Systematic analysis of desorption chemical ionization (DCI) mass spectra of nucleic acids--7

The positive ion and negative ion pyrolysis mass spectra of the herring sperm DNA have been studied using desorption chemical ionization. The positive ion desorption chemical ionization spectra have been produced with CH4, i-C4H10, NH3, HCl and Cl2; the negative ones with N2O/CH4, N2O/i-C4H10, Cl2, CCl4, HCl and via electron capture. These spectra have been compared with the electron impact ionization spectra. We have observed an important increase of sensitivity when negative ionization has replaced the positive ionization mode. The series of diagnostic ions resulting from direct chemical ionization belong to the family of base + reagent ion X [BH + X] and base + X - HX ion [B]. Their abundance has increased considerably compared to the electron impact spectra. The application of these new diagnostic ions in nucleic acid studies is interesting especially for the much higher abundance of the usually weak dG fragment ion obtained in the negative ionization mode. The dG-base segment of the DNA is the most nucleophilic centre of the whole nucleic acid and is implicated in numerous important biochemical reactions involving, for example, proteins.     

The structure of cyclolinopeptide A in chloroform refined by RDC measurements

Three‐dimensional structures of molecules traditionally assigned from nuclear Overhauser effects and vicinal coupling constants are recently complemented by measurements of residual dipolar couplings. Residual dipolar couplings measured in a stretched poly(dimethylsiloxane) gel were used to determine the structure of cyclolinopeptide A in chloroform solution at ?50 °C. After structure refinement, conformational details of main cluster were discussed in relation to crystal and nuclear Overhauser effect derived structures. Copyright © 2014 European Peptide Society and John Wiley & Sons, Ltd.     

Secretory and absorptive activity of oesophageal epithelium: evidence of circulating mucosubstances

Summary The space between the oesophageal basal and prickle epithelial cells appears empty by standard ultrastructural preparative techniques. Fixation of human oesophageal biopsies with a variety of agents, including tannic acid, glutaraldehyde—lysine, cetylpyridinium chloride and Ruthenium Red shows that this space is filled with mucosubstances, some free, some attached to the cells as a glycocalyx. There is evidence that this material is secreted constitutively by the basal and prickle cells. This secretion may be changed or blocked by incubating oesophageal biopsies in the presence of colchicine or dinitrophenol. Incubation at 16°C has the same effect. Absorption from the intercellular space may be followed using the fluid phase marker, horseradish peroxidase. Early endosomes may also be shown by their acid phosphatase activity. Incubation of biopsies at 20–22°C allows early endosomes to accumulate material, but not pass it on the late endosomes.     

NMR spectra of some cyanosteroids

The MMR Spectra of thirty-four cyanosteroids and of thirty-four model steroids are discussed. The chemical shifts of the protons at C-18, C-19 and C-21 are used to study the cyanosteroid structures and the specific corrections Δδ^∗ are calculated.     

A Better Half: The Ethics of Hemicorporectomy Surgery

This paper discusses the ethical issues related to hemicorporectomy surgery, a radical procedure that removes the lower half of the body in order to prolong life. The literature on hemicorporectomy (HC), also called translumbar amputation, has been nearly silent on the ethical considerations relevant to this rare procedure. We explore five aspects of the complex landscape of hemicorporectomy to illustrate the broader ethical questions related to this extraordinary procedure: benefits, risks, informed consent, resource allocation and justice, and loss and the lived body.