Correcting for incomplete saturation and off-resonance effects in multiple-site saturation-transfer kinetic measurements |
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Authors: | Kingsley P B Monahan W G |
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Institution: | Department of Radiology, North Shore University Hospital, 300 Community Drive, Manhasset, New York, 11030 USA. kingsley@nshs.edu |
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Abstract: | The effects of incomplete saturation and off-resonance irradiation on nuclear magnetic resonance saturation-transfer measurements of three-site chemical-exchange rates are discussed. A new method that uses double-saturation measurements is compared with two published methods, one that uses single-saturation measurements and one that uses a single-saturation measurement and a double-saturation measurement. Several formulas are compared for measuring the exchange rate constant k(DE) for exchange from a detected spin D to an exchanging spin E in the presence of exchange from spin D to a competing spin C. For each method, formulas are derived with corrections for incomplete saturation or off-resonance effects, with both corrections, and with neither correction. Exact formulas are available for three exchanging sites with incomplete saturation if there are no off-resonance effects. Off-resonance corrections are imperfect even with complete saturation. |
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