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In recent years, perovskite nanocrystal superlattices have been reported with collective optical phenomena, offering a promising platform for both fundamental science studies and device engineering. In this same avenue, superlattices of perovskite nanoplates can be easily prepared on different substrates, and they too present ensemble optical response. However, the self-assembly and optical properties of these aggregates in solvents have not been reported to date. Here, we report on the condition for this self-assembly to occur and show a simple strategy to induce the formation of these nanoplates stacks in suspension in different organic solvents. We combined wide- and small-angle X-ray scattering and scanning transmission electron microscopy to evaluate CsPbBr3 and CsPbI3 perovskite nanoplates with different thickness distributions. We observed the formation of these stacks by changing the concentration of nanoplates and the viscosity of the colloidal suspensions, without the need of antisolvent addition. We found that, in hexane, the concentration threshold for the formation of the stacks is rather high and approximately 80 mg/mL. In contrast, in decane, dodecane, and hexadecane, we observe a much easier self-assembly of the nanoplates, presenting a clear correlation between the degree of aggregation and viscosity. We, then, discuss the impact of the self-assembly of perovskite nanoplates on Förster resonant energy transfer. Our predictions suggest an energy transfer efficiency higher than 50%, even in a low photoluminescence quantum yield scenario, for both perovskite compositions.

Na(+)/Ca(2+) exchangers (NCXs) are secondary active transporters that couple the translocation of Na(+) with the transport of Ca(2+) in the opposite direction. The exchanger is an essential Ca(2+) extrusion mechanism in excitable cells. It consists of a transmembrane domain and a large intracellular loop that contains two Ca(2+)-binding domains, CBD1 and CBD2. The two CBDs are adjacent to each other and form a two-domain Ca(2+) sensor called CBD12. Binding of intracellular Ca(2+) to CBD12 activates the NCX but inhibits the NCX of Drosophila, CALX. NMR spectroscopy and SAXS studies showed that CALX and NCX CBD12 constructs display significant interdomain flexibility in the apo state but assume rigid interdomain arrangements in the Ca(2+)-bound state. However, detailed structure information on CBD12 in the apo state is missing. Structural characterization of proteins formed by two or more domains connected by flexible linkers is notoriously challenging and requires the combination of orthogonal information from multiple sources. As an attempt to characterize the conformational ensemble of CALX-CBD12 in the apo state, we applied molecular dynamics (MD) simulations, NMR ((1)H-(15)N residual dipolar couplings), and small-angle x-ray scattering (SAXS) data in a combined strategy to select an ensemble of conformations in agreement with the experimental data. This joint approach demonstrated that CALX-CBD12 preferentially samples closed conformations, whereas the wide-open interdomain arrangement characteristic of the Ca(2+)-bound state is less frequently sampled. These results are consistent with the view that Ca(2+) binding shifts the CBD12 conformational ensemble toward extended conformers, which could be a key step in the NCXs’ allosteric regulation mechanism. This strategy, combining MD with NMR and SAXS, provides a powerful approach to select ensembles of conformations that could be applied to other flexible multidomain systems.

Hair analysis plays an important role in forensic toxicology and biomonitoring tests. However, cosmetic treatments cause changes to the hair. Thus, a better understanding of the hair’s structure and the factors that influence its composition is critical. It is known that oxidative treatments modify the hair chemical, structural and mechanical properties. These treatments also cause degradation of the melanin as well as of the structures present in the hair cuticle and cortex. Considering that the literature is unanimous regarding the increase in hydrophilicity and porosity promoted in human hair by bleaching, in this work we investigated how this oxidative damage is triggered. By combining several techniques, inelastic and quasi-elastic neutron scattering, differential scanning calorimetry, thermal gravimetric analysis and X-ray diffraction, we were able to connect the chemical and structural changes to a subtle dynamic modification of the proton mobility in the hair fibers. In addition, alterations in the thermal behavior evidenced a small denaturation of α-keratin intermediate filaments and a slight decrease in the amount of confined water in the hair fibers. Moreover, data obtained by neutron spectroscopy indicated that bleaching attacks the thioester groups of the proteins causing larger proton mobility of the hydrogenous components (water, protein and/or lipids).

Made available in DSpace on 2021-06-25T10:12:08Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-12-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) The activation process of phospholipase A2-like (PLA2-like) toxins is a key step in their molecular mechanism, which involves oligomeric changes leading to the exposure of specific sites. Few studies have focused on the characterization of allosteric activators and the features that distinguish them from inhibitors. Herein, a comprehensive study with the BthTX-I toxin from Bothrops jararacussu venom bound or unbound to α-tocopherol (αT) was carried out. The oligomerization state of BthTX-I bound or unbound to αT in solution was studied and indicated that the toxin is predominantly monomeric but tends to oligomerize when complexed with αT. In silico molecular simulations showed the toxin presents higher conformational changes in the absence of αT,which suggests that it is important to stabilize the structure of the toxin. The transition between the two states (active/inactive) was also studied, showing that only the unbound BthTX-I system could migrate to the inactive state. In contrast, the presence of αT induces the toxin to leave the inactive state, guiding it towards the active state, with more regions exposed to the solvent, particularly its active site. Finally, the structural determinants necessary for a molecule to be an inhibitor or activator were analyzed in light of the obtained results. Departamento de Biofísica e Farmacologia Instituto de Biociências Universidade Estadual Paulista (UNESP) Laboratoire de Biologie et de Pharmacologie Appliquée École Normale Supérieure Paris Saclay UMR 8113 CNRS, 4 Avenue des Sciences Departamento de Física Experimental Instituto de Física Universidade de São Paulo (USP) Departamento de Biotecnologia e Bioprocessos Faculdade de Ciências Agronômicas Universidade Estadual Paulista (UNESP) Instituto de Biotecnologia Universidade Estadual Paulista (UNESP) Departamento de Biofísica e Farmacologia Instituto de Biociências Universidade Estadual Paulista (UNESP) Departamento de Biotecnologia e Bioprocessos Faculdade de Ciências Agronômicas Universidade Estadual Paulista (UNESP) Instituto de Biotecnologia Universidade Estadual Paulista (UNESP) CNPq: 302883/2017-7 CNPq: 401190/2017-0 CAPES: 88881.134154/2016-01 CAPES: 88882.183567/2007-01

