Biosynthesis and isomerization of 11-hydroperoxylinoleates by manganese- and iron-dependent lipoxygenases

Manganese lipoxygenase (Mn-LO) oxygenates linoleic acid (LA) to a mixture of the hydroperoxides—11(S)-hydroperoxy-9Z,12Z-octadecadienoic acid [11(S)-HPODE] and 13(R)-hydroperoxy-9Z,11E-octadecadienoic acid [13(R)-HPODE]- and also catalyzes the conversion of 11(S)-HPODE to 13(R)-HPODE via oxygen-centered (LOO•) and carbon-centered (L•) radicals [Hamberg, M., Su, C., and Oliw, E. (1998) Manganese Lipoxygenase. Discovery of a Bis-allylic Hydroperoxide as Product and Intermediate in a Lipoxygenase Reaction, J. Biol. Chem. 273, 13080–13088]. The aims of the present work were to investigate whether 11-HPODE can also be produced by iron-dependent lipoxygenases and to determine the enzymatic transformations of stereoisomers of 11-HPODE by lipoxygenases. Rice leaf pathogen-inducible lipoxygenase, but not soybean lipoxygenase-1 (sLO-1), generated a low level of 11-HPODE (0.4%) besides its main hydroperoxide, 13(S)-HPODE, on incubation with LA. Steric analysis revealed that 11-HPODE was enriched with respect to the R enantiomer [74% 11(R)]. In agreement with previous results, 11(S)-HPODE incubated with Mn-LO provided 13(R)-HPODE, and the same conversion also took place with the methyl ester of 11(S)-HPODE. 11(R,S)-HPODE was metabolized biphasically in the presence of Mn-LO, i.e., by a rapid phase during which the 11(S)-enantiomer was converted into 13(R)-HPODE and a slow phase during which the 11(R)-enantiomer was converted into 9(R)-HPODE. sLO-1 catalyzed a slow conversion of 11(S)-HPODE into a mixture of 13(R)-HPODE (75%), 9(S)-HPODE (10%), and 13(S)-HPODE (10%), whereas 11(R,S)-HPODE produced a mixture of nearly racemic 13-HPODE (≈70%) and 9-HPODE (≈30%). The results showed that 11-HPODE can also be produced by an iron-dependent LO and suggested that the previously established mechanism of isomerization of 11(S)-HPODE involving suprafacial migration of O₂ is valid also for the isomerizations of 11(R)-HPODE by Mn-LO and of 11(S)-HPODE by sLO-1.     

Effect of Texture and Surface Chemistry of Palm Nut Hull Activated Carbon on the Adsorption of Pigments and Free Fatty Acids from Vegetable Oils

Activated carbons were produced from palm nut hull,which is a waste material of palm oil extraction industries.Activated carbons having various pore size distri...     

Preparation,properties, and laser processing of poly(ɛ-caprolactone)/poly(lactic acid) blends with addition of natural fibers as a potential for printing plates application

In this research, biodegradable blend of poly(ɛ-caprolactone) (PCL) and poly(lactic acid) (PLA) is proposed as a new material for the production of a printing plate for embossing process. Printing plates for embossing consist of raised printing elements and recessed nonimage elements. In production of printing plates, laser technology was used in order to form a relief printing plate. The embossing process is based on the principle of the pressure of the relief printing plate into the printing substrate, which causes the controlled deformation of the substrate and three-dimensional (3D) effect. Coir fibers (CFs) were added as a natural filler to PCL/PLA blends to improve and adjust the properties of produced blends. Scanning electron microscopy micrographs, dynamic mechanical analysis analysis, roughness, and hardness were measured on prepared materials, and 2D and 3D microscopy was conducted on laser engraved printing plates. Results have shown that the addition of CFs improved the mechanical properties of produced materials. DMA results indicate the semicrystalline structure of all prepared blends, and that the addition of CFs raises the elasticity of the composites. Laser engraving showed that it is possible to engrave the produced biodegradable materials and to use it as a material for production of printing plates.     

