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Similar Stability (similar + stability)
Selected AbstractsMechanism of Selective and Unselective Enclathration by a Host Compound Possessing Open, Flexible Host FrameworksEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 13 2003Kazunori Nakano Abstract Molecular recognition of o -, m -, and p -xylenes (oX, mX, and pX) through enclathration of cholic acid (CA) is described. All of the xylenes give lattice inclusion crystals with CA, and crystallographic studies reveal that they are included in different open host frameworks. In particular, oX has two polymorphs, depending on the recrystallization temperatures. Competitive recrystallization from mixtures of xylenes resulted in selective enclathrations and the formation of racemic mixed crystals. In the presence of an equimolar amount of oX, CA selectively includes mX or pX in the host frameworks, which are identical to those obtained from the pure mX or pX, respectively. The low affinity of oX is explained in terms of a lower stability of CA·oX than of the other two complexes, as judged from the low PCcavity, the volume ratio of the guest compound to the host cavity. Meanwhile, mixtures of mX and pX yield inclusion crystals that accommodate both of the guests. These have the same open host framework as obtained from pure mX, and the guest components are disordered statically in the host cavity. The ratios of the xylene mixtures in the single crystals are similar to those in the original recrystallization mixtures, and also in the bulk crystals, indicating that CA forms mixed crystals of mX and pX. This non-selectivity is attributed to the similar stabilities of CA·mX and CA·pX, according to the moderate PCcavity. The inclusion behavior of CA from mixtures of xylenes is quite similar to chiral recognition by diastereomer-salt methods. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Electronic Interactions in Ferrocene- and Ruthenocene-Functionalized Tetraazamacrcocyclic Ligand Complexes of FeII/III, CoII, NiII, CuII and ZnIIEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 2 2005Peter Comba Abstract The syntheses of ferrocene- and ruthenocene-functionalized tetraazamacrocyclic ligands and their corresponding transition metal complexes are described. Reaction of N,N, -bis(2-aminoethyl)-1,3-propanediamine (2,3,2-tet) with 1,1,-diformylferrocene and 1,1,-diformylruthenocene produces the ligands fcmac and rcmac in 81,85% yield. Examination of their CuII, NiII, CoII, ZnII and FeII/III complexes by IR, UV/Vis, EPR and Mössbauer spectroscopy as well as by electrochemical studies suggests electronic communication between the two metal centers of each complex. The molecular structure of [CuII(fcmac)(FBF3)]BF4, determined by X-ray structure analysis, is reported and shows that the distance between the two metals is 4.54 Å. Stability constants, determined by potentiometric titration, indicate that the copper(II) complexes are of similar stability as those with unfunctionalized tetraazamacrocyclic ligands (e.g. cyclam = 1,4,8,11-tetraazacyclotetradecane); stability constants of cobalt(II) complexes are about 2 log units smaller, those of nickel(II) and zinc(II) complexes are reduced by more than 10 log units. This selectivity is discussed on the basis of the structural studies. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Assembly of cytochrome f into the cytochrome bf complex in isolated pea chloroplastsFEBS JOURNAL, Issue 3 2001Ruth M. Mould Structural features of cytochrome f necessary for assembly into the cytochrome bf complex were examined in isolated pea chloroplasts following import of 35S-labelled chimeric precursor proteins, consisting of the presequence of the small subunit of Rubisco fused to the turnip cytochrome f precursor. Assembly was detected by nondenaturing gel electrophoresis of dodecyl maltoside-solubilized thylakoid membranes. A cytochrome f polypeptide unable to bind haem because of mutagenesis of Cys21 and Cys24 to alanine residues was assembled into the complex and had similar stability to the wild-type polypeptide. This indicates that covalent haem binding to cytochrome f is not necessary for assembly of the protein into the cytochrome bf complex. A truncated protein lacking the C-terminal 33 amino acid residues, including the transmembrane span and the stroma-exposed region, was translocated across the thylakoid membrane, had a similar stability to wild-type cytochrome f but was not assembled into the complex. This indicates that the C-terminal region of cytochrome f is important for assembly into the complex. A mutant cytochrome f unable to bind haem and lacking the C-terminal region was also translocated across the thylakoid membrane but was extremely labile, indicating that, in the absence of the C-terminal membrane anchor, haem-less cytochrome f is recognized by a thylakoid proteolytic system. [source] Semi-Lagrangian advection scheme with controlled damping: An alternative to nonlinear horizontal diffusion in a numerical weather prediction modelTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 631 2008Filip Vá Abstract This paper proposes a nonlinear horizontal diffusion scheme for models using semi-Lagrangian formulations. The scheme is made flow dependent and not entirely linked to the model levels. As an extension, the implementation of the scheme to the model Aladin is given. The damping abilities of interpolation are used for the diffusion filtering. The aim is to provide a horizontal diffusion scheme of similar stability and computational efficiency as the existing linear spectral diffusion scheme in Aladin. Preserving such qualities, the new scheme brings beneficial new skills to the model. The differences between the performances of the two diffusion schemes are examined and discussed. Finally, some interesting case-studies simulated with both horizontal diffusion schemes are presented. Copyright © 2008 Royal Meteorological Society [source] | ||||||||||