The Na+/Ca2+ exchanger of Drosophila melanogaster, CALX, is the main Ca2+-extrusion mechanism in olfactory sensory neurons and photoreceptor cells. Na+/Ca2+ exchangers have two Ca2+ sensor domains, CBD1 and CBD2. In contrast to the mammalian homologs, CALX is inhibited by Ca2+ binding to CALX-CBD1, whereas CALX-CBD2 does not bind Ca2+ at physiological concentrations. CALX-CBD1 consists of a β-sandwich and displays four Ca2+-binding sites at the tip of the domain. In this study, we used NMR spectroscopy and isothermal titration calorimetry (ITC) to investigate the cooperativity of Ca2+ binding to CALX-CBD1. We observed that this domain binds Ca2+ in the slow exchange regime at the NMR chemical shift timescale. Ca2+ binding restricts the dynamics in the Ca2+-binding region. Experiments of 15N chemical exchange saturation transfer and 15N R2 dispersion allowed the determination of Ca2+ dissociation rates (∼30 s-1). NMR titration curves of residues in the Ca2+-binding region were sigmoidal because of the contribution of chemical exchange to transverse magnetization relaxation rates, R2. Hence, a novel, to our knowledge, approach to analyze NMR titration curves was proposed. Ca2+-binding cooperativity was examined assuming two different stoichiometric binding models and using a Bayesian approach for data analysis. Fittings of NMR and ITC binding curves to the Hill model yielded nHill ∼2.9, near maximal cooperativity (nHill = 4). By assuming a stepwise model to interpret the ITC data, we found that the probability of binding from 2 up to 4 Ca2+ is approximately three orders of magnitude higher than that of binding a single Ca2+. Hence, four Ca2+ ions bind almost simultaneously to CALX-CBD1. Cooperative Ca2+ binding is key to enable this exchanger to efficiently respond to changes in the intracellular Ca2+ concentration in sensory neuronal cells.

The aim of this study was to investigate the effects of 6-months consumption of green-banana biomass on the LDL particle functionality in subjects with type 2 diabetes. Subjects (n = 39, mean age 65 years old) of both sexes with diabetes (HbA1c ≥ 6·5%) were randomized to receive nutritional support plus green-banana biomass (40 g) (n = 21) or diet alone (n = 18) for 6-months. Non-linear optical responses of LDL solutions from these participants were studied by Z-scan technique. UV–visible spectrophotometer was used to measure the absorbance of the LDL samples. Small Angle X-ray Scattering and Dynamic Light Scattering experiments were used to look for any structural changes in LDL samples and to determine their size distribution. The Lipoprint test was used to determine the LDL sub-fractions in terms of distribution and size. Consumption of green-banana biomass, reduced total- (p = 0.010), non-HDL-cholesterol (p = 0.043), glucose (p = 0.028) and HbA1c (p = 0.0007), and also improved the protection of the LDL particle against oxidation, by the increase in carotenoids content in the particles (p = 0.007). This higher protection against modifications may decrease the risk of developing cardiovascular disease. These benefits of the green-banana biomass encourage the use of resistant starches with potential clinical applications in individuals with pre-diabetes and diabetes.

Magnetic nanoparticles based on manganese–zinc ferrite presenting spherical and cubic shapes, verified by small-angle X-rays scattering, were studied by means of the hyper-Rayleigh scattering, the Z-Scan technique in the open-aperture configuration, and a spectrally resolved femtosecond transient absorption setup. Hyper-Rayleigh scattering and Z-Scan experiments were performed with applied magnetic field parallel to the laser polarization state and in the perpendicular direction. The hyperpolarizability of spherical nanoparticles was greater than the cubic ones due to the higher volume of spherical nanoparticles and, therefore, the increased influence of the spin-disoriented layer at the surface on cubic nanoparticles, resulting in a smaller orientational average contribution to the hyperpolarizability. The two-photon absorption cross section was the same for both samples, since the basic constituents are the same and the light absorption is not influenced by the surface anisotropy present on magnetic nanoparticles. For both nanoparticles, the measured optical second harmonic and the nonlinear absorption increased during experiments performed in the presence of external field in the parallel configuration, while a decrease was verified for experiments in the perpendicular case, which demonstrates a crystalline anisotropy on the nonlinear optical properties. Transient absorption measurements revealed an ultrafast relaxation process containing at least two separated dynamical processes, the faster with characteristic time below 1 ps and a longer one, much higher than 100 ps.

We present a study on the formation of silver (Ag) and bimetallic silver-gold (AgAu) nanoparticles monitored by in situ SAXS as well as by ex situ TEM, XRD and UV-vis analysis in a flow reactor at controlled reaction temperature. The formation mechanism of the nanoparticles is derived from the structural parameters obtained from the experimental data. The evolution of the average particle size of pure and alloyed nanoparticles shows that the particle growth occurs initially by a coalescence mechanism. The later growth of pure silver nanoparticles is well described by Ostwald ripening and for the alloyed nanoparticles by a process with a significantly slower growth rate. Additionally, the SAXS data of pure silver nanoparticles revealed two major populations of nanoparticles, the first one with a continuous crystal growth to a saturation plateau, and the second one probably with a continuous emergence of small new crystals. The particle sizes obtained by SAXS agree well with the results from transmission electron microscopy and X-ray diffraction. The present study demonstrates the capability of an in situ investigation of synthesis processes using a laboratory based SAXS instrument. Online monitoring of the synthesis permitted a detailed investigation of the structural evolution of the system. CA - Epple

The study of supramolecular structures in biological systems aiming at the investigation of mechanisms of interaction, detection, kinetics, among others, is of great relevance. Due to the nanometric dimensions of such structures, scattering techniques are widely used for their characterization, in addition to allowing great versatility with regard to the physical state of the sample to be analyzed, which includes liquids, gels, gases, and solids. In this chapter, we will present an overview of DLS, SAXS, SANS, and SLS scattering techniques, as well as a brief explanation on what structural parameters could be obtained from each of them. In the following, we present application examples involving different classes of biomolecules such as proteins, DNAs, lipids, and polymers, where the SAXS technique was used as the main tool for their structural characterization.

Photodynamic therapy (PDT) is a potential non-invasive approach for application in oncological diseases, based on the activation of a photosensitizer (PS) by light at a specific wavelength in the presence of molecular oxygen to produce reactive oxygen species (ROS) that trigger the death tumor cells. In this context, porphyrins are interesting PS because they are robust, have high chemical, photo, thermal, and oxidative stability, and can generate singlet oxygen (1O2). However, porphyrins exhibit low solubility and a strong tendency to aggregate in a biological environment which limits their clinical application. To overcome these challenges, we developed hybrid nanostructures to immobilize 5,10,15,20-tetrakis[(4-carboxyphenyl) thio-2,3,5,6-tetrafluorophenyl] (P), a new third-generation PS. The biological effect of this system was evaluated against bladder cancer (BC) cells with or without light exposition. The nanostructure composed of lipid carriers coated by porphyrin-chitosan (P-HNP), presented a size of ca. 130 nm and low polydispersity (ca. 0.25). The presence of the porphyrin-chitosan (P-chitosan) on lipid nanoparticle surfaces increased the nanoparticle size, changed the zeta potential to positive, decreased the recrystallization index, and increased the thermal stability of nanoparticles. Furthermore, P-chitosan incorporation on nanoparticles increased the stability and enhanced the self-organization of the system and the formation of spherical structures, as observed by small-angle X-ray scattering (SAXS) analysis. Furthermore, the immobilization process maintained the P photoactivity and improved the photophysical properties of PS, minimizing its aggregation in the cell culture medium. In the photoinduction assays, the P-HNP displayed high phototoxicity with IC50 3.2-folds lower than free porphyrin. This higher cytotoxic effect can be correlated to the high cellular uptake of porphyrin immobilized, as observed by confocal images. Moreover, the coated nanoparticles showed mucoadhesive properties interesting to its application in vivo. Therefore, the physical and chemical properties of nanoparticles may be relevant to improve the porphyrin photodynamic activity in BC cells.

