Identification of cyclopentenyl fatty acids by gas liquid chromatography and mass spectrometry

The straight chain fatty acids and the cyclopentenyl fatty acids present in the lipids of Hydnocarpus wightiana seeds were separated as their pyrrolidides by means of gas chromatography. A gas chromatography-mass spectrometry system confirmed the complete separation and permitted the identification of the individual components in the sample.     

Identification of 4-methoxybenzoyl-N-glycine in urine by gas chromatography/mass spectrometry.

An unusual metabolite was detected in the urine of two children with neurological dysfunctions of unclear aetiology by using gas chromatography/mass spectrometry (GC/MS). On the basis of the analysis of its fragmentation pathways, synthesis of tentative compound and its GC/MS analysis it was stated that the unknown metabolite is 4-methoxybenzoyl-N-glycine.     

Estimation of deanol and choline by gas chromatography mass spectrometry

Analytical methods are described which permit the measurement of both deanol and choline in the same sample by gas chromatography mass spectrometry when either compound may be present in large excess (100:1). Deuterium labelling is employed for internal standards, to distinguish endogenous from tracer variants and to distinguish deanol in the sample from deanol formed by derivatization of choline. The limit of detection of both compounds is about 50 pmol.     

Peptidergic innervation of the rat Harderian gland

Summary The immunohistochemical localization of vasoactive intestinal polypeptide (VIP), Neurotensin (NT), cholestokinin (CCK), Neuropeptide Y (NPY), and calcitonin-gene-related peptide (CGRP) in rat Harderian glands was examined. Numerous VIP- and CCK-like immunoreactive nerves were found in close apposition to the acini. Sparse numbers of NT-, NPY-, and CGRP-like immunoreactive nerves were observed in close proximity to the acini and blood vessels. Some VIP-like immunoreactive nerves were shown to be co-localized with acetylcholinesterasepositive cholinergic nerves.     

Peptidergic innervation of the rat Harderian gland

The immunohistochemical localization of vasoactive intestinal polypeptide (VIP), Neurotensin (NT), cholecystokinin (CCK), Neuropeptide Y (NPY), and calcitonin-gene-related peptide (CGRP) in rat Harderian glands was examined. Numerous VIP- and CCK-like immunoreactive nerves were found in close apposition to the acini. Sparse numbers of NT-, NPY-, and CGRP-like immunoreactive nerves were observed in close proximity to the acini and blood vessels. Some VIP-like immunoreactive nerves were shown to be co-localized with acetylcholinesterase-positive cholinergic nerves.     

用气相色谱-质谱联用比较牛耳草代谢物的提取方法

通过比较不同的提取方法对牛耳草新鲜和脱水叶片中代谢物的提取效率,旨在建立一种可以有效鉴定并分析牛耳草脱水过程中关键小分子代谢物的种类和含量变化的方法,为研究植物耐脱水分子机制提供技术方法。本研究以气相色谱-质谱联用(GC-MS)为分析方法,对复苏植物牛耳草代谢物提取方法进行比较。从提取总色谱峰数目、提取效率、代谢物保留时间和提取效率稳定性等方面比较甲醇溶液(A法)和甲醇-氯仿-水溶液(B法)两种提取方法的提取效果。对牛耳草新鲜样品提取结果表明,B法提取的总色谱峰数目多于A法;对9种共有代谢物的提取效率比较结果表明,B法的提取效率高于A法;对10种色谱峰的保留时间和提取效率的方法学考察结果表明,两者保留时间RSD(相对标准偏差)值均小于1%,A法提取效率的RSD值≤10%的比例为50%,B法的为100%。A法对干样的提取色谱峰数目远少于鲜样,而B法对干样的提取色谱峰数目和鲜样没有显著差异,保留时间RSD值均小于1%,提取效率的RSD值与鲜样没有差异,稳定性良好。     

Identification of acetylcholine and propionylcholine in bull spermatozoa by integrate pyrolysis, gas chromatography and mass spectrometry

Acetylcholine was identified in fertile bull spermatozoa using combined pyrolysis gas-chromatography and mass spectrometry. Bull spermatozoa contain other minor choline esters in smaller quantities than acetylcholine. One of the minor choline esters is possibly propionycholine. The spermatozoa from infertible bulls exhibited low motility and very low levels of acetylcholine.     

The analysis of trenbolone and the human urinary metabolites of trenbolone acetate by gas chromatography/mass spectrometry and gas chromatography/tandem mass spectrometry.

The electron impact mass spectrometric properties of trimethylsilyl ether and fluoroacyl ester derivatives of trenbolone, combined or not combined with a methoxime group, are presented. Some derivatization problems were observed and were due to the formation of enol derivatives at the 3C-position in several tautomeric forms, which in their turn were not stable and lost two or four hydrogens under the conditions studied. The enolization could be minimized by carefully selecting the reaction conditions or could be prevented by the introduction of a methoxime group at the 3C-position. The limits of detection and identification of the methoxime heptafluorobutyryl ester and the methoxime trimethylsilyl ether derivative of trenbolone were determined using a mass selective detector in the electron impact mode and a triple-stage quadrupole in the methane positive chemical ionization mode. Selected reaction monitoring in tandem mass spectrometry did not improve the limit of detection, but because of the gain in selectivity did improve the limit of identification. The glucuronides of trenbolone and epitrenbolone could be identified in three urine specimens out of 200 samples in routine doping control.     

Proteome profiling in the rat Harderian gland

The Harderian gland is an orbital gland located behind the ocular bulb in most terrestrial vertebrates probably functioning for production of lipid secretion to protect the eye. We herein present a protein reference database of the rat Harderian gland that may serve as analytical tool for future proteomic work, report lipid and porphyrin handling cascades, address sequence conflicts and report structures that have not been so far described by proteomics methods.     

