Lipids play important roles in biological systems; they store energy, play a structural role in the cell membrane, and areinvolved in cell growth, signal transduction, and apoptosis. Phospholipids (PLs) in particular have received attention in the medical andlipidomics research fields because of their involvement in human diseases such as diabetes, obesity, atherosclerosis, and many cancersassociated with lipid metabolic disorders. Here I review experimental strategies for PL analysis based on nanoflow liquid chromatography-electrospray ionization-tandem mass spectrometry (nLC-ESI-MSn). In particular, discussed are lipid extraction methods, nanoflowLC separation of PLs, effect of ionization modifiers on the ESI of PLs, influence of chain lengths and unsaturation degree of acyl chainsof PLs on MS intensity, structural determination of the molecular structure of PLs and their oxidized products, and quantitative profilingof PLs from biological samples such as tissue, urine, and plasma in relation to cancer and coronary artery disease.
Thermal ionization mass spectrometry (TIMS) was used to determine the concentration and isotope ratio of uraniumcontained in samples of soil and groundwater collected from Korea. Quantification of uranium in ground water samples was performedby isotope dilution mass spectrometry. A series of chemical treatment processes, including chemical separation usingextraction chromatography, was applied to the soil samples to extract the uranium. No treatments other than filtration wereapplied to the groundwater samples. Isotopic analyses by TIMS showed that the isotope ratios of uranium in both the soil andwater samples were indistinguishable from those of naturally abundant uranium. The concentration of uranium in the groundwatersamples was within the U.S. acceptable standards for drinking water. These results demonstrate the utility of TIMS for monitoringuranium in environmental samples with high analytical reliability.
Liquid chromatography based mass spectrometry (LC-MS) is a key technology for analyzing highly complex anddynamic proteome samples. With highly accurate and sensitive LC-MS analysis of complex proteome samples, efficient dataprocessing is another critical issue to obtain more information from LC-MS data. A typical proteomic data processing starts withprotein database search engine which assigns peptide sequences to MS/MS spectra and finds proteins. Although several searchengines, such as SEQUEST and MASCOT, have been widely used, there is no unique standard way to interpret MS/MS spectraof peptides. Each search engine has pros and cons depending on types of mass spectrometers and physicochemical properties ofpeptides. In this study, we describe a novel data process pipeline which identifies more peptides and proteins by correcting precursorion mass numbers and unifying multi search engines results. The pipeline utilizes two open-source software, iPE-MMRfor mass number correction, and iProphet to combine several search results. The integrated pipeline identified 25% more proteinsin mouse epididymal adipose tissue compared with the conventional method. Also the pipeline was validated using controland colitis induced colon tissue. The results of the present study shows that the integrated pipeline can efficiently identifyincreased number of proteins compared to the conventional method which can be a breakthrough in identification of a potentialbiomarker candidate.
An advanced and reliable high performance liquid chromatography (HPLC)/ultraviolet detector (UV)/ion-trap timeof-flight (IT-TOF) mass spectrometry was developed for the simultaneous quantification of 19 marker compounds in Bangpoong-tong-sung-san (BPTS), a traditional oriental prescription. Various parameters affecting HPLC separation and IT-TOFdetection were investigated, and optimized conditions were identified. The separation was achieved on a Capcell PAK C18 column(1.5 mm × 250 mm, 5 μm particle size) using a gradient elution of acetonitrile and water containing 0.1% formic acid at aflow rate of 0.1 mL/min. The column temperature was maintained at 40oC and the injection volume was 2 μL. IT-TOF systemwas equipped with an electrospray ion source (ESI) operating in positive or negative ion mode. The optimized electrospray ionizationparameters were as follows: ion spray voltage, +4.5 kV (positive ion mode), or -3.5 kV (negative ion mode); drying gas(N2), 1.5 L/min; heat block temperature, 200oC. Automatic MSn (n = 1~3) analyses were carried out to obtain structural informationof analytes. Elemental compositions and their mass errors were calculated based on their accurate masses obtained from aformula predictor software. The marker compounds in BPTS were identified by comparisons between MSn spectra from standardsand those from extracts. Moreover, the libraries of MS2 and MS3 spectra and accurate masses of parent and fragment ionsfor marker compounds were constructed. The developed method was successfully applied to the BPTS extracts and identified 17out of 19 marker compounds in the BPTS extracts.
A solid phase extraction (SPE) method was optimized for the quantitative analysis of perfluorooctanoic acid (PFOA)in serum using hydrophilic-lipophilic balance SPE and LC-MS/MS. Fetal bovine serums spiked with 13C8-PFOA before or afterSPE were used as test samples for evaluation of the SPE efficiency. Simultaneous evaluation of matrix effects and absolute SPErecovery for 13C8-PFOA in serum using different sample pre-treatments and SPE conditions allowed optimization of SPE processefficiency with minimal matrix effect and decent SPE recovery. Introduction of protein precipitation as a sample pre-treatmentprocedure for serum samples before SPE generally decreased matrix effect in LC-MS/MS analysis and provided morestable recovery of PFOA.