Hepatitis B virus causes acute and chronic infections in millions of people worldwide and, since 1982, a vaccine with 95% effectiveness has been available for immunization. The main component of the recombinant hepatitis B vaccine is the surface antigen protein (HBsAg). In this work, the effect of pH, ionic strength and temperature on the native state of the HBsAg antigen were studied by a combination of biophysical methods that included small angle X-ray scattering, synchrotron radiation circular dichroism, fluorescence and surface plasmon resonance spectroscopies, as well as in vivo and in vitro potency assays. The native conformation, morphology, radius of gyration, and antigenic properties of the HBsAg antigen demonstrate high stability to pH treatment, especially in the pH range employed in all stages of HBsAg vaccine production and storage. The HBsAg protein presents thermal melting point close to 56 °C, reaching a more unfolded state after crossing this point, but it only experiences loss of vaccine potency and antigenic properties at 100 °C. Interestingly, a 6-month storage period does not affect vaccine stability, and the results are similar when the protein is kept under refrigerated conditions or at room temperature (20 °C). At frozen temperatures, large aggregates (>200 nm) are formed and possibly cause loss of HBsAg content, but that does not affect the in vivo assay. Furthermore, HBsAg has a well-ordered secondary structure content that is not affected when the protein is formulated with silica SBA-15, targeting the oral delivery of the vaccine. The combined results from all the characterization techniques employed in this study showed the high stability of the antigen at different storage temperature and extreme values of pH. These findings are important for considering the delivery of HBsAg to the immune system via an oral vaccine.

One of the most remarkable examples of cell-penetrating peptides (CPPs) is Penetratin, a 16-mer fragment derived from the Drosophila Antennapedia homeobox. Understanding the structure of Penetratin/DNA complexes is a key factor for the successful design of new vectors for gene delivery and may assist in optimizing molecular carriers based on CPPs. Herein, we present a comprehensive study on the nanoscale structure of noncovalent complexes formed between Penetratin and DNA. The strong cationic nature of the peptide makes it a very efficient agent for condensing DNA strands via electrostatic attraction, and we show for the first time that DNA condensation is accompanied by random-to-β-sheet transitions of Penetratin secondary structure, demonstrating that nucleic acids behave as a structuring agent upon complexation. For the first time, nanoscale-resolved spectroscopy is used to provide single-particle infrared data from DNA carriers based on CPPs, and they show that the structures are stabilized by Penetratin β-sheet cores, whereas larger DNA fractions are preferentially located in the periphery of aggregates. In-solution infrared assays indicate that phosphate diester groups are strongly affected upon DNA condensation, presumably as a consequence of charge delocalization induced by the proximity of cationic amide groups in Penetratin. The morphology is characterized by nanoassemblies with surface fractal features, and short-range order is found in the inner structure of the scaffolds. Interestingly, the formation of beads-on-a-string arrays is found, producing nanoscale architectures that resemble structures observed in early steps of chromatin condensation. A complexation pathway where DNA condensation and peptide pairing into β-sheets are key steps for organization is proposed.

In addition to autophagy, proteasomes are critical for regulating intracellular protein levels and removing misfolded proteins. The 20S proteasome (20SPT), the central catalytic unit, is sometimes flanked by regulatory units at one or both ends. Additionally, proteosomal activation has been associated with increased lifespan in many organisms. Our group previously reported that the gating (open/closed) of the free 20S proteasome is redox controlled, and that S-glutathionylation of two Cys residues (Cys76 and Cys221) in the α5 subunit promotes gate opening. The present study constructed site-directed mutants of these Cys residues, and evaluated the effects these mutations have on proteosome gate opening and yeast cell survival. Notably, the double mutation of both Cys residues (Cys76 and Cys221) rendered the cells nonviable, whereas the lifespan of the yeast carrying the single mutations (α5-C76S or α5-C221S) was attenuated when compared to the wild type counterpart. Furthermore, it was found that α5-C76S or α5-C221S 20SPT were more likely to be found with the gate in a closed conformation. In contrast, a random α5-subunit double mutation (S35P/C221S) promoted gate opening, increased chronological lifespan and provided resistance to oxidative stress. The 20SPT core particle purified from the long-lived strain degraded model proteins (e.g., α-synuclein) more efficiently than preparations obtained from the wild-type counterpart, and also displayed an increased chymotrypsin-like activity. Mass spectrometric analyses of the C76S, C221S, S35P/C221S, S35P and S35P/C76S mutants provided evidence that the highly conserved Cys76 residue of the α5-subunit is the key determinant for gate opening and cellular survival. The present study reveals a sophisticated regulatory mechanism that controls gate opening, which appears to be based on the interactions among multiple residues within the α5-subunit, and consequently impacts the lifespan of yeast.

The combination of simultaneous measurements of small and wide angle X-ray scattering (SAXS/WAXS–SWAXS) to investigate the overall size, shape, and crystallinity of silver nanoparticles and alloyed silver-gold nanoparticles in the size range of 8 to 80 nm is shown. The obtained results for overall size are in agreement with the particle size obtained by differential centrifugal sedimentation (DCS) and transmission electron microscopy (TEM). In addition to the overall size, SWAXS provided precise information about the crystallographic internal structure of the particles, providing a powerful multi-scale tool for structural characterization of the studied systems.

We report the effect of replacement of 5% of the Fe atoms by Ho during the synthesis of magnetic nanoparticles (MNPs) in the original colloidal system composed of Mn, Zn, Fe, O. Without the presence of Ho the MNPs are spherical and, when the Ho is included in the synthesis they change the shape to cubes with rounded edges. Different experimental techniques were used for the structural characterization of both systems. The magnetic characterization of both colloids showed important differences between them on their magnetic response. The magnetic coupling parameter, the blocking temperature and the effective anisotropy constant are bigger in the colloid with cubic MNPs with respect to the one with spherical particles. The magnetization vs. the applied magnetic field (until 10 kOe) did not show saturation behavior in the colloid with cubic particles, differently from the colloid with spherical particles. This result could be explained taking into account the balance between the energy of the magnetic coupling of the field with the magnetic moment of the cubes, and the thermal energy. The result of Small-angle X-ray scattering (SAXS) pattern confirms the effect of shape due to the Ho substitution in MZ sample. SAXS pattern with and without the presence of external magnetic fields shows non-aggregated particles. The nonlinear optical characterization of the colloids revealed that the imaginary part of the third-order optical susceptibility of the spherical particles is about 30% bigger than that of the cubes.

