Biomolecular structures are molecules associated with DNA, RNA or proteins which are a key signature of life. I know it would be a great sign that life exists on other planets if we could find some in space but I do not believe any evidence has been found of them yet.
No biomolecules (DNA/RNA/proteins) have been found in space. There are some much smaller molecules that are considered to be “biomarkers”, such as methyl chloride, that form when biomolecules break down. Some of these have been detected in space, but no one has confirmed that they were produced by decomposing biomolecules.