Chemistry Letters
Online ISSN : 1348-0715
Print ISSN : 0366-7022
ISSN-L : 0366-7022
Volume 40 , Issue 4
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  • Shin-ichi Ozaki, Akira Nakahara, Takehiro Sato
    2011 Volume 40 Issue 4 Pages 362-363
    Published: April 05, 2011
    Released: March 02, 2011
    JOURNALS OPEN ACCESS
    Heme acquisition system A (HasA), secreted by various gram-negative pathogens, uses a unique histidine–iron–tyrosine (His–Fe–Tyr) coordination to scavenge heme (i.e., protoporphyrin IX–Fe complex) as an iron source. In order to study heme uptake by HasA, we utilized axial ligand mutants and protoporphyrin IX. Our results suggest that the binding of heme in apoprotein is initiated by interactions between heme and hydrophobic residues in the heme pocket. Subsequently, the sequential coordination of Tyr-75 and His-32 with the iron appears to complete holoprotein formation.
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  • Mizuki Nakajima, Kun Qiao, Nobuhisa Kobayashi, Quanxi Bao, Daisuke Tom ...
    2011 Volume 40 Issue 4 Pages 396-397
    Published: April 05, 2011
    Released: March 12, 2011
    JOURNALS OPEN ACCESS
    A Lewis acid ionic liquid, 1-[4-(chlorosulfonyl)butyl]-3-methylimidazolium chlorosulfate ([CBMIm]SO3Cl), with Lewis acid sites in both the anion and cation was synthesized. This was demonstrated to be an efficient catalyst for dehydration of aldoximes to nitriles. An unexpected self-induced phase separation of the reaction mixture was observed when the reaction was carried out in acetonitrile. This could be attributed to the hydrolysis of [CBMIm]SO3Cl to regenerate 1-(4-sulfobutyl)-3-methylimidazolium hydrogensulfate ([SBMIm]HSO4), which was the Brønsted precursor of [CBMIm]SO3Cl.
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