We suggest a physical mechanism by which antimicrobial peptides spontaneously induce stable pores in membranes. Peptide binding to a lipid bilayer causes an internal stress, or internal membrane tension, that can be sufficiently strong to create pores. Like detergents, peptides have a high affinity for the rim of the pore. Binding to the rims reduces the line tension and decreases the number of...

in assisted reproduction techniques (art) settings, reactive oxygen species (ros) can be produced from endogenous and exogenous sources during in vitro manipulation. endogenous sources of ros include gametes and embryo, whereas exogenous sources are oxygen tension, light exposure, culture media, and the nature of some protocols, such as centrifugation or cryopreservation. elevated ros productio...

In order to face environmental constraints, trees are able to re-orient their axes by controlling the stress level in the newly formed wood layers. Angiosperms and gymnosperms evolved into two distinct mechanisms: the former produce a wood with large tension pre-stress on the upper side of the tilted axis, while the latter produce a wood with large compression pre-stress on the lower side. In b...

This article gives an overview of recent research on the mechanical properties and spatial deformations of the DNA molecule. Globally the molecule behaves like a uniform elastic rod, and its twisting and writhing govern its compaction and packaging within a cell. Meanwhile high mechanical stresses can induce structural transitions of DNA giving, for example, a phase diagram in the space of the ...

Previous studies have shown that hindlimb unweighting of rats, a model of microgravity, reduces evoked contractile tension of peripheral conduit arteries. It has been hypothesized that this diminished contractile tension is the result of alterations in the mechanical properties of these arteries (e.g., active and passive mechanics). Therefore, the purpose of this study was to determine whether ...

Wolff's "law" of the functional adaptation of bone is rooted in the trajectory hypothesis of cancellous bone architecture. Wolff often used the human proximal femur as an example of a trajectorial structure (i.e. arched trabecular patterns appear to be aligned along tension/compression stress trajectories). We examined two tenets of the trajectory hypothesis; namely, that the trabecular tracts ...

The normal stress distribution across a slip plane has the effect of reducing the critical loading required for dislocation emission from a crack tip. The reduction by normal stresses was found to be very significant for Si, based on properties estimated for it using density functional theory, to be large for Fe as modeled by the embedded atom method (EAM), and to be smaller in AI, Ni and order...

Mechanical responses to stretch and length-tension relations were examined in rabbit taenia coli, mesenteric vein, aorta, and myometrium and in guinea pig taenia coli made atonic by incubation in Krebs-bicarbonate solution at 20-22 degrees C. When stretched 10% of the length at which maximum active tension is observed (Lo) in 0.5 s, the muscles showed a transient large force (resistance to stre...

To explore the role of titin filaments in muscle elasticity, we measured the resting tension-sarcomere length curves of six rabbit skeletal muscles that express three size classes of titin isoform. The stress-strain curves of the split fibers of these muscles displayed a similar multiphasic shape, with an exponential increase in tension at low sarcomere strain followed by a leveling of tension ...