Judul: Karakterisasi awal protein diatom Chaetoceros gracilis yang terlibat dalam pembentukan biosilika
Abstrak: Penggunaan bahan berbasis silika sangat luas untuk berbagai bidang, termasuk bidang-bidang strategis di antaranya di industri biosensor, biomedik dan semikonduktor yang menggunakan silika dengan struktur nano sebagai mineral utama. Saat ini, metode pembuatan silika yang berlaku di industri memerlukan kondisi pH dan suhu ekstrim disertai penambahan surfiddm yang menghasilkan limbah talc ramah ligkungan. Penemuan protein yang terlibat dalam pembentukan silika pada biota laut seperti diatom dm sponge, membuka peluang penggunaan katalis biologis untuk membuat struktur silika yang spesifik dan teratur secara in vitro.
Keyword: 

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.
Keyword: 

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