---- Short descriptor explanation -----------

lig_cov: percentage of ligand covered by the predicted pocket;
poc_cov: percentage of the pocket covered by the co-crystallized ligand;

Size and shape descriptors:
volume: pocket volume in A^3 calculated via grid points;
surface: pocket surface in A^2 calculated via grid points;
lipo_surf: solvent accessible lipophilic surface;
depth:  depth of the pocket in A;
ellips c/a or b/a: ellipsoid main axes ratios, with a > b > c;
enclosure: ratio of number of surface to hull grid points;

Functional group descriptors:
H-don: number of hydrogen bond donors;
H-acc: number of hydrogen bond acceptors;
Met: number of metals;
Hphob: number of hydrophobic contacts;
siac ratio: relative number of hydrophobic SIACs;

Element descriptors:
nof_dif_atms:  number of surface atoms lining the pocket;
elem_x: number of elements of specific type in active site; types: C, N, O, S or other (X);

Amino acid composition:
aa_apol, aa_pol, aa_pos, aa_neg: relative number of amino acids apolar, polar, positive, and negative);

Amino acid descriptors:
ALA, ARG,...: number of amino acids in pocket, 3-letter code of 20 amino acid types;
