More Like this

1. Distinct Bimetallic Cooperativity Among Water Reduction Catalysts Containing [Co III Co III ], [Ni II Ni II ], and [Zn II Zn II ] Cores

   https://doi.org/10.1002/chem.202104426  

   Morgan, Fredricka ; Schaugaard, Richard ; Anderson, Dennis ; Schlegel, H. Bernhard ; Verani, Cláudio N. ( March 2022 , Chemistry – A European Journal)

   Three binuclear species [LCo^III₂(μ‐Pz)₂](ClO₄)₃(1), [LNi^II₂(CH₃OH)₂Cl₂]ClO₄(2), and [LZn^II₂Cl₂]PF₆(3) supported by the deprotonated form of the ligand 2,6‐bis[bis(2‐pyridylmethyl) amino‐methyl]‐4‐methylphenol were synthesized, structurally characterized as solids and in solution, and had their electrochemical and spectroscopic behavior established. Species1–3had their water reduction ability studied aiming to interrogate the possible cooperative catalytic activity between two neighboring metal centers. Species1and2reduced H₂O to H₂effectively at an applied potential of −1.6 V_Ag/AgCl, yielding turnover numbers of 2,820 and 2,290, respectively, after 30 minutes. Species3lacked activity and was used as a negative control to eliminate the possibility of ligand‐based catalysis. Pre‐ and post‐catalytic data gave evidence of the molecular nature of the process within the timeframe of the experiments. Species1showed structural, rather than electronic cooperativity, while species2displayed no obvious cooperativity. DFT methods complemented the experimental results determining plausible mechanisms.

    

   more » « less
2. Anomalous mechanics of Zn 2+ -modified fibrin networks

   https://doi.org/10.1073/pnas.2020541118  

   Xia, Jing ; Cai, Li-Heng ; Wu, Huayin ; MacKintosh, Frederick C. ; Weitz, David A. ( March 2021 , Proceedings of the National Academy of Sciences)

   Fibrin is the main component of blood clots. The mechanical properties of fibrin are therefore of critical importance in successful hemostasis. One of the divalent cations released by platelets during hemostasis is Zn²⁺; however, its effect on the network structure of fibrin gels and on the resultant mechanical properties remains poorly understood. Here, by combining mechanical measurements with three-dimensional confocal microscopy imaging, we show that Zn²⁺can tune the fibrin network structure and alter its mechanical properties. In the presence of Zn²⁺, fibrin protofibrils form large bundles that cause a coarsening of the fibrin network due to an increase in fiber diameter and reduction of the total fiber length. We further show that the protofibrils in these bundles are loosely coupled to one another, which results in a decrease of the elastic modulus with increasing Zn²⁺concentrations. We explore the elastic properties of these networks at both low and high stress: At low stress, the elasticity originates from pulling the thermal slack out of the network, and this is consistent with the thermal bending of the fibers. By contrast, at high stress, the elasticity exhibits a common master curve consistent with the stretching of individual protofibrils. These results show that the mechanics of a fibrin network are closely correlated with its microscopic structure and inform our understanding of the structure and physical mechanisms leading to defective or excessive clot stiffness.

    

   more » « less
3. Zn 2+ Binds to Phosphatidylserine and Induces Membrane Blebbing

   https://doi.org/10.1021/jacs.0c09103  

   Poyton, Matthew F. ; Pullanchery, Saranya ; Sun, Simou ; Yang, Tinglu ; Cremer, Paul S. ( October 2020 , Journal of the American Chemical Society)

   null (Ed.)
4. Zn 2+ influx activates ERK and Akt signaling pathways

   https://doi.org/10.1073/pnas.2015786118  

   Anson, Kelsie J. ; Corbet, Giulia A. ; Palmer, Amy E. ( March 2021 , Proceedings of the National Academy of Sciences)

   Zinc (Zn²⁺) is an essential metal in biology, and its bioavailability is highly regulated. Many cell types exhibit fluctuations in Zn²⁺that appear to play an important role in cellular function. However, the detailed molecular mechanisms by which Zn²⁺dynamics influence cell physiology remain enigmatic. Here, we use a combination of fluorescent biosensors and cell perturbations to define how changes in intracellular Zn²⁺impact kinase signaling pathways. By simultaneously monitoring Zn²⁺dynamics and kinase activity in individual cells, we quantify changes in labile Zn²⁺and directly correlate changes in Zn²⁺with ERK and Akt activity. Under our experimental conditions, Zn²⁺fluctuations are not toxic and do not activate stress-dependent kinase signaling. We demonstrate that while Zn²⁺can nonspecifically inhibit phosphatases leading to sustained kinase activation, ERK and Akt are predominantly activated via upstream signaling and through a common node via Ras. We provide a framework for quantification of Zn²⁺fluctuations and correlate these fluctuations with signaling events in single cells to shed light on the role that Zn²⁺dynamics play in healthy cell signaling.

    

   more » « less
5. Photoresponsive Zn 2+ -specific metallohydrogels coassembled from imidazole containing phenylalanine and arylazopyrazole derivatives

   https://doi.org/10.1039/d0dt01809k  

   Sallee, Ashanti ; Ghebreyessus, Kesete ( August 2020 , Dalton Transactions)

   null (Ed.)

   Stimuli-responsive supramolecular gels and metallogels have been widely explored in the past decade, but the fabrication of metallogels with reversible photoresponsive properties remains largely unexplored. In this study, we report the construction of photoresponsive hybrid zinc-based metallohydrogel systems coassembled from an imidazole functionalized phenylalanine derivative gelator (ImF) and carboxylic acid functionalized arylazopyrazole (AzoPz) molecular photoswitches in the presence of Zn 2+ ions. Unlike traditional covalent conjugation, noncovalent introduction of small molecular switches into the gel matrix provides a convenient route to generate photoresponsive functional materials with tunable properties and expands the scope of optically controlled molecular self-assemblies. It has been found that the carboxylic acid functionalized AzoPz derivatives alone or mixed with the ImF moiety could not self-assemble to form any gels. However, in the presence of Zn 2+ ions they readily formed the coassembled hybrid metallogels in an alkaline aqueous solution with various morphologies. These results suggest that the gelation process was triggered by the Zn 2+ ions. In addition, the ImF gelator shows specific response to Zn 2+ ions only. The presence of the AzoPz moiety in the gel matrix makes the metallogel coassemblies photoresponsive and the reversible gel-to-sol phase transition was studied by UV-vis spectroscopy. The gels showed a slow reversible light-induced gel-to-sol phase transition under UV ( λ = 365 nm) and then sol-to-gel transition by green light ( λ = 530) irradiation resulting in the reformation of the original gel state. The morphology and viscoelastic properties of the fibrillar opaque metallogels have been characterized by transmission electron microscopy (TEM) and rheological measurement, respectively. 

   more » « less