Solubility determination and thermodynamic model analysis of L-α-glyceryl phosphorylcholine in different organic solvents of 278.15 K to 323.15 K

L-α-glyceryl phosphorylcholine, also referred to as choline ethanol phosphate and phosphocholine glycerophosphate, is a naturally occurring metabolite of water-soluble phospholipids in animals. This molecular property is important for informing the crystallization and purification of drugs. The solubility of L-α-glyceryl phosphorylcholine was determined in ten pure solvents and three mixed solvents under atmospheric pressure. The experimental results indicate that L-α-glyceryl phosphorylcholine is most soluble in methanol and least soluble in acetone. Additionally, the solubility of L-α-glyceryl phosphorylcholine was found to increase with temperature within the experimental range. Furthermore, the solubility of L-α-glyceryl phosphorylcholine in binary solvents is dependent on the proportion of positive solvent and temperature. The solubility of L-α-glyceryl phosphorylcholine increases with the proportion of positive solvent. XRD and DSC results indicate that the crystal form of L-α-glyceryl phosphorylcholine remains unchanged before and after dissolution in the reagent, and its melting point temperature is 413.15 K. Various models, including the modified Apelblat model, λh model, Jouyban-Acree model, SUN model, and CNIBS/R-K model, were used to fit the solubility data of L-α-glyceryl phosphorylcholine in different solvents. The study found that the modified Apelblat model and CNIBS/R-K model were the most appropriate for fitting the data. The KAT-LSER model was used to analyze the molecular interactions between solvents and solutes, revealing that the solvent step method with non-specific polarity/polarization interaction had the greatest impact on solubility.

Effects of the Molecular Structure of Malodor Substances and Their Masking on 1,2-Dioleoyl-sn-glycero-3-phosphocholine Molecular Layers

Certain odors have been shown not only to cause health problems and stress but also to affect skin barrier function. Therefore, it is important to understand olfactory masking to develop effective fragrances to mask malodors. However, olfaction and olfactory masking mechanisms are not yet fully understood. To understand the mechanism of the masking effect that has been studied, the responses of several target substance (TS) molecules-1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) mixed molecular layers to odorant (OD) molecules were examined as a simple experimental model of epithelial cellular membranes injured by TS molecules. Here, we examined trans-2-nonenal, 1-nonanal, trans-2-decenal, and 1-decanal as TS molecules to clarify the effects of double bonds and hydrocarbon chain lengths on the phospholipid molecular layer. In addition, benzaldehyde and cyclohexanecarboxaldehyde were utilized as OD molecules to clarify the masking effect of the aromatic ring. Surface pressure (Π)-area (A) isotherms were measured to clarify the adsorption or desorption of TS and OD molecules on the DOPC molecular layer. In addition, Fourier transform infrared spectroscopy was performed to clarify the interactions among DOPC, TS, and OD molecules. We found that TS molecules with and without double bonds had different effects on the DOPC molecular layer and that molecules with shorter chain lengths had greater effects on the DOPC molecular layer. Furthermore, OD molecules with aromatic rings counteracted the effects of the TS molecules. On the basis of this research, not only a detailed mechanism by which odor molecules affect lipid membranes without mediating olfactory receptors is elucidated but also more effective OD molecules with masking effects are proposed.

Associations of dietary choline and betaine with all-cause mortality: a prospective study in a large Swedish cohort

PURPOSE

Investigate the association between choline and betaine intake and all-cause mortality in a large Swedish cohort.

METHODS

Women (52,246) and men (50,485) attending the Västerbotten Intervention Programme 1990-2016 were included. Cox proportional hazard regression models adjusted for energy intake, age, BMI, smoking, education, and physical activity were used to estimate mortality risk according to betaine, total choline, phosphatidylcholine, glycerophosphocholine, phosphocholine, sphingomyelin, and free choline intakes [continuous (per 50 mg increase) and in quintiles].

RESULTS

During a median follow-up of 16 years, 3088 and 4214 deaths were registered in women and men, respectively. Total choline intake was not associated with all-cause mortality in women (HR 1.01; 95% CI 0.97, 1.06; P = 0.61) or men (HR 1.01; 95% CI 0.98, 1.04; P = 0.54). Betaine intake was associated with decreased risk of all-cause mortality in women (HR 0.95; 95% CI 0.91, 0.98; P < 0.01) but not in men. Intake of free choline was negatively associated with risk of all-cause mortality in women (HR 0.98; 95% CI 0.96, 1.00; P = 0.01). No other associations were found between intake of the different choline compounds and all-cause mortality. In women aged ≥ 55 years, phosphatidylcholine intake was positively associated with all-cause mortality. In men with higher folate intake, total choline intake was positively associated with all-cause mortality.

