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Analysis of C19O3 steroids by thin-layer and gas-liquid chromatography and mass spectrometry.

The separation of twenty-six saturated and two unsaturated C19O3 steroids has been studied by thin-layer chromatography on silica gel F254, with seven mobile phases, and by gas-liquid chromatography on packed columns with four stationary phases; combination of both techniques permitted separation of all the test compounds. The mass spectra of the steroids were obtained by gas chromatography-mass spectrometry and are presented. Fragmentation processes have been studied, and characteristic ions that may be used for multiple ion detection or lead to identification of biologically produced C19O3 steroids are discussed.

Androstanes↗

Separation and characterization of the reduced metabolites of the 18-hydroxydeoxycorticosterone hormone by gas-liquid chromatography-mass spectrometry. Occurrence of stereoisomeric forms in rat adrenals and liver.

In order to study the metabolism of 18-OH-11-deoxycorticosterone, the mineralocorticoid hormone responsible for hypertension in rats and humans, we have synthesized the following dihydrogenated and tetrahydrogenated reference derivatives: 18,21-dihydroxy-5alpha-pregnane-3,20-dione, 18,21-dihydroxy-5beta-pregnane-3,20-dione, 3alpha,18,21-trihydroxy-5alpha-pregnan-20-one (I), 3beta,18,21-trihydroxy-5alpha-pregnan-20-one (II), 3alpha,18,21-trihydroxy-5beta-pregnan-20-one (III) and 3beta,18,21-trihydroxy-5beta-pregnan-20-one (IV). A complete separation of these compounds from each other and from tetrahydrocorticosterone isomers has been realized only by the association of thin-layer chromatography and gas-liquid chromatography on high-efficiency glass capillary columns. Characterization by gas-liquid chromatography-mas spectrometry is described. The stereoisomer distribution in rats is: adrenals of adult males and females (compounds I and II in the ratio 4:1); adrenals of 23-day-old males and females (compounds I, II and III, 11:11:3); liver of females (compound I and traces of III); and the liver of adult male (compounds II, III and IV, 4.5:4.5:1).

18-Hydroxydesoxycorticosterone↗

Fractionation of low-molecular-mass heparin by centrifugal partition chromatography in the ion-exchange displacement mode.

Centrifugal partition chromatography in the ion-exchange displacement mode allowed a preparative and efficient fractionation of low-molecular-mass heparins from enoxaparin sodium. Amberlite LA2--a lipophilic liquid secondary amine--was chosen as a weak anion exchanger. The biphasic system methyl isobutyl ketone-water was selected. Protonated LA2 (10%, v/v) was added to the organic stationary phase. Hydroxide (Na+, OH-) was chosen as a displacer in the aqueous mobile phase. The observed pH and concentration profiles are typical of displacement chromatography, as supported by numerical simulation. The Dubois test for the analysis of sugar content and an analysis of sulfur content (and consequently sulfatation rate) were carried out to monitor the effectiveness of the procedure. Moreover, the fractions were analyzed by high-performance size-exclusion chromatography and the 1H NMR spectra confirmed the fractionation of the sample of enoxaparin sodium.

Chromatography, Gel↗

Fast protein liquid chromatography scale-up procedures for the preparation of low-molecular-weight proteins from urine.

A system for the rapid isolation of low molecular weight proteins from urine has been devised, and illustrated by alpha 1-microglobulin, beta 2-microglobulin, retinol binding protein, lysozyme and monoclonal light chains. Urine proteins from patients with tubular dysfunction were concentrated, either by ultrafiltration or ammonium sulphate precipitation. This was followed by gel chromatography on Sephadex G-50. The appropriate fractions were then separated by chromatography on Pharmacia monobead columns. A Mono Q strong anion exchanger was used for beta 2-microglobulin, retinol binding protein, alpha 1-microglobulin and free monoclonal light chains. Lysozyme was separated on a Mono S cation exchanger. The chromatography was first optimized on HR 5/5 columns and then scaled up to HR 16/10 columns.

Alpha-Globulins↗

Binding affinity of monoiodinated insulin tracers isolated after reversed-phase high-performance liquid chromatography.

Insulin and insulin monoiodinated in tyrosine A14, A19, B16 and B26 can be separated using reversed-phase high-performance liquid chromatography on a number of C18 columns eluted with acetonitrile containing triethylammonium phosphate or acetate buffers. The monoiodoinsulins can be isolated using lyophilization, gel chromatography, or Sep-Pak purification. Compared with similar tracers purified and isolated by disc electrophoresis-ion-exchange chromatography, the resulting binding affinities to adipocytes of the purified tracers are more or less reduced dependent on the choice of column support, buffer, separation temperature, and isolation procedure.

