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1.
R. A. Gibbons 《Biopolymers》1971,10(2):411-416
2.
《Inorganica chimica acta》1986,114(1):15-20
The silylphosphine ligand Ph2PSiMe3 reacts readily with a slurry of [Re(CO)5X] (X Cl, Br) in polar and in non-polar solvents to yield soluble cis-[Re(CO)4- (Ph2PSiMe3)X] (Ia, X Cl;Ib, X Br) via CO substitution. Compound I is readily hydrolyzed by water or silica gel to cis-[Re(CO)4(Ph2PH)X]. Compound Ib reacts with [Re(CO)5Br] to yield [Re2(CO)8(μ-PPh2)- (μ-Br)] (II), and with [Mn(CO)5Br] to yield [MnRe- (CO)8(μ-PPh2)(μ-Br)] (III).The reaction of Ph2PSiMe3 with [Mn(CO)5X] (X=Cl,Br,I) is highly dependent upon reaction conditions.In polar and in non-polar solvents, an excess of ligand gives mainly cis-[Mn(CO)4(Ph2PSiMe3)X] (IVa, X Cl;IVb, X Br;IVc, X I). With ligand: [Mn(CO)5X] reacting ratios in the range 0.5–1.0:1, the products from the three respective halomanganese complexes in THF were: (a) mainly [Mn2(CO)8(μ- PPh2)(μ-Cl) (Va); (b) both [Mn(CO)4(Ph2PSiMe3)Br] and [Mn2(CO)8(μ-PPh2)(μ-Br)] (Vb); and (c) exclusively [Mn(CO)4(Ph2PSiMe3)I]. The compounds IVa-c are stable in solution at ambient temperatures and are readily hydrolyzed by water or methanol to [Mn(CO)4(Ph2PH)X]. Compound IVb reacts at room temperature with [Mn(CO)5Cl] to yield only [Mn2- (CO)8(μ-PPh2)(μ-Br)] (Vb); compound IVc reacts in hot toluene with [Mn(CO)5Cl] to yield mainly [Mn2(CO)8(μ-PPh2)(μ-I)] (Vc), together with a small amount of the chloro-bridged analog.The dinuclear species II, III and Va-c appear to be formed mainly via an intermolecular elimination of Me3SiX from the appropriate [M(CO)4(Ph2PSiMe3)X] and metalpentacarbonylhalide (chloride or bromide) complexes. 相似文献
3.
Apoconalbumin binds Mn(II) at two sites with association constants of K1 = 7 (+/- 1) X 10(4) and K2 = 0.4 (+/- 0.25) X 10(4) M-1. The binding is tighter in the presence of excess bicarbonate resulting in K1 = 1.8 (+/- 0.2) X 10(5) and K2 = 3 (+/- 2) X 10(4) M-1. The electron paramagnetic resonance spectrum (at both 9 and 35 GHz) of Mn(II) bound at the tight site reveals a rhombic distortion (lambda = E/D approximately equal to 0.25-0.31) in the protein ligand environment of the mental ion. An evaluation of the 1/pT1p, paramagnetic contribution to the longitudinal relaxation rate of solvent protons with Mn(II)-, Mn(III)-, and Fe(III)-derivatives of conalbumin revealed that the mental ion in each site of conalbumin is accessible to one water molecule. For Mn(II)-conalbumin and Mn(III)-conalbumin species, inner coordination sphere protons are rapidly exchanging with the bulk solvent, while slow exchange conditions prevail for Fe(III)-conalbumin. 相似文献
4.
