Long-chain Polyenoic Fatty Acids Research Articles

The role of defensin fragment in the regulation of fatty acid composition of membrane phospholipids in epithelial-like cells

It is shown that a tetrapeptide fragment of defensin does not alter the phospholipid composition in the membranes of CHO-K1 cells but regulates the fatty acid composition of phosphatidylcholine, phosphatidylethanolamine (PEA), phosphatidylserine (PS), and phosphatidylinositol (PI). Incubation of the cells in the presence of this tetrapeptide resulted in modification of unsaturated fatty acid composition in the studied phospholipids. The content of monoenoic (mainly C18 : 1ω9) and/or dienoic (C18 : 2ω6) fatty acids increased, while the level of polyenoic fatty acids decreased. It was found that in the polyenoic fatty acid group of the PEA, PS and PI molecules, the ω3-/ω6-acid ratio decreased mainly due to the lower content of long-chain ω3-acids with 20 and/or 22 carbonic atoms. The possible role of this peptide in inhibition of the activity of Δ6- and Δ5-desaturases involved in the synthesis of long-chain polyenoic fatty acids, the quantitative alteration of which in phospholipids influences physicochemical parameters in cell membranes, is discussed.

Unique thermal behavior of sphingomyelin species with nonhydroxy and 2-hydroxy very-long-chain (C28-C32) PUFAs

In rat germ cells and spermatozoa, sphingomyelin (SM) contains molecular species with nonhydroxy (n) and 2-hydroxy (h) very-long-chain polyunsaturated fatty acids (V), the most abundant being SMs with (n- and h-) 28:4n-6, 30:5n-6, and 32:5n-6 as acyl chains. The aim of this study was to gain information about their thermotropic behavior and interactions with other lipids. After isolation from rat testis, multilamellar and giant unilamellar vesicles from these SMs were examined using fluorescent probes. Only n-32:5 SM and h-32:5 SM displayed a gel-liquid transition temperature (Tt ∼ 21-22°C), the rest remaining in the liquid state in the 5°C-45°C range. The degree of order was larger in bilayers of any of the h-V SMs than in those of their chain-matched n-V SMs. Both, but n-V SM relatively more than h-V SM, decreased the Tt of dimyristoylphosphatidylcholine as their proportion increased in binary phosphatidylcholine:SM liposomes. In contrast to the established ability of 16:0 SM to form lateral cholesterol/SM-rich ordered domains in ternary dioleoylphosphatidylcholine:cholesterol:SM bilayers, neither n-V SM nor h-V SM showed a tendency to do so. Thus, these SMs are in the fluid state and are not involved in this type of domains in spermatozoa at physiological temperatures. However, this state could be altered at the very low temperatures at which these gametes are usually preserved.

Differentiation-related changes in lipid classes with long-chain and very long-chain polyenoic fatty acids in rat spermatogenic cells

In rat seminiferous tubules (ST), cells that contain polar and neutral lipids with long-chain polyenoic fatty acids (PUFA) and sphingomyelins (SM) and ceramides (Cer) with very long chain (VLC) PUFA of the n-6 series coexist. In this study, pachytene spermatocytes and round spermatids were isolated to determine how these lipids change during spermatogenesis. As the amount per cell of PUFA-rich glycerophospholipids (GPL) decreased with cell size, the 22:5/20:4 ratio increased with cell differentiation. The elovl2 and elovl5 genes, required for 22:5 formation, were expressed (mRNA) in both cell types. Residual bodies- particles with compacted organelles and materials discarded from late spermatids-concentrated cholesterol, 22:5-rich triacylglycerols, and GPL, including plasmalogens and phosphatidylserine. Species of SM and Cer with nonhydroxylated (n-) VLCPUFA (28:4, 30:5, and 32:5) predominated in pachytene spermatocytes, whereas species with the corresponding 2-hydroxy (2-OH) VLCPUFA prevailed in round spermatids. Thus, a dramatic increase in the 2-OH/n-VLCPUFA ratio in SM and Cer was a hallmark of differentiation. A substantial decrease of 2-OH SM occurred between spermatids and mature spermatozoa and 2-OH SM species were collected in residual bodies "en route" to Sertoli cells. Notably, spermatids and spermatozoa gained a significant amount of ceramides devoid of n-VLCPUFA but having 2-OH VLCPUFA as their main fatty acids.

