共查询到20条相似文献,搜索用时 15 毫秒
1.
Hani Atamna Patrick B Walter Bruce N Ames 《Archives of biochemistry and biophysics》2002,397(2):345-353
Mitochondria decay with age from oxidative damage and loss of protective mechanisms. Resistance, repair, and replacement mechanisms are essential for mitochondrial preservation and maintenance. Iron plays an essential role in the maintenance of mitochondria, through its two major functional forms: heme and iron-sulfur clusters. Both iron-based cofactors are formed and utilized in the mitochondria and then distributed throughout the cell. This is an important function of mitochondria that is not directly related to the production of ATP. Heme and iron-sulfur clusters are important for the normal assembly and for the optimal activity of the electron transfer complexes. Loss of mitochondrial cytochrome c oxidase (complex IV), integrity of mtDNA, and function can result from abnormal homeostasis of iron. We review the physiological role of iron-sulfur clusters and heme in the integrity of the mitochondria and the generation of oxidants. 相似文献
2.
[Ru(H)(CO)(PPh3)2(α/β-NaiR)](ClO4) (3, 4) are synthesized by the reaction of [Ru(H)(Cl)(CO)(PPh3)3] with 1-alkyl-2-(naphthyl-α/β-azo)imidazole (α-NaiR (3); β-NaiR (4)). One of the complexes [Ru(H)(CO)(PPh3)2(α-NaiMe)](ClO4) (3a) has been structurally established by X-ray diffraction study. Upon addition of Cl2 saturated in MeCN to 3 or 4 gives [Ru(Cl)(CO)(α/β-NaiR)(PPh3)2](ClO4) (for α-NaiR (5); β-NaiR (6)), without affecting metal oxidation state, which were characterized by spectroscopic measurements. The redox property of the complexes is examined by cyclic voltammetry. 相似文献
3.
We report the synthesis of phosphorescent divalent osmium complexes of the form [Os(N-N)2(L-L) or Os(L-L)2(N-N)]2+ (PF6)2 where N-N is a derivative of 1,10-phenanthroline, and L-L is a diarsine or diphosphine ligand: 1,2-bis(dimethylphosphino)ethane, 1,2-bis(dicyclohexylphosphino)ethane, or 1,2-bis(dimethylarseno)benzene. X-ray structures have been determined, luminescent and electrochemical properties have been measured and DFT calculations have been performed on the complexes. The emission lifetime of complexes of structure Os(II)(L-L)2(N-N) are longer than the those of Os(II)(N-N)2(L-L). The DFT calculations show that there is significant mixing of the π−π∗ into the dπ−π∗ charge-transfer state for the complexes of the form Os(II)(L-L)2(N-N) resulting in a longer lived excited state. Through DFT calculations we were able to conclude that the HOMO of the complexes is a d orbital on the osmium while the LUMO is the b1(ψ) π∗ system of the phenanthroline. However, we found that the HOMO did not have the correct symmetry to enable strong charge transfer to the phenanthroline to be observed, and the strong MLCT transition observed in the spectra is the metal d HOMO(−1) to the b1 π∗ LUMO of the phenanthroline. 相似文献
4.
Annalese F. Maddox Arnold L. Rheingold W. Scott Kassel 《Inorganica chimica acta》2008,361(11):3283-3293
The oxidative electrochemistry of chiral, bidentate ferrocenylphosphines, five Taniaphos and seven Walphos ligands, was studied in methylene chloride. In general, two waves of varying reversibility were observed. Complexes of the general type [(phosphine)MCl2] (phosphine = Taniaphos or Walphos; M = Pd or Pt) were prepared and characterized by NMR. Upon coordination, the oxidative electrochemistry of the ligands was greatly simplified. The X-ray structures of a Taniaphos platinum complex as well as a palladium and a platinum complex with a Walphos ligand were determined. 相似文献
5.
S. Jarrett Howell 《Inorganica chimica acta》2005,358(13):3711-3723
A series of new thiophene amides containing a pyridine ring has been synthesized and characterized. Single crystal X-ray structures have been determined for four of the new substances which show two distinct patterns of hydrogen-bonding. The crystal structure of the copper (II) complex of one of the ligands shows that the bonding is O,N in a square planar geometry with perchlorate ions in the axial positions. The new compounds do not undergo electropolymerization due to primary oxidation of the amide function but tuning of the amide group by introduction of an electron-withdrawing group on the pyridine ring allows electropolymerization to occur. 相似文献
6.
