Magnetic Resonance Spin-spin Relaxation Time Research Articles

Gelling properties of myosin as affected by L-lysine and L-arginine by changing the main molecular forces and microstructure

ABSTRACTThis paper investigated the effects of l-lysine (Lys) and l-arginine (Arg) on the water-holding capacity (WHC) and hardness of myosin gel as well as the mechanism of these effects. The results showed that Lys, Arg, and KOH increased the WHC but decreased the hardness in all cases. At pH 6.32, the WHC increased in the order control < KOH < Lys ≈ Arg, while the hardness decreased in the order control > KOH > Lys > Arg. Lys shortened low field nuclear magnetic resonance spin-spin relaxation times (T2), while Arg and KOH slightly affected T2. Lys, Arg, and KOH had different influences on the molecular forces in myosin gels and the distribution of myosin size. Lys formed a gel with porous clusters, while Arg generated a gel with fine caves. Therefore, both Lys and Arg changed the microstructure of myosin gel by changing the distribution of the myosin size as well as the molecular forces that form and/or maintain myosin gel, ultimately contributing to the differences in the WHC, hardness, and T2.

Magnetic resonance spin-spin relaxation time estimation in a rat model of fatty liver disease.

To compare mono- and bi-exponential relaxation model equations to discriminate between normal and fatty liver disease. Six rats on a choline deficient amino acid modified (CDAA) diet and six on normal chow were studied. Multiple spin echo images with increasing echo times (TEs) were collected at 9.4T. Pixel-wise T2 maps were generated using mono-exponential decay function to calculate T2M , and a bi-exponential to calculate, short T2 component (T2S ), long T2 component (T2L ), and fractions of these components (ρS , ρL ), respectively. Statistical F-tests and Akaike's information criterion (AIC) were used to assess the relative performance of the two models. F-test and AIC showed that in the CDAA group, T2 bi-exponential model described the signal of T2 weighted imaging of the liver better than the mono-exponential model. Controls were best described by the mono-exponential model. Mean values for T2M , T2L , T2S , ρS , ρL were 31.2 ± 0.7 ms, 72.8 ± 3.3 ms, 8.2 ± 0.6 ms,71.2 ± 2.1%, 30.4 ± 1.3%, respectively, in CDAA rats, compared with 18.8 ± 0.5 ms, 32.3 ± 0.7 ms, 9.2 ± 1.8 ms, 79 ± 2%, 21.0 ± 1.1% in controls. In the fatty liver of CDAA rats we have shown that T2 weighted images fit the bi-exponential model better than mono-exponential decays thus providing a better description of the data. 1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:468-476.

Application of Nuclear Magnetic Resonance to Detect Toxigenic Clostridium difficile from Stool Specimens: A Proof of Concept

We evaluated the performance of an early prototype core molecular mirroring nuclear magnetic resonance detection platform (Mentor-100) to detect toxigenic Clostridium difficile from stool. This technology uses customized nanoparticles bound to target specific oligonucleotide probes that form binaries in the presence of nucleic acid from the target microorganism. Liquid patient stool specimens were seeded with C. difficile or other Clostridium species to determine the analytical sensitivity and specificity. Samples underwent nucleic acid extraction and target amplification with probes conjugated with iron nanoparticles. Signal from nuclear magnetic resonance spin-spin relaxation time was measured to detect the presence or absence of toxigenic C. difficile. The limit of detection was <180 colony forming units per reaction of toxigenic C. difficile. No cross-reactivity was observed with nontoxigenic C. difficile, Clostridium sordellii, Clostridium perfringens, Bacillus subtilis, or Paenibacillus polymyxa at 108 colony forming units/mL. Correlation studies using frozen stool samples yielded a sensitivity of 88.4% (61 of 69) and a specificity of 87.0% (40 of 46) as compared with a commercial PCR assay for C. difficile. The area under the curve in the receiver operating characteristic curve analysis was 0.922. The prototype molecular mirroring platform showed promising performance for pathogen detection from clinical specimens. Theplatform design has the potential to offer a novel, low-cost alternative to currently available nucleic acid-based tests.

Characterisation of Soybean and Wheat Seeds by Nuclear Magnetic Resonance Spectroscopy

The effects of equilibration under different air relative humidities (RH, 1 - 90 %) and temperatures (35 and 45 °C) on soybean (Glycine max) and wheat (Triticum aestivum) seeds were studied using different techniques. Seed moisture content, electrical conductivity (EC) of seed leachate and per cent seed germination were measured following standard procedures, and compared with nuclear magnetic resonance spin-spin relaxation time (T2) measurements. Moisture contents of soybean and wheat seeds, following the reverse sigmoidal trend, were greater at 35 than at 45 °C at any particular RH. Changes in T2 were related to the changes in germination percentage and leachate EC of both soybean and wheat seeds. Equilibrating soybean seeds at RH ≤ 11 % decreased germination percentage with corresponding decrease in T2. On the contrary, EC of seed leachate increased. In wheat seeds equilibrated at 45 °C, T2 was maximal at RH 5.5 %. T2 declined in seeds equilibrated at high RH (> 80 %) together with low germination percentage.

In vivo visualization of myelin water in brain by magnetic resonance

We exploit the intrinsic difference in magnetic resonance spin-spin relaxation time, T2, between water associated with myelin sheaths and water in other central nervous system tissue in order to measure myelin water content within any region of an image or to generate indirectly a myelin map of the brain. In normal volunteers, myelin water maps give the expected myelin distribution. In multiple sclerosis patients, lesions exhibit different myelin water contents providing insight into the demyelination process unavailable from conventional magnetic resonance images. In vivo myelin measurement has important applications in the clinical management of multiple sclerosis and other white matter diseases.

Nuclear magnetic resonance spin-spin relaxation time in hydrated protein powders. A two site dynamic exchange model

Nuclear magnetic resonance spin-spin relaxation time in hydrated protein powders. A two site dynamic exchange model