TY - JOUR
T1 - Lifetimes of complexes of the antibiotic x-537a (lasalocid a) with physiological cations in methanol. Determination by NMR using a dissociative shift reagent
AU - Krishnan, C. V.
AU - Friedman, H. L.
AU - Springer, C. S.
N1 - Funding Information:
The research described here was made possible by grant from the National institutes of Health.
PY - 1978/11
Y1 - 1978/11
N2 - Using a magnetic resonance method we have determined the lifetimes of the following complexes of X-537A (HX) in methanol solution at 25° C, BaX+, 132 μs; SrX+, 34 μs; CaX+, 24 μs, and KX, 15 μs, each with an estimated uncertainty of 30%. For NaX and LiX the lifetimes are too short to measure by the present method, The lifetime found for BaX+ is considerably shorter than the result obtained by Patel and Shen using a different method. The present method depends upon the broadening of the resonance lines of certain protons in X- due to reactions such as X- + Ba2+ = BaX+, when the resonance of the proton in the "free" X- has been shifted from its normal frequency by Pr(III) which acts via the exchange PrX3 ⇌ PrX+2 + X-. To determine the lifetimes of interest the equations for a three-state spin system were derived; under the relevant conditions the final equations take the form of the Swift-Connick equations for a two-state system, with the characteristics of one of the states dependent upon the PrX3 concentration. This dependence is used to extract the life-times from the data in a novel and simple way.
AB - Using a magnetic resonance method we have determined the lifetimes of the following complexes of X-537A (HX) in methanol solution at 25° C, BaX+, 132 μs; SrX+, 34 μs; CaX+, 24 μs, and KX, 15 μs, each with an estimated uncertainty of 30%. For NaX and LiX the lifetimes are too short to measure by the present method, The lifetime found for BaX+ is considerably shorter than the result obtained by Patel and Shen using a different method. The present method depends upon the broadening of the resonance lines of certain protons in X- due to reactions such as X- + Ba2+ = BaX+, when the resonance of the proton in the "free" X- has been shifted from its normal frequency by Pr(III) which acts via the exchange PrX3 ⇌ PrX+2 + X-. To determine the lifetimes of interest the equations for a three-state spin system were derived; under the relevant conditions the final equations take the form of the Swift-Connick equations for a two-state system, with the characteristics of one of the states dependent upon the PrX3 concentration. This dependence is used to extract the life-times from the data in a novel and simple way.
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U2 - 10.1016/0301-4622(78)87012-4
DO - 10.1016/0301-4622(78)87012-4
M3 - Article
C2 - 753401
AN - SCOPUS:0018068234
SN - 0301-4622
VL - 9
SP - 23
EP - 35
JO - Biophysical Chemistry
JF - Biophysical Chemistry
IS - 1
ER -