Photodissociation chemistry footprints in the Starburst galaxy NGC 253

We report the first detection of PDR molecular tracers, namely HOC+, and CO+, and confirm the detection of the also PDR tracer HCO towards the starburst galaxy NGC 253, claimed to be mainly dominated by shock heating and in an earlier stage of evolution than M 82, the prototypical extragalactic PDR. Our CO+ detection suffers from significant blending to a group of transitions of 13CH3OH, tentatively detected for the first time in the extragalactic interstellar medium. These species are efficiently formed in the highly UV irradiated outer layers of molecular clouds, as observed in the late stage nuclear starburst in M 82. The molecular abundance ratios we derive for these molecules are very similar to those found in M 82. This strongly supports the idea that these molecules are tracing the PDR component associated with the starburst in the nuclear region of NGC 253. A comparison with the predictions of chemical models for PDRs shows that the observed molecular ratios are tracing the outer layers of UV illuminated clouds up to two magnitudes of visual extinction. Chemical models, which include grain formation and photodissociation of HNCO, support the scenario of a photo-dominated chemistry as an explanation to the abundances of the observed species. From this comparison we conclude that the molecular clouds in NGC 253 are more massive and with larger column densities than those in M 82, as expected from the evolutionary stage of the starbursts in both galaxies.Comment: 32 pages, 4 figures, Published in Ap

Food availability and predation risk, rather than intrinsic attributes are the main factors shaping the reproductive decisions of a long-lived predator

Acknowledgements We thank B. Sheldon and two anonymous reviewers for all their helpful comments on a previous version of the manuscript. Our thanks also go to M. Davison, B. Little, P. Hotchin, D. Anderson and all other field assistants for their help with data collection and Forest Enterprise, particularly Tom Dearnley and Neville Geddes for facilitating work in Kielder Forest. We are also grateful to C. Sutherland for his help and advice on statistical analyses. This work was partly funded by Natural Research Limited and a Natural Environment Research Council studentship NE/J500148/1 to SH and grant NE/F021402/1 to XL. Forest Research funded all the fieldwork on goshawks, tawny owls and field voles during 1973-1996. In addition, we are grateful to English Nature and the BTO for issuing licences to visit goshawk nest sites.Peer reviewedPublisher PD

Photoregulated hydrazone-based hydrogel formation for biochemically patterning 3D cellular microenvironments

\u3cp\u3ePhotodriven click reactions have emerged as versatile tools for biomaterial synthesis that can recapitulate critical spatial and temporal changes of extracellular matrix (ECM) microenvironments in vitro. In this article, we report on the synthesis of poly(ethylene glycol) (PEG) hydrogels using photodriven step-growth polymerization, where one of the reactive functionalities is formed by a photocleavage reaction. Upon photocleavage, an aldehyde functionality is generated that rapidly reacts with hydrazine-functionalized PEGs; the gelation kinetics and final material modulus are distinctly controlled by variations in the light intensity. This light-driven aldehyde generation is further exploited to install biochemical ligands in the hydrazone-based hydrogels with precise spatial control. We expect that user-directed spatial and temporal control over both biophysical and biochemical gel properties through photochemical reactions and photopatterning, respectively, should provide newfound opportunities to probe and understand dynamic cell-matrix interactions.\u3c/p\u3

A supramolecular platform stabilizing growth factors

High concentrations of supplemented growth factors can cause oversaturation and adverse effects in in vitro and in vivo studies. Though, these supraphysiological concentrations are often required due to the low stability of growth factors. Here we demonstrate the stabilization of TGF-β1 and BMP4 using supramolecular polymers. Inspired by heparan sulfate, sulfonated peptides were presented on a supramolecular polymer to allow for non-covalent binding to growth factors in solution. After mixing with excipient molecules, both TGF-β1 and BMP4 were shown to have a prolonged half-life compared to the growth factors free in solution. Moreover, high cellular response was measured by a luciferase assay, indicating that TGF-β1 remained highly active upon binding to the supramolecular assembly. The results demonstrate that significant lower concentrations of growth factors can be used when supramolecular polymers bearing growth factor binding moieties are implemented. This approach can also be exploited in hydrogel systems to control growth factor release