An expansion of the polyglutamine (polyQ) tract within the deubiquitinase ataxin-3 protein is believed to play a role in a neurodegenerative disorder. Ataxin-3 contains a Josephin catalytic domain and a polyQ tract that renders it intrinsically prone to aggregate, and thus full-length protein is difficult to characterize structurally by high-resolution methods. We established a robust protocol for expression and purification of wild-type and expanded ataxin-3, presenting 19Q and 74Q, respectively. Both proteins are monodisperse as assessed by analytical size exclusion chromatography. Initial biophysical characterization was performed, with apparent transition melting temperature of expanded ataxin-3 lower than the wild-type counterpart. We further characterize the molecular envelope of wild-type and expanded polyQ tract in ataxin-3 using small angle X-ray scattering (SAXS). Characterization of protein-protein interactions between ataxin-3 and newly identified binding partners will benefit from our protocol.

A review is presented on the strategic use of scattering and imaging tools to design immunologic complexes based on porous silica for oral vaccine formulations., This article summarizes developments attained in oral vaccine formulations based on the encapsulation of antigen proteins inside porous silica matrices. These vaccine vehicles show great efficacy in protecting the proteins from the harsh acidic stomach medium, allowing the Peyer’s patches in the small intestine to be reached and consequently enhancing immunity. Focusing on the pioneering research conducted at the Butantan Institute in Brazil, the optimization of the antigen encapsulation yield is reported, as well as their distribution inside the meso- and macroporous network of the porous silica. As the development of vaccines requires proper inclusion of antigens in the antibody cells, X-ray crystallography is one of the most commonly used techniques to unveil the structure of antibody-combining sites with protein antigens. Thus structural characterization and modelling of pure antigen structures, showing different dimensions, as well as their complexes, such as silica with encapsulated hepatitis B virus-like particles and diphtheria anatoxin, were performed using small-angle X-ray scattering, X-ray absorption spectroscopy, X-ray phase contrast tomography, and neutron and X-ray imaging. By combining crystallography with dynamic light scattering and transmission electron microscopy, a clearer picture of the proposed vaccine complexes is shown. Additionally, the stability of the immunogenic complex at different pH values and temperatures was checked and the efficacy of the proposed oral immunogenic complex was demonstrated. The latter was obtained by comparing the antibodies in mice with variable high and low antibody responses.

Gold cylinders with nanometric dimensions were successfully synthesized and characterized by X-ray scattering and diffraction, transmission electron microscopy, dynamic light scattering, and ultraviolet–visible spectroscopy. A small change on the synthesis route led to a slower reaction, allowing better control over the dimensions of the nanorods. The structural characterization enabled the description of the parameters as a function of synthesis time as well as reliable quantification of molar concentrations. The fine-tuning of sizes is crucial for the optimization of the nanorods on specialized applications.

Ultrasmall gold nanoparticles with a metallic core diameter of 2 nm were surface-conjugated with peptides that selectively target epitopes on the surface of the WW domain of the model protein hPin1 (hPin1-WW). The binding to the gold surface was accomplished via the thiol group of a terminal cysteine. The particles were analyzed by NMR spectroscopy, high-resolution transmission electron microscopy, and differential centrifugal sedimentation. The surface loading was determined by conjugating a FAM-labeled peptide, followed by UV-vis spectroscopy, and by quantitative 1H NMR spectroscopy, showing about 150 peptide molecules conjugated to each nanoparticle. The interaction between the peptide-decorated nanoparticles with hPin1-WW was probed by 1H-15N-HSQC NMR titration, fluorescence polarization spectroscopy (FP), and isothermal titration calorimetry (ITC). The particles showed a similar binding (KD = 10-20 μM) compared to the dissolved peptides (KD = 10-30 μM). Small-angle X-ray scattering (SAXS) showed that the particles were well dispersed and did not agglomerate after the addition of hPin1-WW (no cross-linking by the protein). Each nanoparticle was able to bind about 20 hPin1-WW protein molecules. An unspecific interaction with hPin1 was excluded by the attachment of a nonbinding peptide to the nanoparticle surface. The uptake by cells was studied by confocal laser scanning microscopy. The peptide-functionalized nanoparticles penetrated the cell membrane and were located in the cytosol. In contrast, the dissolved peptide did not cross the cell membrane. Peptide-functionalized nanoparticles are promising agents to target proteins inside cells.

Mycobacterium tuberculosis (Mtb) has 11 Serine-Threonine Protein Kinases (STPK) that control numerous physiological processes, including cell growth, cell division, metabolic flow, and transcription. PknF is one of the 11 Mtb STPKs that has, among other substrates, two FHA domains (FHA-1 and FHA-2) of the ATP-Binding Cassette (ABC) transporter Rv1747. Phosphorylation in T152 and T210 located in a non-structured linker that connects Rv1747 FHA domains is considerate to be the regulatory mechanism of the transporter. In this work, we resolved the three-dimensional structure of the PknF catalytic domain (cPknF) in complex with the human kinase inhibitor IKK16. cPknF is conserved when compared to other STPKs but shows specific residues in the binding site where the inhibitor is positioned. In addition, using Small Angle X-Ray Scattering analysis we monitored the behavior of the wild type and three FHA-phosphomimetic mutants in solution, and measured the cPknF affinity for these domains. The kinase showed higher affinity for the non-phosphorylated wild type domain and preference for phosphorylation of T152 inducing the rapprochement of the domains and significant structural changes. The results shed some light on the process of regulating the transporter's activity by phosphorylation and arises important questions about evolution and importance of this mechanism for the bacillus., Graphical abstract Image 1, Highlights • Rv1747 is an ABC transporter which activity is regulated by PknF. • cPknF is a typical Serine/Threonine Protein Kinase that can be explored as drug target. • The higher affinity of cPknF for FHA-2 is important for further conformational changes. • Rv1747 activation model reveals a concatenated activity essential for the system.

