Molecular weight, mass spectral determination

Mass spectral studies play an important role in structure determination in this field. One of the major advantages is that only minute amounts of substrate are required for spectral measurement. Under high resolution conditions the compound s molecular weight can be determined with great accuracy tables are available for translation of this... 

Molecular weight determination by mass spectral analysis... 

Dienes and polyenes show a pronounced molecular ion in the mass spectra and hence the molecular weight of polyenes can be determined by positive ion mass spectra. The easy removal of a 7r-electron from a diene is usually the reason for the distinct M +. The mass spectral investigation of conjugated polyenes is somewhat similar to that of aromatic structures, due to the high stability of the rearranged ions formed after the... 

A thorough search of the reconstructed ion chromatogram (RIC) was made to determine the mass spectra of all detectable components. The spectra were compared with those of reference standards when available or with the spectra from the mass spectral library. Molecular weights of more abundant constituents are shown in Figure b, many additional minor components were also characterized. A complete list of compounds characterized in this sample by GC-MS is given in Table I. 

A variety of tools address the stoichiometry and molecular weight of compounds. The necessary condition that at least two metals be present for multiple metal bond formation is a simple sorting method for initial studies the molecular unit as determined by any type of molecular weight study must correspond to that of at least two metals per molecule. Conductivity measurements supply similar data for ions, and mass spectral data can indicate the presence of at least two metals per molecule. Analytical data with nonintegral ligand-to-metal ratios require that some multiple number of metal centers be present in order to formulate a stoichiometric compound. This array of techniques only eliminates the possibility of metal—metal bonds for mononuclear metal complexes, and further studies are always necessary to confirm the presence of an attractive metal-metal interaction. 

Table X. FAB Mass Spectral Analysis and Molecular Weight Determination of the Series of Purified Diphosphoryl Lipid A Fractions ...

Spegazzinidine (LXIX) was shown by elementary analysis to be C21H28N2O4, the number of hydrogens being confirmed by the mass spectral molecular weight determination. Its UV-spectrum resembles... 

Analysis and mass spectral molecular weight determination established the empirical formula, C21H26N2O3, for stemmadenine (8, 116, 117). Its UV-spectrum was characteristic of an indole (cf. ref. 55), while the IR-spectrum indicated the presence of a normal ester grouping (1718 cm-1) and the absence of any substituent in the indole aromatic ring (116). These findings were fully borne out by NMR-spectroscopy which showed the presence of an indole NH (9.3 S), four aromatic protons, and a carbo-methoxyl methyl singlet (3.79 S). A single vinyl proton quartet (5.4 S)... 

Dihydroperiphylline can be prepared from periphylline (138) by reduction with NaBH3CN (116). The structural differences between the four alkaloids were deduced on the basis of mass spectral molecular weight determination and, of course, H-NMR spectral data. 

It is evident from the discussions above that mass spectrometric method in combination with enzymatic digestion offers a convenient approach to the characterization of GM-CSF and its variants. ESI-MS method demonstrated a mass accuracy of better than 0.01% for a recombinant protein. The mass spectral data of the enzymatic digest of GM-CSF and its variants allow the precise determination of the molecular weights of the peptides, leading to the identification of sites of covalent modifications, the disulfide bonding pattern, and confirmation of the cDNA-derived sequence of the protein. 

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