Judul: Simulasi Model Biosensor Berbasis Multi Enzim dengan Penambahan Faktor pH
Abstrak: Penelitian ini membahas mekanisme difusi reagen pada biosensor berbasis multi enzim. Model yang digunakan dibentuk dari persamaan difusi dengan faktor nonlinier Michaelis-Menten akibat reaksi kimia yang terjadi pada membran katalitik. Persamaan difusi tersebut direkonstruksi sehingga hanya mengandung besaran tak berdimensi dan diselesaikan menggunakan metode beda hingga eksplisit. Pada penelitian ini, faktor pH lingkungan dipertimbangkan dan dimasukan kedalam model biosensor berbasis multi enzim. Solusi numerik berupa mekanisme difusi dan keluaran fluks listrik diperoleh pada variasi pH lingkungan tertentu. Secara keseluruhan solusi numerik model tersebut menunjukkan bahwa pada pH yang tinggi laju difusi berlangsung lebih cepat dan keluaran fluks listrik lebih besar. Selain itu, pH lingkungan dapat mempengaruhi besar signifikansi dari kondisi parameter kimia yang berbeda seperti konstanta laju reaksi dan konstanta disosiasi asam-basa., This research discusses the mechanism of reagent diffusion in multi-enzyme-based biosensors. The model used is formed from the diffusion equation with the Michaelis-Menten nonlinear factor due to chemical reactions that occur in the catalytic membrane. The diffusion equation is reconstructed so that it only contains dimensionless quantities and being solved using the explicit finite difference method. In this study, environmental pH factors were considered and included in the multi-enzyme-based biosensor model. Numerical solutions in the form of diffusion mechanisms and electric flux outputs are obtained at some environmental pH variations. Overall, the numerical solution of the model shows that at high pH the diffusion rate is faster and the electric flux output is greater. In addition, the environmental pH can significantly affect the conditions of different chemical parameters such as the reaction rate constant and the acid-base dissociation constant.
Keyword: biosensor multi enzim, metode beda hingga, biosensor berbasis pH, kinetika enzimatik, multi-enzyme biosensor, finite difference method, pH based biosensor, enzyme kinetics

Judul: Simulation of One Enzyme-Based Biosensor Model with the Addition of pH Factor
Abstrak: Model matematika pada biosensor berbasis satu enzim dengan penambahan pH didasarkan pada sistem persamaan difusi dan reaksi bergantung waktu yang menggambarkan mekanisme laju reaksi substrat dan produk yang sesuai dengan reaksi katalis Michaelis-Menten. Model tersebut dideskripsikan melalui bentuk persamaan diferensial parsial, lalu persamaan tersebut diubah dalam bentuk tak berdimensi dengan cara mereduksi parameter-parameter dari persamaan. Persamaan tersebut diselesaikan menggunakan metode beda hingga secara eksplisit dan perangkat lunak MATLAB. Hasil simulasi divalidasi melalui proses kekekalan massa pada reaksi substrat dan produk. Solusi numerik dari penelitian ini dapat menggambarkan konsentrasi substrat dan produk serta respons arus listrik di dalam lapisan enzimatik ketika ditambahkan pH. Perubahan nilai parameter-parameter dalam model dapat menyebabkan perubahan dalam proses laju difusi dan reaksi. Penambahan pH dalam simulasi ini mempercepat laju reaksi substrat-produk serta melihat lebih teliti puncak arus listrik yang dihasilkan pada saat biosensor bekerja. Model biosensor berbasis satu enzim dengan penambahan pH ini diharapkan dapat dikembangkan lebih lanjut dengan fokus pada jenis enzim dan analit yang spesifik. Nilai parameter-parameter yang digunakan dalam penelitian ini dapat disempurnakan melalui studi literatur ataupun eksperimen untuk lebih mengoptimalkan model ini., The mathematical model of a single enzyme-based biosensor with pH addition is based on a system of time-dependent diffusion and reaction equations that describe the mechanism of substrate and product reaction rates corresponding to the Michaelis-Menten catalyst reaction. The model is described through the form of partial differential equations, then the equations are converted into dimensionless form by reducing the parameters of the equations. The equation is solved using the explicit finite difference method and MATLAB software. The simulation results are validated through the mass conservation process in the substrate and product reactions. The numerical solution of this study can describe the substrate and product concentrations as well as the electric current response in the enzymatic layer when pH is added. Changes in the values of the parameters in the model can cause changes in the diffusion and reaction rate processes. The addition of pH in this simulation accelerates the substrate-product reaction rate and looks more closely at the peak of the generated electric current when the biosensor is working. This single enzyme-based biosensor model with pH addition is expected to be further developed with a focus on specific types of enzymes and analytes. The values of the parameters used in this research can be refined through literature studies or experiments to further optimize this model.
Keyword: biosensor, enzim, metode beda hingga, pH, biosensor, enzyme, finite difference method, pH

Judul: Lejeuneaceae Subfamily Ptychanthoideae (Hepaticae) in  West Java
Abstrak: Subfamily Ptychanthoideae of the family Lejeuneaceae (Hepaticae) in West Java is still poorly known. Publications on this subfamily are out of dated and written in the 19th or early of 20th century. The last taxonomic treatment of Ptychanthoideae of West Java was in 1933, many species names have changed since then. Studies on Ptychanthoideae of West Java are urgently needed. Studies on the Ptychanthoideae were based on the specimens collected from West Java. A total number of 361 of specimens deposited in the Herbarium Bogoriense (BO), Herbarium Biotrop (BIOT), Gottingen Herbarium (GOET) and Bangi Herbarium (UKMB) were examined, those are old and several recent specimens collected in West Java. Recent collections were made from Telaga Warna, Ciater, Gunung Halimun Salak National Park, Cibodas Botanical Garden, Bodogol Education Center and Conservation (Gunung Gede Pangrango National Park), University of Indonesia Campus Depok, including several collections from Banten Province. Twenty four species of Lejeuneaceae subfamily Ptychanthoideae are known from West Java, belonging to 8 genera namely Acrolejeunea (Spruce) Schiffn. (2 species), Archilejeunea (Spruce) Schiffn. (1 species), Lopholejeunea (Spruce) Schiffn. (10 species), Mastigolejeunea (Spruce) Schiffn. (3 species), Ptychanthus Nees (1 species), Schiffneriolejeunea Verd. (1 species), Spruceanthus Verd. (2 species) and Thysananthus Lindenb. (4 species). Two new records of Ptychanthoideae: Mastigolejeunea indica Steph. and Thysananthus minor Verdoorn are reported for Java. A determination key to the species is presented including their descriptions and illustrations.
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