title: Proteomic study of a model causative agent of harmful red tide, Prorocentrum triestinum I: Optimization of sample preparation methodologies for analyzing with two-dimensional electrophoresis.
abstract: A comprehensive study to find the optimal sample preparation conditions for two-dimensional electrophoresis (2-DE) analysis of Prorocentrum triestinum, a model causative agent of harmful algal blooms (HABs) was carried out. The four major sample preparation steps for 2-DE: (a) cell disruption: i.e. sonication and homogenization with glass beads; (b) protein extraction : i.e. sequential and independent extraction procedures; (c) pre-electrophoretic treatment: these included (i) treatment with RNAase/DNAase or benzonase; (ii) ultracentrifugation to sediment large macromolecules such as DNA; (iii) desalting and concentration by ultrafiltration through a Microcon centrifugal filter device (MWCO: 3000 daltons); and (iv) desalting by a micro BioSpin chromatography column (MWCO: 6000 daltons); and (d) rehydration buffers, reducing agents and sample application in the first dimension isoelectric focussing were studied. Our results showed that sonication is easy to perform and resulted in a higher protein yield. Among the four extraction buffers, the urea containing buffers resulted in the extraction of the highest amount of protein while tris(hydroxymethyl)aminomethane buffers and trichloroacetic acid (TCA)/acetone precipitation allowed detection of a higher number of protein species (i.e. protein spots). Desalting by BioSpin and ultrafiltration have improved the 2-DE resolution of the water soluble fraction but have less effect on urea containing fractions. TCA/acetone precipitation was able to desalt all protein fractions independent of the extraction media, however extended exposure to this low pH medium has caused protein modification. Introduction of either DNase/RNase or benzonase treatment did not improve the discriminatory power of the 2-DE but this treatment did yield 2-DE with the clearest background. Proteolytic digestion was inhibited by addition of a protease inhibitor cocktail. Taken overall, a combination of sequential extraction and desalting by BioSpin chromatography for sample treatment before first dimension of 2-DE gave best results based on its simplicity and minimal protein loss. Finally, triscarboxyethylphosphine (TCEP) has performed well as a reducing agent in both the rehydration and equilibration buffers. The rehydration buffer found to be best in this study was 8.0 M urea, 2% 3-[(3-cholamidoprphyldimethylamino]-1-propanesulfonate, 4 mM TCEP and 1% immobilized pH gradient buffer. Subsequently, we applied this finding and performed 2-DE analysis on the soluble protein fractions extracted from light-starved cultured algal cells (nonblooming) and cultured cells grown under optimal conditions (blooming). 2-DE maps of these algal cultures were visibly different and many differentially expressed proteins were found.
mesh_terms: D000096:Acetone / Q000494:pharmacology; D000818:Animals; D003851:Deoxyribonucleases / Q000378:metabolism; D004141:Dinoflagellida / Q000737:chemistry*; D015180:Electrophoresis, Gel, Two-Dimensional / Q000379:methods; D004591:Electrophoresis, Polyacrylamide Gel; D006863:Hydrogen-Ion Concentration; D007202:Indicators and Reagents / Q000494:pharmacology; D008027:Light; D008855:Microscopy, Electron, Scanning; D010720:Phosphines / Q000378:metabolism; D020543:Proteome; D012260:Ribonucleases / Q000378:metabolism; D016622:Silver Staining; D014461:Ultracentrifugation; D014867:Water / Q000378:metabolism
chemical_list: D000096:Acetone; D003851:Deoxyribonucleases; D007202:Indicators and Reagents; D010720:Phosphines; D020543:Proteome; D012260:Ribonucleases; D014867:Water; C080938:tris(2-carboxyethyl)phosphine