Hydrogen-Bonded Structure of Ion Pairs of Ammonium Salts as Deduced from Proton-Exchange Rates

1965 ◽  
Vol 87 (9) ◽  
pp. 2070-2071 ◽  
Author(s):  
Michael Cocivera ◽  
Ernest Grunwald
Keyword(s):  
Exchange Rates ◽  
Ion Pairs ◽  
Proton Exchange ◽  
Ammonium Salts ◽  
Hydrogen Bonded

Effect of peptide binding on amide proton exchange rates in the PDZ2 domain from human phosphatase hPTP1E

1998 ◽  
Vol 76 (2-3) ◽  
pp. 334-340 ◽  
Author(s):  
Irena Ekiel ◽  
Denis Banville ◽  
Shi Hsiang Shen ◽  
Kalle Gehring
Keyword(s):  
Exchange Rates ◽  
Ph Dependence ◽  
Guanidine Hydrochloride ◽  
Peptide Binding ◽  
Fluorescence Emission ◽  
Proton Exchange ◽  
Amide Proton ◽  
Amide Proton Exchange ◽  
C Terminus ◽  
Amide Exchange

Amide hydrogen-deuterium exchange rates were measured in the PDZ2 domain from human phosphatase hPTP1E by 1H-15N heteronuclear NMR spectroscopy. Protection factors were calculated for the slowly exchanging hydrogens in both the free PDZ2 domain and its complex with an octapeptide peptide, R-N-E-I-Q-S-L-V, derived from the C-terminus of the Fas receptor. Aside from a short α-helical region α1 (amino acids A-45 to D-49), the pattern of highly protected amides correlated well with the presence of hydrogen bonds in elements of the secondary structure. Hydrogen-bonded amides showed relatively fast exchange rates with half-lives of less than 9 h at pD 7.6 and 8°C. Protection factors, calculated as the ratio of theoretical (denatured) and observed exchange rates, showed less dispersion in maximal values than did the actual exchange rates. This behavior and the large pH dependence of the exchange rates suggest that amide exchange is close to the EX2 limit. In this limit, exchange of the most protected amides occurs through a global unfolding mechanism. The free energy of the unfolding calculated from the largest protection factors is 4.8 ± 0.4 kcal/mol (1 cal = 4.184 J). This ΔG° closely matches the value measured by experiments with guanidine hydrochloride and fluorescence emission spectroscopy. Peptide binding to PDZ2 resulted in mostly global effects and stabilized the folded domain by 1.4 kcal/mol.Key words: PDZ2 from hPTP1E, amide exchange, ligand binding, NMR.

scholarly journals Amide proton exchange rates of oxidized and reduced saccharomyces cerevisiae iso-1-cytochrome c

1993 ◽  
Vol 2 (11) ◽  
pp. 1966-1974 ◽  
Author(s):  
Jennifer L. Marmorino ◽  
Douglas S. Auld ◽  
Stephen F. Betz ◽  
Donald F. Doyle ◽  
Gregory B. Young ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cytochrome C ◽  
Exchange Rates ◽  
Proton Exchange ◽  
Amide Proton ◽  
Amide Proton Exchange

The log kexovs. log kendo correlation as a mechanistic criterion; on the mechanisms of solvolysis of norbornyl derivatives and base-catalyzed isotope exchange of norbornanones

1976 ◽  
Vol 54 (5) ◽  
pp. 678-684 ◽  
Author(s):  
Sujit Banerjee ◽  
Nick Henry Werstiuk
Keyword(s):  
Transition State ◽  
Exchange Rates ◽  
Isotope Exchange ◽  
Transition States ◽  
Substituent Effects ◽  
Proton Exchange ◽  
Hydrogen Deuterium Exchange ◽  
Rate Data ◽  
Hydrogen Deuterium ◽  
The Difference

Rate data for the acetolysis of exo-norbornyl-sulfonates have been correlated with those for the corresponding endo isomers. It is shown that the slopes of the log kexovs. log kendo plots reflect the difference in delocalization between the transition states derived from the exo and endo isomers, respectively. The log kexovs. log kendo plot, which is comprised of the parent norbornyl sufonate and its derivatives substituted at the 5, 6, and 7 positions, has a slope of 1.11 ± 0.08, which establishes that σ bridging is absent in the transition state obtained from the exo isomer. A similar analysis of base-catalyzed hydrogen–deuterium exchange rates of norbornanones reveals that exo proton exchange is more sensitive to substituent effects than the corresponding endo process.

Proton-exchange rates in solid tropolone as measured via carbon-13 CP/MAS NMR

1983 ◽  
Vol 105 (9) ◽  
pp. 2579-2582 ◽  
Author(s):  
Nikolaus M. Szeverenyi ◽  
Ad Bax ◽  
Gary E. Maciel
Keyword(s):  
Exchange Rates ◽  
Proton Exchange ◽  
Mas Nmr ◽  
Cp Mas Nmr
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