Distribution Of Trans Research Articles

Recent developments in altering the fatty acid composition of ruminant-derived foods

There is increasing evidence to indicate that nutrition is an important factor involved in the onset and development of several chronic human diseases including cancer, cardiovascular disease (CVD), type II diabetes and obesity. Clinical studies implicate excessive consumption of medium-chain saturated fatty acids (SFA) and trans-fatty acids (TFA) as risk factors for CVD, and in the aetiology of other chronic conditions. Ruminant-derived foods are significant sources of medium-chain SFA and TFA in the human diet, but also provide high-quality protein, essential micronutrients and several bioactive lipids. Altering the fatty acid composition of ruminant-derived foods offers the opportunity to align the consumption of fatty acids in human populations with public health policies without the need for substantial changes in eating habits. Replacing conserved forages with fresh grass or dietary plant oil and oilseed supplements can be used to lower medium-chain and total SFA content and increase cis-9 18:1, total conjugated linoleic acid (CLA), n-3 and n-6 polyunsaturated fatty acids (PUFA) to a variable extent in ruminant milk. However, inclusion of fish oil or marine algae in the ruminant diet results in marginal enrichment of 20- or 22-carbon PUFA in milk. Studies in growing ruminants have confirmed that the same nutritional strategies improve the balance of n-6/n-3 PUFA, and increase CLA and long-chain n-3 PUFA in ruminant meat, but the potential to lower medium-chain and total SFA is limited. Attempts to alter meat and milk fatty acid composition through changes in the diet fed to ruminants are often accompanied by several-fold increases in TFA concentrations. In extreme cases, the distribution of trans 18:1 and 18:2 isomers in ruminant foods may resemble that of partially hydrogenated plant oils. Changes in milk fat or muscle lipid composition in response to diet are now known to be accompanied by tissue-specific alterations in the expression of one or more lipogenic genes. Breed influences both milk and muscle fat content, although recent studies have confirmed the occurrence of genetic variability in transcript abundance and activity of enzymes involved in lipid synthesis and identified polymorphisms for several key lipogenic genes in lactating and growing cattle. Although nutrition is the major factor influencing the fatty acid composition of ruminant-derived foods, further progress can be expected through the use of genomic or marker-assisted selection to increase the frequency of favourable genotypes and the formulation of diets to exploit this genetic potential.

The dynamic influence of photoisomerization on optical reorientation in absorbing isotropic liquid crystals

The induced transient dichroism and the transient optical Kerr effect (OKE) response of azo-doped isotropic liquid crystals were studied in picosecond time scale. Photoisomerization occurs when the azo-dye molecules are resonantly excited. As a result, a significant enhancement of OKE signal was found in the dye doped liquid crystals with respect to the pure liquid crystals. The enhancement was attributed to the extra torque exerted on liquid crystals after anisotropic orientational distribution of trans and cis isomers were generated. A modified mean field theory model was applied to treat the interactions of trans and cis isomers with liquid crystals. A small-pump enhancement factor of 3.8 was obtained, which is comparable with that of the well-known anthraquinone dye doped LC system.

Triplet-Triplet Energy Transfer in Photocrosslinkable Dendrimers

AbstractThis report describes the synthesis of photocrosslinkable dendrimers with peripheral cinnamamide residues, which exhibit both photoisomerization and photodimerization, and their photochemical and photophysical properties in dilute solutions and polymer matrices. Photoirradiation with 313 nm gave rise to monotonous decrease in the absorbance of trans-cinnamamide at 270 nm as a result of the photochemical reactions of the cinnamamide residues. Spectral analysis revealed the changes in the photoproduct distribution of trans- and cis-photoisomerized and photodimerized cinnamamide groups to be a function of the exposure energy. In dilute solutions, the first-generation dendrimer displayed preferential formation of cis-isomer of the cinnamamide, whereas the photodimerization took place more favorably for the third- and fifth-generation dendrimers. The photochemical behavior was strongly dependent on the dendrimer generation rather than the concentration, probably due to the extent of steric crowding among the cinnamamide residues at terminal positions. Furthermore, the third- and fifth-generation dendrimers showed capturability of a benzophenone derivative into the macromolecules and triplet-triplet energy transfer in the photocrosslinkable dendrimers. This novel phenomenon of the triplet-triplet energy transfer in the dendritic cavities suggests potential applicability to design and fabricate novel optical and electrical molecular devices.

