Scottish bishops and the relic-lists of the cartulary of Christchurch Priory, Twynham, Hampshire, 1200–1221 (with an edition and translation of the text by John Reuben Davies)

No abstract available

'All this I say against the rage of archdeacons against my poor fellow citizens': archdeacons' authority and identity in twelfth-century England

No abstract available

The bishops of King Stephen's reign

Traditionally, the bishops who held office during the civil war which dominated King Stephen's reign (1135-1154) have been considered weak and ineffective, able neither to bring peace between the two sides or among warring local barons nor to protect their flocks or even themselves from the so-called 'Anarchy'. The explanation for this has been found in the bishops' lack of spiritual calibre. Bishops have also been seen as withdrawing their support from the king and ending their involvement in royal government, partly because of increasing general ecclesiastical desire for separation between Church and State and partly because of specific disputes with Stephen. As a consequence of all this, bishops are allowed little importance in modern histories of Stephen's reign. This thesis shows that modern historiographical consensus is based in flawed interpretive frameworks which have led to misinterpretation of the nature of the episcopate and its importance in Stephen's reign. It offers more valid alternatives and then re-examines, the royal, ecclesiastical and, especially, the local evidence in light of them to show that, in fact, the bishops were crucially important figures in regional politics, religion and society during the civil war. It proves as well, that they could possess considerable spiritual authority and continued to be committed to the king and active in the government of the kingdom throughout the period. Additionally, each of these also has consequences for how the episcopacy and Anglo-Norman history in general are understood. This is, therefore, a reassessment of the bishops of King Stephen's reign

Opportunities for mesoporous nanocrystalline SnO2 electrodes in kinetic and catalytic analyses of redox proteins

PFV (protein film voltammetry) allows kinetic analysis of redox and coupled-chemical events. However, the voltammograms report on the electron transfer through a flow of electrical current such that simultaneous spectroscopy is required for chemical insights into the species involved. Mesoporous nanocrystalline SnO2 electrodes provide opportunities for such ‘spectroelectrochemical’ analyses through their high surface area and optical transparency at visible wavelengths. Here, we illustrate kinetic and mechanistic insights that may be afforded by working with such electrodes through studies of Escherichia coli NrfA, a pentahaem cytochrome with nitrite and nitric oxide reductase activities. In addition, we demonstrate that the ability to characterize electrocatalytically active protein films by MCD (magnetic circular dichroism) spectroscopy is an advance that should ultimately assist our efforts to resolve catalytic intermediates in many redox enzymes

Redox and Chemical Activities of the Hemes in the Sulfur Oxidation Pathway Enzyme SoxAX

BACKGROUND: SoxAX enzymes initiate microbial oxidation of reduced inorganic sulfur compounds. Their catalytic mechanism is unknown. RESULTS: Cyanide displaces the CysS(-) ligand to the active site heme following reduction by S(2)O(4)(2-) but not Eu(II). CONCLUSION: An active site heme ligand becomes labile on exposure to substrate analogs. SIGNIFICANCE: Elucidation of SoxAX mechanism is necessary to understand a widespread pathway for sulfur compound oxidation. SoxAX enzymes couple disulfide bond formation to the reduction of cytochrome c in the first step of the phylogenetically widespread Sox microbial sulfur oxidation pathway. Rhodovulum sulfidophilum SoxAX contains three hemes. An electrochemical cell compatible with magnetic circular dichroism at near infrared wavelengths has been developed to resolve redox and chemical properties of the SoxAX hemes. In combination with potentiometric titrations monitored by electronic absorbance and EPR, this method defines midpoint potentials (E(m)) at pH 7.0 of approximately +210, -340, and -400 mV for the His/Met, His/Cys(-), and active site His/CysS(-)-ligated heme, respectively. Exposing SoxAX to S(2)O(4)(2-), a substrate analog with E(m) ~-450 mV, but not Eu(II) complexed with diethylene triamine pentaacetic acid (E(m) ~-1140 mV), allows cyanide to displace the cysteine persulfide (CysS(-)) ligand to the active site heme. This provides the first evidence for the dissociation of CysS(-) that has been proposed as a key event in SoxAX catalysis

