RESUMEN
Barrier performance and retrostructural modeling of the macromolecular components demonstrate new design principles for film formulations based on renewable wood hydrolysates. Hardwood hydrolysates, which contain a fair share of lignin coexisting with poly- and oligosaccharides, offer excellent oxygen-barrier performance. A Hansen solubility parameter (HSP) model has been developed to convert the complex hydrolysate structural compositions into relevant matrix oxygen-permeability data allowing a systematic prediction of how the biomass should be formulated to generate an efficient barrier. HSP modeling suggests that the molecular packing ability plays a key role in the barrier performance. The actual size and distribution of free volume holes in the matrices were quantified in the subnanometer scale with Positron annihilation lifetime spectroscopy (PALS) verifying the affinity-driven assembly of macromolecular segments in a densely packed morphology and regulating the diffusion of small permeants through the matrix. The model is general and can be adapted to determine the macromolecular affinities of any hydrolysate biomass based on chemical composition.
Asunto(s)
Betula/química , Materiales Manufacturados , Modelos Químicos , Extractos Vegetales/química , Polisacáridos/química , Madera/química , Algoritmos , Biomasa , Conformación de Carbohidratos , Secuencia de Carbohidratos , Hidrólisis , Lignina/química , Datos de Secuencia Molecular , Oxígeno/química , Permeabilidad , Extractos Vegetales/aislamiento & purificación , Tereftalatos Polietilenos/química , Polisacáridos/aislamiento & purificación , SolubilidadRESUMEN
Biomass is converted to oxygen barriers through a conceptually unconventional approach involving the preservation of the biomass native interactions and macromolecular components and enhancing the effect by created interactions with a co-component. A combined calculation/assessment model is elaborated to understand, quantify, and predict which compositions that provide an intermolecular affinity high enough to mediate the molecular packing needed to create a functioning barrier. The biomass used is a wood hydrolysate, a polysaccharide-rich but not highly refined mixture where a fair amount of the native intermolecular and intramolecular hemicelluloses-lignin interactions are purposely preserved, resulting in barriers with very low oxygen permeabilities (OP) both at 50 and 80% relative humidity and considerably lower OPs than coatings based on the corresponding highly purified spruce hemicellulose, O-acetyl galactoglucomannan (AcGGM). The component interactions and mutual affinities effectively mediate an immobilization of the chain segments in a dense disordered structure, modeled through the Hansen's solubility parameter concept and quantified on the nanolength scale by positron annihilation lifetime spectrum (PALS).
Asunto(s)
Madera , Biomasa , Hidrólisis , Lignina/química , Oxígeno/química , Polisacáridos/química , TermogravimetríaRESUMEN
Polymers with ester linkages in their main chain comprise a family of polymers with immense diversity and versatility. This review deals with the preparation of such polymers from dicarboxylic acid monomers, and the result in terms of properties and applicability. Polyesters alone, and their copolymers with amides, anhydrides, urethanes, imides, ethers or other functional groups, offer countless opportunities to tune the properties of the resulting material within a broad range. Of particular interest is the inherent biodegradability of the ester linkage. Biodegradability is sought after in a wide range of applications, above all in the preparation of environmentally friendly polymers and biomedical materials for temporary surgical use and in drug delivery.
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Poliésteres/química , Animales , Humanos , Poliésteres/síntesis química , Poliésteres/farmacocinéticaRESUMEN
The nonlinear optical quantities, second and third harmonics (beta and gamma), were predicted using a quantitative structure-property relationship (QSPR) approach. Molecular orbital ab initio calculations were applied to generate easily accessible variables to be used in the partial least-squares analysis. Simplified equations are presented that could be used to predict the experimental beta and gamma responses, prior to further investigations of potentially interesting molecules for use in optical materials.
