Cytotoxic Effects of Methylgerambullin and Bis(Methylthiomethyl)-Disulphide (SB) on T-Lymphoblastic Leukemic Cell Line (Cem-SS)

The cytotoxic effects of 2 sulphur-containing compounds were studied on Tlymphoblastic leukemic cell line. Methylgerambullin is believed to be a new sulphone derived from a methylthiopropenoic acid isolated from Glycosmis calcicola (family Rutaceae). Another sui phonic compound IS bis- (methylthiomethyl)-disulphide, an extract from Scorodocarpus borneensis (family Olacaceae) with irritating garlic-like odor. Cytotoxic activities of methylgerambullin and bis-(methylthiomethyl)-disulphide were tested against CEM-SS (T-Iymphoblastic leukaemia), KU812F (chronic myelogeneous leukaemia), UACC-62 (melanoma) and HT29 (colon cancer) cell lines using MTT, a colorimetric tetrazolium-based assay. Cytotoxic concentrations of the compounds that killed cells by 50% (CD50) with respect to untreated cell population, varied among the cell lines tested. CEM-SS was found to be the most sensitive cell line to methylgerambullin and bis-(methylthiomethyl)-disulphide with CD50 = 0.25 )µg/ml and 3.50 )µg/ml respectively. The cytotoxic effects exerted by both compounds on this cell line was studied from both morphological manner over 72 hours period. Microscopic observations, including inverted microscopy of live cultures, fluorescent microscopy of acridine orange-propidium iodide stained cultures, and scanning and transmission electron microscopy showed that both necrotic and apoptotic death occurred in meiliylgerambullinand bis-(methylthiomethyl)-disulphide-treated cell populations, based on morphological criteria. From agarose gel electrophoresis and quantitative analyses of intemucleosomal cleavage, treatments with these compounds at their respective CD50 doses did not yield random or multiple of 180-200 bp DNA fragmentation which often associated with necrotic and apoptotic deaths respectively. Such observation may simply owe to the fact that the percentage of apoptosis and necrosis events were fairly low as quantified after acridine orangepropidium iodide staining, or may also suggest the involvement of sulphur residue in methylgerambullin and bis-(methylthiomethyl)-disulphide which act as an antioxidant, thus protecting DNA degradation from occuring. Flow cytometric analyses based on annexin V-FITC (fluorescein isothiocynate) binding to the phosphatidylserines residue which was translocated from the inner to the outer leaflet of the plasma membrane showed that the onset of apoptosis in both methylgerambullin- and bis-(methylthiomethyl)-disulphide-treated population was at 6 hours exposure. Both methylgerambullin and bis-(methylthiomethyl)disulphide induced GO/G1 arrest up to 48 hours and 24 hours respectively followed by arrest in the subsequent S phase

Characterisation of the Binding Properties of Bacillus Thuringiensis 18 Toxin on Leukaemic Cells

<p>Abstract</p> <p>Background</p> <p>Various strains of <it>Bacillus thuringiensis </it>(Bt) have been found to produce parasporal proteins that are cytotoxic to human cancer cells. This study aims to establish the binding affinity of purified Bt 18 toxin for CEM-SS (T lymphoblastic leukaemia cell line), to determine if competition exists between the toxin and commercial anticancer drugs for the binding site on CEM-SS and to localise the binding site of the toxin on CEM-SS.</p> <p>Methods</p> <p>In homologous competitive binding study, the purified toxin was labelled with biotin and allowed to compete with unlabelled toxin for binding sites on CEM-SS and its dissociation constant (Kd) was determined. Comparisons were made with CCRF-SB, CCRF-HSB-2 and MCF-7. In heterologous competitive binding study, biotinylated toxin competition was determined with two other Bt toxins (crude Btj and crude Bt 22) and anticancer drugs (cisplatin, doxorubicin, etoposide, navelbine and methotrexate). To localise the binding site under the confocal microscope, the biotinylated toxin was tagged with FITC-conjugated streptavidin.</p> <p>Results</p> <p>Homologous competitive binding assays revealed decreasing binding affinity of Bt 18 toxin for CEM-SS, CCRF-SB, and CCRF-HSB-2 with Kd of 8.44 nM, 14.98 nM and 17.71 nM respectively. Kd for MCF-7 was not determined as the inhibitory concentration (IC₅₀) was not reached. Heterologous competitive study showed little competition (< 30%) between biotinylated Bt 18 toxin and all test compounds used. Confocal microscopy revealed binding of toxin at the periphery of the cell.</p> <p>Conclusions</p> <p>It was postulated that purified Bt 18 toxin binds on the cell surface of CEM-SS and the mechanism of cell death may differ from that of Btj toxin, Bt 22 toxin and all five anticancer drugs used in this study, since it did not significantly compete with these compounds for the same binding site.</p

