The thermal effects of platinum(II) and palladium(II) complexes with 2-acetyl pyridine and pyridine-2-carbaldehyde N(4)-ethyl-thiosemicarbazones in membrane bilayers

Platinum(II) and palladium(II) complexes with 2-acetyl pyridine and pyridine-2-carbaidehyde N(4)-ethyl-thiosemicarbazones, HAc4Et and HFo4Et respectively were synthesized and found to exhibit a cytotoxic potency in a very low micromolar range and to be able to overcome the cisplatin resistance of A2780/Cp8 cells. The biologically active complexes Pd(Fo4Et)(2) (1), Pd(Ac4Et)(2) (2), Pt(Fo4Et)(2) (3) and Pt(Ac4Et)(2) (4) were tested for their perturbation in model membrane bilayers. The aim was to investigate if there is a possible relation between their mechanism of action in membranes with their biological activity. Indeed, it was found that complexes of deprotonated HAc4Et, (2) and (4), are more perturbing than complexes of deprotonated HFo4Et, (1) and (3). (C) 2004 Elsevier B.V. All rights reserved.Thermochimica Act

Post-acquisition spectral stitching. An alternative approach for data processing in untargeted metabolomics by UHPLC-ESI(−)-HRMS

Introduction In the case of the MS-based metabolomics, the large number of false positives remains a fundamental issue. Objective The aim of this study was to develop a new strategy, which highlights the number of the reliable features i.e. the detected features that correspond to a consistent peak according to chromatographic and mass spectrometric criteria. Method For the analysis blood samples from 20 chickens, which were administrated with naringin and 9 samples from control, were analyzed by UHPLC-HRMS (Orbitrap Velos). Two methodologies have been compared for data processing. In the first one (classical approach), all data in the 100–900 m/z mass-to charge range were included for the data processing procedure whereas for the newly developed methodology, the data were shred in 100 Da slices generating 8 datasets, which have been then subjected to the downstream MS data processing. Each dataset was treated separately and the m/z_tR features obtained by either VIP's or t-test values were merged and used as the input for the construction of the general model. Results The new methodology resulted to a 4-fold increase of the peaks that could be considered chromatographically and mass spectrometrically valid. Conclusion A new strategy was reported on the detection of chromatographically reliable features during a metabolomic approach. The shredding of the LC–MS chromatograms into multiple m/z ranges increased the number of the identified chromatographically reliable features. © 2016 Elsevier B.V

Growth and membrane fluidity of food-borne pathogen Listeria monocytogenes in the presence of weak acid preservatives and hydrochloric acid

This study addresses a major issue in microbial food safety, the elucidation of correlations between acid stress and changes in membrane fluidity of the pathogen Listeria monocytogenes. In order to assess the possible role that membrane fluidity changes play in L. monocytogenes tolerance to antimicrobial acids (acetic, lactic, hydrochloric acid at low pH or benzoic acid at neutral pH), the growth of the bacterium and the gel-to-liquid crystalline transition temperature point (Tm) of cellular lipids of each adapted culture was measured and compared with unexposed cells. The Tm of extracted lipids was measured by differential scanning calorimetry. A trend of increasing Tm values but not of equal extent was observed upon acid tolerance for all samples and this increase is not directly proportional to each acid antibacterial action. The smallest increase in Tm value was observed in the presence of lactic acid, which presented the highest antibacterial action. In the presence of acids with high antibacterial action such as acetic, hydrochloric acid or low antibacterial action such as benzoic acid, increased Tm values were measured. The Tm changes of lipids were also correlated with our previous data about fatty acid changes to acid adaptation. The results imply that the fatty acid changes are not the sole adaptation mechanism for decreased membrane fluidity (increased Tm). Therefore, this study indicates the importance of conducting an in-depth structural study on how acids commonly used in food systems affect the composition of individual cellular membrane lipid molecules. © 2013 Diakogiannis, Berberi, Siapi, Arkoudi-Vafea, Giannopoulou and Mastronicolis

Losartan's molecular basis of interaction with membranes and AT 1 receptor

Physicochemical methods were used to study the thermal and dynamic changes caused by losartan in the membrane bilayers. In addition, molecular modeling was implemented to explore its topography both in membranes and AT1 receptor. Its incorporation resulted in the modification of thermal profile of dipalmitoyl phosphatidylcholine (DPPC) bilayers in a concentration dependent way up to 20mol% as it is depicted from the combination of differential scanning calorimetry (DSC) and MAS data. In particular, the presence of losartan caused lowering of the phase transition temperature and abolishment of the pretransition. T1 experiments revealed the location of the drug into the membrane bilayers. The use of a combination of biophysical methods along with docking experiments brought out a possible two-step mechanism which involves incorporation of losartan at the interface of membrane bilayers and diffusion in the upper parts of AT1 receptor helices IV-VII. © 2003 Elsevier Science Ireland Ltd. All rights reserved

An integrated approach using UHPLC-PDA-HRMS and 2D HSQC NMR for the metabolic profiling of the red alga Laurencia: Dereplication and tracing of natural products Dedicated to the memory of Professor Constantinos Vagias.

The global metabolic profile of Laurencia crude red algal extracts was addressed by applying high-throughput analytical techniques, namely UHPLC-PDA-HRMS and 2D HSQC NMR. An integrated platform including software tools and databases, such as Xcalibur, ToxID, ACD/Labs and MarinLit, has been developed to mine the complex analytical data towards the accelerated identification of known metabolites and the detection of new natural products at the early stages of phytochemical analysis. In parallel, a searchable 'in-house' Laurencia-focused NMR database incorporating chemical structures, NMR spectroscopic data and reported biological activities has been generated. The screening strategy has been developed as a tool to prioritize the crude extracts to be further subjected to phytochemical analysis by tracing the presence of new natural products among the pool of known compounds. The successful application of this integrated methodology in the crude extract of Laurencia chondrioides led to the rapid detection of two new C15 bromoallene acetogenins (1 and 2), which were subsequently isolated and characterized. © 2014 Elsevier Ltd. All rights reserved