Possibilities of multinuclear NMR in the chemistry of heteroorganic compounds

Results of multinuclear NMR studies of some heteroorganic compounds have been presented.According to a report at the conference «Current problems of organometallic chemistry» (May 8–13,1994, Moscow).Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 614–616, April, 1994.     

A kinetic study of the oxidation of hydroxamic acids by compounds I and II of horseradish peroxidase: Effect of transition metal ions

Abstract

Oxidation of hydroxamic acids (HXs) generates HNO, and it is not clear whether it is formed also in the presence of metal ions. The kinetics of the oxidation of HXs, such as acetohydroxamic acid, suberohydroxamic acid, and suberoylanilide hydroxamic acid (SAHA), by compounds I and II of horseradish peroxidase (HRP) at pH 7.0 and 25?°C have been studied using rapid-mixing stopped-flow. The kinetics of these reactions were compared to those observed in the presence of Cu(ClO₄)₂, NiSO₄, or ZnSO₄. The rates decrease upon increasing [Cu^II] at constant [HXs], and no oxidation of HX occurs when [HX]/[Cu^II] ≈ 2, implying that HX oxidation in the presence of Cu^II proceeds through the free ligand since the predominant complex is CuX₂. In the case of Ni^II, the oxidation rate decreases upon increasing the ratio [Ni^II]/[HX] beyond 1, where the predominant complex is Ni^IIX⁺, implying that its oxidation is feasible. The effect of Zn^II could be studied only on the rate of HXs oxidation by compound II demonstrating similar behavior to that of Ni^II. HXs were also oxidized catalytically by HRP/H₂O₂ at pH 7.0, demonstrating that metal ions facilitate the formation of HNO while hardly affecting its yield and the extent of HX oxidation.     

Studies on the P-branch spectral lines of rovibrational transitions of diatomic system

An analytical formula is used to predict the accurate P-branch spectral lines of rovibrational transitions for diatomic systems. The formula is derived from elementary expression of molecular total energy by taking multiple spectral differences. It is not only reproduces the known experimental transition lines by using a group of fifteen known experimental transition data, but also predicts the accurate spectral lines that may not be available experimentally. The P-branch emission spectra of the (0,1), (0,2) and (0,3) bands of the B(2)∑(+)→X(2)∑(+) system in the (12)C(17)O(+) molecular ion are studied, and correct values of the unknown spectral lines up to J=80.5 for each band are predicted using the formula.     

15N NMR spectral parameters of compounds of the N-methylpyrazole series

The¹⁵N NMR chemical shifts and¹⁵N-¹H SSCCs are presented for substituted N-methylpyrazoles with substituents such as CH₃, NO₂, Br, Cl, NH₂, O=CNH₂, O=CPh, and COOH at the carbon atoms. The¹⁵N chemical shifts of the cyclic atoms of nitrogen and the nitro groups are discussed as well as the geminal and vicinal SSCCs of the ring nitrogen atoms with the hydrogen atoms of the CH and CH₃ fragments.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117334 Moscow. D. I. Mendeleev Chemico-Technological Institute, Moscow, Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 11, pp. 2554–2561, November, 1992.     

The Synthesis and the Cationic Fluorescence Role of Glycols with Aromatic End Groups, Part III

Some novel bis-(substituted-phenoxy) ended glycols were synthesised usinghydroxy aromatics of vanillin, o-vanillin, iso-vanillin and 4-hydroxy coumarin which reacted with bis-dihalides of polyglycols in the presence ofDMSO/alkali carbonate. The novel podands, Ar-(CH₂CH₂O)_m-Ar,(m = 1–4), were identified with IR, ¹H-NMR, ¹³C-NMR and mass spectrometry. The various (formyl-methoxy)phenyl and 4-oxycoumarin derivatives of glycols were studied to estimate the cation binding selectivity of SCN^- salts ofLi⁺, Na⁺, K⁺ and Zn²⁺ cations in acetonitrile using steady statefluorescence spectroscopy. The relevant structures of podands have shown goodselectivity depending on the cation and the glycollength, although the chromophoreend groups have no specific contribution on binding.     

