Effect of d-amino acids on collagen fibrillar assembly and stability: Experimental and modelling studies

• EDC/NHS in the presence of d-AAs improves the stability and flexibility.
• d-Lys has accelerated self-assembly and staggered alignment of collagen fibril.
• d-Lys has the lowest binding energy with CLP when compared to d-Ala and d-Glu.
• Orientational changes in ChC on CLP-d-Lys decreases its accessibility.
• Creates new topologies inaccessible and resistance to collagenase activity.

The effect of selected d-amino acids (d-AAs) on collagen with 1-ethyl-3-(3-dimethylamino propyl)carbodiimide (EDC)/N-hydroxysuccinimide (NHS) initiated crosslinking is evaluated by using experimental and modelling tools. The experimental results suggest that d-Lysine (d-Lys) plays a pivotal role in the self-assembly and conformation of collagen fibrils than d-Alanine (d-Ala) and d-Glutamic acid (d-Glu). The SDS-PAGE, absorption spectrum and viscosity measurements indicate significant differences in the d-Lys crosslinked collagen when compared to other systems. The CD spectra show an increase in the peak intensity at 220 nm in the presence of d-Lys, which could be due to increase in propensity of the structure to form a triple helix. Modelling studies indicated that d-Lys bind with collagen-like peptide (CLP) through multiple H-bonding and hydrophobic interactions. d-Lys has the lowest binding energy (−4.2 kcal/mol, indicating strongest interactions) when compared to d-Ala and d-Glu (−3.6 and −3.7 kcal/mol, respectively). Orientational changes in the collagenase on CLP-d-Lys are observed which may decrease its accessibility to degradation and stabilise CLP against the action of the former. d-Lys has the lowest binding energy and improved fibrillar-assembly and staggered alignment without the undesired structural stiffness and aggregations. The information derived from the present study could help in designing heterochiral collagen-based biomaterial.

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