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11.
Zusammenfassung Die Bedingung für das Auftreten einer Verzweigung bei einem beliebigen festen Körper wird allgemein für den Fall diskutiert, dass Teile der Oberfläche unter einer druckartigen Belastung stehen. Besondere Beachtung wird der Frage der Eindeutigkeit bei konventionellen plastischen Körpern geschenkt und mit Beispielen illustriert. Die Formel mit dem Tangentenmodul für das Beulen einer langen dünnwandigen Zylinderschale unter sehr flüssigem Druck wird verbessert. 相似文献
12.
Dr. Kenta Arai Takahiko Matsunaga Haruhito Ueno Nozomi Akahoshi Yuumi Sato Dr. Gaurango Chakrabarty Prof. Dr. Govindasamy Mugesh Prof. Dr. Michio Iwaoka 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(55):12751-12760
At the redox-active center of thioredoxin reductase (TrxR), a selenenyl sulfide (Se−S) bond is formed between Cys497 and Sec498, which is activated into the thiolselenolate state ([SH,Se−]) by reacting with a nearby dithiol motif ([SHCys59,SHCys64]) present in the other subunit. This process is achieved through two reversible steps: an attack of a cysteinyl thiol of Cys59 at the Se atom of the Se−S bond and a subsequent attack of a remaining thiol at the S atom of the generated mixed Se−S intermediate. However, it is not clear how the kinetically unfavorable second step progresses smoothly in the catalytic cycle. A model study that used synthetic selenenyl sulfides, which mimic the active site structure of human TrxR comprising Cys497, Sec498, and His472, suggested that His472 can play a key role by forming a hydrogen bond with the Se atom of the mixed Se−S intermediate to facilitate the second step. In addition, the selenenyl sulfides exhibited a defensive ability against H2O2-induced oxidative stress in cultured cells, which suggests the possibility for medicinal applications to control the redox balance in cells. 相似文献
13.
Yuanming Li Dr. Shyamal Chakrabarty Dr. Christian Mück‐Lichtenfeld Prof. Dr. Armido Studer 《Angewandte Chemie (International ed. in English)》2016,55(2):802-806
A novel and efficient approach to ortho‐trialkylstannyl arylphosphanes by the reaction of arynes generated in situ with stannylated phosphanes (R3Sn? PR2) is described. Concurrent C? P and C? Sn bond formation occurs with high yields, and stannylated products are easily transformed into valuable ortho‐substituted arylphosphanes. The reaction features high efficiency, good regioselectivity, and excellent practicality. 相似文献
14.
Anirbandeep Bose Uttam Bhaumik Animesh Ghosh Bappaditya Chatterjee Uday Sankar Chakrabarty Amlan Kanti Sarkar Tapan Kumar Pal 《Chromatographia》2009,69(11-12):1233-1241
A rapid, simple, sensitive and specific liquid chromatography–tandem mass spectrometry method was developed and validated for simultaneous quantification of itopride hydrochloride and domperidone in human plasma. Both drugs were extracted by liquid–liquid extraction with ethyl acetate and saturated borax solution. The chromatographic separation was performed on a reversed-phase C18 column with a mobile phase of water–methanol (2:98, v/v) containing 0.5% formic acid. The protonated analyte was quantitated in positive ionization by multiple reaction monitoring with a mass spectrometer. The assay exhibited linearity over the concentration range of 3.33–500 ng mL?1 for itopride hydrochloride and 3.33–100 ng mL?1 for domperidone in human plasma. The precursor to product ion transitions of m/z 359.1–72.3 and 426.0–147.2 were used to measure itopride hydrochloride and domperidone respectively. The method was found suitable for the analysis of plasma samples collected during phase 1 pharmacokinetics study of itopride HCl 50 mg and domperidone 20 mg in 12 healthy volunteers after single oral doses of the combination drug. 相似文献
15.