Lycopene degradation and isomerization in tomato dehydration

Lycopene is an important nutrient, since it appears to provide protection against a broad range of epithelial cancers. Tomatoes and tomato products are the major source of lycopene, and are considered to be an important source of carotenoids in the human diet. Biodegradation of lycopene not only affects the attractive color of the final products, but also their nutritive value. The main cause of lycopene degradation in tomato dehydration is isomerization and oxidation. The objectives of this study were to determine the retention of total lycopene and isomerization in different dehydration methods, and to optimize processing technology for the retention of lycopene biological potency in the tomato products. Experiments were carried out to compare the effect of osmotic treatment, vacuum-drying, air-drying and their combination on the retention of lycopene bioactivity. Firstly a skin treatment was applied to the tomatoes, following an osmotic treatment at 25°C in 65°Brix sucrose solution for 4 h, then vacuum-drying at 55°C for 4–8 h, or air-drying at 95°C for 6–10 h. In the fresh tomato samples, lycopene content is 75.5 μg/100 g on dry weight basis. Lycopene occurs in nature primarily in the more stable all- trans form. A significant increase in the cis-isomers with simultaneous decrease in the all- trans isomers can be observed in the dehydrated tomato samples in the different dehydration methods. The cis-isomers increased with temperature and processing time. In the osmotic treatment, the predominating mechanism is isomerization of lycopene. Since the total lycopene content remained essentially constant, but the distribution of trans- and cis-isomers changed. In the air-drying processing, isomerization and oxidation (autoxidation) as two strong factors affected simultaneously the decrease of total lycopene content, distribution of trans-and cis-isomers, and biological potency. A possible explanation of this result is that sugar enters the tomato matrix and strengthen the binding force on lycopene in the tomato matrix. Osmotic solution (sugar) remaining on the surface layer of the tomato prevents oxygen from penetrating and oxidizing lycopene. The osmotic treatment could reduce lycopene losses in comparison with other dehydration methods.

Structure oftrans-4-(trans-4-n-pentylcyclohexyl)cyclohexylcarbonitrile (CCH5) in the isotropic and nematic phases: a computer simulation study

Abstract We have studied the single particle structural properties of the nematogen trans-4-(trans-4-n-pentylcyclohexyl)cyclohexylcarbonitrile (CCH5) by molecular dynamics simulation using realistic atom-atom potentials. On going from the isotropic phase at 390 K to the nematic phase at 350 K, the molecules become significantly longer and thinner, as indicated by the equivalent molecular moment-of-inertia spheroid and the distribution of trans and gauche bonds. This change is only partly accounted for by the lowering of the temperature, there being a significant quenching effect due to the change in the molecular environment. This quenching effect is also apparent in the distribution of molecular shapes seen in molecular width-breadth contour maps. In the nematic phase, at 350K, the distributions of alkyl tail bond orientations with respect to the director show a pronounced odd-even effect, with peaks in the distributions occurring alternately parallel to, and at an angle to, the director.

Distribution of trans and cis 18:1 Fatty Acid Isomers in Chicks Fed Different Fats

The effects of dietary trans isomers of 18:1 (t-18:1) were studied in chicks by feeding purified diets containing soybean oil (SBO) as the control lipid source, saturated fat (SF), hydrogenated soybean oil (HSBO), or spent restaurant grease (SRG) for three weeks. Argentation thin-layer chromatography and gas-liquid chromatography were used to separate trans and cis (c) isomers of 18:1 and to determine the fatty acid composition in chick tissues. Chicks fed HSBO (34% t-18:l of total 18:1) had weight gains similar to those of chicks fed SF but significantly (P<.05) lower gains than those of chicks fed SBO or SRG. No differences were observed in feed conversion ratios (total feed:total gain) across treatments. Trans- 18:l was incorporated into liver, heart, lung, and abdominal fat pad of chicks fed HSBO. Chicks fed HSBO had higher levels of c-16:lω7 and 18:1 and lower levels of linoleate and arachidonate in tissue lipids. Similar changes were observed in liver microsomal fatty acids of chicks fed SRG that was adequate in linoleate, but which contained low levels of t-18:1 (4% of total 18:1). Positional and geometrical isomers of 18:1 appear to impair essential fatty acid metabolism in the chick.

