Search results for "Dimension"
showing 10 items of 2766 documents
1H NMR studies of paramagnetic ferricytochrome c-551 from Pseudomonas aeruginosa at high pH: The role of histidine 16 in the spin transition
2005
Abstract Cytochrome c-551 from the mesophile Pseudomonas aeruginosa is an electronic transfer protein that contains 82 amino-acid residues and a c-type heme as the prosthetic group with low spin Fe(II) in the reduced form and low spin Fe(III) in the oxidized form of cytochrome c-551. We have studied the electronic properties of ferricytochrome c-551 from P. aeruginosa at high pH (9–11.4) by means of paramagnetic 1H NMR spectra and the T1 and T2 values of isotropically shifted proton resonances. We have also analyzed the temperature dependence of the hyperfine-shifts. Resonance assignment of some signals was based on 2D saturation transfer experiments, EXSY. These results indicate the existe…
New Triterpenoid and Ergostane Glycosides from the Leaves of Hydrocotyle umbellata L.
2011
Two new triterpenoid glycosides, together with two new ergostane glycosides, umbellatosides A–D (1–4, resp.), have been isolated from the leaves of Hydrocotyle umbellata L. Their structures were established by 2D-NMR spectroscopic techniques (1H,1H-COSY, TOCSY, NOESY, HSQC, and HMBC) and mass spectrometry as 3β,22β-dihydroxy-3-O-[α-L-rhamnopyranosyl-(12)-β-D-glucuronopyranosyl]olean-12-en-28-oic acid 28-O-β-D-glucopyranosyl ester (1), 3-O-[α-L-rhamnopyranosyl-(12)-β-D-glucuronopyranosyl]oleanolic acid 28-O-β-D-glucopyranosyl ester (2), (3β,11α,26)-ergosta-5,24(28)-diene-3,11,26-triol 3-O-(β-D-glucopyranosyl)-11-O-(α-L-rhamnopyranosyl)-26-O-β-D-glucopyranoside (3), and (3β,11α,21,26)-ergosta…
Sequence of a new tRNALeu(U∗AA) from brewer's yeast
1991
The nucleotide sequence of a new tRNA(Leu)(anticodon U*AA) from Saccharomyces cerevisiae which could recognize exclusively the UUA codon has been determined. Its primary structure is: pGGAGGGUUGm2GCac4CGAGDGmGDCDAAGGCm2(2)GGCAGACmUU*AAm1GA++ + psi CUGUUGGACGGUUGUCCGm5CGCGAGT psi CGm1A(orA)ACCUCGCAUCCUUCACCA. This tRNA has a large extraloop and contains 15 modified nucleotides. So far it is the third isoacceptor tRNA for leucine in yeast. It has 61% homology with tRNA(Leu)(anticodon m5CAA) and 63% homology with tRNA(Leu)(anticodon UAG), the two other known yeast tRNAs(Leu).
A new oleanane glycoside from the roots ofAstragalus caprinus
2006
A novel oleanane-type triterpene saponin (1) together with two known molecules, soyasapogenol B and astragaloside VIII were isolated from the roots of Astragalus caprinus. Their structural elucidation was performed mainly by 2D NMR techniques (COSY, TOCSY, NOESY, HSQC, HMBC) and mass spectrometry. Compound 1 was determined as 3-O-[alpha-L-rhamnopyranosyl-(1 --> 2)-beta-D-glucuronopyranosyl]-22-O-beta-D-apiofuranosyl-soyasapogenol B.
Solvatochromy and electro-optical study of new fluorine-containing chromophores
1998
technology requires tailored functional materials which fulfill the demands for optimal operation parameters, reliability andprocessability. Organic chromophores and polymers which contain covalently bound chromophores are promising materialclasses which can satisfy a broad spectrum of demands on functional materials for photonics, and they are, therefore,favorites for the development of new photonic devices. However, it is almost impossible to satisfy all physico-chemical andtechnological requirements simultaneously with a polymer consisting of only one type of functional unit. The developmentof a series of different building blocks which allow to cover the whole range of physico-chemical …
Acylated triterpene saponins from the roots of Securidaca longepedunculata.
