Study of Moderately Rapid Chemical Exchange Reactions by Means of Nuclear Magnetic Double Resonance

Forsén, Sture; Hoffman, Ragnar A.

doi:10.1063/1.1734121

Cited by 1,191 publications

(629 citation statements)

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“…3), an equilibrium reaction is considered where k AB and k BA are first-order rate constants for the forward and backward reaction, respectively. Initiated by the pioneering work of Forsen and Hoffman, 6 the majority of kinetic formalisms describe saturation transfer from pool B to pool A.…”

Section: Basic Theory Models Measurement Methodsmentioning

confidence: 99%

“…The original saturation transfer technique, 6 which was used in the first in vivo MT experiments both for MRI 11 and MRS, 12 was cw off-resonance preirradiation, where rf preirradiation is done with a constant amplitude ! 2 = B 2 and an offset frequency D = D!/2p during t t .…”

Section: Basic Theory Models Measurement Methodsmentioning

confidence: 99%

“…Historically the first polarization transfer experiment was performed by Forsen and Hoffmann, 6 who studied the chemical exchange of protons between salicylaldehyde (site A) and 2-Hydroxyacetophenone (site B) (Fig. 1).…”

Section: Introductionmentioning

confidence: 99%

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Magnetization transfer MRS

Leibfritz¹,

Dreher²

2001

NMR in Biomedicine

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This review deals with magnetization transfer (MT) effects observed in in vivo NMR spectroscopy. The basic experimental methods of MT experiments, the underlying kinetic mechanisms as well as the evaluation of measured data by fits to two-or three-pool models are described. Experimental results of both 31 P and 1 H in vivo MRS are reviewed showing the potential of MT experiments to characterize kinetic equilibrium reactions. This includes reactions where all involved components are MR visible, as well as situations where one indirectly measures pools of bound spins which cannot directly be observed in vivo. In particular, MT effects are described which have been observed in in vivo 1 H NMR spectra measured on the animal or human brain or on skeletal muscle. Possible mechanisms for the strong MT effects observed for the signals of creatine/phosphocreatine, lactate, alcohol and other metabolites are discussed. It is also emphasized that MT effects caused by water suppression techniques may lead to systematic errors in the quantification of in vivo 1 H NMR spectra.

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Section: Basic Theory Models Measurement Methodsmentioning

confidence: 99%

Section: Basic Theory Models Measurement Methodsmentioning

confidence: 99%

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Magnetization transfer MRS

Leibfritz¹,

Dreher²

2001

NMR in Biomedicine

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“…Hydrogen exchange rates were determined by measuring the transfer of saturation of the amide proton signals from the H20 resonance as a function of pH (Forsen & Hoffman, 1963, 1964Krishna et al, 1979). The pH of the sample was adjusted to the desired value with HCl or NaOH and a one-dimensional proton spectrum acquired at 500 MHz with 1.5 s of pre-irradiation of the water resonance, an acquisition time of 1 s, a sweep width of 6,500 Hz, eight steady state pulses and 128 transients co-added.…”