Ceramides with 2-hydroxylated, very long-chain polyenoic fatty acids in rodents: From testis to fertilization-competent spermatozoa

Sphingolipids from rodent testis and spermatozoa are known to contain non-hydroxylated (N-) and 2-hydroxylated (2-OH) very-long-chain polyunsaturated fatty acids (VLCPUFA). In this study, the contribution of species with each type of fatty acids to the total ceramides (Cer) and sphingomyelins (SM) was investigated in rat and mouse testis and in rat spermatozoa. The major VLCPUFA in both lipids of testis were N- and 2-OH versions of 28:4n−6, 30:5n−6 and 32:5n−6 in the rat, and predominantly of 30:5n−6 in the mouse. Absent altogether from rat pre-puberal testes, SM and Cer with N-VLCPUFA appeared 10 days earlier than those with 2-OH VLCPUFA in postnatal development, in association with germ cell differentiation. Conversely, in adult fertile rats that were gradually deprived of germ cells in vivo after treatment with doxorubicin, SM and Cer with N-VLCPUFA decreased earlier than their 2-OH counterparts, and neither was present in aspermatogenic testes. In rat epididymal spermatozoa, the content of Cer prevailed over that of SM and 2-OH VLCPUFA prevailed over N-VLCPUFA in both lipids. In mature gametes, the acrosomal reaction resulted in an almost complete hydrolysis of the species of SM that contain both types of VLCPUFA to produce the corresponding Cer. Ceramides are biosynthetic precursors of SM in the testis, but themselves final products in spermatozoa. VLCPUFA-rich SM and Cer are thus produced in germ cells with the teleological objective of fulfilling their ultimate physiological role in spermatozoa that are apt and ready to fertilize an oocyte.

Sequential depletion of rat testicular lipids with long-chain and very long-chain polyenoic fatty acids after X-ray-induced interruption of spermatogenesis

When a single dose of X-rays is applied to the adult rat testis, stem spermatogonia are damaged, and spermatogenesis is interrupted. Supported by Sertoli cells, spermatogenic cells that endure irradiation complete their differentiation and gradually leave the testis as spermatozoa. In this study, the in vivo changes taking place a number of weeks after irradiation revealed cell-specific features of testicular lipid classes. A linear drop, taking about six weeks, in testis weight, nonlipid materials, free cholesterol, and 22:5n-6-rich glycerophospholipids took place with germ cell depletion. Sphingomyelins and ceramides with nonhydroxy very long-chain polyenoic fatty acids (n-VLCPUFA) disappeared in four weeks, together with the last spermatocytes, whereas species with 2-hydroxy VLCPUFA lasted for six weeks, disappearing with the last spermatids and spermatozoa. The amount per testis of 22:5n-6-rich triacylglycerols, unchanged for four weeks, fell between weeks 4 and 6, associating these lipids with spermatids and their residual bodies, detected as small, bright lipid droplets. In contrast, 22:5n-6-rich species of cholesterol esters and large lipid droplets increased in seminiferous tubules up to week 6, revealing they are Sertoli cell products. At week 30, the lipid and fatty acid profiles reflected the resulting permanent testicular involution. Our data highlight the importance of Sertoli cells in maintaining lipid homeostasis during normal spermatogenesis.

Very Long-chain Polyunsaturated Fatty Acids Are the Major Acyl Groups of Sphingomyelins and Ceramides in the Head of Mammalian Spermatozoa

Very long-chain (C24 to C34) polyunsaturated fatty acids (VLCPUFA) are important constituents of sphingomyelin (SM) and ceramide (Cer) in testicular germ cells. In the present paper we focused on the SM and Cer and their fatty acids in spermatozoa and their main regions, heads and tails. In bull and ram spermatozoa, SM was the third most abundant phospholipid and VLCPUFA were the major acyl groups ( approximately 70%) of SM and Cer. In rat epididymal spermatozoa the SM/Cer ratio was low in the absence of and could be maintained high in the presence of the cation chelator EDTA, added to the medium used for sperm isolation. This fact points to the occurrence of an active divalent cation-dependent sphingomyelinase. Bull and rat sperm had an uneven head-tail distribution of phospholipid, with virtually all the VLCPUFA-rich SM located at the head, the lower SM content in the rat being determined by the lower sperm head/tail size ratio. Most of the SM from bull sperm heads was readily solubilized with 1% Triton X-100 at 4 degrees C. The detergent-soluble SM fraction was richer in VLCPUFA than the nonsoluble fraction and richer in saturated fatty acids. Cer was produced at the expense of SM, thus decreasing severalfold the SM/Cer ratio in rat spermatozoa incubated for 2 h in presence of the sperm-capacitating agents, calcium, bicarbonate, and albumin. The generation of Cer from SM in the sperm head surface may be an early step among the biochemical and biophysical changes known to take place in the spermatozoon in the physiological events preceding fertilization.

