X-ray and conformational analysis of methyl 3-amino-2,3-dideoxy-α-d-arabino-hexopyranoside

Modification of DNA structure by reactive nitrogen species as a result of 2-methoxyestradiol-induced neuronal nitric oxide synthase uncoupling in metastatic osteosarcoma cells

2-methoxyestradiol (2-ME) is a physiological anticancer compound, metabolite of 17β-estradiol. Previously, our group evidenced that from mechanistic point of view one of anticancer mechanisms of action of 2-ME is specific induction and nuclear hijacking of neuronal nitric oxide synthase (nNOS), resulting in local generation of nitro-oxidative stress and finally, cancer cell death.

The current study aims to establish the substantial mechanism of generation of reactive nitrogen species by 2-ME. We further achieved to identify the specific reactive nitrogen species involved in DNA-damaging mechanism of 2-ME.

The study was performed using metastatic osteosarcoma 143B cells. We detected the release of biologically active (free) nitric oxide (^•NO) with concurrent measurements of peroxynitrite (ONOO⁻) in real time in a single cell of 143B cell line by using ^•NO/ONOO⁻ sensitive microsensors after stimulation with calcium ionophore. Detection of nitrogen dioxide (^•NO₂) and determination of chemical rate constants were carried out by a stopped-flow technique. The affinity of reactive nitrogen species toward the guanine base of DNA was evaluated by density functional theory calculations. Expression and localization of nuclear factor NF-kB was determined using imaging cytometry, while cell viability assay was evaluated by MTT assay.

Herein, we presented that 2-ME triggers pro-apoptotic signalling cascade by increasing cellular reactive nitrogen species overproduction – a result of enzymatic uncoupling of increased nNOS protein levels. In particular, we proved that ONOO⁻ and ^•NO₂ directly formed from peroxynitrous acid (ONOOH) and/or by auto-oxidation of ^•NO, are inducers of DNA damage in anticancer mechanism of 2-ME. Specifically, the affinity of reactive nitrogen species toward the guanine base of DNA, evaluated by density functional theory calculations, decreased in the order: ONOOH > ONOO⁻ > ^•NO₂ > ^•NO.

Therefore, we propose to consider the specific inducers of nNOS as an effective tool in the field of chemotherapy.

How the configurational changes influence on molecular characteristics. The alkyl 3-azido-2,3-dideoxy-D-hexopyranosides - Theoretical approach

In this paper we present two currents of our research. The first goal was the geometry optimization of the structures of derivatives of the alkyl 3-azido-2,3-dideoxy-D-hexopyranosides. Then, we examine the influence of the applied quantum methods on the values of molecular features describing these structures. We use two methods for geometry optimization: the semi-empirical PM7 method and DFT B3LYP/6-31++G* method. The results of comparison parameters of descriptors indicate that there are no statistical differences obtained from both methods. Thus, we recommend the PM7 method for geometry optimization of the derivatives of the alkyl 3-azido-2,3-dideoxy-D-hexopyranosides due to its time and computer resources requirements. Another part of the research was the examination, which groups of descriptors are the most suitable for identifying the similarities in the configuration, the substituents pattern and the molecular mass of 232 examined structures. To explore relation between configuration changes of the 3-azidosaccharides and influence of these changes on the molecular characteristic, we use hierarchical cluster analysis (HCA), where WHIM, 3D-MORSE, RDF and GETAWAY descriptors were selected. Depending on the group of descriptors, molecules are divided in various ways. In general, saccharide' structures are divided into groups based on the configuration of substituents (combination of epimers) or length of the O-glycoside chain. Never before, these saccharides derivatives, were investigated by chemometric analysis. The most problematic issue in experimental and theoretical research is the configuration of substituents in pyranoside ring. Due to vast number of configurations, it is possible to obtain massive amount of diverse structures. This problem concerns us and opens opportunity in investigation the effect of configuration on the parameter of molecules.

Stopped-flow spectrophotometric study of the kinetics and mechanism of CO₂ uptake by cis-[Cr(C₂O₄)(BaraNH₂)(OH₂)₂]+ cation and the acid-catalyzed decomposition of cis-[Cr(C₂O₄)(BaraNH₂)OCO₂]- anion in aqueous solution

