The article presents a sampling of mechanistic studies on nitric oxide binding to metallobiomolec... more The article presents a sampling of mechanistic studies on nitric oxide binding to metallobiomolecules. The main emphasis falls on the application of ambient and high pressure laser flash photolysis techniques in the elucidation of the mechanism of the reaction of NO with metals in active centres of biomolecules and complexes of potential medicinal application.
Three non-native derivatives of vitamin B12 with imidazole, ethylenediamine, and pyrazine as coba... more Three non-native derivatives of vitamin B12 with imidazole, ethylenediamine, and pyrazine as cobalt(III) β-ligands were characterized by applying the BP/def2-TZVP density functional method. The binding of all three ligands is thermodynamically favorable. It is proposed that their synthesis might be possible from aquacobalamin as a starting form of vitamin B12, as has been done in the case of an imidazole derivative of B12 (Hannibal et al. Inorg. Chem. 2007, 46, 3613-3618). Furthermore, the possibility of the formation of their conjugates with cisplatin is investigated. The proposed β-ligands may serve as bridging ligands, binding to the platin ion as N-donors. In parallel, the calculations are done for the previously synthetized B12-cisplatin adduct with CN(-) as a bridging ligand and are compared with available experimental data, allowing assessment of the applied computational protocol. A good agreement between the computed and experimental structural parameters is obtained. In each of the studied structures, the Co-β-ligand bond is weaker than the Pt-β-ligand bond.
Detailed kinetic and mechanistic studies have been carried out on the reaction between aquacobala... more Detailed kinetic and mechanistic studies have been carried out on the reaction between aquacobalamin/hydroxocobalamin (CblOH2+/CblOH) and nitroxyl (HNO) generated by Piloty's acid (PA, N-hydroxybenzenesulfonamide) over a wide pH range (3.5-13). The resulting data showed that in a basic solution HNO can react with hydroxocobalamin to form nitrosylcobalamin despite the inert nature of CblOH. It was shown that at low PA concentrations the rate-determining step is the decomposition of PhSO2NHO- to release HNO, whereas the reaction between CblOH and HNO becomes the rate-determining step at high PA concentrations. Data from kinetic studies on the reaction of CblOH with an excess of HNO enabled us to experimentally determine the pKa(HNO) value from initial rate data as a function of pH, giving pKa(HNO) = 11.47 ± 0.04. An especially interesting observation was made in the neutral pH range, where PA is stable and does not produce HNO. Under such conditions, rapid formation of CblNO was observed in the studied system. The obtained data suggest that CblOH2+ reacts directly with PA to form a Piloty's acid-bound cobalamin intermediate, which deprotonates rapidly at neutral pH followed by rate-determining S-N bond cleavage to give CblNO and release PhSO2-.
The insertion of palladium(II) into di‐p‐pyrirubyrin results in mutually convertible bimetallic c... more The insertion of palladium(II) into di‐p‐pyrirubyrin results in mutually convertible bimetallic complexes. Post‐synthetic functionalization of one of them yielded bispalladium(II) dioxo‐di‐p‐pyrirubyrin and, after demetallation, dioxo‐di‐p‐pyrirubyrin, introducing for the first time the α,β′‐pyridin‐2‐one unit into the macrocyclic frame. Bispalladium(II) di‐p‐pyrirubyrin 6, bispalladium(II) dioxo‐di‐p‐pyrirubyrin 9, and dioxo‐di‐p‐pyrirubyrin 10 absorb and emit light around 1000 nm and are characterized by high photostability. Thus, they are promising candidates for near‐infrared photoacoustic dyes, ideally targeting (9) the wavelength of Yb‐based fiber lasers. The incorporation of an α,β′‐pyridine moiety into expanded porphyrins opens a highly interesting area of research due to the attractive optical and coordination properties of the resulting molecules.
Besides the well-known functions performed by vitamin B12 (CblCN) in biochemical processes of the... more Besides the well-known functions performed by vitamin B12 (CblCN) in biochemical processes of the human body, an increasing interest has been raised by the possibility of its use as a transmembrane drug carrier, capable, among others, of enhancing the accumulation of inorganic cytostatics in cancer cells. The present study was aimed at determining the possibility of the formation of CblCN conjugates with Pd(II) complexes. A key aspect was their stability, which we attempted to tune by appropriate choice of ligands. Syntheses, spectroscopic analysis of postreaction systems and kinetic investigations of conjugate formation reactions, have been complemented by DFT modelling. The obtained results showed that ligand charge, geometry and electron affinity may have a significant impact on carrier binding and release leading to the activation of the Pd(II) complex. This provides a rationale to expect that with appropriate composition of the coordination sphere, it will be possible to extend...
