Effect of argon implantation on solid-state dewetting: control of size and surface density of silicon nanocrystals.

Thermally induced solid-state dewetting of ultra-thin films on insulators is a process of prime interest, since it is capable of easily forming nanocrystals. If no particular treatment is performed to the film prior to the solid-state dewetting, it is already known that the size, the shape and the density of nanocrystals is governed by the initial film thickness. In this paper, we report a novel approach to control the size and the surface density of silicon nanocrystals based on an argon-implantation preliminary surface treatment. Using 7.5 nm thin layers of silicon, we show that increasing the implantation dose tends to form smaller silicon nanocrystals with diameter and height lower than 50 nm and 30 nm, respectively. Concomitantly, the surface density is increased by a factor greater than 20, going from 5 µm-2 to values over 100 µm-2.

Inappropriate prescribing in elderly people with diabetes admitted to hospital.

AIMS: To assess inappropriate prescribing in older people with diabetes mellitus during the month prior to a hospitalization, using tools on potentially inappropriate medicines (PIMs) and potential prescribing omissions (PPOs) and comparing inappropriate prescribing in patients with without diabetes. METHODS: In an observational, prospective multicentric study, we assessed inappropriate prescribing in 672 patients aged 75 years and older during hospital admission. The Beers, Screening Tool of Older Person's Prescriptions (STOPP) and Screening Tool to Alert Doctors to Right Treatment (START) criteria and Assessing Care of Vulnerable Elders (ACOVE-3) medicine quality indicators were used. We analysed demographic and clinical factors associated with inappropriate prescribing. RESULTS: Of 672 patients, 249 (mean age 82.4 years, 62.9% female) had a diagnosis of diabetes mellitus. The mean number of prescribing drugs per patient with diabetes was 12.6 (4.5) vs. 9.4 (4.3) in patients without diabetes (P < 0.001). Of those patients with diabetes, 74.2% used 10 or more medications; 54.5% of patients with diabetes had at least one Beers-listed PIM, 68.1% had at least one STOPP-listed PIM, 64.6% had at least one START-listed PPO and 62.8% had at least one ACOVE-3-listed PPO. Except for the Beers criteria, these prevalences were significantly higher in patients with diabetes than in those without. After excluding diabetes-related items from these tools, only STOPP-listed PIMs remained significantly higher among patients with diabetes (P = 0.04). CONCLUSIONS: Polypharmacy is common among older patients with diabetes mellitus. Inappropriate prescribing is higher in older patients with diabetes, even when diabetes-related treatment is excluded from the inappropriate prescribing evaluation.

Towards Q-PCR of pathogenic bacteria with improved electrochemical double-tagged genosensing detection.

A very sensitive assay for the rapid detection of pathogenic bacteria based on electrochemical genosensing has been designed. The assay was performed by the PCR specific amplification of the eaeA gene, related with the pathogenic activity of Escherichia coli O157:H7. The efficiency and selectivity of the selected primers were firstly studied by using standard Quantitative PCR (Q-PCR) based on TaqMan fluorescent strategy. The bacteria amplicon was detected by using two different electrochemical genosensing strategies, a highly selective biosensor based on a bulk-modified avidin biocomposite (Av-GEB) and a highly sensitive magneto sensor (m-GEC). The electrochemical detection was achieved in both cases by the enzyme marker HRP. The assay showed to be very sensitive, being able to detect 4.5 ng microl(-1) and 0.45 ng microl(-1) of the original bacterial genome after only 10 cycles of PCR amplification, when the first and the second strategies were used, respectively. Moreover, the electrochemical strategies for the detection of the amplicon showed to be more sensitive compared with Q-PCR strategies based on fluorescent labels such as TaqMan probes.

In situ DNA amplification with magnetic primers for the electrochemical detection of food pathogens.

A sensitive and selective genomagnetic assay for the electrochemical detection of food pathogens based on in situ DNA amplification with magnetic primers has been designed. The performance of the genomagnetic assay was firstly demonstrated for a DNA synthetic target by its double-hybridization with both a digoxigenin probe and a biotinylated capture probe, and further binding to streptavidin-modified magnetic beads. The DNA sandwiched target bound on the magnetic beads is then separated by using a magneto electrode based on graphite-epoxy composite. The electrochemical detection is finally achieved by an enzyme marker, anti-digoxigenin horseradish peroxidase (HRP). The novel strategy was used for the rapid and sensitive detection of polymerase chain reaction (PCR) amplified samples. Promising resultants were also achieved for the DNA amplification directly performed on magnetic beads by using a novel magnetic primer, i.e., the up PCR primer bound to magnetic beads. Moreover, the magneto DNA biosensing assay was able to detect changes at single nucleotide polymorphism (SNP) level, when stringent hybridization conditions were used. The reliability of the assay was tested for Salmonella spp., the most important pathogen affecting food safety.

