Time-of-flight mass spectrometry, MALDI

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... 

Maleamic acid, cyclization of, 293 Maleic anhydride, 59 Maleimido azine, 307 Manganese diacetate catalysts, 71 Mark-Houwink-Sakurada equation, 57 Material safety data sheets (MSDSs), 246 Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS), 385, 388 McGrath, J. E., 327 MDI isomers, 210 MDIs. See Methylene diphenyl diisocyanates (MDIs)... 

Matrix-Assisted Laser Desorption Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF)... 

We have used accurate mass measurements obtained by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOFMS) to differentiate and profile saponins from M. truncatula roots. An example is provided (Fig.3.11) showing the MALDI-TOFMS spectra of a solid-phase extract of M truncatula root tissue. In this spectrum, we can identify multiple saponins. 

Foret et al.98 collected fractions of model proteins and variants of human hemoglobins after fractionation by CIEF, and then analyzed them by matrix-assisted laser desorption-time-of-flight-mass spectrometry (MALDI-TOF-MS). As the authors point out, MS is an orthogonal method to CIEF because it separates according to molecular mass. 

There are at least three possibile ways in which the inhibitor can bind to the active site (1) formation of a sulfide bond to a cysteine residue, with elimination of hydrogen bromide [Eq. (10)], (2) formation of a thiol ester bond with a cysteine residue at the active site [Eq. (11)], and (3) formation of a salt between the carboxyl group of the inhibitor and some basic side chain of the enzyme [Eq. (12)]. To distinguish between these three possibilities, the mass numbers of the enzyme and enzyme-inhibitor complex were measured with matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI). The mass number of the native AMDase was observed as 24766, which is in good agreement with the calculated value, 24734. An aqueous solution of a-bromo-phenylacetic acid was added to the enzyme solution, and the mass spectrum of the complex was measured after 10 minutes. The peak is observed at mass number 24967. If the inhibitor and the enzyme bind to form a sulfide with elimination of HBr, the mass number should be 24868, which is smaller by about one... 

Below we report methodological studies based upon HPLC, GC/FID, GC-MS, LC-MS, matrix-assisted laser desorption ionisation coupled with time-of-flight mass spectrometry (MALDI-ToF/MS), CE, proton nuclear magnetic resonance ( I INMR), RIA and enzymatic colorimetric techniques. 

Specifically, the co-polycondensation reaction of the dihydroxy[2]catenand 50b with the terephthalic acid derivative 47 does not proceed to high molecular-weight but affords preferentially the cyclic oligo[2]catenands 52 with n= 1,2,3 as shown by matrix-assisted time-of-flight mass spectrometry (MALDI-TOFMS) [56]. Besides the high structural flexibility of the dihydroxy[2]catenand 50b, an-... 

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI ToF) for parasite analysis 337... 

They screened seven libraries, each containing 19 peptides of different masses, and found the sequences that bound most tightly to Tom20. Matrix-assisted laser desorp-tion/ionization time-of-flight mass spectrometry (MALDI-TOF MS) served as a readout that allowed the ionized peptides to be observed directly. Using this approach, Kohda and colleagues discovered that the recognition site spans six residues, not the previously established five, and were able to refine sequence preferences further. 

Direct evidence of the existence of organomagnesium compounds with a cluster metal core has been obtained by matrix-assisted laser desorption/ ionizaiton time-of-flight mass spectrometry (MALDI-TOF MS). This method allows one to record the spectra of molecular ions [MH]+ of pro-tonated molecules M. The major advantage of this method is that the use of volatile matrices makes it possible to measure the mass spectra of compounds that hardly transform to the gas phase under other conditions. This is true in full measure for organomagnesium compounds. The method does not provide detailed information on the geometry of corresponding... 

A fast-growing application of the MALDI technique is use in combination with Time-of-Flight mass spectrometry (MALDI-TOF-MS) and has been applied to the determination of molecular weight for biological macromolecules [2-4], Currently, analytes that have molecular weights of <1,000 Da can be analyzed by MALDI-TOF-MS [5-7],... 

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry MALDI-TOF appears the newest technique particularly suitable for the study of oligomers and dendrimers because, under appropriate conditions, the parent peak is obtained uncontaminated by fragmentation species. However, in some cases supramolecular clusters have been observed which could be misinterpre-tated as dimers and higher multiplets [13]. The molecular weight range available reaches 50,000 D with a potential resolution between 0.01 and 0.05%. 

Because of expected electrical, electrochemical, optical, chemo-sensor, and other properties of the ball-type Pcs, several metallo and metal-free ball-type Pcs with different linkers have been reported. Metallo and metal free ball-type Pcs containing four calyx[4]arene units as linkers have been synthesized, Fig. 1 [37], The structures of compounds 1-3 were confirmed by UV-vis, IR, 1II-NMR, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS), and elemental analysis. Because of their unique structure and versatile complexation properties [38], calixarenes were found to be one type of interesting compounds to be incorporated into Pc. The cone conformation of the t-butylcalix[4]arene direct... 

Recently, matrix-assisted laser desorption ioniza-tion/time-of-flight/mass spectrometry (MALDI/TOF/ MS) of intact adducted hemoglobin was explored as a diagnostic tool for the confirmation of exposure to sulfur mustard (23). Multiple alkylated species were observed from incubates of hemoglobin with sulfur mustard however, the methodology has not yet been reported for diagnostic purposes. 

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