Translocation-coupled DNA cleavage by the Type ISP restriction-modification enzymes

Endonucleolytic double-strand DNA break production requires separate strand cleavage events. Although catalytic mechanisms for simple dimeric endonucleases are available, there are many complex nuclease machines which are poorly understood in comparison. Here we studied the single polypeptide Type ISP restriction-modification (RM) enzymes, which cleave random DNA between distant target sites when two enzymes collide following convergent ATP-driven translocation. We report the 2.7 Angstroms resolution X-ray crystal structure of a Type ISP enzyme-DNA complex, revealing that both the helicase-like ATPase and nuclease are unexpectedly located upstream of the direction of translocation, inconsistent with simple nuclease domain-dimerization. Using single-molecule and biochemical techniques, we demonstrate that each ATPase remodels its DNA-protein complex and translocates along DNA without looping it, leading to a collision complex where the nuclease domains are distal. Sequencing of single cleavage events suggests a previously undescribed endonuclease model, where multiple, stochastic strand nicking events combine to produce DNA scission

Single apex plowing at polymer surfaces using a nanoindenter diamond AFM tip

Micro-patterning and subsequent imaging can be used an analytical method for the determination of the ductile or brittle properties of deeper surface layers. The depth profile of the UV-damaged polymer could be determined. An investigation illustrating the applicability of this method is presented

Nanolithographic determination of brittleness at polymer surfaces

AFM techniques were used to interrogate the mechanical properties of weathered polyester copolymer sheets near the exposed surface. Tapping mode tips, as well as a diamond tip mounted on a high spring constant cantilever, were used to scratch overlapping quadrilateral patterns into the polymer. The marred sites were micrographed and the RMS roughness was used as an index of brittleness. Propagation speed and normal force of the test cycle were optimized

Admitting hospital patients: a qualitative study of an everyday nursing task

In recent years new modes of nursing work have been introduced globally in response to radical changes in healthcare policies, technology and new ideologies of citizenship. These transformations have redefined orthodox nurse–patient relationships and further complicated the division of labour within health-care. One distinctive feature of the work of registered nurses has been their initial assessment of patients being admitted to hospital, and it is of interest that this area of nursing practice remains central to the registered nurse's role at a time where other areas of practice have been relinquished to other occupational groups. This qualitative study, drawing on conversation analysis and ethnographic techniques, explores this area of everyday nursing work. Initial nursing assessments have attracted considerable interest in the nursing literature, where it is clearly stated that assessments should be patient centred and seen as the important first step on the road to a therapeutic nurse–patient relationship. Results from this study lead to the conclusion that the actual nursing practice of patient assessment on admission to hospital is at odds with the recommendations of the literature and that a more routinised, bureaucratic form of work is devised by nurses as a means of expediting the process of admission. In this paper I explore the work of nurses when initially assessing the health and social care needs of adults undergoing admission into hospital. While there has been a small body of work that has explored this particular area of nursing work, few have taken the opportunity offered by qualitative methods to explore in detail the way frontline nurses and patients accomplish initial assessments. The article aims to contribute to the understanding of everyday nursing work by describing the ways in which initial nursing assessments are rooted in social relations and routine practices. My premise in this article is that descriptions in nursing literature of mundane work such as patient assessment are often idealised towards what ‘should happen’ and biased to highlight the individual nurse's judgemental, interpretive work. Consequently, these descriptions often overlook how mundane nursing work may be shaped by external routines of everyday practice, which operate to organise the individual nurse's working day, rather than reflecting some idealised version of nursing practice. An attempt will be made to rectify this bias whilst acknowledging the fact that nurses’ work is not easily understood, nor is it easy to research (Melia 1979; Lawler 1991). In acknowledgement of this frequent reference will be made to qualitative data collected in the UK during doctoral studies to support any of the points made