POSTIRRADIATION PROPERTIES OF A UV-SENSITIVE VARIANT OF CHO

Abstract A UV-hypersensitive mutant of Chinese hamster ovary (CHO) cells, termed 43-3B, has been used in a comparative study with the wild type CHO in order to determine the involvement of repair in several postirradiation phenomena. 43-3B has the same growth rate and chromosome number as the wild type CHO-9. It is hypersensitive to UV irradiation (D₀ of 0.3 J/m² as compared to 3.2 J/m² for the wild type). 43-3B shows only about 17% of the UV-stimulated unscheduled DNA repair synthesis of CHO-9 as measured by autoradiography. When breaks in supercoiled chromatin are measured after UV by the nucleoid sedimentation method, the mutant appears to be capable of carrying out only limited incision. A much reduced ability to recover control rates of semiconservative DNA synthesis after UV irradiation was observed in the repair-deficient 43-3B cell line, suggesting that the removal of UV-induced replication blocks by excision repair is the most important factor in allowing recovery of UV-inhibited DNA synthesis. Recovery of colony-forming ability between fractionated UV exposures was observed in the wild type CHO-9, but little recovery was seen in 43-3B. This indicates that excision repair capability can also be important in split-fluence recovery.     

The gold(III) tetra­chloride salt of L‐cocaine

The title salt, methyl (1R,2R,3S,5S,8S)‐3‐benzoyl­oxy‐8‐methyl‐8‐aza­bicyclo­[3.2.1]octane‐2‐carboxyl­ate tetra­chloro­aurate(III), (C₁₇H₂₂NO₄)[AuCl₄], has its protonated N atom intra­molecularly hydrogen bonded to the O atom of the methoxy­carbonyl group [N⋯O = 2.755 (6) Å and N—H⋯O = 136°]. Two close inter­molecular C—H⋯O contacts exist, as well as five C—H⋯Cl close contacts. The [AuCl₄]⁻ anion was found to be distorted square planar.     

A Facile One Stage Synthesis of Oxazolines Under Microwave Irradiation

A rapid, high yielding procedure for the synthesis of 2-substituted oxazolines has been achieved under microwave irradiation from alkyl and aryl nitriles and β-amino alcohols using a mild Lewis acid catalyst.     

Parameters Tied to Treewidth

Treewidth is a graph parameter of fundamental importance to algorithmic and structural graph theory. This article surveys several graph parameters tied to treewidth, including separation number, tangle number, well‐linked number, and Cartesian tree product number. We review many results in the literature showing these parameters are tied to treewidth. In a number of cases we also improve known bounds, provide simpler proofs, and show that the inequalities presented are tight.     

Catalysts for convenient aerobic alcohol oxidations in air: systematic ligand studies in Pd/pyridine systems

We report highly convenient Pd catalysts for the aerobic oxidation of alcohols, which are generated in situ by combining commercially available catalyst precursors. Systematic optimizations of the L- and X-type ligand environment and the employed additive allow the use of air as the sole oxidant without formation of Pd black. The resulting novel protocol provides quantitative yields of a broad variety of ketones and aldehydes.     

Synthetic studies towards the penicisulfuranols: Synthesis of an advanced spirocyclic diketopiperazine intermediate

The 2,5-diketopiperazine (DKP) moiety is a core feature of many natural products and medicinally relevant scaffolds. As part of our efforts directed towards a total synthesis of penicisulfuranol B, we have developed and report herein: (1) the preparation of an N-hydroxy diketopiperazine intermediate accessible via a molybdenum-mediated oxidation of a parent diketopiperazine, and (2) further synthetic studies leading to a novel spirocyclic dihydrobenzofuran-containing diketopiperazine.