Female Mice are Resistant to Fabp1 Gene Ablation-Induced Alterations in Brain Endocannabinoid Levels

Although liver fatty acid binding protein (FABP1, L‐FABP) is not detectable in the brain, Fabp1 gene ablation (LKO) markedly increases endocannabinoids (EC) in brains of male mice. Since the brain EC system of females differs significantly from that of males, it was important to determine if LKO differently impacted the brain EC system. LKO did not alter brain levels of arachidonic acid (ARA)‐containing EC, i.e. arachidonoylethanolamide (AEA) and 2‐arachidonoylglycerol (2‐AG), but decreased non‐ARA‐containing N‐acylethanolamides (OEA, PEA) and 2‐oleoylglycerol (2‐OG) that potentiate the actions of AEA and 2‐AG. These changes in brain potentiating EC levels were not associated with: (1) a net decrease in levels of brain membrane proteins associated with fatty acid uptake and EC synthesis; (2) a net increase in brain protein levels of cytosolic EC chaperones and enzymes in EC degradation; or (3) increased brain protein levels of EC receptors (CB1, TRVP1). Instead, the reduced or opposite responsiveness of female brain EC levels to loss of FABP1 (LKO) correlated with intrinsically lower FABP1 level in livers of WT females than males. These data show that female mouse brain endocannabinoid levels were unchanged (AEA, 2‐AG) or decreased (OEA, PEA, 2‐OG) by complete loss of FABP1 (LKO).     

Sterol Carrier Protein-2/Sterol Carrier Protein-x/Fatty Acid Binding Protein-1 Ablation Impacts Response of Brain Endocannabinoid to High-Fat Diet

Brain endocannabinoids (EC) such as arachidonoylethanolamine (AEA) and 2-arachidonoylglycerol (2-AG) primarily originate from serum arachidonic acid (ARA), whose level is regulated in part by a cytosolic ARA-binding protein, that is, liver fatty acid binding protein-1 (FABP1), not expressed in the brain. Ablation of the Fabp1 gene (LKO) increases brain AEA and 2-AG by decreasing hepatic uptake of ARA to increase serum ARA, thereby increasing ARA availability for uptake by the brain. The brain also expresses sterol carrier protein-2 (SCP-2), which is also a cytosolic ARA-binding protein. To further resolve the role of SCP-2 independent of FABP1, mice ablated in the Scp-2/Scp-x gene (DKO) were crossed with mice ablated in the Fabp1 gene (LKO) mice to generate triple knock out (TKO) mice. TKO impaired the ability of LKO to increase brain AEA and 2-AG. While a high-fat diet (HFD) alone increased brain AEA, TKO impaired this effect. Overall, these TKO-induced blocks were not attributable to altered expression of brain proteins in ARA uptake, AEA/2-AG synthesis, or AEA/2-AG degrading enzymes. Instead, TKO reduced serum levels of free ARA and/or total ARA and thereby decreased ARA availability for uptake to the brain and downstream synthesis of AEA and 2-AG therein. In summary, Scp-2/Scp-x gene ablation in Fabp1 null (LKO) mice antagonized the impact of LKO and HFD on brain ARA and, subsequently, EC levels. Thus, both FABP1 and SCP-2 participate in regulating the EC system in the brain.     

Human Liver Fatty Acid Binding Protein‐1 T94A Variant,Nonalcohol Fatty Liver Disease,and Hepatic Endocannabinoid System

