Mass Spectrometry as a Tool for the Determination of Heats of Tautomerization of Thioamides in the Gas Phase

2005 ◽  
Vol 11 (1) ◽  
pp. 53-63 ◽  
Author(s):  
P.E. Allegretti ◽  
C.B. Milazzo ◽  
J.J.P. Furlong
Keyword(s):  
Mass Spectrometry ◽  
Gas Phase ◽  
Electron Energy ◽  
Temperature Effects ◽  
Mass Spectra ◽  
Theoretical Calculations ◽  
Neutral Species ◽  
Empirical Results ◽  
Semi Empirical

Tautomerism of several thioamides was studied by mass spectrometry. The analysis of the corresponding mass spectra allowed some fragmentations to be assigned to specific tautomers and heats of tautomerization to be determined through temperature effects and electron energy studies. Experimental determinations were strongly supported by theoretical calculations. AM1 semi-empirical results indicate that the thioamide–thioimidol equilibrium can be studied by mass spectrometry. Also, additional evidence was obtained regarding tautomerism occurrence between neutral species.

Tautomerism of uracil and related compounds: A mass spectrometry study

2017 ◽  
Vol 24 (2) ◽  
pp. 214-224 ◽  
Author(s):  
Diego D Colasurdo ◽  
Matías N Pila ◽  
Dacio A Iglesias ◽  
Sergio L Laurella ◽  
Danila L Ruiz
Keyword(s):  
Mass Spectrometry ◽  
Gas Phase ◽  
Mass Spectra ◽  
Tautomeric Form ◽  
Ion Trap ◽  
Theoretical Calculations ◽  
Ion Trap Mass Spectrometry ◽  
Mass Spectrometry Study ◽  
Related Compounds ◽  
Substituted Uracils

It has been demonstrated that uracil has a preponderant tautomeric form, but it is also known that different tautomers co-exist in this equilibrium. In this work, mass spectrometry is used as a helpful tool to analyse the equilibria, using derivative compounds to forbid the presence of some tautomers and ion trap mass spectrometry to follow relevant fragmentation pathways. Theoretical calculations were performed to confirm tautomers abundance by energy minimization in gas phase. Analysis of mass spectra of uracil, three methyl-substituted uracils, 2-thiouracil and three benzouracils suggest that uracil exists mainly as three tautomers in gas phase: one major structure that corresponds to the classical structure of uracil (pyrimidine-2,4(1H,3H)-dione) bearing two carbonyls and two NH moieties, and two minor enolic forms (4-hydroxypyrimidin-2(1H)-one and 2-hydroxypyrimidin-4(1H)-one). Such tautomeric distribution is supported by theoretical calculations, which show that they are the three most stable tautomers.

scholarly journals Gas-Phase Fragmentation of Cyclic Oligosaccharides in Tandem Mass Spectrometry

Molecules ◽  
2019 ◽  
Vol 24 (12) ◽  
pp. 2226 ◽  
Author(s):  
Alexander O. Chizhov ◽  
Yury E. Tsvetkov ◽  
Nikolay E. Nifantiev
Keyword(s):  
Mass Spectrometry ◽  
Tandem Mass Spectrometry ◽  
Gas Phase ◽  
Structure Elucidation ◽  
Mass Spectra ◽  
Food Additives ◽  
Tandem Mass ◽  
Modern Mass ◽  
Gas Phase Fragmentation ◽  
Different Sources

Modern mass spectrometry, including electrospray and MALDI, is applied for analysis and structure elucidation of carbohydrates. Cyclic oligosaccharides isolated from different sources (bacteria and plants) have been known for decades and some of them (cyclodextrins and their derivatives) are widely used in drug design, as food additives, in the construction of nanomaterials, etc. The peculiarities of the first- and second-order mass spectra of cyclic oligosaccharides (natural, synthetic and their derivatives and modifications: cyclodextrins, cycloglucans, cyclofructans, cyclooligoglucosamines, etc.) are discussed in this minireview.

