Influence of hydrophobicity on positive-and negative-ion yields of peptides in electrospray ionization mass spectrometry

RATIONALE: The influence of hydrophobicity originating from an amino acid phenylalanine (Phe) residue on the ion yields of peptides has been empirically evaluated using positive-and negative-ion electrospray ionization (ESI) mass spectrometry. The enhancement effect of hydrophobicity was compared with that of the presence of basic and acidic residues of peptides. METHODS: In order to empirically understand the ion yields in soft ionization methods, we have divided the total ionization process into ionization efficiency of analyte molecules and the rate of desorption or vaporization of molecules. The ion yields of protonated and deprotonated molecules of peptides were evaluated. RESULTS: The presence of a Phe residue resulted in an increase in the ion yields of both the analyte ions [M + nH] n+ and [M-nH] n-. The relationship between the ion yields and hydrophobicities of peptides was evaluated using the partition coefficient measured by thin-layer chromatography (PACTLC). A peptide containing a Phe residue at its C-terminus gave a higher ion yield than when it was at the N-terminus. CONCLUSIONS: The ion yields of peptides increased with increasing hydrophobicity both in positive-and negative-ion ESI. The enhancement effect of hydrophobicity on the ion yields was higher than that of basicity and acidity of the peptides in ESI

Mass spectrometry imaging of the capsaicin localization in the capsicum fruits

We succeeded in performing mass spectrometry imaging (MSI) of the localization of capsaicin in cross-sections of the capsicum fruits at a resolution of 250 µm using matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. Post source decay of protonated capsaicin ion revealed structural information of the corresponding acid amide of vanillylamide and C9 chain fatty acid. MALDI-TOF-MSI confirmed that localization of capsaicin in the placenta is higher than that in the pericarp. In addition, it revealed no localization of capsaicin in seed and the higher localization of capsaicin at placenta surface compared with that in the internal region. A quantitative difference was detected between localizations of capsaicin at placenta, pericarp and seed in the capsicum fruits. This imaging approach is a promising technique for rapid quality evaluation general food as well as health food and identification of medicinal capsaicin in plant tissues

Rapidity and Precision of Steroid Hormone Measurement

Steroids are present in all animals and plants, from mammals to prokaryotes. In the medical field, steroids are commonly classified as glucocorticoids, mineralocorticoids, and gonadal steroid hormones. Monitoring of hormones is useful in clinical and research fields for the assessment of physiological changes associated with aging, disease risk, and the diagnostic and therapeutic effects of various diseases. Since the discovery and isolation of steroid hormones, measurement methods for steroid hormones in biological samples have advanced substantially. Although immunoassays (IAs) are widely used in daily practice, mass spectrometry (MS)-based methods have been reported to be more specific. Steroid hormone measurement based on MS is desirable in clinical practice; however, there are several drawbacks, including the purchase and maintenance costs of the MS instrument and the need for specialized training of technicians. In this review, we discuss IA- and MS-based methods currently in use and briefly present the history of steroid hormone measurement. In addition, we describe recent advances in IA- and MS-based methods and future applications and considerations

Nutrition analysis by nanoparticle-assisted laser desorption/ionisation mass spectrometry

We analysed the bioactive compounds in Panax ginseng C.A. Meyer by using nanoparticle-assisted laser desorption/ionisation (nano-PALDI) mass spectrometry (MS). To this end, we prepared manganese oxide nanoparticles (d = 5.4 nm) and developed a nano-PALDI MS method to analyse the standard ginsenosides and identify these ginsenosides in an extract of P. ginseng. The nanoparticles served as an ionisation-assisting reagent in MS. The mass spectra did not show any background interference in the low-m/z range. Our pilot study showed that the nanoparticles could ionise the standard ginsenosides and also respective lipid and ginsenosides in the extract without the aid of chemical and liquid matrices used in conventional MS methods. Analysis of the post-source decay spectra obtained using nano-PALDI MS will yield information regarding the chemical structure of the analyte

Study on Formation Mechanism and Ligand-directed Architectural Control of Nanoparticles Composed of Bi, Sb and Te: Toward One-pot Synthesis of Ternary (Bi,Sb)2Te3 Nanobuilding Blocks

This paper reports a study on the formation mechanism of nanoparticles (NPs) composed of bismuth, antimony and tellurium for thermoelectric materials using a modified polyol synthetic route. Our one-pot synthesis technique has proven highly versatile in creating a wide range of different anisotropic NPs such as nanowires (NWs), nanodiscs (NDs), nanoribbons and nanospines (NDs studded on NWs) simply by modifying the capping species or elemental precursor feeding ratio used in the synthesis. However, an independent control of morphology and composition is still hugely challenging and the facile synthesis of (Bi,Sb)_2Te_3 solid solution NPs is not a trivial task, reflecting the complex nature of this multicomponent system. To achieve this goal, it is imperative to understand the formation mechanism based on a systematic investigation of mono- and binary elemental NP systems. Our study clearly shows the different actions of oleylamine (OAM) and decanethiol (DT) capping ligands in our synthesis reaction. In the case of DT capping system, Te NDs are first formed, and then, Bi and Sb are separately incorporated into the Te ND structure via catalytic decomposition of Bi-DT and Sb-DT complexes on the Te ND surfaces. Therefore, the resulting NPs are phase segregated into Te, Bi_2Te_3 and Sb_2Te_3. On the other hand, in the case of the OAM capping system, Te NWs and Bi-Sb solid solution NPs are formed separately, and then, parts of Te NWs are transformed into (Bi,Sb)_2Te_3 phase via oriented attachment of Bi-Sb NPs and Te NWs. These findings are crucially important towards the one-pot synthesis of uniform (Bi,Sb)_2Te_3 nanobuilding blocks with controllable characteristics for highly efficient thermoelectric materials

Protein Carbonylation Detected with Light and Heavy Isotope-Labeled 2,4-Dinitrophenylhydrazine by Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry

Oxidation of proteins leads to carbonylation―the formation of aldehydes or ketones―at the amino acid side chain and/or the terminal amino groups. Carbonylated proteins have been conventionally detected by UV absorption spectrometry of the stable adduct with 2,4-dinitrophenylhydrazine (DNPH). However, this routine method is limited to detection of the total carbonyl content and does not provide structural information. We developed an isotope-dilution method for the specific detection of carbonylated proteins using ^C_6-DNPH and ^C_6-DNPH. This method has the following steps: the oxidized protein or peptide is divided into two parts, and these parts are independently labeled with ^C_6-DNPH and ^C_6-DNPH; the mixtures of these two labeled solutions are subsequently measured with matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. The carbonylated peptide was found by searching for a doublet peak having a mass difference of 6 Da. We examined oxidized angiotensin I and oxidized lysozyme prepared by treatment with NaOCl. The oxidized angiotensin I showed four pairs of doublet peaks in the MALDI-TOF mass spectrum. The structure was determined by tandem mass spectrometry. In the case of tryptic digest of the oxidized lysozyme, two carbonylated products could be easily identified even in a complex mixture. The use of ^C_6-DNPH provides rapid and accurate detection of carbonylated peptides even in complex mixtures