Search results for "Spectrometry"
showing 10 items of 3206 documents
Massenspektrometrische Untersuchungen an 4(5)-Hydroxymethyl-imidazolen
1979
Es wurden 12 unterschiedlich substituierte Hydroxymethylimidazole massenspektrometrisch untersucht und die charakteristischen Schlusselbruchstucke beschrieben. Fur den Zerfall von 4(5)-Hydroxymethyl-imidazol (1) und 5-Hydroxymethyl-1-methyl-imidazol (8) werden Fragmentierungsschemata angegeben. Mass Spectrometry of 4(5)-Hydroxymethylimidazoles 12 substituted hydroxymethylimidazoles were investigated by mass spectrometry. The characteristic fragments are described. Schemes for the fragmentation of 4(5)-hydroxymethylimidazole (1) and 5-hydroxymethyl-1-methylimidazole (8) are reported.
Mass spectrometry of 3,4-dihydroquinazolin-4-ones of pharmaceutical interest. Part3. Electron ionization mass spectra of 2-substituted-3-(5′-pyrazoly…
1992
The fragmentation reactions induced by electron impact of eighteen title compounds has been investigated with the aid of low beam energy spectra (14 eV, nom. value), metastable ion detection, high resolution measurements and labelling experiments. The loss of the 4-carbonyl oxygen together with the 3-substituent, which constitutes a characteristic fragmentation route of 3-aryl and 3-heteroaromatic substituted-4(3H)-quinazolinones, is again observed, but the presence of a carboxyethyl group at the 4′-position of the pyrazole ring is responsible of an anomalous loss of 47 daltons from the molecular ion. Lastly, a comparison with the previously described behaviour of 3-(5′-isoxazolyl) derivati…
Über den thermischen abbau des poly(ɛ-caprolacton)s
1977
The thermal and electron impact induced degradation reactions of poly(e-caprolactone) {poly[oxy(1-oxohexamethylene)]} were investigated in a mass spectrometer. It can be shown that the favorated thermal degradation reaction is the cleavage of the ester bond and formation of ω-hydroxyl and ketene endgroups (Eq. (iii)) and with a lower intensity the cleavage of the OCH2-bond and formation of carboxyl-and pentenyl endgroups (Eq. (vii)). After electron impact and fragmentation of the pyrolysis products to carboxonium ions an elimination of caprolactone via a “zip”-mechanism can be observed (Eq. (v)).
Absolute cross-sections for the nonresonant multi-photon ionization of toluene and xylene in the gas phase
2001
Abstract The absolute multi-photon ionization cross-section of the phenyl ring was determined by laser-ionization of toluene and xylene molecules in the gas phase. Excitation was achieved using nonresonant four-photon absorption of the frequency doubled light of a 10 ns pulsed Nd:YAG laser (532 nm). The resulting ions were stored in a Penning trap and detected by time-of-flight mass spectrometry. The values of the cross-sections are 1.4(3)×10 −42 cm 8 W −4 s −1 and 1.3(3)×10 −42 cm 8 W −4 s −1 for toluene and xylene, respectively.
Introduction of a luminescent sensor for tracking trace levels of hydrazine in insect pollinated cropland flowers
2021
In recent years the excessive use of hydazine containing chemical pesticides and insecticides in farming practices is well pronounced, which directly or indirectly impart a great threat towards the total environment. Considering the above fact we are motivated to introduce a new, efficient and simple chemodosimeter (NCD) based on a carbazole-naphthalimide framework to recognize and estimate the mutagenic hydrazine within several affected cropland flowers. Probe NCD can detect hydrazine in a nanomolar range (65 nM or 2 ppb) in the presence of other metal ions, anions and amines, which gives it not only great potential but also makes it selective and sensitive. The sensing mechanism is confir…
Volatile Constituents ofTeucrium poliumL. from Turkey
1998
Abstract The volatile constituents obtained from the aerial parts of Teucrium polium were analyzed by GC and GC/MS. The oil was found to contain 37 components, of which 30 were identified. The major constituents were β-pinene (18.0%), β-caryophyllene (17.8%), α-pinene (12.0%), caryophyllene oxide (10.0%), myrcene (6.8%) and germacrene-D (5.3%)
Depth profiling of Pu, 241Am and 137Cs in soils from southern Belarus measured by ICP-MS and alpha- and gamma-spectrometry
2003
The depth distribution of plutonium, americium, and Cs-137 originating front the 1986 accident at the Chernobyl Nuclear Power Plant (NPP) was investigated in several soil profiles in the vicinity from Belarus. The vertical migration of transuranic elements in soils typical of the 30 km relocation area around Chernobyl NPP was studied using inductively coupled plasma mass spectrometry (ICP-MS), alpha spectrometry, and gamma spectrometry. Transuranic concentrations in upper soil layers ranged from 6 x 10(-12) g g(-1) to 6 x 10(-10) g g(-1) for plutonium and from 1.8 x 10(-13) g g(-1) to 1.6 x 10(-11) g g(-1) for americium. These concentrations correspond to specific activities of Pu239+240 of…
S-type lectins occur also in invertebrates: high conservation of the carbohydrate recognition domain in the lectin genes from the marine sponge Geodi…
1993
The marine sponge Geodia cydonium contains several lectins. The main component, called lectin-1, is composed of three to four identical subunits. The subunits of the lectins were cloned from a cDNA library; two clones were obtained. From the deduced aa sequence of one clone, LECT-1, a mol. wt of 15,313 Da is calculated; this value is in good agreement with mass spectrometric analysis of 15,453 +/- 25 Da. The sequence of another clone, LECT-2, was analysed and the aa sequence was deduced (15,433 Da). The two subunits have a framework sequence of 38 conserved aa which are characteristic for the carbohydrate-binding site of vertebrate S-type lectins. Clustering of lectin sequences of various s…
Methionine in a protein hydrophobic core drives tight interactions required for assembly of spider silk
2019
Web spiders connect silk proteins, so-called spidroins, into fibers of extraordinary toughness. The spidroin N-terminal domain (NTD) plays a pivotal role in this process: it polymerizes spidroins through a complex mechanism of dimerization. Here we analyze sequences of spidroin NTDs and find an unusually high content of the amino acid methionine. We simultaneously mutate all methionines present in the hydrophobic core of a spidroin NTD from a nursery web spider’s dragline silk to leucine. The mutated NTD is strongly stabilized and folds at the theoretical speed limit. The structure of the mutant is preserved, yet its ability to dimerize is substantially impaired. We find that side chains of…
Evidence of oxidative stress in very long chain fatty acid--treated oligodendrocytes and potentialization of ROS production using RNA interference-di…
2011
X-linked adrenoleukodystrophy (X-ALD) and pseudo neonatal adrenoleukodystrophy (P-NALD) are neurodegenerative demyelinating diseases resulting from the functional loss of the peroxisomal ATP-binding cassette transporter D (ABCD1) and from single peroxisomal enzyme deficiency (Acyl-CoA oxidase1: ACOX1), respectively. As these proteins are involved in the catabolism of very long chain fatty acids (VLCFA: C24:0, C26:0), X-ALD and P-NALD patients are characterized by the accumulation of VLCFA in plasma and tissues. Since peroxisomes are involved in the metabolism of reactive oxygen species (ROS) and nitrogen species (RNS), we examined the impact of VLCFA on the oxidative status of 158N murine o…