MALDI-TOF spectrometry

Some synthetic aspects of the above cyclodehydrogenation reaction are truly remarkable (1) MALDI-TOF spectrometry proves that, indeed, 108 hydrogens... 

Another example of a Pc-based 1-D polymer is that reported by Armstrong and co-workers [158], They prepared a Pc with eight styrene-type polymerizable sites at the end of the peripheral substituents. This molecule forms highly ordered, rod-like aggregates at the air-water interface that can be transferred onto solid supports. Irradiation of the thin films affords polymerization between the olefin moieties of adjacent molecules by photostimulated [2 + 2] cycloaddition. The rod-like Pc macromolecules were conveniently studied by matrix-assisted laser desorp-tion/ionization (MALDI-TOF) spectrometry and atomic force microscopy (ATM), the latter showing rods with lengths up to 290 nm. 

The use of mass spectrometry (MS) techniques to monitor SP reactions has recently become possible through the use of matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) spectrometry (137) after in situ cleavage of a small number of resin beads (138-140). Although the compound is cleaved from the resin, the cleavage happens directly onto the center of the MALDI target and the method can be considered on-bead. 

Several assays have been patented for mutation detection these are mainly designed for single-nucleotide polymorphism (SNP) analysis and use MALDI-TOF spectrometry (Invader , Sequazyme-PinPoint assay, MassARRAY , GOOD assay) all of which use PCR amplification, or require a high DNA concentration in the sample (Invader ). 

Figure 11.25 Mass spectrometric sequencing of oligosaccharides. Carbohydrate-cleaving enzymes were used to release and specifically cleave the oligosaccharide component of the glycoprotein fetuin from bovine serum. Parts A and B show the masses obtained with MALDI-TOF spectrometry as well as the corresponding structures of the oligosaccharide-digestion products (using the same scheme as that in Figure 11.18) ...

The residue from step 2 above is collected by filtration at the water pump washed with water and dried in a vacuum oven at 40°C. The material has a number average degree of polymerization of about 7 by MALDI-TOF spectrometry and NMR (see Chapter 1). 

Rokicki, G. and Kowalczyk, Synthesis of Oligocarbonate Diols and Their Characterization by MALDI-TOF Spectrometry, Polymer, 41, 9013, 2000. 

MALDI-TOF spectrometry Matrix-assisted laser desorption ionization-time of... 

DBU), l,5-diazabicyclo[4.3.0]non-5-ene (DBN), and N, N-dimethylaminopyridine (DMAP) afforded polyether diols containing BPA moiety.It was shown by MALDI-TOF spectrometry and and NMR spectroscopies that the product obtained from 4-tcrt-butylphenol and PC at 150 °C contained some amount of oligomers with carbonate linkages. The authors suggested that phenols were ionized by an organic base to form an active phenol anion which attacked cyclic carbonate monomer to generate intermediate ions that could farther capture proton and react with phenol itself to yield polyether or poly(ether-carbonate). 

For the reaction catalyzed by (salen) CrCl in the presence of n-Bu4N N3 as the initiator, both MALDI-TOF spectrometry and infrared spectroscopy revealed an azide end-group in the... 

The use of MALDI (Matrix-Assisted Laser Desorption Ionization) equipped with a time of flight (TOP) spectrometer offers an elegant and effective method for the precise and absolute determination of polymer molar masses. Initially designed for the characterization of biomolecules, MALDI-TOF spectrometry is now extensively applied to synthetic polymers in this technique the polymer to be studied is dispersed in an organic matrix that is volatilized under the effect of a laser radiation whose wavelength is in the absorption range of the matrix. Owing to the specific molecular interactions between polymer and matrix—which plays an important role in the chain desorption—each polymer requires a suitable matrix. For example, 1,8,9-trihydroxyanthracene is well suited to poly(methyl methacrylate). 

Major groove (DNA), 1104-1105 Malate, from fumarate, 221-222 MALDI-TOF mass spectrometry, 417-418... 

Two relatively new techniques, matrix assisted laser desorption ionization-lime of flight mass spectrometry (MALDI-TOF) and electrospray ionization (FS1), offer new possibilities for analysis of polymers with molecular weights in the tens of thousands. PS molecular weights as high as 1.5 million have been determined by MALDI-TOF. Recent reviews on the application of these techniques to synthetic polymers include those by Ilantoif54 and Nielen.555 The methods have been much used to provide evidence for initiation and termination mechanisms in various forms of living and controlled radical polymerization.550 Some examples of the application of MALDI-TOF and ESI in end group determination are provided in Table 3.12. The table is not intended to be a comprehensive survey. 

Table 3.12 Application of MALDI-TOF or ESI Mass Spectrometry to Polymers Prepared by Radical Polymerization...

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... 

Mandal and Hay28 used MALDI-TOF mass spectrometry to determine the absolute molecular masses and endgroups of 4-phenylphenol novolac resins prepared in xylene or chlorobenzene. Peaks with a mass difference of 44 (the molecular weight of a xylene endgroup) suggested that reactions conducted in xylene included some incorporation of xylene onto the chain ends when a strong acid such as sulfuric acid was used to catalyze the reaction. By contrast, no xylene was reacted into the chain when a milder acid catalyst such as oxalic acid was used. No chlorobenzene was incorporated regardless of the catalyst used. 

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]. 

Sanders (14) has exploited the strong and selective coordination of phosphine donor groups to Ru(II) to construct hetero-dimetallic porphyrin dimers (17, Fig. 5). An alkyne-phosphine moiety introduced on the periphery of a free base or metalloporphyrin (M = Zn or Ni) spontaneously coordinates to a Ru(II)(CO) porphyrin when the two porphyrins are mixed in a 1 1 ratio. Coordination is characterized by a downfield shift of the 31P resonance (A<531P = 19 ppm). There is no evidence of self-coordination of the zinc porphyrin at 10 6 m in toluene, there is no shift in the Soret band in the UV-Vis absorption spectrum. The Ni-Ru dimer was observed by MALDI-TOF mass spectrometry. Heating the Ru(II)CO porphyrin with 2 equivalents of the phosphine porphyrins led to quantitative formation of trimeric assemblies. 

Figure 2.4. Peptide fingerprinting by MALDI-TOF mass Spectrometry. Proteins are extracted and separated on by 2D gel electrophoresis. A spot of interest is excised from the gel, digested with trypsin, and ionized by MALDI. The precise mass of proteolytic fragments is determined by time-of- flight mass spectrometry. The identity of the protein is determined by comparing the peptide masses with a list of peptide masses generated by a simulated digestion of all of the open reading frames of the organism.

Current proteomics studies rely almost exclusively on 2D gel electrophoresis to resolve proteins before MALDI-TOF or ESI-MS/MS approaches. A drawback of the 2D gel approach is that it is relatively slow and work intensive. In addition, the in-gel proteolytic digestion of spots followed by mass spectrometry is a one-at-a-time method that is not well suited for high throughput studies. Therefore, considerable effort is being directed towards alternate methods for higher throughput protein characterization. 

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