Hepatic endocannabinoids (EC) and their major binding/“chaperone” protein (i.e., liver fatty acid binding protein‐1 [FABP1]) are associated with development of nonalcoholic fatty liver (NAFLD) in animal models and humans. Since expression of the highly prevalent human FABP1 T94A variant induces serum lipid accumulation, it is important to determine its impact on hepatic lipid accumulation and the EC system. This issue was addressed in livers from human subjects expressing only wild‐type (WT) FABP1 T94T (TT genotype) or T94A variant (TC or CC genotype). WT FABP1 males had lower total lipids (both neutral cholesteryl esters, triacylglycerols) and phospholipids than females. WT FABP1 males' lower lipids correlated with lower levels of the N‐acylethanolamide DHEA and 2‐monoacylglycerols (2‐MAG) (2‐OG, 2‐PG). T94A expression in males increased the hepatic total lipids (triacylglycerol, cholesteryl ester), which is consistent with their higher level of CB1‐potentiating 2‐OG and lower antagonistic EPEA. In contrast, in females, T94A expression did not alter the total lipids, neutral lipids, or phospholipids, which is attributable to the higher cannabinoid receptor‐1 (CB1) agonist arachidonoylethanolamide (AEA) and its CB1‐potentiator OEA being largely offset by reduced potentiating 2‐OG and increased antagonistic EPEA. Taken together, these findings indicate that T94A‐induced alterations in the hepatic EC system contribute at least in part to the hepatic accumulation of lipids associated with NAFLD, especially in males.     

Ligand Binding Promiscuity of Human Liver Fatty Acid Binding Protein: Structural and Dynamic Insights from an Interaction Study with Glycocholate and Oleate

Human liver fatty acid binding protein (hL‐FABP) has been reported to act as an intracellular shuttle of lipid molecules, thus playing a central role in systemic metabolic homeostasis. The involvement of hL‐FABP in the transport of bile salts has been postulated but scarcely investigated. Here we describe a thorough NMR investigation of glycocholate (GCA) binding to hL‐FABP. The protein molecule bound a single molecule of GCA, in contrast to the 1:2 stoichiometry observed with fatty acids. GCA was found to occupy the large internal cavity of hL‐FABP, without requiring major conformational rearrangement of the protein backbone; rather, this led to increased stability, similar to that estimated for the hL‐FABP:oleate complex. Fast‐timescale dynamics appeared not to be significantly perturbed in the presence of ligands. Slow motions (unlike for other proteins of the family) were retained or enhanced upon binding, consistent with a requirement for structural plasticity for promiscuous recognition.     

Interplay Between n-3 and n-6 Long-Chain Polyunsaturated Fatty Acids and the Endocannabinoid System in Brain Protection and Repair

The brain is enriched in arachidonic acid (ARA) and docosahexaenoic acid (DHA), long‐chain polyunsaturated fatty acids (LCPUFAs) of the n‐6 and n‐3 series, respectively. Both are essential for optimal brain development and function. Dietary enrichment with DHA and other long‐chain n‐3 PUFA, such as eicosapentaenoic acid (EPA), has shown beneficial effects on learning and memory, neuroinflammatory processes, and synaptic plasticity and neurogenesis. ARA, DHA and EPA are precursors to a diverse repertoire of bioactive lipid mediators, including endocannabinoids. The endocannabinoid system comprises cannabinoid receptors, their endogenous ligands, the endocannabinoids, and their biosynthetic and degradation enzymes. Anandamide (AEA) and 2‐arachidonoylglycerol (2‐AG) are the most widely studied endocannabinoids and are both derived from phospholipid‐bound ARA. The endocannabinoid system also has well‐established roles in neuroinflammation, synaptic plasticity and neurogenesis, suggesting an overlap in the neuroprotective effects observed with these different classes of lipids. Indeed, growing evidence suggests a complex interplay between n‐3 and n‐6 LCPUFA and the endocannabinoid system. For example, long‐term DHA and EPA supplementation reduces AEA and 2‐AG levels, with reciprocal increases in levels of the analogous endocannabinoid‐like DHA and EPA‐derived molecules. This review summarises current evidence of this interplay and discusses the therapeutic potential for brain protection and repair.     

