ABSTRACT
Objective To set up a method of stools protein extraction,analysis and identification in order to get the new nonin-vasive indicators of human digestive diseases.Methods The stools proteins,collected from healthy persons,the patients with atrophic gastritis,those who suffed from gastric carcinoma and postoperative patients with gastric carcinoma respectively, were extracted in three different ways including saline,Tris-HCl buffer and Urea buffer,the best way was selected by using SDS-PAGE,then a preliminary analysis of stools proteins was performed by 1D LC-MS/MS.Results The methods of saline and Tris-HCl buffer could get more stools proteins than the method of urea.The proteins in stools from the healthy persons, the patients with atrophic gastritis,the patients with gastric carcinoma and postoperative patients with gastric carcinoma were all abundant and more than one hundred.There was a significant difference in stools protein maps among the various populations.Alpha1-antitrypsin,a number of immunoglobulin and keratin were identified in the stools from patients with gastric carcinoma but not postoperative patients with gastric carcinoma and the healthy persons.Conclusions In this re-search,there was a significant difference in stools protein maps among the healthy persons,the patients with atrophic gastri-tis,the patients with gastric carcinoma and postoperative patients with gastric carcinoma,not only the composition of stools proteins,but also the abundance of same proteins.Therefore,using proteomics technologies to screening of the noninvasive indicators in human stools is viable.The study recommended that the noninvasive indicators in human stools should be iden-tified with quantitative differences analysis combination of quality of mass spectrometer method in the future research.
ABSTRACT
Matrix_assisted laser desorption ionization_time of flight tandem mass spectrometry ( MALDI_TOF/TOF MS) and electrospray ionization_quadrupole_time of flight mass spectrometry ( ESI_Q_TOF MS) were used to confirm the structure of cyclic lipopeptide daptomycin fastly. First, the relative molecular weight 1916. 7107 of daptomycin was measured by ESI with error 0. 0007. The sample’s doubly charged peak m/z 809. 848 was selected as precursor ion for ESI_MS/MS analysis, and the exocyclic amino acid sequence C9 H19 CO_Trp_Asn_Asp was successfully matched. Second, the experimental conditions of cleaving daptomycin by lithium hydroxide ( LiOH) were optimized and the ring_opened process was monitored by MALDI_TOF/TOF MS. After obtaining ring_opened product with purity of above 95%, the MS/MS measurements by MALDI and ESI were carried out. The b+and y+of ring_opened product were completely matched, which confirmed the amino acid sequence of daptomycin. Finally, ESI_MS/MS conditions of ring_opened product were further optimized to obtain more low mass fragment ions for analyzing the structure of fatty acid chain and the cleavage pattern of fat chain in mass spectrometry was proposed. The method was fast, convenient, accurate and reliable for identifying cyclic lipopeptide compounds.
ABSTRACT
This review largely deals with the peptide toxins elaborated by marine cone snails of the genus Conus . Each species of Conus contains in its venom 50 to 200 different peptides directed at different macromolecular targts. These include competitive antagonists of postsynaptic nicotinic receptors (a-conotoxins), blockers selective for Na+ channels in skeletal muscle (u- conotoxins), blockers of presynaptic of antagonists of postsynaptic Ca2+ channels (w-conotoxins), activators of Na+ channels (s-conotoxins), blockers of K+ channels (k-conotoxins), blockers of nicotinic receptor channels (u-conotoxins) and antagonists of NMDA receptors (cono-sleeper).The small size of the peptides (13 to 30 residues is typical) has facilitated synthesis of many of them. A very attractive feature is the highly cross-linked conserved 2 to 3 disulfide bonds which make conotoxins conformationally rigid, some of conotoxins, however, are stabilized by r-carboxyglutamates. The Structure-Activity Relationships of conotoxins and a brief perspective have been reviewed in the paper.