Influence of valence band states on the core hole screening in lanthanide perovskite compounds

Investigation on core level and valence band photoelectron spectra of lanthanide perovskite samples (Ag _x La_1–x CoO₃;x<0,3) and reinvestigations of metallic lanthanum and La-oxide layers are reported. Differences in preparation method during perovskite formation are leading to different quality of sample purity and different electronic properties. This could be followed by changes in the density of states near the Fermi energy. On the other hand the screening mechanism after ionization of a La 3d core hole is affected by the relative energy position of occupied valence band states with respect to the empty La 4f ^* level in the core ionized state. Changes in La 3d line profile are discussed as changes in multi electron processes (e.g. shake up or energy gain) during photoionization. We attribute the two electron process during photoemission of La 3d electrons to the well screened energy gain transition in LaCoO₃, whereas the two electron process results in a shake up transition in La₂O₃ and La(OH)₃.     

Cartilage degradation by stimulated human neutrophils: reactive oxygen species decrease markedly the activity of proteolytic enzymes

BACKGROUND: Although neutrophilic granulocytes clearly contribute to cartilage degradation in rheumatic diseases, it is unclear if reactive oxygen species (ROS) or proteolytic enzymes are the most important components in cartilage degradation and how they interact. RESULTS: Neutrophils were stimulated by chemicals conferring a different degree of ROS formation and enzyme release. Supernatants of neutrophils were incubated with thin slices of pig articular cartilage. Supernatants of cartilage were assayed by NMR spectroscopy, MALDI-TOF mass spectrometry and relevant biochemical methods. Stimulation conditions of neutrophils correlated well with the extent of cartilage degradation. Due to the release of different enzymes, cartilage degradation could be best monitored by NMR since mainly low-mass degradation products were formed. Astonishingly, the suppression of the formation of ROS resulted in decreased cartilage degradation. CONCLUSION: ROS formed by neutrophils are not directly involved in cartilage degradation but influence the activity of proteolytic enzymes, which are the main effectors of cartilage degradation.     

(Z)-3-p-tolylsulfinylacrylonitrile as a chiral dienophile: diels-alder reactions with furan and acyclic dienes

The behavior of (Z)-3-p-tolylsulfinylacrylonitrile (1) as a chiral dienophile has been evaluated from its reactions with furan and acyclic dienes. Electrostatic interactions of the cyano group with the sulfinyl one restrict the conformational mobility around the C-S bond, thus controlling the pi-facial selectivity, which is almost complete in all cases, the approach of the diene from the less-hindered face of the dienophile (that bearing the lone electron pair) in the predominant rotamer being the favored one. The regioselectivity is also completely controlled by the cyano group. Additionally, the reactivity of compound 1 as well as its endo-selectivity are both higher than those observed for the corresponding (Z)-3-sulfinylacrylates, thus proving the potential of sulfinylnitriles as chiral dienophiles.