High Glucose and Liver Fatty Acid Binding Protein Gene Ablation Differentially Impact Whole Body and Liver Phenotype in High-Fat Pair-Fed Mice

Ad libitum-fed diets high in fat and carbohydrate (especially fructose) induce weight gain, obesity, and nonalcoholic fatty liver disease (NAFLD) in humans and animal models. However, interpretation is complicated since ad libitum feeding of such diets induces hyperphagia and upregulates expression of liver fatty acid binding protein (L-FABP)—a protein intimately involved in fatty acid and glucose regulation of lipid metabolism. Wild-type (WT) and L-fabp gene ablated (LKO) mice were pair-fed either high-fat diet (HFD) or high-fat/high-glucose diet (HFGD) wherein total carbohydrate was maintained constant but the proportion of glucose was increased at the expense of fructose. In LKO mice, the pair-fed HFD increased body weight and lean tissue mass (LTM) but had no effect on fat tissue mass (FTM) or hepatic fatty vacuolation as compared to pair-fed WT counterparts. These LKO mice exhibited upregulation of hepatic proteins in fatty acid uptake and cytosolic transport (caveolin and sterol carrier protein-2), but lower hepatic fatty acid oxidation (decreased serum β-hydroxybutyrate). LKO mice pair-fed HFGD also exhibited increased body weight; however, these mice had increased FTM, not LTM, and increased hepatic fatty vacuolation as compared to pair-fed WT counterparts. These LKO mice also exhibited upregulation of hepatic proteins in fatty acid uptake and cytosolic transport (caveolin and acyl-CoA binding protein, but not sterol carrier protein-2), but there was no change in hepatic fatty acid oxidation (serum β-hydroxybutyrate) as compared to pair-fed WT counterparts.     

Design,Synthesis, and Evaluation of an 18F‐Labeled Radiotracer Based on Celecoxib–NBD for Positron Emission Tomography (PET) Imaging of Cyclooxygenase‐2 (COX‐2)

A series of novel fluorine‐containing cyclooxygenase‐2 (COX‐2) inhibitors was designed and synthesized based on the previously reported fluorescent COX‐2 imaging agent celecoxib–NBD ( 3 ; NBD=7‐nitrobenzofurazan). In vitro COX‐1/COX‐2 inhibitory data show that N‐(4‐fluorobenzyl)‐4‐(5‐p‐tolyl‐3‐trifluoromethylpyrazol‐1‐yl)benzenesulfonamide ( 5 ; IC₅₀=0.36 μM , SI>277) and N‐fluoromethyl‐4‐(5‐p‐tolyl‐3‐trifluoromethylpyrazol‐1‐yl)benzenesulfonamide ( 6 ; IC₅₀=0.24 μM , SI>416) are potent and selective COX‐2 inhibitors. Compound 5 was selected for radiolabeling with the short‐lived positron emitter fluorine‐18 (¹⁸F) and evaluated as a positron emission tomography (PET) imaging agent. Radiotracer [¹⁸F] 5 was analyzed in vitro and in vivo using human colorectal cancer model HCA‐7. Although radiotracer uptake into COX‐2‐expressing HCA‐7 cells was high, no evidence for COX‐2‐specific binding was found. Radiotracer uptake into HCA‐7 tumors in vivo was low and similar to that of muscle, used as reference tissue.     

NBD‐Based Green Fluorescent Ligands for Typing of Thymine‐Related SNPs by Using an Abasic Site‐Containing Probe DNA

The binding behavior of green fluorescent ligands, derivatives of 7‐nitrobenzo‐2‐oxa‐1,3‐diazole (NBD), with DNA duplexes containing an abasic (AP) site is studied by thermal denaturation and fluorescence experiments. Among NBD derivatives, N¹‐(7‐nitrobenzo[c][1,2,5]oxadiazol‐4‐yl)propane‐1,3‐diamine (NBD‐NH₂) is found to bind selectively to the thymine base opposite an AP site in a DNA duplex with a binding affinity of 1.52×10⁶ M ^?1. From molecular modeling studies, it is suggested that the NBD moiety binds to thymine at the AP site and a protonated amino group tethered to the NBD moiety interacts with the guanine base flanking the AP site. Green fluorescent NBD‐NH₂ is successfully applied for simultaneous G>T genotyping of PCR amplification products in a single cuvette in combination with a blue fluorescent ligand, 2‐amino‐6,7‐dimethyl‐4‐hydroxypteridine (diMe‐pteridine).     

