Glutathione (γ-glutamyl-cysteinyl-glycine, GSH) is a major thiol-containing peptide with cellular levels of up to 10 mM.1 Several recent reports have demonstrated glutaredoxins (Grx) to form [Fe2S2] cluster-bridged dimers, where glutathione provides two exogenous thiol ligands, and have implicated such species in cellular iron sulfur cluster biosynthesis. We report the finding that glutathione alone can coordinate and stabilize an [Fe2S2] cluster under physiological conditions, with optical, redox, Mössbauer and NMR characteristics that are consistent with a [Fe2S2](GS)4 composition. The Fe-S assembly protein ISU catalyzes formation of [Fe2S2](GS)4 from iron and sulfide ions in the presence of glutathione, and the [Fe2S2] core undergoes reversible exchange between apo ISU and free glutathione.
Assembly and stabilization of a glutathione-complexed [2Fe-2S] cluster is promoted by aggregation of glutathione. The cluster core selects the tetramer species from a collection of equilibrating solution aggregate species, and in turn the core is stabilized toward hydrolytic degradation. Studies of glutathione derivatives, in combination with mass spectrometric and Mössbauer investigations provide insight on reaction intermediates during formation of [2Fe-2S](GS)42-.
trans-Sialidase and cruzipain are important virulence factors from Trypanosoma cruzi, the etiological agent of Chagas disease,
that have highly antigenic domains in their structure and were reported
as potential tools for diagnosis of the illness. The aim of the present
study is to assess the possibility of using cruzipain and the catalytic
domain of trans-sialidase in a Surface Plasmon Resonance-based
immunosensor for the diagnosis of chronic Chagas disease. Immunoassays
carried out with canine sera verified that cruzipain allows the detection
of anti-Trypanosoma cruzi antibodies whereas recombinant trans-sialidase did not yield specific detections, due to
the high dilutions of serum used in the immunoassays that hinder the
possibility to sense the specific low titer antibodies. The developed
cruzipain-based biosensor, whose price per assay is comparable to
a commercial enzyme-linked immunosorbent assay (ELISA), was successfully
applied for the rapid quantification of specific antibodies against Trypanosoma cruzi in fresh human sera showing an excellent
agreement with ELISA.
The short range technique of the Perturbed Angular Correlation (PAC) and x-ray diffraction (Rietveld) methods have been employed to determine the phase content in commercial mullite-zirconia and zircon raw materials that are ordinarily used to produce ceramic materials. The PAC technique, which probes zirconiumcontaining compounds at nanoscopic level, showed that zircon contains crystalline ZrSiO 4 and an important amount of a structurally distorted zircon, which is also observed accompanying monoclinic zirconia in mullite-zirconia. This particular zircon phase was not detected by the long range x-ray diffraction-Rietveld technique. After an annealing treatment, important changes in crystalline contents of the powders allow confirming, by the x-ray diffraction-Rietveld method, the preexistence of this particular zircon phase. This fact must be taken into account when preparing multicomposites based on the present raw materials.
The applications of pharmaceutical and medical nanosystems are among the most intensively investigated fields in nanotechnology. A relevant point to be considered in the design and development of nanovehicles intended for medical use is the formation of the "protein corona" around the nanoparticle, that is, a complex biomolecular layer formed when the nanovehicle is exposed to biological fluids. The chemical nature of the protein corona determines the biological identity of the nanoparticle and influences, among others, the recognition of the nanocarrier by the mononuclear phagocytic system and, thus, its clearance from the blood. Recent works suggest that Surface Plasmon Resonance (SPR), extensively employed for the analysis of biomolecular interactions, can shed light on the formation of the protein corona and its interaction with the surroundings. The synthesis and characterization of solid lipid nanoparticles (SLN) coated with polymers of different chemical nature (e.g., polyvinyl alcohol, chitosans) are reported. The proof-of-concept for the use of SPR technique in characterizing protein-nanoparticle interactions of surface-immobilized proteins (immunoglobulin G and bovine serum albumin, both involved in the formation of the corona) subjected to flowing SLN is demonstrated for non-chitosan-coated nanoparticles. All assayed nanosystems show more preference for IgG than for BSA, such preference being more pronounced in the case of polyvinyl-alcohol-coated SLN.
The development of drug carriers based in lipid nanoparticles (LNPs) aims toward the synthesis of non-toxic multifunctional nanovehicles that can bypass the immune system and allow specific site targeting, controlled release and complete degradation of the carrier components. Among label free techniques, Surface Plasmon Resonance (SPR) biosensing is a versatile tool to study LNPs in the field of nanotherapeutics research. SPR, widely used for the analysis of molecular interactions, is based on the immobilization of one of the interacting partners to the sensor surface, which can be easily achieved in the case of LNPs by hydrophobic attachment onto commercial lipid- capture sensor chips. In the last years SPR technology has emerged as an interesting strategy for studying molecular aspects of drug delivery that determines the efficacy of the nanotherapeutical such as LNPs' interactions with biological targets, with serum proteins and with tumor extracelullar matrix. Moreover, SPR has contributed to the obtention and characterization of LNPs, gathering information about the interplay between components of the formulations, their response to organic molecules and, more recently, the quantification and molecular characterization of exosomes. By the combination of available sensor platforms, assay quickness and straight forward platform adaptation for new carrier systems, SPR is becoming a high throughput technique for LNPs' characterization and analysis.
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