表面修饰纳米CdS制备中两个重要影响因素及结构表征

利用溶胶-凝胶法制备了PVP表面修饰的CdS纳米晶粒。考察了影响纳米CdS制备的两个重要因素Cd²⁺/S^2-和PVP,及其作用机理。确证表面过剩S^2-和PVP在反应体系中的作用是在较高浓度下制备纳米CdS的两个重要因素,进一步确定了PVP的最佳用量。通过TEM、ED、XRD、FT-IR等手段对合成的纳米粒子进行了结构表征,最小粒径为7～10nm,闪锌矿构型,粒子大小及形貌可通过改变Cd²⁺/S^2-及反应物浓度来控制。最后给出了CdS/PVP纳米晶粒的结构模型。     

NMR structural aspects of the chemistry of V, Mo, W polyoxometalates

The results of structural investigations of vanadium, molybdenum, and tungsten polyoxoanions (PA) by ¹⁷O, ⁵¹V, ⁹⁵Mo, ¹⁸³W, and heteroatom NMR are generalized in this review. NMR spectroscopy possibilities to determine the structure of PA are discussed. NMR data on PA of different structures compositions nuclei are demonstrated.     

Specificity and Origin of the Stability of the Sr Isotopic Ratio in Champagne Wines

The ⁸⁷Sr/⁸⁶Sr ratio of 39 Champagnes from six different brands, originating from the whole “Appellation d’Origine Contrôlée” (AOC) Champagne was analyzed to establish a possible relation with the geographical origin. Musts (i.e., grape juice) and base wines were also analyzed to study the evolution of the Sr isotopic ratio during the elaboration process of sparkling wine. The results demonstrate that there is a very homogeneous Sr isotopic ratio (⁸⁷Sr/⁸⁶Sr = 0.70812, n = 37) and a narrow span of variability (2σ = 0.00007, n = 37). Moreover, the Sr concentrations in Champagnes have also low variability, which can be in part explained by the homogeneity of the bedrock in the AOC Champagne. Measurements of the ⁸⁷Sr/⁸⁶Sr ratio from musts and base wines show that blending during Champagne production plays a major role in the limited variability observed. Further, the ⁸⁷Sr/⁸⁶Sr of the musts were closely linked to the ⁸⁷Sr/⁸⁶Sr ratio of the vineyard soil. It appears that the ⁸⁷Sr/⁸⁶Sr of the product does not change during the elaboration process, but its variability decreases throughout the process due to blending. Both the homogeneity of the soil composition in the Champagne AOC and the blending process during the wine making process with several blending steps at different stages account for the unique and stable Sr isotopic signature of the Champagne wines.     

新型吸附剂的合成、表征及其对Ni(II)的吸附研究

利用滴加法合成了球形含Ni^2＋交联壳聚糖, 并通过胺化引入大量活性氨基, 再经除镍制成对重金属镍离子具有较好吸附能力的新型吸附剂[P-C-CTS(Ni)]. 通过Ni^2＋吸附容量的测定, IR及XPS分析, 验证了合成技术路线的正确性. 通过研究pH值对吸附量的影响, 初步讨论了无柠檬酸根(Cit)配位体存在时, 吸附剂对Ni(II)的吸附为螯合作用. 通过Cit存在条件下(c_Ni＝c_Cit＝0.852 mmol•L^－1), 吸附剂对Ni(II)离子和Cit的吸附量随pH值的变化, 结合相应pH值下金属镍的形态分布, 探讨了其对Ni(II)的吸附机理, 研究认为不仅仅是简单的螯合作用, 其吸附机理和吸附量与溶液中金属离子的存在形式有关, 引入静电吸附原理解释了吸附剂对Ni(II)的吸附现象.     