2009
Abstract Four triterpene saponins , 3- O -β- d -glucopyranosylpresenegenin 28- O -β- d -apiofuranosyl-(1 → 3)-β- d -xylopyranosyl-(1 → 4)-[β- d -apiofuranosyl-(1 → 3)]-α- l -rhamnopyranosyl-(1 → 2)-{4- O -[( E )-3,4,5-trimethoxycinnamoyl]}-β- d -fucopyranosyl ester, 3- O -β- d -glucopyranosylpresenegenin 28- O -β- d -apiofuranosyl-(1 → 3)-β- d -xylopyranosyl-(1 → 4)-[β- d -apiofuranosyl-(1 → 3)]-α- l -rhamnopyranosyl-(1 → 2)-[(6- O -acetyl)-β- d -glucopyranosyl-(1 → 3)]-{4- O -[( E )-3,4,5-trimethoxycinnamoyl]}-β- d -fucopyranosyl ester, 3- O -β- d -glucopyranosylpresenegenin 28- O -β- d -apiofuranosyl-(1 → 3)-β- d -xylopyranosyl-(1 → 4)-[β- d -apiofuranosyl-(1 → 3)]-α- l -rhamnopyranosyl-(…
1,4-Bis(arylthio)but-2-enes as Assembling Ligands for (Cu2X2)n (X = I, Br; n = 1, 2) Coordination Polymers: Aryl Substitution, Olefin Configuration, …
2016
CuI reacts with E-PhS(CH2CH═CHCH2)SPh, L1, to afford the coordination polymer (CP) [Cu2I2{μ-E-PhS(CH2CH═CHCH2)SPh}2]n (1a). The unprecedented square-grid network of 1 is built upon alternating two-dimensional (2D) layers with an ABAB sequence and contains rhomboid Cu2(μ2-I)2 clusters as secondary building units (SBUs). Notably, layer A, interconnected by bridging L1 ligands, contains exclusively dinuclear units with short Cu···Cu separations [2.6485(7) A; 115 K]. In contrast, layer B exhibits Cu···Cu distances of 2.8133(8) A. The same network is observed when CuBr reacts with L1. In the 2D network of [Cu2Br2{μ-E-PhS(CH2CH═CHCH2)SPh}2]n (1b), isotype to 1a, one square-grid-type layer contain…
Reaction kinetics in dense two-dimensional polymer solutions : an excimer probe study
1994
We report measurements of the time dependent reaction rate of excimer formation in two-dimensional solutions of a polymerized amphiphile with partially pyrene-labelled chains in monolayers at the air-water-interface. We find a time dependent reaction rate for excimer formation obeying a power law r(t) ∞ t -β . The exponent β has a value of 0.22±0.12. This value is consistent with β=1/4, as has been predicted for bimolecular diffusion-controlled reactions in two-dimensional polymer melts by de Gennes. The measurements demonstrate the usefulness of the excimer technique to explore polymer dynamics
Fractal calibration in size-exclusion chromatography
2003
Abstract The elution behaviour of different polymer–solvent systems in three types of organic columns for SEC has been compared and interpreted. The experimental data show that the classical universal calibration is not accomplished. Deviations from a unique curve are observed due to the binary and ternary interactions between the components of the system (solvent, polymer and gel) which results on secondary mechanisms accompanying the main pure or “ideal” SEC separation mechanism. Both, enthalpic and entropic effects are interpreted in terms of the swelling and crosslinking degrees of the gel packings, and are also related with the fractal characteristics of their surfaces, such as the fra…
Mean square radius of gyration and hydrodynamic radius of jointed star (dumbbell) and H-comb polymers
1996
Equations for the mean square radius of gyration and the hydrodynamic radius for jointed stars (dumbbells) and H-combs are derived, based on random flight statistics for each subchain. Comparision with literature data on computer simulations and experimental data for H-combs show good agreement for the g-value of the mean square radius of gyration even in good solvents. This suggests that for the mean square radius of gyration the relative dimension of a H-comb relative to the linear molecule of the same degree of polymerization is not altered significantly by long range interactions, as in the case of star polymers. For the hydrodynamic radius the situation is different. Fair agreement is …