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  1. Free, publicly-accessible full text available December 17, 2022
  2. Protein–protein interactions are essential for life but rarely thermodynamically quantified in living cells. In vitro efforts show that protein complex stability is modulated by high concentrations of cosolutes, including synthetic polymers, proteins, and cell lysates via a combination of hard-core repulsions and chemical interactions. We quantified the stability of a model protein complex, the A34F GB1 homodimer, in buffer,Escherichia colicells andXenopus laevisoocytes. The complex is more stable in cells than in buffer and more stable in oocytes thanE. coli. Studies of several variants show that increasing the negative charge on the homodimer surface increases stability in cells. These data, takenmore »together with the fact that oocytes are less crowded thanE. colicells, lead to the conclusion that chemical interactions are more important than hard-core repulsions under physiological conditions, a conclusion also gleaned from studies of protein stability in cells. Our studies have implications for understanding how promiscuous—and specific—interactions coherently evolve for a protein to properly function in the crowded cellular environment.

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  3. A unique chain-rupturing transformation that converts an ether functionality into two hydrocarbyl units and carbon monoxide is reported, mediated by iridium( i ) complexes supported by aminophenylphosphinite (NCOP) pincer ligands. The decarbonylation, which involves the cleavage of one C–C bond, one C–O bond, and two C–H bonds, along with formation of two new C–H bonds, was serendipitously discovered upon dehydrochlorination of an iridium( iii ) complex containing an aza-18-crown-6 ether macrocycle. Intramolecular cleavage of macrocyclic and acyclic ethers was also found in analogous complexes featuring aza-15-crown-5 ether or bis(2-methoxyethyl)amino groups. Intermolecular decarbonylation of cyclic and linear ethers was observed whenmore »diethylaminophenylphosphinite iridium( i ) dinitrogen or norbornene complexes were employed. Mechanistic studies reveal the nature of key intermediates along a pathway involving initial iridium( i )-mediated double C–H bond activation.« less