Langmuir Films of Petroleum at the Air-Water Interface

Understanding the behavior of petroleum films at the air/water interface is crucial for dealing with oil sticks and reducing the damages to the environment, which has normally been attempted with studies of Langmuir films made of fractions of petroleum. However, the properties of films from whole petroleum samples may differ considerably from those of individual fractions, Using surface pressure and surface potential measurements and Brewster angle and fluorescence microscopy, we show that petroleum forms it nonhomogeneous Langmuir film at the air-water interface. The surface pressure isotherms for petroleum Langmuir films exhibit gas (G), liquid-expanded (LE), and liquid-condensed phases, with almost no hysteresis in the compression-decompression cycles. Domains formed upon compression from the G to the LE phase were accompanied by an increase in fluorescence intensity with excitation at 400-440 nm owing to an increase in the surface density of the chromophores in the petroleum film. The surface pressure and the fluorescence microscopy data pointed to self-assembling domains into a pseudophase in thermo-dynamic equilibrium with other less emitting petroleum components. This hypothesis was supported by Brewster angle microscopy images, whereby the appearance of water domains even at high surface pressures confirms the tendency of petroleum to stabilize emulsion systems. The results presented here suggest that, for understanding the interaction with water, it may be more appropriate to use the whole petroleum samples rather than its fractions.

Monomolecular films of cholesterol oxidase and S-Layer proteins

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Jacalin interaction with human immunoglobulin A1 and bovine immunoglobulin G1: Affinity constant determined by piezoelectric biosensoring

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

A hydrogel scaffold that maintains viability and supports differentiation of dental pulp stem cells

Objectives: The clinical translation of stem cell-based Regenerative Endodontics demands further development of suitable injectable scaffolds. Puramatrix™ is a defined, self-assembling peptide hydrogel which instantaneously polymerizes under normal physiological conditions. Here, we assessed the compatibility of Puramatrix™ with dental pulp stem cell (DPSC) growth and differentiation. Methods: DPSC cells were grown in 0.05-0.25% Puramatrix™. Cell viability was measured colorimetrically using the WST-1 assay. Cell morphology was observed in 3D modeling using confocal microscopy. In addition, we used the human tooth slice model with Puramatrix™ to verify DPSC differentiation into odontoblast-like cells, as measured by expression of DSPP and DMP-1. Results: DPSC survived and proliferated in Puramatrix™ for at least three weeks in culture. Confocal microscopy revealed that cells seeded in Puramatrix™ presented morphological features of healthy cells, and some cells exhibited cytoplasmic elongations. Notably, after 21 days in tooth slices containing Puramatrix™, DPSC cells expressed DMP-1 and DSPP, putative markers of odontoblastic differentiation. Significance: Collectively, these data suggest that self-assembling peptide hydrogels might be useful injectable scaffolds for stem cell-based Regenerative Endodontics. © 2012 Academy of Dental Materials.

Interação do peptídeo MP-I com micela de SDS em solução aquosa: um estudo por dinâmica molecular

Pós-graduação em Biofísica Molecular - IBILCE

Estudo de processos redox enzimáticos confinados em eletrodos pelo concomitante monitoramento da variação de massa e da corrente: o caso da penicilinase como modelo

Pós-graduação em Biotecnologia - IQ

Educação continuada do catalogador na modalidade a distância: uma proposta alternativa

This paper presents a proposal for the teaching of cataloguing, emphasizing the problem-solving methodology. The proposal was designed for the distance-based continuing education of the professional cataloguer. It takes into account the challenges inherent to the development of interactive and inter-disciplinary tasks, as well as the development of directed self-education and critical consciousness of that professional, inasmuch as he becomes an active subject, manager of his/her own education.

Jacalin interaction with human immunoglobulin A1 and bovine immunoglobulin G1: Affinity constant determined by piezoelectric biosensoring