Structural Insights into the Interactions of Digoxin and Na+/K+-ATPase and Other Targets for the Inhibition of Cancer Cell Proliferation

Digoxin is a cardiac glycoside long used to treat congestive heart failure and found recently to show antitumor potential. The hydroxy groups connected at the C-12, C-14, and C-3′a positions; the C-17 unsaturated lactone unit; the conformation of the steroid core; and the C-3 saccharide moiety have been demonstrated as being important for digoxin’s cytotoxicity and interactions with Na⁺/K⁺-ATPase. The docking profiles for digoxin and several derivatives and Na⁺/K⁺-ATPase were investigated; an additional small Asn130 side pocket was revealed, which could be useful in the design of novel digoxin-like antitumor agents. In addition, the docking scores for digoxin and its derivatives were found to correlate with their cytotoxicity, indicating a potential use of these values in the prediction of the cancer cell cytotoxicity of other cardiac glycosides. Moreover, in these docking studies, digoxin was found to bind to FIH-1 and NF-κB but not HDAC, IAP, and PI3K, suggesting that this cardiac glycoside directly targets FIH-1, Na⁺/K⁺-ATPase, and NF-κB to mediate its antitumor potential. Differentially, digoxigenin, the aglycon of digoxin, binds to HDAC and PI3K, but not FIH-1, IAP, Na⁺/K⁺-ATPase, and NF-κB, indicating that this compound may target tumor autophagy and metabolism to mediate its antitumor propensity.     

Nuclear magnetic resonance of donor atoms as a tool for determination of the structure of platinum metal complexes in solutions

Data on the NMR spectroscopy of C, N, O, Si, P, and Sn donor atoms of platinum metal complexes in solutions are surveyed. The chemical shift of a donor atom mainly depends on the ligand in the trans-position (due to the trans-effect). The chemical shift of a donor atom on a particular coordinate of the complex (coordinate shift, CSh) is an attribute of this coordinate and can be used to identify such a coordinate in platinum metal complexes and to determine the structures of complexes. Based on the known data, CSh diagrams were composed for ¹H, ¹³C, ¹⁴N, ¹⁷O, ¹⁹F, ³¹P, and ¹¹⁹Sn. Examples of using the CShs for determining the structures of platinum metal complexes in solutions are presented.     

八肋游仆虫中心蛋白N端半分子Loop区首个氨基酸的作用

本文通过分子生物学方法将八肋游仆虫中心蛋白N端半分子loop区的首个氨基酸,天冬氨酸Asp37和Asp73,分别突变为带相反电荷的赖氨酸。使用铽敏化荧光、TNS疏水探针研究了八肋游仆虫中心蛋白N端半分子loop区的首个氨基酸的作用。结果表明：当中心蛋白loop Ⅰ区37位的天冬氨酸突变为赖氨酸后,loop Ⅰ丧失了金属离子结合能力,进而影响了中心蛋白依赖于金属离子的构象变化;而loop Ⅱ区73位的天冬氨酸突变为赖氨酸后仍保持金属离子结合能力,依赖于金属离子的构象变化减小。中心蛋白发挥大部分生物功能都依赖于金属离子,这就表明loop Ⅰ区37位的天冬氨酸在中心蛋白发挥生物功能时起着重要作用,是不可缺少的。在10 mmol·L^-1 Hepes、pH 7.4、20 mmol·L^-1 KCl条件下,八肋游仆虫中心蛋白N端半分子loop Ⅱ与金属离子Tb³⁺和Ca²⁺的结合常数分别为：K_Ⅱ(Tb³⁺)=(8.31±0.18)×10⁴ L·mol^-1和K_Ⅱ(Ca²⁺)=(0.94±0.12)×10² L·mol^-1,中心蛋白N端半分子的两个金属结合部位结合能力顺序为：Ⅰ>Ⅱ。     

Thionation of the monoacetal of pentacyclo[5.4.0.0.0.0]undecane-8,11-dione

As part of a programme to synthesize thione derivatives with pentacyclo[5.4.0.0^2,6.0^3,10.0^5,9]undecane moieties it was decided to sulfurize the monoacetal 6 of pentacyclo[5.4.0.0^2,6.0^3,10.0^5,9]undecane-8,11-dione 2. Unexpectedly the diol 9 was isolated as the product.     

