Periplasmic superoxide dismutases in Aquaspirillum magnetotacticum

Aquaspirillum magnetotacticum MS-1 cells cultured microaerobically (dissolved O₂ tension 1% of saturation), expressed proteins with superoxide dismutase (SOD) activity. The majority (roughly 95%) of total cell superoxide dismutase activity was located in the cell periplasm with little or no activity in the cell cytoplasm. Irontype SOD (FeSOD) contributed 88% of the total activity activity detected, although a manganese-type SOD (MnSOD) was present in the periplasm as well. Cells cultured at a higher dissolved O₂ tension (10% of saturation) expressed increased activity of the MnSOD relative to that of the FeSOD.     

磁场对大豆共生固氮的效应

恒定磁场处理慢生大豆根瘤菌“005”和接种后的大豆植株,发现磁场可以提高根瘤的固氮活性。在一定的磁场强度(70—100mT)下,固氮活性平均可以提高4—5倍,植株的结瘤数和根瘤重量平均提高2—3倍。从这样的根瘤中所分离出的根瘤菌,由慢生型转变成快生型,在100植株中有17株的根瘤分离出快生菌。生长世代时间和培养溶液中的pH值与慢生型不同,而与快生型相同。     

Optically detected magnetic resonance in lysozyme: evidence for three phosphorescent TRP residues

The Optically Detected Magnetic Resonance spectrum of lysozyme has been shown to consist of a multiplet of narrow components, at -1565 MHz, 1585 MHz, and 1620 MHz. The 1585 MHz component is the strongest feature of the spectrum. This is consistent with earlier reports which apparently resolved only this principal component in lysozyme. The linewidths reported here are the narrowest ever reported for tryptophan in proteins. Using Microwave-Induced Phosphorescence techniques, the dominant 1585 MHz line is seen to be coupled to a "narrow" phosphorescence emission component at about 4134A. This component has a bandwidth of about 25A compared to 42A for the normal O-O band for tryptophan in lysozyme.     

Acute and Prolonged Alterations in Brain Free Magnesium Following Fluid Percussion-Induced Brain Trauma in Rats

Abstract: Several studies have reported declines in brain total and free magnesium concentration after a traumatic insult to the CNS. Although the evidence suggests that this magnesium decline is associated with eventual neurologic outcome after trauma, the duration of free magnesium decline and its impact on related bioenergetic variables are relatively unknown. The present study has therefore used phosphorus magnetic resonance spectroscopy to determine the length of time that free magnesium remains suppressed after traumatic brain injury in rats. Immediately after the traumatic event, brain intracellular free magnesium declined to <60% of preinjury values and remained significantly depressed (50 ± 8%; p < 0.001) for 5 days before recovering to preinjury levels by day 8. Cytosolic phosphorylation ratio and mitochondrial oxidative capacity also significantly decreased ( p = 0.008) and increased ( p = 0.002), respectively, after trauma. However, unlike the time of maximum magnesium change, the maximum changes in these bioenergetic variables occurred at 16–24 h after trauma and thereafter remained stable until after the magnesium had recovered. We conclude that free magnesium decline after trauma precedes changes in bioenergetic variables. Furthermore, therapies targeted at reestablishing magnesium homeostasis after trauma may require administration over a 1-week period.     

Synthesis and characterization of SrCu2(O2CR)3(bdmap)3 and Bi2(O2CCH3)4(bdmap)2(H2O) (R = CH3, CF3; bdmap = 1,3-bis(dimethylamino)-2-propanolato)

New mixed metal complexes SrCu₂(O₂CR)₃(bdmap)₃ (R = CF₃ (1a), CH₃ (1b)) and a new dinuclear bismuth complex Bi₂(O₂CCH₃)₄(bdmap)₂(H₂O) (2) have been synthesized. Their crystal structures have been determined by single-crystal X-ray diffraction analyses. Thermal decomposition behaviors of these complexes have been examined by TGA and X-ray powder diffraction analyses. While compound 1a decomposes to SrF₂ and CuO at about 380°C, compound 1b decomposes to the corresponding oxides above 800°C. Compound 2 decomposes cleanly to Bi₂O₃ at 330°C. The magnetism of 1a was examined by the measurement of susceptibility from 5–300 K. Theoretical fitting for the susceptibility data revealed that 1a is an antiferromagnetically coupled system with g = 2.012(7), −2J = 34.0(8) cm⁻¹. Crystal data for 1a: C₂₇H₅₁N₆O₉F₉Cu₂Sr/THF, monoclinic space group P2₁/m, A = 10.708(6), B = 15.20(1), C = 15.404(7) Å, β = 107.94(4)°, V = 2386(2) ų, Z = 2; for 1b: C₂₇H₆₀N₆O₉Cu₂Sr/THF, orthorhombic space group Pbcn, A = 19.164(9), B = 26.829(8), C = 17.240(9) Å, V = 8864(5) ų, Z = 8; for 2: C₂₂H₄₈O₁₁N₄Bi₂, monoclinic space group P2₁/c, A = 17.614(9), B = 10.741(3), C = 18.910(7) Å, β = 109.99(3)°, V = 3362(2) ų, Z = 4.     

A tooth at the border of two morphogenetic fields

A tooth at the border between two morphogenetic fields (mandibular canine and honing premolar) may become morphologically similar to and/or functionally incorporated with the teeth of either field. In light of this, observations of the morphology and occlusion of female anthropoid C1s from 58 extant species are presented to assess whether and to what extent they exhibit incisor-like form and function. Female C1s in 74% of the taxa observed exhibit well developed incisor-like traits which may reflect field border phenomena. In another 9%, incisor traits are present but they are not examples of field border phenomena. Interspecies variation in female C1 morphology is related to behavior, function, natural selection and phyletic inertia. A selection model, derived from the data, is used to explain C1 sexual dimorphism and the evolution of male and female human canines. The data's relevance to the field vs clone theory debate is also discussed.     

Molecular magnetic materials from polyoxometalates

The significance of polyoxometalates in the field of molecular magnetism is discussed. We show that this kind of inorganic complexes provides remarkable examples for the study of the exchange interactions in clusters. On the other hand, we examine the possibility of using these metal oxide anions as magnetic components of molecular materials containing organic tetrathiafulvalenes as electron donor molecules.     

脑部磁刺激场的理论模型

作为脑部磁刺激研究的一项基础工作,建立了刺激磁场中的球形头模型、对方形线圈在其内产生的时变磁场和感应电场进行了理论研究.导出(?).(?).(?)的解析表达式,分析了场的特性和刺激强度的分布规律.为进一步探索时变磁场对人脑的最佳刺激方式和作用机理提供了初步的理论基础.