Solution structural studies

The reported stability constants for Reaction (V.70) are listed in Table V-8. 

Method Medium r( C) logi K, reported accepted Reference 

The value given by Arhland and Rosengren [56AHR/ROS] determined at 

The formation of higher complexes (NiF , 1) is not reported in the literature, not even in presence of more than a thousand-fold excess of fluoride over Ni(II) [71 BON]. 

From the above A //° value, the following selected standard enthalpy of formation can be derived for NiF  

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Dattagupta N, Crothers DM (1981) Solution structural studies of the Ag(I)-DNA complex. Nucl Acids Res 9 2971-2985... 

The crystal structure of native hen ovalbumin shows an intact reactive center loop in the form of an exposed a-helix of three turns that protrudes from the main body of the molecule on two peptide stalks. The ovalbumin structure includes four crystallographically independent ovalbumin molecules and the position of the helical reactive center loop relative to the protein core differs by 2-3 A between molecules. Although this shift is probably due to the different environments of the helices in the crystal lattice, it suggested that the reactive center loop is flexible in solution. Structural studies of serpins in various conformations have shown how the exceptional mobility of the serpin reactive center loop and their unique flexibility is essential for function. In contrary to inhibitory serpins, ovalbumin does not show evidence for a large conformational change following cleavage at its putative reactive center and appears to have lost the extreme mobility which is characteristic for its inhibitory ancestors. 

The anion [(CpTiS)2(/x-S)]22 obtained by monodeprotonation of Cp2Ti(SH)2 with LiBuc in THF reacts with complexes [M(/i-Cl)(diolefin)]2 (M = Rh, Ir) to give the tetranuclear derivatives CpTi(/i3-S)3M3(diolefin)3. Carbonylation reactions and further treatment with P-donor ligands afford Rh- and Ir-substituted complexes CpTi(/i3-S)3M3Lx (Scheme 712). Spectrocopic data indicate fluxional behaviour in solution. Structural studies and... 

In the work presented here, these processes have been studied primarily by calorimetry. Planned measurements of partial specific heat and partial molal volume will give additional thermodynamic data on the structure of micellar systems. Heat capacity measurements will allow "simple" extrapolation of measured enthalpy terms to higher temperatures. In addition, a direct measure of the effect of temperature variation is of interest for solution structure studies. Partial molal volume measurements give information on the packing of surfactant monomers and micelles within the water structure. The effect of cosurfactants on the partial molal volume will be of particular interest. 

Denmark SE, Su X (1999) Solid state and solution structural studies of chiral phosphoramide-tin complexes relevant to lewis base catalyzed aldol addition reactions. Tetrahedron 55 8727-8738... 

As was the case with the solution structural studies on the mammalian proteins [154,219-222], there were no dipolar crmstraints between the two metal domains to permit their respective orientation. This was a limitation when working with MTs isolated from natural source at the time, which today could be overcome by the expression of recombinant MT with isotopic labeling and the use of residual dipolar coupling methods [227]. Another advancement in the 3D structural studies on this protein has arisen from the increased sensitivity of newer, higher field NMR instruments. NMR studies on MT at 800 MHz now provide a sufficient number of H- H NOE dipolar constraints to permit the calculation of the tertiary fold of the protein backbone in MT without the need for Cd substitution and the... 

Although experimental studies of DNA and RNA structure have revealed the significant structural diversity of oligonucleotides, there are limitations to these approaches. X-ray crystallographic structures are limited to relatively small DNA duplexes, and the crystal lattice can impact the three-dimensional conformation [4]. NMR-based structural studies allow for the determination of structures in solution however, the limited amount of nuclear overhauser effect (NOE) data between nonadjacent stacked basepairs makes the determination of the overall structure of DNA difficult [5]. In addition, nanotechnology-based experiments, such as the use of optical tweezers and atomic force microscopy [6], have revealed that the forces required to distort DNA are relatively small, consistent with the structural heterogeneity observed in both DNA and RNA. 

The serine proteinases have been very extensively studied, both by kinetic methods in solution and by x-ray structural studies to high resolution. From all these studies the following reaction mechanism has emerged. 

The alkyl-bridged structures can also be described as comer-protonated cyclopropanes, since if the bridging C—C bonds are considered to be fully formed, there is an extra proton on the bridging carbon. In another possible type of structure, called edge-protonated cyclopropanes, the carbon-carbon bonds are depicted as fully formed, with the extra proton associated with one of the bent bonds. MO calculations, structural studies under stable-ion conditions, and product and mechanistic studies of reactions in solution have all been applied to understanding the nature of the intermediates involved in carbocation rearrangements. 

A more detailed representation of the reaction requires more intimate knowledge of the enolate structure. Studies of ketone enolates in solution indicate that both tetrameric and dimeric clusters can exist Tetrahydrofliran, a solvent in which many synthetic reactions are performed, favors tetrameric structures for the lithium enolate of isobutyr-ophenone, for example. ... 

Hie solution structures of cyano-Gilman aiprates and lower-ordet cyanoaiprates have been studied by ctyoscopic meastirenients in THF [141]. Hie results of tliis study have in several cases sliown ways to obtain useful single crystals of several higher- and lowet-order cyanoaiprates and consequently to determine tlieir structures in tlie solid state. 11 appears tlial a number of tliese cyanoaiprales retain tlieir observed solid-slale sliuctute when dissolved in THF. 

No structural studies have been reported on these complexes, but detailed study of their vibrational spectra permits the assignments shown in Table 2.13. Like the rhodium analogues, iridium ammines are photoactive therefore, on excitation of ligand-field bands, solutions of [Ir(NH3)6]3+ or [Ir(NH3)5Cl]+ afford [Ir(NH3)5(H20)]3+. 

As has been shown by the X-ray diffraction method the parent metals (i.e. Pd or Ni), the a-phase, and /3-phase all have the same type of crystal lattice, namely face centered cubic of the NaCl type. However, the /9-phase exhibits a significant expansion of the lattice in comparison with the metal itself. Extensive X-ray structural studies of the Pd-H system have been carried out by Owen and Williams (14), and on the Ni-H system by Janko (8), Majchrzak (15), and Janko and Pielaszek (16). The relevant details arc to be found in the references cited. It should be emphasized here, however, that at moderate temperatures palladium and nickel hydrides have lattices of the NaCl type with parameters respectively 3.6% and 6% larger than those of the parent metals. Within the limits of the solid solution the metal lattice expands also with increased hydrogen concentration, but the lattice parameter does not depart significantly from that of the pure metal (for palladium at least up to about 100°C). 

Models for copper-protein interaction based on solution and crystal structure studies. R. Osterberg, Coord. Chem. Rev., 1974,12, 309-347 (130). 

Report 125 Structural Studies of Polymers by Solution NMR, H.N. Cheng, Hercules Incorporated. 

Several assumptions were made in using the broad MWD standard approach for calibration. With some justification a two parameter equation was used for calibration however the method did not correct or necessarily account for peak speading and viscosity effects. Also, a uniform chain structure was assumed whereas in reality the polymer may be a mixture of branched and linear chains. To accurately evaluate the MWD the polymer chain structure should be defined and hydrolysis effects must be totally eliminated. Work is currently underway in our laboratory to fractionate a low conversion polydlchlorophosphazene to obtain linear polymer standards. The standards will be used in polymer solution and structure studies and for SEC calibration. Finally, the universal calibration theory will be tested and then applied to estimate the extent of branching in other polydlchlorophosphazenes. 

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