Recognition and Sensing of Nucleoside Monophosphates by a Dicopper(II) Cryptate

The dicopper complex of a bis-tren cryptand in which the spacer consists of two furane subunits connected in 2,2' by a -CH2- fragment selectively recognizes guanosine monophosphate with respect to other nucleoside monophospates (NMPs) in a MeOH/water solution at pH 7. Recognition is efficiently signaled through the displacement of the indicator 6-carboxyfluorescein bound to the receptor, monitoring its yellow fluorescent emission. Titration experiments evidenced the occurrence of several simultaneous equilibria involving 1:1 and 2:1 receptor/NMP and receptor/indicator complexes. It was demonstrated that the added NMP displaces the indicator from the 2:1 receptor/indicator complex, forming the 1:1 receptor/ analyte inclusion complex. Recognition selectivity is thus ascribed to the nature of nucleotide donor atoms involved in the coordination and their ability to encompass the CuII-CuII distance within the cryptate

DNA profiling, telomere analysis and antioxidant properties as tools for monitoring ex situ seed longevity

Background and Aims The germination test currently represents the most used method to assess seed viability in germplasm banks, despite the difficulties caused by the occurrence of seed dormancy. Furthermore, seed longevity can vary considerably across species and populations from different environments and studies related to the eco-physiological processes underlying such variations are still limited in their depth. The aim of the present work was the identification of reliable molecular markers that might help monitoring seed deterioration. Methods Dry seeds were subjected to artificial aging and collected at different time points for molecular/biochemical analyses. DNA damage was measured using the RAPD (Random Amplified Polymorphic DNA) approach while the seed antioxidant profile was obtained using both the DPPH (1,1-diphenyl, 2-picrylhydrazyl) assay and the Folin Ciocalteu reagent method. Electron Paramagnetic Resonance (EPR) provided profiles of free radicals. Quantitative RealTime-Polymerase Chain Reaction (QRT-PCR) was used to assess the expression profiles of the antioxidant genes MT2 (Type 2 Metallothionein) and SOD (Superoxide Dismutase). A modified QRT-PCR protocol was used to determine telomere length. Key Results The RAPD profiles highlighted different capacities of the two Silene species to overcome DNA damage induced by artificial aging. The antioxidant profiles of dry and rehydrated seeds revealed that the high-altitude taxon Silene acaulis was characterised by a lower antioxidant specific activity. Significant up-regulation of the MT2 and SOD genes was observed only in the rehydrated seeds of the low-altitude species. Rehydration resulted in telomere lengthening in both Silene species. Conclusions Different seed viability markers have been selected for plant species showing inherent variation of seed longevity. RAPD analysis, quantification of redox activity of non enzymatic antioxidant compounds and gene expression profiling provide deeper insights to study seed viability during storage. Telomere lengthening is a promising tool to discriminate between short- and long-lived species

EPR study of cation-radicals of cyclic alkenes in chlorofluorocarbon matrices

By gamma irradiation of cycloheptatriene, bicyclo(3.3.0)octene and dehydrodicyclopentadiene in chlorofluorocarbon matrices at 77 K the radical cations generated by electron loss from the parent molecules have been obtained and their electronic structure analyzed by EPR spectroscopy and by INDO and MNDO-PM3 molecular orbital calculations. On warming above 77 K these species undergo deprotonation to form neutral radicals. In the case of dicyclopentadiene the primary radical-cation is not stable at 77 K but decomposes probably by ring opening giving a bis-allylilic type cation-radical

Matrix isolation and ESR study of unstable intermediate generated by radiation techniques from metal carbonyl complexes

Exposure of MeTHF solutions of M(CO)6 (M=Cr, Mo, W) to γ-rays or photoionization with TMPD at 77 K gives paramagnetic species attributed to 17 electron radical anions M(CO) . The excess energy arising from the primary electron capture process is responsible of the fast M—CO bond breaking which prevents the trapping of 19-electron species M(CO) . Experimental and EHT-MO calculated g-tensors of the pentacoordinated anions are consistent with a square pyramidal C4ν structure having the unpaired electron in a molecular orbital with a high dz2 character

Dicopper(II) and dicopper(III) complexes with a double-ring octaaza macrocycle

The bicyclic amine I was prepd. in 30% yield by condensation of tetra-Et 1,1,2,2-ethanetetracarboxylate with 1,4,8,11-tetraazaundecane in refluxing EtOH for 2 days and formed a 1:2 complex with Cu2+ in aq. soln. The 2Cu2+-I complex showed weak metal-metal interaction and was easily oxidized to the trivalent state by 2 consecutive one-electron steps sepd. by 110 mV