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Poly(ether ether ketone) (PEEK) possesses attractive mechanical and thermal properties but demonstrates poor adhesion. To overcome this disadvantage, in this study, the surface modification of PEEK or PEEK-based carbon-fiber-reinforced thermoplastics (CFRTP) was performed through the Friedel-Crafts reaction and successive epoxidation. Under optimized reaction conditions, surface modification was achieved without surface deterioration, and epoxy groups were introduced. The progress of the Friedel-Crafts reaction and epoxidation was demonstrated by X-ray photoelectron spectroscopy measurements after fluorine labeling through thiol-en reaction and amine addition, respectively. The adhesive strength between CFRTP and epoxy adhesives was increased to 23.5 MPa, and cohesive fracture of epoxy adhesives, rather than interfacial peeling, occurred. In addition, compared with conventional plasma treatment, the durability of the modified surface and thickness of the modified surface layer increased. Therefore, we succeeded in modifying the surface properties through the epoxidation of the PEEK surface.

We prepared microwave-responsive “on-demand-peeling” adhesives simply by mixing second-generation acrylic adhesives with ionic liquids. A rapid response (

Living tissues modules consist of highly organized cells and extracellular matrices (ECMs) in a hierarchical manner. Among these ECMs, type I collagen (COL), which is the most abundant protein, is widely accepted in the tissue engineering field due to its biocompatibility. However, improvement of mechanical properties of COL scaffolds still remains a challenge. We prepared the scaffold sheets with blends of COL and 2,2,6,6-tetramethylpiperidine-1-oxil(TEMPO)-oxidized cellulose nanofiber (TOCN). TOCNs with high mechanical properties reinforced COL scaffolds. Moreover, we prepared their blends under various pH conditions and investigated their mechanical properties and biocompatibilities. Sheets prepared at a higher pH possess a better mechanical performance. From Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy measurements, it is proved that the higher mechanical properties were attributed to COL triple inter helix structure, hydrogen interaction, and electrostatic interaction with TOCN. The biocompatibilities of COL/TOCN prepared at a higher pH were increased. We successfully demonstrated COL/TOCN blend materials with a high mechanical strength and high biocompatibility for scaffold materials.

Celluloses have attracted much attention as sustainable and abundant materials. Herein, we focus on nanocomposites based on the oxidation-treated nano-sized fibrillated celluloses, namely TOCNs. The silver nanoparticles (AgNPs) were prepared in TOCN aqueous dispersion. Generally, the AgNPs are quickly agglomerated after preparation. For the inhibition of the agglomeration of AgNPs, it is required that AgNPs were prepared under the chelation of TOCN, followed by reduction therein. Therefore, AgNPs possessed the nano-scaled radii and aligned along the TOCN from the atomic force microscopic measurements. The thermal stabilities and mechanical properties were increased. The anisotropic thermal conductivities originated from the orientation of TOCN in nanocomposites were observed. The loading of the large amounts of AgNP fillers led to the drastic increase of the thermal and electrical conductivities. The conductive paths of heat and electron were formed by the contact of AgNP with each other. We functionalized the TOCN papers through the loading of AgNPs and the obtained nanocomposites sheets served as conductors.

Primer treatments to improve the adhesive properties of isotactic polypropylene (it.PP) have advantages in terms of their simple process and reasonable costs. However, a large contribution to the optimization of the treatment condition is required because of many parameters for achieving high adhesion strength. In addition, the mechanisms of primer effects have not been explained completely. We investigated the primer effects of dimethyloctadecylamine on the it.PP surface from the viewpoint of structural and surface properties. The it.PP main chains in the thin film state were aligned in parallel to the substrates. After amine primer treatment, the dimethyloctadecylamine assembled on the it.PP layer within 5 h. The primer alignments enhanced adhesive strength between it.PP and cyanoacrylate adhesives. The surface free energy of it.PP and cyanoacrylate adhesives was also increased by primer treatment. The time dependence of primer effects on the adhesion strength and surface properties was clarified.

