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Unusual supramolecular assembly and nonlinear optical properties of l-histidinium hydrogen malate

Gomes, E. de Matos; Rodrigues, V. H.; Costa, M. M. R.; Belsley, M. S.; Cardoso, P. J. M.; Gonçalves, C. F.; Proença, F.
Fonte: Universidade de Coimbra Publicador: Universidade de Coimbra
Tipo: Artigo de Revista Científica Formato: aplication/PDF
ENG
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A new nonlinear optical material, l-histidinium hydrogen malate, has been synthesized. The crystal structure was determined at 90 K by single-crystal X-ray diffraction in order to analyze its supramolecular structure. A new building block type has been found. The malate anions form head-to-side infinite chains parallel to [100], via O-H...O interactions, instead of the usual head-to-tail infinite chains found in other hydrogen malate salts. The l-histidine cations form chains parallel to [100] via N-H...O hydrogen bonds, with cations of adjacent chains in anti-parallel way. The compound shows a good optical second-harmonic generation capability with an effective second-order susceptibility estimated to be 0.70 of that for potassium dihydrogen phosphate.; http://www.sciencedirect.com/science/article/B6WM2-4JY4145-3/1/a3f1c7be73432d0bb15977e2639292c6

Crystal structure, supramolecular self-assembly and interaction with DNA of a mixed ligand manganese(II) complex

Sun,Yun-Ming; Dong,Feng-Ying; Wang,Da-Qi; Li,Yan-Tuan
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2011 EN
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A mixed ligand manganese(II) complex, [Mn(sal)(phen)2]ClO4 (1) (sal = salicylaldehyde, phen = 1,10-phenanthroline), has been synthesized and characterized by elemental analysis and single crystal X-ray diffractometry. The structural analysis revealed that complex 1 crystallizes in the monoclinic space group P2(1)/n. The asymmetric unit of the complex is comprised of [Mn(sal)(phen)2]+ complex cation and uncoordinated perchlorate anion. The manganese(II) is located in a seriously distorted octahedral MnN4O2 coordination environment. Four types of π-π stacking modes involving phenanthroline and salicylaldehyde ligands are involved in the supramolecular self-assembly. These aromatic stacking interactions cooperate with hydrogen bonding to assemble the complex into a fascinating 3D supramolecular architecture. Electronic absorption spectroscopy and fluorescence titration studies of the interaction between complex 1 and calf thymus DNA suggest an intercalative binding mode with a constant of 7.97×10³ L mol-1 and a Stern-Volmer quenching constant of 1.34×10(4) L mol-1.

Carbohydrate gluing, an architectural mechanism in the supramolecular structure of an annelid giant hemoglobin.

Ebina, S; Matsubara, K; Nagayama, K; Yamaki, M; Gotoh, T
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 01/08/1995 EN
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We report a carbohydrate-dependent supramolecular architecture in the extracellular giant hemoglobin (Hb) from the marine worm Perinereis aibuhitensis; we call this architectural mechanism carbohydrate gluing. This study is an extension of our accidental discovery of deterioration in the form of the Hb caused by a high concentration of glucose. The giant Hbs of annelids are natural supramolecules consisting of about 200 polypeptide chains that associate to form a double-layered hexagonal structure. This Hb has 0.5% (wt) carbohydrates, including mannose, xylose, fucose, galactose, glucose, N-acetylglucosamine (GlcNAc), and N-acetylgalactosamine (GalNAc). Using carbohydrate-staining assays, in conjunction with two-dimensional polyacrylamide gel electrophoresis, we found that two types of linker chains (L1 and L2; the nomenclature of the Hb subunits followed that for another marine worm, Tylorrhynchus heterochaetus) contained carbohydrates with both GlcNAc and GalNAc. Furthermore, two types of globins (a and A) have only GlcNAc-containing carbohydrates, whereas the other types of globins (b and B) had no carbohydrates. Monosaccharides including mannose, fucose, glucose, galactose, GlcNAc, and GalNAc reversibly dissociated the intact form of the Hb...

Idiotypic mimicry and the assembly of a supramolecular structure: an anti-idiotypic antibody that mimics taxol in its tubulin-microtubule interactions.