The kinetics of CO₂ uptake by the cis-[Cr(C₂O₄)(BaraNH₂)(OH₂)₂]⁺ complex cation and the acid hydrolysis of the cis-[Cr(C₂O₄)(BaraNH₂)OCO₂]⁻ complex anion (where BaraNH₂ denotes methyl 3-amino-2,3-dideoxy-β-D-arabino-hexopyranoside) were studied using the stopped-flow technique. The reactions under study were investigated in aqueous solution in the 288–308 K temperature range. In the case of the reaction between CO₂ and cis-[Cr(C₂O₄)(BaraNH₂)(OH₂)₂]⁺ cation variable pH values (6.82–8.91) and the constant ionic strength of solution (H⁺, Na⁺, ClO₄⁻ = 1.0) were used. Carbon dioxide was generated by the reaction between sodium pyruvate and hydrogen peroxide. The acid hydrolysis of cis-[Cr(C₂O₄)(BaraNH₂)OCO₂]⁻ was investigated for varying concentrations of H⁺ ions (0.01–2.7 M). The obtained results enabled the determination of the number of steps of the studied reactions. Based on the kinetic equations, rate constants were determined for each step. Finally, mechanisms for both reactions were proposed and discussed. Based on the obtained results it was concluded that the carboxylation (CO₂ uptake) reactions of cis-[Cr(C₂O₄)(BaraNH₂)(OH₂)₂]⁺ and the decarboxylation (acid hydrolysis) of the cis-[Cr(C₂O₄)(BaraNH₂)OCO₂]⁻are the opposite of each other.

A novel biosensor for evaluation of apoptotic or necrotic effects of nitrogen dioxide during acute pancreatitis in rat

The direct and accurate estimation of nitric dioxide levels is an extremely laborious and technically demanding procedure in the molecular diagnostics of inflammatory processes. The aim of this work is to demonstrate that a stop-flow technique utilizing a specific spectroscopic biosensor can be used for detection of nanomolar quantities of NO(2) in biological milieu. The use of novel compound cis-[Cr(C(2)O(4))(AaraNH(2))(OH(2))(2)](+) increases NO(2) estimation accuracy by slowing down the rate of NO(2) uptake. In this study, an animal model of pancreatitis, where nitrosative stress is induced by either 3g/kg bw or 1.5 g/kg bw dose of L-arginine, was used. Biochemical parameters and morphological characteristics of acute pancreatitis were monitored, specifically assessing pancreatic acinar cell death mode, NO(2) generation and cellular glutathione level. The severity of the process correlated positively with NO(2) levels in pancreatic acinar cell cytosol samples, and negatively with cellular glutathione levels.

Crystal structures of ethyl 3-azido-2,3-dideoxy-D-arabino-hexopyranoside anomers

The structures of the title alpha (1) and beta (2) anomers of ethyl 3-azido-2,3-dideoxy-d-arabino-exopyranoside (C(8)H(15)N(3)O(4)) are reported. The single-crystal structures of C(8)H(15)N(3)O(4) were determined by X-ray crystallography at 293K. It has been found that both title compounds crystallize in the orthorhombic space group. In both cases, the unit cell contains four asymmetric molecules. From intensity measurements, it has been shown that each of these molecules adopts a (4)C(1) chair conformation. The packing arrangement in the unit cell displays a stratified structure. Moreover, medium strength O-H...O hydrogen bonds in both crystal lattices can be observed.

Crystal structure of methyl 3-amino-2,3-dideoxy-beta-D-arabino-hexopyranoside. Stabilization of the crystal lattice by a double network of N-H...O, O-H...N and O-H...O interactions

The structure, conformation and configuration of methyl 3-amino-2,3-dideoxy-beta-D-arabino-hexopyranoside were investigated by (1)H NMR, (13)C NMR and IR spectroscopy, as well as by optical rotation. The crystal structure was confirmed by single-crystal X-ray crystallographic analysis at 293 K and R = 0.0434 based on 910 independent reflections. The crystal belongs to the monoclinic system, space group of P2(1) with cell dimensions a = 6.050(1) Angstroms, b = 7.284(1) Angstroms, c = 10.289(2) Angstroms, beta = 104.69(3) degrees, D(c) = 1.341 Mg cm(-3) and V = 438.9(1) Angstroms(3) for Z = 2. Furthermore, the molecule has a typical (4)C(1) chair conformation. Hydrogen bonds between sugar molecules are responsible for stabilizing the crystal lattice.

Pivotal participation of nitrogen dioxide in L-arginine induced acute necrotizing pancreatitis: protective role of superoxide scavenger 4-OH-TEMPO

For the first time, a direct sensitive method of *NO(2) detection and measurement in biological material has been established. It is based on the interaction of this radical with the coordination compound of Cr(III) with aminodeoxysugar as biosensor. Our new method makes it possible to precisely assess *NO(2) level in experimental acute necrotizing pancreatitis induced by L-arginine, where oxidative and nitrosative stresses are supposed to play a key role in the pathomechanism of the disease. As much as 20 nmol of *NO(2)/mg protein was detected which correlated with severe deterioration of pancreatic acinar cell ultrastructure. Protective effect of superoxide radical scavenger 4-OH-TEMPO expressed as *NO(2) level decrease confirmed by preserved acinar cell ultrastructure and decreased pancreatic amylase release to blood serum is demonstrated. This study reveals a possible pathomechanism of L-arginine induced acute pancreatitis.