Gabriel L. Radu

Comparative Proteomics Reveals Novel Components at the Plasma Membrane of Differentiated HepaRG Cells and Different Distribution in Hepatocyte- and Biliary-Like Cells

Hepatitis B virus (HBV) is a human pathogen causing severe liver disease and eventually death. Despite important progress in deciphering HBV internalization, the early virus-cell interactions leading to infection are not known. HepaRG is a human bipotent liver cell line bearing the unique ability to differentiate towards a mixture of hepatocyte- and biliary-like cells. In addition to expressing metabolic functions normally found in liver, differentiated HepaRG cells support HBV infection in vitro, thus resembling cultured primary hepatocytes more than other hepatoma cells. Therefore, extensive characterization of the plasma membrane proteome from HepaRG cells would allow the identification of new cellular factors potentially involved in infection. Here we analyzed the plasma membranes of non-differentiated and differentiated HepaRG cells using nanoliquid chromatography-tandem mass spectrometry to identify the differences between the proteomes and the changes that lead to differentiation of these cells. We followed up on differentially-regulated proteins in hepatocytes- and biliary-like cells, focusing on Cathepsins D and K, Cyclophilin A, Annexin 1/A1, PDI and PDI A4/ERp72. Major differences between the two proteomes were found, including differentially regulated proteins, protein-protein interactions and intracellular localizations following differentiation. The results advance our current understanding of HepaRG differentiation and the unique properties of these cells.

Analysis of Phenolic Compounds in Some Medicinal Herbs by LC–MS

In this paper, a liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry in negative mode method was developed for the identification and quantitative determination of 13 individual phenolics (chlorogenic acid, caffeic acid, coumaric acid, ferulic acid, (+)-catechin, (-)-epicatechin, rutin, quercitrin, isoquercitrin, fisetin, isorhamnetin, hesperidin and chrysin) from ethanolic extracts [30, 50 and 70% (w/v)] of Calendula officinalis, Hypericum perforatum, Galium verum and Origanum vulgare and some commercial extracts of these medicinal herbs. Correlation coefficients (r(2)) from calibration curves for all the compounds were between 0.9971 and 0.9996. Limit of detection was in the range of 0.070-0.280 µg/mL and limit of quantification was from 0.233 to 0.932 µg/mL. The method was partially validated and the results obtained are: the intra- and interday relative standard deviation values were within 0.086 and 2.821% and recovery values vary from 95.84% (coumaric acid) to 103.20% (rutin).

LC-MS and FT-IR characterization of amber artifacts

AbstractThis work focuses on using analytical methods, such as Fourier transform Infrared spectroscopy (FTIR) and high performance liquid chromatography (HPLC) with mass spectrometry (MS) detection to assess archaeological and geological amber.The main goal of this study is to apply the previously developed and optimized analytical methods in verifying criteria to ascribe and characterize the origin of materials found in archaeological sites.The proposed LC-MS method was successfully applied for the quantification of succinic acid content both in geological and archaeological samples of amber and offers excellent linearity between 0.1 and 5µg mL−1. The developed FTIR method provided some criteria which is able to differentiate between Baltic and Romanian amber (Romanite) that furthermore validates on archaeological amber artefacts.

Determination of S-Adenosylmethionine and S-Adenosylhomocysteine from Human Blood Samples by HPLC-FL

Abstract S-adenosylmethionine plays an important role in many biochemical reactions, including human health maintenance and disease prevention. This paper proposes a simplified, rapid, and easy high performance liquid chromatography (HPLC) with fluorimetric detection method of S-adenosylmethionine and its product, S-adenosylhomocysteine. Determination of S-adenosylmethionine and S-adenosylhomocysteine was by HPLC with fluorimetric detection by the formation of the fluorescent 1,N 6-ethanoderivatives of these compounds, which showed a linear concentration range of 310−6–310−8 molL−1 for S-adenosylmethionine and 510−7–510−9for S-adenosylhomocysteine; the detection limits of the method ranged in the nanomolar domain. The method applied to real plasma samples lead to values of 60.1±19.6 for S-adenosylmethionine and 24±14.1 nmolL−1 for S-adenosylhomocysteine.

A Novel HPLC-PDA-MS Method for S-Adenosylmethionine and S-Adenosylhomocysteine Routine Analysis

S-adenosylmethionine and S-adenosylhomocysteine are essential compounds in metabolic pathways; therefore, the development of a suitable method to routinely quantify these compounds is very important. In this paper, a simple and fast method (10 minutes) for simultaneous SAM and SAH quantification in plasma and blood samples is proposed based on the HPLC-PDA-MS technique. A new solid phase extraction procedure for blood samples is reported. The developed method proved to be highly sensitive (1.3 × 10−9 molL−1 for SAM and 4.5 × 10−10 molL−1 for SAH), repeatable (CV = 1.06% for SAM and CV = 0.92% for SAH), and reproducible (CV = 4.1% for SAM and CV = 3.77% for SAH).

Fourier transform Raman and statistical analysis of thermally altered samples of amber

We report the experimental results that refer to a Fourier transform Raman (FT-Raman) survey of thermally altered Baltic and Romanian amber and the related statistical interpretation of data using principal component analysis (PCA). Although FT-Raman spectra show several small changes in the characteristic features of the investigated amber samples which may be used for discrimination, their visual recognition is relatively difficult, especially when interpreting data from archeological samples, and thus multivariate data analysis may be the solution to more accurately assign the geological origin based on overall characteristic spectral features. The two categories of amber have different behavior in terms of degradation during the experimental alteration, and Romanian amber is more susceptible to physico–chemical transformations by the aggressive environment when compared with Baltic amber. The obtained data were in accordance with the Fourier transform infrared (FT-IR) remarks published previously in a dedicated journal. The Raman technique is an alternative method that requires little to no sample preparation, water does not cause interference, and the spectra can be collected from a small volume (1-50 μm in diameter).