Detailed kinetic and mechanistic studies have been carried out on the reaction between aquacobala... more Detailed kinetic and mechanistic studies have been carried out on the reaction between aquacobalamin/hydroxocobalamin (CblOH2+/CblOH) and nitroxyl (HNO) generated by Piloty's acid (PA, N-hydroxybenzenesulfonamide) over a wide pH range (3.5-13). The resulting data showed that in a basic solution HNO can react with hydroxocobalamin to form nitrosylcobalamin despite the inert nature of CblOH. It was shown that at low PA concentrations the rate-determining step is the decomposition of PhSO2NHO- to release HNO, whereas the reaction between CblOH and HNO becomes the rate-determining step at high PA concentrations. Data from kinetic studies on the reaction of CblOH with an excess of HNO enabled us to experimentally determine the pKa(HNO) value from initial rate data as a function of pH, giving pKa(HNO) = 11.47 ± 0.04. An especially interesting observation was made in the neutral pH range, where PA is stable and does not produce HNO. Under such conditions, rapid formation of CblNO was observed in the studied system. The obtained data suggest that CblOH2+ reacts directly with PA to form a Piloty's acid-bound cobalamin intermediate, which deprotonates rapidly at neutral pH followed by rate-determining S-N bond cleavage to give CblNO and release PhSO2-.
The article presents a sampling of mechanistic studies on nitric oxide binding to metallobiomolec... more The article presents a sampling of mechanistic studies on nitric oxide binding to metallobiomolecules. The main emphasis falls on the application of ambient and high pressure laser flash photolysis techniques in the elucidation of the mechanism of the reaction of NO with metals in active centres of biomolecules and complexes of potential medicinal application.
MnIII(TPPS) is oxidized by an excess of hydrogen peroxide in basic aqueous solution to yield MnV(... more MnIII(TPPS) is oxidized by an excess of hydrogen peroxide in basic aqueous solution to yield MnV(TPPS) and/or MnIVTPPS, and subsequently reduced back to MnIII(TPPS) to reveal redox cycling, catalase and degradation activities.
Laser flash photolysis (LFP) is a powerful tool for spectroscopic and kinetic determination of bo... more Laser flash photolysis (LFP) is a powerful tool for spectroscopic and kinetic determination of both primary photophysical transformations and rapid chemical reactions. This method is very useful in mechanistic studies of fast reactions and detection of transition states and intermediates. The main goal of the review is to point out some current applications of LFP in chemical, biological, biochemical, and
The article presents a sampling of mechanistic studies on nitric oxide binding to metallobiomolec... more The article presents a sampling of mechanistic studies on nitric oxide binding to metallobiomolecules. The main emphasis falls on the application of ambient and high pressure laser flash photolysis techniques in the elucidation of the mechanism of the reaction of NO with metals in active centres of biomolecules and complexes of potential medicinal application.
Three non-native derivatives of vitamin B12 with imidazole, ethylenediamine, and pyrazine as coba... more Three non-native derivatives of vitamin B12 with imidazole, ethylenediamine, and pyrazine as cobalt(III) β-ligands were characterized by applying the BP/def2-TZVP density functional method. The binding of all three ligands is thermodynamically favorable. It is proposed that their synthesis might be possible from aquacobalamin as a starting form of vitamin B12, as has been done in the case of an imidazole derivative of B12 (Hannibal et al. Inorg. Chem. 2007, 46, 3613-3618). Furthermore, the possibility of the formation of their conjugates with cisplatin is investigated. The proposed β-ligands may serve as bridging ligands, binding to the platin ion as N-donors. In parallel, the calculations are done for the previously synthetized B12-cisplatin adduct with CN(-) as a bridging ligand and are compared with available experimental data, allowing assessment of the applied computational protocol. A good agreement between the computed and experimental structural parameters is obtained. In each of the studied structures, the Co-β-ligand bond is weaker than the Pt-β-ligand bond.
Detailed kinetic and mechanistic studies have been carried out on the reaction between aquacobala... more Detailed kinetic and mechanistic studies have been carried out on the reaction between aquacobalamin/hydroxocobalamin (CblOH2+/CblOH) and nitroxyl (HNO) generated by Piloty's acid (PA, N-hydroxybenzenesulfonamide) over a wide pH range (3.5-13). The resulting data showed that in a basic solution HNO can react with hydroxocobalamin to form nitrosylcobalamin despite the inert nature of CblOH. It was shown that at low PA concentrations the rate-determining step is the decomposition of PhSO2NHO- to release HNO, whereas the reaction between CblOH and HNO becomes the rate-determining step at high PA concentrations. Data from kinetic studies on the reaction of CblOH with an excess of HNO enabled us to experimentally determine the pKa(HNO) value from initial rate data as a function of pH, giving pKa(HNO) = 11.47 ± 0.04. An especially interesting observation was made in the neutral pH range, where PA is stable and does not produce HNO. Under such conditions, rapid formation of CblNO was observed in the studied system. The obtained data suggest that CblOH2+ reacts directly with PA to form a Piloty's acid-bound cobalamin intermediate, which deprotonates rapidly at neutral pH followed by rate-determining S-N bond cleavage to give CblNO and release PhSO2-.
