Configurational-bias Monte Carlo simulation of n-butane in NaY zeolite has been reported at different temperatures and loadings. In contrast to n-butane in silicalite, the gauche conformer population is always found to be higher in zeolite NaY than in pure fluid at the same density. Normally, an increase in adsorbate concentration in gases such as methane, rare gases, etc. leads to an increase in population near the cage centre. In contrast, we find that an increase in n-butane concentration gives rise to an increase in population near the periphery of the cage. Enhancement in gauche conformer population observed for NaY zeolite is attributed to the surface curvature of the alpha-cavity.