1. Detection of hypoxia-related proteins in medaka (Oryzias latipes) brain tissue by difference gel electrophoresis and de novo sequencing of 4-sulfophenyl isothiocyanate-derivatized peptides by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry
Leon P Oehlers, Amy N Perez, Ronald B Walter Comp Biochem Physiol C Toxicol Pharmacol. 2007 Feb;145(1):120-33. doi: 10.1016/j.cbpc.2006.06.005. Epub 2006 Jun 21.
Two-dimensional fluorescence-based difference gel electrophoresis (DIGE) was used in combination with matrix-assisted laser desorption/ionization tandem time-of-flight mass spectrometry (MALDI-TOF/TOF-MS) to identify a set of hypoxia-related biomarker proteins in medaka (Oryzias latipes) brain tissue. Each of the proteins were identified via de novo sequencing of tryptic peptides derivatized with 4-sulfophenyl isothiocyanate (SPITC), which N-terminally sulfonates peptides and promotes facile post-source decay peptide fragmentation, resulting in greatly simplified spectra consisting mainly of y-series fragment ions. We also report that addition of the non-ionic surfactant n-octyl-beta-d-glucopyranoside significantly improves SPITC-derivatized peptide recoveries. In addition, we found that a MALDI matrix consisting of the sodium-tolerant matrix 2,4,6-trihydroxyacetophenone, diammonium citrate, and alpha-cyano-4-hydroxycinnamic acid also improves ionization of SPITC-peptides, presumably by reducing ionization suppression effects from matrix contaminants, especially sodium cations. The DIGE experiments and analyses resulted in detection of six abundant proteins and related isozymes up-regulated (>1.49, p<0.005) in hypoxic medaka brain tissues, including two hemoglobin beta subunit forms, four carbonic anhydrase 2 forms, calbindin, aldolase, succinate dehydrogenase, and glutathione-S-transferase.
2. De novo sequencing of tryptic peptides sulfonated by 4-sulfophenyl isothiocyanate for unambiguous protein identification using post-source decay matrix-assisted laser desorption/ionization mass spectrometry
Ping Chen, Song Nie, Wei Mi, Xian-Chun Wang, Song-Ping Liang Rapid Commun Mass Spectrom. 2004;18(2):191-8. doi: 10.1002/rcm.1280.
A simple method of solid-phase derivatization and sequencing of tryptic peptides has been developed for rapid and unambiguous identification of spots on two-dimensional gels using post-source decay (PSD) matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. The proteolytic digests of proteins are chemically modified by 4-sulfophenyl isothiocyanate. The derivatization reaction introduces a negative sulfonic acid group at the N-terminus of a peptide, which can increase the efficiency of PSD fragmentation and enable the selective detection of only a single series of fragment ions (y-ions). This chemically assisted method avoids the limitation of high background normally observed in MALDI-PSD spectra, and makes the spectra easier to interpret and facilitates de novo sequencing of internal fragment. The modification reaction is conducted in C(18) microZipTips to decrease the background and to enhance the signal/noise. Derivatization procedures were optimized for MALDI-PSD to increase the structural information and to obtain a complete peptide sequence even in critical cases. The MALDI-PSD mass spectra of two model peptides and their sulfonated derivatives are compared. For some proteins unambiguous identification could be achieved by MALDI-PSD sequencing of derivatized peptides obtained from in-gel digests of phosphorylase B and proteins of hepatic satellite cells (HSC).
3. alpha-Defensins from blood leukocytes of the monkey Papio hamadryas
E V Tsvetkova, G M Aleshina, O V Shamova, L E Leonova, R I Lehrer, V N Kokryakov Biochemistry (Mosc). 2006 Aug;71(8):879-83. doi: 10.1134/s0006297906080098.
Three antimicrobial peptides named PHD1-3 (Papio hamadryas defensin) have been isolated from hamadryas baboon blood leukocytes using preparative electrophoresis and reverse-phase HPLC. The primary structures of these peptides have been determined by automated Edman degradation and mass-spectrometry. The results suggest that the peptides belong to the alpha-defensin family. Structural homology analysis reveals that among alpha-defensins from other animal species, PHD3 is the most closely related to RMAD5 (rhesus macaque alpha-defensin) (90% homology) from rhesus macaque leukocytes and also highly similar to human alpha-defensin HD5 (60% homology), which is produced by intestinal Paneth cells. The homology of PHD3 with human neutrophil alpha-defensin HNP1 (human natural peptide) was 30%. The primary structures of PHD1 and PHD2 are most similar to RED1 (rhesus enteral defensin), one of six enteral alpha-defensins of rhesus monkeys. PHD1-3 have been shown to be active against the Gram-positive bacteria Listeria monocytogenes and Staphylococcus aureus, the Gram-negative bacterium Escherichia coli, and the fungus Candida albicans, similarly to the human HNP1 defensin.
