Removal Of Phospholipids Research Articles

The impact of phospholipids and phospholipid removal on bioanalytical method performance.

Phospholipids (PLs) are a component of cellmembranes, biological fluids and tissues. These compounds are problematic for the bioanalytical chemist, especially when PLs are not the analytes of interest. PL interference with bioanalysis highly impacts reverse-phase chromatographic methods coupled with mass spectrometric detection. Phospholipids are strongly retained on hydrophobic columns, and can cause significant ionization suppression in the mass spectrometer, as they outcompete analyte molecules for ionization. Strategies for improving analyte detection in the presence of PLs are reviewed, including in-analysis modifications and sample preparation strategies. Removal of interfering PLs prior to analysis seems to be most effective atmoderating thematrix effects fromthese endogenous cellular components, and has the potential to simplify chromatography and improve column lifetime. Products targeted at PL removal for sample pre-treatment, as well as products that combine multiplemodes of sample preparation (i.e. Hybrid SPE), show significant promise inmediating the effect on PL interference in bioanalysis.

Development and application of a high-throughput sample cleanup process based on96-well plate for simultaneous determination of 16 steroids in biological matrices using liquid chromatography-triple quadrupole mass spectrometry.

A novel high-throughput sample pretreatment system was developed by the integration of protein precipitation (PP), phospholipid removal (PPR), and hollow fiber liquid-phase microextraction (HF-LPME) into two simple 96-well plates and a matching 96-grid lid. With this system, 16 steroids were separated from biological matrices of plasma, milk, and urine and analyzed by liquid chromatography-triple quadrupole mass spectrometry. In the tandem sample cleanup process, the prepositive PP and PPR step preliminarily removed some of the interferences from the biological matrices. The following HF-LPME step kept the residual interference out of the hollow fiber and enriched the steroids in the hollow fiber to achieve high sensitivity. By a series of method optimizations, acetonitrile was chosen as the crash solvent for PP and PPR. A mixture of octanol and toluene (1:1 v/v) was used as the acceptor phase for HF-LPME. The extraction was conducted at 80 rpm for 50 min in a donor phase containing 1 mL 20% sodium chloride at 25 °C. Under these conditions, the limits of detection for the 16 steroids were 3.6-300.0 pg(.)mL(-1) in plasma, 3.0-270.0 pg·mL(-1) in milk, and 2.2-210.0 pg(.)mL(-1) in urine. The recoveries of the 16 steroids were 81.9-97.9% in plasma (relative standard deviation 1.0-8.0%), 80.6-97.7% in milk (relative standard deviation 0.8-5.4%), and 87.3-98.7% in urine (relative standard deviation 1.0-4.9%). Further, the integrated 96-well platform of PP, PPR, and HF-LPME enabled us to run this assay in an automatic and high-throughput fashion. The reliability of the method was further corroborated by evaluation of its applicability in plasma and urine samples from volunteers and fresh bovine milk from local dairy enterprises.

血清試料からのリン脂質除去が薬物分析の感度及び精度に与える影響

血清試料からのリン脂質除去が薬物分析の感度及び精度に与える影響

High-Throughput Serum 25-Hydroxy Vitamin D Testing with Automated Sample Preparation.

Serum from bar-coded tubes, and then internal standard, are pipetted to 96-well plates with an 8-channel automated liquid handler (ALH). The first precipitation reagent (methanol:ZnSO4) is added and mixed with the 8-channel ALH. A second protein precipitating agent, 1 % formic acid in acetonitrile, is added and mixed with a 96-channel ALH. After a 4-min delay for larger precipitates to settle to the bottom of the plate, the upper 36 % of the precipitate/supernatant mix is transferred with the 96-channel ALH to a Sigma Hybrid SPE(®) plate and vacuumed through for removal of phospholipids and precipitated proteins. The filtrate is collected in a second 96-well plate (collection plate) which is foil-sealed, placed in the autosampler (ALS), and injected into a multiplexed LC-MS/MS system running AB Sciex Cliquid(®) and MPX(®) software. Two Shimadzu LC stacks, with multiplex timing controlled by MPX(®) software, inject alternately to one AB Sciex API-5000 MS/MS using positive atmospheric pressure chemical ionization (APCI) and a 1.87 min water/acetonitrile LC gradient with a 2.1 × 20 mm, 2.7 μm, C18 fused core particle column (Sigma Ascentis Express). LC-MS/MS through put is ~44 samples/h/LC-MS/MS system with dual-LC channel multiplexing. Plate maps are transferred electronically from the ALH and reformatted into LC-MS/MS sample table format using the Data Innovations LLC (DI) Instrument Manager middleware application. Before collection plates are loaded into the ALS, the plate bar code is manually scanned to download the sample table from the DI middleware to the LC-MS/MS. After acquisition-LC-MS/MS data is analyzed with AB Sciex Multiquant(®) software using customized queries, and then results are transferred electronically via a DI interface to the LIS. 2500 samples/day can be extracted by two analysts using four ALHs in 4-6 h. LC-MS/MS analysis of those samples on three dual-channel LC multiplexed LC-MS/MS systems requires 19-21 h and data analysis can be done by two analysts in 4-6 h.