The modification of surface properties of isotactic polypropylene (it.PP) has attracted much attention in fundamental science and industrial applications. Primer treatment is a promising methods that is employed to overcome the poor adhesive property of it.PP. In this study, we examined the primer effect of the cobalt complexes, cobalt (II) acetylacetonate Co(acac)2 and cobalt (III) acetylacetonate Co(acac)3, from the perspectives of adhesive strength, curing process, surface structure, affinity between substrate and adhesive, morphology and interfacial thickness. The results obtained explain the increased adhesive strength between an isotactic polypropylene substrate and a cyanoacrylate adhesive. In particular, the interfacial regions were evaluated as “interphase” by nano-Raman scattering microscopy and transmission electron microscope-energy-dispersive X-ray spectroscopy. The region is expanded by applying Co(acac)2 primer as the adhesive strength increased. The Co(acac)2 primer caused the increased adhesive property with the enhancement of molecular interaction, chemical affinity, and mutual diffusion.

In Asian countries, only bamboo culms that are 3–5 years old are used especially as materials because of their toughness, pliability, and/or workability. In this study, we evaluated the mechanical properties of bamboo in correlation with age-dependent changes in the nanostructures of cell walls, such as microfibril angles (MFAs), crystallite sizes, and crystallinity. Current year and 1.5-, 3.5-, 4.5-, 6.5-, and 8.5-year-old Phyllostachys pubescens samples were used. Three-point bending tests and wide-angle X-ray scattering experiments were conducted. The specific bending of Young’s modulus and the specific bending strength of 3.5- and 4.5-year-old bamboo samples were greater than those of other ages. The MFAs decreased in 1.5-year-old bamboo, were constant until samples were 6.5-years old, and then increased slightly in 8.5-year-old bamboo. The widths of crystallites appeared to be constant for all ages, while the lengths of crystallites and crystallinity showed age-dependent differences only on the inner side. In this study, the MFA was negatively correlated with the toughness of bamboo culms. This result should be considered with other structural features at the tissue level; however, the age-related changes in MFA values appear to be important factors related to the mechanical properties of bamboo.

Elastic modulus of the crystalline regions (crystal modulus) of poly(glycolic acid) (PGA) in the directions parallel (El) and perpendicular (Et) to the chain axis was measured by X-ray diffraction. The El value of PGA was 104 GPa at room temperature. This relatively low El value suggests that the PGA skeleton is not fully extended as reported before but contracted. The Et value of PGA was obtained as 7 GPa, which resembles that (7 GPa) of poly(vinyl alcohol) based on intermolecular hydrogen bonds. This reveals strong intermolecular interactions act between PGA molecules in the crystal lattice. Both low El value and high Et value are considered to contribute to the extraordinarily high melting point (223 °C) of PGA among aliphatic polyesters. Temperature dependence (13–400 K) of both El and Et of PGA was also investigated. Abrupt changes around 200 K for both directions were considered to be caused by molecular motion in the crystalline regions of PGA.

Recently, the synthesis of P3HT with high head-to-tail regioregularity and the control of the molecular weight have been achieved. Herein, we evaluated the structure in thin films of various molecular weight P3HT (from M w = 13 k to 828 k) prepared under diverse conditions through X-ray diffraction measurements. Higher molecular weight P3HT had the increase of “Face-on” structure in the thin films. From the structure of thin films prepared under other conditions, the main attribution was the speeds of sedimentation and inhabitation of the crystallization. Moreover, at the surface, the P3HT thin films with high molecular weight ( M w = 828 k) emerged “Edge-on”-rich structure. With the larger distance from thin film surface, the structure gradually changed from “Edge-on” to “Face-on”. These fundamental results would lead the suggestion in fabrication and performance of organic electronic devices.

This study investigated the effect of pretreatment of ultrasonic irradiation on emulsion polymerization of styrene to propose a process intensification method which gives high conversion, high reaction rate, and high energy efficiency. The solution containing styrene monomer was irradiated by a horn mounted on the ultrasonic transducer with the diameter of 5 mm diameter and the frequency of 28 kHz before starting polymerization. The pretreatment of ultrasound irradiation as short as 1 min drastically improved monomer dispersion and increased reaction rate even under the agitation condition with low rotational speed of impeller. Furthermore, the ultrasonic pretreatment resulted in higher monomer concentration in polymer particles and produced larger polymer particles than conventional polymerization without ultrasonic pretreatment.

