179 research outputs found
Effects of confinement on thermal stability and folding kinetics in a simple Ising-like model
In cellular environment, confinement and macromulecular crowding play an
important role on thermal stability and folding kinetics of a protein. We have
resorted to a generalized version of the Wako-Saito-Munoz-Eaton model for
protein folding to study the behavior of six different protein structures
confined between two walls. Changing the distance 2R between the walls, we
found, in accordance with previous studies, two confinement regimes: starting
from large R and decreasing R, confinement first enhances the stability of the
folded state as long as this is compact and until a given value of R; then a
further decrease of R leads to a decrease of folding temperature and folding
rate. We found that in the low confinement regime both unfolding temperatures
and logarithm of folding rates scale as R-{\gamma} where {\gamma} values lie in
between 1.42 and 2.35
Rigorous results on the local equilibrium kinetics of a protein folding model
A local equilibrium approach for the kinetics of a simplified protein folding
model, whose equilibrium thermodynamics is exactly solvable, was developed in
[M. Zamparo and A. Pelizzola, Phys. Rev. Lett. 97, 068106 (2006)]. Important
properties of this approach are (i) the free energy decreases with time, (ii)
the exact equilibrium is recovered in the infinite time limit, (iii) the
equilibration rate is an upper bound of the exact one and (iv) computational
complexity is polynomial in the number of variables. Moreover, (v) this method
is equivalent to another approximate approach to the kinetics: the path
probability method. In this paper we give detailed rigorous proofs for the
above results.Comment: 25 pages, RevTeX 4, to be published in JSTA
Optimality in Self-Organized Molecular Sorting
We introduce a simple physical picture to explain the process of molecular sorting, whereby specific proteins are concentrated and distilled into submicrometric lipid vesicles in eukaryotic cells. To this purpose, we formulate a model based on the coupling of spontaneous molecular aggregation with vesicle nucleation. Its implications are studied by means of a phenomenological theory describing the diffusion of molecules toward multiple sorting centers that grow due to molecule absorption and are extracted when they reach a sufficiently large size. The predictions of the theory are compared with numerical simulations of a lattice-gas realization of the model and with experimental observations. The efficiency of the distillation process is found to be optimal for intermediate aggregation rates, where the density of sorted molecules is minimal and the process obeys simple scaling laws. Quantitative measures of endocytic sorting performed in primary endothelial cells are compatible with the hypothesis that these optimal conditions are realized in living cells
Glued to your phone? Generation Z's smartphone addiction and online compulsive buying
Recent studies found that smartphone usage has become an addiction nowadays, especially among young consumers. The abuse of these digital devices affects individuals' social life and well-being. Of particular interest in this regard is the study of compulsive buying, as it has been noted a possible co-occurrence of this disorder with smartphone abusive tendencies. With a model theoretically anchored in the stimulus-organism-response framework, the current study investigates the novel connection between smartphone addiction and online compulsive buying in a sample of 275 Generation Z consumers. The proposed model integrates mood regulatory behaviours and flow experiences associated with smartphone addiction to affect online compulsive buying behaviours. The current research contributes to the literature on compulsive buying behaviours and smartphone addiction by offering empirical evidence that (1) smartphone addiction and online compulsive buying are related; and (2) mood regulatory behaviours and flow experience act as strengthening factors in this relationship. This article advances knowledge in terms of theory and practice on Generation Z consumers’ smartphone addiction and online compulsive buying
Inversion of the balance between hydrophobic and hydrogen bonding interactions in protein folding and aggregation.
Identifying the forces that drive proteins to misfold and aggregate, rather than to fold into their functional states, is fundamental to our understanding of living systems and to our ability to combat protein deposition disorders such as Alzheimer's disease and the spongiform encephalopathies. We report here the finding that the balance between hydrophobic and hydrogen bonding interactions is different for proteins in the processes of folding to their native states and misfolding to the alternative amyloid structures. We find that the minima of the protein free energy landscape for folding and misfolding tend to be respectively dominated by hydrophobic and by hydrogen bonding interactions. These results characterise the nature of the interactions that determine the competition between folding and misfolding of proteins by revealing that the stability of native proteins is primarily determined by hydrophobic interactions between side-chains, while the stability of amyloid fibrils depends more on backbone intermolecular hydrogen bonding interactions
Pacing and Decision Making in Sport and Exercise: The Roles of Perception and Action in the Regulation of Exercise Intensity
In pursuit of optimal performance, athletes and physical exercisers alike have to make decisions about how and when to invest their energy. The process of pacing has been associated with the goal-directed regulation of exercise intensity across an exercise bout. The current review explores divergent views on understanding underlying mechanisms of decision making in pacing. Current pacing literature provides a wide range of aspects that might be involved in the determination of an athlete's pacing strategy, but lacks in explaining how perception and action are coupled in establishing behaviour. In contrast, decision-making literature rooted in the understanding that perception and action are coupled provides refreshing perspectives on explaining the mechanisms that underlie natural interactive behaviour. Contrary to the assumption of behaviour that is managed by a higher-order governor that passively constructs internal representations of the world, an ecological approach is considered. According to this approach, knowledge is rooted in the direct experience of meaningful environmental objects and events in individual environmental processes. To assist a neuropsychological explanation of decision making in exercise regulation, the relevance of the affordance competition hypothesis is explored. By considering pacing as a behavioural expression of continuous decision making, new insights on underlying mechanisms in pacing and optimal performance can be developed. © 2014 Springer International Publishing Switzerland
Longitudinal intra- and inter-individual variability in young swimmers' performance and determinant competition factors
Canottaggio
il canotaggio \ue8 l'attivit\ue0 fisica del remare, praticata su imbarcazioni leggere, condotte da singoli atleti o da equipaggi. In questa voce \ue8 riportato un riassunto delle conoscenze attuali di bion\uecmeccanica e bioenergetica della vog
Il costo energetico: fattori che lo determinano
Il costo energetico del nuoto (C) è definito
come l’energia spesa per coprire una
determinata distanza; per produrre un’elevata
velocità, C dovrebbe essere il minore
possibile. C dipende dalla resistenza
idrodinamica (Wd: è vantaggioso avere un
valore basso), dall’efficienza propulsiva
(ηp) e dall’efficienza totale (ηo) (è vantaggioso
avere questi due valori alti). Sfortunatamente,
questi parametri sono piuttosto
difficili da misurare e i metodi finora proposti
in letteratura per misurare/calcolare
questi fattori danno risultati molto diversi
tra loro
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