CPISRTWASIFRCW    CPISRTWASIFRCW Left. Same hydrophobicity and I/L about same
CPISRT---LFRCW    CPISRTL---FRCW size while W is much bigger.

CPISRTRASEFRCW    CPISRTRASEFRCW Left. K and R both positive and E negative.
CPISRTK---FRCW    CPISRT---KFRCW

CPISRTIASNFRCW    CPISRTIASNFRCW Right. H and N both hydrophilic.
CPISRTH---FRCW    CPISRT---HFRCW

CPISRTEASDFRCW    CPISRTEASDFRCW Left. N same size as D. Other difference is same
CPISRT---NFRCW    CPISRTN---FRCW between N/D and N/E plus E good for helix; N and D turn.

CPISRTSASIFRCW    CPISRTSASIFRCW Right. T and S both alcoholic and small. T/I both β-branced,
CPISRT---TFRCW    CPISRTT---FRCW but that is only secondary to hydrophobicity similarity.

CPISRTGASIFRCW    CPISRTGASIFRCW Now it is getting difficult. The PAM-250 matrix prefers A/G over
CPISRTA---FRCW    CPISRT---AFRCW A/I. In practice this will depend much on the environment. G is special
                                 because of its flexibility, but we very often find one of the three
                                 small residues (G,A,S) at the point where two helices have their cosest
                                 approach. At the Bijvoet center website I found a nice example:

CPISRTEASNFRCW    CPISRTEASNFRCW PAM-250 thinks this is almost the same. In practice this will
CPISRTQ---FRCW    CPISRT---QFRCW fully depend on the local environment in the structure. Most matrices
                                 show a preference for the left one because the one extra carbon that
                                 Q and E both have in the side chain makes them hydrophobically a bit more
                                 similar to each other than to N.

CPISRTFASTFRCW    CPISRTFASTFRCW Right. Y/F both have big aromatic ring and that is sufficiently
CPISRT---YFRCW    CPISRTY---FRCW much hydrophobic similarity. Also, if you like the idea of T and Y both
                                 being alcoholic then realize that if you mutate T <-> Y, you will find
                                 the alcohol group at a very different point in space.