pH-Responsive Aminoproline-Containing Collagen Triple Helices.

Area of Science:

• Biochemistry and structural biology
• Peptide chemistry
• Materials science

Background:

• Collagen's thermal stability is crucial for its biological function.
• Tuning collagen stability requires understanding molecular interactions.
• Aminoproline (Amp) offers potential as a pH-responsive element.

Purpose of the Study:

• To investigate the use of (4S)- and (4R)-aminoproline (Amp) as pH-responsive probes.
• To modulate the thermal stability of collagen triple helices across varying pH conditions.
• To explore the impact of Amp's stereochemistry and positioning within collagen model peptides (CMPs).

Main Methods:

• Synthesis and incorporation of (4S)- and (4R)-configured aminoproline residues into collagen model peptides (CMPs).
• Thermal stability assays of Amp-containing CMPs across a range of pH values.
• Comparative quantum chemical calculations to analyze steric and stereoelectronic effects of substituents.

Main Results:

• Aminoproline (Amp) residues effectively tuned collagen triple helix stability in response to pH changes.
• The switch in Amp's ring pucker between amino and ammonium forms influences stability.
• Positioning and absolute configuration of Amp provide tunable control over helix stability.
• Quantum chemical calculations supported experimental findings on steric and electronic effects.
• Substitution of collagen's natural hydroxy group with certain electron-withdrawing groups is detrimental.

Conclusions:

• Aminoproline (Amp) serves as a versatile pH-responsive probe for modulating collagen triple helix stability.
• The stereoelectronic properties of Amp and its placement within CMPs are key to controlling thermal stability.
• Understanding these interactions is vital for designing collagen-based biomaterials and therapeutics.