The zinc complex of glycinate [Gly-H ϩ Zn] ϩ has been formed by electrospray of a glycine/ZnCl 2 mixture in a 50:50 vol. water/methanol solution. In this article, the precursors and the fragments of [Gly-H ϩ Zn] ϩ ions are studied by means of collisional induced decomposition (CID) experiments including H/D exchanges and accurate ab initio calculations. Two precursors were identified: [Gly ϩ CH 3 OH-H ϩ Zn] ϩ (A) and [Gly ϩ Gly-H ϩ Zn] ϩ (B), A being much more abundant than B. The three main fragmentations of [Gly-H ϩ Zn] ϩ are loss of carbon dioxyde, loss of carbon monoxyde, and successive losses of water and carbon monoxyde. To interpret these fragmentations four structures were chosen to describe [Gly-H ϩ Zn] ϩ . These structures are complexes between Zn(II) and glycine deprotonated either on the carboxylic group [NH 2 CH 2 COOZn] ϩ (1) or on the amine function [ZnNHCH 2 COOH] ϩ (2) or isomeric forms involving ZnH ϩ i.e. either [NH 2 CHCOOZnH] ϩ (3) or [HZn . . . NH¢CHCOOH] ϩ (4) respectively. None of the fragmentations is interpretable directly from structures 1 and 2. Loss of carbon dioxyde occurs from 3, loss of carbon monoxyde from a complex CX where HOZn ϩ interacts with CO and NH¢CH 2 , a rearranged form of 2. Successive losses of water and carbon monoxyde can take place from 4. The non occurrence of structures 1 and 2 during the fragmentation of [Gly-H ϩ Zn] ϩ ions is interpreted by isomerizations within A before evaporation of the last molecule of solvent. These isomerizations are energetically easier than the last step of desolvation. (Int J Mass Spectrom 204 (2000) 267-280) © 2000 Elsevier Science B.V.