Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:Q86TM3 (cage)
 29,987 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have determined intersite distances from Cys374 of actin to Cys707 (SH1) and Cys697 (SH2) of myosin subfragment 1 (S1) in actosubfragment 1 (A.S1) by fluorescence resonance energy transfer for rigor complex A.S1 and complexes containing bound ADP and ADP plus orthovanadate (Vi), A.S1.ADP, and A.S1.ADP.Vi. A single energy acceptor (4-dimethylaminophenylazophenyl-4'-maleimide, DABMI) was attached to Cys374, and two different energy donors [(5-(iodoacetamideothyl)aminonaphthalene-1-sulfonic acid (IAEDANS) and 2-(4'-maleimidylanilino)naphthalene-6-sulfonic acid (MIANS)] were each attached to SH1 and SH2 for the distance determination. The two sites SH1 and SH2 of S1 were approximately equidistant (ca. 45 A) from actin Cys374 in rigor A.S1 when MIANS was the energy donor attached to the two thiols. The Cys374-SH1 distance decreased by 7-8 A in the presence of ADP plus Vi, but the distance Cys374-SH2 was essentially unaltered under identical conditions. Slightly different but similar distance results were obtained with AEDANS as energy donor. If the structure of actin monomer in A.S1 is assumed to be rigid [Miki, M. (1991) Biochemistry 30, 10878-10884], the present results indicate that MgADP plus Vi induced a movement of SH1 toward the actin site and that SH2 was insensitive to saturation of the active site pocket of S1 and relatively immobile. These results suggest that during the steady-state hydrolysis of ATP or in the weak-binding state of actomyosin, the short helical segment of S1 heavy chain containing SH1 moves closer to the COOH-terminal end of actin, while the adjacent helical segment containing SH2 remains stationary. The emission spectrum of MIANS attached to SH2 experienced a large red spectral shift (6-10 nm) in the presence of MgADP, MgADP + Vi, MgADP + beryllium fluoride, and ATP. A crude model of S1 based on the C alpha coordinates suggests that SH2 is located in a hydrophobic cage surrounded by three hydrophobic residues. Reorientation of one of these side chains could expose SH2 to the solvent. The observed red spectral shift of MIANS attached to SH2 could be explained by such a nucleotide-induced exposure, and this explanation would be consistent with the interpretation that SH2 is stationary.
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PMID:Internal movement in myosin subfragment 1 detected by fluorescence resonance energy transfer. 775 79

The FeCl3-catalysed arylation of C60F18 gives tri-substituted compounds C60F15Ar3, where Ar=phenyl, 4-tolyl, 4-methoxyphenyl, 4-phenoxyphenyl, 4-chlorophenyl, 3,4-dichlorophenyl, 2-biphylenyl and 2-fluorenyl, together with some bis- and mono-substituted product. Bis-substitution was achieved with biphenylene and fluoranthene, and mono-substitution with biphenylene (2-position), pyrene (1-position), and naphthalene (1- and 2-positions); the tris-phenyl and tris-biphenylene derivatives are fluorescent. The 2-naphthyl substituent freely rotates at 328 K, whereas rotation of the 1-naphthyl substituent is prevented by interaction of the peri-hydrogen atom with fluorine. The 1-naphthyl derivative eliminates a molecule of HF during EI mass spectrometry, whilst the 2-naphthyl derivative eliminates HF and all fluorenes to give a naphthaleno[60]fullerene. The reaction rate is relatively unaffected by electron supply in the aryl rings, but no product was obtained with benzotrifluoride which defines the lower reactivity limit. The low discrimination between aromatics makes it possible to isolate derivatives having different aryl groups attached to the cage. Reactions occur mainly when the reagent solutions (or solutions in 1,2-dichlorobenzene) are evaporated to dryness. In most FeCl3-catalysed reactions, unreacted C60F18 was recovered, more if the less effective SnCl4 was used as a catalyst; use of AlCl3 resulted in polyarylation and degradation of the C60F18. The structure of C60F17(1-biphenylyl) was confirmed by single-crystal X-ray analysis. Reaction of C60F18 with perylene/FeCl3/o-dichlorobenzene gave red fluorescent "tagliatelli"-like threads (up to 1 cm long) of self-assembled pi-stacked tetrachloroperylene arising from chlorination by FeCl3.
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PMID:Electrophilic aromatic substitution by the fluorofullerene C60F18. 1537 31