Ultrasmall gold nanoparticles (diameter about 2 nm) were surface‐functionalized with cysteine‐carrying precision macromolecules. These consisted of sequence‐defined oligo(amidoamine)s (OAAs) with either two or six cysteine molecules for binding to the gold surface and either with or without a PEG chain (3400 Da). They were characterized by 1H NMR spectroscopy, 1H NMR diffusion‐ordered spectroscopy (DOSY), small‐angle X‐ray scattering (SAXS), and high‐resolution transmission electron microscopy. The number of precision macromolecules per nanoparticle was determined after fluorescent labeling by UV spectroscopy and also by quantitative 1H NMR spectroscopy. Each nanoparticle carried between 40 and 100 OAA ligands, depending on the number of cysteine units per OAA. The footprint of each ligand was about 0.074 nm2 per cysteine molecule. OAAs are well suited to stabilize ultrasmall gold nanoparticles by selective surface conjugation and can be used to selectively cover their surface. The presence of the PEG chain considerably increased the hydrodynamic diameter of both dissolved macromolecules and macromolecule‐conjugated gold nanoparticles., Ultrasmall gold nanoparticles (diameter about 2 nm) were surface‐functionalized with cysteine‐carrying precision macromolecules. These consisted of sequence‐defined oligo(amidoamine)s (OAAs) with either two or six cysteine molecules for binding to the gold surface and either with or without a PEG chain (3400 Da). The presence of the PEG chain considerably increased the hydrodynamic diameter of both dissolved macromolecules and macromolecule‐conjugated gold nanoparticles.

Made available in DSpace on 2021-06-25T10:18:30Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-02-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Snakebite envenomation has been categorized by World Health Organization as a category A neglected tropical disease, since it causes chronic psychological disorders, physical disablement and death. Ophidian accidents may cause local myonecrosis that cause drastic sequelae, which are not efficiently neutralized via serum therapy. Phospholipase A2-like (PLA2-like) myotoxins have a major role in the local effects caused by several snake venoms. We previously demonstrated that chicoric acid (CA) is an efficient inhibitor of the BthTX-I myotoxin and solved the X-ray structure of complex. Herein, we assess the oligomeric behavior of the BthTX-I/CA complex in solution under different physical-chemical conditions and using toxin obtained by two different biochemical methodologies to fully elucidate structural bases of inhibition of myotoxins by CA. We demonstrated the ability of PLA2-like proteins to form different oligomeric assemblies in the presence of certain inhibitors, which can also be modulated by buffer polarity change. In the presence of ethanol, BthTX-I/CA remains predominantly in a monomeric conformation, which prevents it from being in its active form (dimeric conformation). In contrast, in the absence of ethanol, the tetramer assembly was observed, which hid key regions of the protein responsible for docking and disruption of the muscle membrane. Therefore, the “plasticity” of these proteins with regard to their abilities to form oligomeric assemblies is a key issue for the future development of therapeutic agents to complement of serum therapy. Departamento de Biofísica e Farmacologia Instituto de Biociências Universidade Estadual Paulista (UNESP) Instituto de Física Universidade de São Paulo (USP) Departamento de Biofísica e Farmacologia Instituto de Biociências Universidade Estadual Paulista (UNESP)

Na+/Ca2+ exchangers (NCX) are secondary active transporters that couple the translocation of Na+ with the transport of Ca2+ in the opposite direction. The exchanger is an essential Ca2+ extrusion mechanism in excitable cells. It consists of a transmembrane domain and a large intracellular loop that contains two Ca2+-binding domains, CBD1 and CBD2. The two CBDs are adjacent to each other and form a two-domain Ca2+-sensor called CBD12. Binding of intracellular Ca2+ to CBD12 activates the NCX but inhibits the Na+/Ca2+ exchanger of Drosophila, CALX. NMR spectroscopy and SAXS studies showed that CALX and NCX CBD12 constructs display significant inter-domain flexibility in the Apo state, but assume rigid inter-domain arrangements in the Ca2+-bound state. However, detailed structure information on CBD12 in the Apo state is missing. Structural characterization of proteins formed by two or more domains connected by flexible linkers is notoriously challenging and requires the combination of orthogonal information from multiple sources. As an attempt to characterize the conformational ensemble of CALX-CBD12 in the Apo state, we applied molecular dynamics (MD) simulations, NMR (1H-15N RDCs) and Small-Angle X-Ray Scattering (SAXS) data in a combined modelling strategy that generated atomistic information on the most representative conformations. This joint approach demonstrated that CALX-CBD12 preferentially samples closed conformations, while the wide-open inter-domain arrangement characteristic of the Ca2+-bound state is less frequently sampled. These results are consistent with the view that Ca2+ binding shifts the CBD12 conformational ensemble towards extended conformers, which could be a key step in the Na+/Ca2+ exchangers’ allosteric regulation mechanism. The present strategy, combining MD with NMR and SAXS, provides a powerful approach to select representative structures from ensembles of conformations, which could be applied to other flexible multi-domain systems.SIGNIFICANCEThe conformational ensemble of CALX-CBD12, the main Ca2+-sensor of Drosophila’s Na+/Ca2+ exchanger, was characterized by a combination of MD simulations with SAXS and NMR data using the EOM approach. This analysis showed that this two-domain construct experiences opening-closing motions, providing molecular information about CALX-CBD12 in the Apo state. Ca2+-binding shifts the conformational ensemble towards extended conformers. These findings are consistent with a model according to which Ca2+ modulation of CBD12 plasticity is a key step in the Ca2+-regulation mechanism of the full-length exchanger.

We investigate a lyotropic mixture presenting in the calamitic nematic phase ( N C ) and its corresponding calamitic cholesteric phase ( Ch C ), where a small amount of the chiral agent (brucine sulfate) was added. Different experimental techniques (polarized optical microscopy and laser conoscopy) were used to characterize the phases. The main technique employed in the analysis of the structure and local ordering at nanoscale is the Small-Angle X-ray Scattering, where advanced modeling analysis were applied. The lyotropic nematic mixtures was composed of potassium laurate/potassium sulfate/dodecanol/water and the cholesteric phases were obtained from these mixtures, by adding the chiral molecule, brucine sulfate. From an advanced modeling analysis, we show that the micellar overall shape is not modified by the doping with brucine. However, the presence of the brucine between micelles in the Ch C phase imposes a higher correlation between micelles along the direction of the pseudo-lamellar ordering. Finally, the order parameter P 2 was calculated and these values for the phases N C and Ch C are 0.8133(6) and 0.747(2), respectively, indicating a slightly higher orientational ordering in the N C phase.

The aggregation of two short peptides, [RF] and [RF]4 (where R = arginine and F = phenylalanine), at dipalmitoylphosphatidylcholine (DPPC) model membranes was investigated at the air–water interface using the Langmuir technique and vesicles in aqueous solutions. The molar ratio of the peptide and lipid components was varied to provide insights into the peptide–membrane interactions, which might be related to their cytotoxicity. Both peptides exhibited affinity to the DPPC membrane interface and rapidly adopted β-sheet-rich structures upon adsorption onto the surface of the zwitterionic membrane. Results from adsorption isotherm and small-angle X-ray scattering experiments showed changes in the structural and thermodynamic parameters of the membrane with increasing peptide concentration. Using atomic force microscopy, we showed the appearance of pores through the bilayer membranes and peptide aggregation at different interfaces, suggesting that the hydrophobic residues might have an effect on both pore size and layer structure, facilitating the membrane disruption and leading to different cytotoxicity effects.

