Osmium Models of Intermediates Involved in Catalytic Reactions of Alkylidenecyclopropanes

The complex [OsCp­{κ³-<i>P</i>,<i>C</i>,<i>C</i>-PⁱPr₂[C­(CH₃)CH₂]}­(CH₃CN)]­PF₆ (<b>1</b>) reacts with (2-pyridyl)­methylenecyclopropane, at room temperature, to give initially the cyclobutylidene derivative [Os­(η⁵-C₅H₅)­(CCH₂CH₂CH-<i>o</i>-C₅H₄N)­{PⁱPr₂[C­(Me)CH₂]}]­PF₆ (<b>2</b>), as a result of the ring expansion of the alkylidenecyclopropane unit. Over time complex <b>2</b> rearranges into the cyclobutene derivative [Os­(η⁵-C₅H₅)­{η²-C­(CHCH₂CH₂)-<i>o</i>-C₅H₄N}­{PⁱPr₂[C­(Me)CH₂]}]­PF₆ (<b>3</b>). The reaction of <b>1</b> with (2-pyridyl)­methylenecyclopropane at room temperature also affords the phosphinomethanide metallacycle [Os­(η⁵-C₅H₅)­{κ⁴-<i>P</i>,<i>C</i>^a,<i>C</i>^b,<i>N</i>-PⁱPr₂[C^a(Me)­CH₂CH)­(C^bCH₂CH₂-<i>o</i>-C₅H₄N]}]­PF₆ (<b>4</b>) as a minor product, which becomes the major product of the reaction at 45 °C. This osmacyclopentane results from the C–C coupling of the isopropenyl substituent of the phosphine ligand and the organic substrate. In acetone at 75 °C, the reaction of <b>1</b> with (2-pyridyl)­methylenecyclopropane leads to the 2-alkylidene-1-osmacyclobutane [Os­(η⁵-C₅H₅)­{κ³-<i>N</i>,<i>C</i>^a,<i>C</i>^b-C^a(CH₂C^bH₂)­(CH-<i>o</i>-C₅H₄N)}­{PⁱPr₂[C­(Me)CH₂]}]­PF₆ (<b>5</b>), as a consequence of the oxidative addition of one of the C­(sp²)–C­(sp³) bonds of the cyclopropane unit of the substrate to the osmium atom, along with <b>6</b>, a diastereomer of <b>4</b>. Complexes <b>3</b>–<b>5</b> have been characterized by X-ray diffraction analysis. DFT calculations suggest that all of the reaction products are derived from a common key 1-osma-2-azacyclopent-3-ene intermediate (<b>D</b>)

Osmium Models of Intermediates Involved in Catalytic Reactions of Alkylidenecyclopropanes

The complex [OsCp­{κ³-<i>P</i>,<i>C</i>,<i>C</i>-PⁱPr₂[C­(CH₃)CH₂]}­(CH₃CN)]­PF₆ (<b>1</b>) reacts with (2-pyridyl)­methylenecyclopropane, at room temperature, to give initially the cyclobutylidene derivative [Os­(η⁵-C₅H₅)­(CCH₂CH₂CH-<i>o</i>-C₅H₄N)­{PⁱPr₂[C­(Me)CH₂]}]­PF₆ (<b>2</b>), as a result of the ring expansion of the alkylidenecyclopropane unit. Over time complex <b>2</b> rearranges into the cyclobutene derivative [Os­(η⁵-C₅H₅)­{η²-C­(CHCH₂CH₂)-<i>o</i>-C₅H₄N}­{PⁱPr₂[C­(Me)CH₂]}]­PF₆ (<b>3</b>). The reaction of <b>1</b> with (2-pyridyl)­methylenecyclopropane at room temperature also affords the phosphinomethanide metallacycle [Os­(η⁵-C₅H₅)­{κ⁴-<i>P</i>,<i>C</i>^a,<i>C</i>^b,<i>N</i>-PⁱPr₂[C^a(Me)­CH₂CH)­(C^bCH₂CH₂-<i>o</i>-C₅H₄N]}]­PF₆ (<b>4</b>) as a minor product, which becomes the major product of the reaction at 45 °C. This osmacyclopentane results from the C–C coupling of the isopropenyl substituent of the phosphine ligand and the organic substrate. In acetone at 75 °C, the reaction of <b>1</b> with (2-pyridyl)­methylenecyclopropane leads to the 2-alkylidene-1-osmacyclobutane [Os­(η⁵-C₅H₅)­{κ³-<i>N</i>,<i>C</i>^a,<i>C</i>^b-C^a(CH₂C^bH₂)­(CH-<i>o</i>-C₅H₄N)}­{PⁱPr₂[C­(Me)CH₂]}]­PF₆ (<b>5</b>), as a consequence of the oxidative addition of one of the C­(sp²)–C­(sp³) bonds of the cyclopropane unit of the substrate to the osmium atom, along with <b>6</b>, a diastereomer of <b>4</b>. Complexes <b>3</b>–<b>5</b> have been characterized by X-ray diffraction analysis. DFT calculations suggest that all of the reaction products are derived from a common key 1-osma-2-azacyclopent-3-ene intermediate (<b>D</b>)