Digestion of triacylglycerols containing long-chain polyenoic fatty acids in vitro by colipase-dependent pancreatic lipase and human milk bile salt-stimulated lipase

To assess the role of human milk bile salt-stimulated lipase (BSSL) in the digestion of polyunsaturated ester bonds of triacylglycerols, hydrolysis of docosahexaenoic acid (22:6( n − 3)) ester bonds was compared to that of oleic acid (18:1( n − 9)) or arachidonic acid (20:4( n − 6)) esters. As model substrates, we used rat chylomicrons obtained after feeding human milk fat globules and radiolabeled fatty acids. Radiolabeled chylomicrons were incubated with colipase-dependent pancreatic lipase, with BSSL, or with both enzymes in combination. Both enzymes hydrolyzed 18:1 more efficiently than 22:6 esters. With colipase-dependent lipase there was a large accumulation of 22:6 in diacylglycerol whereas with BSSL it accumulated mainly in monoacylglycerol. Esters containing 20:4 were hydrolyzed by BSSL as efficiently as 18:1 but this fatty acid also accumulated as diacylglycerol with colipase-dependent lipase. At low bile salt concentrations, as found in duodenal contents of newborns, colipase-dependent lipase was virtually unable to hydrolyze esters of 20:4 and 22:6 whereas BSSL hydrolyzed these esters at appreciable rates. Combining the two enzymes gave the most efficient hydrolysis of all fatty acids tested regardless of bile salt concentrations. BSSL may thus have a physiological role in completing duodenal hydrolysis of milk triacylglycerols containing 22:6- or 20:4-esters to free fatty acids and monoacylglycerol.

Lipid remodelling during epididymal maturation of rat spermatozoa. Enrichment in plasmenylcholines containing long-chain polyenoic fatty acids of the n-9 series.

In their transit from the caput to the cauda segments of the epididymis, rat spermatozoa undergo significant modifications in lipid content and composition. The amount of lipid phosphorus per cell decreases, and most lipid classes show specific changes in their constituent fatty acids. A depletion of phosphatidylcholine and phosphatidylethanolamine, concomitant with a virtually unchanged amount of the corresponding plasmalogens, are the major alterations, plasmenylcholine thereby becoming the major phospholipid. Diphosphatidylglycerol, sphingomyelin and the phosphoinositides decrease to a lesser extent or do not change at all, also resulting in relative increases with sperm maturation. Concerning the fatty acids, the proportions of oleate (C18:1, n-9) and linoleate (C18:2, n-6) in most lipids decrease on movement of sperm from caput to cauda, augmenting in turn the proportions of longer-chain (C20 to C24) and more unsaturated fatty acids. Docosapentaenoate (C22:5, n-6) is a major acyl chain present in all lipids at both stages, but uncommon long-chain polyenoic fatty acids of the n-9 series are also present, being almost exclusively found in the choline glycerophospholipids. These fatty acids are found to undergo the most significant changes during sperm maturation. They are minor components of plasmenylcholine in immature spermatozoa, but increase severalfold on maturation, representing more than half of the acyl chains of this major lipid in cells from the cauda. The high concentration of n-9 polyenes in mature sperm plasmenylcholine raises intriguing questions on the possible role epididymal cells may play in providing spermatozoa with such an unusual phospholipid. These plasmenylcholines could contribute to the characteristic lipid domain organization of the mature spermatozoa plasma membrane.

