Effect of glycerin on structure transition of PVA/SF blends

Blend films of silk fibrion (SF) and poly(vinyl alcohol) (PVA), with glycerin as an additive, were made, and the structure and properties of the blends were investigated by scanning electron microscopy (SEM), Fourier transform infrared (FT‐IR) spectroscopy, differential scanning calorimetry (DSC), and wide‐angle X‐ray diffraction (WAXD) and with an Instron Material Tester. The results showed that SF and PVA are principally incompatible and the blends made by the two polymers were phase‐separated. The results, however, also demonstrated that the blend structure could be changed to some extent by addition of 3–8% glycerin. The boundary of the PVA and SF phases became indistinct, as reported by SEM, a new peak appeared in the WAXD curves, the width of the OH absorption peak in the FT‐IR spectra increased, and the melting points changed in the DSC curves. In particular, the mechanical properties obviously increased, from 350 kg/cm² and 10% of PVA/SF (80/20) film to 832 kg/cm² and 39% of PVA/SF (80/20) film because of the increase in glycerin. It was suggested that glycerin plays a role in building the relationship between PVA and SF, strengthening the interaction between them and improving their compatibility. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2342–2347, 2002     

Relations between the molecular aggregation state and ionic conductivity in photopolymerized crosslinking polymers with oligo(oxyethylene) chains

A mixture of a vinyl monomer and a crosslinking agent was photopolymerized to form a crosslinked polymer film. Methacrylate with pendant oligo(oxyethylene) chain and poly(ethylene glycol) dimethacrylate were used as the vinyl monomer and crosslinking agent, respectively. The ionic conductivity of the film increased with an increasing concentration of LiClO₄ and then decreased. The size of the quasicrystalline aggregation phase composed of pendant and crosslinking chains in the film decreased with an increasing concentration of LiClO₄. The amorphous pendant and crosslinking oxyethylene chains gave rise to increased segmental motion and conductivity. The dissolution was depressed for a decrease in the ionic conductivity at a high LiClO₄ concentration at which the interactions among ions became stronger and the crystal phase of LiClO₄ was formed. The amount of the dissolution of the aggregation phase increased with an increasing crosslinking agent concentration. The quasicrystalline aggregation phase became larger with an increasing length of the pendant chains, and an increase in the size of the aggregation phase resulted in a decrease in the ionic conductivity. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1272–1277, 2002     

Amplifying shear deformation of finger pad increases tracing distances

Human sensory inputs and motor outputs mutually affect one another. We pursue the idea that a tactile interface can influence human motor outputs by intervening in sensory–motor relationships. This study focuses on the shear deformation of a finger pad while a person traces a line or circle. During these tracing movements, the finger pads were deformed using a tactile interface. The tracing distances increased when the finger pad deformations were amplified by the tactile interface, which indicates that the intervention in the haptic sensorimotor loop affected the tracing movements. Elucidation of such interaction between the tracing movements and the shear deformations of finger pads enhances the understanding of human-assistive haptic techniques.     

Point mutation of alanine (31) to valine prohibits the folding of reduced lysozyme by sulfhydryl--disulfide interchange

In the preceding paper in this issue, we described the overproduction of one mutant chicken lysozyme in Escherichia coil.Since this lysozyme contained two amino acid substitutions (Ala³¹ValandAsn¹⁰⁶Ser)in addition to an extra methionine residue at theNH₂-terminus the substituted amino acid residues were convertedback to the original ones by means of oligonucleotide-directedsite-specific mutagenesis and in vitro recombination. Thus fourkinds of chicken lysozyme [Met^–1 Val³¹Ser¹⁰⁶-, Met^–1Ser¹⁰⁶-,Met^–1 Val³¹-and Met^–1 (wild type)] wereexpressed in E. coli. From the results of folding experimentsof the reduced lysozymes by sulfhydryl-disulfide interchangeat pH 8.0 and 38°C, follow ed by the specific activity measurementsof the folded en zymes, the following conclusions can be drawn:(i) an extra methionine residue at the NH₂-terminus reducesthe folding rate but does not affect the lysozyme activity ofthe folded enzyme; (ii) the substitution of Asn¹⁰⁶ by Ser decreasesthe activity to 58% of that of intact native lysozyme withoutchanging the folding rate; and (iii) the substitution of Ala³¹Val prohibits the correct folding of lysozyme. Since the wildtype enzyme (Met^–1-lysozyme) was activated in vitro withoutloss of specific activity, the systems described in this study(mutagenesis, overproduction, purification and folding of inactivemutant lysozymes) may be useful in the study of folding pathways,expression of biological activity and stability of lysozyme.     

