Conformational Dynamics of Calixarenes. Kinetics of Conformational Interconversion in 5,11,17,23-Tetra-p-tert-butyl-25,26,27,28-tetramethoxycalix[4]arene under Entropic Control

1994 ◽  
Vol 116 (26) ◽  
pp. 11957-11960 ◽  
Author(s):  
Johan Blixt ◽  
Christian Detellier
Keyword(s):  
Conformational Dynamics ◽  
Tert Butyl ◽  
Conformational Interconversion ◽  
Kinetics Of

Thermodynamic and Kinetic Investigation of the Solvent Effect on the Oxidation of [Co(en)2SCH2COO]+ with S2O82- In Water-Methanol and Water-tert-Butyl Alcohol Mixtures

1993 ◽  
Vol 58 (5) ◽  
pp. 1001-1006 ◽  
Author(s):  
Oľga Vollárová ◽  
Ján Benko
Keyword(s):  
Transfer Functions ◽  
Activation Parameters ◽  
Butyl Alcohol ◽  
Oxidation Of Co ◽  
Kinetics Of Oxidation ◽  
Tert Butyl ◽  
Tert Butyl Alcohol ◽  
Alcohol Mixtures ◽  
Kinetics Of

The kinetics of oxidation of [Co(en)2SCH2COO]+ with S2O82- was studied in water-methanol and water-tert-butyl alcohol mixtures. Changes in the reaction activation parameters ∆H≠ and ∆S≠ with varying concentration of the co-solvent depend on the kind of the latter, which points to a significant role of salvation effects. The solvation effect on the reaction is discussed based on a comparison of the transfer functions ∆Ht0, ∆St0 and ∆Gt0 for the initial and transition states with the changes in the activation parameters accompanying changes in the CO-solvent concentration. The transfer enthalpies of the reactant were obtained from calorimetric measurements.

Conformational dynamics and pre-steady-state kinetics of DNA glycosylases

2010 ◽  
Vol 75 (10) ◽  
pp. 1225-1239 ◽  
Author(s):  
O. S. Fedorova ◽  
N. A. Kuznetsov ◽  
V. V. Koval ◽  
D. G. Knorre
Keyword(s):  
Steady State ◽  
Conformational Dynamics ◽  
Dna Glycosylases ◽  
Steady State Kinetics ◽  
Kinetics Of

scholarly journals Oversized galactosides as a probe for conformational dynamics in LacY

2018 ◽  
Vol 115 (16) ◽  
pp. 4146-4151 ◽  
Author(s):  
Irina Smirnova ◽  
Vladimir Kasho ◽  
Xiaoxu Jiang ◽  
Hong-Ming Chen ◽  
Stephen G. Withers ◽  
...  
Keyword(s):  
Binding Site ◽  
Conformational Dynamics ◽  
Dissociation Rate ◽  
Binding Kinetics ◽  
Lactose Permease ◽  
E Coli ◽  
Open Conformation ◽  
Dissociation Rate Constants ◽  
Kinetics Of ◽  
Micromolar Range

Binding kinetics of α-galactopyranoside homologs with fluorescent aglycones of different sizes and shapes were determined with the lactose permease (LacY) of Escherichia coli by FRET from Trp151 in the binding site of LacY to the fluorophores. Fast binding was observed with LacY stabilized in an outward-open conformation (kon = 4–20 μM−1·s−1), indicating unobstructed access to the binding site even for ligands that are much larger than lactose. Dissociation rate constants (koff) increase with the size of the aglycone so that Kd values also increase but remain in the micromolar range for each homolog. Phe27 (helix I) forms an apparent constriction in the pathway for sugar by protruding into the periplasmic cavity. However, replacement of Phe27 with a bulkier Trp does not create an obstacle in the pathway even for large ligands, since binding kinetics remain unchanged. High accessibility of the binding site is also observed in a LacY/nanobody complex with partially blocked periplasmic opening. Remarkably, E. coli expressing WT LacY catalyzes transport of α- or β-galactopyranosides with oversized aglycones such as bodipy or Aldol518, which may require an extra space within the occluded intermediate. The results confirm that LacY specificity is strictly directed toward the galactopyranoside ring and also clearly indicate that the opening on the periplasmic side is sufficiently wide to accommodate the large galactoside derivatives tested here. We conclude that the actual pathway for the substrate entering from the periplasmic side is wider than the pore diameter calculated in the periplasmic-open X-ray structures.

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