Section: Nmr Studiesmentioning

confidence: 99%

The orientation and dynamics of substance P in lipid environments

Keire

Kobayashi

1998

Protein Science

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The membrane-associated conformation of substance P (RPKPQQFFGLM-NH2) has been previously proposed to be the NKI-receptor-active conformation. In this work, NMR methods are applied to explore the orientation and dynamics of substance P at lipid surfaces for which the peptide's three-dimensional structure had been previously determined. Here the presence of dodecylphosphocholine (DPC) or sodium dodecylsulfate (SDS) micelles has been found to cause sequence specific changes in the acid-and base-catalyzed amide proton exchange rates relative to the solution state values. On binding of substance P to SDS micelles, the FFG portion showed the largest decreases in the base-catalyzed amide exchange rates. Similar sequence-specific changes in substance P are observed in the presence of DPC micelles, albeit at much weaker levels due to fast exchange between free and bound forms of the peptide. These differences are attributed to the location of the amide protons either in the surface double layer (via electrostatic effect) or inserted into the polar head group region of the micelles (via low dielectric). The sequence-specific effects of micelle association were also observed in the homonuclear nonselective spin-lattice relaxation time; these, in combination with spin-spin relaxation times, were used to calculate correlation times for the backbone amide protons. These data combined with paramagnetic broadening observations on peptide protons in the presence of spin-labeled lipids yield a detailed model of the interaction of substance P with lipid surfaces.Keywords: amide exchange; correlation times; dodecylphosphocholine; NMR; peptide-lipid interactions; sodium dodecylsulfate; substance P; TI and T2 relaxation Substance P (SP) is a member of the tachykinin family of neuropeptides and is widely distributed in both the central and peripheral nervous system of humans. Tachykinins, which are characterized by a common C-terminal tail (F-x-GLM-NH2 where x is F or V for mammals), are of biomedical interest because they have been shown to cause hypotension, contraction of smooth muscles, salivation, transmission of pain, and inflammation (Pernow, 1983). Ligands of SP receptors have potential as a novel class of anti-inflammatory or pain medication, and as a result, interest is high in the structural elements of the peptide that may control receptor activity and selectivity.The membrane-bound conformation of SP has been proposed to be the NK1 receptor active form (Schwyzer, 1995), and the three-dimensional structure of SP in the presence of Abbreviations: DPC, dodecylphosphocholine; RMSD, root-mean-square deviation; SDS, sodium dodecylsulfate; SP, substance P; 2D TOCSY, twodimensional total correlation spectroscopy. 1996). Both structures were similar, although fast exchange between free and bound forms was observed for SP with DPC micelles and predominantly bound characteristics were found for SP with SDS micelles.The three-dimensional SP structure at these lipid-membrane mimetics may represent either a receptor-bound co...

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“…Leu 23, Leu 71, and lle 88 N-H correlations are not observed in the HSQC spectrum of Pdx'. where TI is the longitudinal relaxation time of the resonance, tis the length of time for which the water resonance is saturated, MP is the signal intensity at f = 0, and k, is the rate constant for chemical exchange of the observed proton with the irradiated species (Forsen & Hoffman, 1963;Skelton et al, 1992). When the irradiation time t is long with respect to TI, Equation l simplifies to Equation 2:…”

Section: Bmentioning

confidence: 99%

Redox‐dependent dynamics of putidaredoxin characterized by amide proton exchange

Lyons¹,

Ratnaswamy²,

Pochapsky³

1996

Protein Science

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Multidimensional NMR methods were used to obtain 'H-I'N correlations and "N resonance assignments for amide and side-chain nitrogens of oxidized and reduced putidaredoxin (Pdx), the Fe2S2 ferredoxin, which acts as the physiological reductant of cytochrome P-450,,, (CYPlOl). A model for the solution structure of oxidized Pdx has been determined recently using NMR methods (Pochapsky TC, Ye XM, Ratnaswamy G, Lyons TA, 1994, Biochemistry 33:6424-6432) and redox-dependent ' H NMR spectral features have been described (Pochapsky TC, Ratnaswamy G, Patera A, 1994, Biochemistry33:6433-6441). "N assignments were made with NOESY-('H/''N) HMQC and TOCSY-('H/''N) HSQC spectra obtained using samples of Pdx uniformly labeled with "N. Local dynamics in both oxidation states of Pdx were then characterized by comparison of residue-specific amide proton exchange rates, which were measured by a combination of saturation transfer and H 2 0 / D 2 0 exchange methods at pH 6.4 and 7.4 (uncorrected for isotope effects). In general, where exchange rates for a given site exhibit significant oxidation-state dependence, the oxidized protein exchanges more rapidly than the reduced protein. The largest dependence of exchange rate upon oxidation state is found for residues near the metal center and in a region of compact structure that includes the loop-turn Val 74-Ser 82 and the C-terminal residues (Pro 102-Trp 106). The significance of these findings is discussed in light of the considerable dependence of the binding interaction between Pdx and CYPlOl upon the oxidation state of Pdx.

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Study of Moderately Rapid Chemical Exchange Reactions by Means of Nuclear Magnetic Double Resonance

Cited by 1,191 publications

References 10 publications

Magnetization transfer MRS

Magnetization transfer MRS

The orientation and dynamics of substance P in lipid environments

Redox‐dependent dynamics of putidaredoxin characterized by amide proton exchange

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