Two commercial exogenous pulmonary surfactants, Curosurf and Survanta, are investigated. Their thermotropic behavior and associated structural changes for the samples in bulk are characterized and described. For Survanta, the obtained results of differential scanning calorimetry showed a thermogram with three peaks on heating and only a single peak on cooling. Curosurf on the other hand, presents calorimetric thermograms with only one peak in both the heating and cooling scans. This distinct thermotropic behavior between the two pulmonary surfactants, a consequence of their particular compositions, is associated with structural changes that were evaluated by simultaneous small- and wide-angle X-ray scattering experiments with in situ temperature variation. Interestingly, for temperatures below ∼35 °C for Curosurf and ∼53 °C for Survanta, the scattering data indicated the coexistence of two lamellar phases with different carbon chain organizations. For temperatures above these limits, the coexistence of phases disappears, giving rise to a fluid phase in both pulmonary surfactants, with multilamelar vesicles for Curosurf and unilamellar vesicles for Survanta. This process is quasi-reversible under cooling, and advanced data analysis for the scattering data indicated differences in the structural and elastic properties of the pulmonary surfactants. The detailed and systematic investigation shown in this work expands on the knowledge of the structure and thermodynamic behavior of Curosurf and Survanta, being relevant from both physiological and biophysical perspectives and also providing a basis for further studies on other types of pulmonary surfactants.

Snakebite envenomation has been categorized by World Health Organization as a category A neglected tropical disease, since it causes chronic psychological disorders, physical disablement and death. Ophidian accidents may cause local myonecrosis that cause drastic sequelae, which are not efficiently neutralized via serum therapy. Phospholipase A

The activation process of phospholipase A

Multi-drug resistance (MDR) is a serious threat to global public health, making the development of new antimicrobials an urgent necessity. Pyocins are protein antibiotics produced by Pseudomonas aeruginosa strains to kill closely related cells during intraspecific competition. Here, we report an in depth biochemical, microbicidal and structural characterization of a new S-type pyocin, named S8. Initially, we described the domain organization and secondary structure of S8. Subsequently, we observed that a recombinant S8 composed of the killing subunit in complex with the immunity (Im) protein killed the strain PAO1. Furthermore, mutation of a highly conserved glutamic acid to alanine (Glu100Ala) completely inhibited this antimicrobial activity. Probably the integrity of the H-N-H motif is essential in the killing activity of S8, as Glu100 is a highly conserved component of this structure. Next, we observed that S8 is a metal-dependent endonuclease, as EDTA treatment abolished its ability to cleave supercoiled pUC18 plasmid. Supplementation of apo S8 with Ni2+ strongly induced this DNase activity, whereas Mn2+ and Mg2+ exhibited moderate effects and Zn2+ was inhibitory. Additionally, S8 bound Zn2+ with a higher affinity than Ni2+ and the Glu100Ala mutation decreased the affinity of S8 for these metals as shown by isothermal titration calorimetry (ITC). Finally, we describe the crystal structure of the Glu100Ala pyocin-S8DNase-Im complex at 1.38 Å, which gave us new insights into the endonuclease activity of S8. Our results reinforce the possible use of S8 as an alternative antibiotic for MDR Pseudomonas aeruginosa strains, while leaving commensal human microbiota intact.

Multidrug resistance (MDR) is a serious threat to public health, making the development of new antimicrobials an urgent necessity. Pyocins are protein antibiotics produced by Pseudomonas aeruginosa strains to kill closely related cells during intraspecific competition. Here, we report an in-depth biochemical, microbicidal, and structural characterization of a new S-type pyocin, named S8. Initially, we described the domain organization and secondary structure of S8. Subsequently, we observed that a recombinant S8 composed of the killing subunit in complex with the immunity (ImS8) protein killed the strain PAO1. Furthermore, mutation of a highly conserved glutamic acid to alanine (Glu100Ala) completely inhibited this antimicrobial activity. The integrity of the H-N-H motif is probably essential in the killing activity of S8, as Glu100 is a highly conserved residue of this motif. Next, we observed that S8 is a metal-dependent endonuclease, as EDTA treatment abolished its ability to cleave supercoiled pUC18 plasmid. Supplementation of apo S8 with Ni2+ strongly induced this DNase activity, whereas Mn2+ and Mg2+ exhibited moderate effects and Zn2+ was inhibitory. Additionally, S8 bound Zn2+ with a higher affinity than Ni2+ and the Glu100Ala mutation decreased the affinity of S8 for these metals, as shown by isothermal titration calorimetry (ITC). Finally, we describe the crystal structure of the Glu100Ala S8 DNase-ImS8 complex at 1.38 Å, which gave us new insights into the endonuclease activity of S8. Our results reinforce the possibility of using pyocin S8 as an alternative therapy for infections caused by MDR strains, while leaving commensal human microbiota intact. IMPORTANCE Pyocins are proteins produced by Pseudomonas aeruginosa strains that participate in intraspecific competition and host-pathogen interactions. They were first described in the 1950s and since then have gained attention as possible new antibiotics. However, there is still only scarce information about the molecular mechanisms by which these molecules induce cell death. Here, we show that the metal-dependent endonuclease activity of pyocin S8 is involved with its antimicrobial action against strain PAO1. We also describe that this killing activity is dependent on a conserved Glu residue within the H-N-H motif. The potency and selectivity of pyocin S8 toward a narrow spectrum of P. aeruginosa strains make this protein an attractive antimicrobial alternative for combatting MDR strains, while leaving commensal human microbiota intact.

SBA-15 ordered mesoporous silica can be considered a promising inorganic nanocarrier with emerging potential as an oral vaccine adjuvant. In this study, we investigated its application in the encapsulation of the diphtheria anatoxin (dANA). We observed a considerable preservation of dANA secondary and tertiary structures, even after the drying process by means of Circular Dichroism (CD) and fluorescence spectroscopies. Antigen loading was assessed at a number of different ratios of adjuvant-to-antigen using a combination of nitrogen adsorption porosimetry and Small Angle X-ray Scattering (SAXS). Our data showed that the mass ratio of 1:10 (dANA:SBA-15) is recommended for total encapsulation of dANA in the mesopores, considering that at this relative mass concentration antigen clustering was avoided, which is deleterious effect for immunization purposes. dANA release in mimetic intestine fluid, at a pH equal to 6.8, was followed by in-situ SAXS measurements and shown to be slow, being more pronounced after 6 h and continuous up to 35 h. Finally, the immunogenic complex was tested in isogenic Balb C mice by oral and subcutaneous immunization routes, including a comparison with the only permitted adjuvant for human use, aluminum hydroxide. A higher antibody titer was obtained by subcutaneous and oral administration routes using SBA-15 as the vehicle of dANA, compared with the conventional aluminum hydroxide, demonstrating the viability to use this ordered mesoporous silica in the formulation of oral vaccines, as already proved for the Virus Like Particles (VLP) Hepatitis B (HBsAg) case.

