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1.
The rate of oxidation of the long-wavelength cytochrome b ( b566) on addition of oligomycin to ATP-supplemented anaerobic rat-liver mitochondria was strongly inhibited when 2H 2O was substituted for medium water. This effect was dependent on added substrate, was reversed by uncoupling agents, and was absent in sub-mitochondrial particles. At the same phosphate potential, b566 reduction was favoured in 2H 2O in comparison with H 2O medium. The redox state of b566 may be controlled by the phosphate potential via an intramembrane acid-base equilibrium which is shifted by 2H 2O. 相似文献
2.
We have succeeded in growing Saccharomyces cerevisiae (baker's yeast) on media containing 2H 2O and isolating the core histones highly deuterated in the non-exchangeable positions. The deuterated histones obtained here are of great value for their possible widespread use for structural studies of chromatin. 相似文献
3.
The involvement of OH bond breaking in the 4 dark reactions of the Kok scheme of photosynthetic oxygen evolution was investigated using Chlorella and spinach chloroplasts. When the photosynthetic material was suspended in a 2H 2O based medium, the reaction rates in all 4 cases were only slightly reduced as compared to the rates observed in an H 2O based medium. This was evidence that these rate processes were probably not limited by the breaking of an OH bond. Observations were also made on the yields of O 2 from dark adapted Chlorella subjected to a sequence of brief saturating light flashes. The oscillating flash yield sequence observed with algae suspended in 2H 2O showed greater damping of the oscillations than when the algae were suspended in H 2O. A computer fit of the Kok model to these results revealed a slightly higher proportion of misses, (i.e. absorbed quanta that do not drive photochemistry) in the 2H 2O case. 相似文献
4.
2H 2O (99.8%) Ringer's solution greatly reduces the twitch and tetanus of frog sartorius muscle and, as specially shown here, slows the onset features of the mechanical output of the twitch by: (a) increasing the time ( LR) from stimulus to start of latency relaxation; (b) slowing the developmet of the latency relaxation, and (c) greatly decreasing the rate of onset of tension development. These changes reflect effects of 2H 2O on excitation-contraction coupling and they represent the critical direct effects of 2H 2O on muscle since it does not depress either the action potential or the intrinsic myofibrillar contractility. The increase in LR is attributed to slowed inward electrical propagation in the T-tubule. But the critical effect of 2H 2O on frog muscle is to greatly depress mobilization of activator Ca 2+. The depression of the Ca 2+ mobilization and of its effects on the activation of contraction evidently result from (a) a lowered rate of release of Ca 2+ from the sarcoplasmic reticulum, as indicated by the slowed development of the latency relaxation, (b) a decreased amount of Ca 2+ released in a twitch, and (c) a reduced speed of diffusion of the Ca 2+ to the contractile filaments. The depressed mobilization of Ca 2+ is apparently the essential cause of 2H 2O's general depression of twitch and tetanus output. 相似文献
5.
Arrhenius parameters for formation and decay of phototransients in suspensions of purple membrane fragments in H 2O and 2H 2O have been determined in the temperature range 0–60 °C. Kinetic isotope effects are found which show that proton transfer steps are involved in both formation and decay of the two longest-lived transients absorbing at 410 nm and 660 nm, respectively. The results also suggest that these transients do not occupy a single pathway in the spontaneous deexcitation of bacteriorhodopsin within the purple membrane. Purple membrane undergoes a phase transition at 25–30 °C in both H 2O and 2H 2O. 相似文献
6.