Response of (n-3) and (n-6) Fatty Acids in Piglet Brain, Liver and Plasma to Increasing, but Low, Fish Oil Supplementation of Formula

Addition of fish oils to infant formula provides (n-3) long-chain polyenoic fatty acids (LCP), specifically 22:6(n-3), to infants fed formula rather than human milk. Most fish oils, however, contain high levels of 20:5(n-3) and low (n-6) LCP. These studies determined the brain total, synaptic plasma membrane phosphatidylethanolamine and phosphatidylcholine, and plasma and liver phospholipid fatty acids of piglets fed from birth to 15 d with formula containing (percent fatty acids) 34% 18:2(n-6), 0.8% 18:3(n-3) and 0, 2 or 6 g/L menhaden oil, or sow milk. The brain 22:6(n-3) was higher and 22:4(n-6) lower in piglets fed 6 g/L menhaden oil compared with sow milk. Brain levels of 20:5(n-3) did not increase, or levels of 20:4(n-6) decrease, with increasing dietary (n-3) LCP. A diet concentration-dependent increase in 20:5(n-3) and decrease in 20:4(n-6) (P less than 0.0001) in liver phospholipid showed no evidence of maximum saturation or depletion, respectively, over the range of (n-3) LCP intake studied. The fish oil supplementation was effective in supplying 22:6(n-3) to the developing brain. The accompanying increase in 20:5(n-3) and decrease in 20:4(n-6), important eicosanoid precursors, in plasma and liver phospholipid show the need for caution in the use of fish oils low in (n-6) LCP as a source of (n-3) LCP for infant formula.

Location of double bonds in polyunsaturated fatty acids by gas chromatography-mass spectrometry after 4,4-dimethyloxazoline derivatization

The location of double bonds in polyunsaturated fatty acids is determined by gas chromatography-mass spectrometry after 4,4-dimethyloxazoline (DMOX) derivatization. A procedure for DMOX preparation, starting from fatty acid methyl esters (FAMEs) is proposed. The most interesting properties of these derivatives are presented especially for the analysis of long-chain polyenoic fatty acids. The use of DMOX derivatives in combination with FAMEs can be very useful for the identification of fatty acids in unknown samples.

Effect of a vegetable oil formula rich in linoleic acid on tissue fatty acid accretion in the brain, liver, plasma, and erythrocytes of infant piglets

The effect of feeding sow-milk formula (SMF) or a vegetable-oil infant formula (FF) with minimal n-6 and n-3 long-chain polyenoic fatty acids (LCPs) but high linoleic acid (18:2n-6) and a high ratio of 18:2n-6 to linolenic acid (18:3n-3) on the fatty acids of brain lipid and liver, plasma, and red cell phospholipids was studied in piglets fed from birth for 5, 10, 15, or 25 d. Compared with SMF, FF reduced the concentrations of 18:1 and n-3 LCPs, especially 22:6n-3, in all tissues and increased 22:4n-6 in brain, liver, plasma, and red cell phosphatidylethanolamine. FF also increased 22:5n-6 in brain lipid, liver, and plasma but not in red cell phospholipids. Thus, changes in tissues capable of in situ desaturation were not completely reflected in the red cell phospholipids. The increased liver and brain n-6 LCP accretion in the FF piglets may suggest competent desaturation and possible inhibition of n-3 desaturation and/or acylation by dietary n-6 fatty acids.

Quantitative characterization of microbial biomass and community structure in subsurface material: a prokaryotic consortium responsive to organic contamination

Application of quantitative methods for microbial biomass, community structure, and nutritional status to the subsurface samples collected with careful attention to contamination reveals the presence of a group of microbes. The microbiota is sparse by several measures of biomass compared with that present in surface sediments and soils. The community structure, as characterized by the patterns of ester-linked fatty acids from the phospholipids, shows an absence of long-chain polyenoic fatty acids typical of microeukaryotes and high proportions of fatty acids typical of bacteria. Subsurface samples contain a higher proportion of glycerol teichoic acids than surface samples. Microbes in uncontaminated subsurface sediments show nutritional stress as evidenced by high levels of poly-β-hydroxybutyrate and extracellular polysaccharides. The proportions of ester-linked phospholipid fatty acids show distinctive differences between surface and subsurface, between subsurface sandy clay and limestone, and between two sites of subsurface sandy clay as shown using stepwise discriminant analysis. Contamination increased the microbial biomass, shifted the community to a more gram-negative bacterial consortium, and induced growth as evidenced by phospholipid fatty acid biosynthesis.