Structure--activity relationships in human interleukin-1{alpha}: identification of key residues for expression of biological activities

To identify the sites important for the different biologicalactivities of human interleukin-l (hIL-1), 56 single-amino acid-substitutedmutants of hIL-l were produced in Escherichia coli using site-directedmutagenesis, and were examined for their biological activitiessuch as mouse lymphocyte activating factor activity (LAF activity),cytostatic activity against human melanoma cells A-375 (A375activity) and prostaglandin E2 (PGE2) inducing activity in humanosteosarcoma cells MG-63 (PEI activity). Two amino acid residues,Asp26 and Asp151, were found to be important for these activities.The replacement of Asp26 by Val caused a decrease in LAF andA375 activities by one or two orders of magnitude and a slightdecrease in A375 activity. The Tyr or Phe substitution for Asp151caused decreases in LAF and A375 activities by one or two ordersof magnitude and complete loss of PEI activity. The change fromAsp151 to Lys or Arg resulted in marked decrease in LAF activityand complete loss of A375 and PEI activities. Since Asp26 andAsp151 are close to each other in the three-dimensional structure,the region involving these amino acids seems to be importantfor the biological activities of hIL-1.     

Masking effect of photoactive compounds with various ballast molecules in novolak-naphthoquinonediazide positive photoresists

We investigated the masking effect, that is, the dissolution inhibition effect, of photoactive compounds (PAC) with various ballast moelcules in novolak-naphthoquinonediazide positive photoresists. Two types of ballast molecules were examined: hydroxybenzophenones (HBP) and several m-cresol novolak resins (MCN) of different molecular lengths. The number of naphthoquinonediazide sulfonic (NQDS) moieties in the resist film and the average esterification value of the PACs were the same for each type of ballast molecule. The smaller the size of the HBP ballast molecule, the larger the masking effect becomes. As the size of the ballast molecule becomes smaller, the number of PACs increases and the degree of dispersion of the NQDS moieties in the resist film increases. At the same time, the longer the MCN ballast molecule, the larger the masking effect becomes. The distance between the NQDS moieties in the MCN ballast molecule is greater than that in the HBP ballast molecule. The masking effect per NQDS moiety in the MCN ballast molecule is larger than that in the HBP ballast molecule. As a result, the distance between the NQDS moieties in the ballast molecule and the degree of dispersion of the NQDS moieties in the resist film control the masking effect, which depends on the probability of existence of NQDS moieties around the alkali-soluble hydroxyl groups of the novolak resin. The molecular length of the ballast molecule influences the degree of entanglement with the novolak resins and promotes the masking effect.     

Enzyme electrode based on gold-plated polyester cloth

Summary Diaphorase is immobilized on electrodes derived from metal-plated polyester cloth by entrapment method and coupled with an electron mediator. Cyclic voltammogram depended on the existence of the substrate NADH (for oxidation) or NAD⁺ (for reduction) and the flavo-enzyme was shown to exchange electron(s) with the cloth electrode by mediation of the ferrocene derivative (for oxidation cycle) or the viologen derivative (for reduction cycle), even in the immobilized state. Coupling of the NADH or NAD⁺ regenerating system with alcohol dehydrogenase was examined.     

Growth modulation of human tumor cells by a growth-inhibiting activity derived from tumorigenic V79 Chinese hamster cells

A growth-inhibiting activity was identified in supernatants of the neoplastic V79 Chinese hamster cell line based on its ability to inhibit the proliferation of the same cell line. The partially purified activity, provisionally termed "growth inhibiting factor" (GIF) activity, inhibited the growth of a wide variety of human tumor cells, but not various normal human fibroblasts. This species-nonspecific activity was reversible, saturable, and highly potent in tumorigenic cell lines, and was noted in both monolayer culture and in soft agar. The inhibitory activity of GIF was also exhibited in a chemically defined serum-free medium supplemented with insulin and transferrin. GIF activity was stable to acid, heat, trypsin, and dithiothreitol but sensitive to alpha-chymotrypsin. The pattern of growth modulation by GIF on V79 cells was apparently different from those exhibited by bifunctional peptides such as transforming growth factor-beta, tumor necrosis factor-alpha, and interleukin-1-alpha. In addition, GIF activity cannot be ascribed to these cytokines based on the physicochemical and immunologic properties. Although GIF has yet to be purified to homogeneity, these data suggest that GIF might be a novel growth regulator which has a critical role in regulating growth of V79 cells. The growth modulation of tumor cells by this tumor-derived growth inhibiting activity suggested the presence of an autocrine growth regulatory mechanism even in tumor cells.     

How Does the Agents' Appearance Affect Users' Interpretation of the Agents' Attitudes: Experimental Investigation on Expressing the Same Artificial Sounds From Agents With Different Appearances

An experimental investigation into how the appearance of an agent such as a robot or PC affects people's interpretations of the agent's attitudes is presented. In general, people are said to create stereotypical agent behavioral models in their minds based on the agents' appearances, and these appearances significantly affect their way of interaction. Therefore, it is quite important to address with the following research question: How does an agent's appearance affect its interactions with people? Specifically, a preliminary experiment was conducted to select eight artificial sounds for which people can estimate two specific primitive attitudes (e.g., positive or negative). Then an experiment was conducted where the participants were presented with the selected artificial sounds through three kinds of agents: a MindStorms robot, AIBO robot, and laptop PC. In particular, the participants were asked to select the correct attitudes based on the sounds expressed by these three agents. The results showed that the participants had better interpretation rates when a PC presented the sounds and lower rates when the MindStorms and AIBO robots presented the sounds, even though the sounds expressed by these agents were the same. The results of this study contribute to the design policy of the interactive agents, such as, What types of appearances should agents have to effectively interact with people, and which kinds of information should these agents express to people?