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At least 1,135 records · Page 63Linked to original sources
PubMed1991

Mass spectral analysis and fragment ion structure of fusarochromanone.

Fusarochromanone is a mycotoxin produced by Fusarium equiseti that is implicated in the poultry disease tibial dyschrondroplasia. Electron impact ionization tandem mass spectrometry was used to elucidate probable structures of fragment ions found at m/z 274, 275, 261, 233, 218 and 191 and for devising an analytical rationale for the metabolites of the parent compound. In addition, a sensitive, qualitative liquid chromatographic technique using direct injection continuous-flow fast atom bombardment for the detection of fusarochromanone in corn was devised. Analysis was carried out on a hybrid tandem instrument (VG-7070EQ) using open tubular columns (75 microns i.d.) with direct-flow open-loop injection. The limit of detection of the pure compound was 500 pg in the selected ion monitoring mode. A 50 p.p.b. (500 pg injected) of the pure compound added to ground corn samples was the lowest detectable amount in a biological matrix.

Amino Acids↗
PubMed1986

One- and two-dimensional NMR spectral analysis of the consequences of single amino acid replacements in proteins.

The traditional approach of using homologous sequences to elucidate the role of specific amino acid residues in protein structure and function becomes more meaningful as the number of differences is minimized, with the limit being alteration of a single residue. For small proteins in solution, NMR spectroscopy offers a means of obtaining detailed information about each residue and its response to a given change in the protein sequence. Extraction of this information has been aided by recent progress in spectrometer technology (higher magnetic fields, more sensitive signal detection, more sophisticated computers) and experimental strategies (new NMR pulse sequences including multiple-quantum and two-dimensional NMR methods). The set of avian ovomucoid third domains, which consists of the third domain proper plus a short leader (connecting peptide) and has a maximum of 56 amino acid residues, offers an attractive system for developing experimental methods for investigating sequence-structure and structure-function relationships in proteins. Our NMR results provide examples of sequence effects on pKa' values, average conformation, and internal motion of amino acid side chains.

Amino Acid Sequence↗
PubMed1977

GLC-mass spectral analysis of psilocin and psilocybin.

With the combined technique of GLC-mass spectrometry, psilocin and psilocybin, two hallucinogenic indoles, were analyzed as their trimethylsilyl derivatives. The method was applied to these two components in an extract of Psilocybe cubensis (Earle) Sing.

Basidiomycota↗
PubMed1978

GLC--mass spectral analysis of fungal metabolites.

Four metabolites, hispidin, bisnoryangonin, muscimole, and ibotenic acid, from potentially psychoactive mushrooms were analyzed by GLC--mass spectrometry as their trimethylsilyl derivatives. This method was applied to the first two compounds in Gymnopilus punctifolius (Peck) Singer and to the last two compounds in Amania pantherina (Fr.) Secr.

Agaricales↗
PubMed1983

Spectral analysis of the configuration and solution conformation of dihydrodigoxigenin epimers.

The C20 configuration and solution conformation of each epimer of dihydrodigoxigenin has been studied by circular dichroism (CD) and NMR spectroscopy. Results from the CD spectra indicate that the two epimers have opposite orientations of the beta-carbon in the lactone ring. This finding, together with X-ray crystallographic data from a separate study on the minor epimer, establishes the C20 configuration of the minor epimer as S and of the major epimer as R. NMR evidence indicates that the average lactone rotamer for the minor epimer has the C22 position located on the C12 side of the steroid nucleus, whereas the average lactone rotamer for the major epimer has the C21 position located on the C12 side of the steroid nucleus. Molecular models indicate that these are the least-hindered positions for the respective rotamers. Physical data characterizing the two epimers are provided.

Crystallization↗
PubMed1991

Characterization of the aqueous decomposition products of (+)1,2-bis(3,5-dioxopiperazinyl-1-yl)-propane (ICRF-187) by liquid chromatographic and mass spectral analysis.

