Vanadium Speciation by XANES Spectroscopy: A Three‐Dimensional Approach

“…12a Chart 1. Structures of V Complexes Used for the V Reactions with Blood or Its Components (A−D) and Additional Model Complexes (E−I) 25 Used in the Data Analysis a a The V-oxido binding in V(IV) complexes (B, C, and E) is represented by triple, rather than double, bonds (a combination of one σ and two π bonds), while the bond order in V(V) dioxido complexes (represented as double bonds in D and F) is close to 2.5 30c, 33,34 .…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

“…46 Multiple linear regression analyses of XANES data were performed using Origin software 47 with previously described criteria for a successful fit. 29a Initially, the full set of spectra for model complexes 25 was used for multiple linear regression analyses, but most of the spectral models were rejected computationally during the fitting algorithm due to negative regression coefficients. 29a ■ RESULTS Distribution of Vanadium Complexes between Cell and Plasma Fractions.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

“…The V(V) and V(IV) complexes used to study the reactions with blood and its components (A−D in Chart 1) were either purchased from Aldrich (A; >99%), or synthesized by modified literature procedures (B−D) 35−38 and characterized by elemental analyses, infrared spectroscopy, and electrospray mass spectrometry, as described previously. 25 Newborn calf serum (heat-inactivated and filtered) was purchased from Invitrogen. Other reagents of analytical or higher purity grade were purchased from Sigma-Aldrich or Merck and used without further purification.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

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Reactivity and Speciation of Anti-Diabetic Vanadium Complexes in Whole Blood and Its Components: The Important Role of Red Blood Cells

et al. 2015

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Reactions with blood components are crucial for controlling the antidiabetic, anticancer, and other biological activities of V(V) and V(IV) complexes. Despite extensive studies of V(V) and V(IV) reactions with the major blood proteins (albumin and transferrin), reactions with whole blood and red blood cells (RBC) have been studied rarely. A detailed speciation study of Na3[V(V)O4] (A), K4[V(IV)2O2(citr)2]·6H2O (B; citr = citrato(4-)); [V(IV)O(ma)2] (C; ma = maltolato(-)), and (NH4)[V(V)(O)2(dipic)] (D; dipic = pyridine-2,6-dicarboxylato(2-)) in whole rat blood, freshly isolated rat plasma, and commercial bovine serum using X-ray absorption near-edge structure (XANES) spectroscopy is reported. The latter two compounds are potential oral antidiabetic drugs, and the former two are likely to represent their typical decomposition products in gastrointestinal media. XANES spectral speciation was performed by principal component analysis and multiple linear regression techniques, and the distribution of V between RBC and plasma fractions was measured by electrothermal atomic absorption spectroscopy. Reactions of A, C, or D with whole blood (1.0 mM V, 1-6 h at 310 K) led to accumulation of ∼50% of total V in the RBC fraction (∼10% in the case of B), which indicated that RBC act as V carriers to peripheral organs. The spectra of V products in RBC were independent of the initial V complex, and were best fitted by a combination of V(IV)-carbohydrate (2-hydroxyacid moieties) and/or citrate (65-85%) and V(V)-protein (15-35%) models. The presence of RBC created a more reducing environment in the plasma fraction of whole blood compared with those in isolated plasma or serum, as shown by the differences in distribution of V(IV) and V(V) species in the reaction products of A-D in these media. At physiologically relevant V concentrations (<50 μM), this role of RBC may promote the formation of V(III)-transferrin as a major V carrier in the blood plasma. The results reported herein have broad implications for the roles of RBC in the transport and speciation of metal pro-drugs that have broad applications across medicine.

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“…Recently a useful speciation method, assessment of the chemical states of V, in biological environments was published [125]. Classification can be done on the basis of a three-dimensional diagrams of pre-edge and edge parameters in X-ray absorption near edge decrease their absorption efficacy.…”

Section: Speciation Of Vanadium Complexes In the Gi Tractmentioning

confidence: 99%