CONCLUSION

Overall, our results do not support that intake of total choline is associated with all-cause mortality. However, some associations were modified by age and with higher folate intake dependent on sex. Higher intake of betaine was associated with lower risk of all-cause mortality in women.

Plasma metabolomic profile in orthostatic intolerance children with high levels of plasma homocysteine

BACKGROUND

Orthostatic intolerance, which includes vasovagal syncope and postural orthostatic tachycardia syndrome, is common in children and adolescents. Elevated plasma homocysteine levels might participate in the pathogenesis of orthostatic intolerance. This study was designed to analyze the plasma metabolomic profile in orthostatic intolerance children with high levels of plasma homocysteine.

METHODS

Plasma samples from 34 orthostatic intolerance children with a plasma homocysteine concentration > 9 µmol/L and 10 healthy children were subjected to ultra-high-pressure liquid chromatography and quadrupole-time-of-flight mass spectrometry analysis.

RESULTS

A total of 875 metabolites were identified, 105 of which were significantly differential metabolites. Choline, 1-stearoyl-2-linoleoyl-sn-glycero-3-phosphocholine, 1-(1Z-octadecenyl)-2-(4Z,7Z,10Z,13Z,16Z,19Z-docosahexaenoyl)-sn-glycero-3-phosphocholine, histidine, isocitric acid, and DL-glutamic acid and its downstream metabolites were upregulated, whereas 1-palmitoyl-sn-glycero-3-phosphocholine, 1-stearoyl-sn-glycerol 3-phosphocholine, sphingomyelin (d18:1/18:0), betaine aldehyde, hydroxyproline, and gamma-aminobutyric acid were downregulated in the orthostatic intolerance group compared with the control group. All these metabolites were related to choline and glutamate. Heatmap analysis demonstrated a common metabolic pattern of higher choline, 1-stearoyl-2-linoleoyl-sn-glycero-3-phosphocholine, and DL-glutamic acid, and lower sphingomyelin (d18:1/18:0), 1-stearoyl-sn-glycerol 3-phosphocholine, and 1-palmitoyl-sn-glycero-3-phosphocholine in patients with certain notable metabolic changes (the special group) than in the other patients (the common group). The maximum upright heart rate, the change in heart rate from the supine to the upright position, and the rate of change in heart rate from the supine to the upright position of vasovagal syncope patients were significantly higher in the special group than in the common group (P < 0.05). Choline, 1-stearoyl-2-linoleoyl-sn-glycero-3-phosphocholine, and DL-glutamic acid were positively correlated with the rate of change in heart rate from the supine to the upright position in vasovagal syncope patients (P < 0.05).

CONCLUSIONS

The levels of choline-related metabolites and glutamate-related metabolites changed significantly in orthostatic intolerance children with high levels of plasma homocysteine, and these changes were associated with the severity of illness. These results provided new light on the pathogenesis of orthostatic intolerance.

Effects of grafted polymers on the lipid membrane fluidity

Since the membrane fluidity controls the cellular functions, it is important to identify the factors that determine the cell membrane viscosity. Cell membranes are composed of not only lipids and proteins but also polysaccharide chain-anchored molecules, such as glycolipids. To reveal the effects of grafted polymers on the membrane fluidity, in this study, we measured the membrane viscosity of polymer-grafted giant unilamellar vesicles (GUVs), which were prepared by introducing the poly (ethylene glycol) (PEG)-anchored lipids to the ternary GUVs composed of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), and cholesterol. The membrane viscosity was obtained from the velocity field on the GUV generated by applying a point force, based on the hydrodynamic model proposed by Henle and Levine. The velocity field was visualized by a motion of the circular liquid ordered (Lo) domains formed by a phase separation. With increasing PEG density, the membrane viscosity of PEG-grafted GUVs increased gradually in the mushroom region and significantly in the brush region. We propose a hydrodynamic model that includes the excluded volume effect of PEG chains to explain the increase in membrane viscosity in the mushroom region. This work provides a basic understanding of how grafted polymers affect the membrane fluidity.

Effect of γ-Oryzanol on the LE-LC Phase Coexistence Region of DPPC Langmuir Monolayer

We have studied the effect of relative composition of γ-Oryzanol (γ-Or) on the liquid expanded-liquid condensed phase coexistence region in the mixed Langmuir monolayer of γ-Or and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) molecules at air-water interface. The surface manometry studies at a fixed temperature show that the mixture of γ-Or and DPPC forms a stable monolayer at air-water interface. As the relative composition of γ-Or increases the range of area per molecule over which the coexistence of liquid expanded (LE)-liquid condensed (LC) phases exists reduces. Although the LE-LC phase coexistence corresponds to the first-order phase transition, the slope of the surface pressure-area per molecule isotherm is non-zero. Earlier studies have attributed the non-zero slope in LE-LC phase coexistence region to the influence of the strain between the ordered LC phase and disordered LE phase. The effect of strain on the coexistence of LE-LC phases can be studied in terms of molecular density-strain coupling. Our analysis of the liquid condensed-liquid expanded coexistence region in the isotherms of mixed monolayers of DPPC and γ-Or shows that with the increase in the mole fraction of sterol in the mixed monolayer the molecular lateral density-strain coupling increases. However, at 0.6 mole fraction of γ-Or in the mixed monolayer the coupling decreases. This is corroborated by the observation of minimum Gibb's free energy of the mixed monolayer at this relative composition of γ-Or indicating better packing of molecules.

