PHAGE T4 mobE IS A REGULATED HOMING ENDONUCLEASE GENE THAT IS REQUIRED FOR THE trans HOMING OF THE DEFUNCT HOMING ENDONUCLEASE I- TevIII

The E. coli bacteriophage T4 has fifteen homing endonuclease gene insertions, five of which are predicted to be free-standing HNH homing endonucleases, named mobA to mobE. The focus of my studies is the mobE homing endonuclease gene found inserted between the conserved aerobic ribonucleotide reductase large (nrdA) and small subunits (nrdB). I showed that mobE is expressed during T4 infection, and a conserved Rho- independent transcriptional terminator regulates mobE expression. I demonstrated that mobE is a functional homing endonuclease gene that introduces a nick on the non-coding strand of the T2 nrdB gene. In T2xT4 mixed infections, mobE is inherited in -91.3% of the progeny and the inheritance was reduced to -72.8% in infections with T4 bearing a mobE internal deletion of the predicted HNH motif. Consequently, MobE activity also causes trans homing of the defunct I-TevIII homing endonuclease gene encoded within an intron interrupting the T2 nrdB gene

Letter, Gavin (?) W. Wilson to William A. Corbett [July 21, 1863]

Letter, Gavin (?) W. Wilson to William A. Corbett, July 21, 1863https://repository.stcloudstate.edu/joswilson-letters/1010/thumbnail.jp

Letter, Gavin (?) W. Wilson to Joseph P. Wilson [November 2 and 3, 1856]

Letter, Gavin (?) W. Wilson to Joseph P. Wilson, November 2 and 3, 1856https://repository.stcloudstate.edu/joswilson-letters/1007/thumbnail.jp

The gut in the beaker : missing the surfactants

Gastrointestinal drug administration is the preferred route for the majority of drugs however, the natural physiology and physicochemistry of the gastrointestinal tract is critical to absorption but complex and influenced by factors such as diet or disease. The pharmaceutical sciences drive for product consistency has led to the development of in vitro product performance tests whose utility and interpretation is hindered by the complexity, variability and a lack of understanding. This article explores some of these issues with respect to the drug, formulation and the presence of surfactant excipients and how these interact with the natural bile salt surfactants. Interactions start in the mouth and during swallowing but the stomach and small intestine present the major challenges related to drug dissolution, solubility, the impact of surfactants and supersaturation along with precipitation. The behaviour of lipid based formulations and the influence of surfactant excipients is explored along with the difficulties of translating in vitro results to in vivo performance. Possible future research areas are highlighted with the conclusion that, “a great deal of work using modern methods is still required to clarify the situation”

Statistical investigation of simulated fed intestinal media composition on the equilibrium solubility of oral drugs

Gastrointestinal fluid is a complex milieu and it is recognised that gut drug solubility is different to that observed in simple aqueous buffers. Simulated gastrointestinal media have been developed covering fasted and fed states to facilitate in vitro prediction of gut solubility and product dissolution. However, the combination of bile salts, phospholipids, fatty acids and proteins in an aqueous buffered system creates multiple phases and drug solubility is therefore a complex interaction between these components, which may create unique environments for each API. The impact on solubility can be assessed through a statistical design of experiment (DoE) approach, to determine the influence and relationships between factors. In this paper DoE has been applied to fed simulated gastrointestinal media consisting of eight components (pH, bile salt, lecithin, sodium oleate, monoglyceride, buffer, salt and pancreatin) using a two level D-optimal design with forty-four duplicate measurements and four centre points. The equilibrium solubility of a range of poorly soluble acidic (indomethacin, ibuprofen, phenytoin, valsartan, zafirlukast), basic (aprepitant, carvedilol, tadalafil, bromocriptine) and neutral (fenofibrate, felodipine, probucol, itraconazole) drugs was investigated. Results indicate that the DoE provides equilibrium solubility values that are comparable to literature results for other simulated fed gastrointestinal media systems or human intestinal fluid samples. For acidic drugs the influence of pH predominates but other significant factors related to oleate and bile salt or interactions between them are present. For basic drugs pH, oleate and bile salt have equal significance along with interactions between pH and oleate and lecithin and oleate. Neutral drugs show diverse effects of the media components particularly with regard to oleate, bile salt, pH and lecithin but the presence of monoglyceride, pancreatin and buffer have significant but smaller effects on solubility. There are fourteen significant interactions between factors mainly related to the surfactant components and pH, indicating that the solubility of neutral drugs in fed simulated media is complex. The results also indicate that the equilibrium solubility of each drug can exhibit individualistic behaviour associated with the drug’s chemical structure, physicochemical properties and interaction with media components. The utility of DoE for fed simulated media has been demonstrated providing equilibrium solubility values comparable with similar in vitro systems whilst also providing greater information on the influence of media factors and their interactions. The determination of a drug’s gastrointestinal solubility envelope provides useful limits that can potentially be applied to in silico modelling and in vivo experiments

Is graphene on copper doped?

Angle-resolved photoemission spectroscopy (ARPES) and X-ray photoemission spectroscopy have been used to characterise epitaxially ordered graphene grown on copper foil by low-pressure chemical vapour deposition. A short vacuum anneal to 200 °C allows observation of ordered low energy electron diffraction patterns. High quality Dirac cones are measured in ARPES with the Dirac point at the Fermi level (undoped graphene). Annealing above 300 °C produces n-type doping in the graphene with up to 350 meV shift in Fermi level, and opens a band gap of around 100 meV. Dirac cone dispersion for graphene on Cu foil after vacuum anneals (left: 200 °C, undoped; right: 500 °C, n-doped). Centre: low energy electron diffraction from graphene on Cu foil after 200 °C anneal. Data from Antares (SOLEIL)