The affinity of the d-galactose-binding lectin from Artocarpus heterophyllus lectin, known as jacalin, with immonuglobulins (Igs) was determined by biofunctionalization of a piezoelectric transducer. This piezoelectric biofunctionalized transducer was used as a mass-sensitive analytical tool, allowing the real-time binding analysis of jacalin-human immunoglobulin A1 (IgA(1)) and jacalin-bovine IgG(1) interactions from which the apparent affinity constant was calculated. The strategy was centered in immobilizing jacalin on the gold electrode's surface of the piezoelectric crystal resonator using appropriate procedures based on self-assembling of 11-mercaptoundecanoic acid and 2-mercaptoethanol thiol's mixture, a particular immobilization strategy by which it was possible to avoid cross-interaction between the proteins over electrode's surface. The apparent affinity constants obtained between jacalin-human IgA(1) and jacalin-bovine IgG(1) differed by 1 order of magnitude [(8.0 +/- 0.9) x 10(5) vs (8.3 +/- 0.1) x 10(6) L mol(-1)]. On the other hand, the difference found between human IgA(1) and human IgA(2) interaction with jacalin, eight times higher for IgA(1), was attributed to the presence of O-linked glycans in the IgA(1) hinge region, which is absent in IgA(2). Specific interaction of jacalin with O-glycans, proved to be present in the human IgA(1) and hypothetically present in bovine IgG(1) structures, is discussed as responsible for the obtained affinity values.

Studio di biomateriali usati come scaffold per Tissue Engineering e loro caratterizzazione con tecniche spettroscopiche vibrazionali e di analisi termica

This research investigated someone of the main problems connected to the application of Tissue Engineering in the prosthetic field, in particular about the characterization of the scaffolding materials and biomimetic strategies adopted in order to promote the implant integration. The spectroscopic and thermal analysis techniques were usefully applied to characterize the chemico-physical properties of the materials such as – crystallinity; – relative composition in case of composite materials; – Structure and conformation of polymeric and peptidic chains; – mechanism and degradation rate; – Intramolecular and intermolecular interactions (hydrogen bonds, aliphatic interactions). This kind of information are of great importance in the comprehension of the interactions that scaffold undergoes when it is in contact with biological tissues; this information are fundamental to predict biodegradation mechanisms and to understand how chemico-physical properties change during the degradation process. In order to fully characterize biomaterials, this findings must be integrated by information relative to mechanical aspects and in vitro and in vivo behavior thanks to collaborations with biomedical engineers and biologists. This study was focussed on three different systems that correspond to three different strategies adopted in Tissue Engineering: biomimetic replica of fibrous 3-D structure of extracellular matrix (PCL-PLLA), incorporation of an apatitic phase similar to bone inorganic phase to promote biomineralization (PCL-HA), surface modification with synthetic oligopeptides that elicit the interaction with osteoblasts. The characterization of the PCL-PLLA composite underlined that the degradation started along PLLA fibres, which are more hydrophylic, and they serve as a guide for tissue regeneration. Moreover it was found that some cellular lines are more active in the colonization of the scaffold. In the PCL-HA composite, the weight ratio between the polymeric and the inorganic phase plays an essential role both in the degradation process and in the biomineralization of the material. The study of self-assembling peptides allowed to clarify the influence of primary structure on intermolecular and intermolecular interactions, that lead to the formation of the secondary structure and it was possible to find a new class of oligopeptides useful to functionalize materials surface. Among the analytical techniques used in this study, Raman vibrational spectroscopy played a major role, being non-destructive and non-invasive, two properties that make it suitable to degradation studies and to morphological characterization. Also micro-IR spectroscopy was useful in the comprehension of peptide structure on oxidized titanium: up to date this study was one of the first to employ this relatively new technique in the biomedical field.