Making Epothilones Fluoresce: Design,Synthesis, and Biological Characterization of a Fluorescent N12‐Aza‐Epothilone (Azathilone)

A green fluorescent 12‐aza‐epothilone (azathilone) derivative has been prepared through the attachment of the 4‐nitro‐2,1,3‐benzoxadiazole (NBD) fluorophore to the 12‐nitrogen atom of the azamacrolide core structure. While less potent than natural epothilones or different N12‐acylated azathilone derivatives, NBD‐azathilone ( 3 ) promotes tubulin assembly, inhibits cancer cell proliferation in vitro and arrests the cell cycle at the G2/M transition. Most significantly, the binding of 3 to cellular microtubules (MTs) could be directly visualized by confocal fluorescence microscopy. Based on competition binding experiments with laulimalide‐stabilized MTs in vitro, the N12‐Boc substituted azathilone 1 , Epo A, and NBD‐azathilone ( 3 ) all interact with the same tubulin‐binding site. Computational studies provided a structural model of the complexes between β‐tubulin and 1 or 3 , respectively, in which the NBD moiety of 3 or the BOC moiety of 1 directly and specifically contribute to MT binding. Collectively, these data demonstrate that the cellular effects of 3 and, by inference, also of other azathilones are the result of their interactions with the cellular MT network.     

Elevated Levels of Endocannabinoids in Chronic Hepatitis C May Modulate Cellular Immune Response and Hepatic Stellate Cell Activation

The endocannabinoid (EC) system is implicated in many chronic liver diseases, including hepatitis C viral (HCV) infection. Cannabis consumption is associated with fibrosis progression in patients with chronic hepatitis C (CHC), however, the role of ECs in the development of CHC has never been explored. To study this question, anandamide (AEA) and 2-arachidonoyl glycerol (2-AG) were quantified in samples of HCV patients and healthy controls by gas and liquid chromatography mass spectrometry. Fatty acid amide hydrolase (FAAH) and monoaclyglycerol lipase (MAGL) activity was assessed by [³H]AEA and [³H]2-AG hydrolysis, respectively. Gene expression and cytokine release were assayed by TaqMan PCR and ELISpot, respectively. AEA and 2-AG levels were increased in plasma of HCV patients, but not in liver tissues. Hepatic FAAH and MAGL activity was not changed. In peripheral blood mononuclear cells (PBMC), ECs inhibited IFN-γ, TNF-α, and IL-2 secretion. Inhibition of IL-2 by endogenous AEA was stronger in PBMC from HCV patients. In hepatocytes, 2-AG induced the expression of IL-6, -17A, -32 and COX-2, and enhanced activation of hepatic stellate cells (HSC) co-cultivated with PBMC from subjects with CHC. In conclusion, ECs are increased in plasma of patients with CHC and might reveal immunosuppressive and profibrogenic effects.     

Liver Fatty Acid Binding Protein Gene-Ablation Exacerbates Weight Gain in High-Fat Fed Female Mice

Loss of liver fatty acid binding protein (L‐FABP) decreases long chain fatty acid uptake and oxidation in primary hepatocytes and in vivo. On this basis, L‐FABP gene ablation would potentiate high‐fat diet‐induced weight gain and weight gain/energy intake. While this was indeed the case when L‐FABP null (?/?) mice on the C57BL/6NCr background were pair‐fed a high‐fat diet, whether this would also be observed under high‐fat diet fed ad libitum was not known. Therefore, this possibility was examined in female L‐FABP (?/?) mice on the same background. L‐FABP (?/?) mice consumed equal amounts of defined high‐fat or isocaloric control diets fed ad libitum. However, on the ad libitum‐fed high‐fat diet the L‐FABP (?/?) mice exhibited: (1) decreased hepatic long chain fatty acid (LCFA) β‐oxidation as indicated by lower serum β‐hydroxybutyrate level; (2) decreased hepatic protein levels of key enzymes mitochondrial (rate limiting carnitine palmitoyl acyltransferase A1, CPT1A; HMG‐CoA synthase) and peroxisomal (acyl CoA oxidase 1, ACOX1) LCFA β‐oxidation; (3) increased fat tissue mass (FTM) and FTM/energy intake to the greatest extent; and (4) exacerbated body weight gain, weight gain/energy intake, liver weight, and liver weight/body weight to the greatest extent. Taken together, these findings showed that L‐FABP gene‐ablation exacerbated diet‐induced weight gain and fat tissue mass gain in mice fed high‐fat diet ad libitum—consistent with the known biochemistry and cell biology of L‐FABP.     

