Portable single-sided NMR measurements at variable temperatures: Implementation of a thermo-controlled device and application to the heating of bread dough

A temperature control unit was implemented to vary the temperature of samples studied on a commercial Mobile Universal Surface Explorer nuclear magnetic resonance (MOUSE-NMR) apparatus. The device was miniaturized to fit the maximum MOUSE sampling depth (25 mm). It was constituted by a sample holder sandwiched between two heat exchangers placed below and above the sample. Air was chosen as the fluid to control the temperature at the bottom of the sample, at the interface between the NMR probe and the sample holder, in order to gain space. The upper surface of the sample was regulated by the circulation of water inside a second heat exchanger placed above the sample holder. The feasibility of using such a device was demonstrated first on pure water and then on several samples of bread dough with different water contents. For this, T1 relaxation times were measured at various temperatures and depths and were then compared with those acquired with a conventional compact closed-magnet spectrometer. Discussion of results was based on biochemical transformations in bread dough (starch gelatinization and gluten heat denaturation). It was demonstrated that, within a certain water level range, and because of the low magnetic field strength of the MOUSE, a linear relationship could be established between T1 relaxation times and the local temperature in the dough sample.     

Characterization of local deformation in filled-silicone elastomers subject to high strain - NMR MOUSE and Magnetic Resonance Imaging as a diagnostic tool for detection of inhomogeneities

Magnetic Resonance Imaging (MRI) and unilateral Nuclear Magnetic Resonance (NMR) relaxometry with the NMR MOUSE (MObile Universal Surface Explorer) have been used to characterize local permanent deformation in silicone parts subject to high compressive strain. Samples returned from field service have been characterized by areas of high compression set. Materials excised from these damaged sections have been shown to be clearly distinguishable from undeformed material from the same part and from pristine material by NMR spin-echo, NMR MOUSE and MRI protocols. The results of these studies have been interpreted in the context of studies of model materials of varying crosslink density. The areas of local deformation have been characterized by a reduction in the residual dipolar coupling, which is proportional to the crosslink density and in the non-network sol fraction. These differences were likely to be present in these polymers at the time of production due to inefficient mixing. Additionally, both T₂ weighted Single Point Imaging (SPI) and T₂ weighted MRI experiments have been used to map out the location of different crosslink densities, ultimately determining the quality or homogeneity in silicone components.     

利用荧光浓度指示剂fura-2研究稀土离子的跨膜行为

本文提出了利用fura-2测量细胞内游离稀土离子浓度的定量方法。实验结果表明, 在模拟细胞内离子组成的条件下, 稀土离子La^3^+和Y^3^+与fura-2形成1:1的配合物。其配合物的表观离解常数分别为161nmol.dm^-^3和404nmol.dm^-^3,pH7.05, 有未配对f电子的Nd^3^+, Ho^3^+, Sm^3^+, Dy^3^+,Ce^3^+, Yb^3^+等稀土离子对荧光起萃灭作用。此性质使我们能够定性鉴定它们是否进入了细胞。我们使用如上性质, 利用单细胞阳离子测试系统, 以小鼠骨髓瘤细胞为模式细胞, 研究了上游离稀土离子的跨膜行为及部分体内小分子对稀土离子跨膜行为的影响。实验结果支持游离稀土离子不能通过细胞膜的假设, 而且所研究的体内小分子在生理浓度下对稀土离子的跨膜也无明显作用。