Limiting the discussion to the intramolecular terms parameterized in the present work with the JOYCE3.0 code, the first three contributions on the right side of equation ( ), refer to "stiff" IC's (r sti f f ), which are most likely subjected to small oscillations around their equilibrium value, and can be approximated through harmonic potentials. Among these, the first two terms are routinely employed in most general-purpose force-fields, describing respectively bond stretching (s) and angle bending (b), i.e.: