This article is available online at http://www.jlr.org ing in cell membranes. Specifi c functions and variations of the various phospholipids (PL), the most abundant lipids in eukaryotic cell membranes, are, however, still poorly understood ( 1 ). A diversity of PL in a fi nely balanced equilibrium is used by cells to construct stable and functional membranes, and PL composition determines most of the physico-chemical cell membrane properties such as fl uidity, permeability and thermal phase behavior ( 2 ).Knowledge of the function of lipids within the cell has benefi ted from the development of increasingly sensitive and selective analytical techniques, particularly those based on mass spectrometry ( 3, 4 ). Among these techniques, matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) ( 5 ) has been very successful in studies of the compositions of lipids and other crucial biological molecules. MALDI-MS has allowed direct analysis of complex and unfractionated samples, such as the study of peptide profi les below the level of a single cell ( 6 ). In lipidomics, MALDI-MS has provided fast and simple acquisition of mass spectra with lipid profi les of cells, tissues and body fl uids ( 7 ).MALDI-MS lipid fi ngerprinting can, for example, help studies aimed at understanding the effect of membrane lipid composition on cell membrane behavior after temperature changes. This knowledge is essential for cryopreservation studies of a variety of cells, including oocytes The double molecular layer of polar lipids is a marvelous architectural feature of exquisite biological engineerThis work was supported by the Brazilian research foundations FAPESP (Grant 2008/10756-7) and CNPq.
Using easy ambient sonic-spray ionization mass spectrometry (EASI-MS), fast and non-destructive fingerprinting identification and aging of ballpoint pen ink writings have been performed directly from paper surfaces under ordinary ambient conditions. EASI-MS data obtained directly from the ink lines showed that pens from different brands provide typical ink chemical profiles. Accelerated ink aging has also been monitored by EASI-MS revealing contrasting degradation behaviors for six different common ink dyes. As demonstrated for Basic Violet 3, some dyes display a cascade of degradation products whose abundances increase linearly with time thus functioning as 'chemical clocks' for ink aging. Analysis of questionable documents has confirmed the ink aging capabilities of EASI-MS. The order of superimposition at a crossing point has also been determined by EASI-MS. For two superimposed ink lines, continuous EASI-MS analysis has also shown that the EASI spray is able to penetrate through the layers and therefore both ink layers could be characterized.
The use of mass spectrometry to identify recombinant proteins that are expressed in total soluble proteins (TSPs) from plant extracts is necessary to accelerate further processing steps. For example, the method consists of TSP sample preparation and trypsin digestion prior to the preliminary characterization using nanoUPLC-MS(E) analysis of the recombinant proteins that are expressed in TSP samples of transgenic soybean seeds. A TSP sample as small as 50 μg can be effectively analyzed. In this study, transgenic soybean seeds that expressed recombinant cancer testis antigen (CTAG) were used. The procedure covered 30% of the protein sequence and was quantified at 0.26 ng, which corresponded to 0.1% of the TSP sample. A comparative proteomic profile was generated by the comparison of a negative control and sample that showed a unique expression pattern of CTAG in a transgenic line. The experimental data from the TSP extraction, sample preparation and data analysis are discussed herein.
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