The spectra recorded by matrix-assisted laser desorption/ionization time-of-flight/time-of-flight tandem mass spectrometry (MALDI-TOF/TOF-MS/MS) of complex carbohydrates from human milk are presented. Besides ions originating from glycosidic cleavages and from sugar ring fragmentations, these spectra show intense peaks that may be assigned to ions produced by three new fragmentation pathways involving a six-atom rearrangement. These ions, together with the A fragments from sugar ring fragmentations, open the possibility of obtaining a complete mapping of the linkage positions present in the carbohydrates investigated by MALDI-TOF/TOF.

In this paper we report matrix-assisted laser desorptionlionization (MALDI) mass spectra of dextrans up to 100 OOO Da molecular weight and compare these measurements with those obtained by conventional sizeexclusion chromatography with low-angle laser light scattering (SEULALLS). These results extend the usefulness of MALDI-MS to higher molecular weight polysaccharides and give some insights into the MALDI process.

The development is described of a rapid, simply and accurate analytical method aimed at evaluating both the presence of cow milk in either raw ewe and water buffalo milk samples employed in industrial processes and the addition of powdered milk to samples of fresh raw milk, using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). The presence of adulteration is defined by evaluating the protein patterns coming from the most abundant whey proteins, alpha-lactalbumin and beta-lactoglobulin, used as molecular markers. As no pretreatment of the milk samples is required and owing to the speed and ease of use of MALDI-MS the proposed analytical protocol can be used as a routine strategy for the identification of possible adulteration of the raw fresh milk samples that the dairy industry receives from producers every day.

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Polyvinylpyrrolidone (PVP) of molecular weight (M w ) 40 000 and 160 000 and polydispersity of 1.8± 2.2 was shown to yield matrix-assisted laser desorption/ionization (MALDI) mass spectra with the correct molar mass distribution of the polymer. This is a unique behavior among widely polydisperse samples and was ascribed to the capacity of PVP to complex the MALDI matrix. This result prompted us to test a new sample preparation technique consisting of flash-freezing followed by freeze-drying of the solution of the polymer with the matrix. In this paper we describe our preliminary results on MALDI-MS of polydisperse polymers obtained by this technique. This sample preparation method allowed us to obtain, for the first time, spectra yielding the true molecular weight distribution of polydisperse samples such as dextran, lichenan, nigeran, and poly(ethylene oxide).