A computer-implemented method of quantifying at least a component of binding affinity between a ligand and a receptor molecule, the method comprising: receiving data representing a structure of the ligand, receiving data representing a structure of the receptor molecule, identifying a ring structure within the ligand, the ring structure being either an entire ring or a fused ring; classifying the ring structure based on the spatial relationship of the ring structure to its ambient surroundings when the ligand is bound to the receptor molecule, wherein said ambient surroundings of the ring structure when bound to the receptor molecule include water molecules; wherein the ring structure is assigned one of the following classifications: a) buried; b) solvent exposed; or c) solvent exposed on one surface; wherein determining the classification is based on: i) a calculation of the degree of enclosure of each non-hydrogen atom of the ring structure by non-hydrogen atoms of the receptor; and ii) use of a parameter corresponding to a number of water molecules in a first shell of the ring structure, or in a second shell of the ring structure or in a combination of the first shell and the second shell; and quantifying at least a component of the binding affinity between the ligand and the receptor molecule based on the classification of the ring structure, wherein said quantifying comprises calculating an initial binding affinity and then adjusting the initial binding affinity by a factor obtained based on the classification of the ring structure. receiving data representing a structure of the ligand, receiving data representing a structure of the receptor molecule, identifying a ring structure within the ligand, the ring structure being either an entire ring or a fused ring; classifying the ring structure based on the spatial relationship of the ring structure to its ambient surroundings when the ligand is bound to the receptor molecule, wherein said ambient surroundings of the ring structure when bound to the receptor molecule include water molecules; wherein the ring structure is assigned one of the following classifications: a) buried; b) solvent exposed; or c) solvent exposed on one surface; wherein determining the classification is based on: i) a calculation of the degree of enclosure of each non-hydrogen atom of the ring structure by non-hydrogen atoms of the receptor; and ii) use of a parameter corresponding to a number of water molecules in a first shell of the ring structure, or in a second shell of the ring structure or in a combination of the first shell and the second shell; and quantifying at least a component of the binding affinity between the ligand and the receptor molecule based on the classification of the ring structure, wherein said quantifying comprises calculating an initial binding affinity and then adjusting the initial binding affinity by a factor obtained based on the classification of the ring structure. i) a calculation of the degree of enclosure of each non-hydrogen atom of the ring structure by non-hydrogen atoms of the receptor; and ii) use of a parameter corresponding to a number of water molecules in a first shell of the ring structure, or in a second shell of the ring structure or in a combination of the first shell and the second shell; and