Improved N(α)-acetylated peptide enrichment following dimethyl labeling and SCX.

Protein N-terminal acetylation is one of the most common modifications occurring co- and post-translationally on either eukaryote or prokaryote proteins. However, compared to other protein modifications, the physiological role of protein N-terminal acetylation is relatively unclear. To explore the biological functions of protein N-terminal acetylation, a robust and large-scale method for qualitative and quantitative analysis of this modification is required.

Mechanism-based inhibition of CYP1A1 and CYP3A4 by the furanocoumarin chalepensin.

The cytochrome P450 (P450, CYP) 2A6 inhibitor chalepensin was found to inhibit human CYP1A1, CYP1A2, CYP2A13, CYP2C9, CYP2D6, CYP2E1, and CYP3A4 to different extents. CYP1A1 and CYP3A4 underwent pronounced mechanism-based inactivation by chalepensin and had the smallest IC50 ratios of inhibition with NADPH-fortified pre-incubation (IC50(+)) to that without pre-incubation (IC50(-)). CYP2E1 had the least susceptibility to mechanism-based inactivation.

Magnetic bead-based hydrophilic interaction liquid chromatography for glycopeptide enrichments.

Purification of glycopeptides prior to the analysis by mass spectrometry (MS) is demanded due to ion suppression effect during ionization caused by the co-presence of non-glycosylated peptides. Among various purification methods, hydrophilic interaction liquid chromatography (HILIC) has become a popular method in recent years. In this work, we reported a novel magnetic bead-based zwitterionic HILIC (ZIC-HILIC) material which was fabricated by coating a zwitterionic polymer synthesized by spontaneous acid-catalyzed polymerization of 4-vinyl-pyridinium ethanesulfonate monomer on iron oxide magnetic nanoparticles.

Simple and specific dual-wavelength excitable dye staining for glycoprotein detection in polyacrylamide gels and its application in glycoproteomics.

In this study, a commercially available fluorescent dye, Lissamine rhodamine B sulfonyl hydrazine (LRSH), was designed to specifically stain the glycoproteins in polyacrylamide gels. Through the periodate/Schiff base mechanism, the fluorescent dye readily attaches to glycoproteins and the fluorescence can be simultaneously observed under either 305 nm or 532 nm excitation therefore, the dye-stained glycoproteins can be detected under a regular UV transilluminator or a more elegant laser-based gel scanner. The specificity and detection limit were examined using a standard protein mixture in polyacrylamide gels in this study.

Mechanism-based inhibition of cytochrome P450 (CYP)2A6 by chalepensin in recombinant systems, in human liver microsomes and in mice in vivo.

Background And Purpose: Chalepensin is a pharmacologically active furanocoumarin compound found in rue, a medicinal herb. Here we have investigated the inhibitory effects of chalepensin on cytochrome P450 (CYP) 2A6 in vitro and in vivo.

Experimental Approach: Mechanism-based inhibition was studied in vitro using human liver microsomes and bacterial membranes expressing genetic variants of human CYP2A6.

Bioactive constituents from the roots of Panax japonicus var. major and development of a LC-MS/MS method for distinguishing between natural and artifactual compounds.

Two new saponins, panajaponol (1) and pseudoginsenoside RT1 butyl ester (2), together with 35 known compounds (3-37), were isolated from the roots of Panax japonicus var. major. The structures of 1 and 2 were elucidated on the basis of spectroscopic analysis and chemical methods.

β-carboline alkaloids from Stellaria dichotoma var. lanceolata and their anti-inflammatory activity.

The present investigation on the chemical constituents of the roots of Stellaria dichotoma var. lanceolata has resulted in the isolation of 21 β-carboline alkaloids, including 13 new compounds, dichotomides III-XIV (1-12) and dichotomine E (13), and eight known compounds. The structures of the new compounds were established on the basis of spectroscopic data analysis.

Assignment of disulfide-linked peptides using automatic a1 ion recognition.

We present a novel approach for the assignment of peptides containing disulfide linkages. Dimethyl labeling is introduced to generate labeled peptides which exhibit enhanced a1 ion signals during MS/MS fragmentation. For disulfide-linked peptides, multiple a1 ions can be observed due to multiple N-termini.

Development of a titanium dioxide nanoparticle pipette-tip for the selective enrichment of phosphorylated peptides.

The selective enrichment of specific proteins or peptides on micropipette tips prior to mass spectrometry analysis, which can minimize non-specific interferences as well as sample loss, has been an important issue in current proteomics field. In this paper, we have developed an easy-to-use phosphopeptide-selective pipette tip in which titanium dioxide nanoparticles were embedded in monolithic structure photopolymerized from ethylene glycol dimethacrylate. The simple and convenient fabrication was feasible in a commercial polypropylene pipette tip.

Enhanced a1 fragmentation for dimethylated proteins and its applications for N-terminal identification and comparative protein quantitation.

In this work, dimethyl labeling at the protein level was developed to assist the fragmentation of intact proteins using the Q-TOF instrument. It was shown that a1 ions were favorably enhanced upon collision-induced dissociation for dimethylated proteins with molecular mass below 20 kDa and without N-terminal modifications. This method is helpful in confirming proteolytic sites located at the N-terminus of proteins.