When a molecular project contains many conformations, finding the ones with a suitable size can be a practical challenge. Scanning names alone may not tell you how many atoms each conformation contains. In SAMSON, the Node Specification Language (NSL) offers a direct way to filter conformation nodes by atom count, so you can express the criterion instead of checking each item manually.
Start with the conformation attribute space
Conformation-specific attributes use the conformation attribute space, abbreviated co. This space matches conformation nodes. Its numberOfAtoms attribute has the short name nat, giving you two equivalent ways to write a query:
conformation.numberOfAtoms > 100co.nat > 100
Both expressions match conformations with more than 100 atoms. The short form is convenient for repeated use; the full form can be easier to recognize when you are learning the query or revisiting it later.
Choose a threshold or a range
A threshold is useful when you have a minimum size in mind—for example, when you want to locate conformations above a chosen atom count. Change the number to fit your task:
co.nat > 100finds conformations with more than 100 atoms.
If you are looking for conformations within a bounded size window, use a range:
co.nat 100:200finds conformations with a number of atoms between 100 and 200.
This can help narrow a search to a manageable group before you inspect candidates in more detail. The range expression is also easier to adjust than repeatedly comparing individual counts: replace the two endpoints with the limits that suit the problem at hand.
Keep the query focused
The co prefix matters: it tells NSL that you are querying the conformation attribute space, rather than asking for an atom count on some other kind of node. If your intended target is a conformation, use an expression such as co.nat > 100 rather than relying on a name-based search alone.
Conformations also inherit several attributes from the general node attribute space. For example, co.n refers to the name attribute, and co.selected checks whether a conformation is selected. The inherited selected attribute does not have the short name s in this space. co.sf is the short form of selectionFlag. These attributes answer different questions: a name or selection state can help identify or describe a node, while co.nat gives you a criterion based on atom count.
A small query-planning habit
Before running a search, write down what you mean in plain language: “more than 100 atoms” or “between 100 and 200 atoms.” Then translate that condition into the corresponding NSL expression. This simple step helps prevent a common source of confusion: using a range when you meant a minimum, or choosing a threshold when you actually need an upper limit as well.
These examples are starting points, not assumptions about what a particular model should contain. Choose the threshold or interval according to your workflow, and use the full attribute name when clarity matters or the short name when brevity is helpful.
For the complete attribute reference and additional context, see the SAMSON conformation attributes documentation.
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