Intestinal and liver fatty acid binding proteins differentially affect fatty acid uptake and esterification in L-cells

Differential effects of intestinal (I-FABP) or liver (L-FABP) fatty acid binding proteins on fatty acid uptake and esterification were examined using transfected mouse L-cell fibroblasts. L-FABP, but not I-FABP, expression increased the initial rate and extent ofcis-parinaric acid uptake by 50 and 29%, respectively, compared to control cells. I-FABP and L-FABP expression preferentially increased [³H]-oleic acid incorporation into triacylglycerols by 5.5-fold and 3.8-fold, respectively. While both L-FABP and I-FABP increasedesterification of [³H]-oleic acid into ethanolamine glycerophospholipids, these proteins had opposite effect on esterification into choline glycerophospholipids. These data show for the first time that distinct FABP differentially affect both fatty acid uptake and intracellular esterification.     

Effect of <Emphasis Type="Italic">Fabp1/Scp</Emphasis>-<Emphasis Type="Italic">2/Scp</Emphasis>-<Emphasis Type="Italic">x</Emphasis> Ablation on Whole Body and Hepatic Phenotype of Phytol-Fed Male Mice

Liver fatty acid binding protein (Fabp1) and sterol carrier protein‐2/sterol carrier protein‐x (SCP‐2/SCP‐x) genes encode proteins that enhance hepatic uptake, cytosolic transport, and peroxisomal oxidation of toxic branched‐chain fatty acids derived from dietary phytol. Since male wild‐type (WT) mice express markedly higher levels of these proteins than females, the impact of ablating both genes (TKO) was examined in phytol‐fed males. In WT males, high phytol diet alone had little impact on whole body weight and did not alter the proportion of lean tissue mass (LTM) versus fat tissue mass (FTM). TKO conferred on dietary phytol the ability to induce weight loss as well as reduce liver weight, FTM, and even more so LTM. Concomitantly TKO induced hepatic lipid accumulation, preferentially threefold increased phospholipid (PL) at the expense of decreased triacylglycerol (TG) and total cholesterol. Increased PL was associated with upregulation of membrane fatty acid transport/translocase proteins (FATP 2,4), cytosolic fatty acid/fatty acyl‐CoA binding proteins (FABP2, ACBP), and the rate limiting enzyme in PL synthesis (Gpam). Decreased TG and cholesterol levels were not attributable to altered levels in respective synthetic enzymes or nuclear receptors. These data suggest that the higher level of Fabp1 and Scp2/Scpx gene products in WT males was protective against deleterious effects of dietary phytol, but TKO significantly exacerbated phytol effects in males.     

Branched‐chain fatty acids as activators of peroxisome proliferator‐activated receptors