Small-angle neutron scattering experiments were performed in dilute aqueous solutions of chloroplast F 1-ATPase. By contrast variation in 1H 2O/ 2H 2O mixtures and when using different concentrations of glycerol in 2H 2O, structural information on the spatial distribution of dry protein and water was obtained. The maximum distance within latent and active CF 1 was 12 nm. the shape of CF 1 was globular. The total volume of CF 1 was 900 nm 3, and its dry volume (excluding the volume of one water molecule per two exchangeable hydrogen atoms) was 400 nm 3. A volume of 670 nm 3 was inaccessible to glycerol at low glycerol concentrations (less than 25%). At higher concentrations (up to 50%) a volume of 460 nm 3 was excluded to glycerol. Within the resolution of our experiment (1.6 nm) there was no evidence for particular water-rich regions or of secluded water spaces or any particular places for glycerol exchange. Upon thiol activation of the latent enzyme only small changes in structure were detectable just at the limits of the experimental error. They suggest an enhancement of the surface roughness. 相似文献
7.
In on-going studies of ‘classical’ and ring B-unsaturated oestrogens in equine pregnancy, the products of metabolism of [2,2,4,6,6- 2H 5]-testosterone and [16,16,17- 2H 3]-5,7-androstadiene-3β,17β-diol with equine placental subcellular preparations and allantochorionic villi have been identified. Using mixtures of unlabelled and [ 2H]-labelled steroid substrates has allowed the unequivocal identification of metabolites by twin-ion monitoring in gas chromatography–mass spectrometry (GC–MS). Two types of incubation were used: (i) static in vitro and (ii) dynamic in vitro. The latter involved the use of the Oxycell™ cartridge (Integra Bioscience Systems, St Albans, UK) whereby the tissue preparation was continuously supplied with supporting medium plus appropriate cofactors in the presence of uniform oxygenation. [ 2H 5]-Testosterone was converted into [ 2H 4]-oestradiol-17β, [ 2H 4]-oestrone and [ 2H 3]-6-dehydro-oestradiol-17 in both placental and chorionic villi preparations, but to a greater extent in the latter, confirming the importance of the chorionic villi in oestrogen production in the horse. On the basis of GC–MS characteristics (M+ m/z 477/482 (as O-methyl oxime-trimethyl silyl ether), evidence for 19-hydroxylation of testosterone was found in static incubations, while the presence of a 6-hydroxy-oestradiol-17 was recorded in dynamic incubations (twin peaks in the mass spectrum at m/z 504/507, the molecular ion M+). It was not possible to determine the configuration at C-6. The formation of small, but significant, quantities of [2H4]-17β-dihydroequilin was also shown, and a biosynthetic pathway is proposed. In static incubations of placental microsomal fractions, the 17β-dihydro forms of both equilin and equilenin were shown to be major metabolites of [2H3]-5,7-androstadiene-3,17-diol. Using static incubations of chorionic villi, the deuterated substrate was converted into the 17β-dihydro forms of both equilin and equilenin, together with an unidentified metabolite (base peak, m/z 504/506). The isomeric 17-dihydroequilins were also obtained using the dynamic in vitro incubation of equine chorionic villi, together with the 17β-isomer of dihydroequilenin. Confirmation of the identity of 17β-dihydroequilin and 17β-dihydroequilenin was obtained by co-injection of the authentic unlabelled steroids with the phenolic fraction obtained from various incubations. Increases in the peak areas for the non-deuterated steroids (ions at m/z 414 (17β-dihydroequilin) and 412 (17β-dihydroequilenin) (both as bis-trimethyl silyl ether derivatives) were observed. Biosynthetic pathways for formation of the ring B-unsaturated oestrogens from 5,7-androstadiene-3β,17β-diol are proposed. 相似文献
8.