Recombination of KrD and XeD ions with electrons

Recombination rate coefficients of protonated and deuterated ions KrH⁺, KrD⁺, XeH⁺ and XeD⁺ were measured using Flowing Afterglow with Langmuir Probe (FALP). Helium at 1600 Pa and at temperature 250 K was used as a buffer gas in the experiments. Kr, Xe, H₂ and D₂ were introduced to a flow tube to form the desired ions. Because of small differences in proton affinities of Kr, D₂ and H₂ mixtures of ions, KrD⁺/D₃⁺ and KrH⁺/H₃⁺ are formed in the afterglow plasma, influencing the plasma decay. To obtain a recombination rate coefficient for a particular ion, the dependencies on partial pressures of gases used in the ion formation were measured. The obtained rate coefficients, α_KrD+(250 K) = (0.9 ± 0.3) × 10⁻⁸ cm³ s⁻¹ and α_XeD+(250 K) = (8 ± 2) × 10⁻⁸ cm³ s⁻¹ are compared with α_KrH+(250 K) = (2.0 ± 0.6) × 10⁻⁸ cm³ s⁻¹ and α_XeH+(250 K) = (8 ± 2) × 10⁻⁸ cm³ s⁻¹.     

Preparation of the novel fluorine-18-labeled VIP analog for PET imaging studies using two different synthesis methods

Vasoactive intestinal peptide (VIP) receptors are expressed on various tumor cells in much higher density than somatostatin receptors, which provides the basis for radiolabeling VIP as tumor diagnostic agent. However, fast proteolytic degradation of VIP in vivo limits its clinical application. With the aim to develop and evaluate new ligands for depicting the VIP receptors with positron emission tomography (PET), the structure modified [R^8,15,21, L¹⁷]-VIP analog was radiolabeled with ¹⁸F using two different methods. With the first method, N-4-[¹⁸F]fluorobenzoyl-[R^8,15,21, L¹⁷]-VIP ([¹⁸F]FB-[R^8,15,21, L¹⁷]-VIP 7) was produced in a decay-corrected radiochemical yield (RCY) of 33.6 ± 3%, a specific radioactivity of 255 GBq/μmol (n = 5) within 100 min in four steps. Similarly, N-4-[¹⁸F](fluoromethyl)-benzoyl-[R^8,15,21, L¹⁷]-VIP ([¹⁸F]FMB-[R^8,15,21, L¹⁷]-VIP 8) was synthesized in a RCY of 34.85 ± 5%, a specific radioactivity of 180 GBq/μmol (n = 5) within 60 min in only one step. The two products 7 and 8 were both shown good stability in HSA. Moreover, the low bone uptakes of 7 and 8 in vivo of mice showed good defluorination stability.     

The fractionation and determination procedures for the speciation of Pb and Po in soil samples

