Position specificity of the fatty acids in the phospholipids of the cotton plant variety 108-F

It has been shown by enzymatic hydrolysis with phospholipase A that it is mainly unsaturated fatty acids that are esterified in positions of the PC, PE, and PI molecules (93.2, 86.2, and 76.8%, respectively), which is normal for phospholipids. From the results on the position distribution of the fatty acids we have calculated the possible molecular compositions of the PCs, PEs, and PIs.     

Identification of triacylglycerols containing two short-chain fatty acids at sn-2 and sn-3 positions from bovine udder by fast atom bombardment tandem mass spectrometry

Several triacylglycerol (TAG) molecular species, that contain two short-chain fatty acids (C4 to C8) at the sn-2 and sn-3 positions of the glycerol backbone, were isolated from bovine udder by using solvent extraction and silica gel column chromatography. Their structures were identified by fast atom bombardment (FAB) tandem mass spectrometry (MS/MS), based on the information obtained from collision-induced dissociation (CID) spectra of sodium-adducted molecules ([M + Na](+)) of model TAG compounds which had been synthesized from glycerol and appropriate fatty acids. For each species, the relative positions of the three fatty acids on the glycerol backbone, as well as fatty acid composition and double-bond position in the fatty acyl group, were determined. A majority of sodium-adducted molecules observed in the FAB mass spectrum were mixtures of at least two components that have different fatty acid composition but the same molecular mass. In addition, all the components present in mixtures of all the species contain a long-chain fatty acid (C12 to C18) at the sn-1 position, a short-chain fatty acid (C4 to C8) at the sn-2 position, and a butyric acid uniquely at the sn-3 position.     

Time-dependent SERS of pseudoisocyanine on silver particles generated in silver bromide sol by laser illumination

SERS spectra of pseudoisocyanine dye (PIC) in silver bromide sols show a strong time-dependence. The enhancement factor, in general, follows the formation (and destruction) of SERS-active colloidal silver in the silver halide sols by laser illumination during the Raman measurement. Changes in the relative intensities within a characteristic fine triplet of the SERS spectrum show that the surface potential which is “seen” by the dye molecules shifts to more positive values with longer times. In particular, the values of the potential hint at the existence of Ag₁ and Ag₄ … Ag₆ clusters as SERS-active adsorption sites of the dye molecules in AgBr sols.     

Structure elucidation of unsaturated fatty acids after vicinal hydroxylation of the double bonds by negative electrospray ionisation low-energy tandem mass spectrometry

A method for determining the positions of double bonds in unsaturated fatty acids by use of negative electrospray ionisation low-energy tandem mass spectrometry is described. First, a vicinal hydroxylation of the double bonds of mono- and poly-unsaturated fatty acids was performed. Low-energy collision activation dissociation of the deprotonated molecules produced structurally informative ions formed by a-cleavages relative to the hydroxyl groups. Abundant fragment ions that confirmed the positions of all hydroxyl groups, and thus the positions of the double bonds in the native fatty acids, were observed in the spectra of derivatised mono-, di-, and tri-unsaturated fatty acids. Two types of ions were observed, called [alpha'(n)](-) and [alpha(n)](-). The letter n indicates the positions of the hydroxyl groups. The structurally diagnostic ions [alpha'(n)](-) were produced by cleavages distal to the hydroxyl-groups with the charge retained on the carboxylate. [alpha'(n)](-) ions originating from all hydroxyl-groups were observed in the spectra of modified mono-, di-, and tri-unsaturated fatty acids. Initial proton transfer of a hydroxyl proton to the carboxylate with subsequent cleavages proximal to the hydroxyl groups, relative to the carboxylate, resulted in the two structurally diagnostic [alpha(n)](-) ions. In hydroxylated fatty acids having two or more double bonds in their native structure, [alpha(n)](-) ions originating only from the two final hydroxyl-groups were observed. The formation of all ions of [alpha'(n)](-) and [alpha(n)](-) type can be rationalised by a six-membered transition state. Hydroxylated deprotonated tetra-, penta-, and hexa-unsaturated fatty acids also produced [alpha'(n)](-) ions indicating the positions of most of the hydroxyl-groups, whereas the [alpha(n)](-) ions were observed as described above. The method described offers a simple approach to the determination of the positions of double bonds in unsaturated fatty acids, and is an alternative to utilising di-lithiated fatty acids. The method should also be applicable when fatty acids are constituents of more complex molecules such as phospholipids.     

