Study of instanton contributions to moments of nucleon spin-dependent structure functions

Instantons are the natural mechanism in non-perturbative QCD to remove heli city from valence quarks and transfer it to gluons and quark-antiquark pair s. To understand the extent to which instantons explain the so-called "spin crisis" in the nucleon, we calculate moments of spin-dependent structure f unctions in quenched QCD and compare them with the results obtained with co oled configurations from which essentially all gluon contributions except i nstantons have been removed. Preliminary results are presented.