Chihiro Kachi-TerajimaHitoshi Miyasaka Tomohiko IshiiKen-ichi Sugiura Masahiro Yamashita 《Inorganica chimica acta》2002,332(1):210-215
The ligand substitution reaction of Ru2(O2CCH3)4Cl with 2-amino-4,6-dimethylpyrimidine (Hadmpym) under gentle refluxing conditions in methanol led to the formation of a bridging-ligand mono-substituted compound, [Ru2(O2CCH3)3(admpym)(Cl)(MeOH)] (1). Compound 1 crystallized in monoclinic space group P21/n (no. 14) with a=8.3074(8) Å, b=12.3722(8) Å, c=18.913(1) Å, β=95.559(3)°, V=1934.8(3) Å3, and Z=4. Temperature dependence of the magnetic susceptibility of 1 revealed it to be in a spin ground state S=3/2 arising from the electronic configuration of σ2π4δ2(δ*π*)3. Compound 1 undergoes three metal-centered redox reactions in electrochemistry: E1/2 (ox)=+0.72 V (Ia/Ic<1, ΔEp=0.17 V); E1/2 (1,red)=−0.65 V (Ia/Ic≈1, ΔEp=0.10 V); and E1/2 (2,red)=−1.80 V (Ia/Ic?1, ΔEp=0.16 V). Then, the redox species produced by electrolysis were characterized by spectroscopic studies. 相似文献
7.
The genetic basis of Haldane's rule was investigated through estimating the accumulation of hybrid incompatibilities between Drosophila simulans and D. mauritiana by means of introgression. The accumulation of hybrid male sterility (HMS) is at least 10 times greater than that of hybrid female sterility (HFS) or hybrid lethality (HL). The degree of dominance for HMS and HL in a pure D. simulans background is estimated as 0.23-0.29 and 0.33-0.39, respectively; that for HL in an F1 background is unlikely to be very small. Evidence obtained here was used to test the Turelli-Orr model of Haldane's rule. Composite causes, especially, faster-male evolution and recessive hybrid incompatibilities, underlie Haldane's rule in heterogametic male taxa such as Drosophila (XY male and XX female). However, if faster-male evolution is driven by sexual selection, it contradicts Haldane's rule for sterility in heterogametic-female taxa such as Lepidoptera (ZW female and ZZ male). The hypothesis of a faster-heterogametic-sex evolution seems to fit the current data best. This hypothesis states that gametogenesis in the heterogametic sex, instead of in males per se, evolves much faster than in the homogametic sex, in part because of sex-ratio selection. This hypothesis not only explains Haldane's rule in a simple way, but also suggests that genomic conflicts play a major role in evolution and speciation. 相似文献
8.
A previous review summarized research prior to 2004 carried out on the bioactive host-defense peptides contained in the skin secretions of Australian anurans (frogs and toads). This review covers the extension of that research from 2004 to 2012, and includes membrane-active peptides (including antibacterial, anticancer, antifungal and antiviral peptides) together with the mechanisms by which these peptides interact with model membranes, peptides that may be classified as "neuropeptides" (including smooth muscle active peptides, opioids and immunomodulators) and peptides which inhibit the formation of nitric oxide from neuronal nitric oxide synthase. The review discusses the outcome of cDNA sequencing of signal-spacer-active peptides from an evolutionary viewpoint, and also lists those peptides for which activities have not been found to this time. 相似文献
9.
Evolutionary geneticists have increasingly used sequence variation in mitochondrial DNA (mtDNA) as a source of historical
information. However, conclusions based on these data remain tentative because a sufficiently clear understanding of the evolutionary
dynamics of mtDNA has yet to be developed. In this paper we present the results of computer simulations designed to illustrate
the effects of social structure, geographical structure, and population size on the rate of nucleotide substitution and lineage
sorting of mtDNA. The model is based in part on the social structure of macaque monkeys. Simulated populations of females
were divided into 25 social groups; the animals in each were distributed in a hierarchy of four dominance rank categories.