Position specificity of the fatty acids in the phospholipids of the cotton plant variety 108-F

Summary It has been shown by enzymatic hydrolysis with phospholipase A that it is mainly unsaturated fatty acids that are esterified in positions of the PC, PE, and PI molecules (93.2, 86.2, and 76.8%, respectively), which is normal for phospholipids.From the results on the position distribution of the fatty acids we have calculated the possible molecular compositions of the PCs, PEs, and PIs.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 589–590, September–October, 1976.     

Adsorption of fatty acids from solutions in organic solvents on the surface of finely dispersed magnetite: 1. Isotherms of adsorption of oleic,linoleic, and linolenic acid from carbon tetrachloride and hexane

Isotherms of adsorption of oleic, linoleic, and linolenic acids on magnetite from solutions in carbon tetrachloride and hexane are measured. When CCl₄ is used as a solvent, the adsorption values increase in the following order: oleic, linoleic, and linolenic acid. In the case of hexane, the order is opposite. Adsorption isotherms of the fatty acids on aggregated magnetite are described in terms of the theory of volume filling of micropores. It is disclosed that, in the case of CCl₄ , the limiting adsorption values and characteristic energies of the process increase in a series: oleic, linoleic, and linolenic acid, but in the case of hexane, they decrease in the same sequence. Upon the adsorption of fatty acids from solutions in CCl₄ and hexane on finely dispersed magnetite, molecules of the acids and solvents compete for the active sites on the adsorbent surface. The number of double bonds in the molecules of unsaturated fatty acids and the desolvation of both the adsorbent surface and adsorbate molecules substantially affect the adsorption of these acids. The effect of the solvents is most pronounced for the adsorption of oleic acid, decreasing with a rise in the number of double bonds in a fatty acid molecule.Translated from Kolloidnyi Zhurnal, Vol. 66, No. 6, 2004, pp. 779–783.Original Russian Text Copyright © 2004 by Korolev, Ramazanova, Yashkova, Balmasova, Blinov.     

Polymorphism and intermolecular interactions in crystalline fluorinated alkylbenzoic acids

Thermodynamic and spectral characteristics of fluorinated derivatives of alkylbenzoic acids (FABA) were studied in the temperature range 100–550 K. Experimental values of temperatures, enthalpies and entropies of phase transitions, as well as hydrogen bond energy at different temperatures and in the various physical (phase) states were compared to those for alkyl- and fluoroalkyl-benzoic acids. IR absorption spectra of substances studied were interpreted on the basis of theoretical calculations of frequencies, shapes and intensities of normal modes of molecular vibrations using the published data for related compounds. The information derived was used to construct models of packing of dimerized molecules of FABA in the crystalline state, and possible causes of the absence of mesomorphism on complete fluorination of alkyl radical were discussed.     

Structural change of 1-butyl-3-methylimidazolium tetrafluoroborate + water mixtures studied by infrared vibrational spectroscopy

Mixtures of ionic liquid (IL, 1-butyl-3-methylimidazolium tetrafluoroborate, [BMIM][BF4]) and water with varying concentrations were studied by attenuated total reflection infrared absorption and Raman spectroscopy. Changes in the peak intensities and peak positions of CHx (x = 1, 2, 3) vibration modes of the cation of the IL and OH vibration modes of the water molecules were investigated. Peaks from normal-mode stretch vibrations of CH bonds belonging to the imidazolium ring of the cation did not change their positions, while those from the terminal methyl group of the butyl chain blueshifted by approximately 10 cm-1 with the addition of water. On the other hand, change in the spectral shape in the OH stretch vibration region shows hydrogen-bonding network of water molecules breaking down rapidly as the IL is added. Trends in the change of the peak positions and the peak intensities suggested qualitative change of the intermolecular structure in the [BMIM][BF4] + H2O mixture at 32 +/- 2 and 45 +/- 2 mol/L of water concentration.     