RESUMEN
A special microfiltrated colloidal preparation from fresh Viscum album L. berries was investigated concerning the occurrence and structural features of polymeric carbohydrates. A crude polysaccharide fraction was isolated from lectin-, tannin- and protein-depleted microfiltrates. Further fractionation by exchange chromatography revealed a neutral fraction (average molecular weight 30 kDa) and three acidic fractions (average molecular weights 1300 kDa). Structural analysis of the respective polysaccharide fractions by quantitative and qualitative determination of the sugar composition and linkage analysis indicated that all acidic fractions contained an acidic arabinogalactan with a rhamnose-galactoronic acid backbone and highly branched arabinose-galactose side chains attached by the rhamnose residues to the backbone. The neutral fraction consisted of a neutral arabinogalactan beside minor amounts (about 10%) of a low substituted xyloglucan. Further studies on interaction between the 1340 kDa acidic rhamno-arabinogalactans II and III and mistletoe lectin Viscum album agglutinin I (VAA I) revealed binding capacities between these compounds, while the neutral polymers interacted significantly less with VAA I. Only partial binding of VAA I was observed by incubation of the lectin with polysaccharide II. Similar interactions of polysaccharide fraction III with VAA I was measured in a BIACRORE biosensore system. Using the hemagglutination test, increased agglutination of erythrocytes was observed when mistletoes lectin I and the respective polysaccharide fractions were present together in the assay. All these data indicate clearly strong interaction between VAA I and Viscum polysaccharides.
Asunto(s)
Muérdago/química , Preparaciones de Plantas , Proteínas de Plantas , Plantas Medicinales , Polisacáridos/farmacología , Toxinas Biológicas/farmacología , Adulto , Cromatografía de Gases , Cromatografía Líquida de Alta Presión , Hemaglutinación/efectos de los fármacos , Humanos , Técnicas In Vitro , Lectinas , Masculino , Metilación , Persona de Mediana Edad , Peso Molecular , Extractos Vegetales/química , Lectinas de Plantas , Polisacáridos/química , Proteínas Inactivadoras de Ribosomas , Proteínas Inactivadoras de Ribosomas Tipo 2 , Espectrofotometría Ultravioleta , Toxinas Biológicas/químicaRESUMEN
Biodegradable blends of poly(trimethylene carbonate) (PTMC) and poly(adipic anhydride) (PAA) have been proven to be strong candidates for controlled drug delivery polymers in vitro. We now report on the stability, sterilizability and in vivo local tissue response of these matrices. Blend matrices were sterilized by beta-radiation or ethylene oxide gas treatment, stored at different times and temperatures, and analyzed for changes in physicochemical properties. Moisture uptake at different relative humidities and storage times was determined. Sterilization procedures induced hydrolysis of the matrices. Ethylene oxide gas sterilization had a significantly more marked effect upon the matrix properties than radiation treatment. The onset of degradation was reflected in a decrease of crystallinity and molecular weight along with a change of blend composition. A similar onset of matrix degradation was observed upon storage in air. The physicochemical properties of the blends were well preserved upon storage under argon atmosphere. Biocompatibility of PTMC/PAA implants was assessed in the anterior chamber of rabbits eyes for 1 month. At selected post-operative time points, aqueous humor was analyzed for white blood cells and the corneal thickness was measured. The results suggest good biocompatability of PTMC-rich matrices, whereas fast eroding PAA-rich matrices caused inflammatory responses, due to a burst release of degradation products.
Asunto(s)
Adipatos , Materiales Biocompatibles , Carbonatos , Poliésteres , Polímeros , Animales , Rastreo Diferencial de Calorimetría , Portadores de Fármacos , Espectroscopía de Resonancia Magnética , Microscopía Electrónica de Rastreo , Conejos , Espectroscopía Infrarroja por Transformada de Fourier , EsterilizaciónRESUMEN
BACKGROUND: An acidic arabinogalactan from European mistletoe (Viscum album L, VAL; 1.34 x 10(6) Dalton) was studied in detail because its immunological properties are poorly characterised. MATERIALS AND METHODS: Flow cytometric studies focussed on PS-activated proliferation of human lymphocytes measured via incorporation of bromo-deoxyuridine (BrdU), granulocyte phagocytosis via ingestion of FITC-labelled E.coli, and respiratory burst via oxidation of dihydrorhodamine 123 to rhodamine 123. Cytokines were detected in the cell culture supernatants by ELISA. RESULTS: PS, in contrast to mistletoe lectins (ML), significantly stimulated proliferation of CD4+ T-cells but not CD8+ and CD19+ cells. However, ML influenced PS-mediated stimulation, with a synergistic effect in one and an inhibitory effect in another individual. Furthermore, IFN-gamma release was significantly enhanced by PS, favouring a T-helper cell type-1 cytokine pattern, further IL-6 was significantly stimulated, while granulocyte activity was not affected. CONCLUSIONS: VAL-PS exert yet unknown stimulatory activities, especially on specific CD4+ T-cells which may be influenced by other extract components like the ML. These components may contribute to the anti-tumour effect of VAL.