Leu, J G; Chen, B X; Diamanduros, A W; Erlanger, B F
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 25/10/1994 EN
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Taxol, originally extracted from the bark of the western yew, Taxus brevifolia, is reportedly the first of a new class of anti-cancer agents. It acts by promoting and irreversibly stabilizing microtubule assembly, thus interfering with the dynamic processes required for cell viability and multiplication. With the aim of using immunological techniques to study the mechanism of action of taxol, a monoclonal anti-idiotypic antibody that mimics taxol was prepared, using an auto-anti-idiotypic strategy. It and its Fab fragment inhibited the binding of [3H]taxol to microtubules. Moreover, like taxol, both promoted the assembly of tubulin into microtubules. These findings provide an example of an anti-idiotypic antibody capable of assembling an organized supramolecular structure from soluble cellular components. In addition, it further establishes the ability of anti-idiotypic antibodies to be functional mimics of ligand molecules bearing no structural similarity to immunoglobulins. The variable regions of the antibody have been sequenced. With the exception of the complementarity-determining region 3, the sequence of the heavy chain variable region is strikingly similar to that of an anti-idiotypic antibody raised to anti-insulin. The finding that a polypeptide can mimic taxol raises the possibility that taxol acts as a peptidomimetic compound that interferes with the function of an endogenous polypeptide.

Supramolecular structure of the Shigella type III secretion machinery: the needle part is changeable in length and essential for delivery of effectors

Tamano, Koichi; Aizawa, Shin-Ichi; Katayama, Eisaku; Nonaka, Takashi; Imajoh-Ohmi, Shinobu; Kuwae, Asaomi; Nagai, Shinya; Sasakawa, Chihiro
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
Publicado em 01/08/2000 EN
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We investigated the supramolecular structure of the Shigella type III secretion machinery including its major components. Our results indicated that the machinery was composed of needle and basal parts with respective lengths of 45.4 ± 3.3 and 31.6 ± 0.3 nm, and contained MxiD, MxiG, MxiJ and MxiH. spa47, encoding a putative F1-type ATPase, was required for the secretion of effector proteins via the type III system and was involved in the formation of the needle. The spa47 mutant produced a defective, needle-less type III structure, which contained MxiD, MxiG and MxiJ but not MxiH. The mxiH mutant produced a defective type III structure lacking the needle and failed to secrete effector proteins. Upon overexpression of MxiH in the mxiH mutant, the bacteria produced type III structures with protruding dramatically long needles, and showed a remarkable increase in invasiveness. Our results suggest that MxiH is the major needle component of the type III machinery and is essential for delivery of the effector proteins, and that the level of MxiH affects the length of the needle.

Molecular structure as a blueprint for supramolecular structure chemistry in confined spaces

Turro, Nicholas J.
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
EN
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The supramolecular structure of the GPCR rhodopsin in solution and native disc membranes

Suda, Kitaru; Filipek, Slawomir; Palczewski, Krzysztof; Engel, Andreas; Fotiadis, Dimitrios
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em //2004 EN
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Rhodopsin, the prototypical G-protein-coupled receptor, which is densely packed in the disc membranes of rod outer segments, was proposed to function as a monomer. However, a growing body of evidence indicates dimerization and oligomerization of numerous G-protein-coupled receptors, and atomic force microscopy images revealed rows of rhodopsin dimers in murine disc membranes. In this work we demonstrate by electron microscopy of negatively stained samples, blue native- and sodium dodecyl sulphate-polyacrylamide gel electrophoresis, chemical crosslinking, and by proteolysis that native bovine rhodopsin exists mainly as dimers and higher oligomers. These results corroborate the recent findings from atomic force microscopy and molecular modeling on the supramolecular structure and packing arrangement of murine rhodopsin dimers.

Atomistic Simulation Approach to a Continuum Description of Self-Assembled β-Sheet Filaments

Park, Jiyong; Kahng, Byungnam; Kamm, Roger D.; Hwang, Wonmuk
Fonte: Biophysical Society Publicador: Biophysical Society
Tipo: Artigo de Revista Científica
EN
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377.58266%
We investigated the supramolecular structure and continuum mechanical properties of a β-sheet nanofiber comprised of a self-assembling peptide ac-[RARADADA]2-am using computer simulations. The supramolecular structure was determined by constructing candidate filaments with dimensions compatible with those observed in atomic force microscopy and selecting the most stable ones after running molecular dynamics simulations on each of them. Four structures with different backbone hydrogen-bonding patterns were identified to be similarly stable. We then quantified the continuum mechanical properties of these identified structures by running three independent simulations: thermal motion analysis, normal mode analysis, and steered molecular dynamics. Within the range of deformations investigated, the filament showed linear elasticity in transverse directions with an estimated persistence length of 1.2–4.8 μm. Although side-chain interactions govern the propensity and energetics of filament self-assembly, we found that backbone hydrogen-bonding interactions are the primary determinant of filament elasticity, as demonstrated by its effective thickness, which is smaller than that estimated by atomic force microscopy or from the molecular geometry...

