Propagation of ultra-high energy protons in the nearby universe

We present a new calculation of the propagation of protons with energies above $10^{19}$ eV over distances of up to several hundred Mpc. The calculation is based on a Monte Carlo approach using the event generator SOPHIA for the simulation of hadronic nucleon-photon interactions and a realistic integration of the particle trajectories in a random extragalactic magnetic field. Accounting for the proton scattering in the magnetic field affects noticeably the nucleon energy as a function of the distance to their source and allows us to give realistic predictions on arrival energy, time delay, and arrival angle distributions and correlations as well as secondary particle production spectra.Comment: 12 pages, 9 figures, ReVTeX. Physical Review D, accepte

Time-resolved fluorescence of 2-aminopurine in DNA duplexes in the presence of the EcoP15I Type III restriction-modification enzyme

AbstractEcoP15I is a Type III DNA restriction and modification enzyme of Escherichia coli. We show that it contains two modification (Mod) subunits for sequence-specific methylation of DNA and one copy of a restriction endonuclease (Res) subunit for cleavage of DNA containing unmethylated target sequences. Previously the Mod2 dimer in the presence of cofactors was shown to use nucleotide flipping to gain access to the adenine base targeted for methylation (Reddy and Rao, J. Mol. Biol. 298 (2000) 597–610.). Surprisingly the Mod2 enzyme also appeared to flip a second adenine in the target sequence, one which was not subject to methylation. We show using fluorescence lifetime measurements of the adenine analogue, 2-aminopurine, that only the methylatable adenine undergoes flipping by the complete Res1Mod2 enzyme and that this occurs even in the absence of cofactors. We suggest that this is due to activation of the Mod2 core by the Res subunit

Goltz–Gorlin (focal dermal hypoplasia) and the microphthalmia with linear skin defects (MLS) syndrome: no evidence of genetic overlap

Focal dermal hypoplasia (FDH) is an X-linked developmental disorder with male lethality characterized by patchy dermal hypoplasia, skeletal and dental malformations, and microphthalmia or anophthalmia. Recently, heterozygous loss-of-function mutations in the PORCN gene have been described to cause FDH. FDH shows some clinical overlap with the microphthalmia with linear skin defects (MLS) syndrome, another X-linked male lethal condition, associated with mutations of HCCS in the majority of cases. We performed DNA sequencing of PORCN in 13 female patients with the clinical diagnosis of FDH as well as four female patients with MLS syndrome and no mutation in HCCS. We identified PORCN mutations in all female patients with FDH. Eleven patients seem to have constitutional PORCN alterations in the heterozygous state and two individuals are mosaic for the heterozygous sequence change in PORCN. No PORCN mutation was identified in the MLS-affected patients, providing further evidence that FDH and MLS do not overlap genetically. X chromosome inactivation (XCI) analysis revealed a random or slightly skewed XCI pattern in leukocytes of individuals with intragenic PORCN mutation suggesting that defective PORCN does not lead to selective growth disadvantage, at least in leukocytes. We conclude that the PORCN mutation detection rate is high in individuals with a clear-cut FDH phenotype and somatic mosaicism can be present in a significant proportion of patients with mild or classic FDH

The stepwise generation of multimetallic complexes based on a vinylbipyridine linkage and their photophysical properties

The versatile rhenium complex [ReCl(CO)3(bpyCuCH)] (HCuCbpy = 5-ethynyl-2,2’-bipyridine) is used to generate a series of bimetallic complexes through the hydrometallation of [MHCl(CO)(BTD)(PPh3)2] (M = Ru, Os; BTD = 2,1,3-benzothiadiazole). The ruthenium complex [Ru{CHvCH-bpyReCl(CO)3}Cl(BTD)(CO) (PPh3)2] was characterised structurally. Ligand exchange reactions with bifunctional linkers bearing oxygen and sulfur donors provide access to tetra- and pentametallic complexes such as [{M{CHvCHbpyReCl( CO)3}(CO)(PPh3)2}2(S2CNC4H8NCS2)] and Fe[C5H4CO2M{CHvCH-bpyReCl(CO)3}(CO)(PPh3)2]2. The effect of the group 8 metal on the photophysical properties of the rhenium centre was investigated using the complexes [Ru{CHvCH-bpyReCl(CO)3}Cl(BTD)(CO)(PPh3)2] and [M{CHvCH-bpyReCl(CO)3} {S2P(OEt)2}(CO)(PPh3)2] (M = Ru, Os). This revealed the quenching of the rhenium-based emission in favour of weak radiative processes based on the Ru and Os centres. The potential for exploiting this effect is illustrated by the reaction of [Ru{CHvCH-bpyReCl(CO)3}Cl(CO)(BTD)(PPh3)2] with carbon monoxide, which results in a 5-fold fluorescence enhancement in the dicarbonyl product, [Ru{CHvCH-bpyReCl (CO)3}Cl(CO)2(PPh3)2], as the quenching effect is disrupted