Mass Spectrometric Behaviour of Carboxylated Polyethylene Glycols and Carboxylated Octylphenol Ethoxylates

2003 ◽  
Vol 9 (3) ◽  
pp. 165-173 ◽  
Author(s):  
Magdalena Frańska ◽  
Agnieszka Zgoła ◽  
Joanna Rychłowska ◽  
Andrzej Szymański ◽  
Zenon Łukaszewski ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Alkali Metal ◽  
Mass Spectra ◽  
Secondary Ion Mass Spectrometry ◽  
Metal Cations ◽  
Mass Spectrometric ◽  
Polyethylene Glycols ◽  
Alkali Metal Cations ◽  
Secondary Ion

The mass spectrometric behaviour of mono- and di-carboxylated polyethylene glycols (PEGCs and CPEGCs) and carboxylated octylphenol ethoxylates (OPECs) is discussed. The tendency for ionisation (deprotonation, protonation and cationisation by alkali–metal cations) of carboxylated PEGs was compared with that of non-carboxylated analogues by using both secondary-ion mass spectrometry (SIMS) and electrospray ionisation (ESI). The fragmentation of the PEGCs and CPEGCs is discussed and also compared with their neutral analogues, PEGs. B/E linked-scan mass spectra were recorded, using secondary-ion mass spectrometry as a method for ion generation, for deprotonated and protonated molecules as well as for molecules cationised by alkali–metal cations. The fragmentation behaviour of PEGs is found to be different from that of CPEGCs, The presence of carboxyl groups may be confirmed not only by the determination of molecular weights of the ethoxylates studied, but also on the basis of the fragment ions formed. The metastable decomposition of the [OPEC-H]− ions proceeds through the cleavage of the bond between the octylphenol moiety and the ethoxylene chain and leads to the octylphenoxyl anions. It permits determination of the mass of the hydrophobic moiety of the studied carboxylated alkylphenol ethoxylate. ESI mass spectra recorded in the negative-ion mode were found to be more suitable than SI mass spectra for the determination of the average molecular weight of carboxylated ethoxylates.

Condensed, solution and gas phase behaviour of mono- and dinuclear 2,6-diacetylpyridine (dap) hydrazone copper complexes probed by X-ray, mass spectrometry and theoretical calculations

2013 ◽  
Vol 42 (32) ◽  
pp. 11497 ◽  
Author(s):  
Brenno A. D. Neto ◽  
Barbara F. L. Viana ◽  
Thyago S. Rodrigues ◽  
Priscila M. Lalli ◽  
Marcos N. Eberlin ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Gas Phase ◽  
Copper Complexes ◽  
Theoretical Calculations ◽  
Phase Behaviour ◽  
X Ray

Mass spectral analysis of acetylated peptides: Implications in proteomics

2019 ◽  
Vol 26 (1) ◽  
pp. 36-45
Author(s):  
Deepika Chandra ◽  
P Gayathri ◽  
Mudita Vats ◽  
R Nagaraj ◽  
MK Ray ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Pseudomonas Syringae ◽  
Mass Spectra ◽  
De Novo ◽  
Spectral Quality ◽  
Tryptic Peptides ◽  
Mass Spectral ◽  
Human Proteins ◽  
Terminal Amino

Sequence determination of peptides using mass spectrometry plays a crucial role in the bottom-up approaches for the identification of proteins. It is crucially important to minimise false detection and validate sequence of the peptides in order to correctly identify a protein. Chemical modification of peptides followed by mass spectrometry is an option for improving the spectral quality. In silico-derived tryptic peptides with different N-terminal amino acids were designed from human proteins and synthesized. The effect of acetylation on the fragmentation of peptides was studied. N-terminal acetylation of the tryptic peptides was shown to form b1-ions, improve the abundance and occurrence of b-ions. In some cases, the intensity and occurrence of some y-ions also varied. Thus, it is demonstrated that acetylation plays an important role in improving the de novo sequencing efficiency of the peptides. The acetylation method was extended to tryptic peptides generated from the proteome of an Antarctic bacterium Pseudomonas syringae Lz4W using the proteomics work flow and mass spectra of the peptides were analysed. Comparison of the MS/MS spectra of the acetylated and unacetylated peptides revealed that acetylation helped in improving the spectral quality and validated the peptide sequences. Using this method, 673 proteins of the 1070 proteins identified were validated.

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