Judul: In Silico Study of Mahogany Bark Active Compounds as  Inhibitor of RNA-dependent RNA polymerase and Endoribonuclease SARS-CoV-2 EPI_ISL_46737
Abstrak: RNA-dependent RNA polymerase dan endoribonuclease merupakan protein yang berperan dalam replikasi dan transkripsi SARS-CoV-2 penyebab Covid-19. Kulit kayu mahoni mengandung senyawa golongan polifenol yang memiliki aktivitas antivirus, antioksidan, dan antimikroba. Hingga saat ini belum ada riset senyawa aktif kulit kayu mahoni sebagai inhibitor protein RNA-dependent RNA polymerase dan endoribonuclease. Penelitian ini bertujuan untuk mempelajari interaksi senyawa aktif kulit kayu mahoni terhadap protein RNA-dependent RNA polymerase dan endoribonuclease SARS-CoV-2. Penelitian dilakukan secara in silico dengan teknik penambatan molekuler menggunakan program YASARA. Hasil penelitian dianalisis menggunakan parameter energi bebas Gibbs, konstanta disosiasi, dan interaksi residu. Swietemakrofilanin berpotensi dalam menghambat RNA-dependent RNA polymerase dengan ΔG -4,053 kkal/mol, Kd 1.069 µM, tiga ikatan hidrogen, enam interaksi hidrofobik. Katekin berpotensi dalam menghambat endoribonuclease dengan ΔG -1,700 kkal/mol, Kd 56.739 µM, satu interaksi hidrofobik. Berdasarkan hasil penambatan, kulit kayu mahoni memiliki potensi sebagai inhibitor RNA dependent RNA polymerase dan endoribonuclease SARS CoV-2., RNA-dependent RNA polymerase and endoribonuclease are proteins that play a role in the replication and transcription of SARS-CoV-2 that causes Covid 19. Mahogany bark contains polyphenolic compounds that have antiviral, antioxidant, and antimicrobial activity. Until now, there has been no research on the active compound of mahogany bark as an inhibitor of RNA-dependent RNA polymerase and endoribonuclease. This study aimed to study the interaction of active compounds from mahogany bark on RNA-dependent RNA polymerase and endoribonuclease SARS-CoV-2. The research was conducted in silico with molecular docking using YASARA program. The results were analyzed using Gibbs free energy, dissociation constants, and residual interactions parameters. Swietemacrophylllanin has the potential to inhibit RNA-dependent RNA polymerase with ΔG -4,053 kcal/mol, Kd 1,069 µM, three hydrogen bonds, six hydrophobic interactions. Catechin has the potential to inhibit endoribonuclease with ΔG -1,700 kcal/mol, Kd 56,739 µM, one hydrophobic interaction. Based on the results, mahogany bark has the potential as an inhibitor of RNA-dependent RNA polymerase and endoribonuclease SARS-CoV-2.
Keyword: Covid-19, Endoribonuklease, Katekin, RdRp, Swietemakrofilanin

Judul: Analisis Penambatan Molekuler Senyawa Aktif Kulit Kayu Gmelina arborea terhadap Endoribonuklease SARS-CoV-2
Abstrak: COVID-19 disebabkan oleh infeksi SARS-CoV-2, tingkat keparahannya beragam sesuai dengan tingkat kekebalan tubuh penderita. Aktivitas antioksidan dalam kulit kayu Gmelina berpotensi menurunkan aktivitas protein fungsional SARS-CoV-2. Penelitian ini bertujuan memperoleh informasi mencakup (1) situs pengikatan ligan-protein; (2) nilai ΔG dan konstanta disosiasi; (3) ikatan hidrogen dan interaksi hidrofobik antar molekul; (4) karakteristik kimia senyawa aktif kulit kayu Gmelina. Penelitian ini menggunakan metode in silico melalui penambatan molekuler secara komputasi dengan aplikasi YASARA structure. Berdasarkan hasil penelitian, senyawa balanophonin memiliki pengikatan yang paling baik dibandingkan senyawa aktif kulit kayu Gmelina lainnya dengan nilai ΔG -7,1270 kkal/mol serta konstanta disosiasi 5,96 μM. Dengan demikian, simpulan penelitian ini senyawa aktif balanophonin dengan pengikatan terbaik memiliki nilai ΔG lebih besar dari uridin-5’-monofosfat dan tipiracil, yang merupakan ligan alami dan pembandingnya. Ikatan hidrogen serta interaksi hidrofobik antar molekul memfasilitasi penambatan dan inhibisi aktivitas endoribonuklease SARS-CoV-2., COVID-19 is caused by infection of SARS-CoV-2, the severity based on patient's immune system. Antioxidant activity in Gmelina bark potentiates to decrease activities of SARS-CoV-2 functional protein. This study aims to obtain information including (1) ligand-protein binding sites; (2) the value of G and the dissociation constant; (3) intermolecular hydrogen bonds and hydrophobic interactions; (4) Chemical properties of active compound in Gmelina bark. This research uses in silico method through computational molecular docking with the YASARA structure application. Based on the results, balanophonin has the best binding affinity to other active compounds of Gmelina bark with the value of ΔG -7,1270 kcal/mol and dissociation constant of 5.96 μM. Thus, this study concludes balanophonin with the best binding has a ΔG value which larger than uridine-5'-monophosphate and tipiracil as their natural and comparison ligand. Intermolecular hydrogen bonds and hydrophobic interactions facilitate the binding and inhibition of SARS-CoV-2 endoribonuclease activity.
Keyword: Molecular Docking, Gmelina arborea, Endoribonuclease, SARS-CoV-2

Judul: Metrik Einstein (Anti-) Self-Dual Berdimensi Empat dengan Metode Cartan
Abstrak: Gravitational field equation can be formulated in differential forms (differential geometry), which describes gravity as a manifestation of the curvature of space-time. Curvature of space-time is characterized by a metric that satisfies the gravitational field equation. With differential forms it can be formulated the (anti-) self-dual Einstein equation, which is a modification of the Cartan structure in (anti-) self-dual basis. Calculation of (anti-) self-dual metric with (anti-) self-dual Einstein equation is simpler than the calculation using Christoffel symbols.
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