Reconfigurable self-assembly through chiral control of interfacial tension

Author Posting. © The Author(s), 2011. This is the author's version of the work. It is posted here by permission of Nature Publishing Group for personal use, not for redistribution. The definitive version was published in Nature 481 (2012): 348–351, doi:10.1038/nature10769.From determining optical properties of simple molecular crystals to establishing preferred handedness in highly complex vertebrates, molecular chirality profoundly influences the structural, mechanical, and optical properties of both synthetic and biological matter at macroscopic lengthscales1,2. In soft materials such as amphiphilic lipids and liquid crystals, the competition between local chiral interactions and global constraints imposed by the geometry of the self-assembled structures leads to frustration and the assembly of unique materials3-6. An example of particular interest is smectic liquid crystals, where the 2D layered geometry cannot support twist, expelling chirality to the edges in a manner analogous to the expulsion of a magnetic field from superconductors7-10. Here, we demonstrate a previously unexplored consequence of this geometric frustration which leads to a new design principle for the assembly of chiral molecules. Using a model system of colloidal membranes11, we show that molecular chirality can control the interfacial tension, an important property of multi-component mixtures. This finding suggests an analogy between chiral twist which is expelled to the edge of 2D membranes, and amphiphilic surfactants which are expelled to oil-water interfaces12. Similar to surfactants, chiral control of interfacial tension drives the assembly of myriad polymorphic assemblages such as twisted ribbons with linear and circular topologies, starfish membranes, and double and triple helices. Tuning molecular chirality in situ enables dynamical control of line tension that powers polymorphic transitions between various chiral structures. These findings outline a general strategy for the assembly of reconfigurable chiral materials which can easily be moved, stretched, attached to one another, and transformed between multiple conformational states, thus enabling precise assembly and nano-sculpting of highly dynamical and designable materials with complex topologies.This work was supported by the National Science Foundation (NSF-MRSEC-0820492, NSF-DMR-0955776, NSF-MRI 0923057) and Petroleum Research Fund (ACS-PRF 50558-DNI7).2012-07-0

How patients understand depression associated with chronic physical disease - A systematic review

Background: Clinicians are encouraged to screen people with chronic physical illness for depression. Screening alone may not improve outcomes, especially if the process is incompatible with patient beliefs. The aim of this research is to understand peoples beliefs about depression, particularly in the presence of chronic physical disease. Methods: A mixed method systematic review involving a thematic analysis of qualitative studies and quantitative studies of beliefs held by people with current depressive symptoms. MEDLINE, EMBASE, PSYCHINFO, CINAHL, BIOSIS, Web of Science, The Cochrane Library, UKCRN portfolio, National Research Register Archive, Clinicaltrials.gov and OpenSIGLE were searched from database inception to 31st December 2010. A narrative synthesis of qualitative and quantitative data, based initially upon illness representations and extended to include other themes not compatible with that framework. Results: A range of clinically relevant beliefs was identified from 65 studies including the difficulty in labeling depression, complex causal factors instead of the biological model, the roles of different treatments and negative views about the consequences of depression. We found other important themes less related to ideas about illness: the existence of a self-sustaining depression spiral; depression as an existential state; the ambiguous status of suicidal thinking; and the role of stigma and blame in depression. Conclusions: Approaches to detection of depression in physical illness need to be receptive to the range of beliefs held by patients. Patient beliefs have implications for engagement with depression screening

T-resveratrol accumulation and polygalacturonase inhibition during infection of grape berries by Botrytis cinerea

The resistance of immature grape berries to Botrytis cinerea Pers. ex Fr. results from a combination of factors, among which the accumulation of the stilbene phytoalexin t-resveratrol. Stilbene accumulation is thought to be induced by oligogalacturonides (OGs) which are released from the plant cell wall during tissue maceration catalysed by polygalacturonases (PGs) produced by necrotrophic fungal pathogens. Inhibitors of PG activity, the polygalacturonase- inhibiting proteins (PGIPs), have the capability to slow the hydrolytic activity of PGs and favour the accumulation of active OGs. In the present work we have observed that artificial inoculation of grape inflorescences and immature berries at bloom and post bloom, leads to severe infection of the rachis, while lesions on young berries did not result in the development of the disease, but in the development of necrotic spots and rings. PG was detectable in berry tissues, but its secretion was significantly lower than in infected leaves. Tissues of immature berries reacted to B. cinerea inoculation by a marked accumulation of t-resveratrol. PG produced during spore germination of B. cinerea elicited t-resveratrol accumulation. Apoplastic fluids (AFs) from immature berries and leaves were found to inhibit total PG activity produced by B. cinerea, indicating the involvement of a proteinaceous or non-proteinaceous PG inhibitor, or both, as intercellular defence mechanisms. Taken together, our results suggest that the inhibition of PG produced by B. cinerea mediated by a putative PG inhibitor during the early stages of infection of immature grape berries plays a central role in promoting accumulation of t-resveratrol and, consequently, the restriction of pathogen spread