Molecular and Supramolecular Structural Studies on Human Tropoelastin Sequences

Ostuni, Angela; Bochicchio, Brigida; Armentano, Maria F.; Bisaccia, Faustino; Tamburro, Antonio M.
Fonte: The Biophysical Society Publicador: The Biophysical Society
Tipo: Artigo de Revista Científica
EN
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One of the unusual properties of elastin is its ability to coacervate, which has been proposed to play an important role in the alignment of monomeric elastin for cross-linking into the polymeric elastin matrix. The temperature at which this transition takes place depends on several factors including protein concentration, ionic strength, and pH. Previously, polypeptide sequences encoded by different exons of the human tropoelastin gene have been analyzed for their ability to coacervate and to self-assemble. Few of them were indeed able to coacervate and only one, that encoded by exon 30 (EX30), gave amyloid fibers. In this article, we report on two chemically synthesized peptides—a decapeptide and an octadecapeptide—whose sequences are contained in the longer EX30 peptide and on a polypeptide (EX1–7) of 125 amino-acid residues corresponding to the sequence coded by the exons 1–7 and on a polypeptide (EX2–7) of 99 amino-acid residues encoded by exons 2–7 of human tropoelastin obtained by recombinant DNA techniques. Molecular and supramolecular structural characterization of these peptides showed that a minimum sequence of ∼20 amino acids is needed to form amyloid fibers in the exon 30-derived peptides. The N-terminal region of mature tropoelastin (EX2–7) gives rise to a coacervate and forms elastinlike fibers...

The Role of Lhca Complexes in the Supramolecular Organization of Higher Plant Photosystem I*S⃞

Wientjes, Emilie; Oostergetel, Gert T.; Jansson, Stefan; Boekema, Egbert J.; Croce, Roberta
Fonte: American Society for Biochemistry and Molecular Biology Publicador: American Society for Biochemistry and Molecular Biology
Tipo: Artigo de Revista Científica
Publicado em 20/03/2009 EN
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In this work, Photosystem I supercomplexes have been purified from Lhca-deficient lines of Arabidopsis thaliana using a mild detergent treatment that does not induce loss of outer antennas. The complexes have been studied by integrating biochemical analysis with electron microscopy. This allows the direct correlation of changes in protein content with changes in supramolecular structure of Photosystem I to get information about the position of the individual Lhca subunits, the association of the antenna to the core, and the influence of the individual subunits on the stability of the system. Photosystem I complexes with only two or three antenna complexes were purified, showing that the binding of Lhca1/4 and Lhca2/3 dimers to the core is not interdependent, although weak binding of Lhca2/3 to the core is stabilized by the presence of Lhca4. Moreover, Lhca2 and Lhca4 can be associated with the core in the absence of their “dimeric partners.” The structure of Photosystem I is very rigid, and the absence of one antenna complex leaves a “hole” in the structure that cannot be filled by other Lhcas, clearly indicating that the docking sites for the individual subunits are highly specific. There is, however, an exception to the rule: Lhca5 can substitute for Lhca4...

Oligomerization state and supramolecular structure of the HIV-1 Vpu protein transmembrane segment in phospholipid bilayers

Lu, Jun-Xia; Sharpe, Simon; Ghirlando, Rodolfo; Yau, Wai-Ming; Tycko, Robert
Fonte: Wiley Subscription Services, Inc., A Wiley Company Publicador: Wiley Subscription Services, Inc., A Wiley Company
Tipo: Artigo de Revista Científica
EN
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482.08453%
HIV-1 Vpu is an 81-residue protein with a single N-terminal transmembrane (TM) helical segment that is involved in the release of new virions from host cell membranes. Vpu and its TM segment form ion channels in phospholipid bilayers, presumably by oligomerization of TM helices into a pore-like structure. We describe measurements that provide new constraints on the oligomerization state and supramolecular structure of residues 1–40 of Vpu (Vpu1–40), including analytical ultracentrifugation measurements to investigate oligomerization in detergent micelles, photo-induced crosslinking experiments to investigate oligomerization in bilayers, and solid-state nuclear magnetic resonance measurements to obtain constraints on intermolecular contacts between and orientations of TM helices in bilayers. From these data, we develop molecular models for Vpu TM oligomers. The data indicate that a variety of oligomers coexist in phospholipid bilayers, so that a unique supramolecular structure can not be defined. Nonetheless, since oligomers of various sizes have similar intermolecular contacts and orientations, molecular models developed from our data are most likely representative of Vpu TM oligomers that exist in host cell membranes.

