A multi-methodological study of the (K,Ca)-variety of the zeolite merlinoite

A multi-methodological study of the (K,Ca)-variety of the zeolite merlinoite from Fosso Attici, Sacrofano, Italy was carried out on the basis of electron microprobe analysis in wavelength dispersive mode, singlecrystal X-ray diffraction (at 100 K), Raman and infrared spectroscopy. The chemical formula of the merlinoite from Fosso Attici is (Na0.37K5.69)\u3a3=6.06(Mg0.01Ca1.93Ba0.40)\u3a3=2.34(Fe3+0.02Al10.55Si21.38)\u3a3=31.9O64\u38719.6H2O, compatible with the ideal chemical formula K6Ca2[Al10Si22O64]\u38720H2O. Anisotropic structure refinements confirmed the symmetry and the framework model previously reported (space group Immm, a = 14.066(5),b = 14.111(5), c = 9.943(3) \uc5 at 100 K). Refinement converged with four cationic sites and sixH2Osites; refined bond distances of the framework tetrahedra suggest a highly disordered Si/ Al-distribution. The Raman spectrum of merlinoite (collected between 100 and 4000 cm 121) is dominated by a doublet of bands between 496\u2013422 cm 121, assigned to tetrahedral T\u2013O\u2013T symmetric bending modes. T\u2013O\u2013T antisymmetric stretching is also observed; stretching and bending modes of the H2O molecules are only clearly visiblewhen using a blue laser. The single-crystal near-infrared spectrum shows a very weak band at 6823 cm 121, assigned to the first overtone of the O\u2013H stretching mode, and a band at 5209 cm 121, due to the combination of H2O stretching and bendingmodes.Avery broad and convoluted absorption, extending from 3700 to 3000 cm 121 occurs in the H2O stretching region, while the \u3bd2 bending mode of H2O is found at 1649 cm 121. The powder midinfrared spectrum of merlinoite between 400\u20131300 cm 121 is dominated by tetrahedral T\u2013O\u2013T symmetric and antisymmetric stretches. Raman and Fourier-transform infrared spectroscopy spectra of merlinoite and phillipsite provide a quick identification tool for these zeolites, which are often confused due to their close similarity

Cancrinite-group minerals at non-ambient conditions: a model of the thermo-elastic and structure behavior

The cancrinite-group of minerals comprises more than ten species sharing the [CAN]-topology of the tetrahedral framework. Their microporous structure has wide 12-ring channels, bound by columns of cages (can units). Besides the aluminosilicate composition of the framework (with the only exception of tiptopite, having instead Be and P), the minerals of the cancrinite group show a remarkable chemical variability concerning the extraframework population. Two subgroups can be identified according to the content of the can units: the first with Na-H2O (cancrinite and vishnevite) and the second with Ca-Cl chains (balliranoite and davyne). The channels are stuffed by cations, anions and molecules. In Nature, cancrinite-group minerals occur in the late/hydrothermal stages of alkaline (SiO2)-undersaturated magmatism and in related effusive or contact rocks. On the technological front, cancrinite-group compounds have been proposed as stable storage form for alkaline waste solutions, of which are common precipitation products. We aimed to model the thermo-elastic behavior and the mechanisms of (P,T)-induced structure evolution of cancrinite-group minerals, focusing to the role played by the extraframework population. The study was restricted to the following (CO3)-rich and (SO4)-rich end-members: cancrinite {[(Na,Ca)6(CO3)1.2-1.7][Na2(H2O)2][Al6Si6O24]}, vishnevite {[(Na,Ca,K)6(SO4)][Na2(H2O)2][Al6Si6O24]}, balliranoite {[(Na,Ca)6(CO3)1.2-1.7][Ca2Cl2][Al6Si6O24]} and davyne {[(Na,Ca,K)6((SO4),Cl)][Ca2Cl2][Al6Si6O24]}. Their high-P and low-T (T < 293 K) behavior was investigated by in situ single crystal X-ray diffraction, using diamond-anvil cells and (N2)-cryo-devices, respectively. Though sharing a similar volume compressibility [i.e., ~ 0.021 GPa-1, KV0 ~ 47 GPa] and thermal expansivity [i.e., ~ 4.0-4.5\ub710-5 K-1], these minerals show a different anisotropic pattern, more pronounced in cancrinite and vishnevite. This behavior is governed by different deformation mechanisms, which reflect the different coordination environments of the cage population between the minerals of the two subgroups. In vishnevite, a P-induced re-organization of the channel population took place at P >= 3.5 GPa, suggesting that also the channel-constituents (and not only the cage one) can play an active role on the structure response at non-ambient conditions. In addition, the high-T behavior of cancrinite was studied up to 823 K, by in situ single-crystal X-ray diffraction. At 748 K, a slow dehydration process takes place towards a (quasi)-anhydrous structure. These are the first experimental findings aimed to provide a comparative thermo-elastic analysis of the CAN-group compounds, expanding the knowledge about the P/T-behavior of isotypic materials with open-framework structures

Cation distribution and valence in synthetic Al-Mn-O and Fe-Mn-O spinels under varying fO2 conditions