Enzymatic Wheat Germ Oil Degumming

<abstract> Wheat germ oil (WGO) contains significantly higher amounts of phospholipids than commodity oils. The high phospholipid content in WGO adversely affects its appearance and gives it a very dark and cloudy appearance. Previous studies have demonstrated that water and acid degumming, which are commonly used for commodity oils, are not effective for WGO. This study examined the efficiency of enzymatic degumming for removing phospholipids from hexane extracted and mechanically pressed crude WGO. Two enzymes, Lecitase Ultra and Lysomax, were examined. Process variables (water:oil ratio, reaction time, and temperature) were evaluated for high oil yield and low residual phospholipid content in degummed WGO. Degumming with Lecitase Ultra was more effective than Lysomax. Both enzymes, Lecitase Ultra (219 mg kg^-1 residual phosphorus in the oil) and Lysomax (294 mg kg^-1 residual phosphorus), were more effective than water and acid degumming. The oil yields under the conditions that resulted in the highest phospholipid removal (84% to 88% removal) were about 88.7% and 89.6% for Lecitase Ultra and Lysomax, respectively. Significant amounts of tocopherols were lost during enzymatic degumming.

A UPLC-MSMS method for the analysis of olanzapine in serum-with particular emphasis on drug stability testing.

A method including a rapid and automated extraction of olanzapine from serum followed by ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) has been developed and validated. Serum aliquots (100μL) and internal standard (olanzapine-d3, 25μL) were pipetted onto an Ostro(TM) 96-well filtration plate and protein precipitated with acidic acetonitrile (300μL) before removal of endogenous phospholipids by filtration followed by analysis. Chromatography was achieved using an HSST 3 (2.1×100mm, 1.8μm) column and gradient elution with acidic water in combination with methanol at a flow rate of 0.5mL/min. The runtime was 1.5min. The mass spectrometer was monitored in positive mode and multiple reaction monitoring (MRM). The m/z 313.1>256.1 and 313.1>198.0 transitions were monitored for olanzapine (m/z 316.1>256.1 for olanzapine-d3). The quadratic calibration curves ranged from 5 to 500nM (R(2)≥0.999). Limit of quantification was 0.5nM (CV 9.6%, accuracy 110%). Within-assay and between-assay inaccuracies were 2.6-11.9% (CV≤4.8%). Recovery was 84-95% (CV≤1.4%) and matrix effects ranged from 100 to 103% (CV≤2.6%). Extensive stability testing showed that at ambient temperature, olanzapine in patient serum samples were stable for at least seven hours on the laboratory bench and for at least 48h in darkness. When exposed to 3000lux, however, significant degradation had occurred after 48h. Notably, olanzapine in spiked serum was unstable already after four hours when exposed to 3000 lux. At 4-8°C and exposure to 550lux, both patient serum and spiked serum were stable for more than 48h but less than a week, whereas in darkness, the samples were stable for at least 14 days. The cumulative light exposure causing significant degradation of olanzapine in patient serum was 50,000-100,000lux-h. In some individual samples, however, the effect of light exposure was more pronounced. Therefore, it seems pertinent to recommend protecting all samples from light, although we found no indication that a few hours of exposure to standard indoor illumination will affect the olanzapine concentration to any significant degree.

