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Russell P Newton

Publications and source records attributed to Russell P Newton.

18 recordsLinked to original sources
PubMed2006

In-source CID of guanosine: gas phase ion-molecule reactions.

In-source collision induced dissociation was applied to access second generation ions of protonated guanosine. The in-source gas-phase behavior of [BH2]+-NH3 (m/z 135, C5H3N4O+) was investigated. Adduct formation and reactions with available solvent molecules (H2O and CH3OH) were demonstrated. Several addition/elimination sequences were observed for this particular ion and solvent molecules. Dissociation pathways for the newly formed ions were developed using a QqTOF mass spectrometer, permitting the assignment of elemental compositions of all product ions produced. Reaction schemes were suggested arising from the ring-opened intermediate of the protonated base moiety [BH2]+, obtained from fragmentation of guanosine. The mass spectral data revealed that the in-source CH3OH-reaction product underwent more complex fragmentations than the comparable ion following reaction with H2O. A rearrangement and a parallel radical dissociation pathway were discerned. Apart from the mass spectrometric evidence, the fragmentation schemes are supported by density functional theory calculations, in which the reaction of the ring-opened protonated guanine intermediate with CH3OH and a number of subsequent fragmentations were elaborated. Additionally, an in-source transition from the ring-opened intermediate of protonated guanine to the ring-opened intermediate of protonated xanthine was suggested. For comparison, a low-energy collision induced dissociation study of xanthosine was performed. Its dissociation pathways agreed with our assumption.

Computer Simulation↗
PubMed2006

Analysis of urinary nucleosides. V. Identification of urinary pyrimidine nucleosides by liquid chromatography/electrospray mass spectrometry.

Modified urinary nucleosides are potentially invaluable in cancer diagnosis, as they reflect altered RNA turnovers. High-performance liquid chromatography (HPLC) was combined with full-scan mass spectrometry, tandem mass spectrometry, MS(n) analysis and accurate mass measurements in order to identify pyrimidine nucleosides purified from urine. Potential nucleosides were assessed by their evident UV absorbance in the HPLC chromatogram and then further examined by the various mass spectrometric techniques. In this manner numerous pyrimidine nucleosides were identified in the urine samples from cancer patients including pseudouridine, cytidine, two methylcytidines and an acetylcytidine. Furthermore, a number of novel modified pyrimidine nucleosides were tentatively identified via critical interpretation of the combined mass spectrometric data.

Biomarkers, Tumor↗
PubMed2006

Quantitative determination of major active components in Ginkgo biloba dietary supplements by liquid chromatography/mass spectrometry.

A reversed-phase high-performance liquid chromatography/electrospray ionisation mass spectrometry (RP-HPLC/ESI-MS) method was developed and validated for the simultaneous determination of ten major active components in Ginkgo biloba extract (bilobalide, ginkgolides A, B, C, quercetin, kaempferol, isorhamnetin, rutin hydrate, quercetin-3-beta-D-glucoside and quercitrin hydrate) which have not been previously reported to be quantified in a single analysis. The ten components exhibit baseline separation in 50 min by C18 chromatography using a water/1:1 (v/v) methanol/acetonitrile gradient. Quantitation was performed using negative ESI-MS in selected ion monitoring (SIM) mode. Good reproducibility and recovery were obtained by this method. The sensitivity of both UV and different mass spectrometry modes (full scan, selected ion monitoring (SIM), and selected reaction monitoring (SRM)) were compared and both quantitation with and without internal standard were evaluated. The analysis of Ginkgo biloba commercial products showed remarkable variations in the rutin and quercetin content as well as the terpene lactone contents although all the products satisfy the conventional quality control method.

Chromatography, High Pressure Liquid↗
PubMed2006

Determination of active components of Ginkgo biloba in human urine by capillary high-performance liquid chromatography/mass spectrometry with on-line column-switching purification.

Ginkgo biloba is one of the most popular herbal nutritional supplements, with terpene lactones and flavonoids being the two major active components. An on-line purification high-performance liquid chromatography/mass spectrometry (HPLC/MS) method was successfully developed for the quantitative determination of flavonoids and terpene lactones excreted in human urine after ingesting the herbal supplement. Satisfactory separation was obtained using a C18 capillary column made in-house with sample clean-up and pre-concentration achieved using a C18 pre-column with column switching. High selectivity and limits of detection of 1-18 ng/mL were achieved using a selected ion monitoring (SIM) scan in negative ion mode; the on-line solid-phase extraction (SPE) recovery of the active components in Ginkgo biloba determined in this study was greater than 75%.

