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We investigate the ultrafast photoinduced dynamics of the cyclic disulfide 1,2-dithiane upon 200 nm excitation by time-resolved photoelectron spectroscopy and show that the S-S bond breaks on an ultrafast time scale. This stands in stark contrast to excitation at longer wavelengths where the initially excited S 1 state evolves as the wavepacket is guided towards a conical intersection with S 0 by a torsional motion involving a partially broken bond between the sulfur atoms. This process at lower excitation energy allows for efficient (re-)population of S 0 , rendering dithiane intact. At 200 nm, in contrast, the excitation leads to a manifold of higher excited states, S n , that are primarily of Rydberg character. We are able to follow the gradual transition from the initially excited state to the dissociative receiver state in real time. The Rydberg states are intersected by a repulsive valence state that mediates a transition to the repulsive S 2 surface. Therefore, we propose that the resulting diradical will eventually break apart on a longer timescale. The findings imply that upon going from UV-B to UV-C light the structural integrity of the disulfide moiety is compromised and proteins irradiated in this range will not be able to reform the initial tertiary structure, leading to loss of function., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Cyclopropane carboxylic acid was fed to Saccharopolyspora erythraea NRRL 18643 (6-deoxyerythromycin producer), resulting in the production of 6-deoxy-13-cyclopropyl-erythromycin B. These studies provide further evidence that deoxyerythronolide B synthase has a relaxed specificity for the starter unit.

Avermectins with a wide range of novel C-25 substituents have been prepared by feeding carboxylic acids or their biosynthetic precursors to a Streptomyces avermitilis mutant strain ATCC 53568. This organism lacks the ability to form isobutyric and S-2-methylbutyric acids from their 2-oxo acid precursors and thus is unable to produce natural avermectins unless supplied with these acids. The novel avermectins produced by mutational biosynthesis possess broad-spectrum antiparasitic activity.

UK-63,052 complex, a new group of quinomycin-like antibiotics comprising UK-63,052 (factor A), UK-63,598 (factor C), UK-65,662 (factor B) and several uncharacterised minor components, is produced by a new subspecies of the genus Streptomyces for which the name Streptomyces braegensis Dietz subsp. japonicus, is proposed. The strain, N617-29, is characterised by a negative melanin reaction, grey aerial mycelium, spiral spore chains and smooth or slightly warty spores. Structure determination has identified UK-63,052, C56H68N10O14S2, UK-63,598, C53H62N10O14S2 and UK-65,662, C55H66N10O14S2 as quinaldic acid substituted quinomycins with unusual bridgehead sulfur substitution as shown in Fig. 3.

Peritoneoscopic examination has now been accepted throughout the world as a safe diagnostic procedure in lieu of laparotomy in selected cases. Laparotomies for diagnostic purposes alone should be condemned. Peritoneoscopy should not be done without a definite purpose and the procedure should not be expected to accomplish more than the purpose for which it is done. Indications for the procedure are set forth in detail. Experience has established definite contraindications, which are reviewed. The procedure is especially indicated for patients who are aged, emaciated, anemic, or poor surgical risks for any reason. All patients having ascites of undetermined cause should be examined by peritoneoscopy. The method is especially indicated for examination of patients with liver disease of all types, for pelvic examinations, for use to determine existence of ectopic pregnancy, and for tumor localization. Considerable use was made of the procedure during World War II to determine the extent and site of intra-abdominal injuries caused by crushing, explosions, and falls from high places. The procedure permits early and correct diagnosis, early decision as to the advisability of operation, and determination as to operability in cases of malignant gastric lesions. It is a safe method for obtaining biopsy specimens from intra-abdominal tissue and organs. Accuracy of diagnosis in cases in which the method can be used is considerably greater with peritoneoscopic examination than with clinical information alone.