In Vitro Antioxidant and Antimicrobial Activities of Two Hawaiian Marine Limu: Ulva fasciata (Chlorophyta) and Gracilaria salicornia (Rhodophyta)

Kannappan Vijayavel,Jonathan A. Martinez 한국식품영양과학회 2010 Journal of medicinal food Vol.13 No.6

The antioxidant and antimicrobial properties of two Hawaiian marine algae (Ulva fasciata and Gracilaria salicornia) were evaluated. Ethanolic extracts of these two algae exhibited intracellular reactive 1,1-diphenyl-2-picrylhydrazyl, 2,2′-azino-bis(3-ethylbenzthiazoline)-6-sulfonic radical, nitric oxide, superoxide radical, and hydroxyl radical scavenging activities. In addition to the antioxidant activity these algae possessed appreciable antimicrobial activity and total phenolic contents. The overall results have established that these two marine algae could be used to derive bioactive compounds for a possible role as nutraceutical agents.

Asymmetrical Volume Loss in Hippocampal Subfield During the Early Stages of Alzheimer Disease: A Cross Sectional Study

Kannappan, Balaji The Basic Science Institute Chosun University 2018 조선자연과학논문집 Vol.11 No.3

Hippocampal atrophy is a well-established imaging biomarker of Alzheimer disease (AD). However, hippocampus is a non-homogenous structure with cytoarchitecturally and functionally distinct sub-regions or subfield, with each region performing distinct functions. Certain regions of the subfield have shown selective vulnerability to AD. Here, we are interested in studying the effects of normal aging and mild cognitive impairment on these sub-regional volumes. With a reliable automated segmentation technique, we segmented these subregions of the hippocampus in 101 cognitively normal (CN), 135 early mild cognitive impairment (EMCI), 67 late mild cognitive impairment (LMCI) and 48 AD subjects. Thereby, dividing the hippocampus into hippocampal tail (tail), subiculum (SUB), cornu ammonis 1 (CA1), hippocampal fissure (fissure), presubiculum (PSUB), parasubiculum (ParaSUB), molecular layer (ML), granule cells/molecular layer/dentate gyrus (GCMLDG), cornu ammonis 3(CA3), cornu ammonis 4(CA4), fimbria and hippocampal-amygdala transition area (HATA). In this cross sectional study of 351 ADNI subjects, no differences in terms of age, gender, and years of education were observed among the groups. Though, the groups had statistically significant differences (p < 0.05 after the multiple comparison correction) in the Mini-Mental State Examination (MMSE) scores. There was asymmetrical volume loss in the early stages of AD with the left hemisphere showing volume loss in regions that were unaffected in the right hemisphere. Bilateral parasubiculum, right cornu ammonis 1, 3 and 4, right fimbria and right HATA regions did not show any volume loss till the late MCI stages. Our findings suggest that the hippocampal subfield regions are selectively vulnerable to AD and also that these vulnerabilities are asymmetrical especially during the early stages of AD.

DNA-Wrapped CNT Sensor for Small Nucleic Acid Detection: Influence of Short Complementary Sequence

Shrute Kannappan,장준혁,라마사미 순달바부 브리얀트,허준혁,성원기,노재철,김경규,John Bosco Balaguru Rayappan,이정헌 한국바이오칩학회 2022 BioChip Journal Vol.16 No.4

Carbon nanotubes (CNTs) are versatile materials that act as natural fluorescence quenchers and double scaffolds for DNA that can wrap around them based on π–π stacking. We exploited these properties of CNTs to develop a hybridization-based sensor for the detection of microRNA. We designed a fluorescein amidite (FAM)-labeled single-stranded oligonucleotide containing a CNT binding region (Poly T) followed by a sequence complementary to the target nucleic acid (probe sequence). As the DNA wraps around a CNT, FAM fluorescence is quenched in the absence of the target, whereas in the presence of the target, fluorescence emission is obtained. Experimentally, we found that one of the major issues with this sensor is its compromised sensitivity due to competition for adsorption of the probe DNA onto the CNT versus that of hybridization with the target DNA. To overcome this, we introduced a short complementary sequence (SCS) that binds to the probe sequence and found that it significantly improved the limit of detection of the sensor approximately 25-fold. To gain further insights into the mechanism of SCS in improving the sensor performance, we performed molecular dynamics (MD)-based simulations. Based on hybridization energy calculations performed using MM-GBSA, we found that the position of the SCS is key to shaping the binding affinity of the probe to the CNT. The MD-based calculations were validated using experimental results by comparing the sensor’s experimental limit of detection and the hybridization energy obtained computationally. Finally, we demonstrated the applicability of this sensor for the experimental detection of the cervical cancer-related biomarker miR-21-5p in human serum.