Heterogeneous catalysis for biodiesel production is a current challenge due to the low activity of solid catalysts, especially caused by diffusional resistances. Hybrid silicas, containing SiO−CTA+ provide high conversions in the transesterification of oils and model molecules, but this activity is limited to the external surface area. The generation of surface roughness in the silica particles can increase the external area of the catalysts and expose the catalytic sites. Rough silicas containing cetyltrimethylammonium (CTA+) surfactant were prepared using different [CTABr]/[TEOS] molar ratios in a biphasic system formed by diethyl ether and water. The resulting solids were characterized by FTIR, O1s XPS, TG, SEM, and TEM. These materials were applied as basic catalysts in a model transesterification reaction representing the formation of biodiesel. Increasing the CTA+ content in the synthesis resulted in higher turnover frequencies, due to the smaller particle size and greater surface roughness of the material, which enhanced the accessibility of reagents to the basic siloxy sites.

The photocatalytic activity of TiO2 nanoparticles (NPs) supported on mesoporous silica SBA-15 (TiO2/SBA-15) was evaluated for the photodegradation of sulfadiazine (SDZ), as target contaminant of emerging concern (CEC), using either pure water solutions (PW) or a real secondary urban wastewater (UWW) spiked with SDZ. For this purpose, TiO2/SBA-15 samples with 10, 20 and 30% TiO2 (w/w) were prepared by the sol-gel post synthetic method on pre-formed SBA-15, using titanium (IV) isopropoxide as a precursor. The TiO2/SBA-15 materials were characterized by HRTEM, SAXS and XRD, nitrogen adsorption isotherms and UV–vis diffuse reflectance spectroscopy. TiO2 NPs were shown to be attached onto the external surface, decorating the SBA-15 particles. The TiO2/SBA-15 catalysts were active in SDZ photodegradation using the annular FluHelik photoreactor, when irradiated with UVA light. The 30% TiO2/SBA-15 sample presented the best performance in optimization tests performed using PW, and it was further used for the tests with UWW. The photocatalytic activity of 30% TiO2/SBA-15 was higher (56% SDZ degradation) than that of standard TiO2–P25 (32% SDZ degradation) in the removal of SDZ spiked in the UWW ([SDZ] = 2 mg L−1). The photodegradation of SDZ with 30% TiO2/SBA-15 eached 90% for UWW spiked with a lower SDZ concentration ([SDZ] = 40 μg L−1). Aside of SDZ, a suit of 65 other CECs were also identified in the UWW sample using LC-MS spectrometry. A fast-screening test showed the heterogeneous photocatalytic system was able to remove most of the detected CECs from UWW, by either adsorption and/or photocatalysis. SB and ACSCT acknowledge the São Paulo Research Foundation (FAPESP) for the financial support (grants #2016/05496–2 and #2018/21271–6, respectively). BC thanks the National Council for Scientific and Technological Development (CNPq) (grant #204891/2018–3) for supporting the interchange research period at Faculty of Engineering University of Porto (Portugal). ACSCT also thanks the National Council for Scientific and Technological Development (CNPq) (grant #307481/2017–4). The authors thank the Multiuser Central Facilities (UFABC) for the analytical support. This work was also financially supported by the i) Base Funding - UIDB/50020/2020 of the Associate Laboratory LSRE-LCM - funded by national funds through FCT / MCTES (PIDDAC); ii) the European Regional Development Fund (ERDF) through the Interreg V-A Spain-Portugal Programme (POCTEP) 2014–2020 (ref. 0725_NOR_WATER_1_P). Vítor J.P. Vilar acknowledges the FCT Individual Call to Scientific Employment Stimulus 2017 (CEECIND/01317/2017). The team of the University of Santiago acknowledges funding by Xunta de Galicia (ED431C2017), the Spanish Agencia Estatal de Investigación (ref. CTM 2017-84763-C3-R-2), partly cofounded by the ERDF. 2023-08-24 SI

The development of nanoscale emulsions containing high concentration of vegetable oil and low concentration of surfactant is considered challenging in conventional low-energy processes such as the Phase Inversion Temperature (PIT) and Phase Inversion Composition (PIC) methods. For the first time, a stable 20–30 nm oil-in-water nanoemulsion, containing 40.0% (w/w) olive oil was obtained with 2.0% (w/w) single hydrophilic surfactant, applying D-Phase Emulsification (DPE) process in combination with the Box-Behnken statistical design. The preparation of control samples using the PIT and PIC methods resulted in the absence of emulsion formation under the same composition and conditions followed by the DPE process. As a variable influencing the mean particle size of the nanoemulsion in this specific process, the polyol was confirmed to be crucial as the fourth component. An isotropic phase was revealed in place of a liquid crystalline structure or conventional microemulsion phase, enabling easy dispersion of the high oil content in the oil-in-surfactant intermediate phase, during this process. The presence of an initial isotropic phase indicated that there is no need for a strict adjustment of the hydrophilic-lipophilic balance (HLB), nor of the initial water-in-oil phase as in conventional low-energy methods. The results obtained in the present study confirmed the unique feature of the DPE process, overcoming the limitation of conventional low energy methods, for the development of nanoemulsions with high vegetable oil content as a drug delivery system.

With well-known nutritional properties, casein contributes to about 80% of protein content in milk and has been classified as highly intrinsically disordered protein (IDP). In this paper, the sulfate dodecyl sodium (SDS)-induced conformational changes of bovine casein were studied by multi-techniques. Isothermal titration calorimetry (ITC) and differential scanning calorimetry (DSC) were used to obtain the stoichiometry of conformational changes and the thermal stability of the formed complexes. Spectral results indicated that casein presented a higher helical content but loss of tertiary structure above critical micelle concentration of SDS, namely, the so-called molten globule like state. The thermal self-association of casein could be prevented by SDS according to far-UV CD even at 70 °C. The 1H NMR spectrum of casein showed that the resonance around 1.0 ppm, the region of α-hydrogen, shifted to the higher field, and the aromatic region around 5.5–8.0 ppm shifted to the lower field, while the NOESY spectra of casein exhibited few chemical shifts with binding of SDS. Combining the results of dynamic light scattering (DLS), scanning electron microscope (SEM) and small angle x-ray scattering (SAXS), one obtains that casein micelles presented an elliptical shape of ∼800 nm in diameter and upon binding with SDS, the casein micelles disassociated into more compact globular particles of 10 nm in diameter with a core-shell structure composed by SDS molecules and casein proteins. The present work, not only provides molecular insights into the mechanism of SDS-induced stability of a model IDP, casein, but also helps understand the role of surfactants on the structure–function relationship of bovine casein in the food industry.

