Investigation of boron carbide and iridium thin films, an enabling technology for future x-ray telescopes.

We present an experimental examination of iridium and boron carbide thin-film coatings for the purpose of fabricating x-ray optics. We use a combination of x-ray reflectometry and x-ray photoelectron spectroscopy to model the structure, composition, density, thickness, and micro-roughness of the thin films. We demonstrate in our analyses how the two characterization techniques are complementary, and from this we derive that an overlayer originating from atmospheric contamination with a thickness between 1.

An Unusual Cause of Failure to Ventilate.

We report an unusual case of endotracheal tube failure. It was due to a manufacturing defect in the internal white plastic piece that is normally depressed by the luer-lock syringe within the blue pilot balloon. Prior to use, the endotracheal tube was tested and functioned normally.

Near-fatal kinking of mammary graft due to emphysematous lung disease.

Left internal mammary artery grafting is commonly used in elective coronary artery bypass graft surgery. We report a near-fatal case with graft kinking upon sternal closure due to distended, emphysematous lungs impinging on the mammary graft. After the sternum was closed, the patient suffered a severe hemodynamic deterioration.

Transformations of the FeS Clusters of the Methylthiotransferases MiaB and RimO, Detected by Direct Electrochemistry.

The methylthiotransferases (MTTases) represent a subfamily of the S-adenosylmethionine (AdoMet) radical superfamily of enzymes that catalyze the attachment of a methylthioether (-SCH) moiety on unactivated carbon centers. These enzymes contain two [4Fe-4S] clusters, one of which participates in the reductive fragmentation of AdoMet to generate a 5'-deoxyadenosyl 5'-radical and the other of which, termed the auxiliary cluster, is believed to play a central role in constructing the methylthio group and attaching it to the substrate. Because the redox properties of the bound cofactors within the AdoMet radical superfamily are so poorly understood, we have examined two MTTases in parallel, MiaB and RimO, using protein electrochemistry.

Trifluoroselenomethionine: A New Unnatural Amino Acid.

Trifluoroselenomethionine (TFSeM), a new unnatural amino acid, was synthesized in seven steps from N-(tert-butoxycarbonyl)-l-aspartic acid tert-butyl ester. TFSeM shows enhanced methioninase-induced cytotoxicity, relative to selenomethionine (SeM), toward HCT-116 cells derived from human colon cancer. Mechanistic explanations for this enhanced activity are computationally and experimentally examined.