Yanyan Zhu Zhanfen Chen Zijian Guo Yan Wang Guangju Chen 《Journal of molecular modeling》2009,15(5):469-479
Theoretical studies on the coordination stabilities, spectra and DNA-binding trend for the series of metal-varied complexes,
M(IDB)Cl2 (M = Mn, Fe, Co, Ni, Cu and Zn; IDB = N, N -bis(2-benzimidazolylmethyl) amine), have been carried out by using the DFT/B3LYP
method and PCM model. The calculated coordination stabilities (S) for these complexes present a trend of S(Ni) > S(Co) > S(Fe)
> S(Cu) > S(Zn) > S(Mn). It has been estimated from the molecular orbital energies of the complexes that the DNA-binding affinities
(A) of the complexes are in the order of A(Zn) < A(Mn) < A(Fe) ≈ A(Co) < A(Ni) < A(Cu). The studied results indicate that
the Cu, Ni and Co complexes with large coordination stabilities present the low virtual orbitals, consequently yielding to
the favorable DNA-binding affinities. The spectral properties of excitation energies and oscillator strengths for M(IDB)Cl2 in the ultraviolet region were calculated by TD-DFT/B3LYP method. 相似文献
5.
《Inorganica chimica acta》1988,149(1):63-67
Reactions of SbCl5 with various covalent metal halides in MeCN have been studied as a convenient and direct route to metal hexachloroantimonate salts via Sb(V) halide abstraction. The isolation and characterization (Ir, Vis-UV, 1H NMR spectroscopic and microanalytical) of the complexes [Zn(MeCN)6][SbCl6]2, [CrCl2(MeCN)4][SbCl6], [SnCl3(MeCN)3][SbCl6], [TiCl2(MeCN)4][SbCl6]2, [Cp2M(Cl)(MeCN)x][SbCl6] M = ti, x = 1; M = Zr, Hf, x = 2, and [Cp2M(MeCN)y][SbCl6]2 M = Ti, y = 2; M = Zr, Hf, y = 3, is described. The reaction of MgCl2 with SbCl5 was carried out in EtOAC as solvent and gave [Mg(EtOAc)6][SbCl6]2. 121Sb NMR, IR and UV spectroscopic measurements provide positive identification of the SbCl6− anion. 相似文献
6.
M Waelbroeck J Camus M Tastenoy E Mutschler C Strohmann R Tacke G Lambrecht J Christophe 《Chirality》1991,3(2):118-123
(R)-Hexahydro-difenidol has a higher affinity for M1 receptors in NB-OK 1 cells, pancreas M3 and striatum M4 receptors (pKi 7.9 to 8.3) than for cardiac M2 receptors (pKi 7.0). (S)-Hexahydro-difenidol, by contrast, is nonselective (pKi 5.8 to 6.1). Our goal in the present study was to evaluate the importance of the hydrophobic phenyl, and cyclohexyl rings of hexahydro-difenidol for the stereoselectivity and receptor selectivity of hexahydro-difenidol binding to the four muscarinic receptors. Our results indicated that replacement of the phenyl ring of hexahydro-difenidol by a cyclohexyl group (----dicyclidol) and of the cyclohexyl ring by a phenyl moiety (----difenidol) induced a large (4- to 80-fold) decrease in binding affinity for all muscarinic receptors. Difenidol had a significant preference for M1, M3, and M4 over M2 receptors; dicyclidol, by contrast, had a greater affinity for M1 and M4 than for M2 and M3 receptors. The binding free energy decrease due to replacement of the phenyl and the cyclohexyl groups of (R)-hexahydro-difenidol by, respectively, a cyclohexyl and a phenyl moiety was almost additive in the case of M4 (striatum) binding sites. In the case of the cardiac M2, pancreatic M3, or NB-OK 1 M1 receptors the respective binding free energies were not completely additive. These results suggest that the four (R)-hexahydro-difenidol "binding moieties" (phenyl, cyclohexyl, hydroxy, and protonated amino group) cannot simultaneously form optimal interactions with the M1, M2, and M3 muscarinic receptors.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
7.