Unraveling Complex Hysteresis Phenomenon in 1,2-Dipalmitoyl-sn-Glycero-3-Phosphocholine Monolayer: Insight into Factors Influencing Surface Dynamics

This study explores the hysteresis phenomenon in DPPC (1,2-dipalmitoyl-sn-glycero-3-phosphocholine) monolayers, considering several variables, including temperature, compression and expansion rates, residence time, and subphase content. The investigation focuses on analyzing the influence of these variables on key indicators such as the π-A isotherm curve, loop area, and compression modulus. By employing the Langmuir-Blodgett technique, the findings reveal that all the examined factors significantly affect the aforementioned parameters. Notably, the hysteresis loop, representing dissipated energy, provides valuable insights into the monolayer's viscoelasticity, molecular packing, phase transition changes, and resistance during the isocycle process. These findings contribute to a comprehensive understanding of the structural and dynamic properties of DPPC monolayers, offering insights into their behavior under varying conditions. Moreover, the knowledge gained from this study can aid in the development of precise models and strategies for controlling and manipulating monolayer properties, with potential applications in drug delivery systems, surface coatings, as well as further investigation into air penetration into alveoli and the blinking mechanism.

Spin-Labeled Diclofenac: Synthesis and Interaction with Lipid Membranes

Diclofenac is a non-steroidal anti-inflammatory drug (NSAID) from the group of phenylacetic acid derivatives, which has analgesic, anti-inflammatory and antipyretic properties. The interaction of non-steroidal anti-inflammatory drugs with cell membranes can affect their physicochemical properties, which, in turn, can cause a number of side effects in the use of these drugs. Electron paramagnetic resonance (EPR) spectroscopy could be used to study the interaction of diclofenac with a membrane, if its spin-labeled analogs existed. This paper describes the synthesis of spin-labeled diclofenac (diclofenac-SL), which consists of a simple sequence of transformations such as iodination, esterification, Sonogashira cross-coupling, oxidation and saponification. EPR spectra showed that diclofenac-SL binds to a lipid membrane composed of palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC). 2H electron spin echo spectroscopy (ESEEM) was used to determine the position of the diclofenac-SL relative to the membrane surface. It was established that its average depth of immersion corresponds to the 5th position of the carbon atom in the lipid chain.

Changes of serum metabolites levels during neoadjuvant chemoradiation and prediction of the pathological response in locally advanced rectal cancer

INTRODUCTION

Previous studies have explored prediction value of serum metabolites in neoadjuvant chemoradiation therapy (NCRT) response for rectal cancer. To date, limited literature is available for serum metabolome changes dynamically through NCRT.

OBJECTIVES

This study aimed to explore temporal change pattern of serum metabolites during NCRT, and potential metabolic biomarkers to predict the pathological response to NCRT in locally advanced rectal cancer (LARC) patients.

METHODS

Based on dynamic UHPLC-QTOF-MS untargeted metabolomics design, this study included 106 LARC patients treated with NCRT. Biological samples of the enrolled patients were collected in five consecutive time-points. Untargeted metabolomics was used to profile serum metabolic signatures from LARC patients. Then, we used fuzzy C-means clustering (FCM) to explore temporal change patterns in metabolites cluster and identify monotonously changing metabolites during NCRT. Repeated measure analysis of variance (RM-ANOVA) and multilevel partial least-squares discriminant analysis (ML-PLS-DA) were performed to select metabolic biomarkers. Finally, a panel of dynamic differential metabolites was used to build logistic regression prediction models.

RESULTS

Metabolite profiles showed a clearly tendency of separation between different follow-up panels. We identified two clusters of 155 serum metabolites with monotonously changing patterns during NCRT (74 decreased metabolites and 81 increased metabolites). Using RM-ANOVA and ML-PLS-DA, 8 metabolites (L-Norleucine, Betaine, Hypoxanthine, Acetylcholine, 1-Hexadecanoyl-sn-glycero-3-phosphocholine, Glycerophosphocholine, Alpha-ketoisovaleric acid, N-Acetyl-L-alanine) were further identified as dynamic differential biomarkers for predicting NCRT sensitivity. The area under the ROC curve (AUC) of prediction model combined with the baseline measurement was 0.54 (95%CI = 0.43 ~ 0.65). By incorporating the variability indexes of 8 dynamic differential metabolites, the prediction model showed better discrimination performance than baseline measurement, with AUC = 0.67 (95%CI 0.57 ~ 0.77), 0.64 (0.53 ~ 0.75), 0.60 (0.50 ~ 0.71), and 0.56 (0.45 ~ 0.67) for the variability index of difference, linear slope, ratio, and standard deviation, respectively.

