Ferric-ion-photosensitized damage to DNA by hydroxyl and non-hydroxyl radical mechanisms.

Iron(III) and UVA (320-400 nm) light strongly diminished the transforming activity of Haemophilus influenzae DNA in the presence of oxygen. Iron(III) alone in the absence of light had no measurable effect on the transforming activity. The chelating agent ethylenediaminetetraacetic acid (EDTA) conferred virtually complete protection, but hydroxyl radical scavengers (mannitol, methanol, ethanol, isopropanol and dimethyl sulfoxide) inhibited only a small fraction of the inactivation. Treatment of plasmid DNA (pBR322) with iron(III) results in the conversion of the covalently closed circular form of the plasmid to open circles and ultimately to the linear form. Concomitant with the alteration in the conformation of the plasmid, the ability to transform Escherichia coli was reduced. In model systems, iron(III) photoreacted with the DNA backbone causing nicking and double-strand breakage. The results are consistent with a mechanism involving a preliminary complexation of iron(III) by DNA followed by the generation of reactive free radicals other than .OH. We suggest that bound iron, or other UV-absorbing transition metal complexes, may be chromophores capable of causing DNA damage in the long-wave near-UV region.     

Evaluation of the effect of silicon on the carbonization process of Colombian semi-anthracites

The environmental impacts associated with the exploitation and transformation of fossil resources aggravate the planet's situation in terms of climate change. Due to this, this paper studies an alternative use of mineral coal as a precursor to obtaining new materials with different properties to the starting coals. The thermal degradation of two Colombian semi-anthracites is analyzed through the thermogravimetry (TG) technique coupled to a Fourier transform infrared spectroscopy (FTIR) equipment from room temperature (25 °C) to 900 °C, at a heating rate of 10 K min^?1 in an inert atmosphere. The catalytic effect of the addition of silicon to these samples before being subjected to a carbonization process is evaluated during this process. The results indicated that the primary reaction occurs in the temperature range between 400 and 680 °C, where the highest mass loss rate was observed. At the end of the heating process, the TG profile of the samples with silicon addition showed losses between 14.33 and 18.82% in mass, these values being slightly higher compared to the starting and demineralized samples. The release of water, light gases such as CO₂, CH₄, and species such as toluene, phenol and formic acid was identified in most of the samples. The presence of silica seems to favor the release of all these species, being more evident in one of the semi-anthracites studied. According to the results obtained, it is proved that the presence of silicon in samples subjected to carbonization processes has a catalytic effect that improves some characteristics of the new materials obtained, thus contributing to the use of carbon to get new materials.

     

A Functional Equation Arising from Simultaneous Utility Representations

Suppose that two classes of utility representations of preferences, one additive and one increasing increments, hold simultaneously over uncertain binary alternatives (gambles). This assumption leads to the functional equation $$ f[h(x-y)+y]=f[h(x)]-f[h(y)]+f(y)\qquad (\kappa >x\geq y\geq 0), $$ and to the inequality h(z) ≤ z (z ∈ [0, κ[), where the functions ? and h are strictly increasing maps of the real interval [0, κ[ onto the real intervals [0, λ[ and [0, μ[, respectively, κ, λ, μ ∈]0, ∞]. We present all solutions under the additional assumption of (first-order) differentiability.     

Fusion reactions with the one-neutron halo nucleus (15)C

The structure of (15)C, with an s(1/2) neutron weakly bound to a closed-neutron shell nucleus (14)C, makes it a prime candidate for a one-neutron halo nucleus. We have for the first time studied the cross section for the fusion-fission reaction (15)C+(232)Th at energies in the vicinity of the Coulomb barrier and compared it to the yield of the neighboring (14)C+(232)Th system measured in the same experiment. At sub-barrier energies, an enhancement of the fusion yield by factors of 2-5 was observed for (15)C, while the cross sections for (14)C match the trends measured for (12,13)C.     

Activity of Cuban propolis extracts on Leishmania amazonensis and Trichomonas vaginalis

In this paper we analyzed the antiprotozoal effects of eighteen Cuban propolis extracts (brown, red and yellow type) collected in different geographic areas, using Leishmania amazonensis (as a model of intracellular protozoa) and Trichomonas vaginalis (as a model of extracellular protozoa). All evaluated propolis extracts caused inhibitory effect on intracellular amastigotes of L. amazonensis. However, cytotoxicity on peritoneal macrophages from BALB/c mice was observed. Only five samples decreased the viability of T. vaginalis trophozoites at concentrations lower than 10 microg/mL. No correlation between the type of propolis and antiprotozoal activity was found. Cuban propolis extracts demonstrated activity against both intracellular and extracellular protozoa model, as well as the potentialities of propolis as a natural source to obtain new antiprotozoal agents.     

The associated primes of local cohomology modules over rings of small dimension

Let R be a commutative Noetherian local ring of dimension d, I an ideal of R, and M a finitely generated R-module. We prove that the set of associated primes of the local cohomology module H ⁱ _I (M) is finite for all i≥ 0 in the following cases: (1) d≤ 3; (2) d= 4 and $R$ is regular on the punctured spectrum; (3) d= 5, R is an unramified regular local ring, and M is torsion-free. In addition, if $d>0$ then H ^{d − 1} _I (M) has finite support for arbitrary R, I, and M. Received: 31 October 2000 / Revised version: 8 January 2001     

The synthesis of 3-hydroxymethyldibenzo[b,f]thiepin 5,5-dioxide,a prostaglandin antagonist

An economic synthesis of 3-hydroxymethyldibenzo[b,f]thiepin 5,5-dioxide, a novel prostaglandin antagonist, is described. The key step in the synthesis is the formation of a carboxyphenylacetic acid by carboxylation of a toluic acid dianion, followed by cyclisation to the tricyclic ketone. Readily available starting materials are used in the synthesis and conditions have been found at each stage to give pure intermediates, requiring little purification, in high yield.