Effect of Oxygen Tension, Mn(II) Concentration, and Temperature on the Microbially Catalyzed Mn(II) Oxidation Rate in a Marine Fjord 总被引:2,自引:2,他引:2
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We present evidence that the oxidation of Mn(II) in a zone above the O2/H2S interface in the water column of Saanich Inlet, British Columbia, Canada, is microbially catalyzed. We measured the uptake of 54Mn(II) in water samples under in situ conditions of pH and temperature and in the presence and absence of oxygen. Experiments in the absence of oxygen provided a measure of the exchange of the tracer between the dissolved and solid pools of Mn(II); we interpret the difference between experiments in the presence and absence of oxygen to be a measure of Mn(II) oxidation. Using this method we examined the effect of oxygen tension, Mn(II) concentration, and temperature on the initial in situ Mn(II) oxidation rate (V0). Mn(II) oxidation was almost twice as fast under conditions of 67% air saturation (V0=5.5 nM h−1) as with the in situ concentration of 15 μM (5% air saturation; V0=3.1 nM h−1). Additions of ca. 18 μM Mn(II) completely inhibited all Mn(II) oxidation at three different depths in the oxidizing zone, and there was a temperature optimum for Mn(II) oxidation of around 20°C. These results are consistent with biologically mediated Mn(II) oxidation and indicate that the rate is limited by both oxygen and the concentration of microbial binding sites in this environment. 相似文献
8.
From the many attempts to produce a conceptual framework for the organization of living systems, the notions of (M,R) systems and Autopoiesis stand out for their rigor, their presupposition of the circularity of metabolism, and the new epistemologies that they imply. From their inceptions, these two notions have been essentially disconnected because each has defined its own language and tools. Here we demonstrate the existence of a deep conceptual link between (M,R) systems and Autopoietic systems. This relationship permits us to posit that Autopoietic systems, which have been advanced as capturing the central aspects of living systems, are a subset of (M,R) systems. This result, in conjunction with previous theorems proved by Rosen, can be used to outline a demonstration that the operation of Autopoietic systems cannot be simulated by Turing machines. This powerful result shows the potential of linking these two models. Finally, we suggest that the formalism of (M,R) systems could be used to model the circularity of metabolism. 相似文献
9.
(M,R)-systems, (P,M,C)-nets, hierarchical decay, and biological aging: reminiscences of Robert Rosen
Witten TM 《化学与生物多样性》2007,4(10):2332-2344
I have the pleasure to present a number of personal experiences that I had with Robert Rosen, both as his student and as a research colleague, and I will describe how this affected my academic career over the past decades. As a matter of fact, Rosen's work with (M,R)-systems as well as his continuing mentorship guided me into my own research in gerontology and geriatrics. Amazingly, this still continues to affect my work in complexity theory after 30 years. 相似文献
10.
Positive electrodes such as LiFePO4 and LiMnPO4 nanomaterials with olivine structures are considered as most efficient cathode materials for application in lithium ion batteries. Recently, several methods have been proposed for the preparation of lithium metal phosphates as cathodes for lithium ion batteries and their electrochemical performances have been investigated. Over the last 20 years, several synthetic methods have been proposed for lithium metal phosphate nanomaterials. In this review, hydrothermal and solvothermal syntheses of LiFePO4 and LiMnPO4 nanomaterials at low and high temperatures are discussed, including microwave‐hydrothermal and microwave‐solvothermal methods. The effect of particle size and particle morphology on the electrochemical properties of LiFePO4 and LiMnPO4 cathode materials are also discussed. In addition, the recently emerged supercritical solvothermal and supercritical hydrothermal syntheses of LiFePO4 and LiMnPO4 nanomaterials and their electrochemical property also been addressed. 相似文献
11.
The activation of porcine heart latent protein phosphatase (Fc.M) by pretreatment with Mn++ followed by trypsin (Mn/trypsin) can be stimulated 2.5-fold by including NaCl or KCl in the activation mixtures. The salts also stimulated the activation of the enzyme by Mn++ to the same level as that obtained by Mn/trypsin pretreatment in the absence of salt. The presence of salt in both the Mn++ and Mn/trypsin activations decreased the Mn++ requirement 10-fold in each case. Treatment of latent Fc.M by Mn/trypsin in the presence of 0.2 M NaCl or KCl offers a convenient method of expressing the full potential activity of the protein phosphatase. 相似文献
12.