Capillary Electrochromatography↗
PubMed2005

Study of the mass spectrometric fragmentation of pseudouridine: comparison of fragmentation data obtained by matrix-assisted laser desorption/ionisation post-source decay, electrospray ion trap multistage mass spectrometry, and by a method utilising electrospray quadrupole time-of-flight tandem mass spectrometry and in-source fragmentation.

Many nucleosides and their modified forms have been studied by mass spectrometry elaborating the detailed fragmentation pathways under MS2 and MS(n) conditions. Although the C-nucleoside pseudouridine has been fragmented and studied briefly, usually amongst many other nucleosides, it has not been investigated to the same extent as other nucleosides. In this report a number of different mass spectrometric techniques are applied to obtain a fuller picture of pseudouridine fragmentation. At the same time this study is used to compare different tandem mass spectrometric techniques, including a novel methodology utilising a quadrupole time-of-flight (Q-ToF) instrument for MS(n) analysis comparable with that available with an ion trap mass spectrometer.

Pseudouridine↗
PubMed2005

Intriguing mass spectrometric behavior of guanosine under low energy collision-induced dissociation: H2O adduct formation and gas-phase reactions in the collision cell.

An in-depth study of the fragmentation pathway of guanosine was conducted by using an in-source collision-induced dissociation high-mass accuracy tandem mass spectrometry experiment. The equivalent of MS4 data, a level of information normally achieved on ion trap instruments, was obtained on a Q-TOF mass spectrometer. The combination of the features of high-resolution, accuracy, and in-source CID permitted the unambiguous elucidation of the different fragmentation pathways. Furthermore the elemental compositions of the product ions generated were assigned and their mutual genealogical relationships established. Formerly proposed dissociation pathways of guanosine were revisited and elaborated on more deeply. Furthermore, the presence of H2O in the collision cell of several tandem MS instruments was demonstrated and its effect on the product ion spectra investigated. The neutral gain of H2O by particular fragments of guanosine was experimentally proven by using argon, saturated with H2(18)O, as the collision gas. Data indicating the occurrence of more complex reactions in the collision cell as a result of the presence of H2O were produced, specifically relating to neutral gain/neutral loss sequences. In silico calculations supported the experimental observation of neutral gain by guanosine fragments and predicted a similar behavior for adenosine. The latter was subsequently experimentally confirmed.

Argon↗
PubMed2004

Investigation of the use of immobilised metal affinity chromatography for the on-line sample clean up and pre-concentration of nucleotides prior to their determination by ion pair liquid chromatography-electrospray mass spectrometry: a pilot study.

This study explored an alternative way to enrich and pre-purify biological samples containing nucleoside mono-, di- and triphosphates. These compounds were trapped by immobilised metal affinity chromatography (IMAC) on a Poros 20 MC IMAC-column, which was conditioned with Fe3+. The IMAC-column was implemented in a column switching set-up separating nucleoside mono-, di- and triphosphates on a Hypersil ODS 35 mm x 0.3 mm capillary column hyphenated to electrospray mass spectrometry resulting in the first miniaturised column switching liquid chromatography-mass spectrometry (LC-MS) system for nucleotides.

Chromatography, Affinity↗
PubMed2004

Estimation of guanine deaminase using guanosine as a "prosubstrate".

Plasma guanine deaminase (guanase; GD) is well established as an indicator of hepatocellular disease, recently being applied in the detection of hepatitis C in donor blood and in the diagnosis of hepatoma. No totally efficient, simple method for the estimation of plasma GD activity is routine since both guanine and 8-azaguanine, the substrates of the enzyme, are scarcely soluble in water. This difficulty in preparing stable substrates of sufficient concentration has resulted in methods that are both troublesome and inaccurate. Here we describe the development of new colorimetric and high-performance liquid chromatography (HPLC) methods utilizing guanosine as a "prosubstrate." After an initial breakdown of the guanosine to guanine using purine nucleoside phosphorylase, the ammonia formed as a result of the breakdown of the guanine by GD was estimated colorimetrically by the Berthelot reaction. As an alternative or a complementary assay, the xanthine also formed was measured using an isocratic HPLC method. These methods are suitable for routine assays for measuring plasma GD over a wide range of activities.

