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Effect of Alkyl Substitution at the Amide Nitrogen on Amide Bond Cleavage: Electrospray Ionization/Surface‐induced Dissociation Fragmentation of SubstanceP and Two Alkylated Analogs
Author(s) -
Nair Hari,
Somogyi Árpád,
Wysocki Vicki H.
Publication year - 1996
Publication title -
journal of mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 1076-5174
DOI - 10.1002/(sici)1096-9888(199610)31:10<1141::aid-jms402>3.0.co;2-n
Subject(s) - chemistry , amide , alkylation , protonation , fragmentation (computing) , electrospray ionization , bond cleavage , dissociation (chemistry) , collision induced dissociation , stereochemistry , mass spectrometry , medicinal chemistry , photochemistry , tandem mass spectrometry , ion , organic chemistry , catalysis , computer science , chromatography , operating system
Doubly protonated substance P and two analogs alkylated at the ninth position was studied to determine the effect of N‐alkylation of the amide nitrogen on the electrospray ionization/surface‐induced dissociation (ESI/SID) fragmentation pattern. Thermal decomposition experiments and ab initio calculations were also used in conjunction with the ESI/SID experiments. The increase in relative abundances of the product ions resulting from the cleavage of the amide bond at the alkylation site (relative to the corresponding cleavage for substance P) can be explained by the increased basicity of the amide nitrogen in the context of the ‘mobile proton’ model. The relative abundances of singly charged b ions suggest a rearrangement of the amide hydrogen located N‐terminal to the bond cleaved.