MALDI-TOF-MS

MALDI-ToF (CID) MS has been used to obtain information on the end-groups and other structural features in polyalkylmethacrylates [61]. 

The transfer of material from a microfluidic chip to the mass spectrometer can be performed on-line or off-line. Typically, a MALDI target is under high vacuum while microchip-based electrophoresis is carried out at atmospheric pressure. This difference in pressure makes on-line transfer a challenge. 

With the on-line approach, the sample is continuously delivered to the vacuum in real time. Off-line sample introduction entails the running of microfluidic processes on the chip with later MS analysis. Therefore, the introduction of samples into the ion source generally requires breaking the ion source vacuum. 

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The molecular weights and molecular weight distributions (MWD) of phenolic oligomers have been evaluated using gel permeation chromatography (GPC),23,24 NMR spectroscopy,25 vapor pressure osmometry (VPO),26 intrinsic viscosity,27 and more recently matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS).28... 

During the past decade, MALDI-TOF MS has proven to be an effective tool for the analysis of oligo- and polymeric mannoglucans (for extensive reviews see [222,223]). SEC/MALDI mass spectrometry was employed in the analysis of hemicelluloses isolated by microwave heat-fractionation from spruce and aspen wood [94]. These methods allowed the separation and characterization of the oligo- and polysaccharide fractions derived from the xylan and mannan components of both woods [224]. 

Scheme 3. J efro-addition of 23 and 24 under MALDI-TOF MS conditions generates the ions of the mono-fullerene adducts of cydo-Ci (25" ) and cydo-C.20 (26" ), respectively [61]...

Initial MALDI-TOF MS indicates that only two of the four bean sites have carbohydrate chains attached (data not shown). 

MALDI-TOF MS Matrix-Assisted Laser Desorption Ionisation... 

Scraping and elution NMR and MALDI-TOF/MS Scraping and elution Immimoassay... 

FIGURE 10.5 (a) MALDI-TOF MS analysis of the apo-form of bovine Cu, Zn superoxide... 

The principle issue relating to the use of MALDI-TOF MS for bacterial characterization is resolving power. This factor has a profound effect in large... 

Waters Corporation has now introduced the MicrobeLynx , a MALDI-TOF MS system developed for fingerprint bacterial ID. The system and its applications are described thus ... 

The focus of this chapter is the development of a technique often called wholecell matrix-assisted laser desorption ionization (MALDI) time-of-flight (TOF) mass spectrometry (MS) or whole-cell MALDI-TOF MS. Some groups prefer to use terms such as intact or unprocessed rather than whole, but the intended meaning is the same regardless of which word is used. As noted in the first chapter of this book, there are many different methods for the analysis of bacteria. However, for the analysis of intact or unprocessed bacteria, whole-cell MALDI-TOF MS is the most commonly used approach. This method is very rapid. MALDI-TOF MS analysis of whole cells takes only minutes because the samples can be analyzed directly after collection from a bacterial culture suspension. Direct MALDI MS analysis of fungi or viruses is similar in approach1,2 but is not covered in this chapter. MALDI-TOF MS of whole cells was developed with very rapid identification or differentiation of bacteria in mind. The name (whole cell) should not be taken to imply that the cells are literally intact or whole. Rather, it should be taken to mean that the cells that have not been treated or processed in any way specifically for the removal or isolation of any cellular components from any others. In whole-cell analysis the cells have been manipulated only as necessary to... 

As noted above, whole-cell MALDI-TOF MS was intended for rapid taxonomic identification of bacteria. Neither the analysis of specific targeted bacterial proteins, nor the discovery of new proteins, was envisioned as a routine application for which whole cells would be used. An unknown or target protein might not have the abundance or proton affinity to facilitate its detection from such a complex mixture containing literally thousands of other proteins. Thus, for many applications, the analysis of proteins from chromatographically separated fractions remains a more productive approach. From a historical perspective, whole-cell MALDI is a logical extension of MALDI analysis of isolated cellular proteins. After all, purified proteins can be obtained from bacteria after different levels of purification. Differences in method often reflect how much purification is done prior to analysis. With whole-cell MALDI the answer is literally none. Some methods attempt to combine the benefits of the rapid whole cell approach with a minimal level of sample preparation, often based on the analysis of crude fractions rather... 

Holland et al. proposed a simpler and faster approach using the protein profile obtained directly from whole cells rather than from cellular extracts or affinity beads.17 This was the first report of the whole-cell MALDI-TOF MS... 

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