Improving sensitivity of XANES structural fit to the bridged metal-metal coordination.

Hard X-ray absorption spectroscopy is a valuable in situ probe for non-destructive diagnostics of metal sites. The low-energy interval of a spectrum (XANES) contains information about the metal oxidation state, ligand type, symmetry and distances in the first coordination shell but shows almost no dependency on the bridged metal-metal bond length. The higher-energy interval (EXAFS), on the contrary, is more sensitive to the coordination numbers and can decouple the contribution from distances in different coordination shells. Supervised machine-learning methods can combine information from different intervals of a spectrum; however, computational approaches for the near-edge region of the spectrum and higher energies are different. This work aims to keep all benefits of XANES and extend its sensitivity towards the interatomic distances in the first and second coordination shells. Using a binuclear bridged copper complex as a case study and cross-validation analysis as a quantitative tool it is shown that the first 170 eV above the edge are already sufficient to balance the contributions of Cu-O/N scattering and Cu-Cu scattering. As a more general outcome this work highlights the trivial but often overlooked importance of using `longer' energy intervals of XANES for structural refinement and machine-learning predictions. The first 200 eV above the absorption edge still do not require parametrization of Debye-Waller damping and can be calculated within full multiple scattering or finite difference approximations with only moderately increased computational costs.

[Changes in protein spectrum of cattle blood serum with lympholeukosis].

The protein spectrum of blood serum was studied in healthy cows and those suffering from leucosis. The total amount of protein at the early stages of the disease is established to be unchanged. But with lympholeucosis the content of the globulin fraction increases with a simultaneous decrease in the amount of albumins within 20%. The globulin fraction content rises due to immunoglobulin G. The albumin: globulins coefficient is 0.56 for animals with leucosis and 0.84 for the healthy ones. A problem on possible qualitative changes in this fraction similar to those occurring with other forms of malignant growth is under discussion.

[Structural peculiarities of protein typical of G-myelomas]. / Strukturni osoblivosti bilka, kharakternoho dlia G-mielom

G-myeloma protein is shown to differ by its conformation from the donor immunoglobulin G. It is characterized by a more polar surrounding of the molecule tyrosine and tryptophane residua. Under the effect of urea the changes are less considerable.