Cellulose nanofiber (CNF) materials have received much attention as sustainable “green” materials with high mechanical properties. Their application in oil absorption and enzymatic lipolysis makes them further attractive from the perspective of environmental issues including marine pollution preservation. Herein, we prepared CNF cryogels with various surface properties, evaluated their capacities as oil absorbents and applied them as lipase-lipolysis scaffolds. Their obtained cryogels consisted of various modified CNFs and their structure and properties were investigated. Moreover, lipase-supported CNF cryogels were prepared for enzymatic lipolysis. The cryogels of protonated TEMPO-oxidized CNF showed the highest absorption capacity for olive oil, while all the CNF cryogels possessed similar absorption abilities towards water. In enzymatic lipolysis with lipase, the TEMPO-oxidized CNF (TOCN-Na+) cryogel showed the highest specific activity. The specific activities of lipase in TOCN-Na+ cryogels remained unchanged after being stored at 40 °C for 3 days.

Four types of kenaf bast fibers were prepared via a combination of Wise treatments, for delignification, and alkaline treatments, for the removal of hemicellulose. Each type of kenaf bast fiber with different refining processes were nano fibrillated by grinding. Resulting, cellulose nanofiber (CNF) sheet was obtained from CNF by vacuum filtration (Scheme 1). The structures and properties of these CNF sheets then were investigated to determine how the CNF components had affected these properties. All of the CNFs from different refining processes were classified as a cellulose Iβ type by X-ray diffraction. However, the mechanical properties (Young’s modulus, tensile strength and toughness) of the CNF sheet with Wise treatment were higher than the properties of the other three CNF sheets. These results strongly suggested that alkaline treatment was unnecessary for the removal of hemicellulose, and that the application of the Wise treatment effectively imparted high mechanical properties to the cellulose microfiber. Open image in new window Scheme 1 Schematic roots for getting cellulose nanofiber from biomass with various treatments and fibrillation methods

Objectives We had previously discovered that the flexural and tensile strengths of human dentin were 2–2.4 times greater after being heated to 140 °C, and deduced that the generation of higher-density structures and therefore dehydration probably promoted the increased strength. Our test hypotheses were that intertubular dentin, which constitutes a major part of organic components, was selectively affected by heating, and such changes could happen without critical damages to the basic structure of dentin type I collagen. Methods Micro-mechanical changes of human dentin by heating at 140 °C were investigated by nano-indentation. Chemical changes in dentin collagen after heating were also investigated by X-ray diffraction study, a microscopic Fourier transform infrared (micro-FTIR) and a laser Raman spectroscopic analyses, and a cross-linking analysis by high-performance liquid chromatography. Results The results of nano-indentation showed that the micro-hardness of intertubular dentin increased after heating at 140 °C to 1.8 times more than unheated dentin; on the other hand, peritubular dentin was unchanged. Results of X-ray diffraction showed that the lateral packing of collagen molecules shrank from 13.6 ± 0.3 to 10.6 ± 0.1 A after heating, but the shrinkage reversed to the original after rehydration for seven days. After heating, no substantial chemical changes in the collagen molecules were detected in tests by micro-FTIR or Raman analyses, or by cross-linking analysis. Significance These results suggest that intertubular dentin, which contains most of the type I collagen, was selectively affected by heating at 140 °C without critical damage to its collagen.

A high performance and functional properties in pressure-sensitive adhesives (PSAs) are attractive in fundamental and industrial fields. To control the performance of PSAs, nanofillers have been loaded into them. In this study, we focused on composites of acrylic PSAs and nanodiamonds (NDs). The loaded NDs reinforced the mechanical properties and increased the performance of the PSAs. NDs in a PSA formed a network structure. In this study, we revealed that the acidic–basic state was a key factor in the control of the dispersion of the NDs. When a PSA emulsions and ND aqueous dispersion was mixed under basic conditions, the composites demonstrated higher PSA properties (tack, holding, and peeling strength). We investigated the effect of the ND loading on the PSA properties from the viewpoints of the nanostructure and acid–base interactions.