A supramolecular platform stabilizing growth factors

\u3cp\u3eHigh concentrations of supplemented growth factors can cause oversaturation and adverse effects in in vitro and in vivo studies. Though, these supraphysiological concentrations are often required due to the low stability of growth factors. Here we demonstrate the stabilization of TGF-β1 and BMP4 using supramolecular polymers. Inspired by heparan sulfate, sulfonated peptides were presented on a supramolecular polymer to allow for non-covalent binding to growth factors in solution. After mixing with excipient molecules, both TGF-β1 and BMP4 were shown to have a prolonged half-life compared to the growth factors free in solution. Moreover, high cellular response was measured by a luciferase assay, indicating that TGF-β1 remained highly active upon binding to the supramolecular assembly. The results demonstrate that significant lower concentrations of growth factors can be used when supramolecular polymers bearing growth factor binding moieties are implemented. This approach can also be exploited in hydrogel systems to control growth factor release.\u3c/p\u3

Cardiac progenitor cells and the interplay with their microenvironment

The microenvironment plays a crucial role in the behavior of stem and progenitor cells. In the heart, cardiac progenitor cells (CPCs) reside in specific niches, characterized by key components that are altered in response to a myocardial infarction. To date, there is a lack of knowledge on these niches and on the CPC interplay with the niche components. Insight into these complex interactions and into the influence of microenvironmental factors on CPCs can be used to promote the regenerative potential of these cells. In this review, we discuss cardiac resident progenitor cells and their regenerative potential and provide an overview of the interactions of CPCs with the key elements of their niche. We focus on the interaction between CPCs and supporting cells,\u3cbr/\u3eextracellular matrix, mechanical stimuli, and soluble factors. Finally, we describe novel approaches to modulate the CPC niche that can represent the next step in recreating an optimal CPC microenvironment and thereby improve their regeneration capacity

Effectiveness of cell adhesive additives in different supramolecular polymers

Supramolecular motifs in elastomeric biomaterials facilitate the modular incorporation of additives with corresponding motifs. The influence of the elastomeric supramolecular base polymer on the presentation of additives has been sparsely examined, limiting the knowledge of transferability of effective functionalization between polymers. Here it was investigated if the polymer backbone and the additive influence biomaterial modification in two different types of hydrogen bonding supramolecular systems, that is, based on ureido-pyrimidinone or bis-urea units. Two different cell-adhesive additives, that is, catechol or cyclic RGD, were incorporated into different elastomeric polymers, that is, polycaprolactone, priplast or polycarbonate. The additive effectiveness was evaluated with three different cell types. AFM measurements showed modest alterations on nano-scale assembly in ureido-pyrimidinone materials modified with additives. On the contrary, additive addition was highly intrusive in bis-urea materials. Detailed cell adhesive studies revealed additive effectiveness varied between base polymers and the supramolecular platform, with bis-urea materials more potently affecting cell behavior. This research highlights that additive transposition might not always be as evident. Therefore, additive effectiveness requires re-evaluation in supramolecular biomaterials when altering the polymer backbone to suit the biomaterial application

Supramolecular Platform Stabilizing Growth Factors

High concentrations of supplemented growth factors can cause oversaturation and adverse effects in <i>in vitro</i> and <i>in vivo</i> studies, though these supraphysiological concentrations are often required due to the low stability of growth factors. Here we demonstrate the stabilization of TGF-β1 and BMP4 using supramolecular polymers. Inspired by heparan sulfate, sulfonated peptides were presented on a supramolecular polymer to allow for noncovalent binding to growth factors in solution. After mixing with excipient molecules, both TGF-β1 and BMP4 were shown to have a prolonged half-life compared to the growth factors free in solution. Moreover, high cellular response was measured by a luciferase assay, indicating that TGF-β1 remained highly active upon binding to the supramolecular assembly. The results demonstrate that significant lower concentrations of growth factors can be used when supramolecular polymers bearing growth factor binding moieties are implemented. This approach can also be exploited in hydrogel systems to control growth factor release