Atomistic Simulation of Water Incorporation and Mobility in Bombyx mori Silk Fibroin.

Mathew John Haskew,Samuel Thomas Murphy,John George Hardy,Chin Weng Yong,Benjamin Deacon

doi:10.1021/acsomega.1c05019

Mathew John Haskew, Samuel Thomas Murphy + Show 3 more

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https://doi.org/10.1021/acsomega.1c05019

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Abstract

Bombyx mori silk fibroin (SF) is a biopolymer that can be processed into materials with attractive properties (e.g., biocompatibility and degradability) for use in a multitude of technical and medical applications (including textiles, sutures, drug delivery devices, tissue scaffolds, etc.). Utilizing the information from experimental and computational SF studies, a simplified SF model has been produced (alanine–glycine [Ala–Gly]n crystal structure), enabling the application of both molecular dynamic and density functional theory techniques to offer a unique insight into SF-based materials. The secondary structure of the computational model has been evaluated using Ramachandran plots under different environments (e.g., different temperatures and ensembles). In addition, the mean square displacement of water incorporated into the SF model was investigated: the diffusion coefficients, activation energies, most and least favorable positions of water, and trajectory of water diffusion through the SF model are obtained. With further computational study and in combination with experimental data, the behavior/degradation of SF (and similar biomaterials) can be elucidated. Consequently, greater control of the aforementioned technologies may be achieved and positively affect their potential applications.

Highlights

Silk fibroin (SF) from the Bombyx mori silkworm is an Ala−Gly-rich protein, which is spun from aqueous solutions to produce strong and tough fibers.[1,2] SF has excellent biocompatibility, making it a popular component of biomaterials.[3,4] Many attempts have been made to mimic the natural process of producing robust silk filaments under mild environmental conditions.[5−8] this has proven challenging, and many of the resultant fibers have been weaker than natural silk.[9]
In the density functional theory (DFT) case, hydrating the cell leads to an increase in the cell volume; in the classical MD, there is a slight decrease
The impact on the water on the secondary structure appears to be similar for both techniques as described . 2.2. (Ala−Gly)n SF Crystal Models’ Secondary Structure

Summary

INTRODUCTION

Gly-rich protein, which is spun from aqueous solutions to produce strong and tough fibers.[1,2] SF has excellent biocompatibility, making it a popular component of biomaterials.[3,4] Many attempts have been made to mimic the natural process of producing robust silk filaments under mild environmental conditions.[5−8] this has proven challenging, and many of the resultant fibers have been weaker than natural silk.[9]. The primary structure of B. mori SF contains a high content of (Ala− Gly)n,26 the SF can exist in either silk I or silk II form and its structural confirmations are less clear It is generally accepted[31−33] that silk II contains regions of orderly packed antiparallel β-sheets; the precise content varies between studies, which is in part caused by variations in experimental approaches/conditions and the variation of properties in natural materials.[34,35] As for silk I, the structural parameters remain unclear because this conformation is less stable and susceptible to transformation into the silk II conformation, leading to difficulty in performing an analysis (e.g., X-ray diffraction experiments). This will facilitate future studies that investigate the incorporation of other molecules (e.g., charged ions such as Na+ or Mg2+) within the silk model, expanding the potential in how this material could be applied

RESULTS AND DISCUSSION

CONCLUSIONS

METHODOLOGY

■ ACKNOWLEDGMENTS

■ REFERENCES