reset

load =1hw2
pause

reset
define set1 _O and dna and backbone and CONNECTED(_C)
define set2 _O and dna and backbone and CONNECTED(_P) and not CONNECTED(_C)
define set3 _N and dna and (not backbone) 
restrict dna
cpk off
wireframe on
pause

reset
select set1
cpk 90
pause

reset
cpk off
select set2
cpk 90
pause

reset
cpk off
select set3
cpk 90
pause

select within( 3.5, set1) and not dna and _N

define bolshaya (purine and (*.C5 or *.C6 or *.N7 or *.N6 or *.C8)) or (pyrimidine and (*.C6 or *.C5 or *.C4 or *.N4 or *.C7 or *.O4)) or (nucleic and *.O6)
define malaya dna and not backbone and not bolshaya and not (*.N1 or *.N9)
define polarset _O or _N
define nonpolarset _C or _S or _P
define set1 dna and backbone and not _P and not (CONNECTED(_P) and not CONNECTED(_C)) 
define set2 _P or  (CONNECTED(_P) and not CONNECTED(_C))

select within( 3.5, (set1 and polarset)) and polarset and not dna
select within( 4.5, (set1 and nonpolarset)) and nonpolarset and not dna