Judul: Identification of Biomarker Peptide Gelatin Raw Materials through Mass Spectroscopy using Bioinformatics Techniques
Abstrak: Gelatin, a partial hydrolysis product of animal collagen has been widely used in Indonesia processing industry. The source of gelatin, however, is strictly regulated due to religious concern. Thus, the method that could differentiate the source of gelatin is needed. This research was aimed to predict biomarker peptides using bioinformatics approach that could be used to differentiate the source of gelatin by means of mass spectrometry. Collagen sequences from cattle, pigs, chickens, and fish were obtained from the UniProt database. The sequences were in silico digested using trypsin and chymotrypsin in PeptideMass software. The resulting peptides were filtered following the criteria for mass spectrometry. In general, trypsin digestion produced higher number of specific peptides compared to that of chymotrypsin enzyme. The number of peptide sequences resulting from hydrolysis with the chymotrypsin indicates the enzyme is less specific in cutting protein than the trypsin enzyme. Trypsin is more suitable for finding biomarkers than chymotrypsin. Some of the specific peptides detected can be used to differentiate the species from which gelatin is derived.
Keyword: bioinformatics, enzyme, gelatin, mass spectrometry, specific peptide

Judul: Differentiation of Porcine and Bovine Gelatin and Their Admixture Using SPME-GCMS Method and Multivariate Analysis
Abstrak: Gelatin merupakan produk hidrolisis parsial dari kolagen. Bahan baku gelatin sebagian besar berasal dari kulit babi, kulit sapi, tulang babi, dan tulang sapi. Gelatin dibedakan dengan memanfaatkan salah satu sifat gelatin, yaitu aroma khas berupa komponen volatil yang berasal dari bahan bakunya. Sampel dianalisis menggunakan metode solid phase microextraction (SPME) dan gas chromatography–mass spectrometry (GC-MS) serta analisis multivariat. Hasil analisis multivariat principle component analysis (PCA) dan partial least square-discriminant analysis (PLS-DA) menunjukkan bahwa sampel gelatin babi dan gelatin sapi dapat terklasifikasi dengan baik. Namun, sampel gelatin campuran tidak dapat terklasifikasi dengan baik. Hasil analisis senyawa volatil penanda yang berpengaruh pada pengklasifikasian kelas gelatin babi ialah 3-tetradekun-1-ol, 1,1,2-trimetilsikloundekana, (E)-2-dodeken-1-al, 8-hidroksi-2,2-dimetil-dek-5-en-3-on, dan (E)-2-undeken-1-ol. Senyawa volatil penanda yang berpengaruh pada pengklasifikasian kelas gelatin sapi ialah 1-pentakosena, 3,7-dimetildekana, N-(1-feniletil)formamida, 5-metiltetradekana, dan heksil sianoasetat., Gelatin is a product of partial hydrolysis of collagen. Most of the raw materials for gelatin come from pork skins, cow skins, pork bones, and cow bones. Gelatin can be differentiated by using one of the gelatin's characteristics: distinctive aroma originated by volatile components of the raw material. The samples were analyzed using solid-phase microextraction (SPME), gas chromatography-mass spectrometry (GC-MS), and multivariate analysis. The results of the principal component analysis (PCA) dan partial least square-discriminant analysis (PLS-DA) showed that the samples of porcine gelatin and bovine gelatin could be classified well. However, the mixed gelatin samples could not be classified properly. The volatile marker compounds that affected the classification of porcine gelatin classes are 3-tetradecyn-1-ol, 1,1,2-trimethylcycloundecane, (E)-2-dodecen-1-al, 8-hydroxy-2,2-dimethyl-dec-5-en-3-one, and (E)-2-udecen-1-ol. The volatile marker compounds that affected the classification of bovine gelatin classes are 3,7-dimethyldecane, N-(1-phenylethyl)formamide, 5-methyltetradecane, and hexyl cyanoacetate.
Keyword: gelatin, GC-MS, SPME, volatilomics

Judul: Bifurkasi Hopf pada Model Siklus Bisnis Kaldor Kalecki tanpa dan dengan Waktu Tunda
Abstrak: Business cycle model is one of dynamical system models in economic. One of the business cycles model is Kaldor-Kalecki model. Kaldor-Kalecki business cycle model that is written in delayed defferential equations, is a business cycle model that involves gross product and capital stock of a company. In this paper Kaldor-Kalecki business cycle model is analyzed using both nondelay and delay in time of capital stock. By Taylor expansion for the time delayed model, an analysis of stability around the fixed points has been done. Furthermore, by using Hopf bifurcation theorem, it can be shown that there exists periodic orbits and limit cycle. In the nondelayed model, changing the parameter of goods market could lead to the occurrence of Hopf bifurcation and the existence of limit cycle. Similarly, for the delayed model, it has been shown that changing the time delay parameter may result in the occurrence of Hopf bifurcation and limit cycle.
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