RESUMEN
We investigate the dynamics of clusters made of aggregating particles on a membrane which exchanges particles with a reservoir. Exchanges are driven by chemical reactions which supply energy to the system, leading to the establishment of a non-equilibrium steady state. We predict the distribution of cluster size at steady state. We show in particular that in a regime, that cannot exist at equilibrium, the distribution is bimodal: the membrane is mainly populated of single particles and finite-size clusters. This work is motivated by the observations that have revealed the existence of submicrometric clusters of proteins in biological membranes.
Asunto(s)
Biofisica/métodos , Membrana Celular/metabolismo , Proteínas/química , Adenosina Trifosfato/química , Adsorción , Animales , Análisis por Conglomerados , Citosol/metabolismo , GTP Fosfohidrolasas/química , Guanosina Difosfato/química , Cinética , Microdominios de Membrana/química , Modelos Estadísticos , Unión Proteica , Conformación Proteica , Temperatura , TermodinámicaRESUMEN
Cutaneous melanoma is disproportionately lethal despite its relatively low incidence and its potential for cure in the early stages. The aim of this study is to foster understanding of the role of microstructure on the occurrence of morphological changes in diseased skin during melanoma evolution. The authors propose a biomechanical analysis of its radial growth phase, investigating the role of intercellular/stromal connections on the initial stages of epidermis invasion. The radial growth phase of a primary melanoma is modelled within the multi-phase theory of mixtures, reproducing the mechanical behaviour of the skin layers and of the epidermal-dermal junction. The theoretical analysis takes into account those cellular processes that have been experimentally observed to disrupt homeostasis in normal epidermis. Numerical simulations demonstrate that the loss of adhesiveness of the melanoma cells both to the basal laminae, caused by deregulation mechanisms of adherent junctions, and to adjacent keratynocytes, consequent to a downregulation of E-cadherin, are the fundamental biomechanical features for promoting tumour initiation. Finally, the authors provide the mathematical proof of a long wavelength instability of the tumour front during the early stages of melanoma invasion. These results open the perspective to correlate the early morphology of a growing melanoma with the biomechanical characteristics of its micro-environment.
Asunto(s)
Epidermis/metabolismo , Epidermis/fisiopatología , Melanoma/metabolismo , Melanoma/fisiopatología , Modelos Biológicos , Neoplasias Cutáneas/metabolismo , Neoplasias Cutáneas/fisiopatología , Uniones Adherentes/metabolismo , Uniones Adherentes/patología , Cadherinas/metabolismo , Epidermis/patología , Homeostasis , Humanos , Melanoma/patología , Invasividad Neoplásica , Proteínas de Neoplasias/metabolismo , Neoplasias Cutáneas/patologíaRESUMEN
We propose a unifying, analytical theory accounting for the self-organization of colloidal systems in nanocluster or microcluster phases. We predict the distribution of cluster sizes with respect to interaction parameters and colloid concentration. In particular, we anticipate a proportionality regime where the mean cluster size grows proportionally to the concentration, as observed in several experiments. We emphasize the interest in a predictive theory in soft matter, nanotechnologies, and biophysics.
RESUMEN
We study a simple model for an amphiphilic layer that may adsorb cosurfactant molecules from a reservoir. Upon varying the length of the cosurfactant, we obtain a discontinuous change of the adsorption rate and a corresponding discontinuity of the bending rigidity kappa. With realistic values for the chemical potential and the interaction energy of the hydrophobic tails, our model accounts quantitatively for the measured rigidity and the discontinuity observed for the ternary system AOT/water/oil and for SDS/alcohol bilayers.