ATP Can Act as a Stabilizer on Neutral Macromolecules.

Area of Science:

• Biochemistry
• Physical Chemistry
• Polymer Science

Background:

• Adenosine triphosphate (ATP) is crucial for cellular energy and has recently been identified as a hydrotrope.
• ATP's hydrotropic role, particularly in destabilizing protein coacervates, requires further mechanistic investigation.
• Understanding ATP's interaction with macromolecules is key to elucidating its diverse biological functions.

Purpose of the Study:

• To investigate the influence of ATP and related molecules on macromolecular phase transitions.
• To explore the mechanism behind ATP's hydrotropic action on poly(N-isopropylacrylamide) (PNIPAM).
• To determine the concentration-dependent effects of ATP on macromolecule solubility and aggregation.

Main Methods:

• Utilized Lower Critical Solution Temperature (LCST) and spectroscopic techniques (1H NMR, ATR-FTIR).
• Employed solvation shell spectroscopy and all-atom molecular dynamics (MD) simulations.
• Analyzed the effects of adenine, adenosine, AMP, triphosphate (TP), and ATP on PNIPAM.

Main Results:

• ATP, AMP, and triphosphate promoted macromolecule aggregation (salting-out effect), while adenine and adenosine had minimal impact.
• ATR-FTIR confirmed salting-out behavior at physiological ATP concentrations (<0.1 M).
• No specific binding interactions were detected between PNIPAM and ATP via spectroscopy or MD simulations; ATP self-associates at higher concentrations.

Conclusions:

• ATP's hydrotropic action is dependent on macromolecule structure and concentration.
• At physiological concentrations, ATP stabilizes neutral macromolecules through an excluded volume effect, not by direct binding.
• The findings clarify ATP's role in macromolecular behavior, distinct from its effect on protein coacervates.