The probabilities for offspring survivorship were varied among dominance ranks to reflect the fitness consequences of social
structure. Population size was varied across runs from 100 to 300 females. The pattern of female migration was also varied
to mimic either the island model or the stepping-stone model. All these variables are shown to affect the lineage sorting
period (LSP), and certain combinations of parameter values can cause the retention of mtDNA polymorphisms for a very long
time. In addition, the simulations exhibited a negative relationship between the LSP and substitution rate over a modest and
realistic range of LSP values. An important implication of these results is that estimates of time since isolation based on
the assumption of a constant molecular clock may be biased and unreliable. 相似文献
10.
Fabio Carniato Giuliana Gervasio Enrico Sappa Andrea Secco 《Inorganica chimica acta》2010,363(8):1773-1778
The reactions of the complexes Fe3(CO)12, H2FeRu3(CO)13, H2Ru4(CO)13 and CpNiRu3(H)3(CO)9 with 2(diphenylphosphino)ethyl-triethoxysilane give considerable yields of the complexes Fe3(CO)10L2 (1), H2FeRu3(CO)10L2 (2), Ru4(CO)10L3 (3) and CpNiRu3(H)3(CO)7L2 (4) where L = Ph2PCH2CH2Si(OEt)3. The complexes (1-3) have been characterized by analytical and spectroscopic techniques. The structure of (4) has been determined by X-ray analysis. The presence of a phosphine containing the -Si(OEt)3 group has been exploited for grafting complexes (3) and (4) on the mesoporous SBA-15 and the resulting inorganic-organometallic materials have been characterized by means of ICP-MS, FT-IR, DR-UV-vis spectroscopy, XRD and textural analysis. 相似文献
11.
T. B. Wang M. Niizeki T. Harada R. Ishikawa Y. Q. Qian K. Saito 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1993,86(2-3):371-376
Summary Somatic hybrid cell lines were constructed by the fusion of protoplasts isolated from cell suspensions of Zea mays L. (maize, 2n = 20) and Triticum sect, trititrigia MacKey (trititrigia, 2n = 35), a perennial hybrid of T. durum Desf. and Elytrigia intermedium (Host) Nevski. Iodoacetamide-inactivated protoplasts of maize were fused with trititrigia protoplasts, which were sensitive to the PEG/DMSO fusion treatment at high pH and high calcium. Based on physiological complementation, approximately 0.002% of the total protoplasts cultured following fusion treatment developed into cell colonies, and 79 lines of them, almost a half, were singled out and subcultured. Among the subcultured lines three were, in comparison with the parents, identified as somatic hybrids by their coupled XbaI restriction patterns of total DNAs probed with the ribosomal DNA of rice. Southern analysis of the digested total DNAs with a mitochondrial gene, atpA., from pea, or a chloroplast gene, trnK, from rice, revealed that all the hybrids carried only the organellar DNAs of trititrigia, which excluded the possibilities of a chimeric callus or any DNA contamination. Cytogenetically, one hybrid was mixoploid with a 2n of 46–67 in which chromosomal endoreduplication, characterized by the appearance of diplochromosomes, was occasionally observed. Its hybridity was reconfirmed by the fact that it bore the satellite chromosomes of both maize and trititrigia, which were distinguishable from each other by size. In contrast, the other two hybrids were aneuploids. The potential of gene transfer between Zea and Triticum species was thus conclusively established. 相似文献
12.