Asunto(s)
Galactanos/farmacología , Granulocitos/efectos de los fármacos , Linfocitos/efectos de los fármacos , Muérdago/metabolismo , Monocitos/efectos de los fármacos , Extractos Vegetales/farmacología , Preparaciones de Plantas , Proteínas de Plantas , Plantas Medicinales , Polisacáridos/farmacología , Adyuvantes Inmunológicos/farmacología , Bromodesoxiuridina/metabolismo , Citocinas/biosíntesis , Relación Dosis-Respuesta a Droga , Citometría de Flujo , Granulocitos/inmunología , Humanos , Interferón gamma/metabolismo , Interleucina-6/metabolismo , Lectinas/farmacología , Activación de Linfocitos/efectos de los fármacos , Linfocitos/inmunología , Monocitos/inmunología , Fagocitosis/efectos de los fármacos , Lectinas de Plantas , Estallido Respiratorio/efectos de los fármacos , Proteínas Inactivadoras de Ribosomas Tipo 2 , Células TH1/metabolismo , Células Th2/metabolismo , Toxinas Biológicas/farmacologíaRESUMEN
Human calmodulin-like protein (CLP) is closely related to vertebrate calmodulin, yet its unique cell specific expression pattern, overlapping but divergent biochemical properties, and specific target proteins suggest that it is not an isoform of calmodulin. To gain insight into the structural differences that may underlie the difference target specificities and biochemical properties of CLP when compared to calmodulin, we determined the sequential backbone assignment and associated secondary structure of 144 out of the 148 residues of Ca2+-CLP by using multinuclear multidimensional NMR spectroscopy. Despite a very high overall degree of structural similarity between CLP and calmodulin, a number of significant differences were found mainly in the length of alpha-helices and in the central nonhelical flexible region. Interestingly, the regions of greatest primary sequence divergence between CLP and calmodulin in helices III and VIII displayed only minor secondary structure differences. The data suggest that the distinct differences in target specificity and biochemical properties of CLP and calmodulin result from the sum of several minor structural and side-chain changes spread over multiple domains in these proteins.
Asunto(s)
Proteínas de Unión al Calcio/química , Espectroscopía de Resonancia Magnética , Estructura Secundaria de Proteína , Secuencia de Aminoácidos , Calmodulina/química , Humanos , Concentración de Iones de Hidrógeno , Datos de Secuencia Molecular , Alineación de SecuenciaRESUMEN
Mercuric ions are toxic to living organisms because of their strong affinity for cysteine residues in proteins. Some bacteria have developed a resistance mechanism whereby Hg2+ is transported into the cytoplasm and reduced to Hg0. One of the proteins involved in the transport of mercuric ion is the periplasmic binding protein MerP, which can exist both as oxidized (disulfide) and as reduced (dithiol) forms. Only the reduced form with Cys-17 and Cys-14 residues as free thiols is a potent receptor for mercuric ion. In this work the solution structure of the oxidized form of MerP has been determined by multidimensional NMR spectroscopy and compared to the NMR structures of the previously published structures of the reduced and mercury-bound forms of MerP. The mercury-bound and oxidized forms have similar tertiary structures, whereas in the reduced form there is a large rearrangement of the mercuric ion binding loop and the nearby loop comprising residues 38-41. The structural arrangement of the latter loop seems to be important for the stabilization of the surface location of the cysteine-containing loop. In the reduced form at low pH the cysteine-containing loop adopts a conformation similar to what is observed in the oxidized and mercury-bound forms. The oxidized form also differs with respect to the other two forms in the relative positions of some of the alpha-helices and beta-strands. Structural differences between the oxidized and reduced forms may help explain why the reduced form is stable in the periplasm, which is considered to be an oxidizing environment.
Asunto(s)
Proteínas Bacterianas/química , Proteínas Bacterianas/fisiología , Proteínas Portadoras/química , Proteínas Portadoras/fisiología , Escherichia coli/efectos de los fármacos , Mercurio/metabolismo , Mercurio/farmacología , Proteínas , Cristalografía por Rayos X , Farmacorresistencia Microbiana , Escherichia coli/química , Concentración de Iones de Hidrógeno , Modelos Moleculares , Resonancia Magnética Nuclear Biomolecular , Oxidación-Reducción , Oxidorreductasas/metabolismo , Unión Proteica , Estructura Secundaria de Proteína , Soluciones , Propiedades de SuperficieRESUMEN
The microcystin-RR structures are compared with the structures of microcystin-LR in solution as well as in the crystal structure of the complex with protein phosphatase. The gross structures of the two peptides are similar, but with a more accentuated and compact saddle structure for microcystin-RR. The structural differences affect the hydrogen-bond pattern in the peptides and the location of the side chain of N-methyldehydroalanine, both of which are important for the ability of the peptide to form a tight complex with protein phosphatase. These structural differences may contribute to the observed differences in toxicity of microcystin-RR and microcystin-LR.
