Magnetic properties of Fe-doped NiO nanoparticles.

Undoped and Fe-doped NiO nanoparticles were successfully synthesized using a lyophilization method and systematically characterized through magnetization techniques over a wide temperature range, with varying intensity and frequency of the applied magnetic fields. The Ni1-xFexO nanoparticles can be described by a core-shell model, which reveals that Fe doping enhances exchange interactions in correlation with nanoparticle size reduction. The nanoparticles exhibit a superparamagnetic blocking transition, primarily attributed to their cores, at temperatures ranging from above room temperature to low temperatures, depending on the Fe-doping level and sample synthesis temperature. The nanoparticle shells also exhibit a transition at low temperatures, in this case to a cluster-glass-like state, caused by the dipolar magnetic interactions between the net magnetic moments of the clusters. Their freezing temperature shifts to higher temperatures as the Fe-doping level increases. The existence of an exchange bias interaction was observed, thus validating the core-shell model proposed.

Relação da infecção do papiloma vírus humano (HPV) com a apresentação de carcinomas de células escamosas de regiões da orofaringe / Relationship of human papilloma virus (HPV) infection with the presentation of squamous cell carcinomas from regions of the oropharynx

O papiloma vírus humano (HPV) é classificado como uma doença sexualmente transmissível, sendo esse vírus de DNA de fita dupla associado convencionalmente ao câncer de colo de útero, entretanto, em estudos mais recentes esse vírus também foi associado ao carcinoma de células escamosas de orofaringe (CCEO). Nesse sentido, essa re-visão sistemática tem como objetivo mostrar a relação entre o HPV e o CCEO. Dessa forma, foram utilizadas as bases de dados PubMed, The Cochrane Library, BioOne, Lilacs e Scielo com artigos publicados no período entre janeiro de 2010 e junho de 2020 com publicações nos idiomas: português, espanhol e inglês, respeitando os cri-térios de inclusão e exclusão. Foram considerados elegíveis 11 artigos que apresentaram a relação com a infecção de orofaringe e com o HPV. Apesar do alto número de artigos encontrados pela busca da relação com o HPV com neoplasias em diferentes regiões do corpo, foi possível compreender a relação presente entre o CCEO e a infecção causada pelo HPV através de um modelo de estratificação PRISMA. Assim, foi demonstrado, além da presença dessa relação, a necessidade de métodos diagnósticos mais rápidos, acessíveis e eficazes para apresentação correta entre patologia e fator etiológico. (AU)

Human papilloma virus (HPV) is classified as a sexually transmitted disease, in which this double-stranded DNA virus is often associated with cervical cancer. However, in more recent studies, this virus has also been associated with oropharyngeal squamous cell carcinoma (OSCC). Therefore, this systematic review aims to show the relationship between HPV and CCEO. Thus, Pubmed, The Cochrane Library, Bioone, Lilacs and Scielo databases were used with articles published between January 2010 and June 2020 encompassing publications in Portuguese, Spanish and English, respecting the inclusion and exclusion criteria. A total of eleven articles that presented a relationship with oropharyngeal infection and HPV were considered eligible. Despite the high number of articles found by the search for the association between HPV and neoplasms in different regions of the body, it was possible to understand the association between CCEO and the infection caused by HPV, through a PRISMA stratification model. Thus, it was demonstrated, in addition to the presence of this association, the need for faster, more accessible and effective diagnostic methods for the correct presentation of pathology and etiological factor. (AU)

Spin-Glass Transitions in Zn1-xFexO Nanoparticles.

Monophasic Zn1-xFexO nanoparticles with wurtzite structure were synthesized in the 0 ≤ x ≤ 0.05 concentration range using a freeze-drying process followed by heat treatment. The samples were characterized regarding their optical, structural, and magnetic properties. The analyses revealed that iron doping of the ZnO matrix induces morphological changes in the crystallites. Iron is substitutional for zinc, trivalent and distributed in the wurtzite lattice in two groups: isolated iron atoms and iron atoms with one or more neighboring iron atoms. It was also shown that the energy band gap decreases with a higher doping level. The samples are paramagnetic at room temperature, but they undergo a spin-glass transition when the temperature drops below 75 K. The magnetic frustration is attributed to the competition of magnetic interactions among the iron moments. There are a superexchange interaction and an indirect exchange interaction that is provided by the spin (and charge) itinerant carriers in a spin-polarized band situated in the vicinity of the Fermi level of the Fe-doped ZnO semiconductor. The former interaction actuates for an antiferromagnetic coupling among iron ions, whereas the latter constitutes a driving force for a ferromagnetic coupling that weakens, decreasing the temperature. Our results strongly contribute to the literature because they elucidate the controversies reported in the literature for the magnetic state of the Fe-doped ZnO system.

