Electrospray-Mass Spectrometry ES-MS

Irrespective of the introduction method, an aerosol of microdroplets is generated in the source which then traverses a series of skimmers, encountering a drying gas, the net effect of which is the creation of charged molecular species, devoid of solvent. These gaseous ions, whose charge depends on the number of ionizable groups 

The ionization process in ES-MS is very gentle thus resulting in very few fragment ions and little or no sequence information. To overcome this problem many ES instruments have triple quadrupole analyzers for coUisional activation MS/MS experiments. The first quadrupole is used to select the parent ion, the second is the collision chamber and the third separates the resulting fragment ions. 

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In an attempt to isolate a factor responsible for stimulating hepatocyte growth. Nelson et al. (31) used a PolyHEA column to fractionate an extract of liver by size. The active fraction eluted at a position corresponding to approximately 200 Da the actual molecular weight (electrospray mass spectrometry ES-MS) was 215 Da. The compound of interest proved to be glycerophosphorylethano-lamine. 

FIGURE 5.22 The three principal steps in electrospray mass spectrometry (ES-MS). 

An insight into the equilibria present in solutions of several complexes of the type (R3P)2HgX2 (X = C104, CF3COO) is provided by electrospray mass spectrometry (ES MS) (cf. Section 6.9.2.1.8). 39 In all cases the principal ions [(R3P)2HgX]+ are observed, even if these ions and other ionic constituents of the equilibria are known to be labile on the NMR timescale. In the presence of excess R3P the principal ions [(R3P)3HgX]+ appear. Also fragments of collisionally activated decomposition (CAD, can be influenced and controlled to some extent) are detected, e.g., [(R3P)HgX]+. 

There is another type of reaction with (RSn)i20i4(0H)6 X2 that preserves its structure. Even though no species were isolated, the possible replacement of two /U2-OH, out of six, by methanol has been clearly shown by electrospray mass spectrometry (ES-MS). ... 

The analysis of the metal content in MTs includes determination of the number and nature of the bound metal ions and elucidation of the coordination geometry around the different metal centers enfolded by the polypeptide chain. To this end, optical spectroscopies (UV-Vis, c.d. MCD and luminescence) have played a significant role, despite providing information on the predominant species present in solution. Conversely, electrospray mass spectrometry (ES MS) allows determination of the molecular distribution of the various complex species coexisting within the sample. However, in ES MS, the formation of artifacts due to operational features should not be disregarded. A summary of the techniques more commonly used in the study of the metal-binding features of MTs can be found elsewhere. Additionally, relevant information on the application and possible limitations of the X-ray absorption spectroscopy within the study of MTs has been reported. ... 

Atomic absorption spectrometry (AAS) was established as the most popular gas chromatography (GC) detection technique for lead speciation analysis in the first years of speciation studies. The increase of the residence time of the species in the flame using a ceramic tube inside the flame and, later, the use of electrically heated tubes, made out of graphite or quartz where electrothermal atomization was achieved, provided lower detection limits but still not sufficiently low. Later, the boom of plasma detectors, mainly microwave induced plasma atomic emission (MIP-AES) and, above all, inductively coupled plasma atomic emission and mass spectrometry (ICP-AES and ICP-MS, respectively) allowed the sensitivity requirements for reliable organolead speciation analysis in environmental and biological samples (typically subfemtogram levels) to be achieved. These sensitivity requirements makes speciation analysis of organolead compounds by molecular detection techniques such as electrospray mass spectrometry (ES-MS) a very difficult task and, therefore, the number of applications in the literature is very limited. 

H-Gly-Asp(0 Bu)-Phe-Tyr(PO(OBzl)OH)-Glu(0 Bu)-Ile-Pro-Glu(0 Bu)-Glu(0 Bu)-Ser(PO(OBzl)OH)-I u-NovaSyn TGR was assembled using standard Fmoc SPPS protocols. All acylation reactions were carried out using a 10-fold excess of Fmoc-amino acid activated with TBTU (1 eq) in the presence of HOBt (1 eq) and DIPEA (2 eq). A coupling time of 1 h was used throughout. Cleavage of the peptide from the resin and side-chain deprotection were effected as above. The crude peptide was analysed by HPLC (Figure 2b) and electrospray-mass spectrometry (ES-MS) [expected MH-1456.2, found 1456.1]. 

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