CONCLUSION

This study identified eight metabolites as dynamic differential biomarkers to discriminate NCRT-sensitive and resistant patients. The changes of metabolite level during NCRT show better performance in predicting NCRT sensitivity. These findings highlight the clinical significance of metabolites variabilities in metabolomics analysis.

The effect of chitosan/TiO2/hyaluronic acid subphase on the behaviour of 1,2-dioleoyl-sn-glycero-3-phosphocholine membrane

The main aim of the study was to determine the effect of two polysaccharides: chitosan (Ch) and hyaluronic acid (HA), and/or titanium dioxide (TiO₂) on the structure and behaviour of the 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) membrane. To achieve this goal the surface pressure as a function of the area per molecule (π-A) isotherm for the phospholipid monolayer was recorded. The shape of the π-A isotherms and compression-decompression cycles, as well as the compression modulus values, were analysed in terms of biocompatibility. Besides, morphology and thickness of the phospholipid layers obtained by means of Brewster angle microscope at different π, were determined. The obtained results show that both polysaccharides Ch, HA, as well inorganic TiO₂ affect slightly the structure of the DOPC monolayer but do not disrupt it. Their presence brings no typical arrangements of both the polar heads and tails of DOPC molecules at the interface.

Fluidity-Guided Assembly of Au@Pt on Liposomes as a Catalase-Powered Nanomotor for Effective Cell Uptake in Cancer Cells and Plant Leaves

The fluidity of the liposomes is essential to nanoparticle-membrane interactions. We herein report a liposomal nanomotor system by controlling the self-assembly behavior of gold core-platinum shell nanoparticles (Au@Pt) on liposomes. Au@Pt can aggregate immediately on fluid-phase dioleoyl-sn-glycero-3-phosphocholine (DOPC) liposomes, forming an uneven distribution. By control of the lipid phase and fluidity, either using pure 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) above its phase transition temperature or adding cholesterol as an adjuvant to DPPC lipids, we precisely control the assembly of Au@Pt on liposomes. Au@Pt maintained high catalase-like activity on the liposomal surface, promoting the decomposition of H₂O₂ and the movement of the liposomal nanomotors. Finally, we demonstrate that liposomal nanomotors are biocompatible and they can speed up the cellular uptake in mammalian HepG2 cancer cells and Nicotiana tabacum (Nb) plant leaves. This liposomal nanomotor system is expected to be further investigated in biomedicine and plant nanotechnology.

Pretreatment optimization of tissue metabolomics in colorectal cancer

BACKGROUND AND OBJECTIVES

To optimize the pretreatment method of colorectal cancer tissue samples for metabolomics research based on solid-phase nuclear magnetic resonance (NMR).

METHODS AND STUDY DESIGN

The mucosal tissues of colorectal cancer were classified into five groups with a volume of 0.2 cm*0.2 cm*0.2 cm. The pretreatment methods for each group were as follows: I. Preservation with liquid nitrogen alone. Samples were also treated with liquid nitrogen for 10 (II), 20 (III), and 30 min (IV), respectively, immediately after isolation and then transferred to a -80℃ refrigerator; V. Only -80℃ refrigerator storage. No more than 30 minutes should pass between isolation and pretreatment of tumor samples. The tissue sample testing process was carried out on Bruker AVII-600 NMR Spectrometer. NMR signals were collected and analysed using partial least-squares discrimination analysis (PLS-DA) to explore the effects of different pretreatment methods on the metabolic changes of samples.

RESULTS

The levels of pelargonic acid, stearic acid, D-Ribose, heptadecanoic acid, pyruvic acid, succinate, sarcosine, glycine, creatine, and L-lactate in the group I (only liquid nitrogen) were significantly lower than the other groups (p<0.05); the content of glycerophosphocholine in the group I (only liquid nitrogen) was lower than that in the other groups (p=0.055). These indicated that the glucose and choline phospholipid metabolism levels of the liquid nitrogen group were significantly lower than those of the other four groups.

CONCLUSIONS

Liquid nitrogen storage can stop the metabolic process of glucose and choline phospholipid in colorectal cancer tissue samples in vitro, thus maintaining the metabolic state of tissue samples in vivo as much as possible.

