  In this article we address the general approach for calculating dynamical
dipole polarizabilities of small quantum systems, based on a sum-over-states
formula involving in principle the entire energy spectrum of the system. We
complement this method by a few-parameter model involving a limited number of
effective transitions, allowing for a compact and accurate representation of
both the isotropic and anisotropic components of the polarizability. We apply
the method to the series of ten heteronuclear molecules composed of two of
($^7$Li,$^{23}$Na,$^{39}$K,$^{87}$Rb,$^{133}$Cs) alkali-metal atoms. We rely on
both up-to-date spectroscopically-determined potential energy curves for the
lowest electronic states, and on our systematic studies of these systems
performed during the last decade for higher excited states and for permanent
and transition dipole moments. Such a compilation is timely for the
continuously growing researches on ultracold polar molecules. Indeed the
knowledge of the dynamic dipole polarizabilities is crucial to model the
optical response of molecules when trapped in optical lattices, and to
determine optimal lattice frequencies ensuring optimal transfer to the absolute
ground state of initially weakly-bound molecules. When they exist, we determine
the so-called "magic frequencies" where the ac-Stark shift and thus the viewed
trap depth, is the same for both weakly-bound and ground-state molecules.