Of current interest in our laboratory is the nature of photoinduced processes in the cavities of zeolites completely submerged in polar solvents, or polar-solvated zeolites (PSZ). The present study addresses the nature of electron trapping in PSZ with emphasis on the zeolites NaX and NaY. Free electrons were generated by two-photon, pulsed-laser excitation of either pyrene or naphthalene included in zeolite cavities. Trapped electrons were monitored by diffuse transmittance, transient absorption spectroscopy at visible wavelengths. In anhydrous alcohols, electron trapping by Na(4)(4+) ion clusters was observed in both NaX and NaY. The resulting trapped electrons decayed over the course of tens of milliseconds. No evidence for alcohol-solvated electrons was found. More varied results were observed in solvents containing water. In NaX submerged in CH(3)OH containing 5% or higher water, species having microsecond lifetimes characteristic of solvated electrons were observed. By contrast, a 2 h exposure of NaY to 95/5 CH(3)OH/H(2)O had no effect on electron trapping relative to anhydrous CH(3)OH. The difference between NaX and NaY was explained by how fast water migrates into the sodalite cage. Prolonged exposure to water at room temperature or exposure to water at elevated temperatures was necessary to place water in the sodalite cages of NaY and deactivate Na(4)(4+) as an electron trap. Additional studies in NaY revealed that solvent clusters eventually become lower energy traps than Na(4)(4+) as the water content in methanol increases. In acetonitrile-water mixtures, electron trapping by Na(4)(4+) was eliminated and no equivalent species characteristic of solvated electrons in methanol-water mixtures was observed. This result was explained by the formation of low energy solvated electrons which cannot be observed in the visible region of the spectrum. Measurements of the rate of O(2) quenching in anhydrous solvents revealed rate constants for the quenching of ion cluster trapped electrons that were 2-4 times higher than that for pyrene triplets. In NaX, the rate constant in methanol was 10(4) times smaller than that in cyclohexane, showing greater inhibition of O(2) reactivity in the medium of PSZ. The results of this study point out the conditions under which Na(4)(4+) is active as an electron trap in PSZ and that water must be present in the sodalite cage to produce solvated electrons in the supercage.
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PMID:Electron trapping in polar-solvated zeolites. 1685 43

Incorporation of ligands containing substituted naphthalene cores into coordination cages results in extensive aromatic pi-stacking between ligands; this results in a red-shifted 'excimer-like' luminescence component from the naphthyl groups compared to the free ligands, which is diagnostic of, and can be used to monitor, cage assembly.
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PMID:Red-shifted luminescence from naphthalene-containing ligands due to pi-stacking in self-assembled coordination cages. 1703 1

This report provides a summary of deliberations conducted under the charge for members of Module B participating in the Naphthalene State-of-the-Science Symposium (NS(3)), Monterey, CA, October 9-12, 2006. The panel's charge was to derive consensus estimates of human exposure to naphthalene under various conditions, cancer incidence plausibly associated with these exposures, and identify quintessential research that could significantly reduce or eliminate material uncertainties to inform human cancer risk assessment. Relying in large part on a commissioned paper [Price, P.S., Jayjock, M.A., 2008. Available data on naphthalene exposures: strengths and limitations, in this issue], exposure levels were estimated for background (0.0001-0.003 microg/m(3)), ambient air (0.001-1.0 microg/m(3)), vehicles (0.003-3.0 microg/m(3)), residences (0.1-10 microg/m(3)), mothball use (on-label: 1-100 microg/m(3); off-label: 10-100 microg/m(3)), and occupational (low: 3-100 microg/m(3); high: 30-1,000 microg/m(3)). There have been few published reports of human cancer associated with naphthalene exposure. Several research projects are suggested that could reduce uncertainty in our understanding of human exposure. Using best scientific judgment, it is reasonably certain that the largest non-occupational exposures to naphthalene are indoor/residential exposures, particularly in households that use naphthalene-based products such as mothballs. However, even the highest of these exposures is likely to fall one or more orders of magnitude below moderate or high-level occupational exposure levels experienced by the few known cohorts exposed occupationally to naphthalene alone or as part of chemical mixtures such as jet fuel.
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PMID:Exposure, epidemiology and human cancer incidence of naphthalene. 1842 20