We observed earlier that phytanic acid activated subtype α of the peroxisome proliferator‐activated receptor (PPAR) via the cytosolic liver‐type fatty acid‐binding protein (L‐FABP). In a further search for minor lipid nutrients that interact with genes, we explored here the potential of branched‐chain fatty acids to serve as agonists for the PPAR subtypes α, β and γ in rodent and human molecular test systems. Beyond chlorophyll‐derived pristanic and phytanic acids, bacteria‐derived iso‐ and anteiso‐fatty acids and avian‐derived ‘uropygial’ fatty acids were tested by transactivation assay. In addition, we studied binding of these fatty acids to recombinantly expressed PPAR ligand binding domains (LBDs) and to L‐FABP by competition with fluorescent parinaric acid. In contrast to single methyl‐branched agonists, multi methyl‐branched fatty acids had high transactivation potentials in either test system; in addition, some agonists of the latter were highly subtype selective. Multi methyl‐branched chain fatty acids were superior activators of human PPARγ, a preference not seen in the murine test system. High‐affinity binding of isoprenoid‐derived pristanic and phytanic acids to PPARγ‐LBD and to L‐FABP was observed, and also of pristanic acid to PPARα‐LBD. Polyketidic uropygial fatty acids bound to PPARγ‐LBD only, though weakly. As both isoprenoid and polyketidic fatty acids showed high activation potentials, it became clear that binding data determined in vitro cannot predict biological activity as determined by transactivation assay. For pristanic acid, however, a signalling path similar to that found for phytanic acid can be concluded. Taken together, multi methyl‐branched fatty acids of the human food chain can affect cellular metabolism through regulating gene expression.     

Serum Fatty Acid-Binding Protein 4 is Increased in Patients with Psoriasis

Psoriasis is associated with metabolic syndrome and cardiovascular disease. Fatty acid‐binding proteins (FABP) have been recognized as predictors of these systemic disorders. The aim of this study was to assess correlations between levels of serum heart and adipocyte fatty acid‐binding proteins (FABP3, FABP4) and disease severity, indicators of inflammation or metabolic disturbances, and topical treatment in psoriatic patients. Thirty‐seven patients with relapse of plaque‐type psoriasis and 16 healthy volunteers were recruited. Blood samples were collected before and after 14 days of therapy. Serum FABP concentrations were examined by enzyme‐linked immunosorbent assay for correlation with Psoriasis Area and Severity Index (PASI), body mass index (BMI), inflammatory or metabolic parameters, and treatment used. The median FABP4 serum levels were significantly increased (p = 0.038) in psoriatic patients, while FABP3 levels did not differ (p = 0.47) compared to the controls. No significant correlations were noted between the proteins and PASI, C‐reactive protein (CRP), BMI, or levels of glucose or lipids. FABP3 significantly correlated with white blood count (p = 0.03) and aspartate aminotransferase (p = 0.04). After topical treatment, there was no significant change in serum FABP3 [11.5 (4.9–30.3) vs. 12.9 (3.5–30.3) ng/ml] (p = 0.96), whereas FABP4 was decreased [27,286 (20,344–32,257) vs. 23,034 (18,320–29,874) pg/ml] (p = 0.12), losing its basal significance. FABP4 may be a marker of psoriasis, and FABP3 may be associated with inflammation or liver disorders in psoriatic patients. FABP do not appear to be useful for determining disease severity or the effectiveness of antipsoriatic treatment.     

Immobilization of Lipid Substrates: Application on Phospholipase A2 Determination

The purpose of the study was to assess a fluorimetric assay for the determination of total phospholipase A₂ (PLA₂) activity in biological samples introducing the innovation of immobilized substrates on crosslinked polymeric membranes. The immobilized C₁₂‐NBD‐PtdCho, a fluorescent analogue of phosphatidylcholine, exhibited excellent stability for 3 months at 4 °C and was not desorbed in the aqueous reaction mixture during analysis. The limit of detection was 0.5 pmol FA (0.2 pg) and the linear part of the response curve extended from 1 up to 190 nmol FA/h/mL sample. The intra‐ and inter‐day relative standard deviations (%RSD), were ≤6 and ≤9 %, respectively. Statistical comparison with other fluorescent methods showed excellent correlation and agreement. Semiempirical calculations showed a fair amount of electrostatic interaction between the NBD‐labeled substrate and the crosslinked polyvinyl alcohol with the styryl pyridinium residues (PVA‐SbQ) material, from the plane of which, the sn‐2 acyl chain of the phospholipid stands out and is accessible by PLA₂. Atomic Force Microscopy revealed morphological alterations of the immobilized substrate after the reaction with PLA₂. Mass spectrometry showed that only C₁₂‐NBD‐FA, the PLA₂ hydrolysis product, was detected in the reaction mixture, indicating that PLA₂ recognizes PVA‐SbQ/C₁₂‐NBD‐PtdCho as a surface to perform catalysis.     