High-level production of Bacillus cereus phospholipase C in Corynebacterium glutamicum

Enzymatic oil degumming (removal of phospholipids) using phospholipase C (PLC) is a well-established and environmentally friendly process for vegetable oil refining. In this work, we report the production of recombinant Bacillus cereus PLC in Corynebacterium glutamicum ATCC 13869 in a high cell density fermentation process and its performance in soybean oil degumming. A final concentration of 5.5g/L of the recombinant enzyme was achieved when the respective gene was expressed from the tac promoter in a semi-defined medium. After treatment with trypsin to cleave the propeptide, the mature enzyme completely hydrolyzed phosphatidylcholine and phosphatidylethanolamine, which represent 70% of the phospholipids present in soybean oil. The results presented here show the feasibility of using B. cereus PLC for oil degumming and provide a manufacturing process for the cost effective production of this enzyme.

Quantitative hydrophilic interaction chromatography-mass spectrometry analysis of N-acetylneuraminic acid and N-acetylmannosamine in human plasma.

N-acetylneuraminic acid (Neu5Ac or NANA) is the most predominant sialic acid in mammals. As a terminal component in many glycoproteins and glycolipids, sialic acid is believed to be an important biomarker related to various diseases. Its precursor, N-acetylmannosamine (ManNAc), is being investigated as a potential treatment for GNE myopathy. In this work, we developed two highly sensitive and selective liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods for the quantitation of ManNAc and free Neu5Ac in human plasma. A fit-for-purpose approach was adopted during method validation and sample analysis. To measure the endogenous compounds and overcome the interference from plasma samples, a surrogate matrix that contained 5% bovine serum albumin (BSA) was used for the preparation of calibration standards and certain levels of quality control (QC) samples. QC samples at higher concentrations were prepared in the authentic matrix (human plasma) to best mimic incurred samples. For both methods, an Ostro 96-well phospholipid removal plate was used for sample extraction, which efficiently removed the phospholipids from the plasma samples prior to LC injection, eliminated matrix effect, and improved sensitivity. Chromatographic separation was achieved using hydrophilic interaction chromatography (HILIC) and gradient elution in order to retain the two polar compounds. The lower limit of quantitation (LLOQ) for ManNAc and Neu5Ac was 10.0 and 25.0ng/mL, respectively. The overall accuracy of the two assays was within 100%±8.3% based on three levels of QC samples. Inter- and intra-run precision (coefficient of variation (%CV)) across three analytical runs was less than 6.7% for ManNAc and less than 10.8% for Neu5Ac. These methods have been validated to support clinical studies.

Development and validation of a liquid chromatography–tandem mass spectrometry method for the quantitative determination of gamithromycin in animal plasma, lung tissue and pulmonary epithelial lining fluid

A sensitive and specific method for the quantitative determination of gamithromycin in animal plasma, lung tissue and pulmonary epithelial lining fluid (PELF) using liquid chromatography combined with heated electrospray ionization tandem mass spectrometry (LC–MS/MS) was developed. The sample preparation was rapid, straightforward and consisted of a deproteinization and phospholipid removal step using an Oasis® Ostro™ 96-well plate (chicken, turkey and calf plasma) or HybridSPE®-Phospholipid SPE cartridges (pig plasma and turkey lung tissue), while a liquid–liquid extraction with diethyl ether in alkaline medium was used for PELF of turkey poults. Chromatography was performed on a C18 Hypersil GOLD column using 0.01M ammonium acetate in water with a pH of 9, and acetonitrile as mobile phases. The MS/MS instrument was operated in the positive electrospray ionization mode and the following selected reaction monitoring transitions were monitored for gamithromycin (protonated molecule>product ion): m/z 777.45>619.35 and m/z 777.45>157.80 for quantification and identification, respectively. The method was validated in-house: matrix-matched calibration graphs were prepared and good linearity (r≥0.99) was achieved over the concentration ranges tested (2.5–10,000ngmL−1 for chicken, pig and calf plasma; 5.0–2500ngmL−1 for turkey plasma; 50–10,000ngg−1 for turkey lung tissue and 20–1000ngmL−1 for turkey PELF). Limits of quantification (LOQ) were 2.5ngmL−1 for chicken, pig and calf plasma and 5.0ngmL−1 for turkey plasma, while the limits of detection (LOD) ranged between 0.007 and 0.07ngmL−1. For lung tissue and PELF, respective LOQ and LOD values of 50ngg−1 and 0.76ngg−1 (lung tissue) and 20ngmL−1 and 0.1ngmL−1 (PELF) were obtained. The results for the within-day and between-day precision, expressed as relative standard deviation (RSD), fell within the maximal RSD values. The accuracy fell within −30% to +10% (concentrations 1–10ngmL−1) or −20% to +10% (concentrations>10ngmL−1 or ngg−1) of the theoretical concentration.The method was successfully applied for the quantitative determination of gamithromycin in plasma samples of chickens, turkeys, pigs and calves; and in lung tissues and PELF of turkeys, all derived from pharmacokinetic studies in these animal species.

