Kinetic model and mechanism of the acid dissociation of d-metal bis(dipyrrolylmethenates)

A kinetic model and a mechanism have been developed by quantum chemical simulation for the protolytic dissociation of dinuclear homoleptic bis(dipyrrolylmethenates) of d-metals (M) with the general formula [M₂L₂] and a double-helix structure. The reaction is described by a third-order equation that is first-order with respect to the complex and second-order with respect to the acid. The main contribution to the total dissociation rate is made by the rate-determining step, specifically, attack of the second acetic acid molecule on the nitrogen atom of one of the coordination sites of the helicate. The dinuclear helicates of 3,3′-bis(dipyrrolylmethenes) are more inert in an acidic medium than 2,3′- and 2,2′-bis(dipyrrolylmethenes).     

Molecular structure of bis(dipyrrolylmethanates) of d-metals according to the quantum chemical calculations by the PM6 method

Quantum chemical calculations of the molecular structure of bis(dipyrrolylmethanates) of cobalt(II), nickel(II), copper(II), zinc(II), cadmium(II), and mercury(II) of the composition [M₂L₂] are performed using the PM6 method within the Gaussian 09W program package. The lengths of M-N coordination bonds, the values of dihedral angles formed by N-M-N bonds, the distances l _M?M between the M?M atoms are optimized. It is noted that the regularities obtained from the analysis of the results of quantum chemical calculations of the molecular structure of [M₂L₂] helicates reliably reflect the main trends of changes in their physicochemical properties depending on the nature of a complexing agent and the features of the ligand structure.     

Reconstructive acoustic thermotomography of biological objects

An algebraic reconstructive tomography algorithm for mapping the internal temperature field in q section of a biological object is adapted for use in a multichannel scanning acoustic thermotomograph. For some types of thermodynamic temperature distribution, using the computer simulation method, the distributions of the acoustic brightness temperature are obtained allowing for the antenna system geometry and damping in the biological medium. Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 40, No. 6, pp. 752–760, June, 1997.     

Modeling the vibrational spectrum of 4,4′-diphenylmethane-<Emphasis Type="Italic">bis</Emphasis>(methyl)carbamate

We present results of ab initio calculations of the structure and vibrational IR spectrum for 4,4′-diphenylmethane-bis(methyl)carbamate (DPMC). Calculations were carried out in the HF/6-311G approximation with subsequent force-field scaling. The calculated characteristics of the vibrational spectrum of DPMC show satisfactory agreement with experimental values, which permits them to be used in spectral and structural analysis     

Dynamics and supramolecular organization of the 1D spin transition polymeric chain compound [Fe(NH2trz)3](NO3)2. Muon spin relaxation

The thermal spin transition that occurs in the polymeric chain compound [Fe(NH(2)trz)3](NO3)2 above room temperature has been investigated by zero-field muon spin relaxation (microSR) over the temperature range approximately 8-402 K. The depolarization curves are best described by a Lorentzian and a Gaussian line that represent fast and slow components, respectively. The spin transition is associated with a hysteresis loop of width DeltaT = 34 K (T1/2 upward arrow = 346 K and T1/2 downward arrow = 312 K) that has been delineated by the temperature variation of the initial asymmetry parameter, in good agreement with previously published magnetic measurements. Zero-field and applied field (20-2000 Oe) microSR measurements show the presence of diamagnetic muon species and paramagnetic muonium radical species (A = 753 +/- 77 MHz) over the entire temperature range. Fast dynamics have been revealed in the high-spin state of [Fe(NH(2)trz)3](NO3)2 with the presence of a Gaussian relaxation mode that is mostly due to the dipolar interaction with static nuclear moments. This situation, where the muonium radicals are totally decoupled and not able to sense paramagnetic fluctuations, implies that the high-spin dynamics fall outside the muon time scale. Insights to the origin of the cooperative effects associated with the spin transition of [Fe(NH(2)trz)3](NO3)2 through muon implantation are presented.     

Superparamagnetic gamma-Fe(2)O(3) nanoparticles with tailored functionality for protein separation

Polymer coated superparamagnetic gamma-Fe(2)O(3) nanoparticles were derivatized with a synthetic double-stranded RNA [poly(IC)], a known allosteric activator of the latent (2-5)A synthetase, to separate a single 35 kDa protein from a crude extract which cross reacted with antibodies raised against the sponge enzyme.