The insertion of palladium(II) into di‐p‐pyrirubyrin results in mutually convertible bimetallic c... more The insertion of palladium(II) into di‐p‐pyrirubyrin results in mutually convertible bimetallic complexes. Post‐synthetic functionalization of one of them yielded bispalladium(II) dioxo‐di‐p‐pyrirubyrin and, after demetallation, dioxo‐di‐p‐pyrirubyrin, introducing for the first time the α,β′‐pyridin‐2‐one unit into the macrocyclic frame. Bispalladium(II) di‐p‐pyrirubyrin 6, bispalladium(II) dioxo‐di‐p‐pyrirubyrin 9, and dioxo‐di‐p‐pyrirubyrin 10 absorb and emit light around 1000 nm and are characterized by high photostability. Thus, they are promising candidates for near‐infrared photoacoustic dyes, ideally targeting (9) the wavelength of Yb‐based fiber lasers. The incorporation of an α,β′‐pyridine moiety into expanded porphyrins opens a highly interesting area of research due to the attractive optical and coordination properties of the resulting molecules.
Besides the well-known functions performed by vitamin B12 (CblCN) in biochemical processes of the... more Besides the well-known functions performed by vitamin B12 (CblCN) in biochemical processes of the human body, an increasing interest has been raised by the possibility of its use as a transmembrane drug carrier, capable, among others, of enhancing the accumulation of inorganic cytostatics in cancer cells. The present study was aimed at determining the possibility of the formation of CblCN conjugates with Pd(II) complexes. A key aspect was their stability, which we attempted to tune by appropriate choice of ligands. Syntheses, spectroscopic analysis of postreaction systems and kinetic investigations of conjugate formation reactions, have been complemented by DFT modelling. The obtained results showed that ligand charge, geometry and electron affinity may have a significant impact on carrier binding and release leading to the activation of the Pd(II) complex. This provides a rationale to expect that with appropriate composition of the coordination sphere, it will be possible to extend...
Detailed kinetic and mechanistic studies have been carried out on the reaction between aquacobala... more Detailed kinetic and mechanistic studies have been carried out on the reaction between aquacobalamin/hydroxocobalamin (CblOH2+/CblOH) and nitroxyl (HNO) generated by Piloty's acid (PA, N-hydroxybenzenesulfonamide) over a wide pH range (3.5-13). The resulting data showed that in a basic solution HNO can react with hydroxocobalamin to form nitrosylcobalamin despite the inert nature of CblOH. It was shown that at low PA concentrations the rate-determining step is the decomposition of PhSO2NHO- to release HNO, whereas the reaction between CblOH and HNO becomes the rate-determining step at high PA concentrations. Data from kinetic studies on the reaction of CblOH with an excess of HNO enabled us to experimentally determine the pKa(HNO) value from initial rate data as a function of pH, giving pKa(HNO) = 11.47 ± 0.04. An especially interesting observation was made in the neutral pH range, where PA is stable and does not produce HNO. Under such conditions, rapid formation of CblNO was observed in the studied system. The obtained data suggest that CblOH2+ reacts directly with PA to form a Piloty's acid-bound cobalamin intermediate, which deprotonates rapidly at neutral pH followed by rate-determining S-N bond cleavage to give CblNO and release PhSO2-.
The article presents a sampling of mechanistic studies on nitric oxide binding to metallobiomolec... more The article presents a sampling of mechanistic studies on nitric oxide binding to metallobiomolecules. The main emphasis falls on the application of ambient and high pressure laser flash photolysis techniques in the elucidation of the mechanism of the reaction of NO with metals in active centres of biomolecules and complexes of potential medicinal application.
MnIII(TPPS) is oxidized by an excess of hydrogen peroxide in basic aqueous solution to yield MnV(... more MnIII(TPPS) is oxidized by an excess of hydrogen peroxide in basic aqueous solution to yield MnV(TPPS) and/or MnIVTPPS, and subsequently reduced back to MnIII(TPPS) to reveal redox cycling, catalase and degradation activities.
Laser flash photolysis (LFP) is a powerful tool for spectroscopic and kinetic determination of bo... more Laser flash photolysis (LFP) is a powerful tool for spectroscopic and kinetic determination of both primary photophysical transformations and rapid chemical reactions. This method is very useful in mechanistic studies of fast reactions and detection of transition states and intermediates. The main goal of the review is to point out some current applications of LFP in chemical, biological, biochemical, and
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