碳(CO 2、CH 4)、氮(N 2O)和水汽(H 2O)等温室气体的交换通量是生态系统物质循环的核心, 是地圈-生物圈-大气圈相互作用的纽带。稳定同位素光谱和质谱技术和方法的进步使碳稳定同位素比值( δ 13C)和氧稳定同位素比值( δ 18O)(CO 2)、 δ 13C (CH 4)、氮稳定同位素比值( δ 15N)和 δ 18O (N 2O)、氢稳定同位素比值( δD)和 δ 18O (H 2O)的观测成为可能, 与箱式通量观测技术和方法结合可以实现土壤、植物乃至生态系统尺度温室气体及其同位素通量观测研究。该综述以CO 2及其 δ 13C通量的箱式观测技术和方法为例, 概述了箱式通量观测系统的基本原理及分类, 阐述了系统设计的理论要求和假设, 综述了从野外到室内土壤、植物叶-茎-根以及生态系统尺度箱式通量观测研究的应用进展及问题, 展望了气体分析精度和准确度、观测数据精度和准确度以及观测数据的代表性评价在箱式通量观测研究中的重要性。 相似文献
9.
The syntheses and structures of [Ni(H 2O) 6] 2+[MF 6] 2− (M = Ti,Zr,Hf) and Ni 3(py) 12F 6·7H 2O are reported. The former three compounds are isostructural, crystallizing in the trigonal space group
(No. 148) with Z = 3. The lattice parameters are a = 9.489(4), C = 9.764(7) Å, with V = 761(1) Å 3 for Ti; a = 9.727(2), C = 10.051(3) Å, with V = 823.6(6) Å 3 for Zr; and a = 9.724(3), C = 10.028(4)Å, with V = 821.2(8)Å 3 for Hf. The structures consist of discrete [Ni(H 2O) 6] 2+ and [MF 6] 2− octahedra joined by O---HF hydrogen bond Large single crystals were grown in an aqueous hydrofluoric acid solution. Ni 3(py) 12F 6·7H 2O crystallizes in the monoclinic space group I2/ a (No. 15) with Z = 4. The lattice parameters are a = 16.117(4), B = 8.529(3), C = 46.220(7) Å, β = 92.46(2)°, and V = 6348(5) Å 3. The structure consists of discrete Ni(py) 4F 2 octahedra linked through H---O---HF and H---O---HO hydrogen bonding interactions. Single c were grown from a (HF) x·pyridine/pyridine/water solution. 相似文献
10.
Amino acid side chains play fundamental roles in stabilising protein structures and in catalysing enzymatic reactions. These fields are increasingly investigated by infrared spectroscopy at the molecular level. To help the interpretation of the spectra, a review of the infrared absorption of amino acid side chains in H 2O and 2H 2O is given. The spectral region of 2600–900 cm −1 is covered. 相似文献
11.
The positive ion electrospray mass spectrometry (ESI-MS) of trans-[Ru(NO)Cl)(dpaH) 2]Cl 2 (dpaH=2,2′-dipyridylamine), obtained from the carrier solvent of H 2O–CH 3OH (50:50), revealed 1+ ions of the formulas [Ru II(NO +)Cl(dpaH)(dpa)] + ( m/ z=508), [Ru IIICl(dpaH)(dpa −)] + ( m/ z=478), [Ru II(NO +)(dpa) 2] + ( m/ z=472), [Ru III(dpa) 2] + ( m/ z=442), originating from proton dissociation from the parent [Ru II(NO +)Cl(dpaH) 2] 2+ ion with subsequent loss of NO (17.4% of dissociative events) or loss of HCl (82.6% of dissociative events). Further loss of NO from the m/ z=472 fragment yields the m/ z=442 fragment. Thus, ionization of the NH moiety of dpaH is a significant factor in controlling the net ionic charge in the gas phase, and allowing preferential dissociation of HCl in the fragmentation processes. With NaCl added, an ion pair, {Na[Ru II(NO)Cl(dpa) 2]} + ( m/ z=530; 532), is detectable. All these positive mass peaks that contain Ru carry a signature ‘handprint’ of adjacent m/ z peaks due to the isotopic distribution of 104Ru, 102Ru, 101Ru, 99Ru, 98Ru and 96Ru mass centered around 101Ru for each fragment, and have been matched to the theoretical isotopic distribution for each set of peaks centered on the main isotope peak. When the starting complex is allowed to undergo aquation for two weeks in H 2O, loss of the axial Cl − is shown by the approximately 77% attenuation of the [Ru II(NO +)Cl(dpaH)(dpa)] + ion, being replaced by the [Ru II(NO +)(H 2O)(dpa) 2] + ( m/ z=490) as the most abundant high-mass species. Loss of H 2O is observed to form [Ru II(NO +)(dpa) 2] + ( m/ z=472). No positive ion mass spectral peaks were observed for RuCl 3(NO)(H 2O) 2, ‘caged NO’. Negative ions were observed by proton dissociation forming [Ru II(NO)Cl 3(H 2O)(OH)] − in the ionization chamber, detecting the parent 1− ion at m/ z=274, followed by the loss of NO as the main dissociative pathway that produces [Ru IIICl 3(H 2O)(OH)] − ( m/ z=244). This species undergoes reductive elimination of a chlorine atom, forming [Ru IICl 2(H 2O)(OH)] − ( m/ z=208). The ease of the NO dissociation is increased for the negative ions, which should be more able to stabilize a Ru III product upon NO loss. 相似文献
12.
