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Abstract: The biological role of manganese (Mn2+) has been a long-standing puzzle, since at low concentrations it activates several polymerases whilst at higher concentrations it inhibits. Viral RNA polymerases possess a common architecture, reminiscent of a closed right hand. The RNA-dependent RNA polymerase (RdRp) of bacteriophage {phi}6 is one of the best understood examples of this important class of polymerases. We have probed the role of Mn2+ by biochemical, biophysical and structural analyses of the wild-type enzyme and of a mutant form with an altered Mn2+-binding site (E491 to Q). The E491Q mutant has much reduced affinity for Mn2+, reduced RNA binding and a compromised elongation rate. Loss of Mn2+ binding structurally stabilizes the enzyme. These data and a re-examination of the structures of other viral RNA polymerases clarify the role of manganese in the activation of polymerization: Mn2+ coordination of a catalytic aspartate is necessary to allow the active site to properly engage with the triphosphates of the incoming NTPs. The structural flexibility caused by Mn2+ is also important for the enzyme dynamics, explaining the requirement for manganese throughout RNA polymerization.

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Abstract: The object of this study is a battle helmet of Corinthian type, now in the collections of The Manchester Museum. The Corinthian helmet has been called \u201csone of the great independent achievements of early Greek technology\u201d. It was manufactured out of a single piece of bronze, probably on a rod-anvil, and like all body-armour it was made to measure. This required excep tional skill on the part of the smith, but once discovered the design was so efficient that it was still being used in fifteenth-century Italy, more than 2000 years after its invention around 700 BC. However, by the seventeenth century the art had been lost and had to be re-invented for modern replicas. Victorious Greek cities often set up trophies of armour from the defeated as thank-offerings at temples. Like animals being sacrificed, weapons were \u201cskilled\u201d to be offered to the other world: so helmets had their cheek-pieces and nose-guards bent back. When the sanctuary became too crowded the trophies were cleared away and buried. The Manchester helmet was most likely found at such a site, probably Olympia itself. In order to sell it, the finder \u2014 probably in the 19th century \u2014 straightened out the cheek-pieces, which cracked at the edges, but the nose-guard was either missing or snapped off altogether: in its present form it is too short and too close to the face to be practical. X-ray fluorescence has shown that the main body of the helmet is a copper-tin alloy of varying composition at different places and containing iron and lead while the nose-guard contains zinc in high abundance. This key compositional difference indicates that the nose-guard is not the genuine broken-off piece retrieved from the finding place but is a modern substitute fabricated for restoration purposes. Synchrotron XRD at glancing angle and variable wavelength on several spots on the head and the nose-guard itself shows a shift of the copper Bragg reflections which can be related to Cu-Sn or Cu-Zn percentage composition. In addition, several corrosion products are identified. Small samples of corrosion extracted from the inside of the helmet have been used to obtain powder XRD patterns. The same samples have been studied with synchrotron micro-FTIR. Neutron diffraction sampling the bronze volume at different areas has also been used to quantify the composition. Crystallographic texture data obtained on a neutron diffractometer with large angular detector coverage was used to draw conclusions about the processes used to manufacture this precious example of archaic military technology. Some other interesting questions remain to be investigated in the near future.

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Abstract: This paper considers the design of a normal-conducting linac FEL in the context of the UK's New Light Source project. Capabilities and limitations of this approach are illustrated by reference to a 3GeV S-band linac design. The effects of high repetition rate operation and RF jitter are considered.

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Abstract: Total reflection X-ray fluorescence (TXRF) spectroscopy has attracted interest in recent years. Using this technique, almost all elements ranging from sodium (Z = 11) to uranium (Z = 92) in the periodic table can be detected and analysed in a wide concentration range in a single measurement. The present state-of-the-art sensitivities of TXRF are stretched to femtogram range by employing synchrotron radiation as an excitation source. This article aims to provide a basic overview of the TXRF technique to the general readers. We describe a TXRF spectrometer developed in a laboratory source. An X-ray fluorescence-microprobe beamline for TXRF is being constructed, as an extension of this activity, on the Indian synchrotron source, Indus-2.