The central concern of this paper is to re-evaluate Rosen's replicating (M,R)-systems, presented in his book 'Life Itself ', where M and R signify metabolism and repair, respectively. We look anew at Rosen's model of an organism in the light of extensive research into natural hierarchical systems, and the paper presents conclusions drawn from a comparison between Rosen's relational model and that of a birational complementary natural hierarchy. We accept that Rosen's relational model provides a useful stepping stone to understanding the nature of life, but also suggest that it induces potentially digressive conclusions. We conclude that a binary segregation of relational assemblies into mechanisms and organisms is insufficient, and indicate how a threefold segregation throws new light on Rosen's model. An organism is not 'the complement of a mechanism': the complement of a mechanism is its ecosystem. An organism is the 'complex interface' between mechanism and ecosystem. 相似文献
13.
Robert Rosen's concept of (M,R)-systems was a fundamental advance in our understanding of the essential nature of a living organism as a self-organizing system, one that is closed to efficient causation, synthesizing, and maintaining all of the catalysts necessary for sustained operation during the whole period of its lifetime. Although it is not difficult to construct a model metabolic system to represent an (M,R)-system, such a model system will typically appear to lack organizational invariance, an essential property of a living (M,R)-system. To have this property, an (M,R)-system must not only be closed to external causation, it must also have its organization coded within itself, i.e., the knowledge of which components are needed for which functions must not be defined externally. In this paper, we discuss how organizational invariance may be achieved, and we argue that the apparent failure of previous models to be organizationally invariant is an artifact of the usual practice of treating catalytic cycles as 'black boxes'. If all of the steps in such a cycle are written as uncatalyzed chemical reactions, then it becomes clear that the organization of the system is fully defined by the chemical properties of the molecules that compose it. 相似文献
14.
《Inorganica chimica acta》1986,112(2):189-195
The synthesis, aqueous absorption and reflectance spectra, cyclic voltammetry and ligand field photochemistry of a series of M(bpym)2Cl2 (M=Mn(II), Co(II), Ni(II), Cu(II) and bpym=2,2′-bipyrimidine) are reported here. Ligand field electronic spectral assignments are made by comparison to analogous M(bpy)2Cl2(s) (bpy=2,2′-bipyridine) and M(bpym)32+ complexes. Ligand field absorption maxima are shifted to lower energy as a result of bpym loss vs. M(bpym)32+ complexes. Metal to ligand charge transfer absorption energies increase as a result of dM orbital stabilization vs. M(bpym)32+ complexes. Cyclic voltammetry indicates ring opening upon reduction of the complexes. The complexes are photochemically inert (φmax<0.002) at the irradiated wavelengths. 相似文献
15.
I. S. Sergeeva I. N. Bolotov Yu. V. Bespalaya A. A. Makhrov A. L. Bukhanova V. S. Artamonova 《Biology Bulletin》2008,35(1):102-105
The shells of Pearl mussels from the basins of the Solza, Keret’, and Umba rivers flowing into the White Sea have been measured to determine the ratio of shell convexity to its maximum height. This ratio is the main character that, according to Bogatov et al. (2003), allows one to distinguish between three species of the genus Margaritifera: M. margaritifera, M. elongata, and M. borealis. It has been found that the above ratio gradually increases as the shell grows. Therefore, this character is unsuitable for species diagnosis, the more so that no hiatus in it between the three forms of pearl mussels has been revealed in any of the samples studied. On this basis, it may be concluded that Northern Europe, including Russia, is inhabited by only one species of pearl mussels, M. margaritifera. 相似文献
16.
I. Băianu 《Bulletin of mathematical biology》1973,35(1-2):213-217
On the basis of Rosen's representation of (M, R)-systems as sequential machines (Rosen,Bull. Math. Biophys.,26, 103–111, 1964), the existence of projective limits in categories of general (M, R)-systems is proved. 相似文献
17.
