Judul: Penentuan Keterulangan Biosensor Antioksidan dari Ekstrak Deinococcus radiodurans dan Perbandingan Metode Elektrokimia dengan Spektrofotometri
Abstrak: Biosensor electrochemical method for antioxidant is an alternative method in measuring the capacity of antioxidant. This method has higher sensitivity, lower cost and simple instrumentation compare to spectrophotometry. The objective of this research was to optimize the activity of SOD extract of immobilized zeolite-Deinococcus radiodurans, repeatabillity, and the comparison of detection limit between electrochemical and spectrophotometry method. The optimum condition of SOD antioxidant activity of D. radiodurans extract was obtained at temperature of 31 °C, pH 9, and zeolites 137.5 mg. The optimum current obtained from the repeatibility was 1.749 μA with standard deviation of 0.01, and coefficient of variation of 0.59%. Detection limit of electrochemical biosensor was 1.76 ppm, while spectrophotometry has lower detection limit with value of 2.01 ppm. Electrochemical method can be used to detect lower concentrations analytes.
Keyword: superokside dismutase, limit of detection, repeatibility, D. radiodurans, antioxidant biosensor

Judul: Aktivitas dan Stabilitas Superoksida Dismutase dari Ekstrak Deinococcus radiodurans yang Diimobilisasi pada Zeolit Alam sebagai Biosensor Antioksidan
Abstrak: Immobilization of superoxide dismutase (SOD) from extract of Deinococcus radiodurans have been studied. D. radiodurans is a bacteria having an enzyme Mn-SOD. The optimum condition of SOD antioxidant activity of the extract was at 31 °C, pH 9, and 157 mg zeolite. Determination of Michaelis-Menten constant was based on Lineweaver- Burk, Eadie-Hoofstee, and Hanes methods. The KMapp of SOD of the extract immobilized on zeolite was lower than that of without immobillization. Electrode stability was relatively stable up to 22 hours. Antioxidant activity of using zeolite as the matrix was higher than that of the unimmobilization. The antioxidant activity on electrode with zeolite at 22nd hour was 64.0 %, and the stability of electrodes without zeolite at the same time was only 49.3 %. The SOD of D. radiodurans is potential as a biosensor for antioxidants because of the high antioxidant activity despite of the low stability.
Keyword: superoxide dismutase, natural zeolites, Deinococcus radiodurans, antioxidant biosensor

Judul: Closed Knight’s Tour pada Papan Catur Berbentuk Persegi Panjang dengan Ukuran Maksimal 8 × 8
Abstrak: Closed Knight’s Tour merupakan langkah kuda yang mengunjungi setiap kotak pada papan catur tepat satu kali dengan langkah kuda berawal dan berakhir pada kotak yang sama. Graf yang terbentuk dari closed knight’s tour dinotasikan sebagai graf G(m,n), dengan m adalah banyaknya baris dan n adalah banyaknya kolom. Graf tersebut memuat Hamiltonian cycle. Sebuah graf terhubung G adalah graf bipartite jika dan hanya jika graf tersebut tidak memiliki cycle dengan panjang ganjil. Papan catur yang memenuhi syarat cukup untuk memiliki closed knight’s tour adalah papan catur berukuran 5 × 6, 5 × 8, 6 × 6, 6 × 7, 6 × 8, 7 × 8, dan 8 × 8.
Keyword: bipartite, closed knight’s tour, hamiltonian cycle, knight’s tour, teori graf