Optimization of Pulsed Laser Ablation and Radio-Frequency Sputtering Tandem System for Synthesis of 2D/3D Al₂O₃-ZnO Nanostructures: A Hybrid Approach to Synthesis of Nanostructures for Gas Sensing Applications

In this paper, a unique hybrid approach to design and synthesize 2D/3D Al2O3-ZnO nanostructures by simultaneous deposition is presented. Pulsed laser deposition (PLD) and RF magnetron sputtering (RFMS) methods are redeveloped into a single tandem system to create a mixed-species plasma to grow ZnO nanostructures for gas sensing applications. In this set-up, the parameters of PLD have been optimized and explored with RFMS parameters to design 2D/3D Al2O3-ZnO nanostructures, including nanoneedles/nanospikes, nanowalls, and nanorods, among others. The RF power of magnetron system with Al2O3 target is explored from 10 to 50 W, while the ZnO-loaded PLD’s laser fluence and background gases are optimized to simultaneously grow ZnO and Al2O3-ZnO nanostructures. The nanostructures are either grown via 2-step template approach, or by direct growth on Si (111) and MgO substrates. In this approach, a thin ZnO template/film was initially grown on the substrate by PLD at ~300 °C under ~10 milliTorr (1.3 Pa) O2 background pressure, followed by growth of either ZnO or Al2O3-ZnO, using PLD and RFMS simultaneously under 0.1–0.5 Torr (13–67 Pa), and Ar or Ar/O2 background in the substrate temperate range of 550–700 °C. Growth mechanisms are then proposed to explain the formation of Al2O3-ZnO nanostructures. The optimized parameters from PLD-RFMS are then used to grow nanostructures on Au-patterned Al2O3-based gas sensor to test its response to CO gas from 200 to 400 °C, and a good response is observed at ~350 °C. The grown ZnO and Al2O3-ZnO nanostructures are quite exceptional and remarkable and have potential applications in optoelectronics, such in bio/gas sensors

Bio-harvesting and pyrolysis of the microalgae Botryococcus braunii

The microalgae Botryococcus braunii is widely recognized as a potentially important biofuel-feedstock whose commercial exploitation is limited by difficulties with its cultivation and harvesting. In this study, two B. braunii strains, Kossou-4 and Overjuyo-3 were successfully cultured at a 500 l-scale for 60-days. Harvesting by bio-flocculation with Aspergillus fumigatus at an optimum ratio of 1:40 of fungus to microalgal culture resulted in up to 98% recovery of biomass in the two strains. Ultimate analysis (C, N, H, S, ash, high heating value) and pyrolysis (analytical and preparative pyrolysis and GC–MS assays) showed that co-harvesting with fungi did not cause any impairment of the feedstock value of the microalgal biomass. This work represents the first report on the successful culturing and harvesting of these strains at a 500 l-scale using bio-flocculation. The use of A. fumigatus represents an efficient and economical method for the harvest of B. braunii for biofuel production

Pred-binding: large-scale protein–ligand binding affinity prediction

<p>Drug target interactions (DTIs) are crucial in pharmacology and drug discovery. Presently, experimental determination of compound–protein interactions remains challenging because of funding investment and difficulties of purifying proteins. In this study, we proposed two <i>in silico</i> models based on support vector machine (SVM) and random forest (RF), using 1589 molecular descriptors and 1080 protein descriptors in 9948 ligand–protein pairs to predict DTIs that were quantified by <i>K</i>_i values. The cross-validation coefficient of determination of 0.6079 for SVM and 0.6267 for RF were obtained, respectively. In addition, the two-dimensional (2D) autocorrelation, topological charge indices and three-dimensional (3D)-MoRSE descriptors of compounds, the autocorrelation descriptors and the amphiphilic pseudo-amino acid composition of protein are found most important for <i>K</i>_i predictions. These models provide a new opportunity for the prediction of ligand–receptor interactions that will facilitate the target discovery and toxicity evaluation in drug development.</p