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Isolation and characterization of thermostable phycocyanin from Galdieria sulphuraria
Myounghoon Moon,양지원,Sanjiv K. Mishra,Chul Woong Kim,William I. Suh,Min S. Park 한국화학공학회 2014 Korean Journal of Chemical Engineering Vol.31 No.3
Phycocyanin is a highly valuable pigmented protein synthesized by several species of cyanobacteria andred alga. In this study we demonstrate the production of thermostable phycocyanin from the unicellular red alga Galdieriasulphuraria. Phycocyanin was extracted by repeated freeze-thaw cycles and purified in a two-step process using ammoniumsulfate fractionation, at 25% and 50% concentrations. Purified phycocyanin exhibited maximum absorbanceat 620 nm, and the purity ratio (A620/A280) was found to be greater than 4. The recovery efficiency of phycocyanin fromthe crude extract was above 80%. In total, approximately 19 milligram pure phycocyanin was obtained from 3 g ofwet cell mass of Galdieria sp. Subunits α and β of the protein were separated by SDS-PAGE and analyzed by MALDITOFmass spectrometry for identification, which confirmed that the isolated protein is phycocyanin. The molecularweight of α and β subunits of phycocyanin was found to be 17.6 and 18.4 kDa, respectively.
Improved Conductance Linearity and Conductance Ratio of 1T2R Synapse Device for Neuromorphic Systems
Moon, Kibong,Kwak, Myounghoon,Park, Jaesung,Lee, Dongwook,Hwang, Hyunsang IEEE 2017 IEEE electron device letters Vol.38 No.8
<P>We report on a 1-transisor/2-resistor (1T2R) synapse device with improved conductance linearity and conductance ratio under an identical pulse condition for hardware neural networks with high pattern-recognition accuracy. Utilizing an additional series-connected resistor, the conductance linearity of a synapse device was significantly improved owing to the reduced initial voltage drop on an resistive RAM (RRAM) device during depression conditions. Moreover, to maximize the conductance ratio of a synapse device, we utilized a steep subthreshold region of an MOSFET by a parallel connection of an RRAM and a transistor. A small change in voltage on the RRAM directly controlled the gate bias of the MOSFET, which causes a large change in the drain current. Compared with a conventional RRAM synapse device, the 1T2R synapse device shows an improved conductance linearity and conductance ratio (>x100). Finally, we confirmed an excellent classification accuracy by using a neural network simulation based on a multilayer perceptron.</P>