A method for speciation and determination of ²¹⁰Pb and ²¹⁰Po in soil samples was developed. The speciation was carried out by fractionating the soil samples into five fractions which are water soluble or exchangeable, bound to carbonates, bound to Fe-Mn oxides, bound to organic matter and bound to residue. After mineralisation, 10% solution of each fraction was used to spontaneously deposit polonium on a silver disk at 85-90 °C and pH 1.5, and ²¹⁰Po was measured by α-spectrometry; the remain solution was used to separate lead by anion-exchange resin and purified by precipitation as PbS and PbSO₄, and ²¹⁰Pb was determined by a low background β-counter. The IAEA-327 reference material (soil) was studied for ²¹⁰Pb and ²¹⁰Po speciation. The results show that: (1) the average yields are 88.7 ± 6.4% for ²¹⁰Pb and 93.8 ± 8.2% for ²¹⁰Po; (2) if compared to the total ²¹⁰Pb activity in the sample, ²¹⁰Pb fractions are 0.95% in exchangeable form, 10.6% bound to carbonates, 14.3% bound to Fe-Mn oxides, 7.0% bound to organic matter and 67.2% bound to residue or acid soluble, and the corresponding values for ²¹⁰Po are 0.17%, 0.97%, 21.0%, 0.47% and 77.4%, respectively; and (3) the obtained ²¹⁰Pb concentration is in good agreement with the recommended value given by the IAEA.     

Synthesis and structural characterization of nitrite-coordinating CoII and CoIII complexes as models for the reaction center of Co-substituted nitrite reductase

Co^II and Co^III complexes containing nitrite and tridentate aromatic amine compounds [bis(6-methyl-2-pyridylmethyl)amine (Me₂bpa) and bis(2-pyridylmethyl)amine (bpa)] have been prepared as models of the catalytic center in Co-substituted nitrite reductase: [Co^II(Me₂bpa)(NO₂)Cl]₂ · acetone (2), Co^II(Me₂bpa)(NO₂)₂ (3), Co^II(bpa)(NO₂)Cl (4), Co^II(bpa)(NO₂)₂ (5), Co^III(Me₂bpa)(NO₂)(CO₃) (6), and Co^III(bpa)(NO₂)₃ (7). The X-ray crystal structure analyses of these Co^II and Co^III complexes indicated that the geometries of the cobalt centers are distorted octahedral and the Me₂bpa and bpa with three nitrogen donors exhibit mer- (2, 3, and 7) and fac-form (4 and 6). The coordination mode of nitrite depends on the cobalt oxidation state, to Co^II through the oxygen (nitrito coordination, O- and O,O-coordination) and to Co^III through nitrogen (nitro coordination, N-coordination mode). These findings are consistent with the results of their IR spectra, except that another oxygen of the O-coordinated nitrito group in 3 might interact weakly with Co^II according to its IR spectrum. Reductions of the nitrite in 2, 3, 4, and 5 to nitrogen monoxide were not accelerated in the presence of proton, perhaps due to the nitrito coordination in these Co^II complexes.     

Inhibition of Na+, K+-ATPase in the presence of crown ethers: modulation of ionic composition or pharmacological effects

It is believed that the biological effects of chelating agents such as crown ethers are largely related to their ability to form complexes with ions and/or to facilitate ion transport across membranes. Specific influences are rarely related. Here we present the evidence that even one of the simplest representatives of the crown ether super-family, 1,4,7,10,13,16-hexaoxacyclooctane (18-crown-6), is able to affect the activity of Na⁺, K⁺-ATPase directly. Using nonlinear regression fitting to kinetic data we have found that the crown ether diminishes the apparent Michaelis constant, K _m , and the maximal rate of ATP hydrolysis, V _m , acting as noncompetitive inhibitors. The apparent dissociation constants, K _i , for the crown interaction with the free ATPase and with the enzyme-substrate complex were established to be of 77 ± 3 mM and 21 ± 2 mM, respectively. So 18-crown-6 possesses weak but “direct” pharmacological activity on Na⁺, K⁺-ATPase hinders the formation of enzyme–substrate complex and detains the enzyme in this state.     

Formation of dihydroperoxide derivatives during the oxidation of cyclohexene and tetralin by dioxygen

¹H- and¹³C-NMR investigations revealed that prolonged oxidation of unsubstituted cyclohexene and tetralin, containing symmetrical and weak allylic and benzylic CH bonds, results in the formation of both mono- and dihydroperoxo derivatives.