Analysis of Autoantibody Profiles in Osteoarthritis Using Comprehensive Protein Array Concepts

Osteoarthritis (OA) is the most common rheumatic disease and one of the most disabling pathologies worldwide. To date, the diagnostic methods of OA are very limited, and there are no available medications capable of halting its characteristic cartilage degeneration. Therefore, there is a significant interest in new biomarkers useful for the early diagnosis, prognosis, and therapeutic monitoring. In the recent years, protein microarrays have emerged as a powerful proteomic tool to search for new biomarkers. In this study, we have used two concepts for generating protein arrays, antigen microarrays, and NAPPA (nucleic acid programmable protein arrays), to characterize differential autoantibody profiles in a set of 62 samples from OA, rheumatoid arthritis (RA), and healthy controls. An untargeted screen was performed on 3840 protein fragments spotted on planar antigen arrays, and 373 antigens were selected for validation on bead-based arrays. In the NAPPA approach, a targeted screening was performed on 80 preselected proteins. The autoantibody targeting CHST14 was validated by ELISA in the same set of patients. Altogether, nine and seven disease related autoantibody target candidates were identified, and this work demonstrates a combination of these two array concepts for biomarker discovery and their usefulness for characterizing disease-specific autoantibody profiles

Enterotoxigenic Potential of Staphylococcus intermedius

Staphylococcal food poisoning (SFP) caused by enterotoxigenic staphylococci is one of the main food-borne diseases. In contrast to Staphylococcus aureus, a systematic screening for the enterotoxins has not yet been performed on the genomic level for the coagulase-positive species S. intermedius. Therefore, the enterotoxigenic potential of 281 different veterinary (canine, n = 247; equine, n = 23; feline, n = 9; other, n = 2) and 11 human isolates of S. intermedius was tested by using a multiplex PCR DNA-enzyme immunoassay system targeting the staphylococcal enterotoxin genes sea, seb, sec, sed, and see. Molecular results were compared by in vitro testing of enterotoxin production by two immunoassays. A total of 33 (11.3%) S. intermedius isolates, including 31 (12.6%) canine isolates, 1 equine isolate, and 1 human isolate, tested positive for the sec gene. In vitro production of the respective enterotoxins was detected in 30 (90.9%) of these isolates by using immunological tests. In contrast, none of 65 veterinary specimen-derived isolates additionally tested and comprising 13 (sub)species of coagulase-negative staphylococci were found to be enterotoxigenic. This study shows on both molecular and immunological levels that a substantial number of S. intermedius isolates harbor the potential for enterotoxin production. Since evidence for noninvasive zoonotic transmission of S. intermedius from animal hosts to humans has been documented, an enterotoxigenic role of this microorganism in SFP via contamination of food products may be assumed