Mixed Langmuir monolayers of cholesterol and `essential' fatty acids

Langmuir monolayers of cholesterol and various fatty acids, such as stearic, oleic, linoleic, α-linolenic, and arachidonic acids, spread at the air/water interface are investigated. The system of cholesterol and stearic acid is found to be immiscible, with only one collapse, occurring at the same surface pressure for all composition range. However, surface pressure (π) – area (A) isotherms of cholesterol/unsaturated fatty acids show a characteristic course with two collapse states. The pressure of the first collapse varies with the proportion of the components in the mixture, while the second collapse, occurring at the surface pressure characteristic of cholesterol alone, is independent of mole fraction of the investigated fatty acid. The application of the surface phase rule indicates that the unsaturated fatty acids/cholesterol mixtures are miscible up to the surface pressure corresponding to the first collapse. Negative values of the excess free energy of mixing in all composition ranges prove that the mixtures are stable. The interactions existing in mixtures of cholesterol and unsaturated fatty acids possessing even numbers of double bonds are strongest in the lower region of fatty acid proportion, and the results are consistent with the minimum values of the excess free energy of mixing, indicating the most stable mixtures. For cholesterol and unsaturated fatty acids with odd numbers of double bonds the behavior is different, and the strongest interactions occur in both low and high regions of mole fraction of an acid. Received: 2 May 2000 Accepted: 26 October 2000     

A Narrative Review of the Current Knowledge on Fruit Active Aroma Using Gas Chromatography-Olfactometry (GC-O) Analysis

Fruit aroma, a mixture of chemical compounds with odor, is a strong attractant derived from a complex mixture of different amounts and intensities (threshold) of chemical compounds found in fruits. The odor-producing compounds of fruit aroma are derived from carbohydrates, lipids, phenolic compounds, and mono- and sesquiterpenes, among others. The identification of compounds responsible for fruit aroma is usually conducted using gas chromatography coupled with olfactometry (GC-O). This technique separates the chemical compounds from the aroma of foods using a chromatographic column and divides the resultant outflow between the physical detector and a testing outlet (sniffing port). Trained judges describe the perceived odor in terms of the intensity of the odor zones perceived according to their training method. Moreover, the use of GC-O coupled with a mass detector (GC-MS-O) allows for the retrieval of chemical information such as identification and quantification of compounds, which can be correlated to sensory information. This review aimed to demonstrate the application of GC-MS-O in the identification of precursor compounds in fruit aroma, considering important factors for the application, main results, and most recent advances in this field.     

Antioxidant properties of natural substances in irradiated fresh poultry

This study was undertaken to determine if a combined treatment (marinating in natural plant extracts or vacuum) with irradiation could have a synergistic effect, in order to prevent the lipid oxidation resulting in the development of undesirable flavours. The fresh chicken legs were irradiated at 0,3 and 5 kGy. The fatty acids composition of lipids was identified using gas liquid chromatography. The effect of irradiation treatment combined with a pre-treatment on the fatty acids composition was followed. The day after irradiation, ten panallists were asked to evaluate, using the instruction scaling, the overall appearance, the odor, the flavor and the overall acceptability of the samples. The major fatty acids identified in lipids were oleic acid, palmitic acid, palmitoleic acid and stearic acid. Pre-treatments have a significant effect on linoleic acid (C18:2) and higher fatty acids. The unsaturated fatty acids derived from phospholipids appeared to be more affected by the irradiation dose: however, marinating have better protection on C18:2 derived from phospholipids. The results of sensory evaluation have shown a significant better odor and flavor for the irradiated chicken at 5 kGy than the control. No significant difference have been found between the marinated chicken, the chicken irradiated under vacuum and the control.     

Steric and allosteric effects of fatty acids on the binding of warfarin to human serum albumin revealed by molecular dynamics and free energy calculations

Human serum albumin (HSA) binds with drugs and fatty acids (FAs). This study was initiated to elucidate the relationship between the warfarin binding affinity of HSA and the positions of bound FA molecules. Molecular dynamics simulations of 11 HSA-warfarin-myristate complexes were performed. HSA-warfarin binding free energy was then calculated for each of the complexes by the molecular mechanics-Poisson-Boltzmann surface area (MM-PBSA) method. The results indicated that the magnitude of the binding free energy was smaller in HSA-warfarin complexes that had 4 or more myristate molecules than in complexes with no myristate molecules. The unfavorable effect on the HSA-warfarin binding affinity was caused sterically by the binding of a myristate molecule to the FA binding site closest to the warfarin binding site. On the other hand, the magnitude of HSA-warfarin binding free energy was largest when 3 myristate molecules were bound to the high-affinity sites. The strongest HSA-warfarin binding was attributable to favorable entropic contribution related to larger atomic fluctuations of the amino acid residues at the warfarin binding site. In the binding of 2 myristate molecules to the sites with the highest and second-highest affinities, allosteric modulation that enhanced electrostatic interactions between warfarin and some of the amino acid residues around the warfarin binding site was observed. This study clarified the structural and energetic properties of steric/allosteric effects of FAs on the HSA-warfarin binding affinity and illustrated the approach to analyze protein-ligand interactions in situations such that multiple ligands bind to the other sites of the protein.     

