ESI mass spectrometry

DNA sequencing and. 1113 Electrospray ionization (ESI) mass spectrometry, 417-418 Electrostatic potential map, 37 acetaldehyde, 688 acetamide, 791,922 acetate ion. 43. 53, 56, 757 acetic acid. 53. 55 acetic acid dimer, 755 acetic anhydride, 791 acetone, 55, 56. 78 acetone anion, 56 acetyl azide, 830 acetyl chloride, 791 acetylene. 262 acetylide anion, 271 acid anhydride, 791 acid chloride, 791 acyl cation, 558 adenine, 1104 alanine, 1017 alanine zwitterion, 1017 alcohol. 75 alkene, 74, 147 alkyl halide, 75 alkyne. 74... 

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

ESI mass spectrometry ive mass spectrometry ESR spectroscopy set EPR spectroscopy ethyl acetate, chain transfer to 295 ethyl acrylate (EA) polymerizalion, transfer constants, to macromonomers 307 ethyl methacrylate (EMA) polymerization combination v.v disproportionation 255, 262 kinetic parameters 219 tacticity, solvent effects 428 thermodynamics 215 ethyl radicals... 

More recently, Kim et al. synthesized dendritic [n] pseudorotaxane based on the stable charge-transfer complex formation inside cucurbit[8]uril (CB[8j) (Fig. 17) [59]. Reaction of triply branched molecule 47 containing an electron deficient bipyridinium unit on each branch, and three equiv of CB[8] forms branched [4] pseudorotaxane 48 which has been characterized by NMR and ESI mass spectrometry. Addition of three equivalents of electron-rich dihydrox-ynaphthalene 49 produces branched [4]rotaxane 50, which is stabilized by charge-transfer interactions between the bipyridinium unit and dihydroxy-naphthalene inside CB[8]. No dethreading of CB[8] is observed in solution. Reaction of [4] pseudorotaxane 48 with three equiv of triply branched molecule 51 having an electron donor unit on one arm and CB[6] threaded on a diaminobutane unit on each of two remaining arms produced dendritic [ 10] pseudorotaxane 52 which may be considered to be a second generation dendritic pseudorotaxane. 

Electron impact ionisation (El) stands for extensive fragmentation, but also produces molecular ions. The other ionisation methods shown in Table 6.10 mainly generate quasi-molecular ions for various compound classes. Protonation of organic compounds is one of the most fundamental processes of Cl, FAB and ESI mass spectrometry. Apart from electrospray (ESI), which... 

ESI mass spectra of mixtures are difficult to interpret, because each component produces ions with many different charge states. The most direct and reliable method to solve this problem is to use high-resolution MS and calculate the charge states by measuring the spacing of the isotope peaks. ESI mass spectrometry of (polymeric) mixtures with broad molecular weight distribution benefits from a prior separation that reduces the polydispersity of the analyte. 

Two variations on the analysis of PCR products by ESI mass spectrometry have emerged (1) direct-injection MS and tandem mass spectrometry (MS-MS) and (2) liquid chromatography-mass spectrometry (LC-MS) and tandem mass spectrometry (LC-MS/MS). In the former approach, the sample is cleaned manually, and as noted above, the cleanup is performed as simply and rapidly as possible. In the latter approach, the cleanup is done automatically... 

Figure 2 Distribution of silicate species present in supernatant solution of silicalite-1 in NH4OFI at 190°C as a function of their size according to ESI-mass spectrometry.

ESI mass spectrometry has been used to probe the activation of 5a with MAO in THF and has shown the presence of both a four coordinate [2,6- (2,6-t-Pr2CsH3) N=CMe 2C5H3N]FeMe+ cation and an iron hydride species [2,6- (2,6-t-Pr2C6H3) N=CMe 2C5H3N]FeH+ [106], Using low Fe/MAO ratios, the activation reaction of... 

Han, X. and Gross, R.W. Global analysis of cellular lip-idomes directly from crude biological samples by ESI mass spectrometry a bridge to lipidomics. /. Lipid Res. 44 1071-1079, 2003. 

Ermer, for example, utilized LCQ to monitor impurity profiles of various batches of ramorelix used in toxicological studies, clinical stndies and scale-up. Ramorelix is a synthetic glycosylated decapeptide with monoisotopic of 1530.7. The toxicological batch served as the benchmark against which all other batches were compared. Molecnlar weights of impurities were determined by ESI mass spectrometry, and nsed in conjunction with UV peak area % to gauge impurities in batches nsed in clinical trials. These impurity profiles were compared to those of batches used in the toxicologically qualified batch. Eour impurities were detected with the same value. They were believed to be diastereoisomers of ramorelix, i.e., a peptide sequence with one of the amino acids in the opposite enantiomeric form. 

Negative-ion ESI mass spectrometry has been employed to investigate the mechanisms of the synthesis of the heterobimetallic clusters [((THF)Li)2(MeZn)2(OBu-f)4] (24), [((THF)2K)2(MeZn)2(OSiMe3)4l (25) and [K(MeZn)3(OBu-t)4] (26) in solution". Compounds 24-26 possess distorted heterocubane skeletons Li2Zn204, K2Zn204 and KZn304, respectively. 

Mass spectrometry has played a role in biochemistry since the early 1940s when it was introduced for use in following isotopic labels during metabolism.199-20 However, it was not until the 1990s that suitable commercial instruments were developed to permit mass spectrometry using two new methods of ionization. The techniques are called matrix-assisted laser desorption / ionization time-of-flight (MALDI-TOF) and electrospray ionization (ESI) mass spectrometry. 

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