High-energy collision-activated and electron-transfer dissociation of gas-phase complexes of tryptophan with Na+, K+, and Ca2+

EnantioselectivePhotolysis and Quantitative Chiral Analysis of Tryptophan Complexed With Alkali‐Metalized L‐Serine in the Gas Phase

“…Na + (Trp) ( m/z 227) was formed by the evaporation of L‐Ser in the UV excitation of either heterochiral Na + (L‐Ser)(D‐Trp) or homochiral Na + (L‐Ser)(L‐Trp). This dissociation pathway was similar to the CID of Na + (Trp) 2 , which was reported to be in a charge‐solvated structure where Na + was bonded to nonzwitterionic Trp having both NH 2 and COOH groups . However, in a zwitterionic structure having an NH 3 + group, the NH 3 ‐elimination product can be formed, which was not observed.…”

“…This dissociation pathway was similar to the CID of Na + (Trp) 2 , which was reported to be in a charge-solvated structure where Na + was bonded to nonzwitterionic Trp having both NH 2 and COOH groups. 21 However, in a zwitterionic structure having an NH 3 + group, the NH 3 -elimination product can be formed, which was not observed. Therefore, we postulate that gasphase Trp complexed with Na + (L-Ser) has a charge-solvated structure, and the energy absorbed by Trp is released through the evaporation of an amino acid molecule.…”

Hypervalent radical formation probed by electron transfer dissociation of zwitterionic tryptophan and tryptophan‐containing dipeptides complexed with Ca2+ and 18‐crown‐6 in the gas phase

“…It is unstable and dissociates through N–H or N–C bond cleavage, just as the NH 4 radical dissociates to NH 3 + H, with a lifetime of 13 ps . Reactions via a hypervalent radical intermediate were observed in ETD of Ca 2+ (Trp) 2 using an alkali metal target . Therefore, the hydrogen atom loss observed in the ETD spectrum of TrpCa 2+ (18C6) indicates formation of a hypervalent radical, R‐NH 3 , in the cluster through an intermolecular electron transfer from the fluoranthene anion to the NH 3 + group of the Z1 structure of TrpCa 2+ (18C6).…”

“…However, this confuses the structural analysis. For example, one Trp was zwitterionic, and the other Trp adopted a non‐zwitterionic structure in Ca 2+ (Trp) 2 . In contrast, non‐covalent 1 : 1 complexes of an analyte with Ca 2+ (18C6) are generated using electrospray ionization of a solution containing an analyte, CaCl 2 and 18C6.…”

Molecular recognition and quantitative analysis of leucine and isoleucine using photodissociation of cold gas‐phase noncovalent complexes

“…15 Therefore, the structures of amino acids in Na + (Trp)(Ile) are likely non-zwitterionic, which is consistent with that of Na + (Trp) and Na + (Trp) 2 reported previously. [16][17][18] In addition to these product ions, Na + (Ile) (m/z 154) formed via detachment of Trp is observed. The minor product ion at m/z 157 is assigned to (CO 2 + C 2 H 2 ) loss from Na + (Trp).…”