Andy Banh Valarie Chavez Julia Doi Allison Nguyen Sophia Hernandez Vu Ha Peter Jimenez Fernanda Espinoza Hope A. Johnson 《PloS one》2013,8(10)
Bacterial manganese (Mn) oxidation plays an important role in the global biogeochemical cycling of Mn and other compounds, and the diversity and prevalence of Mn oxidizers have been well established. Despite many hypotheses of why these bacteria may oxidize Mn, the physiological reasons remain elusive. Intracellular Mn levels were determined for Pseudomonas putida GB-1 grown in the presence or absence of Mn by inductively coupled plasma mass spectrometry (ICP-MS). Mn oxidizing wild type P. putida GB-1 had higher intracellular Mn than non Mn oxidizing mutants grown under the same conditions. P. putida GB-1 had a 5 fold increase in intracellular Mn compared to the non Mn oxidizing mutant P. putida GB-1-007 and a 59 fold increase in intracellular Mn compared to P. putida GB-1 ∆2665 ∆2447. The intracellular Mn is primarily associated with the less than 3 kDa fraction, suggesting it is not bound to protein. Protein oxidation levels in Mn oxidizing and non oxidizing cultures were relatively similar, yet Mn oxidation did increase survival of P. putida GB-1 when oxidatively stressed. This study is the first to link Mn oxidation to Mn homeostasis and oxidative stress protection. 相似文献
18.
AimsA bridging ligand 2,4,6-pyridine tricarboxylic acid (H3ptc) and its manganese(II) complex [Mn(Hptc)(phen)(OH)]n(Hptc = 2,4,6-pyridine tricarboxylic acid, phen = 1,10-phenanthroline) have been synthesized and characterized.Main methodsThe interaction with DNA (HeLa and KB) was carried out by fluorescence spectrum and gel electrophoresis assay. In vitro apoptosis assay and cytotoxicity assay detect the manganese (II) complex interaction with cancer cells.Key findingsFluorescence spectrum demonstrated the ability of the complexes to interact with DNA in an intercalative mode. Gel electrophoresis assay exhibited more effective DNA-cleavage activity. In vitro apoptosis assay of the complexes were examined on HeLa and KB cells, exhibited cytotoxic specificity and a significant cancer cell inhibitory rate.SignificanceThe complex may be a latent antitumor agent as a result of its unique interaction mode with DNA and cancer cells inhibition effect. 相似文献
19.
Functional expression of M(1), M(3) and M(5) muscarinic acetylcholine receptors in yeast 总被引:1,自引:0,他引:1
Erlenbach I Kostenis E Schmidt C Hamdan FF Pausch MH Wess J 《Journal of neurochemistry》2001,77(5):1327-1337
The goal of this study was to functionally express the three G(q)-coupled muscarinic receptor subtypes, M(1), M(3) and M(5), in yeast (Saccharomyces cerevisiae). Transformation of yeast with expression constructs coding for the full-length receptors resulted in very low numbers of detectable muscarinic binding sites (B(max) < 5 fmol/mg). Strikingly, deletion of the central portion of the third intracellular loops of the M(1), M(3) and M(5) muscarinic receptors resulted in dramatic increases in B(max) values (53-214 fmol/mg). To monitor productive receptor/G-protein coupling, we used specifically engineered yeast strains that required agonist-stimulated receptor/G-protein coupling for cell growth. These studies showed that the shortened versions of the M(1), M(3) and M(5) receptors were unable to productively interact with the endogenous yeast G protein alpha-subunit, Gpa1p, or a Gpa1 mutant subunit that contained C-terminal mammalian Galpha(s) sequence. In contrast, all three receptors gained the ability to efficiently couple to a Gpa1/Galpha(q) hybrid subunit containing C-terminal mammalian Galpha(q) sequence, indicating that the M(1), M(3) and M(5) muscarinic receptors retained proper G-protein coupling selectivity in yeast. This is the first study to report the expression of muscarinic receptors in a coupling-competent form in yeast. The strategy described here, which involves structural modification of both receptors and co-expressed G proteins, should facilitate the functional expression of other classes of G protein-coupled receptors in yeast. 相似文献