The molecular structure of the title complexes [Fe(H 2O) 4][Fe(Hedta)(H 2O)] 2 · 4H 2O (I) and [Fe(H[ 2edta)(H 2O)] · 2H 2O (II) have been determined by single-crystal X-ray analyses. The crystal data are as follows: I: monoclinic, P2 1/ n, A = 11.794(2), B = 15.990(2), C = 9.206(2) Å, β = 90.33(1)°, V = 1736.1(5) Å 3, Z = 2 and R = 0.030; II: monoclinic, C2/ c, A = 11.074(2), B = 9.856(2), C = 14.399(2) Å, β = 95.86(1)°, V = 1563.3(4) Å 3, Z = 4 and R = 0.025. I is found to be isomorphous with the Mn II analog reported earlier and to contain a seven-coordinate and approximately pentagonal-bipyramidal (PB) [Fe II(Hedta)(H 2O] − unit in which Hedta acts as a hexadentate ligand. The [Fe II(H 2edta)(H 2O)] unit in II has also a seven-coordinate PB structure with the two protonated equatorial glycine arms both remaining coordinated, and thus bears a structural resemblance to the seven-coordinate [Co II(H 2edta)(H 2O)] reported previously. 相似文献
13.
Estrogens have an important role in the growth of breast and other hormone-sensitive cancers. We have shown that 4-hydroxyandrostenedione (4-OHA) selectively blocks estrogen synthesis by inhibiting aromatase activity in ovarian and peripheral tissues and reduces plasma estrogen levels in rat and non-human primate species. In postmenopausal men and women, estrogens are mainly of peripheral origin. When postmenopausal breast cancer patients were administered either by daily oral or parenteral weekly treatment with 4-OHA, plasma estrogen concentrations were significantly reduced. Complete or partial response to treatment occurred in 34% of 100 patients with advanced breast cancer, while the disease was stabilized in 12%. We recently studied the effects of 4-OHA and other aromatase inhibitors, 10-propargylestr-4-ene-3,17-dione (PED) and imidazo[1,5-]3,4,5,6-tetrahydropyrin-6-yl-(4-benzonitrile) (CGS 16949A) as well as 5-reductase inhibitors, N,N-diethyl-4-methyl-3-oxo-4-aza-5-androstane-17β-carboxyamide (4-MA) and 17β-hydroxy-4-aza-4-methyl-19norandrost-5-en-3-one (L651190) in prostatic tissue from 11 patients with prostatic cancer and six patients with benign prostatic hypertrophy (BPH), and from normal men at autopsy. We attempted to measure aromatase activity in tissue incubation by quantitating 3H 2O released during aromatization of androstenedione or testosterone labeled at the C-1 position. The amount of 3H 2O released from all samples was at least twice that of the heat inactivated tissue samples. The 3H 2O release was significantly inhibited by 4-OHA and 4-MA, but not by the other aromatase inhibitors. However, when HPLC and TLC were used to isolate steroid products, no estrone or estradiol was detected in the incubates. Furthermore, no aromatase mRNA was detected following amplification by PCR. The 4-OHA was found to inhibit 5-reductase in both BPH and cancer tissue, although to a lesser extent than 4-MA. The other aromatase inhibitors were without effect. Although a mechanism involving intraprostatic aromatase is not likely, inhibitors may act to reduce peripherally-formed estrogens. In postmenopausal breast cancer, the results indicate that 4-OHA is of significant benefit. 相似文献
14.
