Analysis of thiohydantoins from amino acids by gas-liquid chromatography on short glass capillary columns

A method for separation of amino acid methyl or phenyl thiohydantoins by GLC on a short glass capillary column is described. Calculations of required parameters of the capillary column are presented. By the described methods, nineteen of twenty silylated methylthiohydantoins were separated in one run. The last one (histidine) can be identified on the same column by starting the analysis at a higher temperature. Cysteine and arginine were analysed as S-methylcysteine and ornithine, respectively.     

Xterra RP18柱高效液相色谱法快速分离测定氨基酸

建立了一种用XterraRP1 8色谱柱快速分离测定水解氨基酸的方法。所采用的色谱条件是 :WatersAlliance系统 ,柱温 5 6℃ ,流速 1 .8ml/min ,检测波长 2 4 8nm ,梯度分离 ,运行周期 2 5min,柱反压低于 2 0 0 0Psi。在 1 7.5min内分离了包括AMQ、NH3 和牛磺酸在内的 2 1种氨基化合物 ,适应于复合氨基酸注射液、含牛磺酸的氨基酸口服液及水解氨基酸样品的分析测定     

Postnatal hypoglycaemia and gluconeogenesis in the newborn rat. Delayed onset of gluconeogenesis in prematurely delivered newborns.

A normal-phase high-pressure liquid-chromatography system was used with amino-propyl-bonded silica as the column packing in order to resolve amino acids, reduced amino acid derivatives and reduced cross-links of collagen. The method utilized a solvent system comprising acetonitrile and 10 mM-potassium phosphate buffer, pH 4.3, as described by Schuster [(1980) Anal. Chem. 52, 617-620]. With modifications to the original gradient elution it was possible to resolve fully the radiolabelled components of reduced collagen in one run of less than 80 min. The method is very sensitive, and small biopsy samples can readily be investigated. Although solute retention times gradually decreased with repeated use, little loss of resolution of the reducible cross-links of collagen occurred during a 30-day trial period.     

Automated simultaneous isolation and quantitation of labeled amino acid fractions from plasma and tissue by ion-exchange chromatography

In order to trace metabolic pathways of amino acids in the body, a known labeled amount of an amino acid is infused. Dilution in the body pool is measured, using the specific activity and calculated by dividing the labeled amount of an amino acid (tracer) by its total pool (tracer + tracee). This paper describes a method, which combines fractionation and quantitation of multiple amino acids in one chromatographic run. To achieve this, we performed a classical amino acid ion-exchange separation on standard HPLC equipment. The column effluent was divided continuously into two solvent streams using a rapidly switching, pump controlled “split-valve”. The main part (90%) was directed to a computer controlled fraction collector, while the remaining 10% was mixed with o-phthaldialdehyde reagent after which fluorescence was measured. Using this system, 10–1000 μl of deproteinized plasma, representing a maximum of 50 nmol of each amino acid, could be fractionated and quantitated in the same chromatographic run. In addition to optimal counting efficiency of an off-line radioactivity counter, it enabled easy measurement of the specific activity of multiple amino acid tracers.     

Separation of peptides by reverse-phase high-performance liquid chromatography using propyl- and cyanopropylsilyl supports

The separation of peptides and proteins by reverse-phase high-performance liquid chromatography with cyanopropylsilyl and large-pore propylsilyl supports, together with aqueous trifluoroacetic acid/acetonitrile gradients, was studied. Operating parameters (trifluoroacetic acid concentration, flow rate, and gradient slope) were evaluated using different enzymatic digests of horse cytochrome c and bovine serum albumin. Peptides ranging in size from five amino acids to 68 kDa could be separated on the propylsilyl column in a single chromatographic run. The cyanopropylsilyl column is suitable as a supplement to the use of the large-pore column for medium size (5-20 amino acids) peptides. The chromatographic supports and conditions presented here offer a simple, sensitive, and rapid separation system for a wide size range of peptides and proteins. They extend the versatility of separation methodology for these molecules.     

