Reactions of protonated diamino acids in the gas phase

Weinkam, Robert J.

doi:10.1021/jo00407a007

Cited by 20 publications

(30 citation statements)

References 5 publications

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“…Figure (c) shows almost exclusive loss of water from the peptide, which is presumed to result from the formation of a lactam. The enhanced loss of water from ornithine has been observed previously and has been ascribed to ring size effects. CID of the water loss product in Fig.…”

Section: Resultssupporting

confidence: 67%

The ornithine effect in peptide cation dissociation

McGee

McLuckey

2013

J. Mass Spectrom.

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Facile cleavage C-terminal to ornithine residues in gas phase peptides has been observed and termed the ornithine effect. Peptides containing internal or C-terminal ornithine residues, which are formed from deguanidination of arginine in solution, were fragmented to produce either a y-ion or water loss, respectively, and the complementary b-ion. The fragmentation patterns of several peptides containing arginine were compared to those of the ornithine analogues. Conversion of arginine to ornithine results in a decrease of the gas phase proton affinity of the residue, thereby increasing the mobility of the ionizing proton. This alteration allows the nucleophilic amine to facilitate a neighboring group reaction to induce a cleavage of the adjacent amide bond. The selective cleavage at the ornithine residue is proposed to result from the highly favorable generation of a six-membered lactam ring. The ornithine effect was compared with the well-known proline and aspartic acid effects in peptide fragmentation using angiotensin II, DRVYIHPF and the ornithine analogue, DOVYIHPF. Under conditions favorable to either the aspartic acid (i.e. singly protonated peptide) or proline effect (i.e. doubly protonated peptide), the ornithine effect was consistently observed to be the more favorable fragmentation pathway. The highly selective nature of the ornithine effect opens up the possibility for conversion of arginine to ornithine residues to induce selective cleavages in polypeptide ions. Such an approach may complement strategies that seek to generate non-selective cleavages of the related peptides.

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Section: Resultssupporting

confidence: 67%

The ornithine effect in peptide cation dissociation

McGee

McLuckey

2013

J. Mass Spectrom.

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“…Noncovalent adducts, such as proton-bound dimers, decompose metastably by parallel losses of one or the other of the components with the relative abundances being determined by each component's proton affinity [41]. Covalent ions, on the other hand, fragment by low-energy rearrangements and simple-cleavage reactions, leading often to the losses of small, stable molecules such as H 2 0 , NH 3 , and CO 2 [42]. The abundance of product relative to precursor ion is generally lower than those from CA of loosly bound adducts.…”

Section: Free-radical Coupling To Give Molecules and Ionsmentioning

confidence: 99%

Origins and structures of background ions produced by fast-atom bombardment of glycerol

Caldwell

Gross

1994

J. Am. Soc. Mass Spectrom.

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Accurate mass measurements were used to assign elemental compositions and tandem mass spectrometry was used to characterize the peak-at-every-mass background ions produced by kiloelectron-volt-particle bombardment of neat fast-atom bombardment matrices. The majority of the background ions observed in the mass spectrum of neat glycerol was identified. On the basis of the experiments with glycerol, a theory for the formation of background ions is presented. Results are discussed according to the chemical and physical changes that ygoe;on-volt-particle bombardment produces in the matrix.

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“…As previously suggested, dehydration of the ions in question can only be accomplished by the nitrogen site addition product (as in 7a). After proton transfer from the positively charged nitrogen atom [48] of the ring-opened [M + 13]+ ion, simple cleavage of the oxygen-carbon single bond gives a primary carbocation (Scheme V). This product can either be stabilized by interaction with the lone pair of electrons on the nitrogen atom or continue to react.…”

Section: Loss Of Water Generally the Dehydration Of The [M +mentioning

confidence: 99%

“…The favorability of the carbon-oxygen bond. cleavage after proton transfer presumably depends on the degree of assistance from a nearby electron-d.onating substituent [48]. Interaction between the nitrogen atom and the nascent positive charge stabilizes the transition state and facilitates the dehydration reaction.…”

Section: Loss Of Water Generally the Dehydration Of The [M +mentioning

confidence: 99%

An investigation of site-selective gas-phase reactions of amino alcohols with dimethyl ether ions

Eichmann

Brodbelt

1993

J. Am. Soc. Mass Spectrom.

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The reactions of dimethyl ether ions with neutral amino alcohols were examined in both a quadrupole ion trap mass spectrometer and a triple quadrupole mass spectrometer. These ion-molecule reactions produced two types of ions: the protonated species [M+l](+) and a more complex product at [M+13](+). The abundance of the [M+13](+) ions relative to that of the [M+1](+) ions decreases with increasing formal interfunctional distance. Multistage collision-activated dissociation techniques were used to characterize the [M+13](+) product ions, their reactivities, and the mechanisms for their formation and dissociation. In addition, molecular semiempirical calculation methods were used to probe the thermochemistry of these reactions. Reaction at the amino alcohol nitrogen site is favored, and the resulting [M+13](+) addition products may cyclize for additional stabilization. Comparisons were made among the behavior of related compounds, such as alcohols, diols, amines, and diamines. The alcohols reacted only to form the protonated species, but the diols, amines, and diamines all formed significant amounts of [M+13](+) ions or related dissociation products.

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Reactions of protonated diamino acids in the gas phase

Cited by 20 publications

References 5 publications

The ornithine effect in peptide cation dissociation

The ornithine effect in peptide cation dissociation

Origins and structures of background ions produced by fast-atom bombardment of glycerol

An investigation of site-selective gas-phase reactions of amino alcohols with dimethyl ether ions

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