Post lipid analysis

MALDI-MS is generally performed at (complex) lipids mixtures, although post-LC-column fractionation systems have been developed as well. Additionally, MALDI-MS imaging of TLC plates is useful technology in Upid analysis [219]. The application of MALDI-MS in lipid analysis and lipidomics has been extensively reviewed [193, 194, 220, 221]. The most widely applied matrices in lipid analysis are DHB and 2,6-dihydroxyacetophenone (DHAP). Unlike in ESI-MS, MALDI-MS provides positive-ion response for all phospholipid classes. Individual components may be observed as [M+H]+, [M+Na], [M+K]+, or adduct ions with additional HWa - or H+/K+-exchange, thus significantly complicating the interpretation and (relative) quantification of individual components in... 

Numerous workers have found that measurements of serum lipase activity are useful in the diagnosis of pancreatitis (83, 84, 85). Despite this, serum lipase determinations are not usually performed in clinical laboratories, probably due to inherent problems associated with the conventional methods, based on an emulsified lipid substrate. The methods are also not very suitable for manual batch analysis nor for automation due to laborious post incubation procedures. 

New insights into the analysis of hydrophobically post-translational modified proteins could be achieved by the construction of lipidated proteins in a combination of bioorganic synthesis of activated lipopeptides and bacterial expression of the protein backbone (Fig. 19). The physico-chemical properties of such artificial lipoproteins differ substantially from those of the corresponding lipopeptides. The pronounced dominance of the hydrophilic protein moiety (e.g., for the Ras protein 181 amino acids) over a short lipopeptide with one or two hydrophobic modifications provides solubility up to 10 4 mol/1, while the biotinylated or fluorescence labeled lipopeptides exhibit low solubility in aqueous solutions and can be applied in the biophysical experiments only in vesicle integrated form or dissolved in organic solvent. 

Reviews appeared on the following subjects Analysis of lipid hydroperoxides , the difficulties encountered for hydroperoxide analysis in a plasma matrix , post-column derivatization after GLC of lipid hydroperoxides and methods for detection and characterization of hydroperoxy groups in oxidized polyolefins . 

Odor-active components in cheese flavor, many of which are derived from milk lipids, can be detected using GC-olfactometry (GC-O). GC-0 is defined as a collection of techniques that combine olfactometry, or the use of the human nose, as a detector to assess odor activity in a defined air stream post-separation using a GC (Friedich and Acree, 1988). The data generated by GC-0 are evaluated primarily by aroma extract dilution analysis or Charm analysis. Both involve evaluating the odor activity of individual compounds by sniffing the GC outlet of a series of dilutions of the original aroma extract and therefore both methods are based on the odor detection threshold of compounds. The key odourants in dairy products and in various types of cheese have been reviewed by Friedich and Acree (1988) and Curioni and Bosset (2002). 

Anonymous. (2006b). Waxes Structure, composition, occurrence and analysis [Online] http /www.lipidlibrary.co.uk/Lipids/waxes/ (posted 20-02-2006 verified 27-02-2006). 

A) Fluorescence/Chemiluminescence Techniques. Lipid hydroperoxides can be reacted with chemiluminescent indicators such as luminol or diphenyl-l-pyrenylphosphine post-HPLC , which allows separation and identification of phospholipid and cholesterol ester peroxides . This technique is applicable to both conjugated and non-conjugated lipids, however it tends to involve a relatively long delay between injection and final fluorescent analysis, and it probably provides inaccurate assessments of total levels of peroxide . ... 

---