Nasser Din Rami, Venu Aiswarya Chalikunnath, Rudszuck Thomas, Vallet Alicia, Favier Adrien, Powell Annie K, Guthausen Gisela, Ibrahim Masooma, Krämer Steffen
Université Grenoble Alpes, LNCMI-EMFL, CNRS, INSA-T, and UPS, CEDEX 9, 38042 Grenoble, France.
Institute of Nanotechnology, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany.
Molecules. 2024 Oct 19;29(20):4956. doi: 10.3390/molecules29204956.
The longitudinal and transverse nuclear magnetic resonance relaxivity dispersion (NMRD) of H in water induced by the paramagnetic relaxation enhancement (PRE) of dissolved lanthanide ions (Ln) can become very strong. Longitudinal and transverse H NMRD for Gd, Dy, Er and Ho were measured from 20 MHz/0.47 T to 1382 MHz/32.5 T, which extended previous studies by a factor of more than two in the frequency range. For the NMRD above 800 MHz, we used a resistive magnet, which exhibits reduced field homogeneity and stability in comparison to superconducting and permanent NMR magnets. These drawbacks were addressed by dedicated NMRD methods. In a comparison of NMRD measurements between 800 MHz and 950 MHz performed in both superconducting and resistive magnets, it was found that the longitudinal relaxivities were almost identical. However, the magnetic field fluctuations of the resistive magnet strongly perturbed the transverse relaxation. The longitudinal NMRDs are consistent with previous work up to 600 MHz. The transverse NMRD nearly scales with the longitudinal one with a factor close to one. The data can be interpreted within a PRE model that comprises the dipolar hyperfine interactions between the H and the paramagnetic ions, as well as a Curie spin contribution that is dominant at high magnetic fields for Dy, Er and Ho. Our findings provide a solid methodological basis and valuable quantitative insights for future high-frequency NMRD studies, enhancing the measurement accuracy and applicability of PRE models for paramagnetic ions in aqueous solutions.
溶解的镧系离子（Ln）的顺磁弛豫增强（PRE）所诱导的水中氢（H）的纵向和横向核磁共振弛豫率色散（NMRD）可能会变得非常强烈。测量了钆（Gd）、镝（Dy）、铒（Er）和钬（Ho）在20 MHz/0.47 T至1382 MHz/32.5 T范围内的纵向和横向H NMRD，该频率范围比之前的研究扩展了两倍多。对于高于800 MHz的NMRD，我们使用了一个电阻磁体，与超导和永磁NMR磁体相比，它的场均匀性和稳定性有所降低。这些缺点通过专门的NMRD方法得以解决。在超导磁体和电阻磁体中进行的800 MHz和950 MHz之间的NMRD测量比较中，发现纵向弛豫率几乎相同。然而，电阻磁体的磁场波动强烈干扰了横向弛豫。纵向NMRD与高达600 MHz的先前工作一致。横向NMRD几乎与纵向NMRD成比例，比例因子接近1。这些数据可以在一个PRE模型中得到解释，该模型包括H与顺磁离子之间的偶极超精细相互作用，以及在高磁场下对Dy、Er和Ho占主导的居里自旋贡献。我们的研究结果为未来的高频NMRD研究提供了坚实的方法基础和有价值的定量见解，提高了PRE模型在水溶液中顺磁离子的测量精度和适用性。