Selective hydrogenation of soybean oil: X. Ultra high pressure and low pressure

AbstractSoybean oil was partially hydrogenated with copper‐chromite catalyst at 170 C and up to 30,000 psig hydrogen pressure. Catalyst activity increased with increase in pressure up to 15,000 psig. The linolenate selectivity (SLn) of the reaction remained essentially unchanged over 50–1000 psig pressure range. A SLn of 5.5 to 5.6 was achieved at 15,000 to 30,000 psig pressure range. This value is somewhat lower than the selectivity at 50–1000 psig, but much higher than that obtained with nickel catalysts. Geometric isomerization increased as pressure increased up to 200 psig; above this pressure, the percenttrans remained the same up to 500 psig.trans Isomer content decreased when the pressure was increased to 30,000 psig. cis,trans Isomerization of linoleate was greater at 1000 psig and 15,000 psig than at 50 psig. At 15,000 psig, part of the linoleate in soybean oil was hydrogenated directly without prior conjugation, whereas at low pressures, all of the double bonds first conjugate prior to hydrogenation. This difference in mechanism might explain the lower selectivities obtained at high pressures. Conjugated diene isomers were found in the products up to 200 psig. Above this pressure conjugated diene was not measurable. No significant differences were found in the double bond distribution oftrans monoenes even though the amount oftrans monoene formed decreased as pressure was increased to 30,000 psig.

ChemInform Abstract: ELECTRON‐DIFFRACTION STUDY OF THE STRUCTURE OF 1,2,7,8‐DIEPOXYOCTANE

The molecular structure of gas‐phase 1,2,7,8‐diepoxyoctane was investigated by electron diffraction to extend a study of straight‐chain diepoxides. The synthesis of diepoxyoctane results in a mixture of two diastereomers, which considerably complicates the conformational problem. The distribution of trans and gauche conformers arising from the rotation around the three central C–C bonds was calculated by assuming a free‐energy difference of 610 cal/mole between the trans and gauche positions. The positions of major nonbonded peaks in the radial distribution then ruled out all but two orientations (A and B) of the epoxy groups. The end‐carbon atoms in conformation A are displaced from the trans position (by about 40°) and the oxygen atom is in a roughly gauche position. In conformation B the positions of the end‐carbon atom and the oxygen atom are approximately interchanged with respect to their positions in conformation A. With the assumption that only one orientation was allowed, the angles defining orientations A and B were optimized and a significantly lower standard deviation was obtained with the former. However, without reoptimizing any of the angles, it was found that models involving combinations of orientations A and B gave as good agreement as the model with A alone. The best of the mixed models coupled the orientation of the end group with the conformation of the central carbon atoms. Since consideration of mixed models essentially doubles the number of parameters to be determined, the present experiment was not able to establish completely the distribution of conformers.

Electron-diffraction study of the structure of 1,2,7,8-diepoxyoctane

The molecular structure of gas-phase 1,2,7,8-diepoxyoctane was investigated by electron diffraction to extend a study of straight-chain diepoxides. The synthesis of diepoxyoctane results in a mixture of two diastereomers, which considerably complicates the conformational problem. The distribution of trans and gauche conformers arising from the rotation around the three central C–C bonds was calculated by assuming a free-energy difference of 610 cal/mole between the trans and gauche positions. The positions of major nonbonded peaks in the radial distribution then ruled out all but two orientations (A and B) of the epoxy groups. The end-carbon atoms in conformation A are displaced from the trans position (by about 40°) and the oxygen atom is in a roughly gauche position. In conformation B the positions of the end-carbon atom and the oxygen atom are approximately interchanged with respect to their positions in conformation A. With the assumption that only one orientation was allowed, the angles defining orientations A and B were optimized and a significantly lower standard deviation was obtained with the former. However, without reoptimizing any of the angles, it was found that models involving combinations of orientations A and B gave as good agreement as the model with A alone. The best of the mixed models coupled the orientation of the end group with the conformation of the central carbon atoms. Since consideration of mixed models essentially doubles the number of parameters to be determined, the present experiment was not able to establish completely the distribution of conformers.

Theory of deformation and strain‐induced crystallization of an elastomeric network polymer

AbstractA new theory of deformation and strain induced crystallization of network polymers has been developed. The effects of lattice vacancies, variation in distribution of trans and gauche bond conformations in stretched amorphous polymers, and the crystallite orientation in the partially crystalline stretched vulcanizate were considered in the evaluation of their partition functions. Stress‐extension ratio relationships were evaluated for the amorphous and semicrystalline polymers. The rise in melting temperature due to strain induced crystallization is discussed. The new theory seems to be in closer agreement with the actual strain‐induced crystallization process than earlier research.