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The crystal and molecular structure of the hydrated form of (l-*-3)-|3-D-glucan of native curdlan and paramylon has been determined by combined X-ray diffraction and stereochemical model refinement, using data from X-ray fiber diagrams of curdlan and powder diagrams of paramylon. The structure crystallizes as a triplex of right-handed, sixfold helical chains in a hexagonal unit cell with parameters a = b = 15.56 ± 0.05 A and c (fiber repeat) = 18.78 ± 0.05 A. The probable space group is PI, but the three strands of the triplex are close to P3 symmetry. The structure shows evidence of disorder, in that all 18 hydroxymethyl groups of the triplex are in nonequivalent rotational positions, and the locations of water molecules are at least partly random. Of the 36 water molecules present in the unit cell, half appear to be clustered near the 0(4) and 0(5) atoms of the glucose residues, with about one water for every residue. The other half of the water molecules appear to be distributed in a statistical manner. The conformational characteristics of the chains are very similar to those of the anhydrous form of the structure. The reliability of the structure analysis is indicated by the X-ray residual R = 0.165. and, if so, whether the two triplexes were similar. The present study was, consequently, undertaken to determine the structure of the hydrated form. As before, X-ray diffraction analysis aided by stereochemical model refinement was used,2 with diffraction data obtained from both fiber diagrams of curdlan and powder patterns of paramylon. Experimental SectionThe curdlan was obtained from Takeda Chemical Co., Japan, and the paramylon granules were extracted from depigmented Euglena gracilis and were gifts from Dr. B. A.

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A novel method combining wet chemistry for synthesis of an Fe core, 532 nm laser irradiation of Fe nanoparticles and Au powder in liquid medium for deposition of an Au shell, and sequential magnetic extraction/ acid washing for purification has been developed to fabricate oxidation-resistant Fe@Au magnetic coreshell nanoparticles. The nanoparticles have been extensively characterized at various stages during and up to several months after completion of the synthesis by a suite of electron microscopy techniques (HRTEM, HAADF STEM, EDX), X-ray diffraction (XRD), UV-vis spectroscopy, inductively coupled plasma atomic emission spectroscopy, and magnetometry. The surface plasmon resonance of the Fe@Au nanoparticles is red shifted and much broadened as compared with that of pure colloidal nano-gold, which is explained to be predominantly a shell-thickness effect. The Au shell consists of partially fused ∼3-nm-diameter fcc Au nanoparticles (lattice interplanar distance, d ) 2.36 Å). The 18-nm-diameter magnetic core is bcc Fe single domain (d ) 2.03 Å). The nanoparticles are superparamagnetic at room temperature (300 K) with a blocking temperature, T b , of ≈170 K. After 4 months of shelf storage in normal laboratory conditions, their mass magnetization per Fe content was measured to be 210 emu/g, ∼96% of the Fe bulk value.

In order to facilitate the adhesion of corneal epithelial cells to a poly dimethyl siloxane (PDMS) substrate ultimately for the development of a synthetic keratoprosthesis, PDMS surfaces were modified by covalent attachment of combinations of cell adhesion and synergistic peptides derived from laminin and fibronectin. Peptides studied included YIGSR and its synergistic peptide PDSGR from laminin and the fibronectin derived RGDS and PHSRN. Surfaces were modified with combinations of peptides determined by an experimental design. Peptide surface densities, measured using 125-I labeled tyrosine containing analogs, were on the order of pmol/cm2. Surface density varied as a linear function of peptide concentration in the reaction solution, and was different for the different peptides examined. The lowest surface density at all solution fractions was obtained with GYRGDS, while the highest density was consistently obtained with GYPDSGR. These results provide evidence that the surfaces were modified with multiple peptides. Water contact angles and XPS results provided additional evidence for differences in the chemical composition of the various surfaces. Significant differences in the adhesion of human corneal epithelial cells to the modified surfaces were noted. Statistical analysis of the experimental adhesion results suggested that solution concentration YIGSR, RGDS, and PHSRN as well as the interaction effect of YIGSR and PDSGR had a significant effect on cell interactions. Modification with multiple peptides resulted in greater adhesion than modification with single peptides only. Surface modification with a control peptide PPSRN in place of PHSRN resulted in a decrease in cell adhesion in virtually all cases. These results suggest that surface modification with appropriate combinations of cell adhesion peptides and synergistic peptides may result in improved cell surface interactions.

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Surface modifying macromolecules (SMM) were synthesized and blended into the casting solution of poly(ether sulfone). The solution was cast to films with thickness of 0.12 and 0.24 mm. The cast films were placed in an oven with forced air circulation for periods of 3, 5, 7, and 2000 min to remove the solvent, before being immersed into water at 4°C for gelation. The membranes so prepared were further dried and subjected to contact angle measurement and XPS (X-ray photoelectron spectroscopy) analysis. It was found that the contact angle increased as the solvent evaporation period increased. The increase in contact angle was faster when the membrane was thinner. According to the XPS analysis, after an initial time lag the surface fluorine content increased as the evaporation time increased and finally leveled off. The increase in surface fluorine content was also faster when the membrane was thinner. A kinetic model was established for the SMM surface migration.