A crowded molecular project can be hard to navigate. Folder names may be vague, structures may have been imported in batches, and the one you need might be buried among systems of very different sizes. When a name alone is not enough, SAMSON’s Node Specification Language (NSL) lets you look for folders using properties of the structures they contain.
The useful shift is to think in terms of a question about the folder: How many atoms does its structure have? How many chains or residues? Does it contain a particular number of carbon atoms? The folder attribute space is designed for these searches. Its short prefix is f, and the attributes described here match folder nodes.
Start with a practical size check
If you are trying to distinguish smaller systems from large ones, use the atom-count attribute. For example, f.nat < 1000 matches folders whose structures have fewer than 1,000 atoms. To look for a count in a range, use f.nat 100:200. The full attribute name is folder.numberOfAtoms; the short form is simply quicker to type.
This is often a more reliable first pass than guessing from folder names. It can help narrow a project to a manageable set before you inspect individual candidates. The same integer-style pattern applies to several other counts, including chains, molecules, residues, segments, structural groups, and structural models.
Use composition to narrow the search
When size is not distinctive enough, atom counts can help describe composition. For example, f.nC < 10 selects folders with fewer than 10 carbon atoms, while f.nO 10:20 targets a range of oxygen counts. Corresponding attributes are available for hydrogen (f.nH), nitrogen (f.nN), and sulfur (f.nS).
These counts are useful as simple filters, not as complete chemical descriptions. A carbon or oxygen count by itself does not identify a molecule; it helps you find folders whose contents meet a structural criterion you already care about.
Check charge at the folder level
Folders can also be matched by total formal charge or total partial charge. For example, f.fc 6:8 looks for structures with formal charge in the documented range, while f.pc 1.5:2.0 matches structures with total partial charge in that range. The distinction matters: these are separate attributes, so choose the one that corresponds to the charge measure relevant to your task.
Keep organization and content in view
Folder filters are not limited to chemical counts. Inherited node attributes let you search by name, visibility, hidden state, selection, and material-related properties. A name expression such as f.n "L*" can help when you remember only the beginning of a folder name. The documentation also lists visibility and selection flags, which can be useful when the immediate problem is locating folders by their interface state rather than their molecular contents.
A practical approach is to begin with the criterion that most reduces the search space—often atom count, chain count, or residue count—then inspect the remaining candidates using the properties that matter to your scientific question. Treat each expression as a precise filter, and remember that these attributes describe folders and their structures, not a guarantee that a folder represents a particular biological or chemical interpretation.
For the full list of folder attributes, short names, values, and examples, see the SAMSON folder attribute reference.
Note: SAMSON and all SAMSON Extensions are free for non-commercial use. Get SAMSON.