Oxidation of glycerophospholipids from biological membranes by reactive oxygen species: liquid chromatographic-mass spectrometric analysis of eicosanoid products.

Peroxidation of glycerophospholipids present in cellular membranes results in the formation of a complex mixture, with many products derived from the oxidation of esterified arachidonic acid. Techniques of chromatography and mass spectrometry have facilitated the elucidation of the structure of individual components present as intact glycerophospholipids as well as the oxidized fatty acyl groups liberated from the glycerol backbone by saponification. Previously reported studies are summarized in this overview concerning those oxidized products of arachidonic acid derived from the red blood cell membrane, studied by techniques of electrospray tandem mass spectrometry developed to analyze eicosanoid products.     

Blood phenylalanine monitoring for dietary compliance among patients with phenylketonuria: comparison of methods

PurposeBlood phenylalanine monitoring is critical for the management of phenylketonuria. We compared three methods for measuring blood phenylalanine concentration: the amino acid analyzer, high-performance liquid chromatography with fluorometric detection, and tandem mass spectrometry.MethodsWe studied 22 female patients with phenylketonuria, ages 12–48 years, who attended our Metabolic Camp. Blood was collected into heparinized tubes (for analysis by the amino acid analyzer) or filter paper (for analysis by high-performance liquid chromatography with fluorometric detection and tandem mass spectrometry).ResultsBlood phenylalanine concentrations of plasma measured by the amino acid analyzer were significantly higher than those obtained from whole blood on filter paper by high-performance liquid chromatography (difference: 102 μM; 95% confidence interval: 23, 181) and tandem mass spectrometry (difference: 137 μM; 95% confidence interval: 58, 216). Phenylalanine concentrations from high-performance liquid chromatography and tandem mass spectrometry were not significantly different (P = 0.5).ConclusionsWhen monitoring blood phenylalanine concentrations for dietary compliance, clinicians should be mindful of the method being used; analyses of whole blood on filter paper were consistently approximately 15% lower than analyses of plasma.     

串联质谱技术在脂肪酸氧化代谢病诊断中的应用研究

目的探讨利用串联质谱技术检测干血滤纸片中酰基肉碱水平,诊断脂肪酸氧化代谢病。方法对象为2941例临床遗传性代谢病高危儿童,利用串联质谱技术检测患儿干血滤纸片中酰基肉碱水平,结合临床资料和常规生化结果,进行脂肪酸氧化代谢病诊断。结果诊断了14例脂肪酸氧化代谢病(0.5%),其中肉碱棕榈酰转移酶Ⅰ缺乏症1例,肉碱棕榈酰转移酶Ⅱ缺乏症1例,短链酰基辅酶A脱氢酶缺乏症1例,中链酰基辅酶A脱氢酶缺乏症7例,极长链酰基辅酶A脱氢酶缺乏症2例,多种酰基辅酶A脱氢酶缺乏症2例。结论通过串联质谱技术检测干血滤纸片中酰基肉碱水平,可对部分脂肪酸氧化代谢病进行诊断。     

Detection and identification of morphine in urine extracts using thin-layer chromatography and tandem mass spectrometry.

The application of tandem mass spectrometry to the analysis and identification of morphine following thin-layer chromatography is described. FAB-mass spectrometry and mass spectrometry-mass spectrometry were performed following chromatography on silica gel high-performance thin-layer chromatography plates. The successful application of this simple methodology to a urine extract suggests that this approach has practical utility for confirming the identity of abused drugs detected by thin-layer chromatography.     

Glutaric aciduria type 2 and newborn screening: commentary

Glutaric aciduria type 2 is increasingly being identified through expanded newborn screening programs by tandem mass spectrometry with a goal of decreasing morbidity and mortality. This article presents 3 patients with adverse outcomes in spite of early recognition by newborn screening. Additional long term studies are necessary to determine the efficacy of newborn screening to affect outcome in this disorder.     