Cyclohexyl, adamantyl, and triphenylmethyl groups were employed for the nucleophilic substitution reaction with N-vinylacetamide (NVA), in order to investigate the bulky substituents effects on molecular structures in N-vinyl monomers. Although normal alkyl halides were known to produce N-substituted NVA, alkyl halides with secondary and tertiary carbons did not occur nucleophilic substitution reaction. On the contrary, triphenylmethyl group was introduced into β-position on NVA, accompanied with hydrogen transfer. The refined crystal structure of β-triphenylmethyl-N-vinylacetamide revealed intermolecular linear hydrogen bonds and aromatic bulky triphenylmethyl group supported the structure.

Structures of (Pro-Pro-Gly)4-Xaa-Yaa-Gly-(Pro-Pro-Gly)4 (ppg9-XYG) where (Xaa, Yaa) = (Pro, Hyp), (Hyp, Pro) or (Hyp, Hyp) were analyzed at high resolution using synchrotron radiation. Molecular and crystal structures of these peptides are very similar to those of the (Pro-Pro-Gly)9 peptide. The results obtained in this study, together with those obtained from related compounds, indicated the puckering propensity of the Hyp in the X position: (1) Hyp(X) residues involved in the Hyp(X):Pro(Y) stacking pairs prefer the down-puckering conformation, as in ppg9-OPG, and ppg9-OOG; (2) Hyp(X) residues involved in the Hyp(X):Hyp(Y) stacking pairs prefer the up-puckering conformation if there is no specific reason to adopt the down-puckering conformation. Water molecules in these peptide crystals are classified into two groups, the 1st and 2nd hydration waters. Water molecules in the 1st hydration group have direct hydrogen bonds with peptide oxygen atoms, whereas those in the 2nd hydration group do not. Compared with globular proteins, the number of water molecules in the 2nd hydration shell of the ppg9-XYG peptides is very large, likely due to the unique rod-like molecular structure of collagen model peptides. In the collagen helix, the amino acid residues in the X and Y positions must protrude outside of the triple helix, which forces even the hydrophobic side chains, such as Pro, to be exposed to the surrounding water molecules. Therefore, most of the waters in the 2nd hydration shell are covering hydrophobic Pro side chains by forming clathrate structures. © 2009 Wiley Periodicals, Inc. Biopolymers 91: 361–372, 2009. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com

Small-angle X-ray scattering (SAXS), circular dichroism (CD), and density measurements were made on eight samples of collagen model peptides consisting of glycine (Gly), proline (Pro), and 4-(R)-hydroxyproline (Hyp), i.e., (Gly-Hyp-Hyp) n , (Gly-Pro-Hyp) n , (Gly-Hyp-Pro) n , and (Gly-Pro-Pro) n (n = 5 and 9) in pure water and in phosphate buffered saline at a wide range of temperatures between 4 and 75 °C. A complete triple-helical structure was found only for (Gly-Hyp-Hyp) 9 and (Gly-Pro-Hyp) 9 at 15 °C by SAXS and CD, and (Gly-Pro-Pro) 9 had a partially formed triple helix at 4 °C. At 70 °C or higher temperatures, all peptides are dispersed as monomeric chains in these solvents and have essentially the same radii of gyration as the literature values for denatured proteins with the equivalent number of amino acid residues, suggesting that the conformational entropy for the single chain of the collagen model peptides is almost independent of the imino acid content. Furthermore, the partial specific volume v for (Gly-Hyp-Hyp) 9 around the transition temperature decreases more gradually with decreasing temperature than that for (Gly-Hyp-Hyp) 5 . On the contrary, the temperature dependence of v for (Gly-Pro-Hyp) n has the opposite tendency, indicating that the hydration number for the peptide (Gly-Pro-Hyp) 9 increases with formation of the triple helix whereas that for the peptide (Gly-Hyp-Hyp) 9 decreases. These results are consistent with the difference in the transition enthalpies reported previously [J. Biol. Chem. 2004, 279, 38072].

