. Author manuscript; available in PMC: 2006 Mar 8.

Published in final edited form as: J Am Chem Soc. 1996 Jul 31;118(30):7178–7189. doi: 10.1021/ja9609157

Table 1.

Measured Zero-Pressure Arrhenius Activation Parameters for the Dissociation of Singly Protonated Bradykinin and Its Variants^a

peptide	activation energy (eV)	frequency factor (s⁻¹)	major fragments	minor fragments
[Ala⁶]-bradykinin	1.1	10¹¹	M⁺ – NH₃	y₇, b₂, b₈, y₆, y₅, y₈
bradykinin	1.3	10¹²	M⁺ – NH₃
des-Arg¹-bradykinin	0.82	10⁷	y₆	M⁺ – H₂O
des-Arg⁹-bradykinin*	1.2	10¹²	b₂	y₆, M⁺ – H₂O
des-Pro²-bradykinin	1.1	10¹¹	M⁺ – NH₃	y₇
[Lys¹]-bradykinin	1.0	10⁹	y₇	M⁺ – H₂O, y₆, y₅
Lys-bradykinin	1.4	10¹²	M⁺ – H₂O, M⁺ – 60	M⁺ – H₂O, RP⁺, b₉, y₆, y₅
[Thr⁶]-bradykinin*	1.2	10¹²	M⁺ – NH₃	M⁺ – 60, y₇, y₆, y₅, b₂
methyl ester of [Ala⁶]-bradykinin	0.76	10⁷	M⁺ – NH₃, M⁺ – MeOH	y₇, y₈, b₈, M⁺ – 60
methyl ester of bradykinin	0.61	10⁵	M⁺ – MeOH	M⁺ – NH₃, y₇, c₅, b₈, y₈, y₄, b₂
methyl ester of des-Arg¹-bradykinin	0.94	10⁷	M⁺ – H₂O
methyl ester of des-Arg⁹-bradykinin	1.3	10⁹	M⁺ – H₂O	b₂

Activation energies have standard deviations between 0.03 and 0.1 eV. Those processes for which calculations indicate the measured Arrhenius parameters are lower than the “high-pressure” limit values within the error of the experiment are indicated by an asterisk.