Newborn screening

The aim of newborn screening is to detect newborns with serious, treatable disorders so as to facilitate appropriate interventions to avoid or ameliorate adverse outcomes. Mass biochemical testing of newborn babies was pioneered in the 1960s with the introduction of screening for phenylketonuria, a rare inborn error of metabolism, tested by using a dried blood spot sample. The next disorder introduced into screening programs was congenital hypothyroidism and a few more much rarer disorders were gradually included. Two recent advances have greatly changed the pace: modification of tandem mass spectrometry and DNA extraction and analysis from newborn screening dried blood spot. These two technologies make the future possibilities of newborn screening seem almost unlimited. Newborn screening tests are usually carried out on a dried blood spot sample, for which there are special analytical considerations. Dried blood spot calibrators and controls, prepared on the same lot number of filter paper, are needed. Methods have a co-efficient of variation of about 10% due to the increased variability of a dried filter paper sample compared with other biochemical samples. The haematocrit is an additional variable not able to be measured. Also of importance is obtaining a balance between the sensitivity and specificity of each assay. Fixing cut-off points for action needs consideration of what is an acceptable percentage of the population to recall for further testing. Few assays are 100% discriminatory. Programs in Australasia currently screen for at least 30 disorders. Detection of these requires not only the assay of a primary marker but often determination of a ratio of that marker with another, or possibly an alternative assay, for example a DNA mutation. The most important disorders screened for are described briefly: phenylketonuria, primary congenital hypothyroidism, cystic fibrosis, the galactosaemias, medium-chain acyl-CoA dehydrogenase deficiency, glutaryl-CoA dehydrogenase deficiency and congenital adrenal hyperplasia, together with several other disorders detectable by tandem mass spectrometry. Newborn screening deals with rare disorders and benefit cannot be shown easily without very large pilot studies. There have been randomised controlled trials of screening for cystic fibrosis, and now several studies are beginning to establish the benefit of tandem mass spectrometry screening for disorders of fatty acid and amino acid metabolism. Two things will influence the new directions for newborn screening: the development of effective treatments for hitherto untreatable disorders, and advancing technology, enabling new testing strategies to be developed. There are novel treatments on the horizon for many discrete disorders. Susceptibility testing has recently been considered for newborn screening application, but is more controversial. Newborn screening has entered a new and exciting phase, with an explosion of new treatments, new technologies, and, possibly in the future, new preventive strategies.     

Electrospray mass spectrometry for the identification of MHC class I-associated peptides expressed on cancer cells

Electrospray ionisation (ESI) mass spectrometry (MS) has been used extensively for the detection of peptides presented by major histocompatibility complex (MHC) molecules. This review focuses on the optimisation of electrospray mass spectrometry and the use of tandem mass spectrometry to sequence MHC class I peptides. We review the isolation of MHC class I peptides from the surface of cells with particular reference to tumour cells. In addition, we also discuss the advantages and disadvantages of the methods available to concentrate and fractionate the peptides prior to analysis by electrospray mass spectrometry.     

激光显微切割联合质谱分析继发淀粉样变性患者肾组织SAA蛋白

目的利用激光显微切割联合质谱(LMD/MS)技术分析强直性脊柱炎(AS)合并继发性淀粉样变患者肾活检组织标本血清淀粉样物质A(SAA)蛋白亚型及氨基酸突变序列。方法甲醛固定肾活检组织,脱蜡后行刚果红染色,选取刚果红染色阳性区域进行质谱分析,通过数据分析软件对质谱结果进行整合评估,并将患者SAA蛋白氨基酸序列与变异蛋白数据库氨基酸序列进行比对确定是否有变异蛋白。结果质谱鉴定到高丰度的SAA1及SAA2蛋白,同时有血清淀粉样蛋白P及载脂蛋白E,数据库比对未检测到SAA1及SAA2蛋白的变异序列。结论本研究首次鉴定到了AS合并淀粉样变肾组织中的SAA1及SAA2蛋白,丰富了AS淀粉样变的发病机制,为将来AA型淀粉样变性的精准分型提供新的方法。     

Expanded newborn screening identifies maternal primary carnitine deficiency

Primary carnitine deficiency impairs fatty acid oxidation and can result in hypoglycemia, hepatic encephalopathy, cardiomyopathy and sudden death. We diagnosed primary carnitine deficiency in six unrelated women whose unaffected infants were identified with low free carnitine levels (C0) by newborn screening using tandem mass spectrometry. Given the lifetime risk of morbidity or sudden death, identification of adult patients with primary carnitine deficiency is an added benefit of expanded newborn screening programs.     

