Search results for "CLEAVAGE"
showing 10 items of 281 documents
The Anaphylatoxic Peptide C3a of Guinea Pig Complement
1978
Abstract Highly purified guinea pig C3a was obtained after specific cleavage of isolated C3 by the alternative pathway enzyme VF-B in a one step procedure. It turned out to be a low molecular weight peptide with basic character (M.W. 9500; isoelectric point above 9.4). C3a represents an antigenetic determinant of its own in the native C3 molecule, different from the B determinant. Guinea pig C3a is resistant to 100°C for 10 minutes. Its smooth muscle contracting activity can be destroyed by trypsin and carboxypeptidase B. These findings indicate that guinea pig C3a is quite similar to human C3a.
Molecular response to TBT stress in marine sponge Suberites domuncula: proteolytical cleavage and phosphorylation of KRS_SD protein kinase
2003
Abstract Marine sponges as sessile filter feeders are inevitably under a constant influence of changes in their environment. Mediation of extracellular signals and regulation of cellular response to environmental stress is a key function of cellular protein kinases. Expression, proteolytical cleavage and phosphorylation of stress-responsive KRS_SD protein kinase, in control and tributyl-tin (TBT) treated sponges were investigated. In control sponge, two KRS_SD proteins were expressed: KRS_SD1 (54 kDa) corresponding to KRS_SD calculated molecular weight, and KRS_SD2 (50 kDa). Exposure of sponges to TBT resulted in alteration of KRS_SD1 and KRS_SD2 expression levels and their phosphorylation …
Cycloaddition reactions of benzothiete with azomethines
1986
Obtention de diaryl-2,3 dihydro-3,4 benzothiazines-1,3 (70%) via la cycloaddition de la thiobenzoquinone methode-1,2 (obtenue par scission thermique du benzothiete) et d'arylimines de benzaldehydes. Obtention egalement de 10% du dimere (dibenzo [b, f] dithiocinne-1,5)
ChemInform Abstract: Cycloaddition of Benzothiete and Electron-Deficient Nitriles.
2010
The o-quinoid 8π electron system 2, generated by thermal ring opening of benzothiete (1), enters regio-specific [8π + 2π] cycloaddition reactions with electron-deficient nitriles 3a-d, yielding the 4H-1,3-benzothiazines 4a-d. A competitive dimerization of 1 leads to 1,5-dibenzo[b,f]dithiocin (5). Depending on the nitrile further competitive or subsequent reactions (2 + 3b 7b, 2 + 3d 4d 8d) can occur. The cycloadducts 10e and 11e gained from 3e anticipate a primary cleavage of 3e to methylisothiocyanate 9e which reacts at the CN double bond as well as at the CS double bond.
Cycloaddition of benzothiete and electron-deficient nitriles
1991
The o-quinoid 8π electron system 2, generated by thermal ring opening of benzothiete (1), enters regio-specific [8π + 2π] cycloaddition reactions with electron-deficient nitriles 3a-d, yielding the 4H-1,3-benzothiazines 4a-d. A competitive dimerization of 1 leads to 1,5-dibenzo[b,f]dithiocin (5). Depending on the nitrile further competitive or subsequent reactions (2 + 3b 7b, 2 + 3d 4d 8d) can occur. The cycloadducts 10e and 11e gained from 3e anticipate a primary cleavage of 3e to methylisothiocyanate 9e which reacts at the CN double bond as well as at the CS double bond.
Heterocyclic rearrangements. Synthesis of 1,2,4-oxadiazolo[2,3-a]pyrimidinium systems and their ring opening into pyrimidineN-oxides
1986
Reaction des methyl- et phenyl-5 amino-3 oxadiazoles-1,2,4 avec l'acetylacetone ou la benzoylacetone en presence d'acide perchlorique: obtention de methyl- et phenyl-2 methyl- et phenyl-5 methyl-7 oxadiazolo [2,3-a] pyrimidiniums-4 qui se decyclisent ensuite en oxydes-1 d'acylamino-2- et amino-2 methyl-4 methyl- et phenyl-6 pyrimidines
Mass spectrometric investigation of polymers: Thermal degradation of truxillic and truxinic polyamides
1975
The thermal degradation mechanism of four isomeric truxillic and truxinic polyamides were investigated by direct pyrolysis in the ion source of a mass spectrometer. Thermal degradation reactions were followed directly by this method by detecting the thermal and electron impact-induced fragments. The results obtained have shown that the thermal degradation products are sensibly different for the head-to-head (hh) and head-to-tail (ht) polymers and that the predominant pyrolytic process is the cyclobutane ring cleavage. In the hh isomers, both symmetrical and asymmetrical cyclobutane ring cleavage was detected, while in the ht isomers only symmetrical cleavage occurs; this explains the notice…
Reversible, room-temperature C—C bond activation of benzene by an isolable metal complex
2019
The activation of C-C bonds is of fundamental interest in the construction of complex molecules from petrochemical feedstocks. In the case of the archetypal aromatic hydrocarbon benzene, C-C cleavage is thermodynamically disfavored, and is brought about only by transient highly reactive species generated in situ. Here we show that the oxidative addition of the C-C bond in benzene by an isolated metal complex is not only possible, but occurs at room temperature and reversibly at a single aluminium center in [(NON)Al]- (where NON = 4,5-bis(2,6-diisopropylanilido)-2,7-di-tert-butyl-9,9-dimethylxanthene). Selectivity over C-H bond activation is achieved kinetically and allows for the generation…
Addition reactions of heterocycles. VI. Reactions of 1,2-dimethylpyrrole and 1-methyl-2-carbomethoxypyrrole with nitrilimines
1978
Addition reactions of 1,2-dimethylpyrrole and 1-methyl-2-carbomethoxypyrrole with C-acetyl-N-phenylnitrilimine, have been investigated. 1,2-Dimethylpyrrole gives three different types of adducts: i.e. bis-cycloadducts (Vc) and (VIc), spirocycloadduct (IX), and non cyclic bis-adduct (XII). On the other hand, 1-methyl-2-carbomethoxypyrrole gives the bis-cycloadduct (VIb) only. Compound XII arises probably through a double 1,3-addition reaction, whereas the formation of cycloadducts Vc, VIc, and IX depends on the substituents present at C2 of the pyrrole ring and consequentially on the intermediary occurence of mono-cycloadduct (IIIc), its methylenic tautomer VII, VIc, and XL The behaviour of …
Umsetzung von amino-aziminen mit basen
1980
Abstract Amino-azimines of type (1) react at room temperature with bases (ammonia, aliphatic amines, hydrazine and methyl-hydrazine, aqueous/ethanolic sodium hydroxide) by cleavage of the to the and the NNN moieties (azide).