34 S: A New Opportunity for the Efficient Synthesis of Stable Isotope Labeled Compounds.

The synthesis of stable isotope labeled (SIL) complex drug molecules with a ≥3 mass unit increase from the parent compound is essential for drug discovery and development. Typical approaches that rely on 2 H, 13 C, and 15 N isotopes can be very challenging or even intractable, and can delay the drug development process. This work introduces a new concept for the synthesis of labeled compounds that relies on the use of 34 S. The synthetic utility of 34 S was demonstrated with the efficient synthesis of [34 S]phosphorothioates [34 S2 ]-PS-ODNs-TTT and [13 C, 15 N, 34 S]-ceftolozane. In addition, a procedure for the direct oxidation of phosphites to [34 S]phosphorothioates using elemental 34 S without isotope dilution was developed.

Study of the radioactivity induced in air by a 15-MeV proton beam.

Radioactivity induced by a 15-MeV proton beam extracted into air was studied at the beam transport line of the 18-MeV cyclotron at the Bern University Hospital (Inselspital). The produced radioactivity was calculated and measured by means of proportional counters located at the main exhaust of the laboratory. These devices were designed for precise assessment of air contamination for radiation protection purposes. The main produced isotopes were (11)C, (13)N and (14)O. Both measurements and calculations correspond to two different irradiation conditions. In the former, protons were allowed to travel for their full range in air. In the latter, they were stopped at the distance of 1.5 m by a beam dump. Radioactivity was measured continuously in the exhausted air starting from 2 min after the end of irradiation. For this reason, the short-lived (14)O isotope gave a negligible contribution to the measured activity. Good agreement was found between the measurements and the calculations within the estimated uncertainties. Currents in the range of 120-370 nA were extracted in air for 10-30 s producing activities of 9-22 MBq of (11)C and (13)N. The total activities for (11)C and (13)N per beam current and irradiation time for the former and the latter irradiation conditions were measured to be (3.60 ± 0.48) × 10(-3) MBq (nA s)(-1) and (2.89 ± 0.37) × 10(-3) MBq (nA s)(-1), respectively.

Selected scientific topics of the 11th International Isotope Symposium on the Synthesis and Applications of Isotopes and Isotopically Labeled Compounds.

This micro-review describes hot topics and new trends in isotope science discussed at the 11th International Isotope Symposium on the Synthesis and Applications of Isotopes and Isotopically Labeled Compounds from a personal perspective.

Development of an isotope-coded activity-based probe for the quantitative profiling of cysteine proteases.

Quantification studies of complex protein mixtures have been restricted mainly to whole cell extracts. Here we describe the synthesis of two sets of isotope-coded activity-based probes that allow quantitative functional proteomics experiments on the cathepsins.

Preparation of carrier-free 7Be by ion-exchange following charged particle and photonuclear reactions.

Carrier-free 7Be has been produced by 7Li(p,n)7Be and 10B(gamma,p2n)7Be (as well as 11B(gamma,p3n)7Be) reactions using a cyclotron and electron linear accelerator, respectively. Radiochemical methods for purification of the carrier-free radioactive 7Be isotope from the irradiated lithium and boron compounds have been investigated. A simple separation scheme is proposed.