Acyl Carbon Atom Research Articles

Comprehensive lipidomic analysis revealed the effects of fermented Morus alba L. intake on lipid profile in backfat and muscle tissue of Yuxi black pigs.

Mulberry leaf is a widely used protein feed and is often used as a strategy to reduce feed costs and improve meat quality in the livestock industry. However, to date, there is a lack of research on the improvement of meat quality using mulberry leaves, and the exact mechanisms are not yet known. The results showed that fermented mulberry leaves significantly reduced backfat content but had no significant effect on intramuscular fat (IMF). Lipidomic analysis showed that 98 and 303 differential lipid molecules (p < 0.05) were identified in adipose and muscle tissues, respectively, including triglycerides (TG), phosphatidylcholine, phosphatidylethanolamine, sphingolipids, and especially TG; therefore, we analysed the acyl carbon atom number of TG. The statistical results of acyl with different carbon atom numbers of TG in adipose tissue showed that the acyl group containing 13 carbon atoms (C13) in TG was significantly upregulated, whereas C15, C16, C17, and C23 were significantly downregulated, whereas in muscle tissue, the C12, C19, C23, C25, and C26 in TG were significantly downregulated. Acyl changes in TG were different for different numbers of carbon atoms in different tissues. We found that the correlations of C (14-18) in adipose tissue were higher, but in muscle tissue, the correlations of C (18-26) were higher. Through pathway enrichment analysis, we identified six and four metabolic pathways with the highest contributions of differential lipid metabolites in adipose and muscle tissues respectively. These findings suggest that fermented mulberry leaves improve meat quality mainly by inhibiting TG deposition by downregulating medium- and short-chain fatty acids in backfat tissue and long-chain fatty acids in muscle tissue.

Desaturase specificity is controlled by the physicochemical properties of a single amino acid residue in the substrate binding tunnel

Membrane fatty acyl desaturases (mFAD) are ubiquitous enzymes in eukaryotes. They introduce double bonds into fatty acids (FAs), producing structurally diverse unsaturated FAs which serve as membrane lipid components or precursors of signaling molecules. The mechanisms controlling enzymatic specificity and selectivity of desaturation are, however, poorly understood. We found that the physicochemical properties, particularly side chain volume, of a single amino acid (aa) residue in insect mFADs (Lepidoptera: Bombyx mori and Manduca sexta) control the desaturation products. Molecular dynamics simulations of systems comprising wild-type or mutant mFADs with fatty acyl-CoA substrates revealed that the single aa substitution likely directs the outcome of the desaturation reaction by modulating the distance between substrate fatty acyl carbon atoms and active center metal ions. These findings, as well as our methodology combining mFAD mutational screening with molecular dynamics simulations, will facilitate prediction of desaturation products and facilitate engineering of mFADs for biotechnological applications.

Acylation of Arylamines with Triethylamine Derivatives in Combination with tert‐Butyl Hydroperoxide

AbstractN‐acylation of arylamines with di‐ and trialkyl amines has been reported. This approach provides a general synthesis of aromatic amides by an alkyl transfer through cleavage of the C−N bond, and acts as a model for N‐dealkylations and N‐acylations. Additionally, the synthesis is a promising method towards amidation reactions, wherein di‐ and trialkyl amine derivatives are employed as sources of acyl carbon atoms and tert‐butyl hydroperoxide is employed as the oxygen source of the acyl group.

A Study on Triacylglycerol Composition and the Structure of High-Oleic Rapeseed Oil

The composition of fatty acids in triacylglycerides (TAGs) and their position on the glycerol backbone determine the nutritional value of vegetable oil. In this study, gas chromatography and high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) were used to analyze the composition and distribution of fatty acids in TAGs of different rapeseed oils. Our results show the content of oleic acid in high-oleic-acid rapeseed oil to be about 80%. In terms of the number of acyl carbon atoms (CN), TAGs with CN52–C54 were most abundant, with a maximum concentration at CN54 (80%). The main type of TAG was oleic-oleic-oleic (OOO), accounting for 71.75%, while oleic-oleic-linoleic (OOL) accounted for 7.56%, oleic-oleic-linolenic (OOLn) accounted for 4.81%, and stearic-oleic-oleic (SOO) accounted for 4.74%. Oleic acid in high-oleic-acid rapeseed oil was distributed in the following order of preference: sn-2 > sn-1/3. In high-erucic-acid rapeseed oil, however, oleic acid was enriched at the sn-1/3. These data show that the content of oleic acid can be as high as about 80% in high-oleic-acid material. This finding suggests that high-oleic-acid rapeseed oil has high nutritional value.

