No abstract

Biopolymeric micelles derived from bioinspired amphiphilic polymers are drawing noteworthy attention as carriers for hydrophobic drugs since they possess a hydrophobic core and a hydrophilic cell. Herein, a hydrophobic monomer N-Boc glycine-hydroxy methyl methacrylate (Gly-HEMA) has been synthesized by chemical modification of N-Boc glycine. This monomer has further been grafted through reversible addition–fragmentation chain transfer (RAFT) polymerization on the backbone of sodium alginate (hydrophilic) to obtain an amphiphilic copolymer with an attached hydrophobic segment. The controlled polymerization is assessed using advanced polymer chromatographic (APC) analysis with a narrow dispersity. The critical micelle concentration (CMC) of the developed copolymer [i.e., Alg-g-p­(Gly-HEMA)] has been determined by surface tension measurement and photoluminescence (PL) spectroscopic and dynamic light scattering (DLS) analyses. The size and morphology of the developed micelle have been investigated by field emission scanning electron microscopy (FESEM) and high-resolution transmission electron microscopy (HRTEM) analyses, which reveal that the size of the copolymeric micelle is ∼200 nm with a spherical shape. Alg-g-p­(Gly-HEMA) has demonstrated pH-responsive reversible micellization behavior. The process of micellization to phase separation and vice versa can be controlled just by altering the pH. The formed micelle is able to uptake the hydrophobic drug indomethacin (% of loading: ∼34%) and release it in a controlled manner, as apparent from an in vitro study.

MexAB-OprM efflux pumps, found in Pseudomonas aeruginosa, play a major role in drug resistance by extruding out drugs and antibiotic molecules from cells. Inhibitors are used to cease the potency of the efflux pumps. In this study, in-silico models are used to investigate the nature of the binding pocket of the MexAB-OprM efflux pump. First, we have performed classical molecular dynamics (MD) simulations to shed light on different aspects of protein-inhibitor interaction in the binding pocket of the pump. Using classical MD simulations, quantum mechanics/ molecular mechanics (QM/MM), and various types of analyses, it is found that D13-9001 has a higher binding affinity towards the binding pocket compared to D1 and D2; the results are in sync with the experimental dat. Two stable configurations of D13-9001 are discovered inside the distal pocket which could be one of the primary reasons for the greater efficacy of D13-9001. The free energy barrier upon changing one state to another is calculated by employing umbrella sampling method. Finally, F178 is mutated to have the complete picture as it contributes significantly to the binding energy irrespective of the three inhibitors. Our results may help to design a new generation of inhibitors for such an efflux pump.

Mutations in multi‐domain leucine‐rich repeat kinase 2 (LRRK2) have been an interest to researchers as these mutations are associated with Parkinson's disease. G2019S mutation in LRRK2 kinase domain leads to the formation of  additional hydrogen bonds by S2019 which results in stabilization of the active state of the kinase, thereby increasing kinase activity. Two additional hydrogen bonds of S2019 are reported separately. Here, a mechanistic picture of the formation of additional hydrogen bonds of  S2019 with Q1919 (also with E1920) was presented using ‘active’ Roco4 kinase as a homology model and its relation with the stabilization of the ‘active’ G2019S LRRK2 kinase. A conformational‐flipping of residue Q1919 was found which helped to form stable hydrogen bond with S2019 and made ‘active’ state more stable in G2019S LRRK2. Two different states were found within ‘active’ kinase with respect to the conformational change (flipping) in Q1919. Two doubly‐mutated systems, G2019S/Q1919A and G2019S/E1920K, were studied separately to check the effect of Q1919 and E1920. For both cases, the stable S2 state was not formed, leads to a decrease in kinase activity. These results that both the additional hydrogen bonds of S2019 (with Q1919 and E1920) were necessary to stabilize the active G2019S LRRK2.