**E**ffi**cient Construction of Atomic-Resolution Models of Non-Sulfated Chondroitin Glycosaminoglycan Using Molecular Dynamics Data**

### **Elizabeth K. Whitmore 1,2 , Gabriel Vesenka <sup>1</sup> , Hanna Sihler <sup>1</sup> and Olgun Guvench 1,2,\***


Received: 26 February 2020; Accepted: 1 April 2020; Published: 2 April 2020

**Abstract:** Glycosaminoglycans (GAGs) are linear, structurally diverse, conformationally complex carbohydrate polymers that may contain up to 200 monosaccharides. These characteristics present a challenge for studying GAG conformational thermodynamics at atomic resolution using existing experimental methods. Molecular dynamics (MD) simulations can overcome this challenge but are only feasible for short GAG polymers. To address this problem, we developed an algorithm that applies all conformational parameters contributing to GAG backbone flexibility (i.e., bond lengths, bond angles, and dihedral angles) from unbiased all-atom explicit-solvent MD simulations of short GAG polymers to rapidly construct models of GAGs of arbitrary length. The algorithm was used to generate non-sulfated chondroitin 10- and 20-mer ensembles which were compared to MD-generated ensembles for internal validation. End-to-end distance distributions in constructed and MD-generated ensembles have minimal differences, suggesting that our algorithm produces conformational ensembles that mimic the backbone flexibility seen in simulation. Non-sulfated chondroitin 100- and 200-mer ensembles were constructed within a day, demonstrating the efficiency of the algorithm and reduction in time and computational cost compared to simulation.

**Keywords:** molecular dynamics; glycosaminoglycan; proteoglycan; chondroitin sulfate; carbohydrate conformation; carbohydrate flexibility; glycosidic linkage; ring pucker; force field; explicit solvent