The expression of the phenylalanine ammonia-lyase gene (PAL ) was induced in anthocynanin-producing suspension-cultured carrot cells. In our previous study, we isolated two PAL genes, DcPAL3 and DcPAL4, from a carrot genomic library, the nucleotide sequences of which are highly similar. Here, the complete nucleotide sequence of DcPAL4 was determined and compared with that of DcPAL3, revealing two miniature inverted repeat transposable elements (MITEs), here designated MITE1 and MITE2, inserted into the proximal promoter region of DcPAL3, but not into that of DcPAL4. The expression of DcPAL4 was not detectable by RT-PCR in cultured carrot cells or the tissues of carrot plants, whereas DcPAL3 expression was detected. Transient expression experiment in carrot protoplasts showed that the DcPAL4 promoter actively produces transcripts, as does the DcPAL3 promoter. To characterize the roles of MITE1 and MITE2 (MITE1/2) in the transgenes of stable transformants, they were inserted into a plant transformation vector containing the 35S-b-glucuronidase (GUS) reporter gene and selectable antibiotic-resistance marker genes, and then introduced into tobacco BY-2 cells using an Agrobacterium method. More regenerated calli carrying the MITE1/2 construct survived on medium containing kanamycin than calli lacking MITE1/2. Regenerated calli containing MITE1/2 were more numerous having stronger GUS activity than those without MITE1/2. These results suggest that MITE1/2 enhances the expression of adjacent transgenes introduced into stable transformants and possibly into the endogenous DcPAL3 gene.

Triple-helical structures of (Pro-Hyp-Gly)n (n = 10, 11) at 100 K and room temperature (RT) were analyzed at 1.26 A resolution by using synchrotron radiation data. Totals of 49 and 42 water molecules per seven triplets in an asymmetric unit were found for the structures at 100 K and RT, respectively. These water molecules were classified into two groups, those in the first and second hydration shells. Although there was no significant difference between water molecules in the first shell at 100 K and those at RT, a significant difference between those in the second shell was observed. That is, the number of water molecules at RT decreased to one half and the average distance from peptide chains at RT became longer by about 0.3 A. On the other hand, of seven triplets in an asymmetric unit, three proline residues at the X position at 100 K clearly showed an up-puckering conformation, as opposed to the recent propensity-based hypothesis for the stabilization and destabilization of triple-helical structures by proline hydroxylation. This puckering was attributed to the interaction between proline rings and the surrounding water molecules at 100 K, which is much weaker at RT, as shown by longer average distance from peptide chains.

Poly(3-hexylthiophene) (P3HT) is widely shown to have considerable advantages in photovoltaic cells, including excellent electrical performance, but its fragility remains a challenge for material applications and processing of stretchable devices. Herein, high-molecular-weight and highly regioregular poly(3-substituted thiophene) with disiloxane moieties in the side chains (P3SiT) is synthesized. An investigation of the molecular structure and physical properties of self-supported cast films of P3SiT reveals excellent flexible mechanical properties derived from the disiloxane groups in the side chains. The larger fracture strain reaches over 200% compared with that of poly(3-hexylthiophene) (14%). In addition, its Young's modulus (43 MPa) and low glass transition temperature (-10 °C) result in a typical elastic mechanical property. For the electrical property, the sheet resistivity of the drawn thiophene polymer shows the value almost equal to that of poly(3-hexylthiophene). The anisotropy of electrical resistivity is observed due to orientation of the drawn polymer.

The average crystal structure of a collagen-model peptide, (Pro-Pro-Gly)9 has been determined at 1.0A resolution. Crystals belong to an orthorhombic system (P212121) with cell parameters of a=26.82(2), b=26.33(2), and c=20.25(2)A. The X-Ray oscillation photograph clearly showed satellite spots with an 80 A axial repeat on both sides of the strong spots on the layer lines corresponding to c=20A. The existence of c=80A axial repeat suggests that the longer repeat along the c-axis is the shortest integral multiply of the helical repeat (20A) enough to accommodate one (Pro-Pro-Gly)9 molecule and an appropriate gap between adjacent molecules. According to the reflection data with c=20A axial repeat, the overall peptide structure is very close to the left-handed 7/2-helical model for collagen. Based on the difference Fourier map, 34 water molecules were added in the asymmetric unit of seven triplets. Of which 14 water molecules make hydrogen bonds with peptide chains and rest of them participate in hydrogen bonds only with other water molecules.