Reconstitution of [Fe]-hydrogenase using model complexes.

[Fe]-Hydrogenase catalyses the reversible hydrogenation of a methenyltetrahydromethanopterin substrate, which is an intermediate step during the methanogenesis from CO2 and H2. The active site contains an iron-guanylylpyridinol cofactor, in which Fe(2+) is coordinated by two CO ligands, as well as an acyl carbon atom and a pyridinyl nitrogen atom from a 3,4,5,6-substituted 2-pyridinol ligand. However, the mechanism of H2 activation by [Fe]-hydrogenase is unclear. Here we report the reconstitution of [Fe]-hydrogenase from an apoenzyme using two FeGP cofactor mimics to create semisynthetic enzymes. The small-molecule mimics reproduce the ligand environment of the active site, but are inactive towards H2 binding and activation on their own. We show that reconstituting the enzyme using a mimic that contains a 2-hydroxypyridine group restores activity, whereas an analogous enzyme with a 2-methoxypyridine complex was essentially inactive. These findings, together with density functional theory computations, support a mechanism in which the 2-hydroxy group is deprotonated before it serves as an internal base for heterolytic H2 cleavage.

Discovery and Mechanistic Studies of Facile N-Terminal Cα–C Bond Cleavages in the Dissociation of Tyrosine-Containing Peptide Radical Cations

Fascinating N-terminal Cα-C bond cleavages in a series of nonbasic tyrosine-containing peptide radical cations have been observed under low-energy collision-induced dissociation (CID), leading to the generation of rarely observed x-type radical fragments, with significant abundances. CID experiments of the radical cations of the alanyltyrosylglycine tripeptide and its analogues suggested that the N-terminal Cα-C bond cleavage, yielding its [x2 + H](•+) radical cation, does not involve an N-terminal α-carbon-centered radical. Theoretical examination of a prototypical radical cation of the alanyltyrosine dipeptide, using density functional theory calculations, suggested that direct N-terminal Cα-C bond cleavage could produce an ion-molecule complex formed between the incipient a1(+) and x1(•) fragments. Subsequent proton transfer from the iminium nitrogen atom in a1(+) to the acyl carbon atom in x1(•) results in the observable [x1 + H](•+). The barriers against this novel Cα-C bond cleavage and the competitive N-Cα bond cleavage, forming the complementary [c1 + 2H](+)/[z1 - H](•+) ion pair, are similar (ca. 16 kcal mol(-1)). Rice-Ramsperger-Kassel-Marcus modeling revealed that [x1 + H](•+) and [c1 + 2H](+) species are formed with comparable rates, in agreement with energy-resolved CID experiments for [AY](•+).

Molecular Structure of a Hydridoniobocene Complex [Nb(η5‐C5H4SiMe3)2(H)3] and Its Use as Catalyst for the Ring‐Opening Polymerization of Cyclic Esters

AbstractThe second polyhydridoniobocene complex that was characterized by X‐ray diffraction is reported. On the basis of H–H distances and H–Nb–H angles, [Nb(η5‐C5H4SiMe3)2(H)3] (1) is classified as a “compressed hydride”. Compound 1 acts as an efficient single‐component initiator for the ring‐opening polymerization of ϵ‐caprolactone and δ‐valerolactone. ϵ‐Caprolactone and δ‐valerolactone are both polymerized within a few hours to yield high‐to‐medium‐molecular‐weight polymers with medium to broad polydispersities. Polymer end‐group analysis showed that the polymerization proceeds through a coordination–insertion mechanism based on the cleavage of the ring between the oxygen atom and the acyl carbon atom.

