Multiple quantum coherences: New NMR tools to study materials and living systems

Intermolecular multiple-quantum coherences have been proven in recent years to provide a novel contrast mechanism to study heterogeneity in liquid systems. This subject represents a source of remarkable interest in the fields of physics of matter and biomedicine. Recent results achieved on intermolecular double-quantum signal transverse relaxation decay in confined liquid systems (such as in vivo bone marrow in trabecular bone, and doped water in glass capillary pipes) are reported and discussed in this paper. Correlated two-dimensional spectroscopy revamped by asymmetric z-gradient echo detection-like sequences were implemented in order to perform intermolecular double-quantum transverse relaxation T-2DQ and T-2DQ* measurements. Our experimental results indicated that the relationship T-2.n* = T-2*/n between n-quantum transverse relaxation time and the conventional single-quantum T-2* only applies for homogeneous systems and fails in the case of highly heterogeneous systems like porous systems.