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Nuclear magnetic relaxation studies of BH4 in metal Borohydrides
Kim Chul,Ku Jessie,Hwang Son‐Jong,Bowman Robert C.,Reiter Joseph W. 대한화학회 2021 Bulletin of the Korean Chemical Society Vol.42 No.11
A different approach of nuclear magnetic resonance (NMR) relaxation of the rotational motion of BH4 tetrahedron in light metal borohydrides was introduced. Previous NMR relaxation studies were mainly performed using an approximation which is based on a single exponential transition approach for the spin–lattice relaxation of the spin under quadrupolar interaction. In this new approach, a relaxation rate equation was derived by strictly taking into account both electric quadrupolar and magnetic dipolar contributions to the transitions between Zeeman energy states of quadrupolar 11B nucleus that was coupled to many proton spins. Two exponential relaxation times derived from our theoretical treatment were applied to the analysis of 11B spin–lattice relaxation of LiBH4 and Ca(BH4)2. The activation energies and the correlation times of the reorientational motions of BH4 were evaluated from the two experimental spin–lattice relaxation times. The results were compared to previous activation energies and correlation times.
Comparative Analysis of the Conserved Functions of Arabidopsis DRL1 and Yeast KTI12
Jun, Sang Eun,Cho, Kiu-Hyung,Hwang, Ji-Young,Abdel-Fattah, Wael,Hammermeister, Alexander,Schaffrath, Raffael,Bowman, John L.,Kim, Gyung-Tae Korean Society for Molecular and Cellular Biology 2015 Molecules and cells Vol.38 No.3
Patterning of the polar axis during the early leaf developmental stage is established by cell-to-cell communication between the shoot apical meristem (SAM) and the leaf primordia. In a previous study, we showed that the DRL1 gene, which encodes a homolog of the Elongator-associated protein KTI12 of yeast, acts as a positive regulator of adaxial leaf patterning and shoot meristem activity. To determine the evolutionally conserved functions of DRL1, we performed a comparison of the deduced amino acid sequence of DRL1 and its yeast homolog, KTI12, and found that while overall homology was low, well-conserved domains were presented. DRL1 contained two conserved plant-specific domains. Expression of the DRL1 gene in a yeast KTI12-deficient yeast mutant suppressed the growth retardation phenotype, but did not rescue the caffeine sensitivity, indicating that the role of Arabidopsis Elongator-associated protein is partially conserved with yeast KTI12, but may have changed between yeast and plants in response to caffeine during the course of evolution. In addition, elevated expression of DRL1 gene triggered zymocin sensitivity, while overexpression of KTI12 maintained zymocin resistance, indicating that the function of Arabidopsis DRL1 may not overlap with yeast KTI12 with regards to toxin sensitivity. In this study, expression analysis showed that class-I KNOX genes were downregulated in the shoot apex, and that YAB and KAN were upregulated in leaves of the Arabidopsis drl1- 101 mutant. Our results provide insight into the communication network between the SAM and leaf primordia required for the establishment of leaf polarity by mediating histone acetylation or through other mechanisms.