Biophysical Reviews and Letters

Protein mechanics is a key component of many cellular and sub-cellular processes. The current review focuses on recent studies from our laboratory that probe the effect of sequence on the mechanical stability of structurally similar proteins and the unfolding mechanisms of multi-domain periplasmic binding proteins. Ubiquitin and small ubiquitin-related modifiers (SUMOs) are structurally similar and possess different mechanical stabilities, ubiquitin being stronger than SUMOs as revealed from their unfolding forces. These differences are plausibly due to the variation in number of inter-residue contacts. The unfolding potential widths determined from the pulling speed-dependent studies revealed that SUMOs are mechanically more flexible than ubiquitin. This flexibility of SUMOs plays a role in ligand binding and our single-molecule studies on SUMO interaction with SUMO binding motifs (SBMs) have shown that ligand binding decreases the SUMO flexibility and increases its mechanical stability. Studies on multi-domain periplasmic binding proteins have revealed that the unfolding energy landscape of these proteins is complex and they follow kinetic partitioning between two-state and multiple three-state pathways.

The effect of electromagnetic irradiation with extremely high radio frequencies on several parameters of albumin water-saline solutions has been studied and the changes invoked by this irradiation after long time of its effect were observed. It was shown that the electromagnetic irradiation with 51.8GHz frequency, which is resonant for water, is preserved up to 48h after which the system returns to the initial state. It was shown as well that albumin thermostability also enhances and it is preserved during 48h, after that the system tends to return to the initial state.

In this paper we have proposed and analyzed a simple three-dimensional mathematical model related to malaria disease. We consider three state variables associated with susceptible human population, infected human population and infected mosquitoes, respectively. A discrete delay parameter has been incorporated to take account of the time of incubation period with infected mosquitoes. We consider the effect of insecticide control, which is applied to the mosquitoes. Basic reproduction number is figured out for the proposed model and it is shown that when this threshold is less than unity then the system moves to the disease-free state whereas for higher values other than unity, the system would tend to an endemic state. On the other hand if we consider the system with delay, then there may exist some cases where the endemic equilibrium would be unstable although the numerical value of basic reproduction number may be greater than one. We formulate and solve the optimal control problem by considering insecticide as the control variable. Optimal control problem assures to obtain better result than the noncontrol situation. Numerical illustrations are provided in support of the theoretical results.