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Consider the peptide fragment :
T1 *CONN NFRAG 6 AT1 C 2 AT2 N 1 1 AT3 O 1 BO 1 2 BO 1 3 2 END QUES T1
NFRAG 6 requires that all hits must have at least 6 occurrences of the peptide search fragment and these occurrences must not overlap.
NFRAG -6 would allow overlap, thereby hitting urea-type structures.
If you wished to find structures having exactly 6 occurrences then you would proceed as follows:
Consider the search fragment :
Here we have two disconnected sub-fragments, the pyridinium cation and the sulfite anion.
If we include the instruction SAMERES in the connectivity test instruction packet a hit will be registered for (i) but not for (ii):
It takes the form: C text
There is no limit on the number of comment instructions and they can occur at any position in the connectivity search test instruction packet between the *CONN instruction and the END instruction.
C This test specifies the enol-form of the barbiturate.
It takes the form: NOSC
Normally this instruction would be used only by CCDC staff to test the efficiency of a screen.
Atom numbers p in ATp must be in the range 1-250. These numbers do not have to be sequential or continuous.
Volume 1 Chapter 6 Implicit and Explicit Hydrogen Atoms.