1-Benzenesulfonyl-5-aminoindole 5, prepared from 5-nitroindole 3, was condensed with alkyl isothiocyanates and separately with carbon disulfide and alkyl bromides/iodides to furnish efficiently the corresponding N-alkyl-thioureidoindoles 6a-c and the alkyl N-(indol-5′-yl)dithiocarbamates 9a-e, respectively. Their cyclisation using N-bromosuccinimide (NBS) and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), in the cold, followed by indolic N-deprotection, furnished regioselectively the 2-alkylamino- and the 2-alkylthiothiazolo[5,4-e]indoles 8a-c and 11a-e, respectively, in good overall yields. 相似文献
16.
We report herein a pseudo-crown based fluorescent receptor (1) for the selective detection of Cu2+ cation. Receptor 1 can detect Cu2+ even in 5 μM level in acetonitrile-water (9:1 v/v). Compound 1 is very effective for the detection of Cu2+ amongst the series of metal ions studied (Li+, Na+, K+, Ca2+, Mg2+, Ba2+, Pb2+, Fe3+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg2+ and Mn2+). 相似文献
17.
Shyamaprosad Goswami Subrata Jana Rinku Chakrabarty Hoong-Kun Fun 《Supramolecular chemistry》2013,25(3):143-148
A guanidine-based fluorescent receptor has been synthesised to study its binding behaviour towards anions (F? , Cl? , Br? , I? and AcO? ). The two donor N–H bonds of the receptor do not point in the same direction; rather, one N–H bond is intramolecularly hydrogen-bonded with the carbonyl oxygen atom. The nature of the donor–acceptor (DA) arrangement induces moderate binding properties. The binding behaviour towards monocarboxylic acids (benzoic acid and phenylacetic acid) is also compared. The binding behaviour of receptor 1 towards the F? anion is higher among the anions studied, whereas in the case of monocarboxylic acid, the binding constant with phenylacetic acid is higher than benzoic acid. 相似文献
18.
M. Chakrabarty A. Batabyal M. S. Morales-Ríos P. Joseph-Nathan 《Monatshefte für Chemie / Chemical Monthly》1995,126(6-7):789-794
Summary Unambiguous1H and13C NMR assignments for 4(3H)-quinazolinones1–6 and their corresponding 4-thiones7–12 have been made. This resulted in the revision of the previous assignments for the two benzenoid carbons (C-5 and C-8) of quinazolinones1,2,4, and5. Thionation of the nucleophilic amides1–6 has been found to cause a distinct change in the13C chemical shift of particularly C-4, but also of those of C-4a, C-5, and C-8a. One-bond and several long range heteronuclear coupling constants for the compounds have also been measured.
Kernresonanzspektroskopie von 4(3H)-Chinazolinonen und 4(3H)-Chinazolinthionen
Zusammenfassung Die1H- und13C-NMR-Spektren der 4(3H)-Chinazolinone1–6 und ihrer entsprechenden 4-Thione7–12 wurden zugeordnet. Dabei zeigte sich, daß eine frühere Zuordnung der beiden benzoiden Kohlenstoffe (C-5 und C-8) der Chinazolinone1,2,4 und5 falsch war. Ersatz des Sauerstoffs durch Schwefel in den nukleophilen Amiden1–6 führt insbesondere für C-4, aber auch für C-4a, C-5 und C-8a zu einer deutlichen Änderung der chemischen Verschiebung. Heteronukleare Kopplungskonstanten über eine und über mehrere Bindungen wurden bestimmt.相似文献
19.
20.
Sulphonated styrene-divinylbenzene resins with various cross-linking have been synthesized and the dehydration of 2-butanol
has been studied on these acid catalysts. The pore structure of the resin controls the rate of dehydration. Thecis totrans ratio of the 2-butene formed indicate that the resin catalysts behave like aqueous solution of acids, i.e.dissociated protons
are responsible for catalysis. 相似文献