Synthesis and biological activity of novel acridinylidene and benzylidene thiazolidinediones.

A novel set of acridinylidene thiazolidinediones and benzylidene thiazolidinediones was synthesized by nucleophilic addition of cyanoacrylates. Some of these compounds were evaluated for their glucose lowering capability and their effects on the triglyceride level in alloxan diabetic mice.

Synthesis and schistosomicidal activity of new substituted thioxo-imidazolidine compounds.

Synthesis and physico-chemical properties of 3-benzyl-5-(4-fluoro-benzylidene)-1-methyl-2-thioxo-imidazolidin-4-ones, 5-benzylidene-3-(4-nitro-benzyl)-2-thioxo-imidazolidin-4-ones and 4-acridin-9-ylmethylene-1-benzyl-5-thioxo-imidazolidin-2-ones compounds are described. These thioxo-imidazolidine derivatives were prepared by alkylation and condensation with 4-fluoro-benzaldehyde or nucleophilic Michael addition with cyanoacrylates. The schistosomicidal activity of 3-benzyl-5-(4-fluoro-benzylidene)-1-methyl-2-thioxo-imidazolidin-4-one compounds was evaluated.

Cloning, sequence and regulation of expression of the lexA gene of Aeromonas hydrophila.

The lexA gene of Aeromonas hydrophila (Ah) has been isolated by using a specific one-step cloning system. The Ah LexA repressor is able to block Escherichia coli (Ec) SOS gene expression and is likely to be cleaved by the activated RecA protein of this bacterial species after DNA damage. Ah lexA would encode a protein of 207 amino acids (aa), which is 75% identical to the LexA repressor of Ec. Two Ec-like SOS boxes have been located upstream from Ah lexA, the distance between them being 4 bp, whereas this same distance in Ec lexA is 5 bp. The structure and sequence of the DNA-binding domain of the LexA repressor of Ec, as well as the region at which its hydrolysis occurs, are highly conserved in Ah LexA. Moreover, a residue of the region implicated in the specific cleavage reaction, and which is present in all known RecA-cleavable repressors, is changed in the Ah LexA. Expression of Ah lexA is DNA-damage inducible in both the Ah and Ec genetic backgrounds to the same extent. In contrast, Ec lexA is poorly induced in DNA-injured Ah cells.

Cloning and sequencing of the gyrA gene from the plant pathogen Erwinia carotovora.

The gyrA gene of Erwinia carotovora subsp. carotovora has been cloned and sequenced. The deduced protein possessed 86% identity with the Escherichia coli GyrA protein. E. carotovora gyrA was also shown to complement an E. coli gyrA43ts mutation.

Two different operons for the same function: comparison of the Salmonella typhimurium nrdAB and nrdEF genes.

By using a P22 phage-mediated cloning system, the nrdAB genes of Salmonella typhimurium (St), encoding a ribonucleotide reductase (RR) of class I, have been isolated. The coding regions of the St nrdAB operon show a very high identity with those of the homologous operon of Escherichia coli (Ec). Nevertheless, there are significant differences in their promoter regions since, although the promoters of both operons present two DnaA boxes, these boxes are located downstream from the transcription start point in St, being upstream in Ec. Moreover, the deduced amino-acid sequences of the St nrdAB showed a very limited overall identity (28%) with the products of St nrdEF, which encode a second class-I RR. Expression of St nrdAB and nrdEF is inducible by hydroxyurea, an inhibitor of RR activity. Alignment of the promoter regions of the nrdAB and nrdEF operons of both St and Ec reveals the presence of a consensus sequence. St is the first organism from which two different RR belonging to the same biochemical class are known.

Inhibition of Trypanosoma cruzi trypanothione reductase by acridines: kinetic studies and structure-activity relationships.

Series of 9-amino and 9-thioacridines have been synthesized and studied as inhibitors of trypanothione reductase (TR) from Trypanosoma cruzi, the causative agent of Chagas' disease. The compounds are structural analogues of the acridine drug mepacrine (quinacrine), which is a competitive inhibitor of the parasite enzyme, but not of human glutathione reductase, the closest related host enzyme. The 9-aminoacridines yielded apparent K(i) values for competitive inhibition between 5 and 43 microM. The most effective inhibitors were those with the methoxy and chlorine substituents of mepacrine and NH(2) or NHCH(CH(3))(CH(2))(4)N(Et)(2) at C9. Detailed kinetic analyses revealed that in the case of 9-aminoacridines more than one inhibitor molecule can bind to the enzyme. In contrast, the 9-thioacridine derivatives inhibit TR with mixed-type kinetics. The kinetic data are discussed in light of the three-dimensional structure of the TR-mepacrine complex. The conclusion that structurally very similar acridine compounds can give rise to completely different inhibition patterns renders modelling studies and quantitative structure-activity relationships difficult.