Animals↗

Rapid separation, quantitation and purification of products of polymerase chain reaction by liquid chromatography.

The polymerase chain reaction (PCR), a new, powerful method for rapid enzymatic amplification of specific DNA fragments, has gained tremendous popularity in molecular biology. This paper describes the successful application of liquid chromatography to the analysis of products of the PCR. Efficient separation of both DNA restriction fragments and amplified PCR products were achieved in 10-12 min on a new ion-exchange column, DEAE-NPR, packed with 2.5-microns non-porous particles. The PCR products were quantitated with a reproducibility within 10%. Use of liquid chromatography was demonstrated for separation and quantitation of PCR products in amounts below those required for direct analysis by ethidium bromide gel electrophoresis or a Hoechst 33258 dye-based fluorescence assay. Liquid chromatography was also demonstrated to be effective for quick optimization of PCR procedures.

Chromatography, High Pressure Liquid↗

High-performance liquid chromatography of staphylococcal enterotoxin B.

Size-exclusion, ion-exchange, and reversed-phase chromatography were investigated for use in purification and characterization of Staphylococcal enterotoxin B (SEB), a 28,000 Mr protein associated with Staphylococcal food-borne intoxication. In all approaches chromatography of crude or purified SEB yielded one or more components which displayed toxin activity and contained the 28,000 Mr SEB protein plus other lower-molecular-weight protein species. Reversed-phase chromatography of detergent-treated SEB permitted resolution of the 28,000 Mr protein from lower-molecular-weight components.

Bacterial Proteins↗

Purification of Food Color Red No. 106 (acid red) using high-speed counter-current chromatography.

High-speed counter-current chromatography (HSCCC) has been successfully applied to the separation of the components of Food Color Red No. 106 (R-106). The separation was performed using 25 mg of the sample with a two-phase solvent system composed of n-butanol and 0.01 M trifluoroacetic acid (1:1, v/v). Analyses by thin-layer chromatography, high-performance liquid chromatography and fast atom bombardment mass spectrometry confirmed that HSCCC was effective in the purification of the components of R-106. The separation gave 21 mg of a 99.9% pure main component (Acid Red) and 0.9 mg of 98.0% pure subsidiary dye which is probably a des-ethyl derivative.

Azo Compounds↗

Ion-pair chromatography of inositol polyphosphates with N-methylimipramine.

A novel counter-ion, N-methylimipramine, was synthesized and utilized in the separation of inositol phosphates by ion-pair chromatography. The structural identity of the counter-ion was documented by nuclear magnetic resonance spectroscopy. This counter-ion was capable of resolving inositol phosphates isocratically by reversed-phase high-performance liquid chromatography. Solvent polarity and ionic strength markedly affected the retention of the polyphosphorylated inositides. pH, however, was less significant in its effects. Injection of inositol trisphosphate paired to N-methylimipramine into a mobile phase containing tetrabutylammonium ions demonstrated free exchange of the inositide between the counter-ions. This counter-ion may therefore prove useful in defining empirically the mechanisms of ion-pair chromatography.

Chromatography↗

Rapid size-exclusion chromatography of proteoglycans.

The separation of intact proteoglycans using high-performance liquid chromatography is not trivial because the high molarity denaturing buffers required to maintain proteoglycans in the disaggregated state create back-pressures higher than the limits of many HPLC systems. Until recently, low back-pressure requirements of HPLC size-exclusion columns precluded their use for the separation of intact proteoglycans. In this study we show that rapid size-exclusion chromatography is possible in 8 M urea buffers using a Dionex BioLC system equipped with a Bio-Rad BioSil Sec-400 column. This technique reduced the time required for size-exclusion chromatography of intact proteoglycans from approximately 18 h (Sepharose CL4B) to 25 min and in some cases improved resolution of the sample.

Animals↗

Supercritical fluid chromatography in forensic science: a critical appraisal.

The application of supercritical fluid chromatography (SFC) in forensic science is reviewed. The applications centre on the analysis of explosives and of drugs of abuse. The systems employed are discussed in the context of comparison with gas chromatography and high-performance liquid chromatography methods which are traditionally used for such analyses. The advantages and disadvantages of SFC over these methods are discussed. Recommendations are made for the developments which are required in SFC technology if it is to find greater application in forensic science.

Chromatography, High Pressure Liquid↗

Purification and separation of individual collagenases of Clostridium histolyticum using red dye ligand chromatography.

Six collagenases present in the culture filtrate of Clostridium histolyticum have been purified to homogeneity. Chromatography over hydroxylapatite, Sephacryl S-200, and L-arginine-Affi-Gel 202 removes the brown pigment and the great majority of the contaminating proteinases active against casein, benzoyl-L-arginine ethyl ester, and elastin. Reactive Red 120 dye ligand chromatography subdivides the collagenases, which have very similar physicochemical properties, among four fractions. The final purification is achieved by chromatography over DEAE-cellulose and SP-Sephadex. All six collagenases, designated alpha, beta, gamma, delta, epsilon and zeta by the order of their purification, are highly active against collagen and devoid of other proteolytic activities. Each exhibits a single band on sodium dodecyl sulfate-polyacrylamide gels. Two distinct subspecies of the alpha and gamma enzymes have been isolated, which have the same molecular weight and activity but different isoelectric points. There is some less pronounced microheterogeneity for the other collagenases. On the basis of their activities toward native collagen and the synthetic peptide 2-furanacryloyl-L-leucylglycyl-L-prolyl-L-alanine (FALGPA), the six collagenases are divided into two classes. Class I collagenases (alpha, beta, and gamma) have high collagenase activity and moderate FALGPA activity while the class II collagenases (sigma, epsilon, and sigma) have moderate collagenase and high FALGPA activities. The relationship between these six collagenases and other reported to have been isolated in the literature has also been examined.

Chromatography, Affinity↗

Preparative continuous annular chromatography (P-CAC) enables the large-scale fractionation of fructans.

Fructans (fructo-oligosaccharides and inulin) are of increasing physiological and nutritional interest due to their health-promoting effects. Fructans originally extracted from chicory roots were separated by continuous annular and fixed-bed conventional gel chromatography. Both columns were packed with Toyopearl HW 40 (S) and eluted with deionized water. A multicomponent fractionation was established to obtain single oligosaccharides in a low molecular weight range up to a chain length of five and fractions containing an overall size distribution in the high molecular weight range up to a chain length of 90 monosaccharide units. The productivity and resolution of the continuous annular size exclusion chromatograph (40 cm bed height) were investigated and compared with those of the fixed-bed counterpart (2 x 100 cm bed height). The eluting fractions were analyzed by high-pH anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD). The productivity of the annular system was found to be 25-fold higher than the conventional system. Thus, annular chromatography exemplified for the fractionation of fructans is a powerful method for the large-scale and continuous fractionation of oligomeric and polymeric carbohydrates.

Chemical Fractionation↗

Evaluation of multidimensional chromatography coupled with tandem mass spectrometry (LC/LC-MS/MS) for large-scale protein analysis: the yeast proteome.

Highly complex protein mixtures can be directly analyzed after proteolysis by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). In this paper, we have utilized the combination of strong cation exchange (SCX) and reversed-phase (RP) chromatography to achieve two-dimensional separation prior to MS/MS. One milligram of whole yeast protein was proteolyzed and separated by SCX chromatography (2.1 mm i.d.) with fraction collection every minute during an 80-min elution. Eighty fractions were reduced in volume and then re-injected via an autosampler in an automated fashion using a vented-column (100 microm i.d.) approach for RP-LC-MS/MS analysis. More than 162,000 MS/MS spectra were collected with 26,815 matched to yeast peptides (7,537 unique peptides). A total of 1,504 yeast proteins were unambiguously identified in this single analysis. We present a comparison of this experiment with a previously published yeast proteome analysis by Yates and colleagues (Washburn, M. P.; Wolters, D.; Yates, J. R., III. Nat. Biotechnol. 2001, 19, 242-7). In addition, we report an in-depth analysis of the false-positive rates associated with peptide identification using the Sequest algorithm and a reversed yeast protein database. New criteria are proposed to decrease false-positives to less than 1% and to greatly reduce the need for manual interpretation while permitting more proteins to be identified.

Cations↗

Large-scale analysis of in vivo phosphorylated membrane proteins by immobilized metal ion affinity chromatography and mass spectrometry.

Global analyses of protein phosphorylation require specific enrichment methods because of the typically low abundance of phosphoproteins. To date, immobilized metal ion affinity chromatography (IMAC) for phosphopeptides has shown great promise for large-scale studies, but has a reputation for poor specificity. We investigated the potential of IMAC in combination with capillary liquid chromatography coupled to tandem mass spectrometry for the identification of plasma membrane phosphoproteins of Arabidopsis. Without chemical modification of peptides, over 75% pure phosphopeptides were isolated from plasma membrane digests and detected and sequenced by mass spectrometry. We present a scheme for two-dimensional peptide separation using strong anion exchange chromatography prior to IMAC that both decreases the complexity of IMAC-purified phosphopeptides and yields a far greater coverage of monophosphorylated peptides. Among the identified sequences, six originated from different isoforms of the plasma membrane H(+)-ATPase and defined two previously unknown phosphorylation sites at the regulatory C terminus. The potential for large-scale identification of phosphorylation sites on plasma membrane proteins will have wide-ranging implications for research in signal transduction, cell-cell communication, and membrane transport processes.