Proton-decoupled 31P MRS in untreated pediatric brain tumors

Proton-decoupled (31)P and (1)H MRS was used to quantify markers of membrane synthesis and breakdown in eight pediatric patients with untreated brain tumors and in six controls. Quantitation of these compounds in vivo in humans may provide important indicators for tumor growth and malignancy, tumor classification, and provide prognostic information. The ratios of phosphoethanolamine to glycerophosphoethanolamine (PE/GPE) and phosphocholine to glycerophosphocholine (PC/GPC) were significantly higher in primitive neuroectodermal tumors (PNET) (16.30 +/- 5.73 and 2.97 +/- 0.93) when compared with controls (3.42 +/- 1.62, P < 0.0001 and 0.45 +/- 0.13, P < 0.0001) and with other tumors (3.93 +/- 3.42, P < 0.001 and 0.65 +/- 0.30, P < 0.0001). Mean PC/PE was elevated in tumors relative to controls (0.48 +/- 0.11 versus 0.24 +/- 0.05, P < 0.001), but there was no difference between PNET and other tumors. Total choline concentration determined with quantitative (1)H MRS was significantly elevated (4.78 +/- 3.33 versus 1.73 +/- 0.56 mmol/kg, P < 0.05), whereas creatine was reduced in tumors (4.89 +/- 1.83 versus 8.28 +/- 1.50 mmol/kg, P < 0.05). A quantitative comparison of total phosphorylated cholines (PC+GPC)/ATP measured with (31)P MRS and total choline measured with (1)H MRS showed that in tumors a large fraction of the choline signal (>54 +/- 36%) was not accounted for by PC and GPC. The fraction of unaccounted choline was particularly large in PNET (>78 +/- 7%). The pH of tumor tissue was higher than the pH of normal brain tissue (7.06 +/- 0.03 versus. 6.98 +/- 0.03, P < 0.001).

Acceleration of phosphatidylcholine synthesis and breakdown by inhibitors of mitochondrial function in neuronal cells: a model of the membrane defect of Alzheimer's disease

Brain cells in Alzheimer's disease (AD) exhibit a membrane defect characterized by accelerated phospholipid turnover. The mechanism responsible for this defect remains unknown. Recent studies indicate that impairment of mitochondrial function is frequently observed in AD and may be responsible for certain aspects of its pathophysiology. We show that when PC12 cells are exposed to inhibitors of mitochondrial bioenergetics, the turnover of their major membrane phospholipid, phosphatidylcholine, is accelerated, producing a pattern of metabolic changes that mimics that observed in brains of AD patients. Abnormalities of mitochondrial function may therefore underlie the membrane defect in AD.

Physical property analysis and bacterial adhesion on a series of phosphonated polyurethanes

Glycerophosphorylcholine (GPC) was incorporated as the chain extender in a series of poly(tetramethylene oxide)-based polyurethane block copolymers. In order to determine the feasibility of use of these polyurethanes in biomedical devices, the effects of GPC incorporation on physical properties were studied. The effect of soft-segment molecular weight was also investigated. Biocompatibility of these materials was studied with regard to bacterial adhesion and protein deposition. Tensile testing showed that as GPC content increased, elongation at break decreased, while Young's modulus increased. Differential scanning calorimetry (DSC) results showed slightly decreased glass transition temperatures (Tgs) with increasing GPC content, indicating increased phase separation. Dynamic mechanical analysis (DMA) confirmed the decrease in Tg and the increase in rubbery plateau modulus with increasing GPC content. Water absorption was also increased with GPC content. Decreased bacterial adhesion was found on the GPC-containing materials compared to other functionalized polyurethanes. These experiments were carried out in a radial flow chamber utilizing automated video microscopy. Bacterial attachment was found to be lower on the GPC-containing polyurethanes both in the absence of and after pre-adsorption with plasma proteins.

Convenient synthesis of racemic mixed-chain ether glycerophosphocholines from fatty alkyl allyl ethers: useful analogs for biophysical studies

Diether glycerophosphocholines containing one long and one short chain were synthesized in moderate yield. The synthesis of a diether glycerophosphocholine containing a branched chain and a straight chain is also described. Alkylation of fatty alcohol with allyl bromide and dimethyl sulfoxide anion gave fatty alkyl allyl ether, which was hydroxylated and tritylated. By procedures described previously, 1-O-alkyl-3-O-triphenyl-methylglycerol was alkylated, detritylated, and converted into the phosphocholine product. This method is of general utility for the preparation of a variety of mixed-chain racemic glycerophosphocholines whose physical properties are of interest in studies of biological membranes.