Switching the Spin-Crossover Phenomenon by Ligand Design on Imidazole-Diazineiron(II) Complexes.

The iron(II) complexes of two structural isomers of 2-(1 H-imidazol-2-yl)diazine reveal how ligand design can be a successful strategy to control the electronic and magnetic properties of complexes by fine-tuning their ligand field. The two isomers only differ in the position of a single diazinic nitrogen atom, having either a pyrazine (Z) or a pyrimidine (M) moiety. However, [Fe(M)3](ClO4)2 is a spin-crossover complex with a spin transition at 241 K, whereas [Fe(Z)3](ClO4)2 has a stable magnetic behavior between 2 and 300 K. This is corroborated by temperature-dependent Mössbauer spectra showing the presence of a quintet and a singlet state in equilibrium. The temperature-dependent single-crystal X-ray diffraction results relate the spin-crossover observed in [Fe(M)3](ClO4)2 to changes in the bond distances and angles of the coordination sphere of iron(II), hinting at a stronger σ donation of ligand Z in comparison to ligand M. The UV/vis spectra of both complexes are solved by means of the multiconfigurational wave-function-based method CASPT2 and confirm their different spin multiplicities at room temperature, as observed in the Mössbauer spectra. Calculations show larger stabilization of the singlet state in [Fe(Z)3]2+ than in [Fe(M)3]2+, stemming from the slightly stronger ligand field of the former (506 cm-1 in the singlet). This relatively weak effect is indeed capable of changing the spin multiplicity of the complexes and causes the appearance of the spin transition in the M complex.

Applications of docking and molecular dynamic studies on the search for new drugs against the biological warfare agents Bacillus anthracis and Yersinia pestis.

The fear of biological warfare agents (BWA) use by terrorists is the major concern of the security agencies and health authorities worldwide today. The non-existence of vaccines or drugs against most BWA and the possibility of genetic modified strains has turned the search for new drugs to a state of urgency. Fast in silico techniques are, therefore, perfect tools for this task once they can quickly provide structures of several new lead compounds for further experimental work. Here we try to present a mini-review on docking and molecular dynamics simulations studies applied to the drug design against the BWA Bacillus anthracis and Yersinia pestis.

Antimalarial activity of potential inhibitors of Plasmodium falciparum lactate dehydrogenase enzyme selected by docking studies.

The Plasmodium falciparum lactate dehydrogenase enzyme (PfLDH) has been considered as a potential molecular target for antimalarials due to this parasite's dependence on glycolysis for energy production. Because the LDH enzymes found in P. vivax, P. malariae and P. ovale (pLDH) all exhibit ∼90% identity to PfLDH, it would be desirable to have new anti-pLDH drugs, particularly ones that are effective against P. falciparum, the most virulent species of human malaria. Our present work used docking studies to select potential inhibitors of pLDH, which were then tested for antimalarial activity against P. falciparum in vitro and P. berghei malaria in mice. A virtual screening in DrugBank for analogs of NADH (an essential cofactor to pLDH) and computational studies were undertaken, and the potential binding of the selected compounds to the PfLDH active site was analyzed using Molegro Virtual Docker software. Fifty compounds were selected based on their similarity to NADH. The compounds with the best binding energies (itraconazole, atorvastatin and posaconazole) were tested against P. falciparum chloroquine-resistant blood parasites. All three compounds proved to be active in two immunoenzymatic assays performed in parallel using monoclonals specific to PfLDH or a histidine rich protein (HRP2). The IC(50) values for each drug in both tests were similar, were lowest for posaconazole (<5 µM) and were 40- and 100-fold less active than chloroquine. The compounds reduced P. berghei parasitemia in treated mice, in comparison to untreated controls; itraconazole was the least active compound. The results of these activity trials confirmed that molecular docking studies are an important strategy for discovering new antimalarial drugs. This approach is more practical and less expensive than discovering novel compounds that require studies on human toxicology, since these compounds are already commercially available and thus approved for human use.