Mass spectroscopy fragmentation

Scheme I. Mass spectroscopy fragmentation pattern of juvenile hormone III [23] (reprinted with kind permission from the American Chemical Society).

Nitrogen-containing fulvalenes have not been systematically studied by mass spectroscopy. Only isolated data for several examples of compounds have been reported. Most of the data consist of electron impact (El) mass spectra recorded for analytical purposes. Only a minor fraction dealt with the characterization of ion structures or focused on the effects of substituents, the ring size of fulvalenes, or the number and arrangement of nitrogen atoms and the fragmentation pathways. 

No discussion of the fragmentation pattern of dithietes by mass spectroscopy has appeared. Only molecular and major fragmentation peaks... 

Mass spectroscopy is a useful technique for the characterization of dendrimers because it can be used to determine relative molar mass. Also, from the fragmentation pattern, the details of the monomer assembly in the branches can be confirmed. A variety of mass spectroscopic techniques have been used for this, including electron impact, fast atom bombardment and matrix-assisted laser desorption ionization (MALDI) mass spectroscopy. 

In comparison to humantenine (15), the structure of which has been confirmed by X-ray diffraction analysis, structure 16 can be assigned to humantenirine with reasonable confidence. The proposed structure is supported by the fragmentation pattern (high-resolution mass spectroscopy and... 

In mass spectroscopy, sample molecules are ionized and the different masses of the ions formed are selected by use of an electric or magnetic field. In its simplest form, a mass spectrometer is an instrument that measures the mass-to-electric charge ratios of ions formed when a sample is ionized. If some of the sample molecules are singly ionized and reach the ion detector without fragmenting, then the mass-to-electric charge ratio of the ions gives a direct measurement of the weight of the molecule (de Hoffmann and Stroobant 2001). 

Results and data gathered on mass spectroscopy of various indole alkaloids have been summarized by Hesse (320). The derivation of the characteristic fragments of indolo[2,3-a]quinolizidines has been interpreted by Gribble and Nelson (321), who investigated C-3, C-5, C-6, C-20, and C-21 deuterated derivatives of octahydroindolo[2,3-a]quinolizine (1). Kametani et al. have observed and proved, with labeled compounds, a methyl transfer from the ester function of reserpine derivatives to the basic nitrogen atom during mass-spectroscopic measurement (322). 

HCV IRES (Table 1, entry 6) A mass spectroscopy-based fragment approach was used to identify the weak binder 29 to the ribosome HA sub-domain of hepatitis C (HCV IRES). Conventional optimisation led to a sub-micromolar lead 30 [41]. 

Mass spectroscopy is useful for qualitative analysis because the signals due to the different mass-to-charge ratios, as seen in the mass spectrum, represent molecular fragments that can be pieced together such that the compound can be identified. 

The presence of a fragment corresponding to the loss of selenium in mass spectroscopy under electronic impact of germaneselone 179 points to a thermal instability of the Ge = Se bond.132 Heating a solution of 179 in benzene at 80°C in the presence of sulfur leads to a chalcogen exchange, likely via the divalent species (ArO)2Ge 141 [Eq. (38)]. 

Williams, D.H. Budzikiewicz, H. Pelah, Z. Djerassi, C. Mass Spectroscopy and Its Application to Structural and Stereochemical Problems. XLIV. Fragmentation Behavior of Monocychc Ketones. Monatsh. Chem. 1964,95,166-177. 

Binding of pyridoxal phosphate to peptide PP-42 also appears to be selective for lysine 30. As was indicated by NMR spectroscopy and UV/vis experiments, only one of three potential lysine Schiff bases appeared to form. To determine the site or sites of attachment, the aldimine peptide intermediates were reduced, proteolytically cleaved, and the fragments analyzed by mass spectroscopy. This... 

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