The role of tissue thromboplastin in the development of DIC accompanying neoplastic diseases.

Procoagulant activity of gastric cancer tissues and leukocytes obtained from various types of leukemia have been studied with special reference to TTP. The following results were obtained. Homogenates of APL leukocytes and gastric cancer tissues contained strong procoagulant activities, most of which have been identified as TTP since the activities were neutralized by a specific antibody against purified human placenta TTP, inactivated by the removal of phospholipid with heptane-butanol mixture, and inactivated by the addition of phospholipase C. The delipidated homogenates regained procoagulant activities by relipidation procedures. These results also confirmed that TTP from APL leukocytes and gastric cancer tissues have the same lipoprotein properties as those of TTP in normal tissues. Though slight proteolytic activity and fibrinolytic activity were demonstrated in the homogenate of gastric cancer tissues, it was noted that the TTP activity was different from these two activities by partial purification of TTP from gastric cancer tissues. The TTP activity of 9 homogenates of gastric cancer tissues was 301 +/- 289 (mean +/- SD) units per mg protein, being higher in homogenates of mucinous adenocarcinoma and signet-ring cell carcinoma than in those of tubular and poorly differentiated adenocarcinoma. The mean TTP activity of leukocyte homogenates from 14 patients with APL and one out of 4 patients with CML in blastic crisis was 81 +/- 76 units/10(7) cells. The TTP activity of the homogenates of leukocytes from 7 out of 18 patients with AML and another patient with CML in blastic crisis ranged from one to six units/10(7) cells with a mean of 3.3 +/- 1.2. The TTP activity of leukocyte homogenates from the other 11 cases of AML, two cases of CML in blastic crisis, 6 cases of CML, and one case each of ALL and CLL were less than one unit/10(7) cells. In leukemic patients, all cases with a value of more than 202 for the product of units of TTP activity per 10(7) cells and differential count (%) of leukemic cells in the bone marrow smear (MU value) were accompanied by DIC. The MU value of leukemic patients correlated well to the plasma fibrinogen and serum FDP levels. All patients with a MU value of more than 277 died of DIC when a sufficient amount of heparin was not administered. On the other hand, no DIC developed in any of the patients with a MU value of less than 90.(ABSTRACT TRUNCATED AT 400 WORDS)

LC-MS/MS analysis of pramipexole in mouse plasma and tissues: elimination of lipid matrix effects using weak cation exchange mode based solid-phase extraction.

Intranasal delivery is emerging as a promising alternative for oral or intravenous administration of central nervous system (CNS) drugs, such as pramipexole which is widely used for the treatment of Parkinson's disease. To evaluate the effectiveness of intranasal delivery of pramipexole, preclinical pharmacokinetic and tissue distribution studies following intranasal administration need to be investigated. In this paper, we developed and validated a robust and sensitive LC-MS/MS assay without matrix effect for accurate measurements of pramipexole in mouse plasma and tissue samples. Pramipexole and its stable isotope labeled internal standard (d3-pramipexole) were extracted from biological samples by protein precipitation (PPT) coupled with solid phase extraction (SPE) using weak cation exchange SPE cartridges. Matrix effects were studied using post-column infusion and post-extraction addition experiments by direct monitoring of typical phospholipids including glycerophosphocholines (GPChos) and lysoglycerophosphocholines (Lyso-GPChos). Chromatographic separation was achieved on a Welch Ultimate(®) XB-CN column using isocratic elution with a run time of 3.0 min. The assay was linear in the concentration range of 0.05-100 ng/mL and the intra- and inter-day precision and accuracy met the acceptance criteria. Compared with previous reported assays, the current sample preparation approach exhibited significant reduction of matrix effects due to the dramatically decreased levels of residual matrix components such as GPChos and Lyso-GPChos. This method has been successfully applied to pharmacokinetic and tissue distribution studies of pramipexole in mice following a single intravenous or intranasal dose of 50 μg/kg.