基质辅助激光解吸/离子化飞行时间质谱分析多态性遗传标记

随着人类基因组测序工作的完成，多态性遗传标记及其检测手段日益受到重视。基质辅助激光解吸／离子化飞行时间质谱作为一种高通量的单核苷酸多态性分型技术受到关注，它不仅可以分析单核苷酸多态性，还可以进行微测序、分析短串联重复序列。目前的分析方法有：引物延伸法、连接酶反应法、肽核酸法、侵入法等。     

线粒体脂肪酸β-氧化障碍的研究新进展

脂肪酸是机体在饥饿、应激等状态下通过线粒体内的β-氧化为机体提供能量的主要来源。线粒体中存在着催化脂肪酸氧化的多种酶,近年来研究已发现在脂肪酸β-氧化过程有20余种参与的活性酶,相应酶的活性缺陷导致临床一系列脂肪酸氧化障碍。在脂肪酸β-氧化过程易出现障碍的环节主要涉及到脂肪酸和肉碱转运障碍,各种酰基辅酶A脱氢酶缺陷,线粒体基质内β-氧化所需的各种酶的功能障碍,酮体生成障碍等。临床上常表现为低血糖,心肌病,肌张力低下,酸中毒,猝死,脑病等症状。随着串联质谱技术在高危新生儿遗传代谢病筛查中的应用,使得此类疾病能够得到快速准确的诊断,做到早期发现,早期治疗,从而明显的改善疾病的预后。     

Diagnosing lysosomal storage diseases in a Brazilian non-newborn population by tandem mass spectrometry

OBJECTIVES:

High-throughput mass spectrometry methods have been developed to screen newborns for lysosomal storage disorders, allowing the implementation of newborn screening pilot studies in North America and Europe. It is currently feasible to diagnose Pompe, Fabry, Gaucher, Krabbe, and Niemann-Pick A/B diseases, as well as mucopolysaccharidosis I, by tandem mass spectrometry in dried blood spots, which offers considerable technical advantages compared with standard methodologies. We aimed to investigate whether the mass spectrometry methodology for lysosomal storage disease screening, originally developed for newborns, can also discriminate between affected patients and controls of various ages.

METHODS:

A total of 205 control individuals were grouped according to age and subjected to mass spectrometry quantification of lysosomal α-glucosidase, β-glucocerebrosidase, α-galactosidase, acid sphingomyelinase, galactocerebrosidase, and α−L-iduronidase activities. Additionally, 13 affected patients were analyzed.

RESULTS:

The median activities for each enzyme and each age group were determined. Enzyme activities were significantly lower in individuals aged older than 18 years compared with those in newborns. Affected patients presented enzymatic activities corresponding to less than 20% of the age-matched controls.

CONCLUSIONS:

Our data indicate that the mass spectrometry methodology can be used for the screening of lysosomal storage diseases in non-newborn patients. However, for some diseases, such as Fabry and mucopolysaccharidosis I, a combination of biochemical and clinical data may be necessary to achieve accurate diagnoses.     

Citrin缺陷致新生儿肝内胆汁淤积症患儿生化改变研究

目的探讨citrin缺陷致新生儿肝内胆汁淤积症（NICCD）患儿生化改变特征。方法对经基因学确诊且平均月龄为3个月的26例NICCD患儿进行常规生化检查、气相色谱质谱检查及串联质谱检查并分析。结果 NICCD患儿血清总胆红素、直接胆红素、谷草转氨酶、谷丙转氨酶及乳酸水平升高均占100%,血氨及甲胎蛋白水平升高均占95.2%,胆汁酸水平升高占90.0%,低蛋白水平占84.0%,血脂水平升高占50%。半乳糖增高占78.3%,4-羟基苯乳酸增高占52.2%。C14增高占84.7%,C16增高占71.4%,瓜氨酸增高占66.7%。结论 NICCD患儿存在糖,氨基酸及脂肪酸代谢异常,以半乳糖、瓜氨酸及长链酰基肉碱增高明显。     

Effect of sports activity on carnitine metabolism. Measurement of free carnitine, gamma-butyrobetaine and acylcarnitines by tandem mass spectrometry.

