Water Proton Spin-spin Relaxation Times Research Articles

Gelation Mechanism of Surimi Studied by 1H NMR Relaxation Measurements

In order to elucidate the gelation mechanism of surimi, the temperature dependence of water proton spin-spin relaxation time ((1)H T(2)) has been described by a theoretical approach, in which the exposed protein surface is taken into account. Water (1)H T(2) measured for horse mackerel surimi in the presence of 2.5% NaCl was analyzed on the basis of the consideration for the denaturation and the aggregation of protein in order to explain the macroscopic structural change during the heating and the cooling processes. The temperature dependence of water (1)H T(2) and the fraction of rigid component gave a clear explanation for the gelation mechanism of surimi. Differential scanning calorimetry thermogram and dynamic viscoelastic measurements supported the results of nuclear magnetic resonance (NMR) measurements. It has been demonstrated that the measurement of NMR relaxation times is useful to describe the gelation mechanism of surimi.

Sol-Gel transition of κ-Carrageenan as viewed through NMR

Abstract 23Na, 87Rb, and 133Cs NMR spectra were observed to study an interaction between these cations and κ-carrageenan. It was found that the NMR intensity of gel-forming cations undergoes a remarkable change in the vicinity of the sol-gel transition temperature, while the non-gel-forming cation which coexists together with a gel-forming cation does not show any change. These results suggest that gel-forming cations selectively interact with κ-carrageenan. Motion of water molecules in the gel and the solution of κ-carrageenan was studied by measuring the water proton spin-spin relaxation time. The results indicate three different types of water molecule: a free bulk water molecule, a water molecule strongly bound to κ-carrageenan, and a water molecule weakly bound to the gel network.

Does signal-attenuation on high-field T2-weighted MRI of the brain reflect regional cerebral iron deposition? Observations on the relationship between regional cerebral water proton T2 values and iron levels.

T2-weighted MRI shows attenuated signals from the basal ganglia, such signal attenuation being more evident at high magnetic field strengths of 1.5 tesla (T). The basal ganglia contain high levels of iron, and it has been suggested that these iron deposits lead to shortening of bulk water T2 protons via a mechanism involving diffusion of water through local magnetic field gradients generated by the iron. This mechanism generates a relaxation contribution that is proportional to the square of the applied static field B0, and if it is significant the relaxation rate 1/T2 should be strongly dependent on Bo. T2-weighted MRI would then provide a potential means of imaging regional cerebral iron levels at field strengths that are high enough for this mechanism to be important. The bulk water proton spin-spin relaxation times (T2) of samples from caudate nucleus, frontal cortex, and white matter, taken from fresh cerebral necropsy material of four subjects dying of non-neurological conditions, and one subject with Parkinson's disease have been measured. T2 values were compared with regional cerebral iron content. At high field strengths (2.35 T and 8.5 T) no significant variation in regional cerebral water proton T2 values was found; caudate, cortex and white matter had similar water proton spin-spin relaxation times in spite of the variation in their iron content. Increasing the field strength from 2.35 T to 8.5 T resulted in a generalised 50% decrease in mean regional cerebral T2 values, as opposed to the 13-fold decrease expected if T2 relaxation was dominated by a mechanism that is dependent on B02. It was thus not possible to provide evidence that iron deposition per se is responsible for the attenuated signal obtained from the basal ganglia in T2-weighted MRI.