Acid-labile amino acid precursors in the Murchison meteorite. 1: Chromatographic fractionation.

The amino acid content of a hot water extract of the Murchison meteorite can be increased by over 100 per cent by subjecting the extract to acid hydrolysis. The acid-labile compounds in the extract that account for this increase were fractionated by column chromatography on a cation exchange resin. Seventy mole per cent behaved as neutral or acidic compounds and were eluted from the column with an initial water wash. The remaining 30 mole per cent (basic precursors) were retained on the column and were eluted with the free amino acids by aqueous NH4OH. The acid-labile amino acid precursors in the water eluate could be retained and further fractionated on an anion exchange column, indicating that they are acidic compounds.     

Quantitative gas chromatographic analysis of amino acids on a short glass capillary column

A study of the quantitative gas chromatographic analysis of protein amino acids as their N-heptafluorobutyric amino acid n-propyl esters on a glass capillary column has been made. The analysis is completed within 35 min with good separation of the common protein amino acids in a single-column run.Hydrolyzed peptides have been analyzed. The analyses were performed with a precision varying between 1 and 6% (mean relative standard deviation) depending on the number of amino acid residues in the peptide. The amount taken for analysis was 20–300 μg. The results agree with the known sequences of the peptides and with the analyses by ion-exchange chromatography except for cysteine. This amino acid can be analyzed after modification as S-methylated cysteine.     

Monolithic column-based reversed-phase liquid chromatography separation for amino acid assay in microdialysates and cerebral spinal fluid

The development of a HPLC method using a monolithic C18 column is described using fluorescence detection for the assay of 21 amino acids and related substances with derivatisation using ortho-phthaldialdehyde (OPA) in the presence of 3-mercaptopropionic acid (3-MPA). The method employs a tertiary gradient and has a run time of 24 min. Linearity (r2) for each amino acid was found to be greater than 0.99 up to a 10 microM concentration; reproducibility across all analyses (relative standard deviation (R.S.D.)) was between 0.97 and 6.7% and limit of detection (LOD) between 30 and 300 fmol on column. This method has been applied to the analysis of amino acids in both spinal microdialysis and cerebral spinal fluid samples.     

Measurement of picomoles of phosphoamino acids by high-performance liquid chromatography.

A reverse-phase, high-performance liquid chromatographic system (HPLC) is described that makes possible optimal resolution and quantitation of picomole levels of phosphoamino acids, both with or without the presence of a large excess of nonphosphorylated amino acids. The assay involves precolumn derivatization of an amino acid mixture with phenyl isothiocyanate (PITC) at room temperature, followed by separation of phosphoamino acids from other amino acids by HPLC. The liquid chromatography was carried out on a C18 reverse-phase column at pH 7.4 and 30 degrees C using gradient elution with eluent A as 157 mM sodium acetate containing 2% acetonitrile and eluent B as 60% acetonitrile in water. A uv absorption at 254 nm is employed for detection of the PITC-derivatized amino acids eluting from the column. Amino acids are eluted with baseline resolution in the following order: phosphoserine, phosphothreonine, aspartic acid, glutamic acid, and phosphotyrosine followed by other amino acids. The sensitivity is in the picomole range, and the separation time, injection to injection, is 36 min. Phosphoserine, phosphothreonine, and phosphotyrosine are resolved within the first 8 min. This procedure enables determination of as low as 5 pmol of nonradioactive phosphoamino acids in a 100-fold excess of amino acids, as is usually present in most phosphoproteins in the natural state. Phosphoamino acids in polypeptides separated by sodium dodecyl sulfate-polyacrylamide electrophoresis and transferred to polyvinylidene difluoride (PVDF) membrane, or protein samples directly blotted on the membrane, can also be analyzed by this procedure after acid hydrolysis of the proteins bound to the PVDF membrane.     

A chromatographic method for the quantitative analysis of the deprotection of dithiasuccinoyl (Dts) amino acids.

