Search results for "Bifunctional"
showing 10 items of 123 documents
Conversion of the Sensor Kinase DcuS to the Fumarate Sensitive State by Interaction of the Bifunctional Transporter DctA at the TM2/PAS
2021
The membrane-bound C4-dicarboxylate (C4DC) sensor kinase DcuS of Escherichia coli typically forms a protein complex with the C4DC transporter DctA. The DctA × DcuS complex is able to respond to C4DCs, whereas DcuS without DctA is in the permanent ON state. In DctA, the C-terminal helix 8b (H8b) serves as the site for interaction with DcuS. Here the interaction site in DcuS and the related structural and functional adaptation in DcuS were determined. The Linker connecting transmembrane helix 2 (TM2) and the cytosolic PASC (Per-ARNT-SIM) domain of DcuS, was identified as the major site for interaction with DctA-H8b by in vivo interaction studies. The Linker is known to convert the piston-type…
2,8-Diazido-ATP — a short-length bifunctional photoaffinity label for photoaffinity cross-linking of a stable F1 in ATP synthase (from thermophilic b…
1995
Abstract To demonstrate the direct interfacial position of nucleotide binding sites between subunits of proteins we have synthesized the bifunctional photoaffinity label 2,8-diazidoadenosine 5′-triphosphate (2,8-DiN3ATP). UV irradiation of the F1-ATPase (TF1) from the thermophilic bacterium PS3 in the presence of 2,8-DiN3ATP results in a nucleotide-dependent inactivation of the enzyme and in a nucleotide-dependent formation of α-β crosslinks. The results confirm an interfacial localization of all the nucleotide binding sites on TF1.
Cooperative Assistance in Bifunctional Organocatalysis: Enantioselective Mannich Reactions with Aliphatic and Aromatic Imines
2012
both of which contain a thiourea moiety (Scheme 1).The catalysts are capable of deprotonating suitable nucleo-philes, such as activated carbonyl compounds. This proton-transfer reaction generates an ion pair, which is composed ofthe protonated catalyst and the anionic nucleophile interact-ing through hydrogen bonds. At least one of the NH moietiesin the protonated catalyst is involved in activating theelectrophilic reaction partner.
Combining reactive triblock copolymers with functional cross-linkers: A versatile pathway to disulfide stabilized-polyplex libraries and their applic…
2017
Therapeutic nucleic acids such as pDNA hold great promise for the treatment of multiple diseases. These therapeutic interventions are, however, compromised by the lack of efficient and safe non-viral delivery systems, which guarantee stability during blood circulation together with high transfection efficiency. To provide these desired properties within one system, we propose the use of reactive triblock copolypept(o)ides, which include a stealth-like block for efficient shielding, a hydrophobic block based on reactive disulfides for cross-linking and a cationic block for complexation of pDNA. After the complexation step, bifunctional cross-linkers can be employed to bio-reversibly stabiliz…
Synthesis and cytotoxic activity of a new potential DNA bisintercalator: 1,4-Bis{3-[N-(4-chlorobenzo[g]phthalazin-1-yl)aminopropyl]}piperazine
2010
The synthesis of new 1,4-bisalkylamino (2-4) and 1-alkylamino-4-chloro (5-6) substituted benzo[g]phthalazines is reported. Compounds 2-4 and 6 were prepared both in the free and heteroaromatic ring protonated forms. Bifunctional 6 contains the 1,4-bisaminopropylpiperazine chain as a linker between the two heteroaromatic units, whereas 5 is its monofunctional analogue. The in vitro antitumour activity of the synthesized compounds has been tested against human colon, breast and lung carcinoma cells, and also against human glioblastoma cells. Results obtained show that all of them are active in all cases, but bifunctional 6·2HCl is remarkably effective against the four cell lines tested, exhib…
Enantioselective Mannich reaction of β-keto esters with aromatic and aliphatic imines using a cooperatively assisted bifunctional catalyst
2014
An efficient urea-enhanced thiourea catalyst enables the enantioselective Mannich reaction between β-keto esters and N-Boc-protected imines under mild conditions and minimal catalyst loading (1–3 mol %). Aliphatic and aromatic substituents are tolerated on both reaction partners, affording the products in good enantiomeric purity. The corresponding β-amino ketones can readily be accessed via decarboxylation without loss of enantiomeric purity.
Microwave-Assisted Tandem Organocatalytic Peptide-Coupling Intramolecular aza-Michael Reaction: α,β-UnsaturatedN-Acyl Pyrazoles as Michael Acceptors
2014
Conjugated N-acyl pyrazoles have been successfully employed in the organocatalytic enantioselective intramolecular aza-Michael reaction as ester surrogates. Bifunctional squaramides under microwave irradiation provided the best results in this transformation. Furthermore, this protocol has been combined with a peptide-coupling reaction in a tandem sequence. The final products were easily converted into the corresponding ethyl esters.
New nanobiohybrid engineering composed of titanate nanoribbons for regenerative medicine
2012
This research work is devoted to new nanohybrid engineering composed of titanate nanoribbons for regenerative medicine. Over a first phase, nanoribbons were synthesized by hydrothermal treatment and their morphological, structural and chemical features were defined. A fine characterization by means of different techniques of transmission electron microscopy mainly enabled to determine their thickness; dimension which had never been measured so far. Subsequently, titanate nanoribbons were functionalized by different home-made heterobifunctional PEG. Those polymers present at one of their extremities specific functional groups being able to couple with numerous biological molecules. Some coll…
Heterocycles from α-aminonitriles.
2014
Owing to their various modes of reactivity, α-aminonitriles represent versatile building blocks for the construction of a wide range of nitrogen heterocycles. The present Concept article focuses on synthetic methodologies using their bifunctional nature which is the basis of their reactivity as α-amino carbanions and as iminium ions. Reactions exclusively taking place on either the amine or on the nitrile moiety will not be considered.
Ship-in-a-bottle synthesis of triphenylamine inside faujasite supercages and generation of the triphenylamminium radical ion
2005
Abstract The ship-in-a-bottle synthesis of triphenylamine encapsulated within basic X zeolite has been accomplished by reacting sodium diphenylamide with bromobenzene in the presence of a bifunctional palladium (Hartwig–Buchwald conditions). The presence of incarcerated triphenylamine was demonstrated by dissolving the zeolite with concentrated HF and analyzing the organic material in the dichloromethane extract. Laser flash photolysis (266 nm) gives rise to the generation of triphenylamminium radical cation detected as a transient species decaying in hundreds of microseconds. Upon repetitive cyclic voltammograms, zeolite encapsulated triphenylamine shows a reversible oxidation–reduction pr…