When a molecular project contains many conformations, finding the ones worth inspecting can become a small but persistent bottleneck. A name may not tell you how large a conformation is, and opening items one by one just to check their size interrupts the modeling workflow. In SAMSON, the Node Specification Language (NSL) provides a direct way to match paths by their number of atoms.
The path attribute space—abbreviated p—matches only conformation nodes. Its numberOfAtoms attribute, abbreviated nat, lets you describe a size condition using an integer comparison or a range. That makes it useful when you want to narrow a collection of conformations according to a simple, measurable property.
Set a lower size limit
If your immediate goal is to find paths with more than 100 atoms, use:
p.nat > 100
The longer form is path.nat > 100. Both forms express the same criterion: match paths whose number of atoms is greater than 100. This is useful when smaller conformations are not relevant to the task at hand, or when you want to focus attention on larger entries before reviewing them further.
Work within a size range
Sometimes a cutoff is not enough. You might want to focus on conformations with atom counts between two values. For that, use a range:
p.nat 100:200
This matches paths with between 100 and 200 atoms, as described by the NSL reference. A range can be a practical first pass when you are looking for conformations of a particular scale rather than simply separating small from large ones.
Keep the attribute space straight
A common source of confusion is the difference between the thing being matched and the property used to match it. Here, p refers to the path attribute space, which is limited to conformation nodes; nat is the specific atom-count attribute. So p.nat is the concise way to express “the number of atoms of a path.” The full attribute name is path.numberOfAtoms.
The path space also inherits some node attributes. For example, p.n "A" uses the inherited name attribute, while p.selected and p.sf refer to selection-related attributes. The short name s for selected is not available in this attribute space, so use p.selected rather than assuming that shorthand applies everywhere.
A small, repeatable way to narrow a search
When you are unsure where to start, choose a threshold that reflects the question you are trying to answer, then adjust it as needed. For a broad size cutoff, try p.nat > 100. For a bounded subset, try p.nat 100:200. These expressions let you state the criterion explicitly, making it easier to repeat the same kind of search later or share the exact filter with a collaborator.
Atom count is only one way to describe a conformation, but it is a useful first filter when size is the practical concern. For the complete list of path attributes and their examples, see the SAMSON path attribute reference.
Note: SAMSON and all SAMSON Extensions are free for non-commercial use. Get SAMSON.