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The X-ray standing-wave method was applied to study the elemental composition and molecular organization of ordered protein films of alkaline phosphatase exposed to different xenobiotics (drug compounds, lead). Binding of metal ions from triply distilled water to protein molecules has been experimentally observed. Definite differences in the arrangement of impurity metal ions in the films have been established. The considerable enhancement of protein-metal interactions is attributed to partial rearrangement of the protein native structure, induced by xenobiotics.

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The protective effect of the bisphosphonate drug xydiphone (K,Na-ethidronate) on membrane-bound enzyme damaged by lead ions has been studied. A protein/lipid film of Ca-ATPase/phosphatedylethanolamine deposited on a silicon substrate was used as a model system. The position of lead ions within the molecular film before and after the xydiphone treatment was determined using the total-reflection X-ray fluorescence method. This technique is based on the simultaneous measurement of the X-ray reflection and the yield of the fluorescence radiation excited by X-ray inelastic scattering. The possibility of directly locating lead ions is the main advantage of this approach. Xydiphone has been found to effectively eliminate lead ions that have been incorporated into Ca-ATPase molecules during a preliminary incubation in lead acetate solution. The lead ions that were bound at the sites of the Ca-ATPase attachment to the phospholipid monolayer have proved to be inaccessible for xydiphone. A preliminary incubation of Ca-ATPase in the xydiphone solution precluded the incorporation of lead ions into the protein.

Single crystals of 1 isopropyl 3,3,5´,6´ tetramethylspiro[indoline 2,2´ 2H pyrano[3,2 b] pyridinium] tris(oxalato)chromate(III) (Sp) 3 Cr(C 2 O 4 ) 3 were prepared for the first time. The mo lecular and crystal structure of this salt was studied by X ray diffraction. The crystal structure of the salt consists of the structural units [3(Sp) + ...Cr(C 2 O 4 ) 33-], in which the charged pyranopyri dinium moieties of the photochromic cations (Sp) + are directed toward the oxalate groups, whereas the indoline moieties are directed into the cavities between the structural units. This structure appeared to be favorable for photochromic transformations in the crystals. Under UV irradiation of the (Sp) 3 Cr(C 2 O 4 ) 3 salt, the thermally stable closed form of spiropyran (λ max = 370 nm) is transformed into the open form (λ max = 574 and 603 nm). The reverse cyclization proceeds slowly in the dark (k = 1.0(2)•10 -5 s -1 ) and rapidly under visible light irradiation. The spectroscopic and photochromic properties of the oxalatochromate (Sp) 3 Cr(C 2 O 4 ) 3 are similar to those of the iodide SpI. The magnetic properties of (Sp) 3 Cr(C 2 O 4 ) 3 were studied before and after UV irradiation.