Amides mass spectrometry

Each methylenethio unit adds three daltons to the peptide weight compared to the parent amide. Mass spectrometry can both confirm the expected mass as well as demonstrate preferred cleavages at both C—S bonds. In a linear pseudopeptide N-terminal or C-terminal fragments allow partial characterization of the location and sequence of the replacement by identification of the fragments using positive and negative ionization, respectively.t56 ... 

However, interpretation of, or even obtaining, the mass spectrum of a peptide can be difficult, and many techniques have been introduced to overcome such difficulties. These techniques include modifying the side chains in the peptide and protecting the N- and C-terminals by special groups. Despite many advances made by these approaches, it is not always easy to read the sequence from the mass spectrum because some amide bond cleavages are less easy than others and give little information. To overcome this problem, tandem mass spectrometry has been applied to this dry approach to peptide sequencing with considerable success. Further, electrospray ionization has been used to determine the molecular masses of proteins and peptides with unprecedented accuracy. 

No systematic study of the mass spectra of pyridopyrazines has been noted, but those of 2,3-dialkyl and 2,3-diaryl derivatives have been recorded 750MS97), and mass spectrometry has been used in the elucidation of problems in the reactions of pyrido[2,3-f ]pyrazines with amide ion (including use of and derivatives) (79JHC305), and of pyrido[2,3-f ]pyrazinium salts with indoles (78ZOR431). The mass spectra of some 1-deazaflavins have been recorded (74JCS(P1)1965). 

Like peptide oligomers, peptoids can be analyzed by HPLC and by mass spectrometry. They can be sequenced by Fdman degradation [13] or by tandem mass spectrometry [14] since, like polypeptides, they conveniently fragment along the main chain amides [15, 16]. 

PLE pressurized liquid extraction, SPE solid phase extraction, UE ultrasonic extraction, DSPE dispersive solid phase extraction, SBSE stir bar sorptive extraction, TD-GC-MS thermal desorption-gas chromatography-mass spectrometry, LAS linear alkylbenzene sulfonates, CDEAs coconut diethanol amides, NPEOs nonylphenol ethoxylates, DP degradation products, SPC sulphenyl carboxylates, PCDD dibenzo-p-dioxins (PCDD), PCDF dibenzofurans, PCBs biphenyls... 

G. Huizing, A. H. Beckett, J. Segura, O. M. Bakke, Metabolism of Clebopride in vitro Mass Spectrometry and Identification of Products of Amide Hydrolysis and V-Debenzylation , Xenobiotica 1980, 10, 211-218. 

M. M. Zhu, D. L. Rempel, M. L. Gross Modeling data from titration, amide H/D exchange, and mass spectrometry to obtain protein—ligand binding constants. J. Am. Soc. Mass Spectrom. 2004, 15, 388-397. 

M.L. Modeling data from titration, amide H/D exchange, and mass spectrometry to obtain protein-ligand binding constants. J. Am. 

Zhang, Z. Smith, D.L. Determination of amide hydrogen exchange by mass spectrometry a new tool for protein structure elucidation. Protein Sd. 1993, 2, 522-531. 

Smith, D.L. Dharmasiri, K. Protein-ligand binding studied by amide hydrogen exchange and mass spectrometry. NATO ASI Ser. C 1998, 510, 45-58. 

Woods, V.L. Jr. Hamuro, Y High resolution, high-throughput amide deuterium exchange-mass spectrometry (DXMS) determination of protein binding site structure and... 

Woods V.L. Jr Dissecting interdomain communication within cAPK regulatory subunit type llbeta using enhanced amide hydrogen/ deuterium exchange mass spectrometry (DXMS). Protein Sci. 

Hamuro Y, Zawadzki K.M., Kim J.S., Stranz D., Taylor S.S., Woods V.L. Jr Dynamics of cAPK type 11b activation revealed by enhanced amide H/2H exchange mass spectrometry (DXMS). J. Mol. Biol. 2003, 327, 1065-1076. 

Zhang Z., Post C.B., Smith D.L. Amide hydrogen exchange determined by mass spectrometry application to rabbit muscle aldolase. Biochemistry 1996, 35, 779—791. 

This partition was determined by mass spectrometry, measuring the N-content of the 6-amino compound 57 and that of the 6-chloropyrimidine 58, formed from 57 on diazotation by action of sodium nitrite in cone, hydrochloric acid. The content in both the 6-amino and the 6-chloro compound is the same, providing clear evidence that in the amino demethoxy-lation under described conditions the Sn(ANRORC) mechanism is the sole operative process. It follows the same pattern as described in previous sections for the aminodehalogenation, i.e., initial addition of the amide ion on position 2 and subsequent ring opening and ring closure (Scheme 11.31). 

Phenylpyrimidine. On treatment of 4-phenylpyrimidine with potassium amide in liquid ammonia at 33°C for 70 hr in the presence of potassium nitrate, followed by quenching the reaction mixture by addition of ammonium chloride and workup, two products were isolated 2-amino-4-phenylpyrimidine (60%) and 6-amino-4-phenylpyrimidine (15%) (79JOC4677). When the reaction was carried out with labeled potassium amide in liquid ammonia and using the combined methodologies of chemical conversions and mass spectrometry as discussed previously (see Section II,C,l,a) it was found that in 6-amino-4-phenylpyrimidine (62/63), hardly any label was incorporated in the ring ( 5%), but that about... 

Twelve volatile acyclic amines and amides (114-120,125-129) (Table VIII) from ponerine ants in the genus Mesoponera have been identified by gas chromatography-mass spectrometry and mass spectral comparison with authentic synthetic samples 41). The major aliphatic amine, A-isoamylnonylamine (114), shows a molecular ion at m/z 213, a-cleavage fragments at miz 156 (M — C4H9)... 

Elemental composition C 52.96%, 0 47.04%. It may be analyzed by treatment with water. The product malonic acid formed may be measured quantitatively by direct injection of aqueous solution into a GC for FID detection. Alternatively, the aqueous solution may be evaporated and the residue may be derivatized to methyl ester and identified by mass spectrometry. Also, the gas may react with ammonia or an amine, and the amide derivative may be identified and quantitatively determined by GC-FID, GC-NPD, GC/MS or infrared techniques. 

Ion pair extraction has also been used to extract polar analytes in bioanalytical procedures. Figure 15.2 exemplifies the determination of the amino acid taurine by gas chromatography-mass spectrometry (GC-MS) this figure also illustrates a useful property of amines (and phenols), which is that they will react more rapidly than water with an acylating reagent in an aqueous environment thus improving their organosolubility. After acylation and ion pair extraction with tetrabutyl ammonium sulphate the taurine is converted to an amide prior to analysis by GC-MS. 

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