A rapid method for molecular shape comparison of medium-sized molecules. Conformational calculations on sandalwood odor,IV

Summary A fast method of a surface comparison of two or more molecules to be matched is presented. The Van der Waals surfaces of molecules are described by points calculated as the intersection of grid lines with the molecular surface. The mean surface of various molecules with the same biological activity can be constructed. It is used for further comparisons with similar molecules lacking this activity. Deviations of any molecular surface from the mean surface can be mapped onto the surface. The method was tested on a distinct group of sandalwood odor molecules and it was shown that such matching and comparison procedures are useful in the investigation of odor structure-activity relationships proposed as CAFD (computer aided fragrance design).Dedicated to Prof. Dr. W. Fleischhacker, on occasion of his 60th anniversary     

Isotopologs and isotopomers: New analytical aspects of isotopic mass spectrometry in biology

Metabolic products of biological systems in most cases are polyatomic molecular structures containing polyisotopic elements (hydrogen, carbon, nitrogen, oxygen, sulfur, chorine, etc.) that are different in genesis and biosynthetic pathways. In the molecules carrying two and more atoms of polyisotopic element in different positions (sites), the probability of detection of isotopes by sites in the pool (array) of analyzed molecules may be different, i.e., there is intramolecular isotopic heterogeneity by the specified element. Detection and quantitative estimation of isotopic heterogeneity of polyisotopic elements in molecules by the methods of isotopic mass spectrometry is a novel source of information about the processes involving the respective polyisotopic element. An isotopic equation has been proposed, the coefficients of which are normalized peak intensities of isotopically different molecular ions in the mass spectrum of the analyte. Solutions of this equation reflect the abundance ratios of isotopic atoms of polyisotopic element by its positions in molecules comprising the analyzed pool. During homogenous (equally probable) distribution of isotopic atoms of the element by all of its sites in molecules of the analyzed pool, solutions of the isotopic equation are equal to each other. In the case of non-homogenous isotope distribution of the polyisotopic element in the pool of molecules, solutions of the isotopic equation take on different values and may be presented by both real and complex numbers. Solutions of the isotopic equation reflect the peculiarities of distribution of element isotopes in a molecule and possible pathways of formation of a pool of analyzed molecules under laboratory and natural conditions.     

气相色谱–质谱法测定人体气味中4种脂肪酸

建立搅拌棒吸附萃取–气相色谱–质谱法测定人体气味中正十二烷酸、正十三烷酸、正十四烷酸、正十六烷酸4种脂肪酸的方法。利用PDMS涂层搅拌吸附棒直接采集人体气味,采用热脱附程序升温进样方式气相色谱法测定人体气味中4种脂肪酸。以7-十三酮为内标,建立了4种脂肪酸的内标定量分析方法,线性范围为20~180ng,相关系数r^2为0.992 0~0.997 5,4种脂肪酸的检出限为3.2~7.5 ng。在40 ng加标水平下,样品加标回收率为90%~105%,测定结果的相对标准偏差为2.7%~4.0%(n=5)。该方法已应用于人体气味化学组分分析,满足分析要求。     

A steroid-based receptor for unprotected amino acids: the enantioselective recognition of l-tryptophan

A cholapod receptor possessing urea binding sites at C3, C7, and C12 positions and with an intrinsic chiral structure was synthesized, and the binding abilities toward amino acids in both l- and d- forms (Trp, Phe, Leu, and Ala) were studied using ¹H NMR spectroscopy, UV-vis spectroscopy and computer simulation. Changes in ¹H NMR spectra of the receptor revealed that complexation with amino acids occurred via hydrogen bonding and CH-π interactions. Binding to tryptophan was especially strong, and was found to be enantioselective (K_a=480 M⁻¹ for l-Trp, 260 M⁻¹ for d-Trp). NOESY and computer simulations were used to investigate the structures of the diastereomeric complexes between the receptor and the tryptophan enantiomers. In the case of l-Trp the carboxylate group bound at the two ureas adjacent to C7 and C12, while d-Trp was positioned closer to the urea adjacent to C3.     

Bioaccessibility and Oxidative Stability of Omega-3 Fatty Acids in Supplements,Sardines and Enriched Eggs Studied Using a Static In Vitro Gastrointestinal Model

Modern dietary habits have created the need for the design and production of functional foods enriched in bioactive compounds for a healthy lifestyle. However, the fate of many of these bioactive compounds in the human gastrointestinal (GI) tract has not been thoroughly investigated. Thus, in the present study, the bioaccessibility of omega-3 fatty acids was examined. To that end, different foods and supplements underwent simulated digestion following the INFOGEST protocol. The selected samples were foods rich in omega-3 fatty acids both in free and bound form—i.e., dietary fish oil supplements, heat-treated fish, and eggs enriched with omega-3 fatty acids. The oxidation of polyunsaturated fatty acids (PUFAs) was measured at each stage of the digestion process using peroxide value (PV) and TBARS and by quantifying individual omega-3 fatty acids using a gas chromatograph with flame ionization detector (GC-FID). The final bioaccessibility values of omega-3 fatty acids were determined. Changes in the quantity of mono-saturated fatty acids (MUFAs) and saturated fatty acids (SFAs) were recorded as well. The results indicated a profound oxidation of omega-3 fatty acids, giving rise to both primary and secondary oxidation products. Additionally, stomach conditions seemed to exert the most significant effect on the oxidation of PUFAs during digestion, significantly decreasing their bioaccessibility. The oxidation rate of each fatty acid was found to be strongly correlated with its initial concentration. Finally, the oxidation pattern was found to be different for each matrix and emulsified lipids seemed to be better protected than non-emulsified lipids. It is concluded that digestion has a profound negative effect on omega-3 bioaccessibility and therefore there is a need for improved protective mechanisms.     

INHIBITORY PROPERTY CHARACTERIZATION AND REACTIVE SITE EXPLORATION OF THE ARROWHEAD PROTEINASE INHIBITOR

Affinity chromatography was used to separate two components A and B of the crystalline arrowhead proteinase inhibitor. Both A and B are double-headed and multifunctional proteinase inhibitors. Inhibitor A is capable of inhibiting equimolarly trypsin and chymo-trypsin simultaneously, and has a weak inhibitory activity toward kallikrein; whereas inhibitor B can inhibit two molecules of trypsin simultaneously, and shows rather higher inhibitory activity toward kallikrein than inhibitor A, but its inhibitory activity toward chymo-trypsin is much weaker than that of inhibitor A. The results of chemical modification and the competitive binding of trypsin and chymotrypsin with inhibitor A showed that the two reactive sites of both inhibitors A and B are Lys and Arg residues. Among them the Lys reactive site is specific for inhibiting mainly trypsin, whereas the active domain composed of the Arg reactive site appears to be multifunctional and capable of inhibiting many different Ser proteinases. Based on the st     

Inhibitory property characterization and reactive site exploration of the arrowhead proteinase inhibitor

Affinity chromatography was used to separate two components A and B of the crystalline arrowhead proteinase inhibitor. Both A and B are double-headed and multifunctional proteinase inhibitors. Inhibitor A is capable of inhibiting equimolarly trypsin and chymotrypsin simultaneously, and has a weak inhibitory activity toward kallikrein; whereas inhibitor B can inhibit two molecules of trypsin simultaneously, and shows rather higher inhibitory activity toward kallikrein than inhibitor A, but its inhibitory activity toward chymotrypsin is much weaker than that of inhibitor A. The results of chemical modification and the competitive binding of trypsin and chymotrypsin with inhibitor A showed that the two reactive sites of both inhibitors A and B are Lys and Arg residues. Among them the Lys reactive site is specific for inhibiting mainly trypsin, whereas the active domain composed of the Arg reactive site appears to be multifunctional and capable of inhibiting many different Ser proteinases. Based on the structural characteristics of inhibitors A and B, it was predicated that the two reactive sites should be located in the positions Lys-Ser (44-45) and Arg-Tyr-Lys (76-78), respectively. In inhibitor A, there exists another hydrophobic residue involved in inhibiting chymotrypsin. This residue might be situated in the reactive region composed of the Arg reactive site.