load=1a02
define polar (oxygen or nitrogen) and (dna or *:F)
define nonpolar (carbon or phosphorus or sulfur) and (dna or *:F)
define small (pyrimidine and (*.?1 or  *.?2 or *.?3)) or (purine and (*.?2 or *.?3 or *.?4 or *.?9))
define big (pyrimidine and (*.?4 or *.?5 or *.?6 or *.?7)) or (purine and (*.?1 or *.?5 or *.?6 or *.?7 or *.?8))
select within (3.5, *.O?') and *:F and polar 
pause
select within (4.5, *.C?') and  *:F and nonpolar 
pause
select within (3.5, (*.OP? and dna)) and *:F and polar 
pause
select within (4.5, (phosphorus and dna)) and *:F and nonpolar 
pause
select within (3.5, big and polar) and *:F and polar 
pause
select within (4.5, big and nonpolar) and *:F and nonpolar
pause
select within (3.5, small and polar) and *:F and polar 
pause
select within (4.5, small and nonpolar) and *:F and nonpolar