69 research outputs found
Lipid fingerprinting of Gram-positive lactobacilli by intact cells - Matrix-assisted laser desorption/ionization mass spectrometry using a proton sponge based matrix
No full textA method of direct lipid analysis by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) in intact membranes, without prior extraction/separation steps, is described. Here, we demonstrate the efficacy of a strong base, 1,8-bis(dimethylamino)naphthalene (DMAN; proton sponge), as a novel matrix for MALDI-time-of-flight (TOF) MS analysis of whole cell bacteria. Initially, individual acidic low-molecular-weight analytes such as standard free fatty acids and phospholipids were analyzed using DMAN as matrix. Clear negative-mode MALDI-TOF MS spectra of all analytes show only deprotonated analyte signals at a low picomole limit of detection with the complete absence of matrix-related signals. These results indicate that DMAN represents a suitable matrix for MALDI-TOF MS analysis of mixtures of complex lipids as the intact membranes of microorganisms. DMAN was successfully applied to the analysis of Lactobacillus sanfranciscensis and L. plantarum microorganisms. Different components were sensitively detected in a single spot, including 16:0, 18:2, 18:3, and 21:0 free acids, glycolipids, phosphatidylglycerols (PGs) and cardiolipins. This method might be of general application, offering the advantage of quickly gaining information about lipid components of other Gram-positive bacterial membranes
1H-pteridine-2,4-dione (lumazine): a new MALDI matrix for complex (phospho)lipid mixtures analysis
No full textNowadays, matrix-assisted laser desorption/ionization (MALDI) time-of-flight mass spectrometry represents an emerging and versatile tool for analysis of lipids. However, direct (i.e., with no previous separation of lipid classes) analysis of crude extracts containing a complex mixture of lipids (a problem typically encountered in shotgun lipidomics) is still a quite challenging task using a conventional MALDI matrix such as 2,5-dihydroxybenzoic acid (DHB). Indeed, in the presence of phospholipids containing quaternary ammonium groups, such as phosphatidylcholines and sphingomyelins, strong ionization-suppression effects are experienced especially in positive ion mode. To overcome this limitation, lumazine (1H-pteridine-2,4-dione) was evaluated as an alternative matrix. Lumazine in the solid state showed an absorption maximum at 350 nm, ionizes/desorbs without appreciable decomposition and extensive cluster formation, and can be used in both ion modes. In positive ion mode, the main species were M(center dot+) and 2M(center dot+) radical cations and cationized species ([M+H](+), [M+Na](+), [M+2Na+2Li-3H](+)). In negative ion mode, the main signals observed were the deprotonated molecular ion and the radical anion. The signal-to-noise ratio for phosphatidylglycerols and phosphatidylethanol-amines using lumazine was almost 1 order of magnitude higher than that observed for DHB. Lumazine was successfully used for MALDI analysis (positive and negative ion modes) of crude lipid extracts of milk, soymilk, and hen egg, where phosphatidylethanolamines, phosphatidylserines, and phosphatidylinositols could additionally be detected
Laser Desorption Ionization Time-of-Flight Mass Spectrometry of Triacylglycerols in Oils
No full textSelected triacylglycerols (TAGs) were directly analyzed on a standard stainless steel target plate by
laser desorption/ionization time-of-flight mass spectrometry (LDI-TOFMS). Sodium and potassium
ion adducts of TAGs were produced, and the thermal desorption/ionization mechanism was
invoked to rationalize the experimental observations. The method permits a simple and fast qualitative
analysis of TAGs. Advantages of this approach relative to matrix-assisted laser desorption/
ionization (MALDI) are simpler sample preparation, lack of need to use a matrix with consequent
absence of matrix interference peaks in the spectra, and potential improvements in shot-to-shot
reproducibility due to the absence of the crystallization step resulting in a more homogenously
deposited sample. The procedure was successfully applied to the determination of TAGs in whole
oils, yielding very fast TAG fingerprints
Solid phase microextraction - liquid chromatography (SPME-LC) determination of chloramphenicol in urine and environmental water samples
No full textA solid phase microextraction—liquid chromatography with ultraviolet detection (SPME-LC-UV) method
for the determination of the antimicrobial agent chloramphenicol was developed. The performances of
three commercially available fibers were compared; the Carbowax/TPR-100 was found to provide the
most efficient extraction. All the aspects influencing the fiber adsorption (extraction time, temperature,
pH, salt addition) and desorption (desorption and injection time, desorption solvent mixture composition)
of the analyte were investigated. The method was eventually applied to the determination of the
drug in both biological (urine) and environmental (tap and sea water) samples. The optimized procedure
required a simple sample pretreatment, isocratic elution, and provided enough sensitivity for the
analyte determination in the considered samples. The investigated linear ranges were 37–1000 ng/ml
(urine), 0.1–10 ng/ml (tap water), 0.3–30 ng/ml (sea water). Within-day and between-days RSD% ranged
between 5.5–6.2 and 8.7–9.0 (urine), 5.1–6.0 and 8.4–8.8 (tap water), 5.4–5.7 and 8.6–8.9 (sea water).
