A crowded molecular scene can be hard to inspect folder by folder. The names may not tell you which folders contain a small ligand, a large assembly, several chains, or a structure with an unusual overall charge. In SAMSON, the Node Specification Language (NSL) lets you search folder nodes by those properties, so you can narrow the scene before opening items one at a time.
Folder attributes describe structures contained in folders. Their short prefix is f, and the f. prefix matters: these expressions target folders rather than, for example, individual atoms. The examples below are useful as separate searches when you are deciding what to inspect next.
Start with size and organization
If you are looking for folders containing relatively small structures, try f.nat < 1000. This selects folders with fewer than 1,000 atoms. To focus on a particular size band, use a range such as f.nat 100:200. The same kind of integer comparison can help you sort structures by their organization:
f.nc < 3finds folders with fewer than three chains.f.nm 2:4finds folders with between two and four molecules.f.nr > 100finds folders with more than 100 residues.f.ns 1:3searches for folders with one to three segments.
These counts answer different questions. Atom count gives a broad measure of structure size; chain, molecule, residue, and segment counts describe other aspects of organization. Choosing the attribute that matches your question can make a search more informative than relying on a folder name alone.
Use composition to narrow candidates
When atom count is not enough, elemental counts can help distinguish folders. For example, f.nC < 10 searches for folders with fewer than ten carbon atoms, while f.nO 10:20 searches for folders with ten to twenty oxygen atoms. Corresponding attributes are available for hydrogen (f.nH), nitrogen (f.nN), and sulfur (f.nS). For coarse-grained structures, f.ncga < 1000 searches by the number of coarse-grained atoms.
These are folder-level counts, which makes them useful for screening collections: you can ask whether a folder’s contents have a particular size or elemental count without first identifying every atom manually. Treat the results as a way to find candidates for closer inspection, not as a substitute for checking the structures themselves.
Check total charge
Charge can be another useful sorting criterion. Use f.fc 1 to find folders whose structures have a total formal charge of 1, or f.fc 6:8 to search for formal charges from 6 to 8. For total partial charge, the corresponding attribute is f.pc; for example, f.pc 1.5:2.0 searches for values in that range.
Formal charge and partial charge are separate attributes, so choose the one relevant to the question you are investigating. The page also lists inherited folder attributes for name, visibility, selection, and material. For example, f.n "A" searches by name, while f.v matches visible folders.
A practical search habit
Begin with one clear criterion—such as f.nat < 1000—and inspect the matches. Then try a more specific attribute, such as chain count or oxygen count, if the first result set is still too broad. Keeping searches focused makes it easier to understand why a folder matched and helps avoid overlooking candidates hidden in a large scene.
For the complete attribute list and additional examples, see the SAMSON folder attributes reference.
Note: SAMSON and all SAMSON Extensions are free for non-commercial use. Get SAMSON.