veterinary medicine. The methodology developed in this study, unlike many others, satisfied the requirements of EU Commission Decision 2002/657/EC, which defines the criteria for both screening and confirmatory methods with respect to drug residues on the basis of identification points. Each MRM transition was tested not only for the qualitative but also for the quantitative analysis of sulfonamides. The method was validated for its analytical performance parameters and applied to the determination of those compounds in soil samples.     

Rapid and sensitive identification of ricin in environmental samples based on lactamyl agarose beads using LC‐MS/MS (MRM)

Ricin, a plant‐derived toxin extracted from the seeds of Ricinus communis (castor bean plant), is one of the most toxic proteins known. Ricin's high toxicity, widespread availability, and ease of its extraction make it a potential agent for bioterrorist attacks. Most ricin detection methods are based on immunoassays. These methods may suffer from low efficiency in matrices containing interfering substances, or from false positive results due to antibody cross reactivity, with highly homologous proteins. In this study, we have developed a simple, rapid, sensitive, and selective mass spectrometry assay, for the identification of ricin in complex environmental samples. This assay involves three main stages: (a) Ricin affinity capture by commercial lactamyl‐agarose (LA) beads. (b) Tryptic digestion. (c) LC‐MS/MS (MRM) analysis of tryptic fragments. The assay was validated using 60 diverse environmental samples such as soil, asphalt, and vegetation, taken from various geographic regions. The assay's selectivity was established in the presence of high concentrations of competing lectin interferences. Based on our findings, we have defined strict criteria for unambiguous identification of ricin. Our novel method, which combines affinity capture beads followed by MRM‐based analysis, enabled the identification of 1 ppb ricin spiked into complex environmental matrices. This methodology has the potential to be extended for the identification of ricin in body fluids from individuals exposed (deliberately or accidentally) to the toxin, contaminated food or for the detection of the entire family of RIP‐II toxins, by applying multiplex format.     

A sensitive analysis method for 7 diterpenoids in rat plasma by liquid chromatography-electrospray ionization mass spectrometry and its application to pharmacokinetic study of Isodon serra extract

A simple and sensitive LC-MS/MS method has been developed and validated for the identification and quantification of epinodosin, epinodosinol, nodosin, oridonin, lasiokariurinol, lasiokaurin and rabdoternin A in rat plasma using sulfamethoxazole as the internal standard. The plasma sample pre-treatment consisted of a liquid-liquid extraction. Chromatographic separation was achieved on a C18 column with linear gradient elution using water and methanol, which were both acidified with 0.1% formic acid, at a flow rate of 0.7 mL/min. A tandem mass spectrometric detection was conducted using multiple reaction monitoring (MRM) via an electrospray ionization (ESI) source. A novel multi-determination-periods program was executed to achieve a higher sensitivity by setting five scanning periods. The method presented here utilizes a novel determination strategy, enabling the application of positive and negative ESI-MS in a single run. The optimized mass transition ion-pairs (m/z) for quantitation were 361.2/287.1 for epinodosin, 382.3/347.3 for epinodosinol, 363.3/281.2 for nodosin, 365.3/347.3 for oridonin, 407.3/329.1 for lasiokariurinol, 405.2/59.0 for lasiokaurin, 363.2/283.1 for rabdoternin A and 254.1/156.0 for IS. The total run time was 20.50 min (including 5 min equilibration time) between injections. The specificity, linearity, accuracy, precision, recovery, matrix effect and several validation results demonstrate that this method is sensitive, specific and reliable. The proposed method was further applied to investigate the pharmacokinetics of all analytes after a single oral administration of Isodon serra extract to rats.     

A Multi-Omics Study of Human Testis and Epididymis

The human testis and epididymis play critical roles in male fertility, including the spermatogenesis process, sperm storage, and maturation. However, the unique functions of the two organs had not been systematically studied. Herein, we provide a systematic and comprehensive multi-omics study between testis and epididymis. RNA-Seq profiling detected and quantified 19,653 in the testis and 18,407 in the epididymis. Proteomic profiling resulted in the identification of a total of 11,024 and 10,386 proteins in the testis and epididymis, respectively, including 110 proteins that previously have been classified as MPs (missing proteins). Furthermore, Five MPs expressed in testis were validated by the MRM method. Subsequently, multi-omcis between testis and epididymis were performed, including biological functions and pathways of DEGs (Differentially Expressed Genes) in each group, revealing that those differences were related to spermatogenesis, male gamete generation, as well as reproduction. In conclusion, this study can help us find the expression regularity of missing protein and help related scientists understand the physiological functions of testis and epididymis more deeply.     

Quantitative analysis of low-abundance serological proteins with peptide affinity-based enrichment and pseudo-multiple reaction monitoring by hybrid quadrupole time-of-flight mass spectrometry

Multiple reaction monitoring (MRM) is commonly used for the quantitative analysis of proteins during mass pectrometry (MS), and has excellent specificity and sensitivity for an analyte in a complex sample. In this study, a pseudo-MRM method for the quantitative analysis of low-abundance serological proteins was developed using hybrid quadrupole time-of-flight (hybrid Q-TOF) MS and peptide affinity-based enrichment. First, a pseudo-MRM-based analysis using hybrid Q-TOF MS was performed for synthetic peptides selected as targets and spiked into tryptic digests of human serum. By integrating multiple transition signals corresponding to fragment ions in the full scan MS/MS spectrum of a precursor ion of the target peptide, a pseudo-MRM MS analysis of the target peptide showed an increased signal-to-noise (S/N) ratio and sensitivity, as well as an improved reproducibility. The pseudo-MRM method was then used for the quantitative analysis of the tryptic peptides of two low-abundance serological proteins, tissue inhibitor of metalloproteinase 1 (TIMP1) and tissue-type protein tyrosine phosphatase kappa (PTPκ), which were prepared with peptide affinity-based enrichment from human serum. Finally, this method was used to detect femtomolar amounts of target peptides derived from TIMP1 and PTPκ, with good coefficients of variation (CV 2.7% and 9.8%, respectively), using a few microliters of human serum from colorectal cancer patients. The results suggest that pseudo-MRM using hybrid Q-TOF MS, combined with peptide affinity-based enrichment, could become a promising alternative for the quantitative analysis of low-abundance target proteins of interest in complex serum samples that avoids protein depletion.     

Presence of virgin olive oil phenolic metabolites in human low density lipoprotein fraction: determination by high-performance liquid chromatography-electrospray ionization tandem mass spectrometry

The biological benefits of olive oil in preventing the oxidation of low density lipoprotein (LDL) would seem to be linked to its high monounsaturated fatty acid contents, but also to its respective phenolic compounds contents. One prerequisite to assess the in vivo physiological significance of phenolic compounds is to determine their presence in human LDL following the ingestion of virgin olive oil.In this work, olive oil phenolic metabolites were identified using high-performance liquid chromatography in tandem with electrospray mass spectrometry (HPLC-ESI-MS/MS) detection, after solid phase extraction (SPE). Quantitative methods were developed in carrying out linearity, precision, sensitivity and recovery tests. The results from two methods of LDL separation were compared and shorter LDL isolation procedure showed a better recovery for antioxidants compounds in LDL. The metabolites identified in LDL were: hydroxytyrosol monoglucuronide, hydroxytyrosol monosulfate, tyrosol glucuronide, tyrosol sulfate and homovanillic acid sulfate. The fact that olive oil phenolic metabolites are able to bind LDL strengthens claims that these compounds act as in vivo antioxidants.