The Syntheses and Characterization of Binuclear Clathrochelate Complexes

A series of binuclear clathrochelate complexes, MA(II)MB(II)L+, have been synthesized and characterized for the purpose of examining electrostatic, magnetic, and electronic delocalization effects in binuclear complexes. The clathrochelating ligand, L3-, is a bicyclic Schiff-base compound derived from 3 equiv of 2-hydroxy-5-methylisophthalaldehyde and 2 equiv of 2,2',2"-triaminotriethylamine (tren). The following MA(II)MB(II)L+ complexes were prepared by combinations of metal-ion template, metathesis, and insertion reactions: homonuclear complexes with MA = MB = Mn, Fe, Co, Cu, Zn, and Cd; heteronuclear complexes with MA = Mn, MB = Co, Ni, Zn, Cd, and Mg; MA = Fe, MB = Mn, Co, Ni, Cu, Zn, Cd, and Mg; MA = Cu, MB = Mn, Co, Ni, Zn, Cd, and Mg. In addition, syntheses and characterization are reported for the binuclear Cu(II)Cu(II)LH2+ complex and mononuclear complexes of the non-deprotonated ligand, MLH3n+, with M = Na(I), Mn(II), Mn(III), Fe(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), and Mg(II). The MA redox potentials of the Mn(III)/Mn(II), Fe(III)/Fe(II), and Cu(II)/Cu(I) couples were determined by cyclic voltammetry and differential pulse voltammetry for three series containing both homonuclear and heteronuclear complexes, Mn(II)MB(II)L+, Fe(II)MB(II)L+, and Cu(II)MB(II)L+. Within experimental error, the average of the MA redox potentials for each series of heteronuclear complexes was the same as that for the corresponding homonuclear complex. This result suggests that there is no measurable stabilization of Mn(III)Mn(II)L2+, Fe(III)Fe(II)L2+, and Cu(I)Cu(II)L with respect to mixed-valent heteronuclear analogues. The magnetic properties of a series of four homonuclear MA(II)MB(II)L+ complexes were examined by variable temperature susceptibility measurements (MA = MB = Mn, Fe, Co, and Cu). In all cases, weak antiferromagnetic coupling between the metal centers was observed (-33.5 cm-1 &#60; J &#60; -0.8 cm-1). The weakness is attributed to limited overlap of metal orbitals with those of the bridging atoms.</p

Redox properties and electron paramagnetic resonance spectroscopy of the transition state complex of Azotobacter vinelandii nitrogenase

AbstractNitrogenase is a two-component metalloenzyme that catalyzes a MgATP hydrolysis driven reduction of substrates. Aluminum fluoride plus MgADP inhibits nitrogenase by stabilizing an intermediate of the on-enzyme MgATP hydrolysis reaction. We report here the redox properties and electron paramagnetic resonance (EPR) signals of the aluminum fluoride-MgADP stabilized nitrogenase complex of Azotobacter vinelandii. Complex formation lowers the midpoint potential of the [4Fe-4S] cluster in the Fe protein. Also, the two-electron reaction of the unique [8Fe-7S] cluster in the MoFe protein is split in two one-electron reactions both with lower midpoint potentials. Furthermore, a change in spin-state of the two-electron oxidized [8Fe-7S] cluster is observed. The implications of these findings for the mechanism of MgATP hydrolysis driven electron transport within the nitrogenase protein complex are discussed

Effect of multiple reusing of simulated air showers in detector simulations

The study of high energy cosmic rays requires detailed Monte Carlo simulations of both, extensive air showers and the detectors involved in their detection. In particular, the energy calibration of several experiments is obtained from simulations. Also, in composition studies simulations play a fundamental role because the primary mass is determined by comparing experimental with simulated data. At the highest energies the detailed simulation of air showers is very costly in processing time and disk space due to the large number of secondary particles generated in interactions with the atmosphere. Therefore, in order to increase the statistics, it is quite common to recycle single showers many times to simulate the detector response. As a result, the events of the Monte Carlo samples generated in this way are not fully independent. In this work we study the artificial effects introduced by the multiple use of single air showers for the detector simulations. In particular, we study in detail the effects introduced by the repetitions in the kernel density estimators which are frequently used in composition studies.Comment: 15 pages and 4 figure