Effect of peptide secondary structure on peptide amphiphile supramolecular structure and interactions

Missirlis, Dimitris; Chworos, Arkadiusz; Fu, Caroline J.; Khant, Htet A.; Krogstad, Daniel V.; Tirrell, Matthew
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
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Bottom-up fabrication of self-assembled nanomaterials requires control over forces and interactions between building blocks. We here report on the formation and architecture of supramolecular structures constructed from two different peptide amphiphiles. Inclusion of four alanines between a 16-mer peptide and a 16-carbon long aliphatic tail resulted in a secondary structure shift of the peptide headgroups from alpha helices to beta sheets. A concomitant shift in self-assembled morphology from nano-ribbons to core-shell wormlike micelles was observed by cryogenic transmission electron microscopy (cryo-TEM) and atomic force microscopy (AFM). In presence of divalent magnesium ions, these a priori formed supramolecular structures interacted in distinct manners, highlighting the importance of peptide amphiphile design in self-assembly.

Influence of the electric field on supramolecular structure and properties of amyloid-specific reagent Congo red

Spólnik, Paweł; Król, Marcin; Stopa, Barbara; Konieczny, Leszek; Piekarska, Barbara; Rybarska, Janina; Zemanek, Grzegorz; Jagusiak, Anna; Piwowar, Piotr; Szoniec, Grzegorz; Roterman, Irena
Fonte: Springer-Verlag Publicador: Springer-Verlag
Tipo: Artigo de Revista Científica
EN
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Among specific amyloid ligands, Congo red and its analogues are often considered potential therapeutic compounds. However, the results of the studies so far have not been univocal because the properties of this dye, derived mostly from its supramolecular nature, are still poorly understood. The supramolecular structure of Congo red, formed by π–π stacking of dye molecules, is susceptible to the influence of the electric field, which may significantly facilitate electron delocalization. Consequently, the electric field may generate altered physico-chemical properties of the dye. Enhanced electron delocalization, induced by the electric field, alters the total charge of Congo red, making the dye more acidic (negatively charged). This is a consequence of withdrawing electrons from polar substituents of aromatic rings—sulfonic and amino groups—thus increasing their tendency to dissociate protons. The electric field-induced charge alteration observed in electrophoresis depends on dye concentration. This concentration-dependent charge alteration effect disappears when the supramolecular structure disintegrates in DMSO. Dipoles formed from supramolecular fibrillar species in the electric field become ordered in the solution, introducing the modified arrangement to liquid crystalline phase. Experimental results and theoretical studies provide evidence confirming predictions that the supramolecular character of Congo red is the main reason for its specific properties and reactivity.

Differences in Cellulosic Supramolecular Structure of Compositionally Similar Rice Straw Affect Biomass Metabolism by Paddy Soil Microbiota

Ogura, Tatsuki; Date, Yasuhiro; Kikuchi, Jun
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 19/06/2013 EN
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Because they are strong and stable, lignocellulosic supramolecular structures in plant cell walls are resistant to decomposition. However, they can be degraded and recycled by soil microbiota. Little is known about the biomass degradation profiles of complex microbiota based on differences in cellulosic supramolecular structures without compositional variations. Here, we characterized and evaluated the cellulosic supramolecular structures and composition of rice straw biomass processed under different milling conditions. We used a range of techniques including solid- and solution-state nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy followed by thermodynamic and microbial degradability characterization using thermogravimetric analysis, solution-state NMR, and denaturing gradient gel electrophoresis. These measured data were further analyzed using an “ECOMICS” web-based toolkit. From the results, we found that physical pretreatment of rice straw alters the lignocellulosic supramolecular structure by cleaving significant molecular lignocellulose bonds. The transformation from crystalline to amorphous cellulose shifted the thermal degradation profiles to lower temperatures. In addition, pretreated rice straw samples developed different microbiota profiles with different metabolic dynamics during the biomass degradation process. This is the first report to comprehensively characterize the structure...