The effects of sports activity on carnitine metabolism were studied using mass spectrometry. Serum levels of free carnitine, acylcarnitines (acetylcarnitine, propionylcarnitine, C4-, C5- and C8-acylcarnitine) and gamma-butyrobetaine, a carnitine precursor, were determined by tandem mass spectrometry in liquid secondary ion mass ionization mode. The coefficients of variation at three different concentrations were 2.8-7.9% for gamma-butyrobetaine, and 1.2 to approximately 6.7% for free carnitine. The recoveries added to serum were 109.1% for gamma-butyrobetaine, 89.3% for free carnitine. Sports activity caused increased serum levels of gamma-butyrobetaine, acetylcarnitine, C4- and C8-acylcarnitines and decreased serum levels of free carnitine. This method requires a small amount of sample volume (20 microl of serum) and short total instrumental time for the analysis (1 h for preparation, 2 min per sample for mass spectrometric analysis). Therefore, this method can be applied to study carnitine metabolism under various conditions that affect fatty acid oxidation.     

Measurement of carnitine precursors, epsilon-trimethyllysine and gamma-butyrobetaine in human serum by tandem mass spectrometry.

Methods using tandem mass spectrometry for measurement of epsilon-trimethyllysine and gamma-butyrobetaine in human serum are described. Precursor ion scan analysis of a methylated sample was applied for gamma-butyrobetaine measurement. However, for epsilon-trimethyllysine measurement, homoarginine interfered with the methylated sample during precursor ion scan analysis. To overcome this interference, the sample was propylated and acetylated prior to precursor ion scan analysis. The obtained values resembled those obtained by enzymatic or HPLC measurement. Using tandem mass spectrometry, all members of the carnitine family, free carnitine, acylcarnitines, gamma-butyrobetaine, epsilon-trimethyllysine can be analyzed in 0.1 ml of serum. Thus, the proposed method appears to be suitable for clinical application, especially in the pediatric field.     

The use of post-source decay in matrix-assisted laser desorption/ionisation mass spectrometry to delineate T cell determinants

The identification of naturally processed peptides presented by molecules of the major histocompatibility complex (MHC) has progressed significantly over the past decade. The elution of peptides from immunoaffinity purified complexes of MHC class I or class II molecules has provided highly specific biochemical information regarding the nature of endogenous peptides capable of binding to and being presented by particular MHC alleles. Whilst Edman chemistry is sufficient for the identification of abundant or homogeneous immunodominant peptides contained in samples of fractionated peptides, mass spectrometry has proved more powerful for sequencing less abundant species present in the typically heterogeneous fractions of eluted peptides. This review focuses on the characterisation of T cell determinants by matrix-assisted laser desorption/ionisation (MALDI)-time-of-flight (TOF) mass spectrometry (MS). We demonstrate, with specific examples, the utility of post-source decay in MALDI-TOF MS for the characterisation of the amino acid sequences of both native and modified T cell determinants. The potential advantages and pitfalls of this technique relative to the more commonly used forms of tandem mass spectrometry in electrospray and ion spray modes of ionisation as well as hybrid quadrupole-quadrupole-TOF instruments are discussed. We highlight the complementarity between these techniques and discuss the advantages in the combined use of both MALDI- and electrospray-based instrumentation in epitope identification strategies.     

