Rational Design of Potent Inhibitors of a Metallohydrolase Using a Fragment-Based Approach

Metallohydrolases form a large group of enzymes that have fundamental importance in a broad range of biological functions. Among them, the purple acid phosphatases (PAPs) have gained attention due to their crucial role in the acquisition and use of phosphate by plants and also as a promising target for novel treatments of bone-related disorders and cancer. To date, no crystal structure of a mammalian PAP with drug-like molecules bound near the active site is available. Herein, we used a fragment-based design approach using structures of a mammalian PAP in complex with the Maybridge^TM fragment CC063346, the amino acid L-glutamine and the buffer molecule HEPES, as well as various solvent molecules to guide the design of highly potent and efficient mammalian PAP inhibitors. These inhibitors have improved aqueous solubility when compared to the clinically most promising PAP inhibitors available to date. Furthermore, drug-like fragments bound in newly discovered binding sites mapped out additional scaffolds for further inhibitor discovery, as well as scaffolds for the design of inhibitors with novel modes of action.     

Combined Effects of Confinement and Macromolecular Crowding on Protein Stability

Confinement and crowding have been shown to affect protein fates, including folding, functional stability, and their interactions with self and other proteins. Using both theoretical and experimental studies, researchers have established the independent effects of confinement or crowding, but only a few studies have explored their effects in combination; therefore, their combined impact on protein fates is still relatively unknown. Here, we investigated the combined effects of confinement and crowding on protein stability using the pores of agarose hydrogels as a confining agent and the biopolymer, dextran, as a crowding agent. The addition of dextran further stabilized the enzymes encapsulated in agarose; moreover, the observed increases in enhancements (due to the addition of dextran) exceeded the sum of the individual enhancements due to confinement and crowding. These results suggest that even though confinement and crowding may behave differently in how they influence protein fates, these conditions may be combined to provide synergistic benefits for protein stabilization. In summary, our study demonstrated the successful use of polymer-based platforms to advance our understanding of how in vivo like environments impact protein function and structure.     

Numerical,wind-tunnel,and atmospheric evaluation of a turbulent ground-based inlet sampling system

The use of inlets for transferring aerosols from the environment to instrumentation can introduce uncertainty in the measurement of aerosol properties. Aerosol loss during this process is a non-negligible issue that may bias the subsequent measurements. These loss mechanisms include aspiration at the inlet head and deposition/evaporation/condensation during transport through the sampling lines. Coarse-mode aerosol is significantly impacted by the aspiration and inertial loss mechanisms within an inlet system. This work uses wind tunnel experiments to investigate aerosol losses through the Storm Peak Laboratory’s (SPL) new aerosol inlet system. The inlet is used extensively for both intensive field campaigns and long-term aerosol monitoring. The results of numerical simulations of the SPL aerosol inlet sampling efficiency are provided at several wind speeds, and experimental results demonstrate the system has a 50% cut off for the coarse-mode at an aerodynamic diameter of approximately 13?μm and wind speed of 0.5?m s^?1. This investigation will lead to improved accuracy of in situ aerosol measurements at SPL and this system can be replicated at other atmospheric stations.

Copyright © 2019 American Association for Aerosol Research     

Structural and Biochemical Studies of Actin in Complex with Synthetic Macrolide Tail Analogues

The actin filament‐binding and filament‐severing activities of the aplyronine, kabiramide, and reidispongiolide families of marine macrolides are located within the hydrophobic tail region of the molecule. Two synthetic tail analogues of aplyronine C (SF‐01 and GC‐04) are shown to bind to G‐actin with dissociation constants of (285±33) and (132±13) nM , respectively. The crystal structures of actin complexes with GC‐04, SF‐01, and kabiramide C reveal a conserved mode of tail binding within the cleft that forms between subdomains (SD) 1 and 3. Our studies support the view that filament severing is brought about by specific binding of the tail region to the SD1/SD3 cleft on the upper protomer, which displaces loop‐D from the lower protomer on the same half‐filament. With previous studies showing that the GC‐04 analogue can sever actin filaments, it is argued that the shorter complex lifetime of tail analogues with F‐actin would make them more effective at severing filaments compared with plasma gelsolin. Structure‐based analyses are used to suggest more reactive or targetable forms of GC‐04 and SF‐01, which may serve to boost the capacity of the serum actin scavenging system, to generate antibody conjugates against tumor cell antigens, and to decrease sputum viscosity in children with cystic fibrosis.