Complex self-assembly of pyrimido[4,5-d]pyrimidine nucleoside supramolecular structures

Zhao, Hang; Guo, Xiurong; He, Shiliang; Zeng, Xin; Zhou, Xinglong; Zhang, Chaoliang; Hu, Jing; Wu, Xiaohua; Xing, Zhihua; Chu, Liangyin; He, Yang; Chen, Qianming
Fonte: Nature Pub. Group Publicador: Nature Pub. Group
Tipo: Artigo de Revista Científica
Publicado em 24/01/2014 EN
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Supramolecular self-assembly is not only one of the chemical roots of biological structure but is also drawing attention in different industrial fields. Here we study the mechanism of the formation of a complex flower-shaped supramolecular structure of pyrimido[4,5-d]pyrimidine nucleosides by dynamic light scattering, scanning electron microscopy, differential scanning calorimetry, nuclear magnetic resonance and X-ray analysis. Upon removing the hydroxyl group of sugars, different flower-shaped superstructures can be produced. These works demonstrate that complex self-assembly can indeed be attained through hierarchical non-covalent interactions of single molecules. Furthermore, chimerical structures built from molecular recognition by these monomers indicate their potential in other fields if combined with other chemical entities.

Template Induction of Supramolecular Structure:

Edler, Karen Jean
Fonte: Universidade Nacional da Austrália Publicador: Universidade Nacional da Austrália
Tipo: Thesis (PhD); Doctor of Philosophy (PhD)
EN_AU
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The pure silicate mesoporous material, MCM-41 having hexagonally packed cylindrical channels with a centre to centre distance of ca. 45 Å may be synthesised from a preparation containing only sodium silicate solution, a surfactant template molecule, water, and some acid. The preparation was optimised initially both for heated and unheated syntheses. The effects of aging in the gel, heating time and stirring were investigated. MCM-41 materials which were stable to calcination were prepared in an ambient temperature synthesis, with stability proportional to aging time in the gel. Heated preparations proved to have highest long range order after 3 days at 100°C in unstirred systems. The effect of pH during synthesis was then investigated. Preparations titrated against 1 M acid to maintain a constant pH during the whole of the synthesis developed much higher long-range order, as determined by the number and intensity of the observed X-ray diffraction peaks. A small counterion effect, dependant upon the type of acid used was noted. The most highly ordered materials were prepared from preparations titrated with sulphuric acid to maintain a pH of 10 during the synthesis. Heated preparations were more ordered than those carried out at ambient temperatures...

Supramolecular structure in full-length Alzheimer's beta-amyloid fibrils: evidence for a parallel beta-sheet organization from solid-state nuclear magnetic resonance.

Balbach, John J; Petkova, Aneta T; Oyler, Nathan A; Antzutkin, Oleg N; Gordon, David J; Meredith, Stephen C; Tycko, Robert
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /08/2002 EN
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We report constraints on the supramolecular structure of amyloid fibrils formed by the 40-residue beta-amyloid peptide associated with Alzheimer's disease (A beta(1-40)) obtained from solid-state nuclear magnetic resonance (NMR) measurements of intermolecular dipole-dipole couplings between (13)C labels at 11 carbon sites in residues 2 through 39. The measurements are carried out under magic-angle spinning conditions, using the constant-time finite-pulse radiofrequency-driven recoupling (fpRFDR-CT) technique. We also present one-dimensional (13)C magic-angle spinning NMR spectra of the labeled A beta(1-40) samples. The fpRFDR-CT data reveal nearest-neighbor intermolecular distances of 4.8 +/- 0.5 A for carbon sites from residues 12 through 39, indicating a parallel alignment of neighboring peptide chains in the predominantly beta-sheet structure of the amyloid fibrils. The one-dimensional NMR spectra indicate structural order at these sites. The fpRFDR-CT data and NMR spectra also indicate structural disorder in the N-terminal segment of A beta(1-40), including the first nine residues. These results place strong constraints on any molecular-level structural model for full-length beta-amyloid fibrils.

Tetra-aqua-(4,4'-bimethyl-2,2'-bipyridine)-nickel(ii) sulfate hydrate: a simple structure with an extremely complex H-bonding scheme.