Effect of water on the molecular structure of a phosphatidylcholine hydrate. Raman spectroscopic analysis of the phosphate, carbonyl and carbon-hydrogen stretching mode regions of 1,2-dipalmitoylphosphatidylcholine dihydrate

The Raman spectra of 1,2-dipalmitoylphosphatidylcholine (DPPC) dihydrate crystals were examined in (a) the 1250 and 1080 cm-1 PO-2 antisymmetric and symmetric stretching mode regions, (b) the 1730 cm-1 carbonyl stretching mode region and (c) the 2800-3100 cm-1 C-H stretching mode interval. No evidence was observed for hydrogen bonding effects involving the nonester phosphate oxygen atoms. Spectra of the DPPC dihydrate crystal in the 1250 cm-1 region are compared to spectra of both anhydrous and successively hydrated systems and to spectra of crystalline glycerylphosphorylcholine. The splitting pattern in the 1240 to 1280 cm-1 interval for the DPPC dihydrate was interpreted in terms of the different bonding arrangements assumed by the PO-2 groups in the two molecule asymmetric unit of the eight molecule unit cell. An unusual triplet is observed in the carbonyl stretching mode region around 1730 cm-1. These features reflect differing bond environments, relative to the polar and hydrophobic regions of the bilayer, of the 1- and 2-chain carbonyl groups. Spectra for crystalline DPPC dihydrate in the 3000 cm-1 C-H stretching mode region suggest a hybrid chain packing lattice which is analogous to the packing arrangement determined for the isostructurally similar DMPC dihydrate species.

Facile acylation of glycerophosphocholine catalyzed by trifluoroacetic anhydride

A simplified procedure for the synthesis of short acyl chain phosphatidylcholines is described. A mixed fatty acid-trifluoroacetic anhydride is used to acylate sn-glycero-3-phosphocholine (GPC) which has been dissolved in trifluoroacetic acid. Yields exceeding 70% are achieved in 30-min reaction time using 1.5 to 2.0 equivalents of mixed anhydride per, GPC hydroxyl. This allows a more economical use of labeled short chain acids.

Synthesis of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine with labeled acyl groups

A facile procedure for the small scale chemical synthesis of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPL) is reported. Under optimal conditions, 36% of the sn-glycero-3-phosphocholine was converted to DPL. This procedure is suitable for small scale preparation of DPL with very high specific radioactivity from labeled palmitic acid. Furthermore, the labeled DPL obtained will serve as precursor for the chemical or enzymatic synthesis of other labeled phospholipids.

Stereochemical substrate requirements of lecithin:cholesterol acyltransferase and its inhibition by enantiomeric lysolecithins

The suitability of 1-sn-phosphorylcholine- and 2-sn-phosphorylcholine-diacylglycerols as substrates for lecithin:cholesterol acyltransferase (LCAT) was assayed under standardized conditions using sonicated liposomes of radioactive phospholipids. The results were compared with those obtained for the corresponding molecular species of the natural 3-sn-phosphorylcholinediacylglycerol. It was found that with the 2-sn-phosphorylcholinediacylglycerol, LCAT had only 16% of the activity that it showed for 3-sn-phosphorylcholinediacylglycerol, while its activity with 1-sn-phosphorylcholinediacyglycerol as the substrate was not significant. It is concluded that LCAT possesses highly specific steric and positional requirements for its phosphatidylcholine substrates and that, like phospholipase A2, it has a significant activity with the 2-sn-phosphorylcholinedicacylglycerol. It wa also shown that the activity of LCAT is inhibited by both enantiomers of lysophosphatidylcholine as well as Triton X-100. In all instances the inhibition was reversed by the addition of lipid-free albumin. It is concluded, therefore, that the inhibition of LCAT by lysophosphatidylcholine is a detergent rather than an end-product inhibition phenomenon.

A convenient synthesis of phosphatidylcholines: acylation of sn-glycero-3-phosphocholine with fatty acid anhydride and 4-pyrrolidinopyridine

A high-yield synthesis of saturated, unsaturated, and short chain phosphatidylcholines from sn-glycero-3-phosphocholine is described. The procedure offers advantages over other reported procedures for the synthesis of phosphatidylcholine in that the large-scale synthesis and purification can be achieved in a minimum time. The procedure utilizes 4-pyrrolidinopyridine as a catalyst and moderate amounts of fatty acid anhydride (2 mol eq. of fatty acid anhydride per mol of OH) in a 1:1 mixture of benzene-dimethylsulfoxide (DMSO) at 40 degrees--42 degrees C (oilbath) for 2--5 hr. At the end of the reaction, the phosphatidylcholine can be purified in the usual manner or by using a Waters Prep LC/500 with a radially compressed silica gel column eluted with chloroform-methanol-water 60:30:4. At a flow rate of 200 ml/min, the phospholipid elutes in 10--15 min, depending on the chain length and unsaturation.

