The Constraint on FCNC Coupling of the Top Quark with a Gluon from ep Collisions

Using the constraint on the single top production cross-section obtained at the HERA collider, $\sigma (ep\to etX)$, we evaluate an upper limit on oupling constant of the anomalous top quark interaction with a gluon via flavor-changing neutral current: $\mathrm{\mid }{\kappa }_{tgq}\mathrm{/}\mathrm{\Lambda }\mathrm{\mid }\le 0.4{TeV}^{-1}$, BR$(t\to gq)<13$