Asymmetrical Volume Loss in Hippocampal Subfield During the Early Stages of Alzheimer Disease : A Cross Sectional Study

Balaji Kannappan 조선대학교 기초과학연구원 2018 조선자연과학논문집 Vol.11 No.3

Study on the Effects of H+ and He+ Implantation in Semi-Insulating GaAs by Using Raman Spectroscopy

santhakumar kannappan,Cheul-Ro LEE,Hayakawa Y,Jayavel P,Jin soo Kim,Kesavamoorthy R,Muraleedaran Nair,Tetsuo soga 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.51 No.2I

Fifty-keV hydrogen-ion (H$^+$) and 70-keV helium-ion (He$^+$) implantation with doses from 10$^{13}$ to 10$^{16}$ cm$^{-2}$ in semi-insulating (100) gallium-arsenide (GaAs) single- crystal substrates have been carried out. Raman spectra of as-grown, implanted, and post-implantation-annealed GaAs samples are analyzed. Two LO phonon modes have been observed for all the samples. The lower wavenumber peak is attributed to the strained surface layer whereas the higher wavenumber peak is due to bulk GaAs crystal. For H$^+$ implantation, the peak positions of both peaks shift towards lower wavenumber up to a dose of 10$^{14}$ cm$^{-2}$ due to passivation of charge carriers. For higher doses, the peak positions shift towards higher wavenumber due to hydrogen-filled vacancy loops. On the other hand, for He$^+$-implanted samples, the peak positions increase for doses up to 10$^{13}$ cm$^{-2}$ and then decrease at higher doses. The immiscible nature of helium at low doses causes the increase in the peak positions. In contrast, implantation-induced damage is dominant at higher doses. Implantation-induced defects are partially annealed by post-implantation annealing, causing a blueshift of the peak positions for the H$^+$-implanted samples. In He$^+$-implanted samples, the peak positions redshift due to annealing of He interstitials at low doses and blueshift due to annealing of implantation-induced defects at high doses.

Examining the Effect of Additives and Thicknesses of Hole Transport Layer for Efficient Organic Solar Cell Devices

Shizuyasu Ochiai,Palanisamy Kumar,Kannappan Santhakumar,신백균 대한금속·재료학회 2013 ELECTRONIC MATERIALS LETTERS Vol.9 No.4

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), a conducting polymer, has been receiving a great deal of attention for next generation optoelectronic organic devices. In this report, we discuss the effect of additives along with the thickness of PEDOT:PSS layers on the power conversion efficiency of organic solar cell devices. PEDOT:PSS films treated with high boiling point solvents of dimethyl sulfoxide (DMSO) and ethylene glycol (EG) show a significant enhancement in electrical conductivity without compromising flexibility or optical transparency. The conductivity increased from 0.5 to 517 and 724 S/cm after once and thrice treatment with 4 vol. % EG, respectively. The as-prepared and additives-treated PEDOT:PSS films deposited on glass substrates have been investigated by optical spectroscopy, micro-Raman spectroscopy and atomic force microscopy (AFM). The results indicate that structural and morphological changes were induced by the additive processes. By using DMSO and EG treated PEDOT:PSS as a hole transport layer,organic solar cells with a Poly[[9-(1-octylnonyl)-9H-carbazole-2,7-diyl]-2,5-thiophenediyl-2,1,3-benzothiadiazole-4,7-diyl-2,5-thiophenediyl]:[6,6]-phenyl-C71-butyric acid methyl esters (PCDTBT:PC71BM) bulk heterojunction have been fabricated on indium-tin-oxide (ITO) coated glass substrates. The high power conversion efficiency (PCE) of 5.17%, and 5.69%, were observed for PEDOT:PSS hole transport layers treated with DMSO and EG respectively, even though the devices were prepared in air atmosphere.

RBP2 induces stem-like cancer cells by promoting EMT and is a prognostic marker for renal cell carcinoma

Dahai Zhou,Vinodh Kannappan,Xiang Chen,Jingqin Li,Xuefeng Leng,Jinping Zhang,Shiying Xuan 생화학분자생물학회 2016 Experimental and molecular medicine Vol.48 No.-

Renal cell carcinoma (RCC), one of the most common kidney cancers, has a poor prognosis. Epithelial to mesenchymal transition (EMT) is a hallmark of carcinoma invasion and metastasis. Several studies have examined the molecular regulation of EMT, but the relationship between histone demethylases and EMT is little understood. In this study, we investigated the role of retinoblastoma-binding protein-2 (RBP2), a histone demethylase that is highly expressed in RCC and is positively correlated with poor RCC prognosis in the regulation of EMT. We found that ectopic overexpression of RBP2 can induce cancer stem cell-like (CSC) phenotypes through EMT in RCC cells by converting them to a more mesenchymal phenotype. This results in increased resistance to apoptosis, which leads to enhanced tumor growth in xenograft models. Together, our data show that RBP2 is an epigenetic regulator that has an important role in the initiation of CSC phenotypes through EMT, leading to tumor progression. RBP2 is also a novel biomolecule for RCC diagnosis, and prognosis and may be a therapeutic target.