Amino Acid Sequence↗

Purification of testosterone-oestradiol-binding globulins from mammalian sera by anion-exchange high performance liquid chromatography.

Testosterone-oestradiol-binding globulin (TeBG) has been isolated from serum or plasma of several species using procedures that yielded highly purified protein, but which required multiple and tedious chromatographic steps. In this report we describe a procedure for the isolation of TeBG which involves two chromatographic steps: androgen affinity chromatography followed by anion-exchange high performance liquid chromatography (anion-exchange HPLC). The purity of the final product was confirmed by silver staining following fractionation on sodium dodecyl sulphate-containing polyacrylamide gels. The size heterogeneity and specific binding activity of TeBGs purified from human, rabbit, or bull serum (or plasma) by this technique was indistinguishable from preparations obtained by conventional chromatography. The present technique shortened the entire purification procedure to about 5 working days and yielded milligram quantities of highly purified protein. Bases on our experience with serum or plasma from the human, rabbit, and bull, this approach should be suitable for isolation of TeBG from a wide range of species.

Animals↗

The characterization of somatomedin A, isolated by microcomputer-controlled chromatography, reveals an apparent identity to insulin-like growth factor 1.

The polypeptide termed somatomedin A (SMA) was isolated from outdated human plasma by a new purification procedure, not using acid ethanol extraction. Fractions containing SMA were monitored by a placenta radioreceptorassay and a radioimmunoassay for SMA. The purification method utilized a microcomputer-controlled chromatography system, yielding both SMA (identified as insulin-like growth factor 1 (IGF-1) or a deamidated derivative) and insulin-like growth factor 2 (IGF-2). The first step of CM-Affigel blue adsorbed at neutral pH the majority of somatomedins detectable by the radioreceptorassay for SMA. Exclusion chromatography on Sephadex G-50 in 0.1 M acetic acid separated this active material from albumin and NaCl. Separation between SMA and IGF-2 was achieved on two different cation-exchange columns, but not in the final high-performance liquid chromatography step. The isoelectric points, determined by chromatofocusing, were 8.0 for SMA and 6.2 for IGF-2. The amino acid compositions of the two isolated peptides were indistinguishable from the known compositions of IGF-1 and IGF-2. Sequence analysis up to position 39 of the peptide with a pI of 6.2 also proved identity with IGF-2 for all positions examined. The peptide with a pI of 8.0, corresponding to SMA, was degraded directly as well as after CNBr cleavage. The results show that it is identical to IGF-1, with the possible exception of acid/amide assignment, which could correspond to a deamidation. If occurring in the native preparation before analysis, it could explain the chromatographic properties and isoelectric point of SMA versus IGF-1 isolated by other techniques.

Amino Acid Sequence↗

The novel disulfide reductase bis-gamma-glutamylcystine reductase and dihydrolipoamide dehydrogenase from Halobacterium halobium: purification by immobilized-metal-ion affinity chromatography and properties of the enzymes.

An NADPH-specific disulfide reductase that is active with bis-gamma-glutamylcystine has been purified 1,900-fold from Halobacterium halobium to yield a homogeneous preparation of the enzyme. Purification of this novel reductase, designated bis-gamma-glutamylcystine reductase (GCR), and purification of halobacterial dihydrolipoamide dehydrogenase (DLD) were accomplished with the aid of immobilized-metal-ion affinity chromatography in high-salt buffers. Chromatography of GCR on immobilized Cu2+ resin in buffer containing 1.23 M (NH4)2SO4 and on immobilized Ni2+ resin in buffer containing 4.0 M NaCl together effected a 120-fold increase in purity. Native GCR was found to be a dimeric flavoprotein of Mr 122,000 and to be more stable to heat when in buffer of very high ionic strength. DLD was chromatographed on columns of immobilized Cu2+ resin in buffer containing NaCl and in buffer containing (NH4)2SO4, the elution of DLD differing markedly in the two buffers. Purified DLD was found to be a heat-stable, dimeric flavoprotein of Mr 120,000 and to be very specific for NAD. The utility of immobilized-metal-ion affinity chromatography for the purification of halobacterial enzymes and the likely cellular function of GCR are discussed.

Chromatography, Affinity↗