Static and dynamic light scattering study of crystalline polymer films.

The light scattering from crystalline polymer films has been used to characterize crystalline superstructures such as spherulites, rods and disks which are usually found in crystalline polymer films prepared from melts and cast or molded from concentrated solutions. The scattering has been shown to arise principally from internal heterogeneities of both density and orientation of optic axes of scattering elements occuring in polymer films over distances comparable with the wavelength of the light. It is possible by analyzing and separating the heterogeneities to evaluate the size, shape and type of the superstructures as a whole as well as the internal perfection of such superstructures in terms of both density and orientation. However the separation of the density and orientation heterogeneities, and the separation of the internal heterogeneities occuring in such superstructures from the properties related to the superstructure as a whole are still not completely succesful at this moment

Quantitative Analyses of Small-Angle X-ray Scattering Profiles with a Linear Position Sensitive Detector

Quantitative data analyses of small-angle scattering (SAXS) profiles measured with a linear position sensitive detector (PSD) are discussed. We shall describe corrections of the measured SAXS profiles for (i) non-uniformity of the detector sensitivity along its length, (ii) collimation errors, and (iii) reduction of the position resolution due to the oblique incidence of photons to the detector. The correction of the profile for the collimation errors (i.e., desmearing) involves measurement of the slit weighting functions which depend on properties related to the PSD and its electronics (e.g., channel number or conversion gains of ADC and TAG, position resolution, and the uniformity of detector sensitivity) as well as the optical set-up of the SAXS apparatus. It is shown that properly corrected SAXS profiles obtained with the PSD quantitatively agree with those obtained with a conventional step-scan SAXS apparatus such as the Kratky U-slit system and the Beeman four slit system

Microphase Separation of Block Polymers

Block polymers composed of incompatible block chains of A and B undergo a microphase separation due to the repulsive interaction between A and B in solutions at concentrations above the critical concentration, or in bulk at temperatures below the critical temperature, Tc, (for the A-B system having an upper critical solution temperature) or above Tc (for the system having a lower critical temperature). The microphase separation results in a microdomain structure in solid state, the morphology of which controls the unique physical properties of the block polymer systems. This article reviews recent developments in the area of (i) microphase separation and phase-separated structure in solution and in bulk (ii) microdomain structure in solid state and (iii) polymer-polymer interphase in block polymers for amorphous and linear block polymer systems having simple architectures (e.g., polystyrene and polyisoprene or polystyrene and polybutadiene diblock or triblock polymers)

Time-resolved light scattering studies on kinetics of phase separation and phase dissolution of polymer blends. 1. Kinetics of phase separation of a binary mixture of polystyrene and poly(vinyl methyl ether

ABSTRACT The dynamics of liquid-liquid phase separation of a polymer blend of polystyrene and poly(viny1 methyl ether) was studied by time-resolved elastic light scattering techniques in both the nucleation-growth (NG) and spinodal-decomposition (SD) regimes. It was found that in the early stage of SD the scattered intensity a t a given momentum transfer q = (4r/X) sin (8/2) increases exponentially with time after the initiation of the isothermal phase separation involved by a temperature jump from the temperature well below the binodal point. The relaxation rate 2R(q) of the intensity increase is a function of q such that R(q)/q2 linearly decreases with q2, in accord with the linear theories of SD originally proposed by Cahn for small molecules and extended by de Gennes for polymers. The spinodal temperature was obtained from the dynamics measured as a function of temperature in the linear SD regime. In the later stage of SD, the intensity increase with time starts to deviate from exponential behavior and the scattering maximum shifts to smaller q, corresponding to the onset of the coarsening process. The higher the superheating, the earlier the stage where the coarsening starts. In the NG regime the intensity increases nonexponentially with time

Conformational Epitopes of Pemphigus Antigens (Dsg1 and Dsg3) Are Calcium Dependent and Glycosylation Independent

The target molecule of pemphigus autoantibodies is a transmembrane desmosomal component, desmoglein 3 (Dsg3) in pemphigus vulgaris (PV) and Dsg1 in pemphigus foliaceus (PF). In this study, we examined the effects of calcium and glycosylation on the antigenicity of the pemphigus antigens and on the generation of conformational epitopes. We used recombinant baculovirus proteins, PVIg and PFIg, which are considered to reflect accurately the native conformation of the extracellular domain of their respective proteins Dsg3 and Dsg1. These baculoproteins could immunoadsorb heterogeneous autoantibodies from the corresponding sera of PV and PF patients, completely blocking indirect immunofluorescence staining of normal human skin. Chelating calcium from the solution containing the baculoproteins using ethylenediaminetetraacetic acid (EDTA) or ethyleneglycol-bis(β-aminoethyl ether)-N,N,N', N'-tetraacetic acid (EGTA) abolished immunoadsorption by both PVIg and PFIg; however, immunoadsorption by the baculoproteins was restored after dialysis against 1 mM calcium. Nonglycosylated forms of both baculoproteins produced in the presence of tunicamycin retained their immunoadsorptive ability. Furthermore, immunoadsorption by the baculoproteins was prevented irreversibly by treatment with low pH, high pH, and boiling, but not with the non-ionic detergent Nonidet P-40. These findings indicate that formation of the conformational epitopes on the pemphigus antigens is dependent on calcium but independent of glycosylation, and provide direct evidence that calcium plays an important role in determining the antigenic properties of the pemphigus antigens

Desmoyokin/AHNAK Protein Localizes to the Non-Desmosomal Keratinocyte Cell Surface of Human Epidermis

Desmoykin, a high-molecular-weight protein of 680 kD with a 170-um-long dumbbell shape, was originally thought to be localized to the desmosomal attachment plaque and to work as a kind of stabilizer of desmosomes. Recently, desmoyokin was shown to be widely detected in many types of cells that do not possess desmosomes. The purpose of the present study was to elucidate the precise localization and possible function of desmoyokin in human epidermis. In 0.2-μm ultrathin crysections of human skin for immunofluorescence, anti-desmoyokin antibody showed a ladder-like staining pattern along the cell surface, whereas anti-desmocollin and anti-desmoplakin antibodies as controls showed a discontinuous dotted staining pattern, indicating their distinct localization. Post-embedding immunoelectron microscopy with cryfixation and crysubstitution revealed that desmoyokin was localized manily along the non-desmosomal and non-hemidesmosomal plasma membrance, but not to the desmosomes and hemidesmosomes themselves. This localization was further confirmed by double-labeling immunoelectron microscopy with antibodies against desmocollin, desmoplakin, or bullous pemphigold antigen. Results indicate that desmoyokin was not localized to the desmosomes themselves as previously considered. Desmoyokin was localized to the non-desmosomal and non-hemidesomosomal epidermal keratinocyte cell surface as a plasma membrane-associated protein, and might play a role in cell adhesion that is not directly associated with desmosomes or hemidesmosomes