Two new bis-bidentate bridging ligands have been prepared, L (naph) and L (anth), which contain two chelating pyrazolyl-pyridine units connected to an aromatic spacer (naphthalene-1,5-diyl and anthracene-9,10-diyl respectively) via methylene connectors. Each of these reacts with transition metal dications having a preference for octahedral coordination geometry to afford {M 8L 12} (16+) cages (for L (anth), M = Cu, Zn; for L (naph), M = Co, Ni, Cd) which have an approximately cubic arrangement of metal ions with a bridging ligand spanning each of the twelve edges, and a large central cavity containing a mixture of anions and/or solvent molecules. The cages based on L (anth) have two cyclic helical {M 4L 4} faces, of opposite chirality, connected by four additional L (anth) ligands as "pillars"; all metal centers have a meridional tris-chelate configuration. In contrast the cages based on L (naph) have (noncrystallographic) S 6 symmetry, with a diagonally opposite pair of corners having a facial tris-chelate configuration with the other six being meridional. An additional significant difference between the two types of structure is that the cubes containing L (anth) do not show significant interligand aromatic stacking interactions. However, in the cages based on L (naph), there are six five-membered stacks of aromatic ligand fragments around the periphery, each based on an alternating array of electron-rich (naphthyl) and electron-deficient (pyrazolyl-pyridine, coordinated to M (2+)) aromatic units. A consequence of this is that the cages {M 8(L (naph)) 12} (16+) retain their structural integrity in polar solvents, in contrast to the cages {M 8(L (anth)) 12} (16+) which dissociate in polar solvents. Consequently, the cages {M 8(L (naph)) 12} (16+) give NMR spectra in agreement with the symmetry observed in the solid state, and their fluorescence spectra (for M = Cd) display (in addition to the normal naphthalene-based pi-pi* fluorescence) a lower-energy exciplex-like emission feature associated with a naphthyl --> pyrazolyl-pyridine charge-transfer excited state arising from the pi-stacking between ligands around the cage periphery.
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PMID:Octanuclear cubic coordination cages. 1885 58

A theoretical investigation of stabilities and electronic properties of novel transition bimetallic atoms (BTMAs) encapsulated naphthalene-like Si(20) prismatic cage is being reported for the first time. The symmetry and electronic state of naphthalene-like TMA(2)@Si(20) is significantly affected by the type of encapsulated TMA from 3d, 4d to 5d series. Because of high binding energies, relative high HOMO-LUMO gaps, large charge-reverse transferring from naphthalene-like Si(20) cage to BTMAs at the centre of the 5d series, the most stable species of TMA(2)@Si(20) cage is favorable to form new 1D-TMA(n)@Si(m) nanotube, which is based on array of the novel naphthalene-like structure.
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PMID:Novel bi-transition metallic encapsulated naphthalene-like Si20 prismatic cage: a DFT investigation. 1894 31

Treatment of arachno-4-Me(2)S-B(9)H(13) (1) with ethynylferrocene, FcC[triple bond]CH (Fc = ferrocenyl), in boiling benzene afforded an inseparable 2 : 1 mixture of 6-Fc-nido-5,6-C(2)B(8)H(11) (2a) and 5-Fc-nido-5,6-C(2)B(8)H(11) (2b) in a 10% yield. However, compound 2b was converted quantitatively to the pure, violet 2a by the action of proton sponge (PS), followed by acidification. The structure of 2a was determined by X-ray diffraction analysis. Heating of 2a at 400 degrees C led to the dehydrogenation and isolation of the orange 1-Fc-closo-1,10-C(2)B(8)H(9) (3) in almost quantitative yield, while treatment of 2a with t-BuNC and PS (proton sponge = 1,8-bis(dimethylamino)naphthalene) in CH(2)Cl(2) generated the neutral absolute tautomer 7-t-BuNH-8-Fc-7,8,9-C(3)B(8)H(10) (N4) (yield 50%), which could be converted quantitatively into the zwitterionic tautomer 7-t-BuNH(2)-8-Fc-7,8,9-C(3)B(8)H(9) (Z4) via dissolution in MeCN. Tautomers N4 and Z4 sharply differ in NMR properties and both gave rise to a pair of cage-isomeric closo ferratricarbollides, [1-Cp-2-Fc-12-t-BuNH-1,2,4,12-FeC(3)B(8)H(9)] (5a) (Cp = eta(5)-C(5)H(5)) (yield 48%) and [1-Cp-2-Fc-10-t-BuNH-1,2,4,10-FeC(3)B(8)H(9)] (5b) (yield 32%), upon heating with [CpFe(CO)(2)](2) in mesitylene at reflux. Electrochemical studies revealed that the compounds display one (compounds 2a and 3) or two (compounds 5a and 5b) well-defined, reversible one-electron Fe(II)/Fe(III) redox changes.
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PMID:Synthesis and electrochemistry of some ferrocenyl substituted dicarba- and tricarbaborane compounds. 2014 25