Supramolecular functional assemblies with photo or chemical addressability

Supramolecular self-assembly represents a key technology for the spontaneous construction of nanoarchitectures and for the fabrication of materials with enhanced physical and chemical properties. In addition, a significant asset of supramolecular self-assemblies rests on their reversible formation, thanks to the kinetic lability of their non-covalent interactions. This dynamic nature can be exploited for the development of “self-healing” and “smart” materials towards the tuning of their functional properties upon various external factors. One particular intriguing objective in the field is to reach a high level of control over the shape and size of the supramolecular architectures, in order to produce well-defined functional nanostructures by rational design. In this direction, many investigations have been pursued toward the construction of self-assembled objects from numerous low-molecular weight scaffolds, for instance by exploiting multiple directional hydrogen-bonding interactions. In particular, nucleobases have been used as supramolecular synthons as a result of their efficiency to code for non-covalent interaction motifs. Among nucleobases, guanine represents the most versatile one, because of its different H-bond donor and acceptor sites which display self-complementary patterns of interactions. Interestingly, and depending on the environmental conditions, guanosine derivatives can form various types of structures. Most of the supramolecular architectures reported in this Thesis from guanosine derivatives require the presence of a cation which stabilizes, via dipole-ion interactions, the macrocyclic G-quartet that can, in turn, stack in columnar G-quadruplex arrangements. In addition, in absence of cations, guanosine can polymerize via hydrogen bonding to give a variety of supramolecular networks including linear ribbons. This complex supramolecular behavior confers to the guanine-guanine interactions their upper interest among all the homonucleobases studied. They have been subjected to intense investigations in various areas ranging from structural biology and medicinal chemistry – guanine-rich sequences are abundant in telomeric ends of chromosomes and promoter regions of DNA, and are capable of forming G-quartet based structures– to material science and nanotechnology. This Thesis, organized into five Chapters, describes mainly some recent advances in the form and function provided by self-assembly of guanine based systems. More generally, Chapter 4 will focus on the construction of supramolecular self-assemblies whose self-assembling process and self-assembled architectures can be controlled by light as external stimulus. Chapter 1 will describe some of the many recent studies of G-quartets in the general area of nanoscience. Natural G- quadruplexes can be useful motifs to build new structures and biomaterials such as self-assembled nanomachines, biosensors, therapeutic aptamer and catalysts. In Chapters 2-4 it is pointed out the core concept held in this PhD Thesis, i.e. the supramolecular organization of lipophilic guanosine derivatives with photo or chemical addressability. Chapter 2 will mainly focus on the use of cation-templated guanosine derivatives as a potential scaffold for designing functional materials with tailored physical properties, showing a new way to control the bottom-up realization of well-defined nanoarchitectures. In section 2.6.7, the self-assembly properties of compound 28a may be considered an example of open-shell moieties ordered by a supramolecular guanosine architecture showing a new (magnetic) property. Chapter 3 will report on ribbon-like structures, supramolecular architectures formed by guanosine derivatives that may be of interest for the fabrication of molecular nanowires within the framework of future molecular electronic applications. In section 3.4 we investigate the supramolecular polymerizations of derivatives dG 1 and G 30 by light scattering technique and TEM experiments. The obtained data reveal the presence of several levels of organization due to the hierarchical self-assembly of the guanosine units in ribbons that in turn aggregate in fibrillar or lamellar soft structures. The elucidation of these structures furnishes an explanation to the physical behaviour of guanosine units which display organogelator properties. Chapter 4 will describe photoresponsive self-assembling systems. Numerous research examples have demonstrated that the use of photochromic molecules in supramolecular self-assemblies is the most reasonable method to noninvasively manipulate their degree of aggregation and supramolecular architectures. In section 4.4 we report on the photocontrolled self-assembly of modified guanosine nucleobase E-42: by the introduction of a photoactive moiety at C8 it is possible to operate a photocontrol over the self-assembly of the molecule, where the existence of G-quartets can be alternately switched on and off. In section 4.5 we focus on the use of cyclodextrins as photoresponsive host-guest assemblies: αCD–azobenzene conjugates 47-48 (section 4.5.3) are synthesized in order to obtain a photoresponsive system exhibiting a fine photocontrollable degree of aggregation and self-assembled architecture. Finally, Chapter 5 contains the experimental protocols used for the research described in Chapters 2-4.

