Search results for "CLEAVAGE"
showing 10 items of 281 documents
The crystal structure of a 250-kDa heterotetrameric particle explains inhibition of sheddase meprin β by endogenous fetuin-B
2021
Meprin β (Mβ) is a multidomain type-I membrane metallopeptidase that sheds membrane-anchored substrates, releasing their soluble forms. Fetuin-B (FB) is its only known endogenous protein inhibitor. Herein, we analyzed the interaction between the ectodomain of Mβ (MβΔC) and FB, which stabilizes the enzyme and inhibits it with subnanomolar affinity. The MβΔC:FB crystal structure reveals a ∼250-kDa, ∼160-Å polyglycosylated heterotetrameric particle with a remarkable glycan structure. Two FB moieties insert like wedges through a “CPDCP trunk” and two hairpins into the respective peptidase catalytic domains, blocking the catalytic zinc ions through an “aspartate switch” mechanism. Uniquely, the …
Search for potential Angiotensin Converting Enzyme (ACE)-inhibitors from plants
2001
MeOH extracts, fractions and pure substances from Musanga cecropioides, Cecropia species and Crataegus oxyacantha /C. monogyna were screened by using an in vitro bio-assay based on the inhibition of Angiotensin Converting Enzyme (ACE), as measured from the enzymatic cleavage of the chromophore-fluorophore-labelled substrate dansyltriglycine into dansylglycine and diglycine. Phenolic acids showed no significant ACE-inhibition whereas flavonoids and proanthocyanidins demonstrated inhibitory activity at 0.33 mg/ml using this test system.
Radical Polymerization of Styrene Controlled by Half-Sandwich Mo(III)/Mo(IV) Couples: All Basic Mechanisms Are Possible
2001
Density functional calculations of bond dissociation energies (BDEs) have been used as a guide to the choice of metal system suitable for controlling styrene polymerization by either the stable free radical polymerization (SFRP) or the atom transfer radical polymerization (ATRP) mechanism. In accord with the theoretical prediction, CpMo(eta(4)-C(4)H(6))(CH(2)SiMe(3))(2), 2, is not capable of yielding SFRP of styrene. Still in accord with theoretical prediction, CpMo(eta(4)-C(4)H(6))Cl(2), 1, CpMo(PMe(3))(2)Cl(2), 3, and CpMo(dppe)Cl(2) (dppe = 1,2-bis(diphenylphosphino)ethane), 4, yield controlled styrene polymerization by the SFRP mechanism in the presence of 2,2'-azobisisobutyronitrile (A…
(1,3,4‐Oxadiazole)copper(II) Compounds: Dimensionality, Magnetism and Nuclease Activity
2009
The work presented here describes the synthesis of new copper(II) complexes derived from 2-amino-5-(pyridin-2-yl)-1,3,4-oxadiazole (L1) and 2-methylamino-5-(pyridin-2-yl)-1,3,4-oxadiazole (L2) which also incorporate azido (N3 -), thiocyanato (NCS-), cyanato (NCO-), dicyanamido [N(CN)2 -, dca] and malonato (C3H2O4 2-, mal) coligands. Structures of the [Cu(L2)(mal)(H2O)]·2H 2O(1), [{Cu(L2)(mal)}2] (2), [Cu(L 2)2-(NCS)2] (3), [Cu(L1)(NCS) 2]n (4) and [{Cu(L2)}2(dca) 2](ClO4)2·2H2O (5) compounds show the dependence of the dimensionality on parameters such as the type of oxadiazole and coligand utilised, solvents or reaction times. In this sense, 1 and 3 are mononuclear complexes, 2 contains cen…
Synthesis ofN-Tosylguanidinesby Ring Cleavage of 1,2-Dihydro-2-tosyliminopyrimidines
2003
The present communication discloses a new synthetic method for the preparation of N-tosylguanidines in high yields by ring cleavage of 1,2-dihydro-2-tosyliminopyrimidines with methyl- amine.
