Sirtuins are NAD-dependent deacetylases that regulate important biological processes. Mammals have seven sirtuins, Sirt1-7. Four of them (Sirt4-7) have no detectable or very weak deacetylase activity. Here we found that Sirt5 is an efficient protein lysine desuccinylase and demalonylase in vitro. The preference for succinyl and malonyl groups was explained by the presence of an arginine residue (Arg105) and tyrosine residue (Tyr102) in the acyl pocket of Sirt5. Several mammalian proteins were identified to have succinyl or malonyl lysine modifications by mass spectrometry. Deletion of Sirt5 in mice appeared to increases the level of succinylation on carbamoyl phosphate synthase 1, a known target of Sirt5. Thus protein lysine succinylation may represent a posttranslational modification that can be reversed by Sirt5 in vivo.

A series of high-capacity, amine impregnated sorbents based on a cost-effective silica foam with ultralarge mesopores is reported. The sorbents exhibit fast CO 2 capture kinetics, high adsorption capacity (of up to 5.8 mmol g À1 under 1 atm of dry CO 2 ), as well as good stability over multiple adsorptiondesorption cycles. A simple theoretical analysis is provided relating the support structure to sorbent performance.

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