Sistemi liquido cristallini complessi: simulazioni al calcolatore e studi ESR

The aim of this PhD thesis was to study at a microscopic level different liquid crystal (LC) systems, in order to determine their physical properties, resorting to two distinct methodologies, one involving computer simulations, and the other spectroscopic techniques, in particular electron spin resonance (ESR) spectroscopy. By means of the computer simulation approach we tried to demonstrate this tool effectiveness for calculating anisotropic static properties of a LC material, as well as for predicting its behaviour and features. This required the development and adoption of suitable molecular models based on a convenient intermolecular potentials reflecting the essential molecular features of the investigated system. In particular, concerning the simulation approach, we have set up models for discotic liquid crystal dimers and we have studied, by means of Monte Carlo simulations, their phase behaviour and self­-assembling properties, with respect to the simple monomer case. Each discotic dimer is described by two oblate Gay­Berne ellipsoids connected by a flexible spacer, modelled by a harmonic "spring" of three different lengths. In particular we investigated the effects of dimerization on the transition temperatures, as well as on the characteristics of molecular aggregation displayed and the relative orientational order. Moving to the experimental results, among the many experimental techniques that are typically employed to evaluate LC system distinctive features, ESR has proved to be a powerful tool in microscopic scale investigation of the properties, structure, order and dynamics of these materials. We have taken advantage of the high sensitivity of the ESR spin probe technique to investigate increasingly complex LC systems ranging from devices constituted by a polymer matrix in which LC molecules are confined in shape of nano- droplets, as well as biaxial liquid crystalline elastomers, and dimers whose monomeric units or lateral groups are constituted by rod-like mesogens (11BCB). Reflection-mode holographic-polymer dispersed liquid crystals (H-PDLCs) are devices in which LCs are confined into nanosized (50­-300 nm) droplets, arranged in layers which alternate with polymer layers, forming a diffraction grating. We have determined the configuration of the LC local director and we have derived a model of the nanodroplet organization inside the layers. Resorting also to additional information on the nanodroplet size and shape distribution provided by SEM images of the H-PDLC cross-section, the observed director configuration has been modeled as a bidimensional distribution of elongated nanodroplets whose long axis is, on the average, parallel to the layers and whose internal director configuration is a uniaxial quasi- monodomain aligned along the nanodroplet long axis. The results suggest that the molecular organization is dictated mainly by the confinement, explaining, at least in part, the need for switching voltages significantly higher and the observed faster turn-off times in H-PDLCs compared to standard PDLC devices. Liquid crystal elastomers consist in cross-linked polymers, in which mesogens represent the monomers constituting the main chain or the laterally attached side groups. They bring together three important aspects: orientational order in amorphous soft materials, responsive molecular shape and quenched topological constraints. In biaxial nematic liquid crystalline elastomers (BLCEs), two orthogonal directions, rather than the one of normal uniaxial nematic, can be controlled, greatly enhancing their potential value for applications as novel actuators. Two versions of a side-chain BLCEs were characterized: side­-on and end­-on. Many tests have been carried out on both types of LCE, the main features detected being the lack of a significant dynamical behaviour, together with a strong permanent alignment along the principal director, and the confirmation of the transition temperatures already determined by DSC measurements. The end­-on sample demonstrates a less hindered rotation of the side group mesogenic units and a greater freedom of alignment to the magnetic field, as already shown by previous NMR studies. Biaxial nematic ESR static spectra were also obtained on the basis of Molecular Dynamics generated biaxial configurations, to be compared to the experimentally determined ones, as a mean to establish a possible relation between biaxiality and the spectral features. This provides a concrete example of the advantages of combining the computer simulation and spectroscopic approaches. Finally, the dimer α,ω-bis(4'-cyanobiphenyl-4-yl)undecane (11BCB), synthesized in the "quest" for the biaxial nematic phase has been analysed. Its importance lies in the dimer significance as building blocks in the development of new materials to be employed in innovative technological applications, such as faster switching displays, resorting to the easier aligning ability of the secondary director in biaxial phases. A preliminary series of tests were performed revealing the population of mesogenic molecules as divided into two groups: one of elongated straightened conformers sharing a common director, and one of bent molecules, which display no order, being equally distributed in the three dimensions. Employing this model, the calculated values show a consistent trend, confirming at the same time the transition temperatures indicated by the DSC measurements, together with rotational diffusion tensor values that follow closely those of the constituting monomer 5CB.

Abiotic and prebiotic phosphorus chemistry

The chief obstacle to understand the metabolic origin of life or RNA-based life is to identify a plausible mechanism for overcoming the clutter wrought by abiotic chemistry. Probably trough simple abiotic and then prebiotic reactions we could arrive to simple pre-RNA molecules. Here we report a possible preibiotic synthesis for heterocyclic compounds, and a self-assembling process of adenosine phosphates a constituent of RNA. In these processes we use a simple and prebiotic phosphorus cyclic compounds, as P4O10 and its derivatives. The processes are driven by the formation of hypercoordinated species that activate the processes by a factor of 106-8.

Structure, organization and dynamics of functional supramolecular materials studied by solid-state NMR

Functional materials have great importance due to their many important applications. The characterization of supramolecular architectures which are held together by non-covalent interactions is of most importance to understand their properties. Solid-state NMR methods have recently been proven to be able to unravel such structure-property relations with the help of fast magic-angle spinning and advanced pulse sequences. The aim of the current work is to understand the structure and dynamics of functional supramolecular materials which are potentially important for fuel-cell (proton conducting membrane materials) and solar-cell or plastic-electronic applications (photo-reactive aromatic materials). In particular, hydrogen-bonding networks, local proton mobility, molecular packing arrangements, and local dynamics will be studied by the use of advanced solid-state NMR methods. The first class of materials studied in this work is proton conducting polymers which also form hydrogen-bonding network. Different materials, which are prepared for high 1H conduction by different approaches are studied: PAA-P4VP, PVPA-ABPBI, Tz5Si, and Triazole-functional systems. The materials are examples of the following major groups; - Homopolymers with specific functional groups (Triazole functional polysiloxanes). - Acid-base polymer blends approach (PAA-P4VP, PVPA-ABPBI). - Acid-base copolymer approach (Triazole-PVPA). - Acid doped polymers (Triazole functional polymer doped with H3PO4). Perylenebisimide (PBI) derivatives, a second type of important functional supramolecular materials with potent applications in plastic electronics, were also investigated by means of solid-state NMR. The preparation of conducting nanoscopic fibers based on the self-assembling functional units is an appealing aim as they may be incorporated in molecular electronic devices. In this category, perylene derivatives have attracted great attention due to their high charge carrier mobility. A detailed knowledge about their supramolecular structure and molecular dynamics is crucial for the understanding of their electronic properties. The aim is to understand the structure, dynamics and packing arrangements which lead to high electron conductivity in PBI derivatives.