Quantitation of ethyl glucuronide in serum & urine by gas chromatography - mass spectrometry.

Alcohol misuse has now become a serious public health problem and early intervention is important in minimizing the harm. Biochemical markers of recent and high levels of alcohol consumption can play an important role in providing feedback regarding the health consequences of alcohol misuse. Existing markers are not sensitive to recent consumption and in detecting early relapse. Ethyl glucuronide (EtG), a phase-II metabolite of ethanol is a promising marker of recent alcohol use and can be detected in body fluids. In this study an analytical technique for quantitation of EtG in body fluids using solid-phase extraction (SPE) and gas chromatography (GC) with mass spectrometric detection (MS) was developed and validated. De-proteinization of serum and urine samples was done with perchloric acid and hydrochloric acid, respectively. Serum samples were passed through phospholipids removal cartridges for further clean up. EtG was isolated using amino propyl solid phase extraction columns. Chromatographic separation was achieved by gas chromatography with mass spectrometry. Limit of detection and limit of quantitation were 50 and 150 ng/ml for urine and 80 and 210 ng/ml for serum, respectively. Signal to noise ratio was 3:1, mean absolute recovery was 80-85 per cent. Significant correlation was obtained between breath alcohol and serum EtG levels (r=0.853) and urine EtG and time since last abuse (r = -0.903) in clinical samples. In the absence of other standardized techniques to quantitate EtG in biological samples, this gc - ms method was found to have high throughput and was sensitive and specific.

Enzymatic Degumming of Crude Jatropha Oil: Evaluation of Impact Factors on the Removal of Phospholipids

AbstractJatropha curcas seeds are rich in non‐edible oil, and this plant has received much interest in recent years, especially with respect to biodiesel production. Owing to the high content of phospholipids, crude jatropha oil has to be refined before further use. Conventional refining processes have several environmental and energetic shortcomings. Thus, the search for alternative degumming methods has become relevant. This study compares the enzymatic degumming of screw‐pressed crude jatropha oil with Lecitase Ultra (phospholipase A1) and LysoMax (phospholipase A2). Degumming with phospholipase A2 was less effective that degumming with phospholipase A1. Phospholipase A1 showed the highest reaction rate at 50 °C, 700 rpm stirring, 3 mL of water per 100 g of oil, and with 75 ppm of added phospholipase. To ensure optimum enzyme activity, the pH was adjusted to 5. The phosphorus content was reduced continuously for reaction times up to 3 h. The residual phosphorus content was found to be independent of its initial level. Laboratory experiments showed that enzymatic degumming of jatropha oil with phospholipase A1 at the adapted parameters enables the phosphorus content to be reduced to levels below 4 ppm.

Development of an extraction and purification method for the determination of multi-class pharmaceuticals and endocrine disruptors in freshwater invertebrates

Aquatic organisms from freshwater ecosystems impacted by waste water treatment plant (WWTP) effluents are constantly exposed to constant concentrations of pharmaceuticals, endocrine disruptors and related compounds, among other anthropogenic contaminants. Macroinvertebrates inhabiting freshwater ecosystems might be useful bioindicators of exposure to contaminants, since their lives are long enough to bioaccumulate, but at the same time may integrate short-term changes in the environment. However, studies about potential bioaccumulation of emerging contaminants in these organisms are very scarce. The objectives of this study were to develop an analytical methodology for the analysis of 41 pharmaceuticals and 21 endocrine disruptors in freshwater invertebrates. In addition, bioaccumulation of these contaminants in three macroinvertebrate taxa inhabiting a waste water treatment plant -impacted river was evaluated. The method for the simultaneous extraction of both families of compounds is based on sonication, purification via removal of phospholipids, and analysis by ultra performance liquid chromatography coupled to a mass spectrometer (UPLC–MS/MS) in tandem. Recoveries for pharmaceuticals were 34–125%, and for endocrine disruptors were 48–117%. Method detection limits (MDLs) for EDCs were in the range of 0.080–2.4ngg−1, and for pharmaceuticals, 0.060–4.3ngg−1. These pollutants were detected in water samples taken downstream the waste water treatment plant effluent at concentrations up to 572ngL−1. Two non-esteroidal anti-inflammatory drugs, diclofenac and ibuprofen, and four endocrine disruptors – estrone, bisphenol A, TBEP, and nonylphenol – were detected in at least one macroinvertebrate taxa in concentrations up to 183ngg−1 (dry weight). An isobaric interference was identified during the analysis of diclofenac in Hydropsyche samples, which was successfully discriminated via accurate mass determination by TFC-LTQ Orbitrap.

