Secondary metabolites (Triterpenes) from Couroupita guianensis

Rokeya Begum,Mohammad S Rahman,A M Sarwaruddin Chowdhury,Choudhury M Hasan,Mohammad A Rashid 경희대학교 융합한의과학연구소 2009 Oriental Pharmacy and Experimental Medicine Vol.9 No.2

The n-hexane and carbon tetrachloride soluble fractions of a methanolic extract of the stem bark of the Couroupita guianensis furnished three compounds, identified as β-amyrin (1), betulin-3β- caffeate (2) and lupeol-3β-caffeate (3). The structures of the isolated compounds were deduced by extensive spectroscopic analysis as well as by comparison with published values. Compounds 1-3 were subjected to antioxidant screening through free radical scavenging activity by DPPH (1,1- diphenyl-2-picrylhydrazyl), where compound 2 showed moderate antioxidant activity with IC50 value 108.0 μg/ml. The n-hexane and carbon tetrachloride soluble fractions of a methanolic extract of the stem bark of the Couroupita guianensis furnished three compounds, identified as β-amyrin (1), betulin-3β- caffeate (2) and lupeol-3β-caffeate (3). The structures of the isolated compounds were deduced by extensive spectroscopic analysis as well as by comparison with published values. Compounds 1-3 were subjected to antioxidant screening through free radical scavenging activity by DPPH (1,1- diphenyl-2-picrylhydrazyl), where compound 2 showed moderate antioxidant activity with IC50 value 108.0 μg/ml.

The role of Rho GTPases in the regulation of the rearrangement of actin cytoskeleton and cell movement

Rokeya Begum,M.S.A. Nur-E-Kamal,M.A. Zaman 생화학분자생물학회 2004 Experimental and molecular medicine Vol.36 No.4

The rearrangement of the actin cytoskeleton has been shown to play a critical role in the development of transformation and m alignant phenotype of cancer cells. Rho family GTPases regulate the arrangement of the actin cytoskeleton. By wound-healing assay, we have found that NIH 3T3 fibroblast cells move towards the woundgaps by extending filopodial and lamellipdial structures at the leading edge of the moving cells. We have inactivated the function of Rho GTPases of v-Ras transformed NIH 3T3 cells by overexpressing Rho GTPase-activating (RhoGAP) domain of RhoGAP of p190. W e have observed that inactivation of Rho, Rac and Cdc42 GTPases by overexpressing RHG causes inhibition of: (i) polymerization of actin to form filaments, (ii) formation of lamellipodia, filopodia and stress fibres, (iii) cell m otility, (iv) cell spreading and (v) cell-to-cell adhesions. These results further strengthen the current knowledge on the role of Rho, Rac and Cdc42 GTPases in the regulation of the rearrangement of actin cytoskeleton. Our results, for the first time, demonstrate that RhoGAP domain of RhoGAP could be used to study the m olecular mechanism of Ras-mediated signalling in growth, differentiation and carcinogenesis.

Secondary metabolites (Triterpenes) from Couroupita guianensis

Begum, Rokeya,Rahman, Mohammad S,Chowdhury, A M Sarwaruddin,Hasan, Choudhury M,Rashid, Mohammad A Kyung Hee Oriental Medicine Research Center 2009 Oriental pharmacy and experimental medicine Vol.9 No.2

The n-hexane and carbon tetrachloride soluble fractions of a methanolic extract of the stem bark of the Couroupita guianensis furnished three compounds, identified as $\beta$-amyrin (1), betulin-$3{\beta}$-caffeate (2) and lupeol-$3{\beta}$-caffeate (3). The structures of the isolated compounds were deduced by extensive spectroscopic analysis as well as by comparison with published values. Compounds 1-3 were subjected to antioxidant screening through free radical scavenging activity by DPPH (1,1-diphenyl-2-picrylhydrazyl), where compound 2 showed moderate antioxidant activity with $IC_{50}$ value $108.0{\mu}g/ml$.

Survey on Nucleotide Encoding Techniques and SVM Kernel Design for Human Splice Site Prediction

Bari, A.T.M. Golam,Reaz, Mst. Rokeya,Choi, Ho-Jin,Jeong, Byeong-Soo Korean Society for Bioinformatics 2012 Interdisciplinary Bio Central (IBC) Vol.4 No.4

Splice site prediction in DNA sequence is a basic search problem for finding exon/intron and intron/exon boundaries. Removing introns and then joining the exons together forms the mRNA sequence. These sequences are the input of the translation process. It is a necessary step in the central dogma of molecular biology. The main task of splice site prediction is to find out the exact GT and AG ended sequences. Then it identifies the true and false GT and AG ended sequences among those candidate sequences. In this paper, we survey research works on splice site prediction based on support vector machine (SVM). The basic difference between these research works is nucleotide encoding technique and SVM kernel selection. Some methods encode the DNA sequence in a sparse way whereas others encode in a probabilistic manner. The encoded sequences serve as input of SVM. The task of SVM is to classify them using its learning model. The accuracy of classification largely depends on the proper kernel selection for sequence data as well as a selection of kernel parameter. We observe each encoding technique and classify them according to their similarity. Then we discuss about kernel and their parameter selection. Our survey paper provides a basic understanding of encoding approaches and proper kernel selection of SVM for splice site prediction.

