Self-assembled dithiothreitol on Au surfaces for biological applications: phospholipid bilayer formation

Self-assembly of dithiothreitol (DTT) on Au(111) from solution deposition has been studied by X-ray photoelectron spectroscopy and electrochemical data. DTT molecules self-assemble on Au(111) in a lying-down configuration irrespective of the concentration and temperature. XPS and electrochemical data indicate a DTT surface coverage of y E 0.16 with two S-head–Au covalent bonds per DTT molecule. The DTT monolayer turns the Au surface hydrophilic enough to allow the formation of fluid dimyristoylphosphatidylcholine (DMPC) bilayer domains by vesicle fusion as revealed by "in situ" atomic force imaging. Methylene blue (MB) and flavin adenine dinucleotide (FAD) have been used as probes to study molecule transport across the bilayer.Facultad de Ciencias ExactasInstituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

The complete genome sequence of Chromobacterium violaceum reveals remarkable and exploitable bacterial adaptability

Chromobacterium violaceum is one of millions of species of free-living microorganisms that populate the soil and water in the extant areas of tropical biodiversity around the world. Its complete genome sequence reveals (i) extensive alternative pathways for energy generation, (ii) ≈500 ORFs for transport-related proteins, (iii) complex and extensive systems for stress adaptation and motility, and (iv) wide-spread utilization of quorum sensing for control of inducible systems, all of which underpin the versatility and adaptability of the organism. The genome also contains extensive but incomplete arrays of ORFs coding for proteins associated with mammalian pathogenicity, possibly involved in the occasional but often fatal cases of human C. violaceum infection. There is, in addition, a series of previously unknown but important enzymes and secondary metabolites including paraquat-inducible proteins, drug and heavy-metal-resistance proteins, multiple chitinases, and proteins for the detoxification of xenobiotics that may have biotechnological applications

Response Surface Methodology IV-Optimal design applied to the performance improvement of an RP-HPLC-UV method for the quantification of phenolic acids in Cecropia glaziovii products

ABSTRACTChlorogenic and caffeic acids are bioactive phenolic compounds present in Cecropia glaziovii Snethl., Urticaceae, products that have been used as analytical markers. This paper reports a chemometric study aimed at improving chromatographic performance for quantification of these markers by RP-HPLC. The organic to aqueous content ratio, the acid content of the mobile phase, and the elution method were analyzed using a Response Surface Methodology IV-Optimal design. The resolution between peaks, retention time, tailing and retention factors, number of theoretical plates and peak widths were evaluated. The optimized conditions were mathematically determined as (A) trifluoroacetic acid 0.05% (v/v), (B) 12% (v/v) acetonitrile and (C) increasing gradient. The method was considered specific, fast, precise, reliable and linear in the ranges of 1.0–200.0 and 2.5–100.0 µg/ml for the chlorogenic and caffeic acids, respectively. The adequate conditions to separate and quantify both phenolic acids in C. glaziovii products were demonstrated. Satisfactory resolution was achieved when compared to a previously published chromatographic method which is unable to separate the chlorogenic acid and an interfering compound presented under certain extractive conditions, demonstrating the importance of systematic studies, specifically when analyzing complex plant matrices

Self-assembled dithiothreitol on Au surfaces for biological applications: phospholipid bilayer formation

Self-assembly of dithiothreitol (DTT) on Au(111) from solution deposition has been studied by X-ray photoelectron spectroscopy and electrochemical data. DTT molecules self-assemble on Au(111) in a lying-down configuration irrespective of the concentration and temperature. XPS and electrochemical data indicate a DTT surface coverage of y E 0.16 with two S-head–Au covalent bonds per DTT molecule. The DTT monolayer turns the Au surface hydrophilic enough to allow the formation of fluid dimyristoylphosphatidylcholine (DMPC) bilayer domains by vesicle fusion as revealed by "in situ" atomic force imaging. Methylene blue (MB) and flavin adenine dinucleotide (FAD) have been used as probes to study molecule transport across the bilayer.Facultad de Ciencias ExactasInstituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Octyl and dodecyl gallates induce oxidative stress and apoptosis in a melanoma cell line

AbstractThis study investigated the mechanism of cytotoxicity of octyl (G8) and dodecyl (G12) gallates in a murine melanoma cell line (B16F10). For this purpose, several methods to measure cell viability were used to determine if the cytotoxicity induced by these gallates corresponds to a general or an organelle-specific effect. Furthermore, the mechanisms related to apoptosis were examined, by studying the caspase-3 activity, oxidative stress, mitochondrial potential and the expression of anti- or proapoptotic proteins. When comparing the various methods of assessing cell viability, the tested gallates showed a higher cytotoxicity in the assay that indicates lysosomal activity, compared with the assays that indicate mitochondrial and ribosomal activities. Both gallates promoted the release of lactate dehydrogenase into the medium, indicating an effect on cell membrane integrity. The gallates also promoted cellular oxidative stress, mitochondrial depolarization and an increase in caspase-3 activity. Furthermore, the gallates induced an increase in proapoptotic (Bax) and a decrease in antiapoptotic (Bcl-2) proteins expression. Our results indicate that the apoptotic cell death induced by G8 and G12 in B16F10 cells involves lipid membrane damages, lysosomal and mitochondrial dysfunction, which was accompanied by alterations in apoptotic proteins expression and seems to be triggered by cellular oxidative stress

Semisynthetic Sesquiterpene Lactones Generated by the Sensibility of Glaucolide B to Lewis and Brønsted–Lowry Acids and Bases: Cytotoxicity and Anti-Inflammatory Activities

Sesquiterpene lactone (SL) subtypes including hirsutinolide and cadinanolide have a controversial genesis. Metabolites of these classes are either described as natural products or as artifacts produced via the influence of solvents, chromatographic mobile phases, and adsorbents used in phytochemical studies. Based on this divergence, and to better understand the sensibility of these metabolites, different pH conditions were used to prepare semisynthetic SLs and evaluate the anti-inflammatory and antiproliferative activities. Therefore, glaucolide B (1) was treated with various Brønsted–Lowry and Lewis acids and bases—the same approach was applied to some of its derivatives—allowing us to obtain 14 semisynthetic SL derivatives, 10 of which are hereby reported for the first time. Hirsutinolide derivatives 7a (CC50 = 5.0 µM; SI = 2.5) and 7b (CC50 = 11.2 µM; SI = 2.5) and the germacranolide derivative 8a (CC50 = 3.1 µM; SI = 3.0) revealed significant cytotoxic activity and selectivity against human melanoma SK-MEL-28 cells when compared with that against non-tumoral HUVEC cells. Additionally, compounds 7a and 7c.1 showed strongly reduced interleukin-6 (IL-6) and nitrite (NOx) release in pre-treated M1 macrophages J774A.1 when stimulated with lipopolysaccharide. Despite the fact that hirsutinolide and cadinanolide SLs may be produced via plant metabolism, this study shows that acidic and alkaline extraction and solid-phase purification processes can promote their formation