The modulated polarographic technique of O 2 detection was applied to Chlorella to study the rate-limiting thermal reaction between Photosystem II and O 2 evolution. From an analysis of the operation of the polarograph at different frequencies, it was concluded that a first order thermal reaction of rate constant 305±20 (S.E.) s −1 was consistent with the results of 22 °C. When the algae were successively studied in solutions made up with 2H 2O and H 2O, a kinetic isotopic effect for the rate constant of 1.29±0.05 (S.E.) was found. This suggests that the rate limiting step does not involve the breaking of the O-H bond in water. A temperature study of the rate constant indicated an activation energy of 5.9±0.5 (S.E.) kcal·mole −1 and an entropy of activation of −25 cal·degree −1·mole −1. The linearity of the Arrhenius plot between 8 and 42 °C demonstrated that only one reaction was rate-limiting over this temperature range. 相似文献
15.
The pentose phosphate pathway operates at an elevated level in rat kidney following induction of diabetes and in the compensatory hypertrophy following unilateral nephrectomy in control and alloxan-diabetic rats, as shown by the yields of 14Co 2 from [1- 14C]glucose, [6- 14C]glucose and 3H 2O yields from [2- 3H]glucose. The elevated flux through the pentose phosphate pathway is correlated with the increased RNA content and weight of the kidney. The direct utilization of NADPH for reductive synthetic reactions and the potential for indirect utilization via the sorbitol route and the linked transhydrogenase reactions of the glucuronate-xylulose pathway, for NADH and ATP generation, are also discussed. 相似文献
16.
Five heterometallic compounds with formulae [Ba(H 2O) 4Cr 2(μ-OH) 2( nta) 2] · 3H 2O (I), [M( bpy) 2(H 2O) 2] [Cr 2(OH) 2( nta) 2] · 7H 2O, where M 2+ = Zn, (II); Ni, (III); Co, (IV) and [Mn(H 2O) 3( bpy)Cr 2(OH) 2( nta) 2] · ( bpy) · 5H 2O (V); bpy = 2,2′-bipyridine, ( nta = nitrilotriacetate ion) have been prepared by reaction of I with the corresponding M II-sulfates in the presence of 2,2′-bipyridine. Substances I–V have been characterized by magnetic susceptibility measurements, EPR and X-ray determinations. I represents a 2D coordination polymer formed by coordination of centrosymmetrical dimeric chromium(III) units and Barium cations. The 10-coordinate Ba polyhedron is completed by four water molecules. Compounds II–IV are isostructural and consist of non-centrosymmetric dimeric anions [Cr 2(μ-OH) 2( nta) 2] 2−, complex cations [M II( bpy) 2(H 2O) 2] 2+ and solvate water molecules. The octahedral coordination of chromium atoms implies four donor atoms of the nta3− ligands and two bridging OH groups. Multiple hydrogen bonds of coordinated and solvate water molecules link anions and cations in a 3D network. A similar [Cr 2(μ-OH) 2( nta) 2] 2− unit is found in V. The bridging function is performed by a carboxylate oxygen atom of the nta ligand that leads to the formation of a trinuclear complex [Mn( bpy)(H 2O) 2Cr 2(μ-OH) 2( nta) 2]. Experimental and calculated frequency and temperature dependences of EPR spectra of these compounds are presented. The fine structure appearing on the EPR spectra of compound V is analyzed in detail at different temperatures. It is established that the main part of the EPR signals is due to the transitions in the spin states of a spin multiplet with S = 2. Analyses of experimental and calculated spectra confirm the absence of interaction between metal ions (M II) and Cr-dimers in complexes III and IV and the presence of weak Mn–Cr interactions in V. The temperature dependence of magnetic susceptibilities for I–V was fitted on the basis of the expression derived from isotropic Hamiltonian including a bi-quadratic exchange term. 相似文献
17.