Influence of trehalose addition on antioxidant activity,colour and texture of orange jelly during storage

The aim of this study was to investigate influence of partial replacement of sucrose with trehalose on phenolics, antioxidant activity, colour and texture of orange jelly during 135 days of storage under the light at room temperature. After preparation, phenol content was 1185.6 and 1050.3 mg GAE kg^?1 in orange jelly and orange jelly with trehalose addition, respectively. Loss of phenols during 135 days of storage in orange jelly was 27.8% in comparison with 9.14% in orange jelly with trehalose addition. Browning index of samples with trehalose addition had lower values than orange jelly after their preparation as well as after storage. Evaluated textural parameters were gel strength, rapture strength, brittleness and adhesiveness. After preparation, both jellies had the same gel strength and adhesiveness. Orange jelly had higher rapture strength and higher value of brittleness than orange jelly with trehalose addition.     

Electro-reduction of diazonium salts on gold: Why do we observe multi-peaks?

Multi-peaks have been observed when reducing diazonium salts by cyclic voltammetry (CV). In order to explain that behavior, we studied the electrochemical properties of a fluorinated diazonium salt that exhibits a strongly passivating behavior on various micro-crystalline gold electrodes. We propose here that each sub-peak observed in CV corresponds to the reduction of the compound on a distinct crystallographic site.     

On Discrete Killing Vector Fields and Patterns on Surfaces

Symmetry is one of the most important properties of a shape, unifying form and function. It encodes semantic information on one hand, and affects the shape's aesthetic value on the other. Symmetry comes in many flavors, amongst the most interesting being intrinsic symmetry, which is defined only in terms of the intrinsic geometry of the shape. Continuous intrinsic symmetries can be represented using infinitesimal rigid transformations, which are given as tangent vector fields on the surface – known as Killing Vector Fields. As exact symmetries are quite rare, especially when considering noisy sampled surfaces, we propose a method for relaxing the exact symmetry constraint to allow for approximate symmetries and approximate Killing Vector Fields, and show how to discretize these concepts for generating such vector fields on a triangulated mesh. We discuss the properties of approximate Killing Vector Fields, and propose an application to utilize them for texture and geometry synthesis.     

Influence Of Trehalose Addition On Instrumental Textural Properties Of Strawberry Pastes

Objective of this study was investigation of influence of trehalose addition (3, 5 and 10%) on instrumental textural properties of evaporated and freeze-dried strawberry pastes. As a control, strawberry paste without addition of trehalose was used. Addition of trehalose had influence on both, hardness and stickiness of the samples, but it is very important to define the amount of trehalose in order to achieve desirable properties. With addition of trehalose hardness of both, evaporated and freeze-dried samples decreased, from 29.89 N to 14.72 N for evaporated samples and from 184.83 N to 44.95 N in freeze-dried samples. Also, from those results it could be seen that freeze-dried samples were much harder than evaporated ones, regardless of trehalose addition. While hardness of samples decreased with addition of trehalose, stickiness increased. Stickiness values were from 0.016 N to 0.0102 N for evaporated samples, and from 0.066 N to 0.018 N for freeze-dried samples. Since evaporated samples had lower values for stickiness they were stickier than freeze-dried ones.     

Thermal and electrical properties of copoly(1,3,4‐oxadiazole‐ethers) containing fluorene groups

A series of aromatic copolyethers containing 1,3,4‐oxadiazole rings and fluorene groups was prepared by nucleophilic substitution polymerization technique of 9,9‐bis(4‐hydroxyphenyl)fluorene, 1 , or of different amounts of 1 and an aromatic bisphenol, such as 4,4′‐isopropylidenediphenol or phenolphthalein, with 2,5‐bis(p‐fluorophenyl)‐1,3,4‐oxadiazole. The polymers were easily soluble in polar solvents like N‐methylpyrrolidone, N,N‐dimethylacetamide, N,N‐dimethylformamide, and chloroform and can be cast from solutions into thin flexible films. They showed high thermal stability, with decomposition temperature being above 425°C. The polymers exhibited a glass‐transition temperature in the range of 195–295°C, with a reasonable interval between glass‐transition and decomposition temperature. Electrical insulating properties of some polymer films were evaluated on the basis of dielectric constant and dielectric loss and their variation with frequency and temperature. The values of the dielectric constant at 10 kHz and 20°C were in the range of 3.16–3.25. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009