Human catalytic RNA- and DNA-hydrolyzing antibodies

Sequencing of anti-vancomycin monoclonal antibody (mAb) Fab region (48,000 Da) was carried out using liquid chromatography–electrospray ionization ion trap mass spectrometry (LC/ESI-MS). Comprehensive strategies were employed to ensure complete sequence coverage. The sequence information was obtained from the spectra of collision-induced dissociation (CID) (MS/MS) of the protonated proteolytic peptides resulting from multiple enzymatic digestions of reduced/S-carboxymethylated (RCM) light chain and Fd fragment. Database searching of the spectra against the published immunoglobulin G (IgG) sequences allowed the identification of all the peptides in constant domains as well as partial sequences in variable domains. The rest of the sequences were deduced by manual interpretation of the peptide tandem mass spectrometry (MS/MS) spectra. The analysis showed that the N-terminus of the heavy chain was modified by the conversion of a glutamine residue to pyroglutamic acid.     

Determination of clindamycin in human plasma by liquid chromatography-electrospray tandem mass spectrometry: application to the bioequivalence study of clindamycin

A simple, sensitive and specific liquid chromatography-electrospray tandem mass spectrometry (LC-MS-MS) method for the determination of clindamycin (I) was developed. Both I and verapamil (II, internal standard) were analyzed using a C18 column with a mobile phase of 80% acetonitrile-0.01% trifluoroacetic acid. Column eluents were monitored by electrospray tandem mass spectrometry. Multiple reaction monitoring (MRM) using the parent to daughter combinations of m/z 425-->126 and 455-->165 was used to quantitate I. A limit of quantitation of 0.0500 microgram/ml was found. The assay exhibited a linear dynamic range of 0.0500-20.0 micrograms/ml and gave a correlation coefficient (r2) of 0.998 or better. The chromatographic run time was approximately 2 min. The intra-batch precision and accuracy of the quality controls (QCs, 0.0500, 0.150, 1.50, 15.0 and 20.0 micrograms/ml) were characterized by coefficients of variation (CVs) of 5.13 to 13.7% and relative errors (REs) of -4.34 to 4.58%, respectively. The inter-batch precision and accuracy of the QCs were characterized by CVs of 4.35 to 8.32% and REs of -10.8 to -4.17%, respectively. The method has successfully been applied to the analysis of samples taken up to 12 h after oral administration of 300 mg of I in healthy volunteers.     

大鼠脊髓源神经干细胞与运动神经元的差异蛋白质组学

目的 探讨大鼠脊髓源神经干细胞与运动神经元的差异蛋白质组学,寻找出重要的差异蛋白质.方法 采用双向电泳分离两种细胞的蛋白质,用DeCyder软件分析蛋白表达差异,并采用质谱(HPLC-ESI-MS/MS)进行鉴定.结果 脊髓源神经干细胞与运动神经元蛋白质凝胶分析获得1 300余个清晰的蛋白质斑点,在比国产分析的87个差异点中,初步鉴定出44个差异表达蛋白,其中24个在神经干细胞高表达,20个在运动神经元高表达.结论 脊髓源神经干细胞与运动神经元有各自特定的蛋白质表达,某些差异蛋白可能在神经干细胞向运动神经元分化中发挥关键作用.     

高效液相色谱-串联质谱法测定人血浆盐酸伪麻黄碱浓度

目的 建立一种高效液相色谱-质谱联用技术（LC-MS/MS）测定人血浆盐酸伪麻黄碱浓度的方法。方法 血浆样品经液液萃取后,以甲醇∶水∶甲酸（60∶40∶1,V/V/V）为流动相,流速0.35 ml/min,采用Cap cell pack C18色谱柱分离,150 mm×2.1 mm, 5 μm（USA）;柱温20℃,选择离子喷雾离子化源串联质谱,通过正离子方式检测;选择反应监测（MRM）方式转化m/z=166.3/148.2（盐酸伪麻黄碱）和m/z= 152.2/134.15（内标苯丙醇胺）进行定量分析,用内标法测定含量。结果 伪麻黄碱浓度分别在5.0~400.0 ng/ml的范围内线性良好,R=0.9962,最低检测限为1.0 g/ml。结论 本方法操作简便、快速,结果准确,可用于该药物的含量测定,同时也可为临床药动学研究提供一定的参考。