ChemInform Abstract: Structure and Function of [Fe]‐Hydrogenase and Its Iron—Guanylylpyridinol (FeGP) Cofactor

AbstractReview: 45 refs.

Structure and Function of [Fe]‐Hydrogenase and its Iron–Guanylylpyridinol (FeGP) Cofactor

Abstract[Fe]‐hydrogenase functions in the methanogenic pathway of hydrogenotrophic methanogenic archaea. It catalyzes thereversible reduction of methenyltetrahydromethanopterin (methenyl‐H4MPT+) with H2 to methylene‐H4MPT and a proton by transferring a hydride ion to the proR position of the C14a carbon atom of methylene‐H4MPT. This third type of hydrogenase contains a unique iron–guanylylpyridinol (FeGP) cofactor, in which the iron atom is ligated by one cysteine sulfur atom, two CO groups, one solvent molecule, and an sp2‐hybridized nitrogen atom and an acyl carbon atom from the pyridinol ring. Three globular folding units of this protein form two clefts that serve as substrate‐binding and active sites and that can be open or closed. Structural data are presented for the apoenzyme in a closed form, the holoenzyme (enzyme with the FeGP cofactor), the C176A holoenzyme, and the binary C176A holoenzyme‐methylene‐H4MPT complex in an open form. A closed and potentially active binary complex has been reliably modeled on the basis of the open binary complex and the closed apoenzyme. In this model, the iron center sits near the Re face of the imidazolidine ring of the substrate. The iron ligation site trans to the acyl carbon atom is next to the C14a carbon atom and is therefore considered to be the H2 binding site.

Oxoketene–oxoketene, imidoylketene–imidoylketene and oxoketenimine–imidoylketene rearrangements. 1,3-Shifts of phenyl groups

Dibenzoylketene 5 undergoes degenerate 1,3-shifts of the phenyl group between acyl and ketene carbon atoms, thus interconverting it with 6 and 7. This 1,3-shift takes place in the gas phase under flash vacuum thermolysis (FVT) conditions, but not in solution at 110-145 degrees C. Imidoyl(benzoyl)ketene 13 undergoes degenerate 1,3-shift of the phenyl group on FVT, thus interconverting it with 14, but the ketenimine isomer 15 is not formed, and none of these shifts take place in the solid state at 250 degrees C. Imidoyl(p-toluoyl)ketene 21 undergoes a 1,3-p-tolyl shift, interconverting it with ketene 22 but not with ketenimine 23. The imidoyl(p-toluoyl)ketene rotamer 25 cyclizes to 4-toluoyloxyquinoline 28 and 4-quinolone 29. The cyclization of imidoyl(benzoyl)ketene 13 to 4-benzoyloxyquinoline 18, and of 25 to 28 involves 1,3-C-to-O shifts of benzoyl (toluoyl) groups. Calculations of the transition states for the transformations at the B3LYP/6-31G** level of theory are in agreement with the observed reaction preferences.

Development, Scope, and Mechanism of the Palladium-Catalyzed Intramolecular Hydroalkylation of 3-Butenyl β-Diketones.

Reaction of 7-octene-2,4-dione (3) with a catalytic amount of PdCl2(CH3CN)2 (4) (10 mol %) in dioxane at room temperature for 16 h formed 2-acetylcyclohexanone (5) in 81% yield as a single regioisomer. Byproducts in the conversion of 3 to 5 include 2,4-octanedione (13), 2-acetyl-2-cyclohexenone (14), 2-acetylphenol (15), (E)- and (Z)-6-octene-2,4-dione (17), (E)- and (Z)-5-octene-2,4-dione (18), the η3-β-diketonate chloride dimer {[η3-CH3CH2CH2CHCOHCHAc]Pd(Cl)}2 (12), and the π(allyl)palladium chloride dimer {[η3-CH3CHCHCHC(O)CH2Ac]Pd(Cl)}2 (16). The palladium-catalyzed cyclization of 3-butenyl β-diketones tolerated substitution at the terminal acyl carbon atom, the enolic carbon atom, and the terminal olefinic carbon atom. Deuterium-labeling studies, in conjunction with kinetic and in situ NMR experiments, supported a mechanism for the palladium-catalyzed hydroalkylation of 3-butenyl β-diketones initiated by 6-endo-trig attack of the enol carbon atom on a palladium-complexed olefin to form a palladium cy...

