{
  "id": 11078756,
  "title": "Pyrrolocytosine as a Fluorescent Sensor of RNA-Small Molecule Interactions",
  "url": "https://urgent.news/2026/09/30/pyrrolocytosine-as-a-fluorescent-sensor-of-rna-small-molecule",
  "topic": "science",
  "section": "Science",
  "published": "2026-09-30T00:00:00.000Z",
  "source": {
    "name": "bioRxiv",
    "slug": "biorxiv",
    "url": "https://www.biorxiv.org/content/10.64898/2026.09.29.755477v1?rss=1"
  },
  "original_language": "en",
  "account": "Pyrrolocytosine (pC), an analogue of cytosine, has emerged as a sensitive fluorescent probe for studying RNA structure. In this research, scientists incorporated pC into the aptamer domain of the B. subtilis guanine riboswitch to investigate its potential in sensing RNA-small molecule interactions. Utilizing complementary fluorescence spectroscopy methods, the researchers examined the functional impacts and ligand-sensitivity of pC substitutions both distal to and within the binding pocket.\n\nThe study revealed that pC substitution within a static structural region exhibited the expected ligand-independent fluorescence properties. However, when pC was placed in the ligand binding pocket, it displayed a moderately decreased affinity for guanine (G) and hypoxanthine (Hx) while maintaining high specificity for G. The researchers found that pC functions as a turn-off sensor, displaying distinct changes in fluorescence upon binding with G or Hx. These differences were dependent on the number of hydrogen bonds formed with pC and were discernible in both time-dependent and steady-state fluorescence measurements.\n\nThe findings demonstrate that pC can be effectively employed to study RNA-small molecule interactions and differentiate between similar ligands even when they possess identical binding modes.",
  "summary": "Fluorescent base analogues have proven to be valuable probes of RNA structure. Pyrrolocytosine (pC), an analogue of cytosine, exhibits highly environment-sensitive fluorescence within RNA and is strongly quenched in hydrogen-bonded contexts. In this work, we incorporated pC into the aptamer domain of the B. subtilis guanine riboswitch to determine if this quenching mechanism could allow for…",
  "key_points": [],
  "editors_take": null,
  "illustration": null,
  "coverage": {
    "outlets": 1,
    "also_reported_by": []
  },
  "ai_generated": true,
  "disclaimer": "Summaries, key points and the editor’s take are written by software from other outlets’ reporting and may contain errors — always check the linked original."
}