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Tri-tert-butoksysilanotiolanowe kompleksy cynku(II), kadmu(II) i kobaltu(II) jako modele koordynacji jonu cynku w miejscu aktywnym dehydrogenazy alkoholowej i niektórych innych enzymów

100%

Dołęga A.

Wiadomości Chemiczne

2010

tom [Z] 64, 5-6

389-411

Zinc is ubiquitous in living organisms and second only to iron among the transition metals. Catalytic zinc sites have been found in all six classes of enzymes. Liver alcohol dehydrogenase (EC 1.1.1.1, LADH, Fig. 1) is a zinc enzyme, which catalyzes reversible oxidation of alcohols to aldehydes utilizing as a co-substrate NAD+. The mechanism of an action of the enzyme is summarized by an equation: R1R2CHOH + NAD+ = R1R2CO + NADH + H+ The coordination of zinc in LADH is usually described as pseudotetrahedral but there were several findings supporting penta-coordination of zinc during the catalytic cycle (Fig. 1 and 2) [1–7]. Studies on synthetic analogues of functional sites of the enzymes are used to elucidate the substrate – metal interactions [8]. Tri-tert-butoxysilanethiol which was used as a ligand to model cysteinate – metal ion centers has several advantageous features. It secures formation of mononuclear transition-metal complexes, exhibits resistance towards hydrolysis, and additionally its pKa value is close to that of cysteine mercapto group [9–11]. Over 20 tri-tertbutoxysilanethiolate complexes with MS2NO2 (M = transition metal) cores were synthesized to model the enzymatic centre of alcohol dehydrogenase, including complexes with water, methanol and ethanol (Fig. 5). Crystal structures of zinc(II), cobalt(II), cadmium(II), and manganese(II) complexes were determined and compared to the structures of LADH [12–17]. Structural features of zinc(II) and cadmium(II) complexes were analyzed (Fig. 9, Tab. 2) [15]. 113Cd CP/MAS NMR spectra of tri-tert-butoxysilanethiolate cadmium(II) complexes were determined and compared with the 113Cd NMR spectra of the cadmium-substituted alcohol dehydrogenase. Solid state 113Cd NMR shifts of five-coordinate cadmium(II) complexes with the CdNO2S2 coordination core were found to be identical to that of cadmium-substituted alcohol dehydrogenase in complex with NAD+ [15,18]. The equilibrium character of the reactions between bis(bis(tri-tert-butoxysilanethiolate) cadmium(II) and nitrogen ligands, with a low equilibrium constant of heteroleptic complex formation, were proved by 113Cd NMR studies in solution [18, 19]. The electronic absorption spectra of heteroleptic cobalt(II) complexes with tri-tert-butoxysilanethiolate and imidazole ligands were measured in methanol and solid state. The equilibrium reactions in the methanolic solutions of cobalt complexes were described on the basis of the analysis of charge transfer bands S→dCo LMCT and the molecular structures of the obtained complexes [17]. EPR spectra revealed the high-spin configuration of the studied cobalt(II) compounds [17]. Quantum mechanical calculations performed on the model zinc complex indicate ca10–20% decrease in enthalpy of ethanol deprotonation due to complexation with Zn2+ [15].

Small sacral architecture in the Sub-Carpathian countryside landscape. The case of Czarnorzeki and Wydrze

51%

Sołtysik A. , Dołęga A. , Szarek N.

Topiarius. Studia krajobrazowe

2017

tom Nr 4

67--85

The characteristic feature of Polish rural landscape is the presence of wayside crosses and shrines which create the unusual atmosphere of countryside. They date back to the early years of Christianity in Poland. At the beginning they were built in former pagan places of worship. Wayside shrines have various architectural forms. In Sub-Carpathian region there are five basic types of wayside shrines: chapel shrine, cabinet shrine, wall shrine, column shrine and pedestal shrine. In those shrines, depending on type, sacred figures were placed in different places – as a crowning in cabinets or in niches?. The presence of shrines and crosses in the landscape of countryside is connected with their various functions. The most important was and still is the sacral function. The surrounding of shrines could be considered in spatial, symbolic and functional context. The examples of small sacral architecture in Sub-Carpathian villages are shrines situated in Czarnorzeki and Wydrze. In Czarnorzeki most common are stone column shrines and in Wydrze chapel shrines.

Charakterystyczną cechą polskiego krajobrazu wiejskiego są przydrożne krzyże i kapliczki tworzące niezwykły klimat wsi. W subtelny sposób wpisują się one w krajobraz. Geneza powstawania kapliczek jest ściśle związana z obecnością religii chrześcijańskiej na terenie Polski. Przydrożne kapliczki przybierają różne formy architektoniczne. W krajobrazie Podkarpacia można wyróżnić pięć podstawowych typów kapliczek: domkowe, szafkowe, wnękowe, słupowe i postumentowe. Kapliczki te, w zależności od typu, najczęściej mieściły w sobie figury świętych lub były nimi zwieńczone. Obecność kapliczek i krzyży w krajobrazie wsi wiąże się z różnymi funkcjami jakie pełniły. Najważniejsza z nich to funkcja sakralna. Otoczenie małej architektury można rozpatrywać w kontekście przestrzennym, symbolicznym i funkcjonalnym. Przykładem są kapliczki znajdujące się na terenie dwóch małych miejscowości Czarnorzek i Wydrza. W Czarnorzekach spotkać można kapliczki słupowe wykonane z kamienia, w krajobrazie Wydrza przeważają kapliczki domkowe.