To help control the global pandemic of coronavirus disease 2019 (COVID-19), we developed a diagnostic method targeting the spike protein of the virus that causes the infection, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We applied an ultrasensitive method by combining a sandwich enzyme-linked immunosorbent assay (ELISA) and the thio-nicotinamide adenine dinucleotide (thio-NAD) cycling reaction to quantify spike S1 proteins. The limit of detection (LOD) was 2.62 × 10-19 moles/assay for recombinant S1 proteins and 2.6 × 106 RNA copies/assay for ultraviolet B-inactivated viruses. We have already shown that the ultrasensitive ELISA for nucleocapsid proteins can detect ultraviolet B-inactivated viruses at the 104 RNA copies/assay level, whereas the nucleocapsid proteins of SARS-CoV-2 are difficult to distinguish from those in conventional coronaviruses and SARS-CoV. Thus, an antigen test for only the nucleocapsid proteins is insufficient for virus specificity. Therefore, the use of a combination of tests against both spike and nucleocapsid proteins is recommended to increase both the detection sensitivity and testing accuracy of the COVID-19 antigen test. Taken together, our present study, in which we incorporate S1 detection by combining the ultrasensitive ELISA for nucleocapsid proteins, offers an ultrasensitive, antigen-specific test for COVID-19.
Recent investigations have suggested that CagA, a virulence factor of Helicobacter pylori and known to have multiple genotypes, plays a critical role in the development of stomach cancer. However, the prevalence of cagA-positive H. pylori strains and the cagA genotypes have not been well studied in healthy individuals because of the difficulty in collecting gastric specimens. In the present study, we assessed the prevalence of infection with H. pylori, particularly the strains with the East Asian cagA genotype (which is more potent in causing gastric diseases), among healthy asymptomatic Japanese individuals by a noninvasive method using stool specimens. The H. pylori antigen was detected in 40.3 % of healthy asymptomatic adult individuals (n=186) enrolled in the study. For the detection and genotyping of the cagA gene, DNA was extracted from the stool specimens of these individuals and analysed by PCR. We detected the East Asian cagA genotype in the DNA samples of a significantly high number (63.1 %) of healthy asymptomatic Japanese individuals. These results indicate that a significant number of asymptomatic healthy Japanese individuals were infected with highly virulent H. pylori.
ObjectivesTo determine the prevalence of CTX-M β-lactamase-producing Enterobacteriaceae in stool specimens obtained from healthy individuals in a rural area of Thailand.
In this paper we propose a new metric of SRAM cell stability named static cell-flip voltage (SCFV). In order to measure SCFV, novel design-for-test (DFT) techniques with asymmetric cell-bias-voltage modulation (ACBVM) are introduced, in which the cell-data retention is measured with sweeping potential of a ground node connected to one of the cross-coupled invertors of a cell and source voltage of PMOS loads swept. It is shown that SCFV has high correlation with conventional static noise margin (SNM). The proposed techniques make it possible to directly obtain large amounts of stability data of memory cells arranged in matrix for an SRAM macro, which has been difficult with conventional SNM measurements. The measured data of 1 Kb SRAM with 65 nm technology show good correspondence with simulated results.
Abstract Immunoglobulin A (IgA) has been showing potential as a new therapeutic antibody. However, recombinant IgA suffers from low yield. Supplementation of the medium is an effective approach to improving the production and quality of recombinant proteins. In this study, we adapted IgA1-producing CHO-K1 suspension cells to a high concentration (150 mM) of different disaccharides, namely sucrose, maltose, lactose, and trehalose, to improve the production and quality of recombinant IgA1. The disaccharide-adapted cell lines had slower cell growth rates, but their cell viability was extended compared to the nonadapted IgA1-producing cell line. Glucose consumption was exhausted in all cell lines except for the maltose-adapted one, which still contained glucose even after the 9th day of culturing. Lactate production was higher among the disaccharide-adapted cell lines. The specific productivity of the maltose-adapted IgA1-producing line was 4-fold that of the nonadapted line. In addition, this specific productivity was higher than in previous productions of recombinant IgA1 with a lambda chain. Lastly, secreted IgA1 aggregated in all cell lines, which may have been caused by self-aggregation. These results suggest that a high concentration of disaccharide-supplemented induced hyperosmolarity in the IgA1-producing CHO-K1 cell lines. In addition, the maltose-adapted CHO-K1 cell line benefited from having an additional source of carbohydrate.
We report on stabilization of CMOS power transistors employing a new layout concept. We assume that instability of power transistors is caused by intensified impact ionization at the pinch-off channels, and that the impact ionization is synchronized with acoustic standing waves in the device area if they are designed with conventional layout configurations. In the new layout design, gate fingers are electrically connected in parallel, but thermally and geometrically isolated from one another at random intervals. The shape of the device area is deformed so that acoustic waves are scattered at the boundaries of device area surrounded by shallow trench isolation (STI). Measurements demonstrated that the stability of transistors has been improved. For example, a transistor with a gate width of 800 mum has shown the 1 dB-compression point P 1dB of 15 dB m and the saturation power P SAT of 21 dB m at 2.45 GHz under a bias condition for linear operation. The results indicate that the CMOS transistors are suitable for power amplifiers, especially, for full integration of wireless transceivers.
