320 research outputs found
Porous Supramolecular Architectures: Ultra-fast Molecular Rotors and Dynamics Control by Chemical Stimuli
No full textA challenging issue is the dynamics of nanoporous solids after the insertion of molecular rotors in their building blocks and promises access to the control of rotary motion by chemical and physical stimuli.[1] The combination of porosity with ultra-fast rotor dynamics was discovered in molecular crystals, covalent organic frameworks and MOFs by 2H spin-echo NMR spectroscopy and T1 relaxation times.[2-5] The rotors, as fast as 1011 Hz at 150 K, are exposed to the crystalline channels, which absorb CO2 and I2 from the gas phase, even at low pressures. Interestingly, the rotor dynamics can be switched on and off by vapor absorption/desorption, showing a remarkable change of material dynamics, which, in turn, produces a modulated physical response. Novel mesoporous organosiloxane frameworks allowed us to realize periodic architectures of fast molecular rotors on which C-F dipoles are mounted.[6] These dipolar rotors showed not only rapid dynamics (109 Hz at 325 K) in solid-state NMR experiments, but also a dielectric response typical of a fast dipole reorientation. Moreover, crystals with permanent porosity were exploited in an unusual way to decorate crystal surfaces with regular arrays of dipolar rotors. The inserted molecules carry alkyl chains which are included as guests into the channel-ends.[7] The rotors stay at the surface due to a bulky molecular stopper which prevents the rotors from entering the channels. In a final example, flexible molecular crystals were fabricated by a series of shape-persistent azobenzene tetramers that form porous molecular crystals in their trans configuration. The efficient trans→cis photoisomerization of the azobenzene units converts the crystals into a non-porous phase but crystallinity and porosity are restored upon Z→E isomerization promoted by visible light irradiation or heating. We demonstrated that the photoisomerization enables reversible on/off switching of optical properties as well as the capture of CO2 from the gas phase.[8]
We would like to thank Cariplo Foundation/Lombardy Region/INSTM Consortium.
References
1. A. Comotti, S. Bracco, P. Sozzani Acc. Chem. Res. 2016, 49, 1701.
2. S. Bracco, et al Chem. Eur. J. 2017, 23, 11210.
3. A. Comotti, et al J. Am. Chem. Soc. 2014, 136, 618.
4. A. Comotti, et al Angew. Chem. Int. Ed. 2014, 53, 1043.
5. S. Bracco, et al Chem. Comm. 2017, 53, 7776.
6. S. Bracco, et al Angew. Chem. Int Ed. 2015, 54, 4773.
7. L. Kobr, et al J. Am. Chem. Soc. 2012, 134, 10122.
8. M. Baroncini et al. Nature Chem. 2015, 7, 634
Immunobiology of essential mixed cryoglobulinemia
No full textIntroduction
Mixed cryoglobulinemia (MC) is characterized by the production of monoclonal (type II MC) or polyclonal (type III MC) rheumatoid factors (RF), which form with endogenous IgG cold-precipitable immune complexes that cause small-vessel vasculitis and multi-organ damage. Hepatits C virus is the causative agent in 90% of MC patients, usually characterized by the expansion of an anergic B cell subpopulation called CD21low B cells. Only a minority of the patients has idiopathic or essential MC (EMC) and the B cell population has been scarcely investigated so far.
Objective: to characterize the phenotypical and functional proprieties of B cells in EMC and compare them with those of HCV-related MC and from healthy donors.
Method
The B cell phenotype and function was studied in 13 patients with EMC and compared to 24 patients with HCV-MC. The proliferative response of B cells was investigated through the CFSE assay, the intracellular pERK content was measured by the BD Phos-Flow system and apoptosis was measured through annexin/7AAD staining. All the analyses were performed by flow-cytometry.
Results
EMC patient showed significant lower absolute numbers of circulating B cells compared to HCV-MC (mean ± SD: 185/mm3 ± 236 vs 529/mm3 ± 795). Interestingly percentages and absolute numbers of CD21low B cells were significantly higher in EMC compare to HD but lower than HCV-MC patients. Similarly to CD21low B cells found in HCV MC, CD21low B cells in EMC proliferated poorly in response to TLR9 stimulation, displayed dysregulated pERK signaling and were apoptosis prone.