High-performance liquid chromatography (HPLC) and fast atom bombardment mass spectrometry (FAB-MS) were employed to separate and identify the aqueous decomposition products of (+)1,2-bis(3,5-dioxopiperazinyl-1-yl)-propane (ICRF-187; 1), a drug active against several forms of human cancer and which also has recently been shown to display potent cardioprotective activity in patients treated with the antitumor antibiotic doxorubicin. Two reversed-phase HPLC columns were used to separate the hydrolysis products of 1, a Waters muBondapak phenyl column and an LKB Spherisorb ODS2 column. Incubation of 20 microM 1 in phosphate-buffered saline (PBS) at 37 degrees C for 21 h resulted in 47% decomposition, with three hydrolysis products detected (compound 2, Waters column retention time (RT) = 3.7 min, observed monoisotopic protonated molecular ion (MH+) m/z value of 305.1; compound 3, RT = 4.1 min, MH+ m/z value of 287.1; compound 4, RT = 4.8 min, MH+ m/z value of 287.1). The RT and MH+ m/z values for 1 were 17.1 min and 269.1, respectively. Based on the FAB-MS data, 2 corresponds to ICRF-198, the polar diacid diamide derivative of 1, while peaks 3 and 4 represent the monoacid monoamide derivatives of 1. Using B/E linked scan daughter FAB-MS analysis, 3 displayed a prominent fragment with a m/z value of 160, indicating that it corresponds to the monoacid monoamide derivative of 1, with the methyl group adjacent to the hydrolyzed ring. Compound 4, displaying a fragment with a m/z value of 142 in its B/E linked scan daughter ion spectrum, corresponds to the monoacid monoamide derivative of 1, with the methyl group adjacent to the closed ring.

Chromatography, High Pressure Liquid↗
PubMed2006

1H, 13C, and 73Ge NMR spectral analysis of substituted aryltrimethylgermanes.

NMR chemical shifts of 1H, 13C, and 73Ge are reported for a series of monosubstituted aromatic trimethylgermanes of the type XC6H4Ge(CH3)3; X = p-N(CH3)2, p-OCH3, p-OC2H5, p-C(CH3)3, p-Si(CH3)3, p-Ge(CH3)3, p-Sn(CH3)3, p-CH3, m-CH3, -H, m-OCH3, p-Cl, p-Br, m-F, m-CF3, p-CF3, o-OCH3, and o-CH3. The relatively narrow 73Ge resonances show a strong correlation with Hammett sigma constants, with a correlation coefficient of 0.976 and 0.876 for 73Ge chemical shifts in meta- and para-substituted derivatives, respectively. The 13C chemical shifts of the methyl carbons bonded to germanium also display a relationship, with correlation coefficients of 0.904, 0.993, and 0.911 for para-, meta- and all derivatives, respectively. Comparisons of the Hammett plots for the homologous series XC6H4M(CH3)3; M = C, Si, Ge, Sn, show that, in general, correlation coefficients decrease while slopes increase significantly down the group, presumably reflecting the corresponding increase in chemical shift range of the group 14 atom. The Hammett constant derived for the p-Ge(CH3)3 group of +0.13 compares with the NMR-derived constants of -0.12 for p-C(CH3)3, +0.14 for p-Si(CH3)3, and -0.14 for p-Sn(CH3)3. The indication of electron release by carbon and tin can be rationalized through traditional hyperconjugative arguments for carbon and by the low electronegativity and consequent inductive effect of tin. The small electron attraction suggested by the positive constants for silicon and germanium can be simply, and perhaps naively, attributed to pi-acceptor interactions with the benzene ring.

Journal Article↗
PubMed1989

31P NMR Bayesian spectral analysis of rat brain in vivo.

Bayesian spectrum analysis for parameter estimation is a rigorous statistical (non-Fourier-based) method. Herein the Bayesian quadrature NMR model is introduced and applied to analysis of 31P NMR time domain data from in vivo rat brain. Immunity to both the brain spectrum "baseline hump" and the phase twist is demonstrated.

Animals↗
PubMed1990

NMR spectral analysis of kinetic data using natural lineshapes.

An automated rapid data analysis scheme for NMR spectroscopy time course studies is presented. This method uses a high signal-to-noise reference spectrum collected at the beginning of a time course as a lineshape model to analyze subsequent low signal-to-noise data collected with higher time resolution. The method is fast (approximately 1 s to evaluate two peaks in a 2K spectrum) and easily implemented on NMR spectrometer computers. An application of this method to spectroscopic studies on the heart is provided.