RNA--protein interactions in the ribosome. IV. Structure and properties of binding sites for proteins S4, S16/S17 and S20 in the 16S RNA 总被引:3,自引:0,他引:3
Proteins S4, S16/S17 and S20 of the 30 S ribosomal subunit of Escherichia coli+ associate with specific binding sites in the 16 S ribosomal RNA. A systematic investigation of the co-operative interactions that occur when two or more of these proteins simultaneously attach to the 16 S RNA indicate that their binding sites lie near to one another. The binding site for S4 has previously been located within a 550-nucleotide RNA fragment of approximately 9 S that arises from the 5′-terminal portion of the 16 S RNA upon limited hydrolysis with pancreatic ribonuclease. The 9 S RNA was unable to associate with S20 and S16/S17, however, either alone or in combination. A fragment of similar size and nucleotide sequence, termed the 9 S1 RNA, has been isolated following ribonuclease digestion of the complex of 16 S RNA with S20 and S16/S17. The 9 S1 RNA bound not only S4, but S20 and S16/S17 as well, although the fragment complex was stable only when both of the latter protein fractions were present together. Nonetheless, measurements of binding stoichiometry demonstrated the interactions to be specific under these conditions. A comparison of the 9 S and 9 S1 RNAs by electrophoresis in polyacrylamide gels containing urea revealed that the two fragments differ substantially in the number and distribution of hidden breaks. Contrary to expectation, the RNA in the ribonucleoprotein complex appeared to be more accessible to ribonuclease than the free 16 S RNA as judged by the smaller average length of the sub-fragments recovered from the 9 S1 RNA. These results suggest that the binding of S4, S16/S17 and S20 brings about a conformational alteration within the 5′ third of the 16 S RNA.To delineate further the portions of the RNA chain that interact with S4, S16/S17 and S20, specific fragments encompassing subsequences from the 5′ third of the 16 S RNA were sought. Two such fragments, designated 12 S-I and 12 S-II, were purified by polyacrylamide gel electrophoresis from partial T1 ribonuclease digests of the 16 S RNA. The two RNAs, which contain 290 and 210 nucleotides, respectively, are contiguous and together span the entire 5′-terminal 500 residues of the 16 S RNA molecule. When tested individually, neither 12 S-I nor 12 S-II bound S4, S16/S17 or S20. If heated together at 40 °C in the presence of Mg2+ ions, however, the two fragments together formed an 8 S complex which associated with S4 alone, with S16/S17 + S20 in combination, and with S4 + S16/S17 + S20 when incubated with an un fractionated mixture of 30 S subunit proteins. These results imply that each fragment contains part of the corresponding binding sites. 相似文献
13.
在我国Bt棉主要以Cry1Ab或Cry1Ac为主,其他新型Bt基因未被转入棉花中用来控制害虫,然而大面积种植单价Bt基因的棉花,将可能会大大增加靶标害虫对该类型Bt棉花抗性频率,因此研究其他新型Bt蛋白对靶标害虫的控制作用显得十分必要。采用蛋白混入人工饲料的生物测定方法,在室内测定了6种Bt蛋白对棉铃虫初孵幼虫的毒力,比较了浓度为1.0μg· g-1时不同Bt蛋白对棉铃虫幼虫生长发育的影响。毒力测定结果表明,不同Bt蛋白对棉铃虫初孵幼虫的毒力不同,LC50值由低到高依次为Cry1Ab 0.065μg· g-1、Cry1Ac 0.074μg· g-1、Cry2Ab 0.133μg· g-1、Cry2Aa 11.670μg· g-1、Cry1Ah 13.010μg· g-1和Cry1Ca>20μg· g-1。生长发育测定结果表明,Cry1Ab和Cry1Ac对棉铃虫幼虫的生长发育影响最大,Cry2Ab次之;Cry1Ah和Cry2Aa对1龄幼虫的校正死亡率和体重抑制率差别不大,但对2龄幼虫的差异较大,Cry1Ah处理2龄幼虫后体重和生长发育参数与Cry2Ab接近,而Cry1Ca对棉铃虫幼虫生长发育几乎没影响。Cry1Ah、Cry2Aa和Cry2Ab的毒力不如Cry1Ac和Cry1Ab,但仍可以作为控制棉铃虫幼虫的替代策略。 相似文献
14.