Cobalt(III) complexes with a thiolate or thioether ligand, t-[Co(mp)(tren)] + (2), t-[Co(mtp)(tren)] 2+ (1Me) and t-[Co(mta)(tren)] 2+ (2Me), (mp = 3-mercaptopropionate, MA = 3-(methylthio)propionate and MTA = 2-(methylthio)acetate) have been prepared in aqueous solutions. The crystal structures of 1, 2, 1Me and 2Me were determined by X-ray diffraction methods. The crystal data are as follows, t-[Co(mp)(tren)]ClO 4 (1CIO 4): monoclinic, P2 1/ n, A = 10.877(8), B = 11.570(4), c = 12.173(7) Å, β = 92.20(5)°, V = 1531(1) Å 3, Z = 4 and R = 0.060; t-[Co(ma)(tren)]Cl·3H 2O (2Cl·3H 2O): monoclinic, P2 1/ n, a = 7.7688(8), B = 27.128(2), C = 7.858(1) Å, β = 100.63(1)°, V = 1627.7(3) Å 3, Z = 4 and R = 0.066; (+) 465CD- t-[ Co( mtp)( tren)]( ClO4) 2 ((+) 465CD-1Me(ClO 4) 2): orthorhombic, P2 12 12 1, A = 10.6610(7), B = 11.746(1), C = 15.555(1) Å, V = 1947.9(3) Å 3, Z = 4 and R = 0.068; (+) 465CD- t-[Co(mta)(tren)](ClO 4) 2 ((+) 465CD-2Me(ClO 4) 2): orthorhombic, P2 12 12 1, a = 10.564(1), B = 11.375(1), C = 15.434(2) Å, V = 1854.7(4) Å 3, Z = 4 and R = 0.047. All central Co(III) atoms have approximately octahedral geometry, coordinated by four N, one O, and one S atoms. All of the complexes are only isomer, of which the sulfur atom in the didentate-O,S ligands are located at the trans position to the tertiary amine nitrogen atom of tren. 1 and 1Me contain six-membered chelate ring, and 2 and 2Me do five-membered chelate ring in the didentate ligand. The chirality of the asymmetric sulfur donor atom in (+) 465CD-1Me is the S configuration and that in (+) 465CD-2Me is the R one. The 1H NMR, 13C NMR and electronic absorption spectral behaviors and electrochemical properties of the present complexes are discussed in relation to their stereochemistries. 相似文献
18.
稳定同位素红外光谱(IRIS)技术克服了传统的大气CO 2气瓶采样-同位素质谱(IRMS)技术时间分辨率低且耗时费力的缺点, 可以实现高时间分辨率和高精度的大气CO 2碳同位素组成( δ 13C)和氧同位素组成( δ 18O)的原位连续测定。基于IRIS技术测量CO 2 δ 13C和 δ 18O的误差来源主要包括 δ 13C和 δ 18O测量值对CO 2浓度变化的非线性响应(浓度依赖性)以及对环境条件变化的敏感性导致的漂移(时间漂移)。如何有效地校正浓度依赖性和时间漂移导致的误差是IRIS仪器应用的前提。该综述阐述了 δ 13C和 δ 18O测量值的浓度依赖性产生的理论基础, 回顾了浓度依赖性的理论校正和经验方程校正方法和应用; 回顾了时间漂移的校正原理、方法和应用; 概述了数据溯源至国际标准的原理、方法与应用现状。结合实际情况推荐利用3个或3个以上已知CO 2浓度和 δ 13C、 δ 18O真值的CO 2标准气体涵盖待测气体CO 2浓度的浓度依赖性校正, 设置适当的校正频率校正时间漂移并进行数据溯源。指出应该加强不同仪器和校正方法的比对研究; 采用IRIS技术测定CH 4、N 2O和H 2O同位素组成也可以采取类似的校正方法。 相似文献
19.
