Dataset from DFT Calculations and RDG Analysis for Interactions in a Chitosan/Cassava Starch/Anthocyanin Composite Film
Description
1 Research Hypothesis: This research hypothesizes that at the pH condition (4.4) of the film-forming solution, chitosan (CH), cassava starch (CS), and purple sweet potato anthocyanin (PSPA) can form stable complexes through non-covalent interactions. These molecular-level interactions, primarily hydrogen bonds and van der Waals forces, are responsible for the enhanced mechanical properties and structural compactness observed in the composite film, and underpin its function as a pH-responsive indicator for pork freshness. 2 What the Data Shows: Individual Component Calculations: Chitosan.gjf, Chitosan.chk, Chitosan-ESP.txt: DFT input, output, and electrostatic potential data for chitosan tetramer cassava_starch.gjf, cassava_starch.chk, cassava_starch-ESP.txt: DFT input, output, and ESP data for starch tetramer carbinol_pseudobase.gjf, carbinol_pseudobase.chk, carbinol_pseudobase-ESP.txt: DFT input, output, and ESP data for anthocyanin derivative Complex Calculations: Chitosan-carbinol_pseudobase.gjf, Chitosan-carbinol_pseudobase.chk: DFT input and output for chitosan-anthocyanin complex cassava_starch-carbinol_pseudobase.gjf, cassava_starch-carbinol_pseudobase.chk: DFT input and output for starch-anthocyanin complex Chitosan-carbinol_pseudobase-RDG-output.txt, cassava_starch-carbinol_pseudobase-RDG-output.txt: Non-covalent interaction analysis results 3 Notable Findings and Interpretation: The ESP analysis revealed that protonated chitosan has a strong positive potential around its -NH₃⁺ groups, making it an excellent hydrogen bond donor. PSPA and starch showed significant negative potential around their oxygen atoms, acting as hydrogen bond acceptors. Molecular docking corroborated this, identifying five hydrogen bonds in the CH-PSPA complex and two in the CS-PSPA complex. The short bond distances (< 2.9 Å) indicate stable and favorable interactions. The NCI analysis provided direct evidence of these non-covalent interactions, with clear blue isosurfaces (signifying strong hydrogen bonds) and green regions (signifying van der Waals interactions) between the molecules. This computational evidence strongly supports the experimental FTIR and XRD findings that hydrogen bonding is a key mechanism within the film matrix.
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Steps to reproduce
Computational Workflow and Protocols: 1. Molecular Modeling and Preparation: Chitosan: A tetramer was constructed by truncating and protonating the structure from PubChem (CID 71853) to reflect the protonated (-NH₃⁺) state at pH 4.4. Starch: An amylose tetramer was obtained from the GLYCAM resource (https://glycam.org). PSPA (Anthocyanin): The carbinol pseudobase form was modeled by modifying the structure of delphinidin (PubChem CID 128853). Pre-optimization: All initial structures were pre-optimized using the MMFF94 force field. 2. Quantum Chemical Calculations (DFT): Software: Gaussian 16. Geometry Optimization & Frequency: All structures were fully optimized. Methodology: The B3LYP functional with the GD3BJ empirical dispersion correction and the SMD implicit solvation model (water) was used. Basis Sets: The 6-31+G(d,p) basis set was used for chitosan and starch. The 6-311+G(d,p) basis set was used for the PSPA carbinol pseudobase. Analysis: Molecular ESP maps were generated from the optimized structures and visualized using Multiwfn and VMD. 3. Molecular Docking: Software: AutoDock Vina. Procedure: Docking simulations were performed to predict the binding configurations between PSPA and chitosan, and PSPA and starch. Visualization: The resulting complexes were visualized and rendered using PyMOL. 4. Post-docking DFT and NCI Analysis: Single-point Energy Calculations: The docked complex configurations were subjected to DFT single-point energy calculations at the B3LYP/6-311+G(d,p) level of theory using Gaussian 16. NCI Plot Generation: The wavefunction files from the single-point calculations were analyzed using the RDG method in Multiwfn. The grid for the RDG analysis was defined by selecting the option to input grid spacing and specifying a value of 0.08 Bohr for the X, Y, and Z directions, ensuring a high-quality and consistent resolution for the non-covalent interaction isosurfaces and scatter plots, which were subsequently visualized in VMD.
Institutions
- Xiangtan University