Studies on Fragmentation of Peptide by Nano-electrospray Ionization Fourier Transform Ion Cyclotron Resonance Multi-stage Tandem Mass Spectrometry

The sequence analysis of peptides was performed by nano-electrospray ionization Fourier transform ion cyclotron resonance tandem mass spectrometry（Nano-ESI-FT-ICR-MSn） and several peptides were chosen as examples. With the aid of the collision induced dissociation（CID）, FT-ICR provides not only precise mass/charge ratio, but also structure information of the selected peptides. The fragment ions were identified according to the observed molecular weights and peptide sequence was determined successfully. So Nano-ESI-FT-ICR-MSn is a useful tool for identification of the amino acid sequence of peptides with high confidence. Besides, a pathway for the dehydration of y ions without amino acids containing carboxylic acid under sustained off-resonance irradiation collision-induced dissociation（SORI-CID） condition was proposed.

Improved identification of glycerophospholipids using a linear ion trap mass spectrometer(LTQ) with Pulsed Q Collision Induced Dissociation(PQD)

Phospholipids are the major building blocks of the biological membranes. Additionally, phospholipids modulate membrane trafficking and metabolites derived from their

Octagold selenido nanoclusters:Significance of surface ligands on tuning geometric and electronic structure of Au8Se2 kernel

Two diphosphine-protected superatom gold selenido nanoclusters,[Au_(8)Se_(2)(dppm)4]^(2+)(SD/Au_(8)a,dppm=Ph_(2)PCH_(2)PPh_(2))and[Au_(8)Se_(2)(dppe)4]^(2+)(SD/Au_(8)b,dppe=Ph_(2)P(CH_(2))2PPh_(2)),were obtained by the reduction of[Au(SMe2)Cl]in the presence of Ph3PSe as the selenium ion releasing agents.Both can be regarded as“superatoms”with 1S^(2)configuration based on the spherical Jellium model.Despite the same metal-ligand binding motifs on the surface and the intrinsic C_(2)molecular symmetry,the configurations of Au_(8)Se_(2)kernels in them are different in terms of Au-Au bonded metallic frameworks.SD/Au_(8)a displays a heart-shaped[core+exo]type structure(Au4 tetrahedron core+two exo Au2Se units),whereas the two exo Au_(2)Se counterparts in SD/Au_(8)b are additionally locked by an obvious Au-Au bond,forming a distorted hexagonal Au6 ring with two capping AuSe units appended above and below it.Consequently,they showed different photophysical properties as reflected by their electronic absorption and emission spectra.Especially,both SD/Au_(8)a and SD/Au_(8)b exhibit blue-shifted thermochromic luminescence upon cooling from 293 to 83 K but the latter exhibits anomalous emission intensity evolution trends due to the occurrence of temperature-induced phase transition as revealed by varied-temperature crystallographic analyses.This work not only clearly illustrates the significance of ligands on tuning the kernel structure but also provides two rarely comparable examples for better understanding of the structure-property relationship of gold nanoclusters.

Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometric Study on Sodium Azide Cluster Ions

Sodium azide has rarely been studied in gas phase or in the form of cluster ions and as a model of solid ener-getic substances and inorganic azide salt was ionized by electrospray ionization (ESI) and studied by high resolution Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry (MS) systematically. This paper highlights the effects of experimental conditions on the formation of salt cluster and the collision activation dissociation path-ways of cluster ions to develop a microscopic understanding of inorganic azide salt clusters.