3019-85-0Relevant articles and documents
Binding and catalytic properties of 2-0-and 3-o-permethylated cyclodextrins
Nagata, Takuya,Yoshikiyo, Keisuke,Matsui, Yoshihisa,Yamamoto, Tatsuyuki
, p. 196 - 201 (2009)
Hexakis(3-0-methyl)-α,-cyclodextrin (3α) bound tom-and p-nitrophenolate ions more strongly, whereas hexakis(2-0-methy1)-α- cyclodextrin (2α) bound less strongly than native α-cyclodextrin. ROESY spectra showed that the 3-0-mefhyl groups of 3a interact with the guest protons, whereas 2-0-methyl groups of 2a do not. 3a accelerated and 2a decelerated the cleavage of m-nitrophenyl acetate in an alkaline solution, suggesting that the C(2)-OH of α-cyclodextrin is more catalytic than the C(3)-OH. However, the catalytic effect of 3a was much smaller than that of native a-cyclodextrin. Loss of hydrogen bonding between the C(3)-OH and C(2)-OH by 3-O-permethylation is responsible for the small catalytic effects of 3α. Similar results were obtained for β-cyclodextrin analogs.
Synthesis and isolation of non-chromophore cage-rearranged silsesquioxanes from base-catalyzed reactions
Hanprasit, Sasikarn,Tungkijanansin, Nuttanee,Prompawilai, Arisa,Eangpayung, Supattra,Ervithayasuporn, Vuthichai
supporting information, p. 16117 - 16120 (2016/10/31)
The nucleophilicity of both ortho- and meta-nitrophenolate anions is strong enough to give substituted products, but their basicity also facilitates cage-rearrangement reactions in polyhedral oligomeric silsesquioxanes (POSS). Anions having a stronger basicity, but weaker nucleophilicity, such as CO32-, gave products only from cage-rearrangement, with the cage expansion products being isolable in multi-gram quantities using conventional column chromatography.
Do electrostatic interactions with positively charged active site groups tighten the transition state for enzymatic phosphoryl transfer?
Nikolic-Hughes, Ivana,Rees, Douglas C.,Herschlag, Daniel
, p. 11814 - 11819 (2007/10/03)
The effect of electrostatic interactions on the transition-state character for enzymatic phosphoryl transfer has been a subject of much debate. In this work, we investigate the transition state for alkaline phosphatase (AP) using linear free-energy relationships (LFERs). We determined fcat/K M for a series of aryl sulfate ester monoanions to obtain the Bronsted coefficient, βIg, and compared the value to that obtained previously for a series of aryl phosphorothioate ester dianion substrates. Despite the difference in substrate charge, the observed Bronsted coefficients for AP-catalyzed aryl sulfate and aryl phosphorothioate hydrolysis (-0.76 ± 0.14 and -0.77 ± 0.10, respectively) are strikingly similar, with steric effects being responsible for the uncertainties in these values. Aryl sulfates and aryl phosphates react via similar loose transition states in solution. These observations suggest an apparent equivalency of the transition states for phosphorothioate and sulfate hydrolysis reactions at the AP active site and, thus, negligible effects of active site electrostatic interactions on charge distribution in the transition state.
