Structural distributions from single-molecule measurements as a tool for molecular mechanics

Area of Science:

• Biophysics
• Polymer Physics
• Computational Chemistry

Background:

• Predicting complex system behavior often requires resource-intensive atomistic models.
• Characterizing molecular-level mechanical responses remains a significant challenge.
• Structural distribution offers a potential alternative for extracting mechanical properties.

Purpose of the Study:

• To demonstrate that structural distribution is an effective means for extracting molecular mechanical properties.
• To investigate the size-dependent mechanical responses of poly-L-proline peptides.
• To integrate single-molecule experiments with computational modeling for detailed conformational analysis.

Main Methods:

• Experimental determination of end-to-end distance distributions using single-molecule Förster-type resonance energy transfer (FRET) on poly-L-proline peptides (P(n)CG(3)K-biotin, n = 8, 12, 15, 24).
• Analysis of FRET data, comparing conformational distribution analysis with conventional methods.
• Fitting molecular conformational distributions to a semi-flexible polymer model and employing computational modeling.

Main Results:

• Conformational distribution analysis successfully distinguished between polymer models, unlike averaged end-to-end distances.
• Effective persistence lengths for poly-L-proline peptides were found to be size-dependent (~190 Å, ~67 Å, ~51 Å, ~76 Å for n = 8, 12, 15, 24).
• Computational modeling revealed distinct isomeric structures (all-trans, one-cis, two-cis) correlating with peptide size and conformational modes.

Conclusions:

• The distribution-based approach provides high resolving power for molecular mechanical properties.
• Single-molecule FRET combined with molecular modeling can reveal detailed molecular conformation.
• Size-dependent mechanical properties and specific isomeric conformations were elucidated for short poly-L-proline peptides.