Adiabatic compressibility of globular proteins

Area of Science:

• Biophysics
• Physical Chemistry
• Protein Science

Background:

• Proteins are essential macromolecules with complex structures and functions.
• Understanding protein dynamics and compressibility is crucial for elucidating their biological roles.
• Previous studies have explored various physical properties of proteins, but compressibility data remains limited.

Purpose of the Study:

• To measure the adiabatic compressibility of globular proteins using ultrasonic techniques.
• To differentiate between contributions to compressibility from the protein matrix and surface processes.
• To investigate the implications of compressibility measurements for protein internal dynamics and structure.

Main Methods:

• Adiabatic compressibility measurements were performed on globular proteins.
• An ultrasonic technique was employed across a frequency range of 0.5 to 10 MHz.
• Analysis focused on separating contributions from the protein matrix, side-chain ionization, and solvation effects.

Main Results:

• The adiabatic compressibility of several globular proteins was successfully measured.
• A very low internal protein compressibility was observed.
• Surface processes, including side-chain ionization and solvation, were identified as significant contributors to the overall compressibility.

Conclusions:

• The low internal compressibility of proteins supports the existence of "dynamic domains."
• These dynamic domains are tentatively assigned to secondary structure elements within the proteins.
• The findings provide insights into the mechanical properties and structural organization of globular proteins.