We synthesized and characterized the colloidal suspensions of [Formula: see text] nanoparticles with x = 0.00, 0.02, 0.04, 0.06 and 0.1. The effect of the Fe3+ ion replacement by Nd3+ on the crystal structure is in-depth studied. The samples were characterized by the following techniques: X-ray diffraction (XRD), UV-Vis spectrophotometry, transmission electronic microscopy (TEM), small-angle X-ray scattering (SAXS), magnetization as a function of applied magnetic field (M-H loops) and magnetization as a function of temperature in zero-field-cooled and field-cooled regimes (ZFC-FC). From XRD cation distribution, structural parameters were extracted. The increasing in the bandgap is interpreted as a result of the higher interatomic separation with the doping. TEM micrographs reveal a polydisperse size and shape distribution of particles. The results for the volume-weighted average diameter measured by SAXS are consistent with those determined by XRD. From the M-H loops we found that the superparamagnetic (SPM) regime contributes with 95-97% for all samples, while only 3-5% contribution comes from the paramagnetic (PM) regime. The saturation magnetization increases in a steady manner upon increasing the Nd3+ ion molar ratio from 0.00 up to 0.06, reaching the maximum value of 105.8±0.4 Am2/kg at x = 0.06. It is worth to mention that the result for the saturation magnetization value are higher than that of the bulk material.

This study aimed the production of multilamellar liposomes coencapsulating two hydrophobic bioactives, curcumin and vitamin D3, which present antioxidant and nutraceutical properties. Liposomes were produced by proliposomes hydration and stabilized with a mixture of xanthan and guar gums. Proliposomes were produced by coating of micronized sucrose method. Physicochemical properties of the dispersions were evaluated over 42 days of refrigerated storage. Microstructural characterization were performed by differential scanning calorimetry (DSC), small-angle X-ray scattering (SAXS) and small deformation rheological analyses. Liposomes showed spherical and near-spherical shapes and presented hydrodynamic diameters in the 680–1580 nm range. Curcumin and cholecalciferol were loaded into the same vesicles, with preservation efficiencies ranging from 89.6 to 93.3% and from 88.3 to 91.3%, respectively, after 42 days of storage. SAXS data showed that the lipid bilayer of liposomes produced in the presence of curcumin, vitamin D3, or a mixture of both, are very similar. Also, higher amounts of vitamin D3 did not affect negatively the stability of phospholipid vesicles. Overall, it was demonstrated that the coencapsulation of curcumin and vitamin D3 by liposomes is feasible and high contents of bioactives were retained throughout the storage time.

In this paper, the calcination of SBA-15 in vacuum is followed by in situ and ex situ small angle X-ray scattering (SAXS) measurements at different temperatures and the material properties are compared with the conventional calcination process in nitrogen and air. The whole process of template decomposition and by-products elimination is investigated as a function of temperature, showing early stages of polymer decomposition at 200 °C. The textural properties of the vacuum-calcined material, analyzed by nitrogen adsorption isotherm data at the end of the calcination process at 540 °C, revealed a smaller surface area and no detectable volume of micropores. A sharp monomodal pore size distribution with a mean value around 108 A is obtained, larger than the material calcined via the usual procedure, which gives values around 98 A. The results indicate that the vacuum heat treatment is an alternative calcination strategy for applications which require a well-ordered mesoporous structure, rigid pore walls, and large pore diameters.

The many applications of the chitosan biopolymers in the areas of nanotechnology and nanomaterials have led to the need to develop novel techniques suitable for the production of nanochitosan. At present these typically involve the use of chemical agents to form chitosan nanoparticles. Physical, chemical, and enzymatic methods have been described for the depolymerizatiton of chitosan. In this work, evaluation was made of the efficiency of a combination of physical methods, including milling of the raw material and drying of the final chitosan, in order to obtain nanochitosan with low molar mass. The results revealed the effectiveness of the combination of milling the raw material under controlled conditions for 4.5 h and drying of the chitosan by thermal shock, which provided depolymerization of up to 10× and resulted in chitosan with Mv less than 21 kDa and hydrodynamic diameter below 30 nm.

Hydroxyapatite is one of the most important biomaterials whose application mainly extends to implants and drug delivery. This work will discuss the changes in the pore size distribution of hydroxyapatite when there are latex beads present during the synthesis. These changes were monitored using different techniques: small angle X-ray scattering, X-ray diffraction, thermal gravimetrical analysis, N2 adsorption, scanning and transmission electron microscopy. Latex beads and hydroxyapatite form a single nanocomposite with well-distinguished inorganic and organic phases. Latex bead removal in the temperature range of 300–600 °C did not modify the original crystalline structure of hydroxyapatite. However, the latex beads favored an increase in the adsorption capacity of mesopores at temperatures higher than their glassy transition (Tg). The main result of this research work consists on the increase of surface area and pore size distribution obtained after the removal of latex beads template. Latex beads have been used in a different approach changing the porosity of hydroxyapatite scaffolds not only introducing new routes for cell integration but also broadening the pore size distribution which can result in a more high efficiency for drug release in living cells.

In this work, we developed a coarse-grained model of sumatriptan suitable for extensive molecular dynamics simulations. First, we confirmed the interfacial distribution of this drug in bilayers through cryogenic transmission electron microscopy and small-angle X-ray scattering techniques, as was predicted by our previous atomistic simulations. Based on these simulations, we developed a coarse-grained model for sumatriptan able to reproduce its overall molecular behavior, captured by atomistic simulations and experiments. We then tested the sumatriptan model in a micellar environment along with experimental characterization of sumatriptan-loaded micelles. The simulation results showed good agreement with photon correlation spectroscopy and electrophoretic mobility experiments performed in this work. The particle size of the obtained micelles was comparable with the simulated ones; meanwhile, zeta-potential results suggest adsorption of the drug on the micellar surface. This model is a step forward in the search for a suitable drug-delivery system for sumatriptan. Fil: Wood, Irene. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentina Fil: Albano, Juan Manuel Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentina Fil: Filho, Pedro L. O.. Universidade de Sao Paulo; Brasil Fil: Couto, Veronica Muniz. Universidade Estadual de Campinas; Brasil Fil: Farias, Marcelo A. de. Ministério da Ciência, Tecnologia, Inovações e Comunicações. Centro Nacional de Pesquisa em Energia e Materiais; Brasil Fil: Portugal, Rodrigo V.. Ministério da Ciência, Tecnologia, Inovações e Comunicações. Centro Nacional de Pesquisa em Energia e Materiais; Brasil Fil: de Paula, Eneida. Universidade Estadual de Campinas; Brasil Fil: Oliveira, Cristiano L. P.. Universidade de Sao Paulo; Brasil Fil: Pickholz, Mónica Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentina