Improved resolution of31P nuclear magnetic resonance spectra of phospholipids from brain

A method is described wherein the resolution of³¹P nuclear magnetic resonance spectra of the lipophilic fraction from a Bligh-Dyer extract of rat brain can be enhanced. The lipids are dispersed as micelles in aqueous solution with sodium deoxycholate, and spectral resolution is further optimized by adjusting the pH and by removing ions from the solution. The application of the method to the study of aging in rat brain serves as an example.     

31P nuclear magnetic resonance phospholipid analysis of anionic-enriched lecithins

Phosphorus-31 nuclear magnetic resonance provides well-dispersed, quantifiable phospholipid profiles of commercial and laboratory anionic lecithin preparations. Seventeen phospholipids were determined in commercial soybean lecithins. Lecithin refinement to produce anionic-enriched lecithins may be monitored precisely.     

Alterations in heart and kidney membrane phospholipids in hypertension as observed by 31P nuclear magnetic resonance

Abnormalities of phospholipids in hypertension have previously been described in human erythrocyte, platelet, and plasma lipoproteins. Since the heart and kidney are adversely affected by hypertension, we investigated possible alterations in their membrane phospholipids, which could play a role in the derangement of intracellular ion balance widely observed in hypertension. The phospholipid compositions of heart and kidney from spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats were determined by using ³¹P nuclear magnetic resonance (NMR) spectroscopy. Absolute contents of all phospholipids in hypertensive hearts and kidneys were significantly higher than in normotensive hearts and kidneys. Expressed as a fraction of total phospholipid, cardiolipin (CL) and phosphatidylethanolamine plasmalogen (PEp) were significantly increased in SHR hearts compared to WKY hearts (CL and PEp were 7.95±0.22% and 13.16±0.35% in SHR vs. 7.01±0.20% and 11.19±0.42% in WKY rats, P<-0.05), but phosphatidylethanolamine (PE) and phosphatidylcholine (PC) were significantly decreased in SHR (PE and PC were 22.46±0.37% and 44.81±0.43% in SHR vs. 24.02±0.44% and 46.01±0.50% in WKY rats, p≤0.05). In the phospholipids extracted from rat kidneys, the percentage of PE was significantly higher for SHR than for WKY rats (20.37±0.60% vs. 18.43±0.37%, P≤0.05), while PEp and phosphatidylserine (PS) were significantly lower for SHR (PEp and PS were 10.22±0.36% and 8.42 ±0.28% in SHRs vs. 11.29±0.36% and 9.71±0.40% in WKY rats, P≤0.05). The above alterations in phospholipid composition might contribute to the higher oxygen consumption in the hypertensive heart and abnormal intracellular ion concentrations and ion transport in the heart and the kidney in hypertension.     

Phospholipid profiling of sediments using phosphorus-31 nuclear magnetic resonance

A phosphorus-31 nuclear magnetic resonance method has been developed for the determination of aquatic sediment phospholipid profiles that may be generally applied to all soils and deposits containing viable cellular material. A method of scrubbing chloroform/methanol extracts with potassium acid phosphate overcomes adverse signal broadening from the mineral component, permitting eleven sediment phospholipids to be determined at the quantitative level.     

Meningioma phospholipid profiles measured by31P nuclear magnetic resonance spectroscopy

Fourteen cases of intracranial meningioma were characterized after chloroform/methanol extraction by³¹P nuclear magnetic resonance (NMR) spectroscopy at 202.4 MHz. Each phospholipid class detected in the extracts was identified and quantitated in terms of its molar percentage relative to the total phospholipids measured. The following phospholipids were assayed by³¹P NMR: phosphatidylglycerol, phosphatidic acid, diphosphatidylglycerol, ethanolamine plasmalogen, phosphatidylethanolamine (PE), lysophosphatidylinositol, phosphatidylserine, sphingomyelin, lysophosphatidylcholine (LPC), phosphatidylinositol (PI), sphingosylphosphorylcholine and phosphatidylcholine. In addition, two unidentified phospholipids were detected with resonances at 0.13 and −0.78 ppm, respectively. Three distinct types of spectra were obtained on the extracts and grouped accordingly for comparison purposes. Type 1 tumors showed unusual³¹P NMR profiles with low levels of PE and PI and elevated levels of LPC; type 2 tumors were characterized by low levels of the ethanolamine phospholipids and near equivalent levels of PI and LPC. The spectra of type 1 and type 2 tumors were characteristic of degenerative cells that lacked membrane permeability associated with loss of ethanolamine plasmalogen in the presence of significant phospholipid turnover. Meningiomas belonging to the third spectral type showed characteristics similar to those of normal tissues with normal levels of PE and ethanolamine plasmalogen, as well as very low levels of LPC relative to PI. Type 3 tumors lacked the characteristic signs of degeneration noted in type 1 and type 2 tumors. The data corroborate and augmentin vivo spectroscopic findings reported earlier and demonstrate the value of³¹P NMR spectroscopic phospholipid analysis on lipid extracts for the characterization of meningiomas.     

31P nuclear magnetic resonance studies on alkyl phosphate emulsifiers in cosmetic oil-in-water emulsions

Cosmetic oil-in-water emulsions with a stearyl phosphate emulsifier are examined by means of static and dynamic ³¹P nuclear magnetic resonance (NMR) techniques to characterize the molecular properties of the emulsifier in situ. The interfacially bound emulsifier can be deteced by high-resolution NMR spectroscopy, whereas the excess emulsifier exists as a solid lipid phase not detectable by this technique. The emulsions and the emulsifier raw material, consisting of monostearyl phosphate as well as distearly phosphate, are examined by solid state cross polarization magic angle spinning NMR spectroscopy to prove the existence of solid emulsifier phases in the emulsions. By applying dynamic ³¹P NMR methods to the interfacially bound emulsifier, information about the molecular dynamics at the interface is obtained. The results of the T ₁ and T ₂ relaxation time measurements indicate a restricted motion of the molecules that is dependent on the oil droplet size in the emulsions. This is verified by ³¹P NMR pulsed gradient spin echo self-diffusion measurements on emulsions with different droplet sizes. Only about 5 wt% of the total emulsifier used is bound at the interface; the excess forms solid lipid phases. The coverage of the interface seems to be independent of the emulsifier concentration. Only the monoester of the emulsifier raw material shows interfacial activity. Its mobility indicates the two-dimensional environment of the molecules on the surface of the oil droplets.     

Quantitative applications of high-resolution proton magnetic resonance measurements in the characterization of detergent chemicals

Quantitative hydrogen nuclear magnetic resonance measurements are used for the determination of average structures of detergent chemicals. For alkylbenzenes, alkylphenols, and ethylene oxide (EO) adducts of alkylphenols, the following quantities can be measured: average lengths of alkyl chains, average molecular weights, degree and kind of branching in the alkyl chain, ortho-para distribution of aryl substituents, and average lengths of BO chains. Accuracy is of the the order of ± 2% of the total hydrogen. The method is nondestructive, and sample volumes as small as 0.007 ml have been used.     

A31P nuclear magnetic resonance investigation of acyl group transfer from phosphatidylcholine to yield lysophosphatidylcholine in human plasma

³¹P nuclear magnetic resonance (NMR) spectroscopy was used to measure the rate of acyl transfer from phosphatidylcholine (lecithin, PC) in whole plasma and in high density lipoprotein (HDL). Spectral deconvolution was used to resolve overlapping resonances in the³¹P NMR spectra of the phospholipids. Mean values of the acyl group transfer rates from PC in plasma and HDL were 36 μmol L⁻¹h⁻¹ and 19 μmol L⁻¹h⁻¹, respectively. The reciprocal nature of the decrease in the spectral peak intensities of PC, compared to the increase in the intensities of the lysolecithin (lysoPC) peaks, suggested a substrate/product relationship consistent with the action of lecithin:cholesterol acyltransferase (LCAT), the enzyme responsible for the esterification of free cholesterol in plasma. LCAT involvement was confirmed by measuring the cholesterol esterification rate based on the¹³C NMR spectra obtained on lipid extracts from plasma that had been incubated at 37°C. Within experimental error, the rate of lysoPC formation in plasma was shown to be equal to that of cholesteryl ester formation.     

Competition between Li+ and Mg2+ for red blood cell membrane phospholipids: A 31P, 7Li, and 6Li nuclear magnetic resonance study

The mode of action of the lithium ion (Li⁺) in the treatment of manic depression or bipolar illness is still under investigation, although this inorganic drug has been in clinical use for 50 yr. Several research reports have provided evidence for Li⁺/Mg²⁺ competition in biomolecules. We carried out this study to characterize the interactions of Li⁺ and Mg²⁺ with red blood cell (RBC) membrane components to see whether Li⁺/Mg²⁺ competition occurs. ³¹P nuclear magnetic resonance chemical shift measurements of the phospholipids extracted from the RBC membranes indicated that the anionic phospholipids, phosphatidylserine and phosphatidylinositol, bind Li⁺ and Mg²⁺ most strongly. From ⁶Li relaxation measurements, the Li⁺ binding constant to the phospholipid extract was found to be 45±5M⁻¹. Thus, these studies showed that the phospholipids play a major role in metal ion binding. ⁷Li spin-lattice relaxation measurements conducted on unsealed and cytoskeleton-depleted RBC membrane in the presence of magnesium indicated that the removal of the cytoskeleton increases lithium binding to the more exposed anionic phospholipids (357±24 M⁻¹) when compared to lithium binding in the unsealed RBC membrane (221±21 M⁻¹). Therefore, it can be seen that the cytoskeleton does not play a major role in Li⁺ binding or in Li⁺/Mg²⁺ competition.     

Carbon-13 nuclear magnetic resonance analysis of intact oilseeds

High resolution natural abundance¹³C nuclear magnetic resonance (NMR) spectra of intact oilseeds have been obtained by Fourier transform techniques. The spectra can be interpreted in terms of the relative concentrations of the major fatty acids in the oilseed. The¹³C NMR spectra are well resolved despite the fact that¹H NMR spectra of the same seeds are poorly resolved. The difference in resolution can be attributed to the simplicity of the¹³C NMR spectra in which all spin-spin coupling can be removed, in which the separation of lines is increased by a factor of 30, and in which line broadening due to intermolecular dipolar interactions is not important. The¹³C NMR Fourier transform technique is sufficiently sensitive that a high quality spectrum can be obtained from a single soybean, for example, in about 10 minutes. Similar spectra of single seeds can be obtained in comparable times for corn, castor bean, peanut, sunflower seed, and rapeseed. Because the NMR technique is nondestructive, it can be used to select individual oilseeds for use in breeding programs designed to improve oil quality. By employing some special experimental NMR line narrowing techniques, it also appears feasible to obtain moderately well resolved, natural abundance¹³C NMR spectra of the immobile, rigid protein, and carbohydrate components of an intact oilseed, as well as the more mobile oil components.     

Measurement of solids in triglycerides using nuclear magnetic resonance spectroscopy

A rapid and accurate method using nuclear magnetic resonance (NMR) spectroscopy is presented for determining the percentage of solids in fats and shortenings conditioned at selected temperatures or as received in the laboratory. This method provides more reliable information on the solids content of fatty materials than the empirical dilatometric solid fat index, and is applicable in the range of 50–100% solids which is beyond the limit of the official solid fat index method. The relationship between instrument response and actual solids present was determined on known mixtures of liquid and solid triglycerides. NMR and solid fat index (SFI) measurements were made on a series of commercial margarine oils of varying composition and consistency. Comparisons are presented giving the precision of the two techniques and the relationship between percentage of solids by the NMR technique and the solids fat index.     

Quantitative assessment of alkyl chain branching in alcohol-based surfactants by nuclear magnetic resonance

Surfactants with branched hydrophobes have gained considerable interest, since these can be used in formulations for laundry cleaning at a wide range of conditions. The claims range from improved dissolution rate to hardness tolerance and stain removing efficacy. In contrast to the historically known heavily branched surfactants, novel branched surfactants are less compromised by increased biodegradability. These properties find their basis in the structural characteristics of the hydrophobe, such as number, position, and type of alkyl chain branches. Our current understanding of structure-property relations, however, is hampered by the lack of generic methodology needed to obtain structural data on hydrophobe branching. A nuclear magnetic resonance (NMR) approach was developed by which we could obtain a comprehensive set of quantitative hydrophobe branching parameters in alcoholbased surfactants. The ¹³C and ¹H NMR spin systems of hydrophobe branched species were assigned by means of twodimensional NMR techniques. These assignments allowed the quantitative assessment of these branched species by straight-forward signal integration in the ¹H and ¹³C NMR spectra. The quantified NMR data can be used to understand product performance and the biodegradation of surfactants with branched hydrophobes.     

A new quantitative method for the analysis of monoacylglycerol isomers using13C nuclear magnetic resonance spectroscopy

Current methods for determining the regiochemistry of monoacylglycerols are lengthy, tedious and aggravated by the ready isomerization of 2-acyl-sn-glycerols. A new method employs a very rapid adsorption chromatography step in which isomerization is kept to a minimum, followed by formation of the isopropylidene derivatives using mild procedures. These cyclic derivatives of 1- and 3-acyl-sn-glycerols and 2-acyl-sn-glycerols are stable thermally and display certain characteristic¹³C NMR resonances. Integration of these resonances yields directly the proportion of monoacylglycerol isomers in the mixture. The method was applied to the analysis of monoacylglycerols produced by enzymatic hydrolysis of synthetic and naturally occurring triacylglycerols. NRCC No. 28475.     

Polymyrcene microstructure revisited from precise high-field nuclear magnetic resonance analysis

The microstructural analysis of 1,4-cis- and of 1,4-trans-polymyrcene was conducted by means of thorough investigations at a very high field NMR (21.1T, 900 MHz). A set of 1D and 2D experiments helped to entirely assign the resonances of the spectra for both stereoisomers. A simple method to distinguish between each stereoisomer by NMR spectroscopy is finally provided.     

Quantitative analysis of oil removal from cotton fabrics through thein situ formation of microemulsions by solid-state nuclear magnetic resonance

Solubilization and subsequent removal of soybean oil from cotton fabrics through thein situ formation of microemulsions were evaluated by solid-state nuclear magnetic resonance (NMR) spectrometry. Regions of water-in-oil and oil-in-water microemulsions were identified for systems that contained polyoxyethylene (60) sorbitol hexaoleate, soybean oil, and an aqueous phase composed of water/ethanol or isopropanol (80:20 wt%) at 25°C. The amount of oil removed from the cotton fabrics was determined by solid-state NMR after constructing a calibration curve relating the intensity of camphor/oil NMR signals (I_c/I_o) to their molar ratio (M_c/M_o). A precision Crockmeter (Mul-Tech Industries, New York, NY) was used to reproducibly remove soybean oil stain from cotton fabric, which was subsequently analyzed by NMR. Typically, more than 90% of the oil stain was removed after 200 revolutions of the Crockmeter finger with 2 wt% surfactant at 25°C. Increasing the amount of surfactant to 6 wt% improved soybean oil removal from the fabric to 99 wt%.     

Two-dimensional nuclear magnetic resonance of resins

A group of resins was synthesised from a series of phenols and aldehydes, and their structures comprehensively deduced from two-dimensional nuclear magnetic resonance spectroscopy (2-D NMR). Correlation spectroscopy, in particular carbon-proton heteronuclear chemical shift correlation spectroscopy, was shown to be especially incisive in assigning structural features to the NMR signals. The method has permitted fuller structural characterisation of these materials than was heretofore possible, and has identified, inter alia, methylene and methyleneoxy bridges unequivocally: complex substitution patterns in the phenol-derived aromatic rings have also been elucidated. It is demonstrably possible to apply the same techniques to similar complex resin structures, and to utilise these structural insights to determine the mechanistic processes involved in their syntheses.     

