When a molecular project contains many conformations, finding the ones worth inspecting can become a task of its own. Opening candidates one by one is slow, especially when the first question is simply whether a conformation is large enough—or falls within a useful size range. SAMSON’s Node Specification Language (NSL) provides a compact way to search conformation nodes by their number of atoms.
Use atom count as a first-pass filter
The conformation attribute space is written conformation, or shortened to co. Its numberOfAtoms attribute has the short name nat. That gives you two equivalent ways to express an atom-count query:
conformation.nat > 100co.nat > 100
Both match conformations containing more than 100 atoms. The shorter form is handy for repeated use; the longer form can be easier to read when you are learning NSL or revisiting a query later.
You can also specify an interval:
conformation.nat 100:200co.nat 100:200
This matches conformations with an atom count between 100 and 200. A range can be a useful first pass when you want to focus on candidates of a particular approximate size rather than include every conformation above a threshold.
Why this helps in practice
Atom count is not a measure of structural quality, and it cannot tell you whether a conformation is biologically relevant. It can, however, help reduce a large candidate set using a simple, reproducible criterion. For example, if you are preparing to inspect a collection of conformations, a threshold query can help you focus on those with more than 100 atoms. If you already have a size window in mind, the range query makes that criterion explicit.
That clarity matters when you return to a project later or share your search with a collaborator: the expression records the filter you applied, instead of leaving the selection dependent on memory or manual browsing. Treat the result as a shortlist for further inspection, not as a scientific conclusion about which structure is best.
Keep names and selection state in mind
Conformation nodes also inherit several attributes from the general node attribute space. You can query a name with expressions such as co.n "A" or co.n "L*". The documentation also lists selected and selectionFlag as inherited attributes. For example, co.selected matches selected conformation nodes, while not co.selected matches those that are not selected. The selection-flag short name is sf, as in co.sf false.
These attributes answer different questions: co.nat describes the number of atoms, while name and selection attributes describe other properties of the conformation node. Keeping those distinctions clear helps you choose a query that matches the task at hand. If your immediate bottleneck is a crowded set of candidates, start with atom count; then inspect the resulting conformations using the criteria relevant to your project.
For the complete attribute reference and syntax examples, see the SAMSON conformation attributes documentation.
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