Bloch equations for proton exchange reactions in an aqueous solution

Lee, Jae Seung; Regatte, Ravinder R.; Jerschow, Alexej

doi:10.1002/cmr.a.21397

Cited by 8 publications

(6 citation statements)

References 51 publications

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“…28 Varying pH using a phosphate buffer had no measurable effect on the measured exchange rate of the samples (Figures 5 and S3). However, a recent study suggests that creatine exchange is not strongly catalysed by phosphate, 29 and another study has shown a complex relationship between line broadening and phosphate, 30 which is similar to the changes we see in our data, as demonstrated in Figure S3c.…”

Section: Creatine Phantomsupporting

confidence: 92%

Measuring chemical exchange saturation transfer exchange rates in the human brain using a particle swarm optimisation algorithm

et al. 2023

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The z‐spectrum contains many pools with different exchange rates and T2 values, which can make it difficult to interpret in vivo data and complicates the design of experiments aimed at providing sensitivity to one pool. This work aims to characterise the main pools observable with MRI at 7T in the human brain. To achieve this, we acquired z‐spectra at multiple saturation powers in the human brain at 7T. We used simulations to optimise the use of particle swarm optimisation (PSO) to fit these data, validating this approach using further simulations and creatine phantoms. We then used the PSO to fit data from grey and white matter for the pool size, exchange rate, and T2 of five proton pools (magnetisation transfer, amides, amines, nuclear Overhauser enhancement NOE−3.5ppm and NOE−1.7ppm in addition to water). We then devised an approach for using PSO to fit z‐spectra while limiting the computational burden, and we investigated the sensitivity of the fit to T2 and k for three overlapping pools. We used this to measure the exchange rate of creatine and to show that it varied with temperature, as expected. In the brain we measured a significantly larger pool size in white matter than in grey matter for the magnetisation transfer pool and the NOE−3.5ppm pool. For all other parameters we found no significant difference between grey and white matter. We showed that PSO can be used to fit z‐spectra acquired at a range of B1 to provide information about peak position, amplitude, exchange rate, and T2 in vivo in the human brain. These data could provide more sensitivity to change in some clinical conditions and will also provide key information for further experimental design.

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Section: Creatine Phantomsupporting

confidence: 92%

Measuring chemical exchange saturation transfer exchange rates in the human brain using a particle swarm optimisation algorithm

et al. 2023

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“…As evidenced by Figure 2d from the absence of a peak at ~1.25 ppm that is characteristic of Boc groups, the deprotection was almost quantitatively completed, giving the corresponding polymeric catalysts with different unit ratios in good yields (>85%). It is worth mentioning that the signal from amide N–H was not detected as a consequence of the proton exchange with trace water in the deuterated solvent [31,32].…”

Section: Resultsmentioning

confidence: 99%

A Pseudopeptide Polymer Micelle Used for Asymmetric Catalysis of the Aldol Reaction in Water

Liu

Yao

et al. 2018

Polymers

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Micelles assembled from amphiphilic molecules have proved to be ideal scaffolds to construct artificial catalysts mimicking enzymatic catalytic behavior. In this paper, we describe the synthesis of amphiphilic poly(2-oxazoline) derivatives with l-prolinamide units in the side chain and their application in asymmetric aldol reactions. Upon dissolution in water, the pseudopeptide polymers self-assembled into particles with different sizes, relying on the copolymer composition and distribution of hydrophilic/hydrophobic segments in the polymer chain. A preliminary study has demonstrated that the catalytic activity of these polymeric organocatalysts are strongly dependent on the aggregated architecture. The micelle-type assemblies can act as nanoreactors to efficiently promote the direct aldolisation of cyclohexanone with aromatic aldehydes in aqueous media, affording anti-aldol products in excellent yields (88–99%) and higher stereoselectivities (90/10 dr, 86% ee) compared to their nonmicellar systems under identical conditions.

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“…Furthermore, the model can be extended to reactive mixtures, for which flow effects are hard to handle using calibration techniques. This can be done by incorporating the corresponding additional exchange terms in the Bloch equation [38].…”

Section: Mixtures Of Water + Acetonitrilementioning

confidence: 99%

Prediction of flow effects in quantitative NMR measurements

Friebel

Specht

Harbou

et al. 2020

Journal of Magnetic Resonance

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A method for the prediction of the magnetization in flow NMR experiments is presented, which can be applied to mixtures. It enables a quantitative evaluation of NMR spectra of flowing liquid samples even in cases in which the magnetization is limited by the flow. A transport model of the nuclei's magnetization, which is based on the Bloch-equations, is introduced into a computational fluid dynamics (CFD) code. This code predicts the velocity field and relative magnetization of different nuclei for any chosen flow cell geometry, fluid and flow rate. The prediction of relative magnetization is used to correct the observed reduction of signal intensity caused by incomplete premagnetization in fast flowing liquids. By means of the model, quantitative NMR measurements at high flow rates are possible. The method is predictive and enables calculating correction factors for any flow cell design and operating condition based on simple static T 1 time measurements. This makes time-consuming calibration measurements for assessing the influence

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Bloch equations for proton exchange reactions in an aqueous solution

Cited by 8 publications

References 51 publications

Measuring chemical exchange saturation transfer exchange rates in the human brain using a particle swarm optimisation algorithm

Measuring chemical exchange saturation transfer exchange rates in the human brain using a particle swarm optimisation algorithm

A Pseudopeptide Polymer Micelle Used for Asymmetric Catalysis of the Aldol Reaction in Water

Prediction of flow effects in quantitative NMR measurements

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