Terahertz Dynamics in Human Cells and Their Chromatin

Area of Science:

• Biophysics
• Cellular Dynamics
• Terahertz Spectroscopy

Background:

• Understanding the collective dynamics of biological systems at the molecular level is crucial.
• Human U937 cells and their chromatin exhibit complex dynamic behaviors that are not fully characterized.
• Terahertz spectroscopy offers a unique window into low-frequency vibrational modes in biological matter.

Purpose of the Study:

• To investigate the terahertz dynamics of human U937 cells and their chromatin in situ.
• To identify and characterize the collective dynamics and vibrational modes within cellular structures.
• To provide experimental evidence for specific dynamic branches in chromatin.

Main Methods:

• High-resolution inelastic X-ray scattering (HI-IXS) was employed to probe terahertz dynamics.
• Human U937 cell line was used for the investigation.
• Nuclear DNA was stained with uranyl-acetate salt to enhance dynamical feature visualization.

Main Results:

• The collective dynamics of whole U937 cells resemble bulk water, showing a wavevector-independent branch at ~5 meV and a sound speed of ~2900 m/s.
• First experimental evidence of two distinct branches in chromatin dispersion curves was observed.
• Chromatin exhibits a high-energy acoustic-like mode and a distinctive low-energy optic-like branch at ~2.5 meV.

Conclusions:

• The terahertz dynamics of U937 cells are comparable to bulk water, indicating conserved collective motion properties.
• Chromatin possesses unique terahertz dynamic features, including specific acoustic and optic-like branches.
• These findings advance the understanding of molecular dynamics within human cells and their genetic material.