Quantitative analysis of partial acylglycerols and free fatty acids in palm oil by 13C nuclear magnetic resonance spectroscopy

The chemical shifts, spin-lattice relaxation times (T ₁), and one-bond C−H coupling constants of the glycerol carbons of mono-, di-, and triacylglycerols in CDCI₃ solution are presented and discussed. The glycerol carbons have low T ₁ values (<1.0 s) and full nuclear Overhauser effect and also exhibit broader linewidths than the aliphatic carbons, suggesting that the glycerol carbons are at or near the T ₁ minimum for the dipole-dipole relaxation mechanism. Therefore, for quantitative measurement of the composition of partial acylglycerols (relative to the triacylglycerols) in palm oil, the nuclear magnetic resonance (NMR) spectrum of the β-carbons, which lie exclusively in the region δ68.3–72.1 ppm, should preferably be acquired at medium or low magnetic fields and at an elevated temperature in order to ensure that the condition for extremely narrow spectral lines is satisfied. The chemical shifts and spinlattice relaxation times of the aliphatic C-2 and C-3 carbons and of the carbonyl carbons (C-1) of acyl groups present in palm oil are also presented and discussed. The presence of free fatty acid in the palm oil is easily detected and quantified in the spectrum of the aliphatic carbons. The presence of partial acylglycerols in palm oil can also be detected and/or quantified in the NMR spectra of the C-2 and the carbonyl carbons. The quantitative analysis of the glycerol carbons of a known mixture of acylglycerols obtained by using this method is presented.     

C nuclear magnetic resonance spectral analysis of stereosequences in ethylene-propylene copolymer

A number of split peaks dependent on both comonomer sequences and stereosequences were observed in the ¹³C nuclear magnetic resonance (n.m.r.) spectrum of ethylene-propylene (E-P) copolymer. The ¹³C chemical shifts of methylene carbon in stereoisomers of the respective hexad comonomer sequences were predicted by a chemical-shift calculation using the gamma effect on ¹³C chemical shifts and Mark's rotational isomeric state model for E-P copolymer. Assignments of the split peaks that arise from different hexad stereosequences were given by comparison between the observed and calculated chemical shifts. Reference was made to the hexad assignments of comonomer-sequence-dependent peak splittings determined in our previous calculation of ¹³C n.m.r. chemical shifts of stereoregular E-P copolymers. The tacticities were estimated for successive (not separated by ethylene units) propylene units in the hexad sequences.     

定量核磁共振技术及其在环保型轮胎助剂开发中的应用进展

介绍了欧盟REACH法规对轮胎中多环芳烃(PAHs)含量的限制及所规定的定量核磁共振(QNMR)检测方法对我国合成橡胶工业的影响,综述了QNMR技术的特点、测定PAHs的原理及主要影响参数,提出了QNMR技术在环保轮胎助剂开发中的应用方向。     

Synthesis of acetyl, docosahexaenoyl-glycerophosphocholine and its characterization using nuclear magnetic resonance

Docosahexaenoic acid (DHA) circulates in mammals in lipoproteins and bound to serum albumin as a nonesterified fatty acid as well as esterified in lysophosphatidylcholine (lysoPC). 1-Lyso,2-DHA-glycerophosphocholine (GPC) is an unstable isomer because of a primary alcohol at the sn-1 position. To keep DHA at the sn-2 position of lysoPC, its usual position for the corresponding lysoPC to be acylated into PC in tissues, we synthesized 1-acetyl,2-DHA-GPC and confirmed its structure by use of nuclear magnetic resonance (NMR) spectroscopy in comparison with its positional isomer, 1-DHA,2-acetyl-GPC. 1-Lyso,2-DHA-GPC was prepared from 1-stearoyl,2-DHA-GPC by enzymatic hydrolysis and purified by high-performance liquid chromatography. The isomerization of 1-lyso,2-DHA-GPC into 1-DHA,2-lyso-GPC was obtained by keeping the former overnight at room temperature under nitrogen. Both lysoPC isomers were acetylated by acetic anhydride into 1-acetyl,2-DHA-GPC and 1-DHA,2-acetyl-GPC, respectively, and the resulting phospholipids were fully characterized by NMR. In particular, the 1,2 substitution pattern of the acetyl and DHA chains could be easily detected by 2D heteronuclear multibond correlation. We conclude that 1-acetyl,2-DHA-GPC might be considered as a stable form of 1-lyso,2-DHA-GPC for its delivery to tissues, if the latter exhibits acetyl hydrolase activity.