Highly efficient green, blue, and white phosphorescent inverted organic light-emitting diodes by improving charge injection and balance

Lee, Hyunkoo,Maeng, Min-Jae,Hong, Jong-Am,Najnin, Rokeya,Moon, Jaehyun,Cho, Hyunsu,Lee, Jonghee,Yu, Byoung-Gon,Park, Yongsup,Cho, Nam Sung The Royal Society of Chemistry 2017 Journal of Materials Chemistry C Vol.5 No.38

<▼1><P>Highly efficient green, blue, and white phosphorescent inverted organic light-emitting diodes were demonstrated by improving charge injection and balance.</P></▼1><▼2><P>To improve the performance of inverted organic light-emitting diodes (OLEDs), we investigated the electrical, optical, and interfacial properties of three different lithium (Li)-doped electron transport materials (ETMs): tris(3-(3pyridyl)mesityl)borane (3TPYMB), 1,3,5-tri(m-pyrid-3-yl-phenyl)benzene (TmPyPB), and 1,3-bis(3,5-dipyrid-3-yl-phenyl)benzene (BmPyPB). The electron injection barriers (EIBs) between indium-tin-oxide and the ETMs were deduced for both pristine and Li-doped cases from ultraviolet photoelectron spectroscopy measurements and optical band gap values. The Li-doped ETMs showed EIB values of approximately 0.03 eV, 0.77 eV, and 0.81 eV for 3TPYMB, TmPyPB, and BmPyPB, respectively, which are much lower than those of their pristine counterparts of 0.94 eV, 1.14 eV, and 1.48 eV, respectively. The Li-doped ETMs were employed as electron injection layers (EILs) of inverted bottom-emission OLEDs (IBE-OLEDs) with green phosphorescence. IBE-OLEDs with 3TPYMB, TmPyPB, and BmPyPB EILs exhibited driving voltages of 3.6 V, 4.0 V, and 4.5 V at 1000 cd m<SUP>−2</SUP> and maximum external quantum efficiencies (EQEs) of 20.3%, 19.7%, and 16.5%, respectively. From the low EIB of Li-doped 3TPYMB, we also demonstrated highly efficient blue and white phosphorescent IBE-OLEDs. We optimized the device structure to improve the charge balance and out-coupling efficiency by changing the hole injection layer and the thickness of the hole and electron transport layers with optical simulation. The blue device showed a maximum EQE and luminous current efficiency of 22.9% and 43.1 cd A<SUP>−1</SUP>, respectively. In addition, the white device exhibited a high EQE and luminous efficacy of 19.3% and 37.8 lm W<SUP>−1</SUP> at 3 mA cm<SUP>−2</SUP> (∼1000 cd m<SUP>−2</SUP>), respectively. To the best of our knowledge, the efficiencies of these green, blue, and white devices are the highest values obtained to date with a low driving voltage for IBE-OLEDs without any additional light-extraction structure. Since the Li-doped 3TPYMB has an extremely low EIB and shows good device performance, it can be utilized as an effective EIL in inverted-structure devices.</P></▼2>

Codon-based encoding for DNA sequence analysis

Jeong, B.S.,Golam Bari, A.T.M.,Rokeya Reaz, Mst.,Jeon, S.,Lim, C.G.,Choi, H.J. Academic Press 2014 Methods Vol.67 No.3

With the exponential growth of biological sequence data (DNA or Protein Sequence), DNA sequence analysis has become an essential task for biologist to understand the features, functions, structures, and evolution of species. Encoding DNA sequences is an effective method to extract the features from DNA sequences. It is commonly used for visualizing DNA sequences and analyzing similarities/dissimilarities between different species or cells. Although there have been many encoding approaches proposed for DNA sequence analysis, we require more elegant approaches for higher accuracy. In this paper, we propose a noble encoding approach for measuring the degree of similarity/dissimilarity between different species. Our approach can preserve the physiochemical properties, positional information, and the codon usage bias of nucleotides. An extensive performance study shows that our approach provides higher accuracy than existing approaches in terms of the degree of similarity.