41 research outputs found
Triplet NOAH supersequences optimised for small molecule structure characterisation
No full textA series of NMR supersequences are presented for the time‐efficient structure characterisation of small molecules in the solution state. These triplet sequences provide HMBC, HSQC, and one homonuclear correlation experiment of choice according to the NMR by Ordered Acquisition using 1H detection principle. The experiments are demonstrated to be compatible with non‐uniform sampling schemes and may be acquired and processed under full automation
Measuring spin relaxation rates using satellite exchange NMR spectroscopy
No full textAn approach to the indirect measurement of nuclear spin relaxation rates of low‐magnetogyric ratio (γ) nuclei using the process of satellite exchange is described. The method does not require the observation of, or even the ability to provide radio‐frequency pulses to, the low‐γ nucleus, but requires this to be scalar coupled to an NMR observable nucleus, such as 31P or 1H, making it especially attractive for the study of diamagnetic transition metals. In situations where spin relaxation is dominated by chemical shift anisotropy (CSA), the determination of the longitudinal spin relaxation time constant (T1) of the metal becomes possible, as illustrated for 195Pt and 107/109Ag
NOAH: NMR Supersequences for Small Molecule Analysis and Structure Elucidation
No full textNested NMR experiments combining up to five conventional NMR pulse sequences into one supersequence are introduced. The core two-dimensional NMR techniques routinely employed in small molecule NMR, such as HSQC, HMQC, HMBC, COSY, NOESY, TOCSY and similar, can be recorded in a single measurement dramatically reducing the data collection time and increasing sample throughput for basic NMR applications to structure elucidation and verification in synthetic, medicinal and natural product chemistry
Elizaveta Svilova and Soviet documentary film
No full textThe focus of my research is Soviet documentary filmmaker, Elizaveta Svilova (1900-75), most commonly remembered, if at all, as the wife and collaborator of acclaimed Soviet film pioneer, Dziga Vertov (1896-1954). Having worked with her husband for many years, Svilova continued her career as an independent director-editor after Vertov fell out of favour with the Central Committee. Employed at the Central Studio for Documentary Film, a state-initiated studio, Svilova’s films were vehicles of rhetoric, mobilised to inform, educate and persuade the masses. She draws on visual symbols familiar to audiences and organises them according to the semiotic theories – namely techniques of dialecticism and linkage – attributed to the Soviet montage school of the 1920s.On-screen credits indicate that, during the period 1939 to 1956, Svilova was the director-editor of over 100 documentaries and newsreel episodes, yet this corpus of films has received very little critical attention. As my thesis aims to demonstrate, the reasons for the lack of attention to Svilova’s films are partly due to her husband’s eminent status – the rules whereby we construct film history have resulted in Svilova’s contribution being absorbed into Vertov’s – and this is related to the long-standing tendency within film criticism to marginalise the female artist. My thesis also touches on issues regarding curatorial and archival policies, and provides an opportunity to rethink early film history and the modes through which historiographic and filmographic knowledge are transmitted
An approach to the manzamine alkaloids modelled on a biogenetic theory
No full textImproved conditions for the preparation of 17 are reported together with the synthesis of an advanced intermediate 38 en route to keramaphidin B, a plausible biogenetic precursor to the manzamines
Isolation, separation, identification, and quantification of bioactive methylated flavone regioisomers by UHPLC-MS/MS
No full textMethylated flavones, commonly found in many plants of the Brassicaceae family, have potent antioxidant and anticancer activity with diverse therapeutic potential. However, the specific regioisomers of methylated flavones can have significantly different biochemical and potentially therapeutic properties as shown by various bioassays but analytically differentiating these compounds has been technically challenging and rarely reported. In this study, we demonstrate differentiation and identification of selected bioactive methylated flavone regioisomers, namely 5,7,3′-trihydroxy-4′-methoxyflavone, and 5,7,4′-trihydroxy-3′-methoxyflavone extracted from Coronopus didymus, a member of the Brassicaceae family, using ultra-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry (UPLC-ESI-QTOF-MS/MS). Characteristic MS/MS product ions produced from neutral loss of carbon monoxide, and a methyl radical from the [M-H]– ion, exhibited differential relative abundances attributed to different structural stabilities under the same activation and collision-induced dissociation conditions. MS/MS also provided structural information which was sufficient to differentiate the methylated regioisomers and determine the position of the methyl group based on interpretation of their respective fragmentation patterns. Quantification showed 5,7,4′-trihydroxy-3′-methoxyflavone was at least 1.60 mg per 10 g plant material in C. didymus extracts. This study demonstrates a straightforward and novel approach to rapidly differentiate, identify and quantify regio-isomeric methylated flavone natural products using reversed-phase UPLC-MS/MS
Disciplining the Spectator: Subjectivity, the Body and Contemporary Spectatorship
