Mass spectrometry carboxylic acids

Mass Spectrometry Aside from a peak for the molecular ion which is normally easy to pick out aliphatic carboxylic acids undergo a variety of fragmentation processes The dominant fragmentation m aromatic acids corresponds to loss of OH then loss of CO... 

Mass Spectrometry A prominent peak m the mass spectra of most carboxylic acid derivatives corresponds to an acyhum ion derived by cleavage of the bond to the car bonyl group... 

The coordination of [Me2Sn(IV)f to captopril (cap) [(2S)-l-[(2S)-2-methyl-3-sulfanyl propanoyl]pyrrolidine-2-carboxylic acid] in aqueous solution was studied by means of pH-metric titration, electrospray mass spectrometry, H NMR, and Mossbauer spectroscopies in the 2-11 pH range. The results obtained proved that only monomeric complexes are formed in solution. In the acidic pH... 

C[bicarbonate] and mass spectrometry were used to demonstrate the formation of carboxylic acids during the sulfidogenic mineralization of naphthalene and phenanthrene (Zhang and Young 1997). 

Johnson S.K., Houk L.L., Johnson D.C., and Houk R.S., Determination of small carboxylic acids by capillary electrophoresis with electrospray-mass spectrometry. Anal. Chim. Acta, 389, 1, 1999. 

Seifert, W.K. Teeter, R.M. Preparative Thin-layer Chromatography and High Resolution Mass Spectrometry of Crude Oil Carboxylic Acids, Anal. Chem. 1969, 41, 786. 

F.O. Giilagar, A. Buchs, A. Susini, Capillary gas chromatography mass spectrometry and identification of substituted carboxylic acids in lipids extracted from a 4000 year old Nubian burial, Journal of Chromatography, 479, 61 72 (1989). 

Note Trimethylsilylether (TMS) derivatives are frequently employed to vola-tize alcohols, [14,203] carboxylic acids, [204,205] and other compounds [206,207] for mass spectrometry, and for GC-MS applications in particular. The El mass spectra of TMS derivatives exhibit weak molecular ion peaks, clearly visible [M-CHa]" signals and often [Si(Me)3], m/z 73, as the base peak. 

Breindahl T, Andreasen K. 1999. Determination of 11-nor-delta9-tetrahydrocannabinol-9-carboxylic acid in urine using high-performance liquid chromatography and electrospray ionization mass spectrometry. J Chromatogr B Biomed Sci Appl 732 155. 

Peters R, Hellenbrand J, Mengerink Y, Wal Van der S. 2004. On-line determination of carboxylic acids, aldehydes and ketones by high-performance liquid chromatography-diode array detection-atmospheric pressure chemical ionization mass spectrometry after derivatization with 2-nitrophenylhydrazine. J Chromatogr A 1031 35. 

Tai SS, Welch MJ. 2000. Determination of ll-nor-delta9-tetrahydrocannabinol-9-carboxylic acid in a urine-based standard reference material by isotope-dilution liquid chromatography-mass spectrometry with electrospray ionization. J Anal Toxicol 24 385. 

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... 

Amine-terminated, full-generation PAMAM and PPI dendrimers, as well as carboxylate-terminated half-generation PAMAM dendrimers, can directly bind metal ions to their surfaces via coordination to the amine or acid functionality. A partial hst of metal ions that have been bound to these dendrimers in this way includes Na+, K+, Cs+, Rb+, Fe +, Fe +, Gd +, Cu+, Cu +, Ag+, Mn +, Pd, Zn, Co, Rh+,Ru +,andPt + [18,19,27,36,54,82-96]. Tuxro et al.have also shown that the metal ion complexes, such as tris(2,2 -bipyridine)ruthenium (Rulbpylj), can be attached to PAMAM dendrimer surfaces by electrostatic attraction [97]. A wide variety of other famihes of dendrimers have also been prepared that bind metal ions to their periphery. These have recently been reviewed [3]. Such surface-bound metal ions can be used to probe dendrimer structure using optical spectroscopy, mass spectrometry, and electron paramagnetic resonance (EPR) [86-88,90,97-99]. 

Desferrimaduraferrin is a Fe " complexing metabolite of Actinomadura madurae 185). It consists of salicylic acid, p-Ala, Gly, L-Ser and 77 -hydroxy-77 -methyl-L-Om, with the latter incorporated in a heterocyclic system (Fig. 4, 13). From the same species the madurastatin group was obtained 136). The main representative A1 shows the sequence salicylic acid, o-azaridine carboxylic acid, L-Ala, p-Ala, 77 -hydroxy-77 -methyl-Om, L-cOHOm (Fig. 4, 14). In A2 the azaridine ring is opened giving a Ser residue, A3 is an isomer of the open form with the salicylic acid bound to the hydroxy group of Ser. B1 and B2 are the precursors A-salicyloyl-azaridine carboxylic acid and A-salicyloyl-Ser. The madurastatin species A1 forms a 1 1 Fe " complex as shown by mass spectrometry. 

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