Proton longitudinal relaxation coupling in dynamically heterogeneous soft systems

The physical mechanism of “inhomogeneous” magnetization transfer MRI

“…In a sample that exhibits MT signals, a non-aqueous ihMT (where the non-aqueous ihMTR -0) will cause an aqueous ihMT because of magnetization exchange. Under physiological conditions, magnetization exchange happens primarily via proton exchange between water and the hydroxyl protons in lipid headgroups [18][19][20].…”

Multicomponent analysis of T1 relaxation in bovine articular cartilage at low magnetic fields

“…On this basis, we have to ascribe a major effect to the zonal heterogeneity of AC. However, one cannot exclude the T 1 relaxation broadening due to water‐protein interactions on a local length scale, which refers to the magnetization transfer between water entrapped inside the protein matrix and bulk water . Thus, according to Ref 20, 30%‐35% of water in AC is entrapped in the intrafibrillar space within collagen and the remainder in the extrafibrillar space.…”

“…To address the observed tendency of T 1 relaxation in AC toward a single exponential at high fields, we will refer to a particular relaxation model called an exchange‐mediated orientational randomization (EMOR) . Similar to other 3‐pool models, the EMOR model attributes the water‐ 1 H relaxation enhancement in tissue to the proton exchange between bulk water and a pool of protons (termed intermediary protons) consisting of labile macromolecular groups and entrapped water molecules. The efficiency of this mechanism relies on the residence time τ ex of intermediary protons falling in the microsecond range.…”

A fast field-cycling device for high-resolution NMR: Design and application to spin relaxation and hyperpolarization experiments

“…At the same time, many phenomena, which can be probed by NMR, are magnetic field-dependent, this holds, for instance, for spin relaxation and spin hyperpolarization. In the case of spin-relaxation field dependences of transverse and longitudinal relaxation time yield important information [1][2][3][4][5][6][7][8][9][10][11] on molecular mobility in biological systems, polymers [12], liquid crystals, etc. Hyperpolarization, i.e., strong non-thermal polarization of spins providing [13][14][15][16][17][18][19][20][21] significant NMR signal enhancements, is also field-dependent: it is common that the efficiency of polarizing spins is maximal not at high field of NMR detection but at lower field.…”