Determinación de las reservas de carbono en la biomasa aérea en plantaciones de 8 años de Calyophyllum spruceanum b. en el valle del Aguaytía

Universidad Nacional Agraria La Molina. Facultad de Ciencias Forestales. Departamento Académico de Manejo ForestalEste estudio evaluó el potencial de Calycophyllum spruceanum b. para capturar carbono en plantaciones en dos zonas de la cuenca del río Aguaytía, Provincia de Coronel Portillo, Departamento de Ucayali, Perú. La recolección de información se llevó a cabo en las plantaciones donde el Centro Mundial para la Agroforestería “ICRAF” realiza ensayos de progenie. La metodología consistió en elaborar una ecuación alométrica mediante muestreo destructivo de 30 individuos de Calycophyllum spruceanum b., se midió el diámetro a la altura del pecho (DAP = 1,30m), el diámetro de la base (DB) y la altura total (H) de los árboles para utilizarlas como variables predictivas. La ecuación alométrica que mejor se ajustó para la determinación de la biomasa seca total fue la exponencial de la forma Bt = 0,072*D2,642, con un R2 mayor a 0,98. La investigación siguió con un muestreo estratificado de 35 parcelas temporales de 100 m2, 15 parcelas en el Estrato I o cuenca media y 20 parcelas en el Estrato II o cuenca alta. Se estimó la cantidad de carbono equivalente en la biomasa arbórea, herbácea y en la hojarasca en toneladas métricas por hectárea. Para este estudio el contenido de carbono es una función constante proporcional a la biomasa: 0,45. El carbono total almacenado en plantaciones de Calycophyllum spruceanum b en la cuenca del Aguaytía es de 125,9 tCeq/ha; habiéndose registrado en el Estrato I 84,7 tCeq/ha y en el Estrato II 156,8 tCeq/ha. En el Estrato I, el 74,4% se halló en la biomasa arbórea mientras que el 5,4% y 20,2% en la herbácea y hojarasca respectivamente, en el Estrato II la biomasa arbórea representó el 82,7% mientras que el 2,6% y 14,7% en la herbácea y hojarasca respectivamente.Tesi

Simulation of diffuse scattering in DL-norleucine

The diffraction patterns of DL-norleucine (SR-2-aminohexanoic acid, DL-Nle) crystals may show obvious diffuse scattering, usually described as `streaking', between the Bragg peaks. This phenomenon is obviously related to the non-ideal behaviour of the crystal. The normal interpretation is disorder in the stacking of weakly interacting 2D layers, known also for a number of other racemates of amino acids with linear hydrophobic side chains, as well as 1:1 complexes between different L- and D-enantiomers (quasi-racemates). Presented here is the first attempt to extract the information hidden in the diffuse scattering for this group of compounds by applying Monte Carlo simulations to the site distributions of two polymorphs in a block of 48 × 48 × 48 unit cells (four sites in each unit cell, 442 368 in total). The results demonstrate that it is indeed possible to model the diffuse scattering and relate it to processes expected to take place during phase transitions, characterized by slipping of molecular bilayers (or parts of them) relative to their neighbours. The understanding of the (intermediate) mixed phases in terms of domain size and defect density is consequently brought to a new level

2-Substituted agelasine analogs : synthesis and biological activity, and structure and reactivity of synthetic intermediates

2-Substituted N-methoxy-9-methyl-9H-purin-6-amines were synthesized either from their corresponding 6-chloro-9-methyl-9H-purines or 2-chloro-N-methoxy-9-methyl- 9H-purin-6-amine. Great diversity in the amino/imino tautomeric ratios was observed and calculated based on 1H NMR. The tautomers were identified by 1D and 2D 1H, 13C, and 15N NMR techniques, and showed significant variation both in 13C and 15N shift values. Comparison of the tautomeric ratios with Hammett F values revealed that as the field/inductive withdrawing abilities of the 2-substituent increased, the ratio of amino:imino tautomers was shifted toward the amino tautomer. Computational chemistry exposed the significance of hydrogen bonding between solvent and the compound in question to reach accurate predictions for tautomeric ratios. B3LYP/def2-TZVP density functional theory (DFT) calculations resulted in quantitatively more accurate predictions than when employing the less expensive BP86 functional. N-7-Alkylation of the 2-substituted N-methoxy-9-methyl-9H-purin-6- amines showed that when the field/inductive withdrawing ability of the 2-substituent reached a certain point the reactivity drastically dropped. This correlated with the atomic charges on N-7 calculated using a natural bond orbital (NBO) analysis. Biological screening of the final 2-substituted agelasine analogs indicated that the introduction of a methyl group in the 2-position is advantageous for antimycobacterial and antiprotozoal activity, and that an amino function may improve activity against several cancer cell lines

