Polarized structure functions of proton and neutron and the Gerasimov-Drell-Hearn and Bjorken sum rules

The value of power corrections to the integrals of the polarization structure functions of proton and neutron {integral} g1{sub p,n}(x)dx measured by the EMC, SMC, and E142 groups, is determined based on a model which accounts for higher twist terms, has the correct asymptotic behavior at large Q{sup 2} and satisfies the Gerasimov-Drell-Hearn sum rule at Q{sup 2}=0. The contribution of resonances up to W=1.8GeV at Q{sup 2}=0 is taken into account based on the analysis of electroproduction data. It is shown that when taking into account these higher twit terms, the experimental data agree with the Bjorken sum rule and part of the proton spin projection carried by quarks, is consistent with the natural estimate of {approximately}50%