Conclusion
Similar features of virus-specific exhaustion and anergy induced by continual antigenic stimulation observed in B cells expanded in HCV-MC are found in B cells EMC. Our findings open the question of a possible role of a still yet unknown antigen responsible for the development of EMC
Modulation of granulocyte survival and programmed cell death by cytokines and bacterial products
No full text
Impact of anti-CD20 tumor-targeting therapeutic monoclonal antibodies on human Natural Killer cell responsiveness and plasticity: relevance of FcgammaRIIIA/CD16 affinity ligation conditions
No full textMy study is focused on understanding the mechanisms underlying the modulation of NK cell responsiveness and plasticity induced by tumor targeting therapeutic anti-CD20 monoclonal antibodies (mAbs) nowadays routinely used in the treatment of B-cell malignancies and autoimmune disorders. Anti-CD20 mAbs are grouped into type I and II subtypes. Type I mAbs induce CD20 redistribution into lipid rafts and display a remarkable ability to activate complement-dependent cytotoxicity (CDC). On the other hand, type II mAbs, which are not able to localize CD20 complexes into lipid rafts and induce weak or no CDC, evoke more homotypic adhesion and direct killing of target cells. Both type I and II mAbs demonstrate efficient phagocytosis and antibody-dependent cytotoxicity (ADCC). Natural Killer (NK) cell-mediated ADCC, based on the recognition of IgG-opsonized targets by the low affinity Fc receptor for IgG FcgammaRIIIA/CD16, represents one of the main mechanisms by which anti-CD20 mAbs mediate their anti-tumor effects. Besides ADCC, CD16 ligation also results in the production of cytokines such as IFN-gamma that plays a key role in the shaping of adaptive immune responses. Rituximab is a chimeric type I anti-CD20 mAb of 1st generation and is considered the reference molecule for the comparison with new generation anti-CD20 mAbs, designed to optimize clinical efficacy. Among them, obinutuzumab is a humanized Fc-glycoengineered type II anti-CD20 mAb of 3rd generation designed to increase the affinity for CD16 receptor and consequently the killing of mAb-opsonized targets. However, the impact of CD16 ligation in optimized affinity conditions on NK functional program is not completely understood. Herein, I demonstrated that CD16 affinity ligation conditions may dictate both the amplitude of NK responsiveness (cytotoxicity and IFN-gamma production) as well as the ability to shift the NK functional program. Indeed, I observed that the interaction of NK cells with obinutuzumab-opsonized targets results in enhanced cytotoxicity and IFN-gamma production as compared with the parental non-glycoengineered mAb or the reference molecule rituximab, independently from the CD16-158V/F allotype. The affinity ligation conditions also strictly correlate with the ability to induce CD16 surface down-modulation and lysosomal targeting of receptor-coupled signaling elements. Indeed, a preferential degradation of FcepsilonRIgamma chain and Syk tyrosine kinase was observed upon obinutuzumab stimulation independently from the CD16-158V/F allotype. Notably, although the down-regulation of FcepsilonRIgamma/Syk module hesitates in the impairment of cytotoxic function induced by CD16, NKp46 and NKp30 activating receptors, obinutuzumab-experienced NK cells exhibit an increased ability to produce IFN-gamma in response to cytokines and target stimulation as well as to obinutuzumab-mediated CD16 re-stimulation.
Relying on the observation that obinutuzumab-experienced NK cells, under molecular and functional profile, resemble the distinctive features of the long-lived and highly functional “memory” NK cells, a population recently identified in HCMV seropositive individuals, I assessed the capability of anti-CD20 mAbs to affect the expansion as well as the phenotypic and functional properties of the “memory” NK subset. My data show that the majority of the analysed healthy donors is HCMV seropositive and exhibits a detectable population of “memory” NK cells (CD3- CD56+ FcepsilonRIgamma- CD16+) accounting for 3 to 50% of peripheral blood NK cells. I observed that “memory” NK cells selectively undergo 2- to 12-fold expansion upon co-culturing with anti-CD20-opsonized targets; on the opposite, the proliferation of “conventional” NK cells (CD3- CD56+ FcepsilonRIgamma+ CD16+) is not affected by CD16 stimulation. I also noted that anti-CD20 mAb in vitro expanded “memory” NK cells show the molecular and functional hallmarks of their freshly isolated counterpart, including the increased expression of NKG2C receptor, the reduced expression of NKp46 receptor associated to an enhanced functional activity in response to CD16 re-stimulation, particularly in terms of IFN-gamma production
Fluorinated porous organic frameworks for improved CO2 and CH4 capture
No full textA porous 3D selectively fluorinated framework (F-PAF1), robust yet flexible and with a surface area of 2050 m(2) g(-1), was synthesised by condensation of an ad hoc prepared fluorinated tetraphenylmethane (TPM) monomer to ensure homogenously distributed C-F dipoles in the swellable architecture. Tetradentate TPM was also the comonomer for the reaction with fluorinated difunctional monomers to obtain frameworks (FMFs) with a controlled amount of regularly spaced reorientable C-F dipoles. The isosteric heat of adsorption of CO2 was increased by 53% by even moderate C-F dipole insertion, with respect to the non-fluorinated frameworks. CO2/N-2 selectivity was also increased up to a value of 50 for the difluoro-containing comonomer. Moreover, methane shows optimal interaction energies of 24 kJ mol(-1)
Dynamics and Flexibility in Gas-absorptive Porous Materials
No full textThe enormous interest manifested in recent years for porous materials has generated efficient systems for adsorbing gases of great interest for energy and the environment, such as CO2, CH4 and H2. Our approach was to design porosity in combination with switchable dynamics and flexibility for gaining control over gas capture and selectivity. This approach was made possible by fabricating rotor-on-axel molecular struts and tetrahedral building blocks.
