STRUCTURAL ELUCIDATION OF A PEPTIDE FROM A SINGLE NEURON BY MATRIX-ASSISTED LASER DESORPTION IONIZATION EMPLOYING A TANDEM DOUBLE FOCUSING MAGNETIC-ORTHOGONAL ACCELERATION TIME-OF-FLIGHT MASS-SPECTROMETER/

An AutoSpec-Tof mass spectrometer, in the configuration of a matrix-as sisted laser desorption/ionization source, a trisector mass spectromet er, a high-energy collision chamber, and a time-of-flight mass spectro meter, was used for direct structural characterization of a tetrapepti de from a single identifiable neuron. Peptides from the freshly dissec ted snail neuron were desorbed and ionized by the matrix-assisted lase r desorption/ionization source. A molecular species with a protonated mass of 429 Da was selected as the parent ion and fragmented in the hi gh-energy collision chamber with xenon gas at 800 eV, producing daught er ions that were detected with a time-of-flight detector, The various ion series were recorded and, together, show that the parent ion has the primary structure of AGPWamide.