Organometallic complexes with biological molecules. X: dialkyltin(IV) and trialkyltin(IV) orotates: spectroscopic andin vivo investigations
1999
Several novel diorgano- and triorgano-tin(IV) derivatives of orotic acid, (2,6-dihydroxypyrimidine-4-carboxylic acid; H 3 or) have been synthesized. In the diorganotin(IV) derivatives, the orotic acid behaved either as a monoanionic or as a dianionic ligand, yielding R 2 Sn(H 2 or) 2 and R 2 SnHor (R = Me, Bu) species, respectively, while in the triorganotin(IV) orotates only monodeprotonation of the orotic acid occurred, giving R 3 SnH 2 or (R = Me, Bu) derivatives. Structural hypotheses are proposed and discussed for the solid state based on Mossbauer and IR spectroscopic data, and for solution on 1 H and 1 C NMR results. Finally, investigations have been carried out in vivo, showing the …
Untersuchungen über den Einfluss verschiedener Kationen auf die ATP-Spaltung durch die Zytoplasmafraktion vom Plexus chorioideus des Rindes
1967
The cytoplasma fraction of the bovine choroid plexus epithelial cells was found to contain a considerable ATPase activity. The influence of Na+, K+, Li+, Rb+, Cs+, Co++, Mn++, Zn++ and Fe+++ on the activity of the Mg++-dependent enzyme has been studied. The monovalent cations do not influence the enzymic activity, whereas the effect of the bi- and trivalent cations is characterized by an inhibition of the ATPase.
1,3-Alternate calix[4]arenes, selectively functionalized by amino groups
2004
General strategies are described to synthesize calix[4]arenes which are fixed in the 1,3-alternate conformation and substituted selectively by amino groups. These derivatives are useful starting materials for the attachment of various groups via amide bonds, as demonstrated by several examples, but may be converted also to ureas, imides or azomethines. Four amino groups may be attached to the narrow rim via(several) methylene groups as spacer by O-alkylation with omega-bromophthalimides or omega-bromonitriles. From the resulting tetraethers the amino functions are obtained by cleavage with hydrazine or by hydrolysis, allowing a selective functionalisation of both sides of the molecule (phen…
Enantioselective Total Syntheses of (+)-Hippolachnin A, (+)-Gracilioether A, (-)-Gracilioether E, and (-)-Gracilioether F.
2018
The Plakortin polyketides represent a structurally and biologically fascinating class of marine natural products. Herein, we report a unified strategy that enables the divergent syntheses of various Plakortin polyketides with high step-economy and overall efficiency. As proof-of-concept cases, the enantioselective total syntheses of (+)-hippolachnin A, (+)-gracilioether A, (-)-gracilioether E, and (-)-gracilioether F have been accomplished based on a series of bio-inspired, rationally designed, or serendipitously discovered transformations, which include (1) an organocatalytic asymmetric 1,4-conjugate addition to assemble the common chiral γ-butenolide intermediate enroute to all of the afo…
Antivirale Wirkstoffe, 18. Mitt. 2-Aminothiazole durch Spaltung der S-S-Bindung des Disulfidodicarbamidins
1981
Bei der Umsetzung von Disulfidodicarbamidin (1) mit β-Diketonen 2 werden sowohl (2-Amino-5-thiazolyl)ketone 3 als auch 2,2′-Dithiobispyrimidine 4 und Pyrimidinthione 5 gebildet. Unter Verwendung von Ethanol/Kaliumcarbonat entstehen bei Raumtemp. sowohl aus aliphatisch symmetrisch (2a–c) als auch aus aliphatisch unsymmetrisch (2d) substsituierten, ferner aus fluorierten (2e) β-Diketonen, die korrespondierenden (2-Amino-5-thiazolyl)ketone 3a–e als Hauptprodukte. Antiviral Drugs, XVIII: 2-Aminothiazoles by Cleavage of the S-S-Bond of Disulfidodicarbamidine Through the interaction of disulfidodicarbamidine (1) with β-diketones 2, (2-amino-5-thiazolyl)ketones 3 as well as 2,2′-dithiobispyrimidin…