Ammonia↗
PubMed2004

Mass spectrometric studies on the intrinsic stability of destruxin E from Metarhizium anisopliae.

Destruxins are of current interest as bioactive agents. They are cyclic hexadepsipeptides produced by fungi, the most common destruxins, A, B and E, differing in the structure of a side chain. Before they can be widely used, the potential risk of destruxins and their metabolites entering the human food chain must to be assessed; thus, knowledge of the structures of their degradation products is essential. Here we report a study aimed at identifying, by tandem mass spectrometry and accurate mass analysis, the products resulting from thermally and temporally induced degradation of destruxin E. The degradation products fell into two groups: those with relatively simple modifications of the side chain and those involving much more complex rearrangements. The structures of most of the degradation products were deduced from the MS data, with the major product being destruxin E diol: significantly, this compound had previously been reported to have only been produced as a metabolic product of enzyme action rather than as a simple degradation product as demonstrated here.

Ascomycota↗
PubMed2004

Analysis of urinary nucleosides. IV. Identification of urinary purine nucleosides by liquid chromatography/electrospray mass spectrometry.

Modified urinary nucleosides are potentially invaluable in cancer diagnosis. High-performance liquid chromatography (HPLC) was combined with full scan mass spectrometry (MS), tandem mass spectrometry and MSn analysis in order to identify purine nucleosides purified from urine. UV peaks evident in the chromatogram were examined by the various mass spectrometric techniques and adenosine, 1-methyladenosine, xanthosine, N1-methylguanosine, N2-methylguanosine, N2,N2-dimethylguanosine, N2,N2,N7-trimethylguanosine, inosine, and 1-methylinosine were each identified in the urine samples from cancer patients. The benefits of the use of LC/MS compared with HPLC alone are discussed.

Chromatography, High Pressure Liquid↗
PubMed2004

Plasma purine nucleoside phosphorylase in cancer patients.

BACKGROUND: Purine nucleoside phosphorylase (PNP) is the purine salvage enzyme that converts guanosine to guanine and inosine to hypoxanthine. METHODS: 279 samples from patients with differing cancers were collected during treatment at both pre- and post-dose stages for plasma PNP activity and compared with a normal population. RESULTS: Normal plasma PNP activity was found to be 3.2+/-1.4 U/l (n=55) as compared with the cancer patients (pre-dose 12.3+/-7.4 U/l [n=215] and post-dose 11.2+/-5.9 U/l [n=64]). Levels of plasma PNP did not differ greatly between the different cancer types but were on average four times greater than that found in the reference population.

Antineoplastic Agents↗
PubMed2004

Plant proteome analysis by mass spectrometry: principles, problems, pitfalls and recent developments.

The genome of several species has now been elucidated; these genomes indicate the proteomic potential of the cell. While identification of genomes has been, and continues to be, a technically and intellectually demanding process, the identification of the proteome contains inherently greater difficulties. The proteome of each living cell is dynamic, altering in response to the individual cell's metabolic state and reception of intracellular and extracellular signal molecules, and many of the proteins which are expressed will be post-translationally altered. Thus if the purpose of the proteome analysis is to aid the understanding of protein function and interaction, then it is identification of the proteins in their final state which is required: for this mass spectrometric identification of individual proteins, indicating site and nature of modifications, is essential. Here we review the principles of the methodologies involved in such analyses, give some indication of current achievements in plant proteomics, and indicate imminent and prospective technical developments.

Mass Spectrometry↗
PubMed2004

Cyclic nucleotides.

The natural occurrence of cyclic nucleotides in higher plants, formerly a topic of fierce debate, is now established, as is the presence of nucleotidyl cyclases and cyclic nucleotide phosphodiesterases capable of their synthesis and breakdown. Here we describe the significant properties of cyclic nucleotides, also outlining their second messenger functions and the history of plant cyclic nucleotide research over its first three decades. Findings of the last five years are detailed within the context of the functional role of cyclic nucleotides in higher plants, with particular emphasis upon nucleotidyl cyclases and cyclic nucleotide-responsive protein kinases, -binding proteins and -gated ion channels, with future objectives and strategies discussed.