The dithiasuccinoyl (Dts)-protecting group for amino acids is revoved by thiols (2 equivalents) through the intermediacy of an open-chain carbamoyl disulfide. Starting materials, intermediates, and products can be separated from one another on the standard amino acid analyzer 0.9 × 54-cm column of sulfonated polystyrene resin with 0.2 n sodium citrate buffers. Compounds are detected with the standard ninhydrin-hydrindantin reagent because the hydrindantin acts as a reducing agent and the released amino acid reacts in situ with the ninhydrin to give a purple color. Elution times, integration constants, and the ratios of absorbances at 570 and 440 nm are tabulated. Quantitative conversion of dithiasuccinoyl amino acids to the parent amino acids can be achieved with 0.1 n sodium hydroxide, 0.01 m alcoholic sodium borohydride, 0.1 m triphenylphosphine or 2 m m tri-n-butylphosphine in dioxane-H₂O (9:1) or water, and with a variety of thiols under various conditions. The chromatographic methodology is applicable to the determination of rate constants of the pseudo-first-order reductive deprotection of dithiasuccinoyl amino acids.     

Automated carboxy-terminal sequence analysis of peptides.

Proteins and peptides can be sequenced from the carboxy-terminus with isothiocyanate reagents to produce amino acid thiohydantoin derivatives. Previous studies in our laboratory have focused on solution phase conditions for formation of the peptidylthiohydantoins with trimethylsilylisothiocyanate (TMS-ITC) and for hydrolysis of these peptidylthiohydantoins into an amino acid thiohydantoin derivative and a new shortened peptide capable of continued degradation (Bailey, J. M. & Shively, J. E., 1990, Biochemistry 29, 3145-3156). The current study is a continuation of this work and describes the construction of an instrument for automated C-terminal sequencing, the application of the thiocyanate chemistry to peptides covalently coupled to a novel polyethylene solid support (Shenoy, N. R., Bailey, J. M., & Shively, J. E., 1992, Protein Sci. I, 58-67), the use of sodium trimethylsilanolate as a novel reagent for the specific cleavage of the derivatized C-terminal amino acid, and the development of methodology to sequence through the difficult amino acid, aspartate. Automated programs are described for the C-terminal sequencing of peptides covalently attached to carboxylic acid-modified polyethylene. The chemistry involves activation with acetic anhydride, derivatization with TMS-ITC, and cleavage of the derivatized C-terminal amino acid with sodium trimethylsilanolate. The thiohydantoin amino acid is identified by on-line high performance liquid chromatography using a Phenomenex Ultracarb 5 ODS(30) column and a triethylamine/phosphoric acid buffer system containing pentanesulfonic acid. The generality of our automated C-terminal sequencing methodology was examined by sequencing model peptides containing all 20 of the common amino acids. All of the amino acids were found to sequence in high yield (90% or greater) except for asparagine and aspartate, which could be only partially removed, and proline, which was found not be capable of derivatization. In spite of these current limitations, the methodology should be a valuable new tool for the C-terminal sequence analysis of peptides.     

Acid-labile amino acid precursors in the Murchison meteorite

The amino acid content of a hot water extract of the Murchison meteorite can be increased by over 100 per cent by subjecting the extract to acid hydrolysis. The acid-labile compounds in the extract that account for this increase were fractionated by column chromatography on a cation exchange resin. Sevently mole per cent behaved as neutral or acidic compounds and were eluted from the column with an initial water wash. The remaining 30 mole per cent (basic precursors) were retained on the column and were eluted with the free amino acids by aqueous NH₄OH. The acid-labile amino acid precursors in the water eluate could be retained and further fractionated on an anion exchange column, indicating that they are acidic compounds.Contribution number 101 from the Center for Meteorite Studies.     