Development, Scope, and Mechanism of the Palladium-Catalyzed Intramolecular Hydroalkylation of 3-Butenyl β-Diketones

Reaction of 7-octene-2,4-dione (3) with a catalytic amount of PdCl2(CH3CN)2 (4) (10 mol %) in dioxane at room temperature for 16 h formed 2-acetylcyclohexanone (5) in 81% yield as a single regioisomer. Byproducts in the conversion of 3 to 5 include 2,4-octanedione (13), 2-acetyl-2-cyclohexenone (14), 2-acetylphenol (15), (E)- and (Z)-6-octene-2,4-dione (17), (E)- and (Z)-5-octene-2,4-dione (18), the η3-β-diketonate chloride dimer {[η3-CH3CH2CH2CHCOHCHAc]Pd(Cl)}2 (12), and the π(allyl)palladium chloride dimer {[η3-CH3CHCHCHC(O)CH2Ac]Pd(Cl)}2 (16). The palladium-catalyzed cyclization of 3-butenyl β-diketones tolerated substitution at the terminal acyl carbon atom, the enolic carbon atom, and the terminal olefinic carbon atom. Deuterium-labeling studies, in conjunction with kinetic and in situ NMR experiments, supported a mechanism for the palladium-catalyzed hydroalkylation of 3-butenyl β-diketones initiated by 6-endo-trig attack of the enol carbon atom on a palladium-complexed olefin to form a palladium cy...

Alcoholysis of acylpalladium(II) complexes relevant to the alternating copolymerization of ethene and carbon monoxide and the alkoxycarbonylation of alkenes: the importance of Cis-coordinating phosphines.

The mechanism and kinetics of the solvolysis of complexes of the type [(L-L)Pd(C(O)CH(3))(S)](+)[CF(3)SO(3)](-) (L-L = diphosphine ligand, S = solvent, CO, or donor atom in the ligand backbone) was studied by NMR and UV-vis spectroscopy with the use of the ligands a-j: SPANphos (a), dtbpf (b), Xantphos (c), dippf (d), DPEphos (e), dtbpx (f), dppf (g), dppp (h), calix-6-diphosphite (j). Acetyl palladium complexes containing trans-coordinating ligands that resist cis coordination (SPANphos, dtbpf) showed no methanolysis. Trans complexes that can undergo isomerization to the cis analogue (Xantphos, dippf, DPEphos) showed methanolyis of the acyl group at a moderate rate. The reaction of [trans-(DPEphos)Pd(C(O)CH(3))](+)[CF(3)SO(3)](-) (2e) with methanol shows a large negative entropy of activation. Cis complexes underwent competing decarbonylation and methanolysis with the exception of 2j, [cis-(calix-diphosphite)Pd(C(O)CH(3))(CD(3)OD)](+)[CF(3)SO(3)](-). The calix-6-diphosphite complex showed a large positive entropy of activation. It is concluded that ester elimination from acylpalladium complexes with alcohols requires cis geometry of the acyl group and coordinating alcohol. The reductive elimination of methyl acetate is described as a migratory elimination or a 1,2-shift of the alkoxy group from palladium to the acyl carbon atom. Cis complexes with bulky ligands such as dtbpx undergo an extremely fast methanolysis. An increasing steric bulk of the ligand favors the formation of methyl propanoate relative to the insertion of ethene leading to formation of oligomers or polymers in the catalytic reaction of ethene, carbon monoxide, and methanol.