Estimated LOD and LOQ were 37 and 95 ng/ml (urine), 0.1 and 0.3 ng/ml (tap water), 0.3 and 0.7 ng/ml
(sea water)
Development of a direct in‐matrix extraction (DIME) protocol for MALDI‐TOF‐MS detection of glycated phospholipids in heat‐treated food samples
No full textMALDI Mass Spectrometry: A Promising Non-Chromatographic Technique
No full textIn recent years, food safety and quality have become of great importance and have involved more public concern. Food quality is associated to food authentication and adulteration, or food features that include ingredients and/or additives as antioxidants and chemicals used to improve food taste, aroma and colour. Food safety is concerned with food contaminants and residues as pesticides, veterinary drugs, environmental contaminants, food processing and food packaging contaminants.
As a result, demand for the development and the applications of more efficient methodologies to analyze food is significantly growing.
In this perspective, a new discipline named foodomics has been recently introduced which applies advanced ‐omic sciences (genomics, proteomics, lipidomics, etc.) in food and nutrition fields for compound profiling, authenticity, food quality or safety, food bioactivity, toxicity issue and so on. Of course, for foodomics studies, mass spectrometry (MS) is considered an indispensable technique due to its intrinsic features, i.e. high sensitivity, selectivity and throughput. Among MS techniques, Matrix Assisted Laser Desorption Ionization (MALDI) has demonstrated a great potential in fast screening analyses for food quality and safety, since no chromatographic separation is usually needed.
In this chapter, some MALDI MS quality control applications will be presented, based on proteomic and lipidomic approaches or devoted to the individuation of food contaminants
Laser Desorption ionization time-of-flight mass spectrometry of squalene in oil samples
No full textLetter to the Editor. No abstract availabl
Assessment of lectin and HILIC based enrichment protocols for characterization of serum glycoproteins by mass spectrometry
No full textUdgivelsesdato: 2008-Aug-21Protein glycosylation is a common post-translational modification that is involved in many biological processes, including cell adhesion, protein-protein and receptor-ligand interactions. The glycoproteome constitutes a source for identification of disease biomarkers since altered protein glycosylation profiles are associated with certain human ailments. Glycoprotein analysis by mass spectrometry of biological samples, such as blood serum, is hampered by sample complexity and the low concentration of the potentially informative glycopeptides and -proteins. We assessed the utility of lectin-based and HILIC-based affinity enrichment techniques, alone or in combination, for preparation of glycoproteins and glycopeptides for subsequent analysis by MALDI and ESI mass spectrometry. The methods were successfully applied to human serum samples and a total of 86 N-glycosylation sites in 45 proteins were identified using a mixture of three immobilized lectins for consecutive glycoprotein enrichment and glycopeptide enrichment. The combination of lectin affinity enrichment of glycoproteins and subsequent HILIC enrichment of tryptic glycopeptides identified 81 N-glycosylation sites in 44 proteins. A total of 63 glycosylation sites in 38 proteins were identified by both methods, demonstrating distinct differences and complementarity. Serial application of custom-made microcolumns of mixed, immobilized lectins proved efficient for recovery and analysis of glycopeptides from serum samples of breast cancer patients and healthy individuals to assess glycosylation site frequencies
Aniline/a-cyano-4-hydroxycinnamic acid is a highly versatile ionic liquid for matrix-assisted laser desorption/ionization mass spectrometry
No full textThe performance of a matrix-assisted laser desorption/ionization (MALDI) ionic liquid matrix (ILM) consisting of alpha-cyano-4-hydroxycinnamic acid (CHCA) and aniline (ANI) was evaluated to assess whether it could offer possible advantages over conventional matrices. Ultraviolet (UV), Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR) and laser desorption/ionization mass spectrometry (LDI-MS) experiments were carried out with the aim of confirming the structure of the ANI-CHCA ILM. Different model analytes such as amino acids, peptides, proteins, lipids, phospholipids, synthetic polymers, and sugars were tested. Mass spectra with similar or improved signal-to-noise (S/N) ratio (compared to CHCA) were invariably obtained demonstrating the potential of this ILM as a general purpose matrix. Furthermore, protein identification by peptide mass fingerprinting (PMF) and database search was facilitated compared to CHCA since higher scores and increased sequence coverage were observed. Finally, a complex lipid mixture (i.e. a raw extract of a milk sample) analysed by MALDI-MS showed improved S/N ratio, a reduced chemical noise and a limited formation of matrix-clusters
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