Virology 306: [244][245][246][247][248][249][250][251][252][253] 2003). Previous data also suggested that a certain protein(s) synthesized only at 41°C inhibited the association of M1 with vRNP. The potential of heat shock protein 70 (HSP70) as a candidate obstructive protein was investigated. Induction of HSP70 by prostaglandin A1 (PGA1) at 37°C caused the suppression of virus production. The nuclear export of viral proteins was inhibited by PGA1, and M1 was not associated with vRNP, indicating that HSP70 prevents M1 from binding to vRNP. An immunoprecipitation assay showed that HSP70 was bound to vRNP, suggesting that the interaction of HSP70 with vRNP is the reason for the dissociation of M1. Moreover, NS2 accumulated in the nucleoli of host cells cultured at 41°C, showing that the export of NS2 was also disturbed at 41°C. However, NS2 was exported normally from the nucleus, irrespective of PGA1 treatment at 37°C, suggesting that HSP70 does not influence NS2.Influenza virus is an enveloped RNA virus belonging to the orthomyxovirus family. The viral genome consists of eight segments of negative-sense RNA which are bound to viral RNA polymerases and nucleoprotein (NP) to form a viral ribonucleoprotein complex (vRNP). When a host cell is invaded, influenza virus delivers its vRNP into the nucleus and replicates its genome. vRNP also acts as a template for mRNAs encoding virus-specific proteins. Although the viral proteins are synthesized in the cytoplasm, NP and RNA polymerases are imported into the nucleus to form new vRNP with a replicated genome. The assembly of influenza viral components, however, occurs at the plasma membrane. Therefore, new vRNP must be exported from the nucleus into the cytoplasm for viral offspring production (16). Matrix protein 1 (M1) and nonstructural protein 2/nuclear export protein (NS2/NEP) are known to be necessary for the nuclear export of vRNP (4,19,20,21,24,30). Both proteins also migrate into the nucleus and associate with vRNP (10,19,28,32,33) for transportation via the cellular machinery for nuclear export, dependent on chromosome region maintenance 1 (CRM1) protein (9,18,21).It was previously reported that influenza virus production is suppressed at 41°C in Madin-Darby canine kidney (MDCK) cells but is normal at 37°C (24). Virus-specific proteins are synthesized and vRNP is formed even at 41°C; however, vRNP cannot be exported from the nucleus at 41°C. This failure in vRNP export is due to M1 not interacting with vRNP, demonstrating that the association of M1 with vRNP is essential for the nuclear export of vRNP. To investigate why M1 is not bound to vRNP at 41°C, viral proteins were labeled with [ 35 S]methionine at 37°C, and the M1-vRNP complex formed at 37°C was chased after the culture temperature was raised to 41°C. The temperature rise caused the release of M1 from vRNP; the M1-vRNP complex formed at 37°C was dissociated at 41°C. However, in this experiment, it was found incidentally that the dissociation of the M1-vRNP complex was inhibited if the infected cells were...

A surface plasmon resonance (SPR) sodium ion sensor using an ion optode membrane film was experimentally and theoretically described based on an absorption-based SPR principle proposed in our previous article (Kurihara, K; Suzuki, K. AnaL Chem. 2002, 74, 696-701). The sodium ion concentrations from 10(-6) to 10(-1) have been successfully determined not only by the resonance angle diagnosis of the SPR curve but also by the minimum reflectance one. The ion optode film was plasticized poly(vinyl chloride) including a neutral sodium ionophore, a pH-sensitive cationic dye, and an anionic additive. Its optical absorption intensity changed with the sodium ion concentrations. The SPR ion sensor physically measured the complex refractive index caused by the absorption in the ion optode film. We have exhaustively investigated the experimental response behavior of the SPR curve relative to the sodium ion concentrations by comparison with numerically simulated SPR curves using a three-layer Fresnel equation including experimental values for the sodium ion optode membrane film. As predicted by the absorption-based SPR principle, the SPR curve behavior of the SPR ion sensors depended on two factors: one was the relation between the excitation frequency of the light source and the absorption maximum frequency in the ion optode film while the other was the gold metallic thickness in the Kretchmann configuration. The concept and practical theory of an absorption-based SPR sensor not only have been proved by the experimental results of the SPR sodium ion sensor but also have successfully allowed flexible ion sensing in an SPR sensor, which would be very difficult without the absorption mechanism in the ion optode film.

A new optical analytical method, "Digital Color Analysis (DCA)", is proposed based on a digital color analyzer instead of the conventional optical methodology, "Spectrophotometry". The digital color analyzer is a hand-held-size instrument for measuring "colors", and it can transform the color information into numerical values, color library data, etc., that can be treated as analytical information. DCA gives us a more informative analytical method than spectrophotometry by treating colors as digital information. In addition, DCA can also simulate the optimum color variations for optimization of the visual sensor with computer assistance. By utilizing colors as digital information, colorimetric analysis that has been used for only semiquantitative analysis can serve as an accurate determination method. On the basis of DCA, we developed a plasticized PVC film optode and a paper optode for Li+ determination in saliva. After the optimization of color variation and the detection range for the Li+ measurements, the optode membrane gives colorless gray in the Li+ therapeutic range (at 10(-3) M) in saliva. Consequently, whether or not the optimum therapeutic Li+ concentration is maintained can be easily evaluated with these optodes. Especially, the sensing paper optode can be easily handled within a short measurement time (approximately 80 s) which is suitable for home use. Using the digital color analyzer with QxQy coordinates, a linear relation calibration curve can be obtained over the range from 10(-5) to 10(-1) M Li+, in which the analyzer can detect a concentration difference of approximately 0.1 mM Li+. For the near future, an accurate and simple analysis is needed for a health check at home that does not require going to a hospital. The optode based on DCA has great potential for this analytical purpose.