Judul: Karakteristik Protein Serupa Silicatein Dari Sponge Asal Perairan Nias Dan Lombok
Abstrak: Penggunaan bahan dasar silika yang berstruktur nano di industri pangan makin berkembang sebagai bahan pengemas aktif, biosensor, penyaring dan antikoagulan. Saat ini bahan dasar silika berstruktur nano dilakukan dengan proses yang menggunakan suhu, pH dan tekanan yang ekstrim serta menggunakan surfaktan. Cara lain untuk membuat silika berstruktur nano adalah menggunakan biokatalis protein serupa silicatein. Protein silicatein diisolasi dari sponge laut diketahui dapat membantu polimerisasi silika pada substrat Tetraethylorthosilicate (TEOS) pada suhu ruang dan pH netral. Sponge yang digunakan dalam penelitian ini berasal dari perairan Nias (N6 dan N20) dan perairan Lombok (MT5, MT36, MT37), Indonesia. Protein diperoleh dengan cara mengisolasi spikula silika terlebih dahulu dari tubuh sponge menggunakan larutan Natrium Hipoklorit 10%. Rendemen spikula silika tertinggi yang diperoleh dengan perendaman larutan 3N HNO3/ 3N H2SO4 dan pencucian dengan aseton 2x diperoleh dari sponge MT37 yaitu sebesar 58% dari berat kering sponge. Rendemen protein tertinggi yang diperoleh dari pelarutan silika spikula dengan larutan buffer 2.5 mM HF/NH4F pH 5 selama 2 jam adalah dari sponge N6, N20, MT5, MT36, MT37 berturut-turut sebesar 3.11%, 0.30%, 3.93%, 7.32% dan 58.5% dari berat kering sponge. Dengan metode Bradford, kandungan protein tertinggi spikula silika adalah dari sponge N6, MT5, MT36, MT37 yaitu 0.012 mg/ml, 0.042 mg/ml, 0.05 mg/ml dan 0.21 mg/ml. Hasil analisa SDS-PAGE menunjukkan bahwa berat molekul protein serupa silicatein dari spons N6 adalah 32, 27, 23 kD sedangkan MT36 dan MT37 adalah 15.5 kD dan 18kD. Ekstrak protein serupa silicatein sebanyak 250 ml dengan kandungan protein sebanyak 0.004 mg/ml direaksikan dengan 1 ml TEOS 13.5 μmol yang diinkubasi selama 12 jam pada pH 6.8 suhu 26oC menghasilkan aktivitas polimerisasi tertinggi sebesar 144 μmol/ml. Penghambatan aktivitas protein dari sponge MT37 dan MT5 oleh senyawa Phenylmethylsulfonylfluorida (PMSF) 1mM sebesar 38.8% dan 35.5% menunjukkan bahwa protein serupa Silicatein yang diisolasi diduga kuat mempunyai sisi aktif serin. Hasil studi kinetika reaksi menunjukkan bahwa reaksi protein serupa silicatein dari sponge MT37 dengan TEOS mengikuti persamaan Michaelis-Menten dengan nilai Vmax yang diperoleh adalah 0.001 μmol/detik, nilai Km yang sebesar 0.01 μmol/ml dan nilai Kcat adalah 0.04 μmol/detik.
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Judul: Eksplorasi Protein dari Sponge Asal Perairan Pulau Nias dan Binuangeun yang Mengkatalisis Polimerisasi Silika
Abstrak: Silica, polymerized silicon dioxide, was widely used as raw materials for industries, such as food industry, semiconductor, electronic and medical equipment. Marine sponges (Phylum porifera) were living system that can produce a remarkable diversity of nanostructured silicates at ambient temperature and near-neutral pH. In contrast to living system, synthesis of these materials in industry require extreme of temperature, pressure, and pH with addition surfactant that can cause environmental pollution. Isolating protein that can catalyze nanostructured silica polymerization will make a new route for silica development under mild conditions using protein/enzyme biocatalyst. This research was aimed to extract and analyze protein from Nias Island Sea sponges and Binuangeun Sea sponges and to study their activity to polymerize tetraethoxyorthosilicate (TEOS). Protein in silica spicule of sponge was isolated by collecting silica spicule and soaked in HF/NH4F buffer (pH 5,0) for dissolving silica and releasing this protein. Then, protein was dialyzed and centrifuged. Activity of this protein to polymerize substrate tetraethoxyorthosilicate was measured by colorimetric molybdate assay. Protein of Sponge ST1 (from Binuangeun Sea) and protein of Sponge ST3 (from Nias Island Sea) have the same moleculer weight about 21.4 kDa and the same shape (filament) and size. Both of them have the length approximately 0,1 mm and diameter 10 mm. Protein of Sponge ST1 (250 ml, protein concentration less than 5 mg/ml) could polymerize 15,9 μmol TEOS after 12 hours reaction at room temperature and near-neutral pH and protein of Sponge ST3 could polymerize 3,0 μmol TEOS in the same reaction conditions. Silica formed from polymerization reaction by protein Sponge ST1 during 48 hours, coated this protein and increased its diameter four times. Sponge ST5, ST6 and ST7 which have unique microscleres silica spicule were potential to become sources of protein that can catalyze unique shape of biosilica. Sponges which have no silica spicule such as Sponge St8 and ST9 were not potential to become protein sources.
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Judul: Dynamical System of Hepatitis B in Three Groups with Vaccination
Abstrak: The aim of this study is to modify the hepatitis B transmission model in three age groups involving vaccination from the model conducted by Zhoe and Zhang.The method used is to analyze the stability of the fixed point and its basic reproduction number (R_0). Performed stability analysis and numerical simulation to see population dynamics. Next, a sensitivity analysis of the parameters was carried out to see its effect on R_0. From the analysis obtained two fixed points, namely non-endemic and endemic fixed points. Non-endemic fixed points are locally asymptotically stable if R_0 <1 Meanwhile, the endemic fixed point is locally asymptotically stable if R_0 > 1. Hepatitis vaccination affects the number of susceptible population, because the more successful the vaccination, the smaller the number of susceptible populations so that the smaller the population will be infected.
Keyword: Dynamic, Hepatitis B, Vaccine, Mathematical model