Improved graft patency associated with altered platelet function induced by marine fatty acids in dogs

Female mongrel dogs fed a marine fish diet rich in long-chain polyenoic fatty acids had improved patency of small-diameter arterial prosthetic grafts as compared to controls. Also, in vivo platelet function as measured by bleeding times was significantly prolonged. Eicosapentaenoic acid, not found in the serum of control animals, was present in relatively high concentrations in both the serum and a platelet-rich fraction of the marine oil-fed group. Eicosapentaenoic acid, unlike arachidonic acid, does not induce platelet aggregation and this phenomonon may account for the altered platelet function demonstrated in our animals and hence the improved graft patency. These data lend further support to the role of platelets in determining the patency of vascular grafts.

Reduced triglyceride formation from long-chain polyenoic fatty acids in rat hepatocytes

The mechanism for the marked reduction in hepatic triglyceride secretion when rats are fed fish oils was explored in studies with isolated rat hepatocytes. Hepatocytes obtained from Sprague-Dawley rats fed either chow or fish oil or safflower oil were incubated in the presence of [ 3H]-glycerol to estimate triglyceride formation. In some experiments, various fatty acids, complexed to albumin, were added to the incubations. Similar experiments were carried out with hepatocytes from a genetic strain of hypertriglyceridemic, obese rats. In the absence of added fatty acid, hepatocytes from fish oil-fed rats produced and secreted substantially less triglyceride than cells from safflower oil-fed rats. However, the addition of 2 mmol/L Na oleate stimulated triglyceride formation similarly in both types of hepatocytes. When hepatocytes from chow fed rats were incubated with fatty acids of increasing chain length and unsaturation (oleate, linolenate, arachidonate, eicosapentaenoate, and docosahexaenoate), the latter two, which characterize the fish oil used, almost totally suppressed triglyceride formation. Coincubation with oleate partly reversed this effect. Hepatocytes from the hypertriglyceridemic rats synthesized significantly more triglyceride than hepatocytes from normal rats; however triglyceride formation was markedly reduced also in this strain of rat by feeding fish oil or by adding docosahexaenoate to hepatocytes in vitro. These studies confirm previous conclusions with perfused livers from fish oil-fed rats that showed diminished triglyceride production and secretion. These findings suggest that diversion of polyenoic acids from pathways of esterification is a major factor in the triglyceride lowering effect of fish oils. The new data also establish that both major polyenoic acids are equally inhibitory, that the effect occurs rapidly and being readily reversed with an alternative substrate such as oleic acid, does not represent hepatotoxicity.

Lipid composition of an obligately anaerobic fungus Neocallimastix frontalis isolated from a bovine rumen

The lipid composition of an obligately anaerobic bovine rumen fungus Neocallimastix frontalis, belonging to the Neo-callimasticaceae of the Chytridiomycetes, has been investigated. It consisted of 44% neutral lipids (triacylglycerol, fatty acid, and sterols) and 56% polar lipids. The fatty acid composition of this unusual fungus differed markedly from that of other members of Chytridiomycetes by the absence of long-chain polyenoic fatty acids and by the presence of a large proportion (48%) of a series of cis-monoenoic fatty acids between 14:1 and 24:1. The absence of polyunsaturated fatty acids is explained by the anaerobic life style of this organism. However, the formation of the large proportions of monoenoic fatty acids under anaerobic conditions constitutes a major difference which cannot be explained by known pathways of fatty acid biosynthesis in fungi. This result indicates that N. frontalis differs from other fungi in possessing an anaerobic pathway for monoenoic fatty acid biosynthesis.

Metabolism of arachidonate in rat testis: characterization of 26-30 carbon polyenoic acids.

Fatty acid methyl esters of long-chain polyenoic fatty acids (LCPA) from rat testis injected with [1-14C] arachidonate were analyzed and separated by reversed-phase high performance liquid chromatography (RP-HPLC). Earlier, all previously identified LCPA were prepared in high purity along with 4 previously unidentified fatty acids, which were further characterized by capillary gas chromatography (GC), catalytic hydrogenation and alkaline isomerization. Unidentified fatty acids proved to be 26:4, 26:5, 28:5 and 30:5. All of these LCPA incorporated 14C from arachidonate (20:4) to specific activities that were comparable to that of 20:4 and previously identified metabolites of 20:4 and much greater than specific activities of 18:1n-9 or 22:6n-3. LCPA were analyzed on a capillary GC system capable of resolving known cis-trans and positional isomers of the n-3, n-6, n-7 and n-9 families of unsaturated fatty acids. Log plots of isothermal retention times and normal plots of temperature programmed retention times were linear (r = 0.999) in carbon number when values for known and previously unidentified LCPA of 4 or 5 double bonds, respectively, were coplotted. Thus, the newly identified fatty acids belong to the n-6 family of fatty acids synthesized from arachidonic acid.