In this study, 2H and 31P-NMR techniques were used to study the effects of trehalose and glycerol on phase transitions and lipid acyl chain order of membrane systems derived from cells of E. coli unsaturated fatty acid auxotroph strain K1059, which was grown in the presence of [11,11- 2H 2]-oleic acid or [11,11- 2H 2]-elaidic acid. From an analysis of the temperature dependence of the quadrupolar splitting it could be concluded that neither 1 M trehalose or glycerol generally had any significant effect on the temperature of the lamellar gel to liquid-crystalline phase transition. In the case of the oleate-containing hydrated total lipid extract, glycerol but not trehalose caused a 5°C increase of this transition temperature. In general, both cryoprotectants induced an ordering of the acyl chains in the liquid-crystalline state. Trehalose and glycerol both decrease the bilayer to non-bilayer transition temperature of the hydrated lipid extract of oleate-grown cells by about 5°C, but only trehalose in addition induces an isotropic to hexagonal ( HII) phase transition. In the biological membranes, trehalose and not glycerol destabilised the lipid bilayer, and in the case of the E. coli spheroplasts, part of the induced non-bilayer structures is ascribed to a hexagonal ( HII) phase in analogy with the total lipids. Interestingly, 1 mM Mg 2+ was a prerequisite for the destabilisation of the lipid bilayer. In the hydrated total lipid extract of E. coli grown on the more ordered elaidic acid, both transition temperatures were shifted about 20°C upwards compared with the oleate-containing lipid, but the effect of trehalose on the lipid phase behaviour was similar. The bilayer destabilising ability of trehalose might have implications for the possible protection of biological systems by (cryo-)protectants during dehydration, in that protection is unlikely to be caused by preventing the occurrence of polymorphic phase transitions. 相似文献
20.
A series of diplatinum(III) complexes derived from cis-(NH 3) 2Pt II and the model nucleobase 1-methylcytosine (1-MeC) has been prepared and X-ray structurally characterized, all of which contain two anionic base ligands (1-MeC −) in a head–tail ( ht) arrangement: ht- cis-[( ONO 2)(NH 3) 2Pt(1-MeC −- N3, N4) 2Pt(NH 3) 2( ONO 2)](NO 3) 2·HNO 3·3H 2O (2b), ht- cis-[( NO 2) (NH 3) 2 Pt(1-MeC −- N3, N4) 2Pt(NH 3) 2( OH 2)](ClO 4) 3·3.5H 2O (3), ht- cis-[( OH 2)(NH 3) 2Pt(1-MeC −- N3, N4) 2Pt(NH 3) 2( OH 2)](ClO 4) 4·H 2O (4b), and ht- cis-[(9-EtGH- N7)(NH 3) 2Pt(1-MeC −- N3, N4) 2Pt (NH 3) 2(9-EtGH- N7)](NO 3) 4·9H 2O (7b) (9-EtGH=9-ethylguanine). Several other compounds, differing in the nature of the axial ligands, have been isolated and or observed in solution by 1H and 195Pt NMR spectroscopy. The chemistry of these diplatinum(III) compounds is dominated by facile substitution reactions of the axial ligands. Of particular interest in this context is the ready reaction of 2b or 3 with guanine nucleobases. Since similar compounds are not obtained with any of the other common nucleobases, 2b and 3 can be considered guanine-specific chemical probes. 相似文献
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