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Carbonic anhydrase (CA) is an ultrafast enzyme that catalyzes the reversible conversion of carbon dioxide (CO2) to bicarbonate. CA is considered to be a green catalyst for enzyme-based CO2 capture and utilization. In particular, the CA of Thermovibrio ammonificans (taCA) has attracted increasing attention as a highly stable enzyme. However, the poor solubility and the low expression level in Escherichia coli have hampered further utilization of taCA. In a recent study, these limitations were partly resolved by using a small solubility-enhancing fusion tag named NEXT, which originates from the N-terminal extension of Hydrogenovibrio marinus CA. In this study, the NEXT tag was engineered by adding small peptides to the N terminus to further increase the production yield of NEXT-tagged taCA. The addition of ng3 peptide (His-Gly-Asn) originating from the N-terminal sequence of Neisseria gonorrhoeae CA improved the expression of NEXT-taCA, while the previously developed translation-enhancing element (TEE) and Ser-Lys-Ile-Lys (SKIK) tag were not effective. The expression test with all 16 codon combinations for the ng3 sequence revealed that the change in translation initiation rate brought about by the change in nucleotide sequence was not the primary determinant for the change in expression level. The modified ng3-NEXT tag may be applied to increase the production yields of various recombinant proteins.

Microwave dielectric properties of CaW 1−x (Mo 1/2 Te 1/2) x O 4 (0.01 ≤ x ≤ 0.17) ceramics with (Mo 1/2 Te 1/2) 6+ substitution were investigated. For the specimens sintered at 825-950 °C for 3 h, a single phase of a scheelite structure was observed up to x = 0.13, while secondary phases were detected above x = 0.17. The relative densities of the specimens were higher than 95%, and the grain morphologies were uniform and clean for the entire range of compositions. The quality factor (Qf) depended on the intrinsic factors such as the W-site bond characteristics of CaWO 4 evaluated by the bond valence and degree of covalency, and confirmed by the full width at half maximum of the internal mode peak of Raman spectroscopy. However, Qf was also affected by the extrinsic factors, such as the formation of the secondary phases, which showed the maximum Qf value (167,800 GHz) at x = 0.13 and then decreased. The dielectric constant (K) increased with (Mo 1/2 Te 1/2) 6+ substitution, which was affected by the dielectric polarizabilities of constituent ions. As the (Mo 1/2 Te 1/2) 6+ content increased, the temperature coefficient of resonant frequency (TCF) decreased, which was associated with an increase of oxygen bond valence.