Suarez, Sebastian; Doctorovich, Fabio; Harvey, Miguel Angel; Baggio, Ricardo Fortunato
Fonte: Wiley-blackwell Publishing, Inc Publicador: Wiley-blackwell Publishing, Inc
Tipo: info:eu-repo/semantics/article; info:ar-repo/semantics/artículo; info:eu-repo/semantics/publishedVersion Formato: application/pdf
ENG
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462.12832%
The title ionic compound, [Ni(C12H12N2)(H2O)4]SO4H2O, is composed of an NiII cation coordinated by a chelating 4,40- dimethyl-2,20-bipyridine ligand via its two N atoms [mean Ni?N = 2.056 (2) A ˚ ] and by four aqua ligands [mean Ni?O = 2.073 (9) A ˚ ], the net charge being balanced by an external sulfate anion. The whole structure is stabilized by a solvent water molecule. Even though the individual constituents are rather featureless, they generate an extremely complex supramolecular structure consisting of a central hydrogenbonded two-dimensional hydrophilic nucleus made up of complex cations, sulfate anions and coordinated and solvent water molecules, with pendant hydrophobic 4,40-dimethyl-2,20- bipyridine ligands which interact laterally with their neighbours via ? interactions. The structure is compared with closely related analogues in the literature.; Fil: Suarez, Sebastian. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias; Argentina;; Fil: Doctorovich, Fabio. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias; Argentina;; Fil: Harvey, M. A.. Universidad Nacional del Comahue;; Fil: Baggio, Ricardo Fortunato. Comisión Nacional de Energía Atómica;

Circular Dichroism and Electron Microscopy Studies In Vitro of 33-mer Gliadin Peptide Revealed Secondary Structure Transition and Supramolecular Organization

Herrera, Maria Georgina; Zamarreño, Fernando; Costabel, Marcelo Daniel; Ritacco, Hernán Alejandro; Hütten, Andreas; Sewald, Norbert; Dodero, Veronica Isabel
Fonte: Wiley Publicador: Wiley
Tipo: info:eu-repo/semantics/article; info:ar-repo/semantics/artículo; info:eu-repo/semantics/publishedVersion Formato: application/pdf
ENG
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Gliadin, a protein present in wheat, rye, and barley, undergoes incomplete enzymatic degradation during digestion, producing an immunogenic 33-mer peptide, LQLQPF(PQPQLPY)3 PQPQPF. The special features of 33-mer that provoke a break in its tolerance leading to gliadin sensitivity and celiac disease remains elusive. Herein, it is reported that 33-mer gliadin peptide was not only able to fold into polyproline II secondary structure but also depending on concentration resulted in conformational transition and self-assembly under aqueous condition, pH 7.0. A 33-mer dimer is presented as one initial possible step in the self-assembling process obtained by partial electrostatics charge distribution calculation and molecular dynamics. In addition, electron microscopy experiments revealed supramolecular organization of 33-mer into colloidal nanospheres. In the presence of 1 mMsodium citrate, 1 mMsodium borate, 1 mMsodium phosphate buffer, 15 mMNaCl, the nanospheres were stabilized, whereas in water, a linear organization and formation of fibrils were observed. It is hypothesized that the self-assembling process could be the result of the combination of hydrophobic effect, intramolecular hydrogen bonding, and electrostatic complementarity due to 33-mer’s high content of proline and glutamine amino acids and its calculated nonionic amphiphilic character. Although...

pH effect on surfactant properties and supramolecular structure of humic substances obtained from sewage sludge composting

RAMÍREZ COUTIÑO,Víctor Angel; TORRES BUSTILLOS,Luis Gilberto; GODÍNEZ MORA TOVAR,Luis Arturo; GUERRA SÁNCHEZ,Ricardo Jaime; RODRÍGUEZ VALADEZ,Francisco Javier
Fonte: Centro de Ciencias de la Atmósfera, UNAM Publicador: Centro de Ciencias de la Atmósfera, UNAM
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/08/2013 EN
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This work evaluates the surfactant properties of humic acids (HA) obtained from sewage sludge composts and the production of value-added products from the residue that is typically a disposal problem. To obtain the HA, aerobically digested sewage sludge was composted with either wooden shavings (HACOMP1) or tezontle (HACOMP2) as a bulking agent. HACOMP1 and HACOMP2 samples were evaluated for their effect on surface tension and compared with a commercial vermicompost sample (HALCOMP). The surface tension values for a concentration of 5000 mg/L, showed a decrease from 72 mN/m to 49 and 51 mN/m for HACOMP1 and HACOMP2 respectively, while the commercial vermicompost diminished only to 65 mN/m. The changes in surface tension could be related to the presence of functional groups, particularly COOH and a predominance of either aliphatic or aromatic chains. This fact was confirmed by FTIR analysis, COOH quantification, and the E4/E6 ratio. These results indicate that lower surface tension is due to the predominance of aliphatic chains, plus lower content of COOH groups and a higher E4/E6 ratio (short size molecule). Also, samples exhibit pH dependence, having a lower surface tension at pH values from 3 to 4. According to size exclusion chromatography (SEC) tests...