NMR and density functional studies of the stereoselective palladium catalyzed cyclocarbonylation of (1 R,4 R)-isolimonene

Carbonylation of (1 R,4 R)-isolimonene, catalyzed by [HPd(SnCl 3)(dppf)], involves the exo- and endo-carboncarbon double bonds to provide a cyclopentanone containing two new stereogenic centers with d.e. of 69%. It was shown that this diastereoselectivity arose from the two stereogenic centers of the substrate. Calculations carried out on the cyclization step show that the metal center of the palladium–acyl species coordinates the endocyclic double bond in the endo-position exclusively. The net charge distribution over the palladium center, the acyl carbon atom and the two carbon atoms of the CC bond determines the two nucleophilic attacks in this step.

GC-FID- and acyl carbon number-based determination of characteristic groupings of complex triglyceride (Benefat S and other) mixtures.

Techniques for the gas and liquid chromatographic separation of complex mixtures of triglycerides have evolved over the past two decades, as reviewed in detail by Huang et al. (J. Agric. Food Chem. 1995, 43, 1834-1844; J. Agric. Food Chem. 1997, 45, 1770-1778). A novel method for the quantitative partitioning of complex mixtures of triglycerides into functionally related groups is developed and applied to a low-calorie triglyceride mixture [namely, Benefat S or Salatrim plus mid-chain (C(6,8,10,12)) fatty acids]. The method is based on a nonlinear calibration of retention times (RTs) of a suite of standard triglycerides on their acyl carbon numbers [(ACNs), the sum of all the acyl carbon atoms in a given triglyceride] to estimate all of the intermediate ACNs (from 6 to 66). With the calibrated ACN scale and identifications of some components of a complex mixture's composition, ACN-based partitions were established and a Benefat S-triglyceride chromatogram was partitioned into seven functionally related groups. This method is provisional in the sense that it would typically be employed when the identifications of many components of a complex, homologous series were unknown, yet functionally related groups needed to be quantified. This method has proven to be particularly useful in the intercalibration of research laboratories with production facility laboratories during complex ( approximately 50-90 compounds) and large-scale ( approximately 20 ton) syntheses because of the high reproducibility of the ACN-based partitioning of complex chromatograms. This carbon number and statistically based method can be generally applicable to other complex mixtures of organic compounds and is readily adaptable to laboratory intercalibration efforts.

Synthesis of acylphosphine complexes by controllable migration of acyl groups from molybdenum to phosphido ligands †

The acyl complexes [Mo(COR1)(CO)2(PPh2H)(η-C5H5)] (R1 = Me or Et) have been prepared in high yield by the reaction of [MoR1(CO)3(η-C5H5)] with PPh2H. Deprotonation of the diphenylphosphine ligand with 1,8-diazabicyclo[5.4.0]undec-7-ene (dbu) at –78 °C produced a phosphorus-centred anion which can be alkylated by treatment with R2I (R2 = Me or Et) to give the substituted phosphine acyl complexes [Mo(COR1)(CO)2(PPh2R2)(η-C5H5)], or acylated with R2COCl to produce acylphosphine acyl complexes [Mo(COR1)(CO)2(PPh2COR2)(η-C5H5)]. If the deprotonation is carried out at room temperature, however, migration of the metal acyl group to the phosphorus atom occurs to give the molybdenum-centred anion [Mo(CO)2(PPh2COR1)(η-C5H5)]–, which can in turn be alkylated with R2I to give the acylphosphine alkyl complexes [MoR2(CO)2(PPh2COR1)(η-C5H5)]. The metal-centred anion also undergoes typical reactions with H+ and chlorinated solvents to give [MoX(CO)2(PPh2COR1)(η-C5H5)] (X = H or Cl). Mechanistic studies showed that (i) on deprotonation of the related complex [MoMe(CO)2(PPh2H)(η-C5H5)] the methyl group does not undergo migration to phosphorus, and (ii) the reaction is largely intramolecular but with a measurable intermolecular component. A mechanism is therefore proposed involving nucleophilic attack on the acyl carbon atom by the anionic phosphido ligand. Full spectroscopic data for the new complexes are reported and interpreted, and the crystal structure of [Mo(COMe)(CO)2(PPh2COMe)(η-C5H5)] has been determined.

