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Biomedical subjects

Marat Moustiakimov

Publications and source records attributed to Marat Moustiakimov.

4 recordsLinked to original sources
PubMed2005

The partial structure with errors: a probabilistic treatment.

The method of the joint probability distribution functions has been applied to the case in which observed (with errors) and calculated structure factors are available, the latter referred to a part of the structure with finite errors in the coordinates, the thermal parameters and the scattering factors. Results obtained by other authors are confirmed and generalized. A new relationship is found to estimate the parameter sigmaA, affecting the reliability of the estimates of cos(varphi-varphip). Some practical applications are described.

Journal Article↗
PubMed2005

First example of low-valence ion substitution in Ln5O(OPri)13: mixed-valence europium oxoalkoxide [EuIII4EuIIO(OPri)12(HOPri)]HOPri.

The novel mixed-valence alkoxide [Eu3+(4)Eu2+O(OPri)12(HOPri)]HOPri (1) has been prepared and structurally and spectroscopically characterized. The three synthesis routes (i) metathesis of 4EuCl3, EuI2, and 14KOPri combined with hydrolysis with 1H2O, (ii) oxidation of 5[Eu4(OPri)10(HOPri)3]2HOPri with 1.5O2, and (iii) reduction of Eu5O(OPri)13 with 0.8[Eu4(OPri)10(HOPri)3]2HOPri all yielded pure 1, whereas (iv) reduction of Eu5O(OPri)13 with 0.36-0.5 mol of europium metal produced impure 1. The compound, having the average Eu oxidation number +2.8, is very sensitive toward further oxidation to Eu5O(OPri)13 and is part of a redox series of europium 2-propoxides with average oxidation states +2.5, +2.8, and +3. The square pyramidal molecular structure, containing an oxo-oxygen atom in the basal plane, is similar to that of the well-known Ln5O(OPri)13; the main difference is the substitution of an Eu3+(-)OPri pair for an Eu2+(-)HOPri pair in the basal plane. Fourier transform infrared (FT-IR) and UV-visible spectroscopy showed that the solid-state structure was retained on dissolution in hexane and toluene-HOPri. The compound was further characterized by differential scanning calorimetry and solubility studies.

Journal Article↗
PubMed2004

Locating heavy atoms by integrating direct methods and SIR techniques.

Direct methods have been applied to the SIR (single isomorphous replacement) case to estimate structure-factor moduli from diffraction magnitudes. The joint probability distribution function P(E(H),E(p),E(d)) has been calculated by explicitly considering, as an additional primitive random variable, the cumulative error arising from measurements and from lack of isomorphism. The specific feature of the approach is that it provides estimated values of |E(H)| which depend on the experimental diffraction data as well as on errors. Some test structures have been used to check the efficiency of the new estimates. Patterson techniques, using the estimated |E(H)|(2) values as coefficients, as well as a tangent procedure, have been implemented into a computer program to locate the heavy atoms automatically. All the experimental tests show that the new approach provides results highly competitive with the traditional |E(H)|(2) estimates.

Journal Article↗