Comprehensive Analysis of the Chemical and Structural Transformations of Mg-Al-CO3 Layered Double Hydroxides with Different Mg/Al Ratios at Elevated Temperatures

Mg-Al layered double hydroxides (LDHs) with CO32- interlayer anions are promising CO2 adsorbents. Here, we analyzed the quantitative gas evolution behaviors of Mg-Al LDH particles with different Mg/Al ratios during the multistep chemical/structural transformations at elevated temperatures. The Mg/Al molar ratio strongly affects the behavior: the transformation changes from two apparent steps to three steps depending on the Mg/Al ratio. The transformation occurs in essentially the same way as that observed for large Mg-Al LDH crystals: (1) release of the interlayer water, (2) partial dehydroxylation of the hydroxyl layers followed by coordination of carbonate ions to the metals, and (3) collapse of the layered structure. We provide a molecular/atomic level picture of the structure in each step of the transformation by first-principles density functional theory (DFT) calculation. The structurally optimized model and reexamination of experimental data showed that step (1) results in a large decrease in the interlayer distance of the LDH from ∼7.6 to ∼6.7 Å (a decrease of ∼0.9 Å) and the possible explanation is the waving of the metal hydroxide layers. This study provides a comprehensive understanding of the structural changes of LDHs with various Mg/Al ratios to resolve the various interpretations in the literature.

Complete nucleotide sequence of a new potexvirus, 'Cnidium virus X', isolated from Cnidium officinale in Japan

A flexuous virus was detected in a Cnidium officinale plant in Japan showing mosaic symptoms. The virus was assigned to the genus Potexvirus based on analysis of its complete nucleotide sequence. The genomic RNA of the virus was 5,964 nucleotides in length, excluding the 3'-terminal poly(A) tail. It contained five open reading frames (ORFs), consistent with other members of Potexvirus. The ORF sequences differ from those of previously reported potexviruses. Phylogenetic analysis indicated that the polymerase of the virus is closely related to that of strawberry mild yellow edge virus; and the CP, to those of both yam virus X and vanilla virus X. We propose that this virus be designated as "cnidium virus X" (CnVX).