Evaluation of the Performance of an Organic Thin Film Solar Cell Prepared Using the Active Layer of Poly[[9-(1-octylnonyl)-9H-carbazole-2.7-diyl]-2.5-thiophenediyl-2.1.3-benzothiadiazole-4.7-Diyl-2.5-thiophenediyl]/[6,6]-Phenyl C₇₁ Butyric Aci

Ochiai, Shizuyasu,Uchiyama, Masaki,Kannappan, Santhakumar,Jayaraman, Ramajothi,Shin, Paik-Kyun The Korean Institute of Electrical and Electronic 2012 Transactions on Electrical and Electronic Material Vol.13 No.1

Organic solar cell devices were fabricated using poly[9-(1-octylnonyl)-9H-carbazole-2.7-diyl]-2.5-thiophenediyl-2.1.3-benzothiadiazole-4.7-diyl-2.5-thiophenediyl] PCDTBT/ [6,6]-phenyl $C_{71}$ butyric acid methyl ester (PC71BM) active layer deposited by spin coating. Moreover, the relationship between solar cell performance and buffer layer thickness was investigated by spin coating speed and AFM imaging of the buffer layer surface. The performance of the organic solar cell with spin-coated active layer was then evaluated, and the power conversion efficiency of the solar cell was determined to be > 5%.

High-performance Organic Solar Cells based on a Low-bandgap Poly-thienothiophene-benzodithiophene Polymer and Fullerene Composite Prepared by using the Airbrush Spray-coating Technique

Palanisamy Kumar,Santhakumar Kannappan,Shizuyasu Ochiai,신백균 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.62 No.8

In the present work, we have demonstrated high-performance organic solar cells with spray coated active layers. The influence of the nanomorphology on the power conversion efficiency of poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b’]dithiophene-2,6-diyl] [3-fluoro-2-[(2-ethylhexyl)carbonyl] thieno[3,4-b]thiophenediyl]] (PTB7):[6,6]-phenyl-C71-butyric acid (PC71BM)methyl ester bulk heterojunction solar cells is presented. Active layers were prepared using a chlorobenzene solvent containing a small volume of 1,8-diiodooctane as an additive by spray coating with conventional handheld airbrushes. The surface morphology of the active layers deposited for various spray-coating times was examined using atomic force microscopy. The resulting devices were measured under AM 1.5G (100 mW/cm2) conditions in an ambient atmosphere. The optimized spray-coated PTB7:PC71BM film showed a high solar cell performance with a short-circuit current density of 14.20 ± 0.41 mA/cm2, a fill factor of 56.00 ± 0.02% and a power conversion efficiency of 5.96 ± 0.15%.

Fluorinated Copper-phthalocyanine-based <i>n</i>-type Organic Field-effect Transistors with a Polycarbonate Gate Insulator

Kunjithapatham Sethuraman,Palanisamy Kumar,Kannappan Santhakumar,Shizuyasu Ochiai,신백균 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.61 No.1

Fluorinated copper-phthalocyanine (F₁₆CuPc) thin films were prepared by using a vacuum evaporation technique and were applied to <i>n</i>-type organic field-effect transistors (OFETs) as active channel layers combined with a spin-coated polycarbonate thin-film gate insulator. The output characteristics of the resulting <i>n</i>-type OFET devices with bottom-gate/bottom-contact structures were investigated to evaluate the performances such as the field effect mobility (<i>μ_FE</i>), the on/off current ratio (<i>I_on/off</i>), and the threshold voltage (<i>V_th</i>). A relatively high field effect mobility of 6.0 × 10⁻³ cm²/Vs was obtained for the n-type semiconductor under atmospheric conditions with an on/off current ratio of 1 × 10⁴ and a threshold voltage of 5 V. The electron mobility of the n-type semiconductor was found to depend strongly on the growth temperature of the F₁₆CuPc thin films. X-ray diffraction profiles showed that the crystallinity and the orientation of the F₁₆CuPc on a polycarbonate thin film were enhanced with increasing growth temperature. Atomic force microscopy studies revealed various surface morphologies of the active layer. The field effect mobility of the F₁₆CuPc-OFET was closely related to the crystallinity and the orientation of the F₁₆CuPc thin film.