Spatial Distribution of Biochemical Parameters Indicating Biomass and Community Composition of Microbial Assemblies In Estuarine Mud Flat Sediments

The spatial distribution of communities was examined in estuarine mud flat sediments by the biochemical analysis of the lipids and lipid components extracted from the sediments. Total phospholipid was used as a measure of total biomass, and fatty acids were used as indicators of community composition. Comparisons were made among 2- by 2-m (location) and 0.2- by 0.2-m (cluster) sampling plots by using a nested analysis of variance to design an optimal sampling strategy to define the microbial content of a large, relatively homogenous area. At two of the three stations, a 2- by 2-m plot was representative of the station, but 0.2- by 0.2-m areas were in no case representative of the station. The biomass measured by the extractable phospholipid and the total lipid palmitic acid showed excellent correlation with the fatty acid "signatures" characteristic of bacteria, but showed a lower correlation with the long-chain polyenoic fatty acids characteristic of the microfauna.

Extrauterine fatty acid accretion in infant brain: implications for fatty acid requirements

Total fatty acid content of infant brain was determined to assess minimal fatty acid requirements for synthesis of structural lipids in brain tissue during the first 13 weeks of life. Fatty acid accretion rates were determined by regression analysis of tissue fat components at varying postnatal ages. Quantitative fatty acid analysis indicated that postnatal accretion of long-chain polyenoic fatty acids in cerebellum, frontal and occipital brain lobes initially appeared to lag behind the rate of increase in brain weight and brain fat content. After a 4-week period total long-chain fatty acids increased at a rate similar to the increase in brain weight. Accretion of individual fatty acids in cerebellum also reflected changes in tissue total fatty acid content. These developmental changes in fatty acid components of whole brain and cerebellum are quantitatively relevant to estimation of the minimal extrauterine fatty acid requirements of the human neonate.

Interaction of mycobacterial polymethylpolysaccharides with paranaric acid and palmitoyl-coenzyme A: Structural specificity and monomeric dissociation constants

The long-chain polyenoic fatty acids alpha- and beta-paranaric acid form complexes with the 6-O-methylglucose polysaccharide from Mycobacterium smegmatis as demonstrated by an enhanced fluorescence emission of the paranaric acid. This interaction is eliminated by digestion of the methylglucose polysaccharide with alpha-amylase and glucoamylase, which removes four hexose units from the nonreducing end of the chain. Titration of the methylglucose polysaccharide with either paranaric acid isomer suggests formation of a 1:1 complex with a dissociation constant (K(d)) of 0.4 muM. The fluorescence emission of this complex is quenched by palmitoyl-CoA, which indicates that the paranaric acid can be displaced by the acoyl-CoA, a conclusion confirmed by gel filtration. The presumed polysaccharide/palmitoyl-CoA complex has a K(d) of about 0.1 muM. Acoyl-CoA derivatives with shorter fatty acid chains and free palmitic acid complete less effectively, indicating that they form weaker complexes with the polysaccharide. The methylmannose polysaccharides with 12 or 13 sugar units also complex paranaric acid strongly (K(d) approximately 0.4 muM), whereas the isomer with 11 sugar units complexes weakly.The methylglucose polysaccharide has been coupled to L-tryptophan methyl ester. The fluorescence emission spectrum of the attached tryptophan group is shifted to a shorter wavelength relative to N-acetyl-L-tryptophan methyl ester, and this effect is enhanced in the corresponding derivative made with the amylase-digested polysaccharide. The circular dichroism spectrum of the polysaccharide-tryptophan derivative shows three bands with negative ellipticity, in the 270-300 nm region, not observed in the amylase-digested derivative. These results imply that the tryptophan is in a more structured environment in the former than in the latter derivative. alpha-Paranaric acid binds to the polysaccharide-tryptophan conjugate and shows an enhanced fluorescence emission with partial quenching of the tryptophan fluorescence emission, suggestive of Förster energy transfer from tryptophan to paranaric acid.

The availability of long-chain polyenoic fatty acids for brain development in the rat.

The availability of long-chain polyenoic fatty acids for brain development in the rat.