A method of characterizing polyglycol esters, an important class of industrial polymer, has been developed using electrospray ionization ion trap mass spectrometry (ESI ITMS). The fragmentation behavior of polyglycol esters is found to be different from that of polyglycols whose functional end groups are linked to the polymer chain via ether bonds (i.e., polyglycol ethers). The fragmentation pattern of an oligomer ion generated by low-energy collisioninduced dissociation is strongly dependent on the type of cation used for ionization. It is shown that structural information on the polymer chain and end groups is best obtained by examining the fragment ion spectra of oligomers ionized by ammonium, alkali, and transition metal ions. T andem mass spectrometry using either matrixassisted laser desorption ionization (MALDI) or electrospray ionization (ESI) is being developed as a tool for polymer structural characterization [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. We are particularly interested in characterizing functional polyglycols, including poly(ethylene glycol) (PEG), poly(propylene glycol) (PPG), and their copolymers [12][13][14][15][16][17][18][19]. Structural characterization of this type of polymer is important because polyglycols are widely used in industry with their properties strongly depending on not only molecular weights, but also structures and compositions. Recently, polyglycols have also been increasingly used in biotechnical and biomedical applications such as the development of slow releasing drugs [20,21]. Traditionally, polyglycols were thought to be difficult to fragment in low-energy CID tandem MS. In our recent work, we demonstrated that lithium and transition metal ions could form adduct ions with polyglycol in ESI, and these adduct ions could readily undergo fragmentation [15,16]. The resulting fragment ion spectra were very informative for the structural characterization of polyglycol. Our previous study was focused on alcohol ethoxylates whose end-groups are linked to polyglycol chains via ether-type C™O bonds (i.e., polyglycol ethers). The results generated therein were compared to earlier studies of the same type of polyglycols employing fast atom bombardment (FAB) MS/MS by Latimer and coworkers [22][23][24][25].Poly(ethylene glycol) ester, especially fatty acid methyl ester ethoxylate (FAMEE), is another class of polyglycol which can be used as an alternative to alcohol ethoxylates in many industrial applications. With varying alkyl chain lengths in the fatty acid moiety, a wide range of hydrophilic lipophilic balance (HLB) values can be achieved to suit different applications [14]. They are extensively used as non-ionic bases for cosmetics and pharmaceuticals, non-ionic emulsifiers for vegetable and mineral oils, thickening agents for creams, anti-static agents for plastics, and non-ionic surfactants. Despite active MS study on alcohol ethoxylates [12][13][14][15][16][17][18][19], the literature on ester ethoxylates is scarce [5,16,63].In this work, we report a metho...

A protein mass mapping approach using mass spectrometry (MS) combined with an experimentally derived protein mass database is presented for rapid and effective identification of bacterial species. A prototype mass database from the protein extracts of nine bacterial species has been created by off-line high-performance liquid chromatography (HPLC) matrix-assisted laser desorption/ionization (MALDI) MS, in which the microbiological parameter of bacterial growth time is considered. A numerical method using a statistical weight factor algorithm is devised for matching the protein masses of an unknown bacterial sample against the database. The sum of these weight factors produces a corresponding summed weight factor score for each bacterial species listed in the database, and the database species producing the highest score represents the identity of the respective unknown bacterium. The applicability and reliability of this protein mass mapping approach has been tested with seven bacterial species in a single-blind study by both direct MALDI MS and HPLC electrospray ionization MS methods, and identification results with 100% accuracy are obtained. Our studies have demonstrated that the protein mass database can be rapidly established and readily adopted with relatively less dependency on experimental factors. Furthermore, it is shown that a number of proteins can be detected using a protein sample amount equivalent to an extract of less than 1000 cells, demonstrating that this protein mass mapping approach can potentially be highly sensitive for rapid bacterial identification.