Root growth characteristics, biomass and nutrient dynamics of seedlings of two larch species raised under different fertilization regimes 总被引:12,自引:0,他引:12
The effects of different fertilization regimes on root growth characteristics, nutrient uptake and biomass production of Japanese larch (Larix kampferi Sarg.) and its hybrid larch (L. gmelinii × L. kampferi) seedlings were examined for one growing season. Seedlings were raised in the greenhouse under three fertilizer levels (10, 20, 40 mg N seedling–1 season–1) and two delivery schedules, conventional (C) and exponential (E) for 12 weeks. Root growth, biomass allocation and nutrient loading capacity of seedlings were measured for a 3-week interval. By the end of growing season, seedlings fertilized with low dose conventionally (10C) and exponentially (10E) developed relatively longer root and larger root surface areas than those fertilized at high dose exponential loading (40E). At final harvest, the 40E treated Japanese larch had 134% and 155% more shoot mass as compared with those raised under 20E and 10E treated seedlings, respectively. The seedlings fertilized under 10C and 10E showed a high root mass ratio, while 40E treated seedlings showed a low root mass ratio. These data indicated that different nutrient levels (10 mg, 20 mg and 40 mg) strongly affected root growth characteristics. The same seasonal dose (10 mg) applied exponentially (10E) accumulated more N in seedlings compared to the 10C treatment. Exponential fertilization enhanced an increase in N concentration of the whole plant suggesting exponential delivery schedule is an efficient fertilization technique for greater nutrient uptake of plants. In contrast, N concentration of whole plant was declined for seedlings treated with conventional fertilization due to growth dilution. Late in the growing season, seedlings raised under 40E did not significantly improved dry mass production of root, but nutrient accumulation increased without a concomitant increased in root dry mass production. The result suggests that seedlings fertilized exponentially at medium and high dose rates (20E and 40E) induced luxury nutrient consumption within the plant. 相似文献
15.
16.
V. Shanthiyaa G. Karthikeyan T. Raguchander 《Archives Of Phytopathology And Plant Protection》2013,46(5):517-528
Chaetomium globosum has been well-known potential antagonist of several seed and soilborne fungus. Eight isolates of C. globosum were obtained from different sources and were identified by morphological characters. C. globosum isolates examined for the presence of extra cellular proteins, cellulases and antifungal metabolites in culture filtrate by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), thin-layer chromatography and high-performance liquid chromatography. Variation in the mycelial protein of C. globosum isolates was noted in the SDS-PAGE analysis. Different C. globosum isolates that showed more number of bands in protein profile was further screened for the production of cellulases in culture filtrate. Cellulase activity of C. globosum isolates revealed that maximum activity was observed in the isolate Cg-6 after 11?days of incubation, while Cg-2 had least activity. C. globosum isolates were tested for antibiotic production, among which three isolates viz. Cg-6, Cg-7 and Cg-5 were found to produce the antibiotic Chaetoglobosin A in the culture filtrate. The antibiotic Chaetoglobosin A appeared blue colour under UV spectrum with a wavelength of 250?nm. 相似文献
17.
Xian-He Bu He LiuMiao Du Keith Man-Chung WongVivian Wing-Wah Yam 《Inorganica chimica acta》2002,333(1):32-40
The complexes of Cu(I), Cu(II), Ni(II), Zn(II) and Co(II) with a new polypyridyl ligand, 2,3-bis(2-pyridyl)-5,8-dimethoxyquinoxaline (L), have been synthesized and characterized. The crystal structures of these complexes have been elucidated by X-ray diffraction analyses and three types of coordination modes for L were found to exist in them. In the dinuclear complex [Cu(I)L(CH3CN)]2·(ClO4)2 (1), L acts as a tridentate ligand with two Cu(I) centers bridged by two L ligands to form a box-like dimeric structure, in which each Cu(I) ion is penta-coordinated with three nitrogen atoms and a methoxyl oxygen atom of two L ligands, and an acetonitrile. In [Cu(II)L(NO3)2]·CH3CN 2, the Cu(II) center is coordinated to the two nitrogen atoms of the two pyridine rings of L which acts as a bidentate ligand. The structures of [Ni(II)L(NO3)(H2O)2]·2CH3CN·NO3 (3), [Zn(II)L(NO3)2 (H2O)]·2CH3CN (4) and [Co(II)LCl2(H2O)] (5) are similar to each other in which L acts as a tridentate ligand by using its half side, and the metal centers are coordinated to a methoxyl oxygen atom and two bipyridine nitrogen atoms of L in the same side. The formation of infinite quasi-one-dimensional chains (1, 4 and 5) or a quasi-two-dimensional sheet (2) assisted by the intra- or intermolecular face-to-face aryl stacking interactions and hydrogen bonds may have stabilized the crystals of these complexes. Luminescence studies showed that 1 exhibits broad, structureless emissions at 420 nm in the solid state and at 450 nm in frozen alcohol frozen glasses at 77 K. Cyclic voltammetric studies of 1 show the presence of an irreversible metal-centered reduction wave at approximately −0.973 V versus Fc+/0 and a quasi-reversible ligand-centered reduction couple at approximately −1.996 V versus Fc+/0. The solution behaviors of these complexes have been further studied by UV-Vis and ESR techniques. 相似文献
18.
