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Acylpeptide hydrolases (APH; also known as acylamino acid releasing enzyme) catalyze the removal of an N-acylated amino acid from blocked peptides. The crystal structure of an APH from the thermophilic archaeon Aeropyrum pernix K1 to 2.1 A resolution confirms it to be a member of the prolyl oligopeptidase family of serine proteases. The structure of apAPH is a symmetric homodimer with each subunit comprised of two domains. The N-terminal domain is a regular seven-bladed beta-propeller, while the C-terminal domain has a canonical alpha/beta hydrolase fold and includes the active site and a conserved Ser445-Asp524-His556 catalytic triad. The complex structure of apAPH with an organophosphorus substrate, p-nitrophenyl phosphate, has also been determined. The complex structure unambiguously maps out the substrate binding pocket and provides a basis for substrate recognition by apAPH. A conserved mechanism for protein degradation from archaea to mammals is suggested by the structural features of apAPH.

Mesocellular silica foam (MCF) materials with different pore volumes were prepared and modified with tetraethylenepentamine (TEPA) as sorbents for CO2 capture. The as-prepared sorbents were characterized by XRD, TEM, SEM, nitrogen adsorption/desorption, and FTIR. CO2 capture performances of the adsorbents were tested in a fixed-bed reactor equipped with an online MS. The results indicated that the pore volume of supports has great effect on the CO2 capture performance. With the increasing of pore volume as well as the window and cell sizes of the MCF, more TEPA can be loaded into the pores of MCF. For MCF with larger pore volume, more unoccupied space is left after the same amount of TEPA was loaded into the pores. The unoccupied space is beneficial for higher CO2 uptake because the mass transfer limitation can be reduced to some extent and the interaction between CO2 and TEPA may be easier. MCF material with largest pore volume exhibited the largest CO2 uptake of 4.34 mmol/g of adsorbent with a 70 wt % TEPA loading tested by the fixed-bed reactor and at least 4.57 mmol/g tested by thermogravimetric analysis (TGA) under the conditions of 10.0% (v/v) CO2 in N2 at 75 °C. Repeated adsorption/desorption cycles revealed that its high CO2 capacity can be regenerated via temperature swing adsorption and so it may be useful for CO2 capture via TEPA functionalized MCFs.

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