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Recognition Units (recognition + unit)

Distribution by Scientific Domains

Chemistry	80%

Selected Abstracts

Drug targeting by macromolecules without recognition unit?

JOURNAL OF MOLECULAR RECOGNITION, Issue 5 2003
Ferenc Hudecz
Abstract his review will summarize available information on the ability of macromolecular conjugates containing no specific recognition motifs to deliver anthracyclines (daunomycin, adriamycin) or methotrexate to target cells such as tumour cells or macrophages. Conjugates with natural (proteins, DNA, carbohydrates) and synthetic macromolecules (linear and branched chain poly-,-amino acids, non-biodegradable DIVEMA, HPMA etc.) will be reviewed. Experimental data from several laboratories indicate that these conjugates are taken up by cells mainly by fluid-phase or adsorptive endocytosis. It is believed that these processes do not involve ,specific receptors'. Two examples of methotrexate and daunomycin conjugates will be discussed to show the effect of the chemical structure of branched chain polypeptides on the uptake and antitumour or antiparasitic (Leishmania donovani infection) efficacy of conjugates. Copyright © 2003 John Wiley & Sons, Ltd. [source]

N - tert -Butyl- N,-(5,7-dimethyl-1,8-naphthyridin-2-yl)urea

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 8 2001
Ulrich Lüning
The title compound, C15H20N4O, has been synthesized as an AADD recognition unit for quadruple hydrogen bonds. All non-H atoms of the molecule apart from two methyl groups of the tert -butyl group lie in a common plane. An intramolecular hydrogen bond is formed connecting two N atoms. In the solid state, the title compound crystallizes as a centrosymmetric dimer connected by N,H,O=C interactions with an N,O distance of 2.824,(2),Å. [source]

Syntheses of Triostin A Antibiotic and Nucleobase-Functionalized Analogs as New DNA Binders

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 28 2009
Anmol Kumar Ray
Abstract A total synthesis of the natural product triostin A, wherein the N -methylated depsipeptide scaffold is constructed by solution-phase peptide chemistry followed by disulfide formation and macrocyclization, is described. Finally, the quinoxalines were attached to provide the DNA bisintercalator. Analogs of triostin A were obtained by the successive functionalization of the cyclic depsipeptide with pyrimidine or purine recognition units. The attachment of functional units was achieved by the orthogonal protection of the respective side chain amino functionalities. The nucleobase-functionalized triostin analogs have the potential to recognize double-stranded DNA by hydrogen bonding. The interaction with DNA was investigated by UV spectroscopy and fluorescence intercalator displacement. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

What's special about personally familiar faces?

PSYCHOPHYSIOLOGY, Issue 5 2004
A multimodal approach
Abstract Dual-route models of face recognition suggest separate cognitive and affective routes. The predictions of these models were assessed in recognition tasks with unfamiliar, famous, and personally familiar faces. Whereas larger autonomic responses were only triggered for personally familiar faces, priming effects in reaction times to these faces, presumably reflecting cognitive recognition processes, were equal to those of famous faces. Activation of stored structural representations of familiar faces (face recognition units) was assessed by recording the N250r component in event-related brain potentials. Face recognition unit activation increased from unfamiliar over famous to personally familiar faces, suggesting that there are stronger representations for personally familiar than for famous faces. Because the topographies of the N250r for personally and famous faces were indistinguishable, a similar network of face recognition units can be assumed for both types of faces. [source]

Ground-State Equilibrium Thermodynamics and Switching Kinetics of Bistable [2]Rotaxanes Switched in Solution, Polymer Gels, and Molecular Electronic Devices

CHEMISTRY - A EUROPEAN JOURNAL, Issue 1 2006
Jang Wook Choi
Abstract We report on the kinetics and ground-state thermodynamics associated with electrochemically driven molecular mechanical switching of three bistable [2]rotaxanes in acetonitrile solution, polymer electrolyte gels, and molecular-switch tunnel junctions (MSTJs). For all rotaxanes a ,-electron-deficient cyclobis(paraquat- p -phenylene) (CBPQT4+) ring component encircles one of two recognition sites within a dumbbell component. Two rotaxanes (RATTF4+ and RTTF4+) contain tetrathiafulvalene (TTF) and 1,5-dioxynaphthalene (DNP) recognition units, but different hydrophilic stoppers. For these rotaxanes, the CBPQT4+ ring encircles predominantly (>90,%) the TTF unit at equilibrium, and this equilibrium is relatively temperature independent. In the third rotaxane (RBPTTF4+), the TTF unit is replaced by a ,-extended analogue (a bispyrrolotetrathiafulvalene (BPTTF) unit), and the CBPQT4+ ring encircles almost equally both recognition sites at equilibrium. This equilibrium exhibits strong temperature dependence. These thermodynamic differences were rationalized by reference to binding constants obtained by isothermal titration calorimetry for the complexation of model guests by the CBPQT4+ host in acetonitrile. For all bistable rotaxanes, oxidation of the TTF (BPTTF) unit is accompanied by movement of the CBPQT4+ ring to the DNP site. Reduction back to TTF0 (BPTTF0) is followed by relaxation to the equilibrium distribution of translational isomers. The relaxation kinetics are strongly environmentally dependent, yet consistent with a single electromechanical-switching mechanism in acetonitrile, polymer electrolyte gels, and MSTJs. The ground-state equilibrium properties of all three bistable [2]rotaxanes were reflective of molecular structure in all environments. These results provide direct evidence for the control by molecular structure of the electronic properties exhibited by the MSTJs. [source]