The role of antiandrogenic action in cyproterone acetate-induced morphologic and biochemical changes in human semen

Following the daily administration of 10 mg of cyproterone acetate to three normal fertile human volunteers for 12 to 16 weeks, there was a marked decrease in the count, motility, and cervical mucus-penetrating ability of spermatozoa, with a concomitant increase in abnormal and immature forms. The levels of seminal acid phosphatase and glycerylphosphoryl choline were also significantly decreased. Subsequently, concurrent daily administration of 75 mg of mesterolone increased the count, motility, and cervical mucus-penetrating ability of spermatozoa and stimulated the seminal biochemical constituents. The results indicate that the effects of a low dose of cyproterone acetate are due mainly to peripheral androgen deprivation.

Preferential interaction of pentagastrin with the gel state of dimyristoyl glycerophosphocholine

Fluorescence and circular dichroism spectra indicate that pentagastrin interacts with dimyristoyl glycerophosphocholine more strongly below the phase transition temperature of the lipid than above it. Studies on the interaction of several peptides with dimyristoyl glycerophosphocholine suggest that this property may be related to the ability of these peptides to form amphipathic structures containing two hydrophobic amino acids separated by two other amino acids. Pentagastrin has a marked effect on the proton magnetic resonance spectra of dipalmitoyl glycerophosphocholine below the phase transition temperature indicating the the peptide decreases the motional freedom of the lipid.

An improved method for the preparation of unsaturated phosphatidylcholines: acylation of sn-glycero-3-phosphorylcholine in the presence of sodium methylsulfinylmethide

An improved method for the partial chemical synthesis of unsaturated and radioactively labeled phosphatidylcholines is described. This procedure offers advantages over conventional acylation methods in that it can be carried out on a millimole or micromole scale under mild conditions and it does not require a large excess of the fatty acid acylating reagent. In this procedure sn-glycero-3-phosphorylcholine is reacted with twice the theoretical amount of fatty acid imidazolide and sodium methylsulfinylmethide in dimethylsulfoxide for several minutes at 17 degrees C. Phosphatidylcholine, which was purified by gradient-elution chromatography on silicic acid, was isolated in 60% yield and was estimated to be about 99% pure. The preparations of 1,2-dioleoyl-, 1,2-dilinoleoyl-, and 1,2-dilinolenoyl-sn-glycero-3-phosphorylcholine are described. The reaction was also carried out on a small scale for the preparation of high specific activity 1,2-di[ 1'(-14)C]oleoyl-sn-glycero-3-phosphorylcholine in 38% yield with a specific activity of about 9.7 muCi/mumol.

Orientation and flexibility of the choline head group in phosphatidylcholine bilayers

The average orientation and flexibility of the phosphorylcholine group are deduced from deuterium and phosphorus-31 nuclear magnetic resonance measurements of unsonicated phosphatidylcholine bilayers in the liquid crystalline state. The experimental data are consistent with a model in which the polar head group exhibits a restricted flexibility characterized by rapid transitions between two enantiomeric conformations. A completely flexible or a completely rigid head group structure can be excluded. The phosphorylcholine residue is found to be bent at the position of the phosphate group, due to a gauche-gauche conformation of the phosphodiester linkage. The choline dipole is aligned parallel to the plane of the membrane, which is in agreement with X-ray and neutron diffraction studies. The average orientation of the phosphorylcholine group is therfore the same as that of the phosphorylethanolamine head group.

Interaction of glucagon with dimyristoyl glycerophosphocholine

Glucagon can form amphipathic helices and can interact with dimyristoyl glycerophosphocholine at temperatures below the phase transition leading to a shift in the fluorescence emission maximum of tryptophan from 350 to 338 nm and a 3-fold enhancement of fluorescence intensity as well as a change in the polarization of fluorescence. The circular dichroism properties of the lipid-associated glucagon indicates that it has an increased content of alpha-helix. The phase transition temperature of the lipid as monitored by pyrene excimer fluorescence is not altered by interaction with glucagon although at higher glucagon/lipid ratios a decrease in excimer formation is noted at low temperature. Above the phase transition temperature, the addition of lipid has no effect on the fluorescence emission or circular dichroism of glucagon. Thus this hormone can interact with dimyristoyl glycerophosphocholine and this interaction is stronger below the phase transition temperature than above it.

An analysis of the X-ray interchain peak profile in dipalmitoylglycerophosphocholine

The primary X-ray peak profile characterizing the interchain structure in the dipalmitoylglycerophosphocholine membrane has been measured as a function of temperature. The scattering between 23 and 34.6 degrees C is characterized by an asymmetric crystalline reflection accounting for 85% of the total intensity, the remaining 15% being liquid-like in character. At a pre-transition temperature of 34.6 degrees C, the reflection profile becomes (nearly) symmetrical, indicating a change in tilt angle of the chains with respect to the membrane surface. This change is accompanied by an increase of 20% in the amount of liquid-like scattering, indicating that the pre-transition mechanism includes a partial melting of the chains. At the melting point, 41.5 degrees C, the crystalline reflection disappears, and the liquid component of the scattering increases to a point where it includes all the scattered intensity. The relative values of the integrated intensities at each temperature are tabulated, and the significance of the peak widths and shapes are discussed.

