Can visco-elastic phase separation, macromolecular crowding and colloidal physics explain nuclear organisation?

BACKGROUND: The cell nucleus is highly compartmentalized with well-defined domains, it is not well understood how this nuclear order is maintained. Many scientists are fascinated by the different set of structures observed in the nucleus to attribute functions to them. In order to distinguish functional compartments from non-functional aggregates, I believe is important to investigate the biophysical nature of nuclear organisation. RESULTS: The various nuclear compartments can be divided broadly as chromatin or protein and/or RNA based, and they have very different dynamic properties. The chromatin compartment displays a slow, constrained diffusional motion. On the other hand, the protein/RNA compartment is very dynamic. Physical systems with dynamical asymmetry go to viscoelastic phase separation. This phase separation phenomenon leads to the formation of a long-lived interaction network of slow components (chromatin) scattered within domains rich in fast components (protein/RNA). Moreover, the nucleus is packed with macromolecules in the order of 300 mg/ml. This high concentration of macromolecules produces volume exclusion effects that enhance attractive interactions between macromolecules, known as macromolecular crowding, which favours the formation of compartments. In this paper I hypothesise that nuclear compartmentalization can be explained by viscoelastic phase separation of the dynamically different nuclear components, in combination with macromolecular crowding and the properties of colloidal particles. CONCLUSION: I demonstrate that nuclear structure can satisfy the predictions of this hypothesis. I discuss the functional implications of this phenomenon

The perceptions of social responsibility for community resilience to flooding: the impact of past experience, age, gender and ethnicity

Community resilience to flooding depends, to a large extent, on the participation of community members to take more responsibility for enhancing their own resilience. The perception of social responsibility (SR) which is argued to be one of the antecedents influencing individual’s willingness to undertake resilient behaviours can significantly contribute to community resilience through individual and collective actions. Understanding of factors influencing the perceptions of SR of individuals within community might help with developing strategies to increase the perceptions of SR. This research explores perceptions of SR in relation to flooding for householders and local businesses and establishes their relationships with experience of flooding and demographic factors of age, gender and ethnicity. The data were obtained via a questionnaire survey of three communities in Birmingham and one community in South East London, UK, three with experience of flooding and one without. A total of 414 responses were received and used in the multiple regression analysis. The analysis identified ‘experience of flooding’, ‘age’ and ‘South Asian’ ethnic group as significant variables, suggesting that older individuals from South Asian ethnic groups with previous experience of flooding are likely to be more socially responsible than others without these attributes

The robustness of flood insurance regimes given changing risk resulting from climate change

The changing risk of flooding associated with climate change presents different challenges for the different flood insurance market models in use around the world, which vary in respect of consumer structure and their risk transfer mechanism. A review of international models has been undertaken against three broad criteria for the functioning and sustainability of a flood insurance scheme: knowing the nature of the insurable risk; the availability of an insurable population; and the presence of a solvent insurer. The solvency of insurance markets appears strong, partly because insurers and reinsurers can choose to exclude markets which would give rise to insolvency or can diversify their portfolios to include offsetting perils. Changing risk may threaten solvency if increasing risk is not recognised and adjusted for but insurability of flood risk may be facilitated by the use of market based and hybrid schemes offering greater diversification and more flexibility. While encouragement of mitigation is in theory boosted by risk based pricing, availability and affordability of insurance may be negatively impacted. This threatens the sustainability of an insurable population, therefore the inclusion of the state in partnership is beneficial in ensuring continuity of cover, addressing equity issues and incentivising mitigation