New ternary copper(II) complexes of l-alanine and heterocyclic bases: DNA binding and oxidative DNA cleavage activity

Four new ternary copper(II) complexes of α-amino acid having polypyridyl bases of general formulation [Cu(l-ala)(B)(H₂O)](X) (1-4), where l-ala is l-alanine, B is an N,N-donor heterocyclic base, viz. 2,2′-bipyridine (bpy, 1), 1,10-phenanthroline (phen, 2) and 5,6-phenanthroline dione (dione, 3), dipyrido[3,2:2′,3′-f]quinoxaline (dpq, 4), and X = / are synthesized, characterized by various spectroscopic and X-ray crystallographic methods. The complexes show a distorted square-pyramidal (4 + 1) CuN₃O₂ coordination geometry. The one-electron paramagnetic complexes (1-4) display a low energy d-d band near 600 nm in aqueous medium and show a quasi-reversible cyclic voltammetric response due to one-electron Cu(II)/Cu(I) reduction near −100 mV (versus SCE) in DMF-0.1 M TBAP. Binding interactions of the complexes with calf thymus DNA (CT-DNA) were investigated by UV-Vis absorption titration, ethidium bromide displacement assay, viscometric titration experiment and DNA melting studies. All the complexes barring the complexes 1 and 3 are avid binder to the CT-DNA in the DNA minor groove giving an order: 4 > 2 ? 1, 3. The complexes 2 and 4 show appreciable chemical nuclease activity in the presence of 3-mercaptopropionic acid (MPA) as a reducing agent. Hydroxyl radical was investigated to be the DNA cleavage active species. Control experiments in the presence of distamycin-A show primarily minor groove-binding propensity for the complexes 2 and 4 to the DNA.     

Singlet oxygen production in thylakoid membranes during photoinhibition as detected by EPR spectroscopy

Exposure of isolated spinach thylakoids to high intensity illumination (photoinhibition) results in the well-characterized impairment of Photosystem II electron transport, followed by degradation of the D1 reaction centre protein. In the present study we demonstrate that this process is accompanied by singlet oxygen production. Singlet oxygen was detected by EPR spectroscopy, following the formation of stable nitroxide radicals from the trapping of singlet oxygen with a sterically hindered amine TEMP (2,2,6,6-tetramethylpiperidine). There was no detectable singlet oxygen production during anaerob photoinhibition or in the presence of sodium-azide. Comparing the kinetics of the loss of PS II function and D1 protein with that of singlet oxygen trapping suggests that singlet oxygen itself or its radical product initiates the degradation of D1.Abbreviations HEPES 4-(2-hydroxyethyl)-1-piperazine ethanesulphonle acid - PS Photosystem - TEMP 2,2,6,6-tetramethylpiperidine - TEMPO 2,2,6,6-tetramethylpiperidine-1-oxyl     

Apports de l’acquisition TDM couplée à la scintigraphie pulmonaire dans l’exploration d’une suspicion d’embolie pulmonaire

Pulmonary embolism is a frequent disease difficult to diagnose because of heterogeneous clinical presentation. Pulmonary embolism diagnosis requires additional examinations, which are guided by clinical probability scores. The ventilation/perfusion scintigraphy is a validated technic in pulmonary embolism diagnosis strategies, which represents one of its most important indications. In the past years, the technique of scintigraphy evolved with the appearance of hybrid cameras, allowing the realization of tomoscintigraphy coupled with computerised tomodensitometry (CT). One of the major interests of this technique is the possibility of considering alternative diagnosis in case of negative result of scintigraphy. The purpose of this article is to offer nuclear medicine physicians a review of the alternative diagnoses that can be found during pulmonary ventilation/perfusion tomoscintigraphy according to the underlying scintigraphic and morphological abnormalities. In this review, we will first on diseases responsible for: a mismatch (pathological perfusion and normal ventilation), an inverted mismatch (normal perfusion and pathological ventilation) and for associated disorders in ventilation and in perfusion patterns (identically abnormal perfusion and ventilation). The final part will address some specific CT features that can be encountered on a low dose CT centered on thorax.