*3.3.9 Molecular docking analysis*

The molecular docking is an excellent and an efficient computational technique, which is used to predict the probable binding site of interaction of protein with the ligand/drug molecule and also the preferred binding site of the ligand through the 3-D graphics [4, 11, 47, 99]. Moreover, it also displays the amino acid residues encircling the ligand/drug molecule and also assists to validate the results and highlights the interaction types operating in the protein–ligand/drug system [4, 99, 100]. To study the interaction in the Lyz–RxAc system, molecular docking studies were carried out with Autodock Vina software to clarify the mode of binding between lysozyme and Roxatidine acetate and illustrate the underlying mechanism. For further study, the lowest energy was chosen that was found to be 5.5 kcal/mol (23.01 kj/mol), which is near to the experimental data of ΔG° in thermodynamic analysis (22.25 kj/mol). In the Lyz–RxAc system (**Figure 17A** and **B**), the molecular docking showed the site of binding of RxAc along the long large pocket between the two domains of Lyz, which is also its site of active binding [101], and also showed that there were approximately three sites for binding of RxAc with lysozyme via hydrogen bonds at the lowest energy (Asn46 "two bonds" and Asp52 "one bond") (**Figure 18A** and **B**). The three sites of binding were all located in the large pocket of lysozyme. There were two hydrogen bonds between Asn46 and RxAc that were formed; one bond was between the hydrogen atom of Asn46 and the oxygen atom (C]O) of Roxatidine acetate, and another hydrogen bond was between the other hydrogen atom of Asn46 and the oxygen atom of Roxatidine

*Docking interaction of Lyz-RxAc binding, (A) The lysozyme pocket when RxAc was added. (B) Gaussian contact maps superimposed with the RxAc ligand and the receptor lysozyme, hydrogen bonds preference was indicated.*

*Influence of Tween 80 Surfactant on the Binding of Roxatidine Acetate and Roxatidine… DOI: http://dx.doi.org/10.5772/intechopen.100734*

**Figure 18.**

*(A) Amino acid residues surrounding RxAc. (B) 2-Dimentional representation of Lyz-RxAc system.*

acetate (CdOdC). The third hydrogen bond was between the oxygen atom of Asp52 and the hydrogen atom (NH) of Roxatidine acetate. The dominant fluorophores (Trp62 and Trp63) were involved in the binding sites through hydrophobic interaction via Pi–alkyl binding, which could illustrate the observed quenching of fluorescence, whereas the aliphatic amino acid (Ala107) also formed hydrophobic interaction through alkyl–alkyl binding; in addition, the oxygen atom of Asp52 formed electrostatic binding with the phenyl ring of Roxatidine acetate, as shown in **Figures 17B** and **18A,B**. Molecular docking studies have explained that hydrogen bonding was the dominant driving force in the binding of RxAc to lysozyme, and these results were in accordance with the results of thermodynamic analysis and UV spectroscopy.

#### **4. Conclusion**

In the present study, the RxAc drug–loaded Tween80–Chitosan nanoparticles (RxAcNPs) have been characterized and probed through FTIR, PXRD, UV–Vis, DLS, and SEM techniques. The physicochemical properties of RxAcNPs have been employed and evaluated for drug formulation, determination of external morphology, particle size, drug content, entrapment efficiency, and in vitro release of drugs. In addition, the RxAc and RxAcNPs interactions with Lyz have been investigated utilizing spectroscopic methods such as fluorescence, UV–Vis, and CD spectroscopy. The results of Stern–Volmer plots illustrate that the interaction mechanism of Lyz–RxAc and Lyz–RxAcNPs systems was a static mechanism. In the presence of RxAc and RxAcNPs, the secondary construction of Lyz is reformed. The results of synchronous fluorescence and CD spectra confirm that the RxAc and RxAcNPs cause change in the secondary construction of Lyz. The thermodynamic results clarify that the main forces in both systems were hydrogen bonds and Van der Waals forces, also revealing that the reaction of binding in both systems is spontaneous, exothermic, and enthalpically driven. The molecular docking results were in accordance with the results of thermodynamic analysis, UV–Vis, and CD spectroscopy. The present study illustrates that the binding of RxAcNPs with Lyz is low as compared to RxAc, which confirms that the distribution and absorption of the RxAcNPs to various tissues would be higher. Therefore, the result of this study has a great importance in the clinical medicine and pharmacology area and provides important insight into the interaction of serum albumins with antiulcer drugs.

The significance of this study is evident because the developed RxAc-loaded Tween80–Chitosan nanoparticles could be utilized as an efficient strategy using nanotechnology in applications of ulcer therapy.