Ultrasmall Peptides Self-Assemble into Diverse Nanostructures: Morphological Evaluation and Potential Implications

In this study, we perform a morphological evaluation of the diverse nanostructures formed by varying concentration and amino acid sequence of a unique class of ultrasmall self-assembling peptides. We modified these peptides by replacing the aliphatic amino acid at the C-aliphatic terminus with different aromatic amino acids. We tracked the effect of introducing aromatic residues on self-assembly and morphology of resulting nanostructures. Whereas aliphatic peptides formed long, helical fibers that entangle into meshes and entrap >99.9% water, the modified peptides contrastingly formed short, straight fibers with a flat morphology. No helical fibers were observed for the modified peptides. For the aliphatic peptides at low concentrations, different supramolecular assemblies such as hollow nanospheres and membrane blebs were found. Since the ultrasmall peptides are made of simple, aliphatic amino acids, considered to have existed in the primordial soup, study of these supramolecular assemblies could be relevant to understanding chemical evolution leading to the origin of life on Earth. In particular, we propose a variety of potential applications in bioengineering and nanotechnology for the diverse self-assembled nanostructures

Computational approaches to understanding the self-assembly of peptide-based nanostructures

The interest in the self-assembly of peptide-based systems has grown significantly over the past 10–15 years, as more and more applications are shown to benefit from the useful properties of the amino acid based monomers. With the desire to apply the principals of self-assembly to systems within new application areas, there has been an increasing emphasis in understanding the governing forces involved in the self-assembly process, and using this understanding to predict the behaviour of, and design, new materials. To this end, computational approaches have played an increasingly important role over the past decade in helping to decode how small changes in the primary structure can lead to significantly different nanostructures with new function. In this review, a brief survey of the different computational approaches employed in this quest for understanding are provided, along with representative examples of the types of questions that can be answered with each of the different approaches

Altered Backbone and Side-Chain Interactions Result in Route Heterogeneity during the Folding of Interleukin-1b (IL-1b)

Deletion of the b-bulge trigger-loop results in both a switch in the preferred folding route, from the functional loop packing folding route to barrel closure, as well as conversion of the agonist activity of IL-1b into antagonist activity. Conversely, circular permutations of IL-1b conserve the functional folding route as well as the agonist activity. These two extremes in the folding-functional interplay beg the question of whether mutations in IL-1b would result in changes in the populations of heterogeneous folding routes and the signaling activity. A series of topologically equivalent water-mediated b-strand bridging interactions within the pseudosymmetric b-trefoil fold of IL-1b highlight the backbone water interactions that stabilize the secondary and tertiary structure of the protein. Additionally, conserved aromatic residues lining the central cavity appear to be essential for both stability and folding. Here, we probe these protein backbone-water molecule and side chain-side chain interactions and the role they play in the folding mechanism of this geometrically stressed molecule. We used folding simulations with structure-based models, as well as a series of folding kinetic experiments to examine the effects of the F42W core mutation on the folding landscape of IL-1b. This mutation alters water-mediated backbone interactions essential for maintaining the trefoil fold. Our results clearly indicate that this perturbation in the primary structure alters a structural water interaction and consequently modulates the population of folding routes accessed during folding and signaling activity

Tunable Porous Organic Crystals: Structural Scope and Adsorption Properties of Nanoporous Steroidal Ureas

Previous work has shown that certain steroidal bis-(N-phenyl)ureas, derived from cholic acid, form crystals in the P61 space group with unusually wide unidimensional pores. A key feature of the nanoporous steroidal urea (NPSU) structure is that groups at either end of the steroid are directed into the channels and may in principle be altered without disturbing the crystal packing. Herein we report an expanded study of this system, which increases the structural variety of NPSUs and also examines their inclusion properties. Nineteen new NPSU crystal structures are described, to add to the six which were previously reported. The materials show wide variations in channel size, shape, and chemical nature. Minimum pore diameters vary from ∼0 up to 13.1 Å, while some of the interior surfaces are markedly corrugated. Several variants possess functional groups positioned in the channels with potential to interact with guest molecules. Inclusion studies were performed using a relatively accessible tris-(N-phenyl)urea. Solvent removal was possible without crystal degradation, and gas adsorption could be demonstrated. Organic molecules ranging from simple aromatics (e.g., aniline and chlorobenzene) to the much larger squalene (Mw = 411) could be adsorbed from the liquid state, while several dyes were taken up from solutions in ether. Some dyes gave dichroic complexes, implying alignment of the chromophores in the NPSU channels. Notably, these complexes were formed by direct adsorption rather than cocrystallization, emphasizing the unusually robust nature of these organic molecular hosts