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Cianobacterias/química , Péptidos Cíclicos/química , Espectroscopía de Resonancia Magnética , Toxinas Marinas , Microcistinas , Modelos Moleculares , Conformación Molecular , Estructura Molecular , Fosfoproteínas Fosfatasas/química , TemperaturaRESUMEN
We have used circular dichroism and 1H- and 15N-NMR spectroscopy to investigate calcium binding to the two EF-hands of human nonerythroid or alphaII-spectrin. Comparison of the 1H-NMR spectra from the peptide containing both EF-hands to the peptides containing the single EF-I and EF-II structures showed that both the structural and calcium-binding properties are significantly different. Further studies of the 121 amino acid peptide containing both EF-hands using circular dichroism and NMR showed that the binding of calcium ions induces conformational changes. To investigate the calcium-binding mechanism, the chemical shifts changes were recorded using multidimensional NMR spectroscopy during calcium titration. A total of 25 titration curves were obtained, each corresponding to the chemical shift changes of individual amino acid residues. The shapes of these titration curves were either hyperbolic or sigmoidal. Using factor analysis, two functions were extracted, one hyperbolic and one sigmoidal, which accounted for nearly all information present in the titration curves. By fitting the two functions to binding curves based on different binding models, we found that the binding mechanism is best described as sequential. Since the sigmoidal type was more pronounced in the titration curves corresponding to residues from the first EF-hand, we suggest that calcium binding to the first EF-hand is described by the sigmoidal function, and that the hyperbolic function describes calcium binding to the second EF-hand. Therefore, is seems likely that the second EF-hand must contain bound calcium before the first EF-hand can bind.
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Calcio/metabolismo , Espectrina/metabolismo , Secuencia de Aminoácidos , Sitios de Unión , Dicroismo Circular , Humanos , Espectroscopía de Resonancia Magnética , Datos de Secuencia Molecular , Fragmentos de Péptidos/química , Fragmentos de Péptidos/metabolismo , Conformación Proteica , Proteínas Recombinantes/metabolismo , Procesamiento de Señales Asistido por Computador , Espectrina/químicaRESUMEN
Phenol hydroxylase from Pseudomonas sp. CF600 is a member of a family of binuclear iron-center-containing multicomponent oxygenases, which catalyzes the conversion of phenol and some of its methyl-substituted derivatives to catechol. In addition to a reductase component which transfers electrons from NADH, optimal turnover of the hydroxylase requires P2, a protein containing 90 amino acids which is readily resolved from the other components. The three-dimensional solution structure of P2 has been solved by 3D heteronuclear NMR spectroscopy. On the basis of 1206 experimental constraints, including 1060 distance constraints obtained from NOEs, 70 phi dihedral angle constraints, 42 psi dihedral angle constraints, and 34 hydrogen bond constraints, a total of 12 converged structures were obtained. The atomic root mean square deviation for the 12 converged structure with respect to the mean coordinates is 2.48 A for the backbone atoms and 3.85 A for all the heavy atoms. This relatively large uncertainty can be ascribed to conformational flexibility and exchange. The molecular structure of P2 is composed of three helices, six antiparallel beta-strands, one beta-hairpin, and some less ordered regions. This is the first structure among the known multicomponent oxygenases. On the basis of the three-dimensional structure of P2, sequence comparisons with similar proteins from other multicomponent oxygenases suggested that all of these proteins may have a conserved structure in the core regions.
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Oxigenasas de Función Mixta/química , Secuencia de Aminoácidos , Catecoles/metabolismo , Espectroscopía de Resonancia Magnética , Oxigenasas de Función Mixta/metabolismo , Modelos Moleculares , Datos de Secuencia Molecular , NAD/metabolismo , Conformación Proteica , Estructura Secundaria de Proteína , Pseudomonas/enzimología , SolucionesRESUMEN
The backbone NMR resonances of human carbonic anhydrase I (HCA I) have been assigned. This protein is one of the largest monomeric proteins assigned so far. The assignment was enabled by a combination of 3D triple-resonance experiments and extensive use of amino acid-specific 15N-labeling. The obtained resonance assignment has been used to evaluate the secondary structure elements present in solution. The solution structure appears to be very similar to the crystal structure, although some differences can be observed. Proton-deuteron exchange experiments have shown that the assignments provide probes that can be used in future studies of HCA I.