Metabolism of Anandamide into Eoxamides by 15-Lipoxygenase-1 and Glutathione Transferases

Human 15-lipoxygenase-1 (15-LO-1) can metabolize arachidonic acid (ARA) into pro-inflammatory mediators such as the eoxins, 15-hydroperoxyeicosatetraenoic acid (HPETE), and 15-hydroxyeicosatetraenoyl-phosphatidylethanolamine. We have in this study investigated the formation of various lipid hydroperoxide by either purified 15-LO-1 or in the Hodgkin lymphoma cell line L1236, which contain abundant amount of 15-LO-1. Both purified 15-LO-1 and L1236 cells produced lipid hydroperoxides more efficiently when anandamide (AEA) or 2-arachidonoyl-glycerol ester was used as substrate than with ARA. Furthermore, L1236 cells converted AEA to a novel class of cysteinyl-containing metabolites. Based on RP-HPLC, mass spectrometry and comparison to synthetic products, these metabolites were identified as the ethanolamide of the eoxin (EX) C(4) and EXD(4). By using the epoxide EXA(4)-ethanol amide, it was also found that platelets have the capacity to produce the ethanolamide of EXC(4) and EXD(4). We suggest that the ethanolamides of the eoxins should be referred to as eoxamides, in analogy to the ethanolamides of prostaglandins which are named prostamides. The metabolism of AEA into eoxamides might engender molecules with novel biological effects. Alternatively, it might represent a new mechanism for the termination of AEA signalling.     

Near‐stoichiometric O2 binding on metal centers in Co(salen) nanoparticles

Co(salen) [cobaltous bis(salicylaldehyde)ethylenediamine] complexes are well‐known O₂ carriers in solution. In the solid phase, these complexes exhibit some O₂ binding but detailed studies have been complicated because few of the known polymorphs of Co(salen) actually bind O₂. The O₂ binding results for nanoparticulate Co(salen) are presented in this study. Rod‐shaped Co(salen) nanoparticles, roughly 100 nm in diameter, were recrystallized by spraying a methylene chloride solution of commercially obtained Co(salen) into supercritical carbon dioxide. Temperature‐programmed desorption, thermogravimetric analysis, and a Rubotherm magnetic suspension balance measurements reveal a reversible O₂ uptake of ～1.51 mmol/(g nanoparticles) at 25°C, consistent with a binding stoichiometry involving a bridging peroxo unit between two Co centers. In contrast, no measurable O₂ uptake was observed with the commercial Co(salen). These results clearly show the potential for bottom‐up design of nanoparticulate metal complexes for enhanced O₂ storage and other applications. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

Enzymatic Synthesis of High sn-2 DHA and ARA Modified Oils for the Formulation of Infant Formula Fat Analogues

High sn‐2 docosahexaenoic and arachidonic acid oils (DHAO_m and ARAO_m, respectively) were produced independently via enzymatic interesterification of DHA‐rich and ARA‐rich single cell oils (DHASCO and ARASCO, respectively) using a mix of immobilized lipases, Lipozyme^® TL IM and Novozym^® 435 (weight ratio 1:1) as the biocatalyst system. Response surface methodology (RSM) was employed to model and optimize the reactions conditions. Three independent variables, namely reaction time, reaction temperature, and enzyme load, were investigated in DHAO_m and ARAO_m models. The prediction power of the model was further confirmed by solvent‐free scale‐up reactions of 100 g per batch. Final results showed that DHAO_m contained 46.53 mol% of total DHA (49.70 % at the sn‐2 position), while ARAO_m contained 47.25 mol% of total ARA (36.08 % at the sn‐2 position). This represents a significant increment in the amount of DHA and ARA at the sn‐2 position when compared to DHASCO (47.8 mol%; 30.30 % at the sn‐2) and ARASCO (47.79 mol%; 28.50 % at the sn‐2), respectively. These products have potential as additions to infant formulas where DHA and ARA supplementation is required.