Phospholipid removal combined with a semi-automated 96-well SPE application for determination of budesonide in human plasma with LC–MS/MS

A semi-automated method for quantification of budesonide in human plasma was developed, validated, and applied for high-volume analysis of samples in connection with a pharmacokinetic study. Protein and phospholipid removal was performed using an Ostro 96-well filter plate and subsequently combined with C18 solid-phase extraction on a Hamilton Microlab STARlet automation robot. The final extracts were evaporated to dryness and redissolved in 20% acetonitrile/water. The procedure used budesonide-d8 as internal standard and gave a 3.5-fold concentration of plasma to extract. The final extracts (5 μL injected) were analyzed with selected reaction monitoring liquid chromatography-tandem mass spectrometry (LC-MS/MS) using electrospray ionization in positive mode. The chromatography system used a 100 mm ACQUITY BEH UPLC column and a gradient system consisting of aqueous 0.1% formic acid and acetonitrile as organic modifier. Phospholipid removal was found to be needed during method development in order to reduce ion suppression effects from matrix and to increase method sensitivity. The measuring range was 50-5000 pg/mL with and LOD 24 pg/mL. Calibration response showed good linearity (correlation coefficients<0.99) over the measuring range. The absolute recovery over the sample preparation procedure was estimated to 67%. Total imprecision was <9% at three levels and accuracy was between 98.9 and 103%. The method was successfully applied for analysis of 864 study samples in a short time. The quality control samples at concentration levels 200 and 2000 pg/mL gave a total imprecision of 7.4% and 4.2%, respectively, (n=95).

Quantitative determination of 26 steroids in eggs from various species using liquid chromatography–triple quadrupole-mass spectrometry

A method for analyzing 26 types of steroids in egg matrix was developed. The method used liquid chromatography coupled with tandem mass spectrometry (LC–MS/MS) in electrospray ionization mode (ESI). The procedure involved extraction with acetonitrile and removal of phospholipids by zinc chloride (ZnCl2) followed by SPE cleanup with a Plexa cartridge. The effect of ZnCl2 on phospholipid removal was directly observed using the post column infusion procedure. The SPE washing and elution conditions were optimized using a shallow gradient procedure. The free and conjugated steroids forms were determined using enzyme hydrolysis. The developed method resulted in satisfactory precision (RSD≤15%), and the limits of quantification were between 0.05 and 25ng/g depending on the steroid types. The recoveries ranged from 63.2% to 121.5%. Finally, the developed method was successfully applied to compare the steroids in eggs from different species (i.e., hen, duck, quail and pigeon eggs) or different raising system (i.e., normal vs. organic eggs). The steroids can be clearly clustered according to species and raising system. The hierarchical clustering analysis indicated similarity of the steroids among the species. The developed method is sensitive and useful for detection and quantification of steroids in eggs and can be used for residue control programs. In addition, the observed steroid content will provide a fundamental reference for food risk assessment analysis.

Optimal Conditions to Remove Chemical Hazards in Fish Protein Isolates from Tilapia Frame Using Response Surface Methodology

Response surface methodology (RSM) was employed to maximize the removal of phospholipids (PLs) and other chemical hazards in tilapia protein isolates made from tilapia frame (TF). CaCl2 and the ratio of water to minced tilapia frame (W:TF) were the significant variables affecting PLs reduction. The optimum condition for maximal PLs reduction (90.0%) was: 10.25 mM CaCl2 and a W:TF of 7.8:1, while other variables were fixed at 5 mM citric acid, 60 min incubation, pH 11, and centrifugal speed of 8,000 × g. At these conditions, the great reduction of lipids (93.9%), Hg (97.6%), and As (95.5%), as well as 86.1% of protein recovery, were obtained. Protein isolates with significantly reduced chemical hazards and lipids were successfully prepared from tilapia frames using the alkaline extraction assisted with CaCl2 and citric acid.