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Anhidrasas Carbónicas/química , Secuencia de Aminoácidos , Isótopos de Carbono , Anhidrasas Carbónicas/genética , Deuterio , Humanos , Hidrógeno/química , Espectroscopía de Resonancia Magnética , Datos de Secuencia Molecular , Estructura Molecular , Isótopos de Nitrógeno , Estructura Secundaria de Proteína , Protones , SolucionesRESUMEN
NMR spectroscopy in aqueous and dimethyl sulfoxide/water solutions is used to determine the three-dimensional structures of microcystin-LR, a cyclic cyanobacterial heptapeptide toxin which is a potent inhibitor of type 1 and type 2A protein phosphatases. The conformations of this toxic peptide are studied using a simulated annealing (SA) protocol followed by refined SA calculations in vacuo and free MD simulations in water. Only one conformational family in each solvent is found. The peptide ring has a saddle-shaped form, essentially the same in both solvents. The structural difference observed between the two solution structures is located to the part consisting of Mdha, Ala, and Leu. This peptide segment is not present in nodularin, a cyclic pentapeptide of similar toxicity. The Arg side chain is very flexible, while the side chain of Leu is well defined. The side chain of Adda, essential for toxicity, is constrained in the vicinity of the backbone ring but appears to be flexible in the more remote part.
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Toxinas Bacterianas/química , Cianobacterias/química , Inhibidores Enzimáticos/química , Péptidos Cíclicos/química , Fosfoproteínas Fosfatasas/antagonistas & inhibidores , Simulación por Computador , Dimetilsulfóxido , Microcistinas , Conformación Molecular , Datos de Secuencia Molecular , Reproducibilidad de los Resultados , Soluciones , AguaRESUMEN
Multivariate methods based on principal components (PCA and PLS) have been used to reduce NMR spectral information, to predict NMR parameters of complicated structures, and to relate shift data sets to dependent descriptors of biological significance. Noise reduction and elimination of instrumental artifacts are easily performed on 2D NMR data. Configurational classification of triterpenes and shift predictions in disubstituted benzenes can be obtained using PCA and PLS analysis. Finally, the shift predictions of tripeptides from descriptors of amino acids open the possibility of automatic analysis of multidimensional data of complex structures.
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Técnicas de Química Analítica/métodos , Análisis Multivariante , Secuencia de Aminoácidos , Interpretación Estadística de Datos , Espectroscopía de Resonancia Magnética/métodos , Datos de Secuencia Molecular , Análisis Espectral/métodosRESUMEN
A multivariate data-representation of a portion of the H-NOESY spectrum of an RNA octamer duplex was used to explore the possibility of using Principal Component Analysis and Partial Least Squares Discrimination for pattern recognition. In this case, it is found that the methods can: (i) distinguish slices containing signal from those containing only noise, (ii) locate slices containing overlapping signals, and (iii) in some cases to segregate slices with unique aspects such as those from terminal nucleotides, overlapping signals, purine-H8, pyrimidine-H6 and adenine-H2 containing slices. These properties can easily be included in a scheme to automate spectral analysis. The formulation described here does not distinguish patterns needed to automate sequential assignment of resonances in NOESY spectra of RNA.
Asunto(s)
Espectroscopía de Resonancia Magnética/métodos , ARN , Programas Informáticos , Secuencia de Bases , Simulación por Computador , Modelos Moleculares , Análisis MultivarianteRESUMEN
The 13CO-NMR spectra of carbonylhemoglobins Saint Mandé (beta 102Asn----Tyr), Malmö (beta 97His----Gln), Hôtel Dieu (beta 99Asp----Gly) and Ao have been determined. The positions of the 13CO resonances for hemoglobins Ao, Malmö and Hôtel Dieu were similar indicating similar ligand environments for all. The 13CO resonance for the beta-subunit of Saint Mandé was upfield-shifted compared to the others. This is evidence that structural changes at the beta 102 position directly affect iron-ligand bonding as well as quaternary structure.