Equivalence Principle and Partition of Angular Momenta in the Nucleon

The manifestation of equivalence principle (EP) in spin-gravity interactions, resulting in the nullification of the corresponding analog of Anomalous Magnetic moment is explored. Its tests in the experiments with atoms and cold neutrons are discussed. The validity of EP separately for quarks and gluons in the nucleon resulting in exact equipartition of momentum and total angular momentum is conjectured. The important role of relocalization (Belinfante) invariance in these and other aspects of nucleon spin structure is stressed.