The Effect of Configuration to Interaction Energy Between The Segments of Chitosan and Ascorbic Acid Molecule: Theoretical Study of Drug Release Control

Polymer systems plays an important role in drug delivery, which can control the time release of the drug, reduce the rate of degradation of the drug, and can reduce the toxic properties of the drug. Chitosan is a polymer of N-acetyl glucosamine that is biocompatible, biodegradable, and have active groups that can be used as a drug carrier matrix to control the release rate of the drug in the human body. The related research has been conducted experimentally by applying chitosan as a matrix to control the release rate of ascorbic acid by in vitro in an aqueous medium. So that, this study aimed to describe the interactions that occur between segments of chitosan and ascorbic acid theoretically using ab initio computational methods. Software used is Gaussian03, while the level of theory and basis set calculations determined is HF-SCF / 6-31G (d, p). The results for the nine configuration interaction calculations indicate hydrogen bonds between ascorbic acid molecules and chitosan segment. The interaction energy obtained is different for each configuration. It can be used as a basis for explaining the gradual release of ascorbic acid molecule from chitosan matrix. Ascorbic acid molecules that bound to the matrix of chitosan with lower energy will be easier to release on the medium that used

DFT Study on the Reaction Mechanism of Cyclization of 2-Hydroxy Chalcone Catalyzed by Bronsted Acid with M06-2X Functional

Flavanones are one of the flavonoid group that has wide variety of applications such as a precursors in drug discovery. In the laboratory, flavanone is often synthesized from chalcone compounds. The conversion of chalcone to flavanone can be catalyzed by bronsted acid. The reaction mechanism for this process is proposed through the Michael addition reaction, however, the energetic details and the rate determining step for this reaction is not certainly known. This research aimed to investigate the reaction mechanism for chalcone-flavanone conversion with the present of bronsted acid as catalyst and also studied the effect of the solvent on the reaction energy profile with computational method. In this study, the modeling of the reaction mechanism for the said reaction was carried out using the DFT computational method with M06-2X functional. The computation was done both in the gas phase and in present of the solvent effect using the PCM models. The results showed that the mechanism of chalcone-flavanone conversion occurred in three steps which are protonation, cyclization, and then tautomerization. Based on these calculations, the rate determining step was the tautomerization reaction, which exhibited the same results with or without the solvent effects. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

SISTEM PENDUKUNG KEPUTUSAN KELAYAKAN PESERTA LELANG TENDER PEMERINTAH MENERAPKAN PROMETHEE II

A tender auction is a series of processes from bidding made by the contractor to the decision of the contractor selected as the winner of the tender. The selected contractor will carry out the work in the field in accordance with the rules and procedures issued by the government. The submission process to be a more selective list of bidders makes the government use a decision support system that can provide effective information to the selected tender participants so that the decisions that the government produces are better and more objective. The application of the Promethee II method in supporting the feasibility decision of tender participants is very optimal because each alternative will be compared with each other so that the results obtained from the comparison are the best

Structural Stability of ADTC5 Peptide: Conformational Insights into Dynamics and Its Binding Mode

The cyclic structure of ADTC5 (Ac-CDTPPVC-NH2) peptide is known has ability to modulate homo dimer E-cadherin interactions to form adherens junction at the intercellular junction.  The ability to inhibit E-cadherin interaction has become important to increase paracellular porosity in delivering drug molecules to the target cell. There are two types of ADTC5 state: opened-cyclic state (OCS) and closed-cyclic state (CCS). OCS of ADTC5 is affected by distance constraint and CCS is formed by disulfide bond from terminal cysteines through force restraint. The aim of this research is to investigate the inhibition activity of ADTC5 peptide upon E-cadherin. Here we used molecular docking and molecular dynamics approaches. The structure of ADTC5 peptide was generated by PyMOL program. GROMACS v4.5.5 was utilized to simulate molecular dynamics. The optimized ADTC5 molecule was placed in aqueous or polar condition at physiological pH. Furthermore, ADTC5 was docked with EC1-EC2 coupled domain of E-cadherin using AutoDock 4.2 and be refined using molecular dynamic (MD). The result showed that CCS ADTC5 peptide has stronger affinity and more stable interaction with EC1-EC2 coupled domain than the OCS one

The Optimum Conditions of Carboxymethyl Chitosan Synthesis on Drug Delivery Application and Its Release of Kinetics Study

In this paper, carboxymethyl chitosan (CMC) was synthesized and studied as a carrier to encapsulate vitamin (as drug model) and controlled release. Chitosan (CS) is a polycationic derivated from chitin, which suitable for active substance carrier system on biomedical function. CS has good properties such as non-toxic, biodegradable, and biocompatible. However, CS insoluble in an aqueous solvent so CS was modified chemically into CMC. CMC was formed by reacting CS and monochloroacetic acid with sodium hydroxide (NaOH) as a catalyst. Optimation was performed by varying the NaOH concentration during alkalizing the CS and the temperature reaction. The functional group and crystallinity of CS and CMC were estimated by FTIR and XRD. The degree substitution of carboxymethylation has an average value of 0.60. The results show optimum temperature reaction and NaOH concentration were 60 °C and 40% (w/v). The nicotinamide (NA), a hydrophilic vitamin, was loaded within CMC matrix system through in vitro precipitation method. To confirm the encapsulation of NA in CMC and the release kinetics of NA from CMC in distilled water was studied through UV-Vis spectrophotometry. The release profile of NA from CMC matrix system carried out for 3 h and 12 h. The rate of NA release from CMC increases with increasing time and the follows a zero order, Higuchi, and Korsmeyer-Peppas kinetics rules