Identification of neuropeptides from the sinus gland of the crayfish Orconectes limosus using nanoscale on-line liquid chromatography tandem mass spectrometry

In this article, a novel and sensitive analytical strategy for direct characterization of neuropeptides from the X-Organ-sinus gland neurosecretory system of the crayfish Orconectes limosus is presented. A desalted extract corresponding to 0.5 sinus gland equivalents was analyzed in a nanoflow liquid chromatography system coupled to quadrupole time-of-flight tandem mass spectrometry (nanoLC-QTOF MS/MS). The existence and structural identity of four crustacean hyperglycemic hormone precursor-related peptide variants and two new genetic variants of the pigment-dispersing hormone, not detected by conventional chromatographic systems, molecular cloning, or immunochemical methods before, was revealed. The here-presented approach of the combined LC-QTOF MS/MS technique is a powerful tool to discover new peptide hormones in biological systems, due to its sensitivity, accuracy, and speed.     

Characterization of mixtures of dipeptides by gas chromatography/mass spectrometry

The gas chromatographic and mass spectrometric behavior of over 120 different dipeptides has been investigated. The dipeptides were analyzed as their N,O-perfluoropropionyl methyl ester derivatives by combined gas chromatography/mass spectrometry. Mass spectra of the dipeptides were obtained using both electron impact and chemical ionization. Gas chromatographic retention times were obtained for each of the dipeptides studied and utilized for the prediction of the retention times for most of the 400 common dipeptides. These techniques enable the unambiguous identification of dipeptides in mixtures.     

Automatic recognition of substance classes from data obtained by gas chromatography/mass spectrometry

The combination of gas chromatography and mass spectrometry is one of the most powerful instrumental techniques for analyses of complex samples. A bottleneck is the interpretation of the huge amount of data produced during an analysis. A new software program, MSclass, contains classifiers for the automatic recognition of about 80 chemical substructures or classes of compounds directly from low resolution mass spectra.     

N-Acetyltransferase activity of the rat Harderian gland.

Harderian gland extracts from male rats catalyze the conversion of serotonin to N-acetylserotonin and of tryptamine to N-acetyltryptamine. The reaction is linear up to 14 mg tissue and departs from linearity after 10 min. The pH otpimum with tryptamine as substrate is between 8 and 9. Enzymic activity of the gland in vivo does not show diurnal variations. Enzymic activity of tissue in organ culture is not stimulated by 10 micrometer isoproterenol or 100 micrometer dibutyryl cyclic AMP. Harderian gland tissue in culture can acetylate tryptamine and serotonin and can O-methylate the N-acetylserotonin to form melatonin.     

Analysis of beta-hydroxy-beta-methyl butyrate in plasma by gas chromatography and mass spectrometry

A method for measuring the branched chain hydroxy acid beta-hydroxy-beta-methyl butyrate (HMB, a product of leucine catabolism) has been described. A [2H6]HMB internal standard was added to plasma and standards, and samples were extracted with diethyl ether, backextracted into neutral phosphate, dried, and derivatized for gas chromatography and mass spectrometry. The natural HMB was monitored at 175 amu and the deuterated HMB was monitored at 181 amu. Standard curves were linear to at least 25 microns and were quantitatively recovered from plasma. Basal concentrations of plasma HMB were from 1 to 2 microM in sheep and increased three- to fourfold when leucine's alpha-ketoacid (alpha-ketoisocaproate, KIC) was fed to lambs. This method can also be adapted to quantitate KIC and other branched chain ketoacids in plasma during the same run.     

Determination of acrolein by headspace solid-phase microextraction gas chromatography and mass spectrometry

We developed a headspace solid-phase microextraction (headspace SPME) method to measure acrolein in human urine. This new technique resolves some problems with the headspace gas chromatography and mass spectrometry (GC–MS) method which we developed previously. With the original method, a column and a filament were damaged by the injection of air. A 0.5-ml urine (or phosphate-buffered saline) sample in a glass vial containing propionaldehyde as an internal standard was heated for 5 min. The SPME fiber (65 μm carbonwax–divinylbenzene fiber) was exposed to the headspace and then inserted into a GC–MS instrument in which a DB-WAX capillary column (30 m×0.32 mm, film thickness 0.5 μm) was installed. The total analysis time was 15 min. The inter-assay and intra-assay coefficients of variation were 10.07 and 5.79%, respectively. The calibration curve demonstrated good linearity throughout concentrations ranging from 1 to 10 000 nM. The headspace SPME method exhibits high sensitivity and requires a short analysis time as well as the previous method. We conclude that this method is useful to measure urinary acrolein.     

Method for analysis of polybrominated biphenyls by gas chromatography mass spectrometry

Gas chromatography using a short packed column (45 cm, 0.2 cm i.d., 2% OV-101 on Gas-Chrom Q) with mass spectrometric detection in the selected ion monitoring mode has been found satisfactory for the analysis of lower as well as higher polybrominated biphenyls. Acceptable sensitivity (< 1 ng) may be achieved for this method by focusing selectively at either the low (m/z 20-600) or the high m/z 600-1000) range of the quadrupole filter (low range for mono- through hexabromobiphenyl, high range for hexa- through decabromobiphenyl). A tuning technique has been developed for low range and high range polybrominated biphenyls using the ion abundances of perfluorotributylamine as a standard. Standard ions for the quantitation of mono- through decabromo-biphenyls were selected and validated. The technique was applied to the analysis of a variety of environmental samples.