The spinel-group minerals, found in a range of igneous rocks, are resistant toweathering and can incorporate several multivalent elements, meaning they have the potential to provide insight into the redox conditions of parental magmas. Naturally occurring spinel can contain varying quantities of Mn, an element which occurs terrestrially and extra-terrestrially as Mn2+, Mn3+, Mn4+ and Mn5+. However, a lack of information on the effects of oxygen fugacity (fO2 ) on: (1) Mn valence state and cation distribution; and (2) on spinel-melt partitioning means that the potential for a Mn-in-spinel oxy-barometer remains largely untested. Here, we use electron probe microanalysis, micro-focus X-ray Absorption Near Edge Structure (XANES) spectroscopy and single-crystal X-ray diffraction (SC-XRD) to investigate cation distribution and valence state in spinels in the Al-Mn-O and Fe-Mn-O systems synthesized at ambient pressure under varying fO2 conditions. In contrast to previous studies, we find that the spectral resolution of the Mn K-edge XANES spectra is insufficient to provide quantitative data onMn valence state and site occupancy, although it does verify that Mn is incorporated as both Mn2+ and Mn3+, distributed over tetrahedral and octahedral sites. Combination of data from XANES and SC-XRD refinements can, however, be used to model Mn, Al and Fe valence and site occupancy. It would be expected thatMn-Fe spinels have the potential to record fO2 conditions in parental melts due to changes to the octahedral site under conditions that were more reducing. However, decoupling the effects of temperature and oxygen fugacity on the TFe3+-TMn2+ exchange in the Mn-Fe spinels remains challenging. In contrast, little variation is noted in Mn-Al spinels as a function of fO2 , implying that crystal chemistry and cation site geometry may significantly influence cation distribution, and by inference, crystal-melt partitioning, in spinel-group minerals

Cytotoxic effects of Gemcitabine-loaded liposomes in human anaplastic thyroid carcinoma cells

BACKGROUND: Identification of effective systemic antineoplastic drugs against anaplastic thyroid carcinomas has particularly important implications. In fact, the efficacy of the chemotherapeutic agents presently used in these tumours, is strongly limited by their low therapeutic index. METHODS: In this study gemcitabine was entrapped within a pegylated liposomal delivery system to improve the drug antitumoral activity, thus exploiting the possibility to reduce doses to be administered in cancer therapy. The cytotoxic effects of free or liposome-entrapped gemcitabine was evaluated against a human thyroid tumour cell line. ARO cells, derived from a thyroid anaplastic carcinoma, were exposed to different concentrations of the drug. Liposomes formulations were made up of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine/cholesterol/1,2-distearoyl-sn-glycero-3-phosphoethanolamine-MPEG (8:3:1 molar ratio). Cell viability was assessed by both trypan bleu dye exclusion assay and fluorimetric analysis of cell DNA content. RESULTS: A cytotoxic effect of free gemcitabine was present only after 72 h incubation (ARO cell mortality increased of approximately 4 fold over control at 1 μM, 7 fold at 100 μM). When gemcitabine was encapsulated in liposomes, a significant effect was observed by using lower concentrations of the drug (increased cell mortality of 2.4 fold vs. control at 0.3 μM) and earlier exposure time (24 h). CONCLUSION: These findings show that, in vitro against human thyroid cancer cells, the gemcitabine incorporation within liposomes enhances the drug cytotoxic effect with respect to free gemcitabine, thus suggesting a more effective drug uptake inside the cells. This may allow the use of new formulations with lower dosages (side effect free) for the treatment of anaplastic human thyroid tumours

Effector and central memory T helper 2 cells respond differently to peptide immunotherapy

Peptide immunotherapy (PIT) offers realistic prospects for the treatment of allergic diseases, including allergic asthma. Much is understood of the behavior of naive T cells in response to PIT. However, treatment of patients with ongoing allergic disease requires detailed understanding of the responses of allergen-experienced T cells. CD62L expression by allergen-experienced T cells corresponds to effector/effector memory (CD62L(lo)) and central memory (CD62L(hi)) subsets, which vary with allergen exposure (e.g., during, or out with, pollen season). The efficacy of PIT on different T helper 2 (Th2) cell memory populations is unknown. We developed a murine model of PIT in allergic airway inflammation (AAI) driven by adoptively transferred, traceable ovalbumin-experienced Th2 cells. PIT effectively suppressed AAI driven by unfractionated Th2 cells. Selective transfer of CD62L(hi) and CD62L(lo) Th2 cells revealed that these two populations behaved differently from one another and from previously characterized (early deletional) responses of naive CD4(+) T cells to PIT. Most notably, allergen-reactive CD62L(lo) Th2 cells were long-lived within the lung after PIT, before allergen challenge, in contrast to CD62L(hi) Th2 cells. Despite this, PIT was most potent against CD62L(lo) Th2 cells in protecting from AAI, impairing their ability to produce Th2 cytokines, whereas this capacity was heightened in PIT-treated CD62L(hi) Th2 cells. We conclude that Th2 cells do not undergo an early deletional form of tolerance after PIT. Moreover, memory Th2 subsets respond differently to PIT. These findings have implications for the clinical translation of PIT in different allergic scenarios

Exploitation of the HIV-1 coat glycoprotein, gp120, in neurodegenerative studies in vivo

Neuronal loss has often been described at post-mortem in the brain neocortex of patients suffering from AIDS. Neuroinvasive strains of HIV infect macrophages, microglial cells and multinucleated giant cells, but not neurones. Processing of the virus by cells of the myelomonocytic lineage yields viral products that, in conjunction with potentially neurotoxic molecules generated by the host, might initiate a complex network of events which lead neurones to death. In particular, the HIV-1 coat glycoprotein, gp120, has been proposed as a likely aetiologic agent of the described neuronal loss because it causes death of neurones in culture. More recently, it has been shown that brain neocortical cell death is caused in rat by intracerebroventricular injection of a recombinant gp120 coat protein, and that this occurs via apoptosis. The latter observation broadens our knowledge in the pathophysiology of the reported neuronal cell loss and opens a new lane of experimental research for the development of novel therapeutic strategies to limit damage to the brain of patients suffering from HIV-associated dementia