Comparison of spin–lattice relaxation measurements made in the presence of strong radiation damping

Abstract

The scientific literature contains reports of external magnetic fields affecting the fundamental properties and structure of water, including a report of the rotational motion of water molecules being slowed due to increased hydrogen bonding resulting from magnetic treatment. To investigate such a change in molecular motion, 1 H spin-lattice relaxation times of water were measured at increasing magnetic field strengths. Strong radiation damping was observed at each magnetic field strength when using inversionrecovery experiments. To measure the relaxation times in the presence of radiation damping, several experimental methods of saturation recovery to measure spin-lattice relaxation were applied to a 90% H 2 O sample to obtain results as a function of field strength for proton frequencies from 300 to 800 MHz.

Analysis of Water in the Chicken Eggshell Using the 1H Magic Angle Spinning Nuclear Magnetic Resonance Spectroscopy

“…In addition of the chemical shift, information on water mobility can be obtained by measuring spin-lattice relaxation times. The spin-lattice relaxation time of bulk water, measured under the same experimental conditions, is in the range from 1 s to 3 s (Taylor & Peterson, 2010). Reduced spin-lattice relaxation time is observed when liquid molecules are adsorbed on a solid surface due to a change in molecular mobility (D'Agostion et al, 2014).…”

NMR Analysis of Base‐Pair Opening Kinetics in DNA

“…Furthermore, the wide availability and use of highly sensitive NMR probes possessing high Q‐factors, as is the case in cryogenically cooled probes, but also in many high‐field room‐temperature probes, has not only provided desired boosts in signal intensity, but also led to the undesired effect of radiation damping. This was not an issue for the relaxation measurements early on, but nonetheless the presence of radiation damping was recognized and described at that point (Bloembergen and Pound, ) and has been expanded on since (Mao et al., ,b; Mao and Ye, ; Taylor and Peterson, ). It impacts the relaxation and exchange measurements discussed in this article in many ways.…”

“…Due to the high concentration of bulk water in these samples, the standard inversion recovery method to determine the T 1 -relaxation of water is not readily applicable. This Basic Protocol 2 describes a modified NMR measurement, using the saturation-recovery method (Mao, Guo et al 1994, Mao and Ye 1997, Taylor and Peterson 2010). In the Alternate Protocol 2, we describe a special, but not commonly available setup, using 1 mm NMR tubes, which allows the use of the inversion recovery measurement even with high Q cryoprobes and 95% H 2 O in these samples (see further discussion under “COMMENTARY, T 1 relaxation time of water”).…”

“…This was not an issue for the relaxation measurements early on, but nonetheless the presence of radiation damping was recognized and described at that point (Bloembergen and Pound 1954) and has been expanded on since (Mao, Guo et al 1994, Mao and Ye 1997, Taylor and Peterson 2010). It impacts the relaxation and exchange measurements discussed in this article in many ways.…”

“…Alternative approaches have been proposed by Mao et al., (,b) to measure the relaxation times of strong signals utilizing saturation‐recovery methods. Three methods to achieve selective saturation were described and further compared by Taylor (Mao and Ye, ; Taylor and Peterson, ), which included (a) selective pre‐saturation by continuous‐wave (CW) irradiation of the strong signal in analogy to the pre‐saturation experiment (Alexander, ); (b) DANTE‐style pre‐saturation with a series of π/2 pulses (Morris and Freeman, ); or (c) applying a crusher gradient following a π/2 pulse (Sklenar, ). The selective presaturation of the strong signal is usually followed by a variable delay period and a read‐out pulse, before acquiring the signal.…”