Humans↗
PubMed2002

Electron ionisation mass spectral analysis and fragmentation pathways for some thiophosphorylic p-carboxybenzene sulfonamides.

The work presents the 70 eV electron impact mass spectra of some thiophosphorylic p-carboxybenzene sulfonamides, and proposes rationalisation of their fragmentation pathways. Accurate mass measurements of the fragment ions, and metastable ion analyses performed in the MIKES mode, were used to elucidate the most abundant ion compositions and to elucidate the fragmentation patterns of these pharmacologically interesting compounds.

Journal Article↗
PubMed2001

Mass spectral analysis of asymmetric hemoglobin hybrids: demonstration of Hb FS (alpha2gammabetaS) in sickle cell disease.

Formation of the asymmetric hemoglobin hybrid FS (alpha2gammabetaS) inhibits hemoglobin S (Hb S) polymerization in vitro and underlies the protective effect of fetal hemoglobin (Hb F) in homozygous sickle cell disease. Conventional methods for separating Hb reveal only symmetric Hb tetramers because of the rapid dissociation of tetramers to dimers relative to the separation time for electrophoresis and chromatography. To gain insight into the quantitative distribution of asymmetric Hb FS and other tetrameric species in sickle cell disease, the noncovalent association of Hb subunits in hemolysates was studied by a novel application of electrospray ionization mass spectrometry (ESI-MS). Mass spectra of both patient and fetal blood revealed predominance of tetrameric species with dimer and monomer subunits in lower abundance. ESI-MS analysis revealed the hybrid Hb AF (alpha2gammabetaA) in hemolysates shown by conventional high-performance liquid chromatography to contain only the symmetric species Hb A (alpha2betaA2) and Hb F (alpha2gamma2). A unique tetramer of average mass 64,558 Da was identified in hemolysates from patients with sickle cell disease in accordance with the calculated mass of the asymmetric Hb hybrid FS. Hybrid Hb species were stable under the ESI-MS conditions employed allowing concurrent determination of the proportions of Hb FS and the symmetrical Hb S (alpha2betaS2). The ratios of Hb FS to Hb S correlated closely (r2 = 0.96) with those predicted under physiological conditions.

Adolescent↗
PubMed1999

Design of a PC-based system for time-domain and spectral analysis of heart rate variability.

Investigation of heart rate variability is the subject of considerable interest in physiology, clinical medicine, and clinical pharmacology. The functional assessment of the autonomic nerve system by observation of its main actors, the sympathetic and parasympathetic branch, is emphasizing the importance of autonomic regulation under different physiological circumstances, in several disease states, and under drug therapy. This paper describes a PC-based system designed with LabView that performs time-domain and frequency-domain analyses of heart rate variability as suggested by the guidelines of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology. Examples for heart rate variability are given for different physiological states along with an analysis and evaluation by the system described.

Algorithms↗
PubMed2000

Mass spectral analysis of a protein complex using single-chain antibodies selected on a peptide target: applications to functional genomics.

Genome projects are identifying an ever-increasing number of genes, accelerating the need for reagents to study the expression of these genes and elucidate the function and cellular location of the gene products. Our goal was to develop a strategy to allow human single-chain variable fragment (scFv) antibodies to be used for these endeavors. A library containing 7x10(9) individual variants was displayed by bacteriophage and selected against a biotinylated peptide corresponding to the C-terminal 15 amino acid residues of Ku86, one component of a heterodimer involved in double-stranded DNA break repair. Four unique scFv antibodies were recovered that not only recognized the selected peptide, but also the intact protein. Three of the scFv antibodies were expressed in soluble form and recognized Ku86 by Western analysis. The affinity of one of the scFv antibodies for Ku86 was 16 nM as measured by BIAcore analysis. scFv immunoprecipitation of Ku86 also isolated the other component of the heterodimer, Ku70, as determined by Western analysis and mass spectrometry. These results demonstrate the utility of scFv antibodies as invaluable reagents for functional genomics.

Antibodies↗