Spin Dynamics and Ionic Strength Sensitivity in Nitroxide-Doped Micelles

Area of Science:

• Molecular quantum information science
• Quantum sensing
• Biophysics

Background:

• Paramagnetic spin qubits are promising for quantum sensing and probing biological systems.
• Understanding relaxation and decoherence dynamics is crucial for correlating quantum observables with chemical parameters.

Purpose of the Study:

• To investigate relaxation and decoherence dynamics of spin qubits near biological interfaces.
• To assess the sensitivity of spin relaxation to ionic strength in a biological model system.

Main Methods:

• Doping a nitroxide spin-labeled phospholipid into Triton X-100 micelles.
• Measuring spin-lattice relaxation (T1) at low temperatures (5-80 K).
• Varying KCl concentration (0-500 mM) to simulate physiological conditions.

Main Results:

• The spin-lattice relaxation mechanism varied in micelles compared to nonmicelle controls.
• Relaxation rates were sensitive to KCl concentration, decreasing with increasing salt.
• T1 relaxometry showed significantly higher sensitivity (30%) to KCl compared to pyrene fluorescence (<1%).

Conclusions:

• This study provides a proof-of-concept for investigating interfacial relaxation dynamics using spin qubits in biological systems.
• Spin relaxation demonstrates sensitivity to ionic strength, offering a novel quantum observable for probing biological microenvironments.