Rapid sample processing and fast gas chromatography for identification of bacteria by fatty acid analysis

A commercially available system for microbial identification by fatty acid analysis (Microbial Identification System (MIS), MIDI, Newark, DE, USA) requires a four-step sample derivatization procedure in screw-cap test tubes. By using glass tubes in a 96-well format with multichannel pipetting, the time required for sample preparation can be greatly reduced. The standard gas chromatography column, 25 m long by 0.20 mm ID, is replaced with a 10 m long by 0.10 mm ID column, reducing the gas chromatography run time to one third of the standard time. Either or both of these procedures can be easily implemented in any laboratory using the MIDI system, resulting in faster identifications and higher sample throughput.     

反相高效液相色谱法测定血浆游离氨基酸

本文报告了采用高效液相色谱法反相梯度洗脱,邻苯二甲醛和β-巯基乙醇柱前衍生化,荧光检测分血浆游离氨基酸。实验采用线性洗脱,在50分钟内可同时测定18种氨基酸,血浆样品的预处理简单,衍生化反应的时间仅需1分30秒,血浆样品的实际进样量少于1μl。本测定方法的精确度高,各个氨基酸保留时间的变异系数平均为0.89%±0.45%(SD),峰面积的变异系数平均为2.06%±1.76%(SD),各个氨基酸的浓度在15—150μmol/L的范围中,线性关系的相关系数平均为0.985±0.0305(SD)。准确性好,各个氨基酸的回收率平均为97.6%±5.1%(SD)。实验还讨论了氨基酸分离时溶液pH值、柱温、离心速度等因素对分析结果的影响。     

Liquid chromatography for iothalamate in biological samples

We have previously reported an iothalamate assay for the assessment of the glomerular filtration rate (GFR) that required a long column equilibration time and 22 min run time per sample. We now report a simpler assay that requires a run time of only 5.5 min and is more precise and accurate than the earlier technique. The mobile phase consisted of methanol-acetonitrile-50 mM sodium monobasic phosphate (10:5:85, v/v) at pH 4.4, pumped at a rate of 1.5 ml/min on a C(18) reversed-phase column. Samples of plasma and urine were deproteinized with 1 volume of 4% perchloric acid or 9 volumes of 2% perchloric acid, respectively. No internal standard was used. The diode array detection system collected absorbance at 240 nm and the peak height areas of iothalamate were determined. The iothalamate peak appeared at 3.5 min. Detector response was linear over the range tested (10-2000 microg/ml). Within-run precision was <3% for both plasma and urine and accuracy was 96-102%. Between-day precision for plasma and urine analyses were <7%. The recovery of iothalamate in urine and plasma were 102% and 91%, respectively. There was excellent thermal and pH stability of iothalamate. No interference was found with para-amino hippuric acid (PAH) or N-acetyl PAH, which can be simultaneously assayed, if desired.     

Isolation and characterization of polypeptide at the picomole level. Pre-column formation of peptide derivatives with dimethylaminoazobenzene isothiocyanate.

Polypeptides coupled with dimethylaminoazobenzene isothiocyanate through their amino groups to form dimethylaminoazobenzenethiocarbamoyl- (DABTC-)peptides can be separated by reversed-phase high-pressure liquid chromatography and detected in the visible region (436 nm). As little as 1 ng (2 pmol) of a DABTC-pentapeptide can be identified against a stable base-line with the signal-to-noise ratio of 10. The DABTC-peptides can also be recovered from the column, and their N-terminal amino acids (obtained by direct treatment with aqueous acid) and amino acid compositions and sequences can be all analysed at the picomole level. The power of this method is demonstrated by the complete separation and characterization of model peptides, peptide hormones and peptides derived from enzymic fragmentation of proteins. This new technique should provide a sensitive and efficient tool for peptide analysis at the nanogram level.     