No full textIn this thesis the author argues that although questions of the spectator’s corporeal engagement with film are much neglected by film theory, the body is nevertheless a central term within contemporary cinema, in its mode of address, as a locus of anxiety in media effects debate, and as site of disciplinary practices. And while the thesis begins by demonstrating both the socially and historically constructed nature of spectatorship, and the specific practices that work to create contemporary cinema’s corporeal address, the latter half of the dissertation devotes itself to revealing the regulatory implications of this physical address. That is, the author shows that cinema’s perceived capacity of affect the body of the spectator is a profound source of cultural anxiety. But more importantly, through an analysis of the films Funny Games, Irréversible, Wolf Creek, and the genre of ‘torture porn’ more generally, what is revealed in these final chapters is that the regulation of cinema in the contemporary era is less a question of the institutionalised censorship of texts, and more a question of regulating the ‘self’. In this respect, the author demonstrates the specific disciplinary practices that attempt to present the problem of violent, and sexually violent, imagery not as a textual issue per se, but a question of the formation of appropriate spectatorial relations. Moreover, this study begins the process of teasing out the ways in which the contemporary spectator is induced to see the problem of media violence as one that can be resolved through what
Foucault would term, techniques of the self
Clerodane Diterpenoids from an Edible Plant <i>Justicia insularis</i>: Discovery, Cytotoxicity, and Apoptosis Induction in Human Ovarian Cancer Cells
No full textObjectives: The toxicity of chemotherapeutic anticancer drugs is a serious issue in clinics. Drug discovery from edible and medicinal plants represents a promising approach towards finding safer anticancer therapeutics. Justicia insularis T. Anderson (Acanthaceae) is an edible and medicinal plant in Nigeria. This study aims to discover cytotoxic compounds from this rarely explored J. insularis and investigate their underlying mechanism of action. Methods: The cytotoxicity of the plant extract was evaluated in human ovarian cancer cell lines and normal human ovarian surface epithelia (HOE) cells using a sulforhodamine B assay. Bioassay-guided isolation was carried out using column chromatography including HPLC, and the isolated natural products were characterized using GC-MS, LC-HRMS, and 1D/2D NMR techniques. Induction of apoptosis was evaluated using Caspase 3/7, 8, and 9, and Annexin V and PI based flow cytometry assays. SwissADME and SwissTargetPrediction web tools were used to predict the molecular properties and possible protein targets of identified active compounds. Key finding: The two cytotoxic compounds were identified as clerodane diterpenoids: 16(α/β)-hydroxy-cleroda-3,13(14)Z-dien-15,16-olide (1) and 16-oxo-cleroda-3,13(14)E-dien-15-oic acid (2) from the Acanthaceous plant for the first time. Compound 1 was a very abundant compound (0.7% per dry weight of plant material) and was shown to be more potent than compound 2 with IC50 values in the micromolar range against OVCAR-4 and OVCAR-8 cancer cells. Compounds 1 and 2 were less cytotoxic to HOE cell line. Both compounds induced apoptosis by increasing caspase 3/7 activities in a concentration dependent manner. Compound 1 further increased caspase 8 and 9 activities and apoptosis cell populations. Compounds 1 and 2 are both drug like, and compound 1 may target various proteins including a kinase. Conclusions: Clerodane diterpenoids (1 and 2) in J. insularis were identified as cytotoxic to ovarian cancer cells via the induction of apoptosis, providing an abundant and valuable source of hit compounds for the treatment of ovarian cancer
In vivo antihyperglycaemic and antihyperlipidemic activities and chemical constituents of Solanum anomalum
No full textSolanum anomalum is a plant used ethnomedically for the treatment of diabetes. The study was aimed to validate ethnomedical claims in rat model and identify the likely antidiabetic compounds. Leaf extract (70–210 mg/kg/day) and fractions (140 mg/kg/day) of S. anomalum were evaluated in hyperglycaemic rats induced using alloxan for effects on blood glucose, lipids and pancreas histology. Phytochemical characterisation of isolated compounds and their identification were performed using mass spectrometry and NMR spectroscopy. Bioinformatics tool was used to predict the possible protein targets of the identified bioactive compounds. The leaf extract/fractions on administration to diabetic rats caused significant lowering of fasting blood glucose of the diabetic rats during single dose study and on repeated administration of the extract. The hydroethanolic leaf extracts also enhanced glucose utilization capacity of the diabetic rats and caused significant lowering of glycosylated hemoglobin levels and elevation of insulin levels in the serum. Furthermore, triglycerides, LDL-cholesterol, and VLDL-cholesterol levels were lowered significantly, while HDL–cholesterol levels were also elevated in the treated diabetic rats. There was absence or few pathological signs in the treated hyperglycaemic rat pancreas compared to that present in the pancreas of control group. Diosgenin, 25(R)-diosgenin-3-O-a-L-rhamnopyranosyl-(1?4)-ß-D-glucopyranoside, uracil, thymine, 1-octacosanol, and octacosane were isolated and identified. Protein phosphatases along with secreted proteins are predicted to be the major targets of diosgenin and the diosgenin glycoside. These results suggest that the leaf extract/fractions of S. anomalum possess antidiabetic and antihyperlipidemic properties, offer protection to the pancreas and stimulate insulin secretion, which can be attributable to the activities of its phytochemical constituents
Self-assembly of Russian doll concentric porphyrin nanorings
No full textElectronic communication between concentric macrocycles with wave functions that extend around their circumferences can lead to remarkable behavior, as illustrated by multiwalled carbon nanotubes and photosynthetic chlorophyll arrays. However, it is difficult to hold one π-conjugated molecular ring inside another. Here, we show that ring-in-ring complexes, consisting of a 6-porphyrin ring locked inside a 12-porphyrin ring, can be assembled by placing different metals in the two rings (zinc and aluminum). A bridging ligand with carboxylate and imidazole binding sites forms spokes between the two rings, resulting in a highly cooperative supramolecular self-assembly process. Excitation is transferred from the inner 6-ring to the outer 12-ring of this Russian doll complex within 40 ps. These complexes lead to a form of template-directed synthesis in which one nanoring promotes formation of a larger concentric homologous ring; here, the effective template is an eight-component noncovalent assembly. Russian doll templating provides a new approach to amplifying the size of a covalent nanostructure