During the period from July 1992 to March 1995, suspended particulate matter in Lake Biwa was collected at 1-month intervals,
and the contents of Al, Si, and P were determined. Based on the analytical data, the particulate matter was fractionated by
calculation into three types of particles of different origins: particles of terrigenous origin, particles of diatom origin,
and particles due to microorganisms except for diatoms. The relative abundance of the respective particles was featured in
water depth-time (month) diagrams, with contours in terms of weight per liter of lake water. As a result, the characteristic
distributions of the particles were revealed, and their inherent roles in natural purification were distinguished from each
other. Of the three types of particles, the particles of diatom origin were anticipated to be the principal scavengers not
only of nutritious elements of silicon and phosphorus, but also of various metal ions dissolved in the lake.
Received: October 5, 2000 / Accepted: June 6, 2001 相似文献
19.
Clover seedlings were grown at different nitrogen concentrations (5, 10, 15, 20, 25 mM NO3
−, i.e. N5 to N25) and two irradiances, I (200 and 400 μmol m−2 s−1 of photon flux density, i.e. I
200 and I
400). Net photosynthetic rate (P
N), photosynthetic nitrogen use efficiency (PNUE), leaf chlorophyll (Chl) content, maximum photochemical efficiency (Fv/Fm), and actual photochemical efficiency of photosystem 2 (PS2) (ΦPS2) increased from N5 to N15 and decreased with N15 to N25. P
N, PNUE, and ΦPS2 were higher at I
400 than at I
200, but Fv/Fm and leaf Chl contents at I
400 were lower than at I
200. The effects of the N and I on specific leaf area (SLA) and N contents per unit dry mass (Nm) were similar, the SLA and Nm increased from N5 to N25 and they were higher at I
200 than at I
400. The nitrogen contents per unit area (Na) increased from N5 to N20, but decreased from N20 to N25. The Na was higher at I
200 than at I
400 when Trifolium repens grew at N5 and N10, but it was higher at I
400 than at I
200 at N15 to N25. 相似文献
20.
The reaction of Sn(tmtaa)Cl2 (H2tmtaa=5,14-dihydro-6,8,15,17-tetramethyldi-benzo[b,i][1,4,8,11]tetraazacyclotetradecine) and ammonium thiocyanate or sodium azide under a mild condition resulted in trans six-coordinate tmtaa tin(IV) complexes, Sn(tmtaa)X2 (X=NCS, 1; X=N3, 2). However, the treatment of Sn(tmtaa)Cl2 and sodium picrate produced Sn(tmtaa)(Cl)(OC6H2 (2,4,6-3NO2)) (3). Only one chloro atom of Sn(tmtaa)Cl2 was substituted because of low nucleophilicity of the 2,4,6-trinitrophenolic anion in 3. Furthermore, because of the steric hindrance between the 2,4,6-trinitrophenolic group and the tmtaa ligand, which has a non-planar, saddle-shaped conformation, two chloro atoms cannot be substituted by two 2,4,6-trinitrophenolic groups simultaneously. All complexes were characterized by IR spectra, UV spectra, mass spectra, NMR spectra and elemental analyses, as well as DSC measurements. X-ray crystal structures of 1 and 3 reveal that the complexes retain the characteristic saddle-shaped configuration of H2tmtaa but have adopted the trans geometry. Solid state 119Sn NMR spectroscopy was used to study the bonding environment in the series of six-coordinate trans Sn(IV) tmtaa complexes. It can be found that the 119Sn chemical shifts of the Sn(IV) tmtaa complexes are almost not influenced by the substituents. 相似文献