Application of amino acid analysis by high-performance liquid chromatography with phenyl isothiocyanate derivatization to the rapid determination of free amino acids in biological samples

An amino acid analysis by reversed-phase high-performance liquid chromatography after precolumn derivatization with phenyl isothiocyanate was adapted to the determination of free amino acids in plasma or other biological fluids and in tissue homogenates. Preparation of samples included deproteinization by 3% sulphosalicylic acid, and careful removal under high vacuum of residual phenyl isothiocyanate after derivatization. A Waters Pico-Tag column (15 cm long) was used, immersed in a water-bath at 38°C. In rat or human plasma, separation of 23 individual amino acids, plus the unresolved pair tryptophan and ornithine, was obtained within 13 min. Including the time for column washing and re-equilibration, samples could be chromatographed at 23-min intervals. Variability was tested for each amino acid by calculating the coefficients of variation of retention times (less than 1% in the average) and peak areas (less than 4% for both intra-day and inter-day determinations). The linearity for each standard amino acid was remarkable over the concentration range 3–50 nmol/ml. The mean recovery of amino acid standards added to plasma prior to derivatization was 97 ± 0.8%, except for aspartate (82%) and glutamate (81%). This method is rapid (almost three samples per hour can be analysed, more than in any other reported technique), with satisfactory precision, sensitivity and reproducibility. Therefore, it is well suited for routine analysis of free amino acids in both clinical and research work.     

High-sensitivity amino acid analysis by derivatization with O-phthalaldehyde and 9-fluorenylmethyl chloroformate using fluorescence detection: applications in protein structure determination

An amino acid analysis method using a commercially available analyzer that accurately quantitates protein-derived amino acids in the 10-100 pmol range is described. The method utilizes the robotic capability of the analyzer's autosampler to perform precolumn derivatization of both primary and secondary amino acids with o-phthalaldehyde and 9-fluorenylmethyl chloroformate, respectively. The derivatized amino acids are then separated on a C-18 reverse-phase amino acid column and quantitated in a single run by fluorescence detection. The characterization of beta-lactoglobulin and two tryptic peptides from the bacterial enzyme diaminopimelic acid epimerase is used to demonstrate the sensitivity and utility of this method.     

Resolution of three forms of superoxide dismutase by immobilised metal affinity chromatography

A new method for separation of three forms of superoxide dismutase (SOD) using immobilised metal affinity chromatography (IMAC) is reported. Fe-, Mn- and Cu/Zn-SODs were eluted sequentially from Cu²⁺-IMAC column with an increasing gradient of a counter ion (NH⁺₄) run in combination with an increasing pH gradient (6.8–7.8). The combined gradient elution method resulted in separation of SODs with high resolution, the three proteins being eluted in electrophoretically homogeneous forms. Similar preparation could not be achieved by either increasing gradient of a counter ion or decreasing pH gradients used separately. The described methodology has been successfully applied for separation of three SODs from a protozoan parasite, indicating that this combined gradient elution system for IMAC offers new possibilities for the high-resolution separation of proteins exhibiting only minor differences in their amino acid composition and structure.     

Analysis of 26 amino acids in human plasma by HPLC using AQC as derivatizing agent and its application in metabolic laboratory

The present study reports the simultaneous analysis of 26 physiological amino acids in plasma along with total cysteine and homocysteine by high-performance liquid chromatography (HPLC) employing 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC) as precolumn derivatizing reagent. Separations were carried out using Lichrospher 100 RP-18e (5 μm) 250 × 4.0 mm column connected to 100 CN 4.0 × 4.0 mm guard column on a quaternary HPLC system and run time was 53 min. Linearity of the peak areas for different concentrations ranging from 2.5 to 100 pmol/μL of individual amino acids was determined. A good linearity (R ² > 0.998) was achieved in the standard mixture for each amino acid. Recovery of amino acids incorporated at the time of derivatization ranged from 95 to 106 %. Using this method we have established the normative data of amino acids in plasma, the profile being comparable to the range reported in literature and identified cases of classical homocystinuria, cobalamin defect/deficiency, non-ketotic hyperglycinemia, hyperprolinemia, ketotic hyperglycinemia, urea cycle defect and maple syrup urine disease.