I t is rare that a fully functional biological system presents a simple biophysical problem. The problem of viral DNA packaging comes tantalizingly close: What forces are required to stuff double-stranded DNA of fixed length into a container of fixed volume? Now that biophysicists have developed the capability to measure such forces, theoretical solutions to this problem can be directly tested,...

Abstract The Coulomb barrier is a classic introductory physics concept and one that key to understanding nuclear fusion. Yet the idea fusing nuclei within single system could exhibit both far-range repulsion short-range attraction can result in significant cognitive dissonance students. There are no classical examples of this behaviour commercially available demonstration kits. magnetic ‘Coulom...

A physical model of selective "ion binding" in the L-type calcium channel is constructed, and consequences of the model are compared with experimental data. This reduced model treats only ions and the carboxylate oxygens of the EEEE locus explicitly and restricts interactions to hard-core repulsion and ion-ion and ion-dielectric electrostatic forces. The structural atoms provide a flexible envi...

We study an artificial spin ice system consisting of two identical layers separated by a height offset $h$. For small separation, the are shown to attract each other, provided whole is in ground state. Such attraction comes about means power-law force that we compare van der Waals forces. When magnetic monopoles occur one (or both) layers, scenario becomes even more interesting and these may al...

We study the Brownian motion of a charged colloid, confined between two walls, for small separation colloid and walls. The system is embedded in an ionic solution. combined effect electrostatic repulsion reduced diffusion due to hydrodynamic forces results specific direction perpendicular confining apparent coefficient at short times as well characteristic time are shown follow sigmoid curve fu...

Topological defects are one of the most conspicuous features liquid crystals. In two dimensional nematics, they have been shown to behave effectively as particles with both, charge and orientation, which dictate their interactions. Here, we study "twisted" that a radially dependent orientation. We find twist can be partially relaxed through creation annihilation defect pairs. By solving equatio...

The description of forces across confined complex fluids still holds many challenges due to the possible overlap different contributions. Here, an attempt is made untangle interaction between charged surfaces nanoparticle suspensions. Interaction are measured using colloidal-probe atomic force microscopy. experimental profiles considered as a superposition double layer and structural forces. In...

Adsorption of Bovine Serum Albumin (BSA) onto calcium Hydroxyl Apatite (HA), Ca10PO4(OH)2, has been studied by Ultra Violet (UV) spectroscopy. The adsorption isotherms of BSA onto the HA surface at 291.7 K and 303.2 K were satisfactorily presented by Langmuir equation and the evaluated parameters are reported. The specific surface area of H...

Adsorbed layers of pancreatic RNase A on molecularly smooth mica in aqueous solution attract inorganic mica surfaces whereas they repel similarly adsorbed RNase A layers. As the clean mica surface is covered with RNase A, the attractive interaction slowly diminishes with time and eventually converts to a purely repulsive interaction. Solvent is squeezed out of the solution in the gap during com...