A novel pathway for phosphatidylcholine catabolism in rat brain homogenates

Rat brain homogenates incubated with exogenous [32-P] phosphatidylcholine liberated: LYSO[32-P] phosphatidylcholine, sn-glycero-3-[32-P] phosphorylcholine, [32-P] phosphorylcholine, sn-gleycero-3-[32-P] phosphate and 32-Pi. Further investigation showed that [32-P] phosphorylcholine was released exclusively from sn-glycero-3-[32-P] phosphorylcholien by a novel diesterase activity. We propose that the enzyme be termed L-3-glycerylphosphinicocholine cholinephosphohydrolase (EC 3.1.4.-). Parallel experiments on rat liver homogenates and a P815Y mouse mastocytoma cell-lysate, revealed no diesterase activity.

Separation of 1-acylglycerolphosphate acyltransferase and 1-acylglycerolphosphorylcholine acyltransferase of rat liver microsomes

1-Acylglycerolphosphate acyltransferase (Ec 2.3.1-) and 1-acylglycerolphosphorylcholine acyltransferase (EC 2.3.1.23) of rat liver microsomes were separated from each other. The separation was achieved by sucrose density gradient centrifugation of the enzyme preparation that was obtained by solubilizing microsomes with a nonionic detergent, Triton X-100, and subjecting the solubilized microsomes to molecular-sieve chromatography. The two acyltransferases are distinguishable from each other also with respect to their stabilities to heat and to Triton X-100. Hence, it is concluded that these acyltransferases are distinct enzymes. These results, together with our previous finding that glycerolphosphate acyltransferase is also a separate enzyme, demonstrate the presence of distinct acyltransferases responsible for the acylation of the different acyl acceptors. Furthermore, the acyl-donor specificities of these acyltransferases provide the enzymatic basis for the nonrandom distribution of fatty acids in naturally occurring glycerolipids.

Enzymes of phospholipid metabolism in the plasma membrane of Acanthamoeba castellanii

Phospholipase A, lyophospholipase, acyl CoA hydrolase, and palmitoyl CoA synthetase are present in the plasma membrane of Acanthamoeba castellanii. The first three of these enzymes also occur in other cell fractions but in concentrations too low for the activities in the plasma membrane fraction to be accounted for by contamination by any other cell fraction. Palmitoyl CoA synthetase is restricted almost entirely to the plasma membrane and microsomal fractions; the microsomal activity is too low for the plasma membrane activity to be due to contamination by microsomes. Acyl COA:lysolecithin acyltransferase is predominantly localized in the microsomal fraction, but the activity of the plasma membrane is probably too great to be accounted for by microsomal contamination. CDPcholine:1,2-diglyceride cholinephosphotransferase is restricted almost entirely to the microsomal fraction. Phospholipase C was not detected in any cell fraction or in the growth medium.

A comparison of D-inositol 1:2-cyclic phosphate 2-phosphohydrolase with other phosphodiesterases of kidney

1. The ability to hydrolyse various phosphodiesterase substrates was examined in subcellular fractions of rat kidney and in serial slices of the kidneys of mouse, rat, guinea pig and ox cut from the cortex perimeter inwards. 2. d-Inositol 1:2-cyclic phosphate 2-phosphohydrolase could be clearly distinguished from phosphodiesterases which hydrolyse 2':3'- and 3':5'-cyclic AMP and p-nitrophenyl thymidine 5'-phosphate (phosphodiesterase I). The hydrolysis of sn-glycero-3-phosphorylcholine showed a distribution identical with that of particle-bound d-inositol 1:2-cyclic phosphate 2-phosphodiesterase, but there was a 30-fold difference in the ratio of enzyme activities between the rat and guinea pig. 3. In rat and mouse kidney, d-inositol 1:2-cyclic phosphate 2-phosphohydrolase is virtually all membrane bound and in the outer cortex, whereas in guinea-pig kidney the enzyme is almost entirely soluble and located throughout the kidney tissue. Some properties of the soluble enzyme are described. 4. Distribution and histochemical studies indicated that in the rat and mouse, phosphodiesterase I is associated with the brush borders of the straight portion (pars recta) of the proximal tubule, whereas inositol 1:2-cyclic phosphate 2-phosphohydrolase and probably glycerylphosphorylcholine diesterase are associated with the brush borders of the convoluted part of the tubule (pars convoluta).