Reaction of [Ru3(CO)12] with 2-(chloromethyl)pyridine, syntheses of pyrid-2-ylacetyl ruthenium(II) complexes and crystal structure of [RuCl(C5H4N-2-CH2CO)(CO)(PPh3)2

Abstract The cycloruthenated pyrid-2-ylacetyl complex [[RuCl(C 5 H 4 N-2-CH in2 CO)(CO) 2 ] 2 ] ( 1 ) was obtained by reaction of [Ru 3 (CO) 12 ] with an excess of 2-(chloromethyl)pyridine in refluxing toluene. Subsequent reaction of 1 with two equivalents of triphenylphosphine in refluxing benzene afforded the bis(phosphine) derivative [RuCl(C 5 H 4 N-2-CH 2 CO)(CO)(PPh 3 ) 2 ] ( 2 ). X-ray analysis of 2 shows that the complex is monomeric with the ruthenium atom coordinated by ring nitrogen and acyl carbon atoms from the cycloruthenated pyrid-2-ylacetyl group, cis chlorine and carbonyl carbon atoms, and trans phosphorus atoms, to form a distorted octahedral geometry.

Gas-phase Ion-molecular reactions of C&lt;sub&gt;60&lt;/sub&gt; and C&lt;sub&gt;70&lt;/sub&gt; with Acetone and Quantum Chemistry Study

Gas-phase ion-molecular reactions of C-60 and C-70 with the ion system of acetone have been studied in this paper. The ions of protoned and acetylized C-60 and C-70 were formed by the reactions of C-60 and C-70 with some ions which existed in the ion system when mass spectrometer worked on chemical ionization conditions. The reactivity of C-70 is greater than that of C-60. Results of quantum chemical calculation for the adduct ions showed a sigma bond between the acyl carbon atom and C-60 may be Formed. These results will provide some valuable informations on the condense-phase acetylization of C-60.

Gas phase acetylation of C60 and C70 by ion/molecule reactions

AbstractGas phase reactions of C60 and C70 with the ion system of acetone under chemical ionization conditions have been studied. C60 and C70 can react with acetyl and oxonium ions, which come from self‐chemical ionization of acetone, to form adduct ions. In addition, C60 and C70 can accept protons to produce protonated ions. C70 is more active in the above reactions than C60 because of its stronger gas‐phase basicity. A σ‐bond between C60 and an acyl carbon atom can be formed to produce stable acetylated C60 ions. The above results may be relevant to the acetylation reactions of C60 in the condensed phase.

Prevention of myocardial lesions in JCR:LA-corpulent rats by nifedipine.

Male rats of the JCR:LA-corpulent strain spontaneously develop atherosclerosis and myocardial lesions if corpulent. The corpulent rats exhibit a marked very low density hyperlipidemia and insulin resistance. The incidence of both vascular and myocardial lesions correlates strongly with the hyperinsulinemia, but not with the hyperlipidemia. Corpulent male rats were chronically treated with nifedipine or acetylsalicylic acid to explore the roles of smooth muscle spasm and platelet activity in induction of the myocardial lesions. Acetylsalicylic acid treatment was associated with no significant changes in fasting glucose, insulin, or lipid concentrations. Nifedipine caused no significant changes in glucose concentration but was associated with mildly increased insulin levels. Treatment with nifedipine resulted in significant decreases in serum triglyceride concentrations. The decreases were confined to longer-chain triacylglycerol molecular species with no change in the concentration of molecular species with 48 or 50 acyl carbon atoms. There was no effect on myocardial lesion frequency with acetylsalicylic acid treatment. In contrast, nifedipine prevented the development of old organized scarred lesions. This effect is similar to that seen with treatments that markedly reduce the insulin resistance. These findings suggest that platelet-initiated thrombus formation is not an important factor in lesion formation in the JCR:LA-cp rat, but that smooth muscle spasm is probably important.