13-vertex indenyl cobaltacarboranes with 4,1,6-, 4,1,10- and 4,1,2-CoC(2)B(10) architectures have been synthesised by reduction of the corresponding closo carborane and metallation with an {(eta-C(9)H(7))Co} fragment. Variants of the 4,1,6-isomer were prepared with no, one and two methyl groups on cage C atoms, whilst 4,1,2-species were obtained both with two methyl groups and a trimethylene tether on the cage C atoms. Thermolysis of the 4,1,6-isomers yielded the corresponding 4,1,8-isomers, which in turn were converted to 4,1,12-isomers by thermolysis at higher temperatures. Alternatively relatively mild heating of the 4,1,10-isomer led to the 4,1,12-isomer directly. Products were characterised by mass spectrometry, (1)H and (11)B NMR spectroscopies and, in most cases, elemental analysis, and nine compounds were studied crystallographically. The 4,1,6-, 4,1,8-, 4,1,10- and 4,1,12- species have docosahedral cages whilst the 4,1,2-species are henicosahedral. In the structural studies attention focused on the orientation of the indenyl ligand with respect to the carborane ligand since this affords experimental information on the metal-cage bonding through the structural indenyl effect. There is a general tendency for the indenyl ligand to adopt orientations in which the ring junction C atoms lie trans to cage B atoms. In cases where the orientation is not compromised by the presence of a non-H substituent on the face of the carborane there is generally good agreement between the experimental orientation and that computed by DFT calculations for the related naphthalene ferracarboranes (eta-C(10)H(8))FeC(2)B(10)H(12). The presence of C-methyl substituents in the indenyl cobaltacarboranes tends to override this preference except in the case of 1,6-Me(2)-4-(eta-C(9)H(7))-4,1,6-closo-CoC(2)B(10)H(10) where the indenyl ligand instead is forced to incline away from the cage methyl groups. In DCM solution the 4,1,6-, 4,1,8-, 4,1,10- and 4,1,12- isomers of (eta-C(9)H(7))CoC(2)B(10)H(12) exhibit two, stepwise, 1-electron reductions assigned to Co(III)/Co(II)/Co(I) couples at less negative potentials than those of the corresponding Cp compounds. Moreover these reductions are easier for those isomers (4,1,6- and 4,1,10-) in which there are two cage C atoms in the carborane face to which the metal atom is bound. By spectroelectrochemical and EPR measurements it is concluded that the reductions of these indenyl cobaltacarboranes are largely metal-based.
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PMID:Supraicosahedral indenyl cobaltacarboranes. 2044 Apr 41

A self-assembled molecular flask with a nanometer-sized restricted cavity offers a new reaction environment that is quite different from the bulk solution. The self-assembled cage accommodates a pair of hydrophobic molecules to perform unusual Diels-Alder reactions and [2+2] photoadditions of otherwise unreactive aromatic molecules. In this cage, for example, the Diels-Alder reaction of naphthalene proceeds smoothly under mild conditions, and aceanthrylene shows reactivity for both [2+2] and [2+4] cycloadditions via the identical ternary host-guest complex. The observed greatly enhanced reactivity stems from the increased local concentration and pre-organization of the substrate pair within the cage, which reduces the entropic cost and switches the reaction profile from a bimolecular to a pseudo-intramolecular reaction pathway. The reinforced orientation and arrangement of substrate pairs specify regio- and stereo-selectivities of the subsequent reactions in the cavity. Chiral auxiliaries outside the cage create the inner chiral environment and induce asymmetric reactions inside the cage (up to 50% ee).
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PMID:Pericyclic reactions in an aqueous molecular flask. 2085 76


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