Matrix Effects in Metabolite Quantification for Mist Assessment: The Impact of Phospholipid Removal and HPLC Column Particle Size

This Research article investigates the impact of phospholipid removal and high-performance liquid chromatography column particle size on the accuracy of determining the relative abundance of human metabolites using mass spectrometry peak areas in the context of assessing metabolite abundance for Metabolites in Safety Testing assessment. RESULTS/METHODOLOGY: Plasma samples spiked with 20 compounds, representing ten pairs of drugs and metabolites, were prepared using phospholipid removal plates (Ostro™) or standard protein precipitation techniques and analyzed by liquid chromatography-tandem mass spectrometry using high-performance liquid chromatography columns containing either 2.5 or 3.5 µm particles. Removal of phospholipids significantly reduced matrix effects for samples analyzed on the larger particle size columns while preventing phospholipid build up on the analytical columns. In addition, quantitative accuracy and linearity were not affected by phospholipid removal. Both sample preparation strategies and column particle sizes should be considered in order to reduce the inaccuracy as a result of matrix effects in assessing metabolite abundance using mass spectrometry peak areas.

Evidence for the presence of lipid-free monomolecular apolipoprotein A-1 in plasma

The first step in reverse cholesterol transport is a process by which lipid-free or lipid-poor apoA-1 removes cholesterol from cells through the action of ATP binding cassette transporter A1 at the plasma membrane. However the structure and composition of lipid-free or -poor apoA-1 in plasma remains obscure. We previously obtained a monoclonal antibody (MAb) that specifically recognizes apoA-1 in preβ1-HDL, the smallest apoA-1-containing particle in plasma, which we used to establish a preβ1-HDL ELISA. Here, we purified preβ1-HDL from fresh normal plasma using said antibody, and analyzed the composition and structure. ApoA-1 was detected, but neither phospholipid nor cholesterol were detected in the purified preβ1-HDL. Only globular, not discoidal, particles were observed by electron microscopy. In nondenaturing PAGE, no difference in the mobility was observed between the purified preβ1-HDL and original plasma preβ1-HDL, or between the preβ1-HDL and lipid-free apoA-1 prepared by delipidating HDL. In sandwich ELISA using two anti-preβ1-HDL MAbs, reactivity with intact plasma preβ1-HDL was observed in ELISA using two MAbs with distinct epitopes but no reactivity was observed in ELISA using a single MAb, and the same phenomenon was observed with monomolecular lipid-free apoA-1. These results suggest that plasma preβ1-HDL is lipid-free monomolecular apoA-1.

Removal of Endogenous Phospholipids of Rhodobacter Sphaeroides Cytochrome C Oxidase affects the Flexibility of the Enzyme

The crystal structure of cytochrome c oxidase (COX) from Rhodobacter sphaeroides shows two phospholipids intercalated inside subunit III and four at the interface between subunits I, III and IV. These phospholipids are necessary for electron transfer, but their exact function in the structure of COX is still unclear.Phospholipids were removed from COX by incubation with molar stoichiometric amounts of phospholipase A2 for 3 hours at 4 °C in 20 mM MOPS pH 7.2, 20 mM CaCl2 and 0.2 % dodecyl maltoside. The enzyme was then washed on a cytochrome c-affinity column; phosphorous, iron and copper content was determined by inductively coupled plasma-mass spectrometry. Wild-type enzyme contained an average of 5 moles phosphorous per mole enzyme, while the delipidated enzyme contained less than one. Electron transfer activity in the treated enzyme was decreased 30% and it exhibited suicide inactivation. Inhibition of electron transfer activity and suicide inactivation were reversed by the addition of 1 mg/ml asolectin. The time dependence of α-chymotrypsin digestion of the enzyme showed that subunit I was digested at a faster rate in the delipidated COX, suggesting a more open conformation in the lipid-depleted COX. To further assess COX conformational flexibility upon delipidation, both COX forms were labeled in subunit III with a sulfhydryl group-directed fluorophore, N-iodoacetylamindoethyl-1-aminonaphthalene-5-sulfonate (IAEDANS). Fluorescence anisotropy measurements showed a 50% increase in the rotational rate of AEDANS-labeled delipidated COX. This increase in flexibility of subunit III affects the flexibility of the adjacent subunit I as shown by the higher chymotrypsin digestion rate of subunit I in the delipidated enzyme. Taken together, these data provide an explanation of the low turnover rates and suicide inactivation, both of which occur in COX in the absence of phospholipids.