Cyclic AMP↗
PubMed2003

A study of the cough reflex in idiopathic pulmonary fibrosis.

Little is known about the pathogenesis of cough in idiopathic pulmonary fibrosis (IPF). We hypothesized that abnormalities of respiratory tract tachykinin-containing sensory nerves may be implicated. We studied cough response to capsaicin, substance P (SP), and bradykinin in 10 healthy control subjects and 10 patients with IPF. Six patients were tested before and after steroid therapy. Induced sputum cell counts and neurotrophic factor levels were also measured in 13 patients and 13 control subjects. The results show that cough sensitivity to capsaicin was greater in patients (p < 0.01). Neither SP nor bradykinin induced cough in normal subjects. SP and bradykinin induced cough in 7/10 patients (p < 0.002) and 2/10 patients (not significant) with IPF, respectively. Prednisolone caused a reduction in cough sensitivity to capsaicin (p < 0.05) and SP (p < 0.05) in all six patients treated. There were significantly more neutrophils (p = 0.001) and higher levels of nerve growth factor (p < 0.01) and brain-derived neurotrophic factor (p < 0.01) in patient's sputa. These findings suggest functional upregulation of lung sensory neurones in IPF. The cough response to inhaled SP in most patients may reflect disrupted respiratory epithelium. The response to corticosteroids demonstrates that the cough is amenable to therapy.

Aged↗
PubMed2003

Analysis of urinary nucleosides. III. Identification of 5'-deoxycytidine in urine of a patient with head and neck cancer.

Modified nucleosides in the urine have been postulated to be diagnostic indices of disease, particularly of cancer. The urine of a patient with terminal head and neck cancer has been found to contain a modified nucleoside with a protonated molecule of m/z 228. By means of high-performance liquid chromatography/ion trap mass spectrometry (HPLC/ITMS) and capillary liquid chromatography/triple quadruple mass spectrometry (CapLC/TQMS) we have identified the compound as 5'-deoxycytidine. This is the first report of 5'-deoxycytidine in man: in addition to the elucidation of its structure, its possible origins and the potential significance of its occurrence are discussed.

Chromatography, High Pressure Liquid↗
PubMed2002

Comparative study of human steroid 5alpha-reductase isoforms in prostate and female breast skin tissues: sensitivity to inhibition by finasteride and epristeride.

Steroid 5alpha-reductase (5-AR) catalyses the reduction of testosterone (T) to dihydrotestosterone (DHT). The 5alpha-reductase found in human benign prostatic hyperplasia (BPH) has been compared with that found in human breast skin tissue in respect of sensitivity to inhibition by Finasteride and Epristeride. Kinetic studies showed the presence of two isoforms of 5alpha-reductase in benign prostatic hyperplasia indicated by low and high Km isoforms for testosterone, while female breast skin tissue contained only one isoform. The isoforms differ in their affinity for the inhibitors Finasteride and Epristeride, both compounds being more effective for the low Km 5alpha-reductase isoform than the high Km 5alpha-reductase of prostatic tissue, with Finasteride displaying competitive inhibition and Epristeride uncompetitive. Finasteride and Epristeride are also inhibitors of skin 5alpha-reductase, which possesses a comparable Ki for Finasteride to that of the low Km prostatic enzyme, but Epristeride was a less potent inhibitor of the skin enzyme relative to the prostate isoform. These results suggest that the inhibitors have therapeutic potential, other than for treatment of benign prostatic hyperplasia, for treating skin disorders influenced by the action of dihydrotestosterone and warrant further investigation.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed2002

Cyclic nucleotide content of tobacco BY-2 cells.

The cyclic nucleotide content of cultured tobacco bright yellow-2 (BY-2) cells was determined, after freeze-killing, perchlorate extraction and sequential chromatography, by radioimmunoassay. The identities of the putative cyclic nucleotides, adenosine 3',5'-cyclic monophosphate (cyclic AMP), guanosine 3',5'-cyclic monophosphate (cyclic GMP) and cytidine 3',5'-cyclic monophosphate (cyclic CMP) were unambiguously confirmed by tandem mass spectrometry. The potential of BY-2 cell cultures as a model system for future investigations of cyclic nucleotide function in higher plants is discussed.

Cell Line↗