Rotor-on-axel molecular struts. Ultra-fast molecular rotors were realized in porous solids by engineering crystalline frameworks (molecular crystals, MOFs and mesoporous organosilicas) containing rod-like linkers as amphidynamic elements.1-5 The porous frameworks promise access to the control of rotary motion by chemical and physical stimuli. We prepared rotors as fast as 1011 Hz (in the regime of conventional liquids) in properly designed porous crystals. Rotor dynamics was successfully hampered by the diffusion of gases or vapors. In turn, the on/off switching of dynamics produces modulated physical responses when C-F dipoles were mounted on the rotors.6 Direct evidence of host-guest relationships and interactions at the molecular level were established by 2D solid-state NMR and modelled by ab initio calculations.
Tetrahedral building-blocks. In the search for flexible molecular crystals endowed with porosity, we achieved the fabrication of expandable crystalline prototypal structures, which allow for the absorption of gases, without modifying the crystal architecture.7 The design brings together highly symmetrical tetrahedral elements to construct swellable porous adamantoid frameworks. The flexibility of the porous crystals manifests itself in response to stimuli of selected gases: the contact with CO2, Xe and hexane triggers the enlargement of channel cross-section and capacity. The accomodation of CO2 and Xe in the channel chambers was revealed by synchrotron-light XRD, combined with Molecular Dynamics and DFT calculations. Xenon dynamics, exploring various cavity orientations in the crystal, were gathered by 129Xe NMR chemical shift anisotropy profiles, which encode the shape and orientation of each visited cavity. Jump rate and activation energy experienced by exploring Xe atoms were uniquely established.
Moreover, photo-responsive molecular crystals were fabricated by a series of tetrahedral azobenzene tetramers that form porous molecular crystals in their trans configuration.8 The efficient trans-to-cis photoisomerization of the azobenzene units converts the crystals into a non-porous phase but crystallinity and porosity are restored upon cis-to-trans reverse isomerization promoted by visible light or heat. We demonstrated that the photo-isomerization enables reversible on/off switching of optical properties as well as CO2 capture from the gas phase. Acknowldegements to PRIN 2016 2016-NAZ-0104
(1) A. Comotti, A. et al. Acc. Chem. Res. 49 (2016) 1701-1710.
(2) S. Bracco, et al. Chem. Eur. J. 23 (2017) 11210.
(3) A. Comotti, et al. J. Am. Chem. Soc. 136 (2014) 618.
(4) A. Comotti, et al. Angew. Chem. Int. Ed. 53 (2014) 1043.
(5) S. Bracco, et al. Chem. Comm. 53 (2017) 7776.
(6) S. Bracco, et al. Angew. Chem. Int Ed. 54 (2015) 4773.
(7) I. Bassanetti, et al. J. Mater. Chem. A 6 (2018) 14231.
(8) M. Baroncini, et al. Nature Chem. 7 (2015) 634
Urethane-induced lung carcinogenesis
No full textChemical induced carcinogenesis together with genetically engineered mouse models represent important approaches for the study of the complex mechanisms involving genotype and environmental factors in cancer development, including lung cancer. The induction of lung tumor in mice with urethane (ethyl carbamate) is considered a valuable model of Kras-driven lung cancer. However, inbred mouse strains show variable susceptibility to lung tumor formation, with C57BL/6 background, widely used to study many transgenic and null mutations, highly resistant to lung carcinogenesis. Here is described a protocol of urethane-induced lung cancer effective in lung tumor induction in C57BL/6J strain. Multiple urethane injections are needed to overcome genetic resistance and induce in a reproducible manner lung carcinogenesis in C57BL/6J background mice
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