Metalloproteins can be self-assembled in molecularly ordered, electrochemically addressable arrays. We report here on a study of the transport characteristics of the blue copper protein, azurin, from Pseudomonas aeruginosa, by a combination of electrochemical and scanning probe techniques (scanning tunnelling microscopy and conducting atomic force microscopy). Redox-switchable chemisorbed molecular arrays can be formed from both wild-type and mutant proteins using the strong affinity of cysteine residue thiolates for pristine gold surfaces. The molecular transconductance of single protein molecules within these arrays has been studied under controllable conditions where it has been additionally possible to resolve the effects of protein mechanical perturbation. Although tunnelling appears to be non-resonant and adequately explained through the use of a square barrier model, under some conditions the contribution of the redox-active copper centre to conductance is resolvable.

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Soft X-ray contact microscopy using laser generated plasma sources.

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Soft X-ray contact microscopy (SXCM) is a technique which can image the ultrastructure of living biological specimens at a resolution considerably better than light microscopy (LM). Laser generated plasmas are ideal soft X-ray sources for contact microscopy, since they are capable of providing an intense source of X-rays within the water window region (280-530eV) on a nanosecond timescale. This allows the image to be recorded before the onset of radiation damage and avoids a blurring of the image due to specimen movement. The first experiments used large national laser facilities for X-ray production, although it has become clear that for SXCM to become accessible to the lifescience community, smaller, laboratory scale laser systems are required.Two such laser systems have been developed for the generation of water window X-rays. A small beam line of the large Nd:GLASS laser "Vulcan" at the Rutherford Appleton Laboratory (RAL), UK, has been set up, giving approximately 6-8J on target at a wavelength of 1 .O6zm. In addition, a smaller discharge pumped KrF excimer laser, based at the Clarendon Laboratory, University of Oxford, UK, has been built, giving approximately 2J at a wavelength of 249nm. A comparison of the X-ray emission from plasma generated by the two laser systems using various target materials has been made and evaluated with respect to their application to SXCM.