Functional dna nanostructures for in vitro biosensing in live cells

DNA is a fascinating biomolecule that is well known for its genetic role in living systems. The emerging area of DNA nanotechnology provides an alternative view that exploits unparallel self-assembly ability of DNA molecules for material use of DNA. Although many reports exist on the results of DNA self-assembling systems, still few of them focus on the in vitro study about the function of such DNA nanostructures in live cells. Due to this, there are still a limited research about the in vitro functionality of such designs. To address an aspect of this issue, we have designed, synthesized and characterized two multifunctional fluorescencent nanobiosensors by DNA self-assembling. Each structure was designed and implemented to be introduced in live cells in order to give information on their functioning in real-time. Computational tools were used in order to design a graphic model of two new DNA motifs and also to obtain the specific sequences to all the ssDNA molecules. By thermal self-assembly techniques we have successfully synthesized the structure and corroborate their formation by the PAGE technique. In addition, we have established the conditions to characterize their structural conformation change when they perform their sensor response. The sensing behavior was also accomplished by fluorescence spectroscopy techniques; FRET evaluation and fluorescence microscopy imaging. Providing the evidence about their adequate sensing performance outside and inside the cells detected in real-time. In a preliminary evaluation we have tried to show the in vitro functionality of our structures in different cancer cell lines with the ability to perform local sensing responses. Our findings suggest that DNA sensor nanostructures could serve as a platform to exploit further therapeutic achievements in live cells.

Unprecedented Trapping of Difluorooctamolybdate Anions within an α-Polonium Type Coordination Network

New fluorinated hybrid solids [Mo2F2O5(tr2pr)] (1), [Co3(tr2pr)2(MoO4)2F2]·7H2O (2), and [Co3(H2O)2(tr2pr)3(Mo8O26F2)]·3H2O (3) (tr2pr = 1,3-bis(1,2,4-triazol-4-yl)propane) were prepared from the reaction systems consisting of Co(OAc)2/CoF2 and MoO3/(NH4)6Mo7O24, as CoII and MoVI sources, in water (2) or in aqueous HF (1, 3) employing mild hydrothermal conditions. The tr2pr ligand serves as a conformationally flexible tetradentate donor. In complex 1, the octahedrally coordinated Mo atoms are linked in the discrete corner-sharing {Mo2(μ2-O)F2O4N4} unit in which a pair of tr-heterocycles (tr = 1,2,4-triazole) is arranged in cis-positions opposite to “molybdenyl” oxygen atoms. The anti−anti conformation type of tr2pr facilitates the tight zigzag chain packing motif. The crystal structure of the mixed-anion complex salt 2 consists of trinuclear [Co3(μ3-MoO4)2(μ2-F)2] units self-assembling in CoII-undulating chains (Co···Co 3.0709(15) and 3.3596(7) Å), which are cross-linked by tr2pr in layers. In 3, containing condensed oxyfluoromolybdate species, linear centrosymmetric [Co3(μ2-tr)6]6+ SBUs are organized at distances of 10.72−12.45 Å in an α-Po-like network using bitopic tr-linkers. The octahedral {N6} and {N3O3} environments of the central and peripheral cobalt atoms, respectively, are filled by triazole N atoms, water molecules, and coordinating [Mo8O26F2]6− anions. Acting as a tetradentate O-donor, each difluorooctamolybdate anion anchors four [Co3(μ2-tr)6]6+ units through their peripheral Co-sites, which consequently leads to a novel type of a two-nodal 4,10-c net with the Schläfli symbol {32.43.5}{34.420.516.65}. The 2D and 3D coordination networks of 2 and 3, respectively, are characterized by significant overall antiferromagnetic exchange interactions (J/k) between the CoII spin centers on the order of −8 and −4 K. The [Mo8O26F2]6− anion is investigated in detail by quantum chemical calculations.