# Polyamines of unique structure are integrated in Synura echinulata biosilica

## TL;DR

This study identifies unique long-chain polyamines in the biosilica of Synura echinulata, suggesting a general role for these molecules in silica formation in algae.

## Contribution

The discovery of amino butyl-based long-chain polyamines in Synura echinulata biosilica introduces a novel structural variant not previously observed in other biomineralizing algae.

## Key findings

- Unique long-chain polyamines (LCPAs) were identified in Synura echinulata biosilica.
- LCPAs in S. echinulata are composed of amino butyl repeat units, differing from amino propyl units in other species.
- The presence of LCPAs in biomineralizing algae suggests a general role in silica biomineralization.

## Abstract

Unicellar, biomineralizing algae like diatoms or Synurales are ubiquitous in various habitats all over the world and have an outstanding role in different biogeochemical cycles. They are well known for their elaborate nanopatterned cell structures consisting of amorphous biosilica, which is intracellularly synthesized. Special biomolecules assist in the silica formation. In particular, species-specific long-chain polyamines (LCPAs) are commonly found in diatom biosilica and seem to play a special role due to their ability to self-assemble and induce silica precipitation. In contrast to diatoms, no species from the order Synurales have been tested yet for the presence of LCPAs. Therefore, the present work deals with the analysis of Synura echinulata biosilica using a novel HPLC-HR-MS/MS method. The presence of unique LCPAs is shown, and their structure is elucidated via MS/MS experiments. LCPAs from S. echinulata are based on amino butyl repeat units—in contrast to previously described LCPAs from other organisms, which are mostly based on amino propyl repeat units. The ubiquitous presence of LCPAs in biomineralizing species strongly indicates a general role of LCPAs in silica biomineralization.

The online version contains supplementary material available at 10.1007/s00216-025-05891-3.