Collagen is the most abundant protein in mammals and is widely used as a biomaterial for tissue engineering and drug delivery. We previously reported that dendrimers and linear polymers, modified with collagen model peptides (Pro-Pro-Gly)₅, form a collagen-like triple-helical structure; however, its triple helicity needs improvement. In this study, a collagen-mimic dendrimer modified with the longer collagen model peptides, (Pro-Pro-Gly)₁₀, was synthesized and named PPG10-den. Circular dichroism analysis shows that the efficiency of the triple helix formation in PPG10-den was much improved over the original. The X-ray diffraction analysis suggests that the higher order structure was similar to the collagen triple helix. The thermal stability of the triple helix in PPG10-den was higher than in the PPG10 peptide itself and our previous collagen-mimic polymers using (Pro-Pro-Gly)₅. Interestingly, PPG10-den also assembled at low temperatures. Self-assembled structures with spherical and rod-like shapes were observed by transmission electron microscopy. Furthermore, a hydrogel of PPG10-den was successfully prepared which exhibited the sol-gel transition around 45°C. Therefore, the collagen-mimic dendrimer is a potential temperature-dependent biomaterial.

The solvent effects on the crystallization of porous isotactic (it) poly(methyl methacrylate) (PMMA) thin films as well as the incorporation behavior of syndiotactic (st) poly(methacrylic acid) (PMAA) into the porous films were investigated. The porous it-PMMA thin films were prepared by the extraction of st-PMAA from a stepwise layer-by-layer (LbL) assembly composed of it-PMMA and st-PMAA. The X-ray diffraction pattern of the it-PMMA thin films after immersion in acetonitrile/water (4/6, v/v) showed two characteristic peaks of a crystalline it-PMMA double-stranded helix (2theta = 9 degrees and 14 degrees , d = 0.96 and 0.62 nm). This suggested that acetonitrile promoted the crystallization of the thin films, because water is a nonsolvent for PMMA. The surface structural change of the it-PMMA films was also analyzed by atomic force microscopy. The it-PMMA conformation was maintained after crystallization as observed by infrared spectroscopy. The incorporation percentages of st-PMAA into the porous it-PMMA thin films under various solvent conditions were estimated using a quartz crystal microbalance. The incorporation of st-PMAA decreased as the it-PMMA films crystallized or with growing thickness of the porous it-PMMA films. This suggested that the polymer-polymer interactions and the entanglement of the it-PMMA chains played an important role. The incorporation was promoted as the acetonitrile content in the st-PMAA solution increased, indicating that it was necessary for st-PMAA incorporation to solvate it-PMMA.

The flexural strength of Type I collagen, the major organic component of human dentin, increases with heat. We hypothesized that human dentin can be strengthened by heating, which may help prevent fracture of non-vital teeth after restoration. Beam-shaped dentin specimens were obtained from the crowns of human third molars. The dentinal tubular orientations were arranged to run parallel or perpendicular to loading surfaces. The flexural and microtensile strengths of dentin in the parallel specimens were 2- to 2.4-fold greater after being heated between 110°C and 140°C for 1 hr. The stress intensity factors at fracture also increased after specimens were heated. The x-ray diffraction analyses suggested that shrinking of the lateral packing of the collagen triple-helices from 14 Å to 11 Å was the probable cause of the strengthening of heated dentin. We conclude that heat treatment strengthens human dentin.

Average helical twists were calculated by the method of Sugeta and Miyazawa (Biopolymers 1967, 5, 673-679) for all of the collagen model peptides analyzed to date. Calculation of the helical twists of all triplets in each peptide strand provided novel insights for several model peptides. In the (Pro-Pro-Gly)n (n = 9 and 10), the helical twists showed cyclic fluctuations between 40 and 65 degrees with a 20 A period, suggesting that their molecular conformations were close enough to the ideal 7/2-helix to show the helical repeat of 20 A. Rather small helical twists in the guest regions of IBP in complex and T3-785 were attributed to the interaction with Integrin I domain and a relaxed conformation caused by three consecutive triplets lacking imino acid residues, respectively. Although most of the triplets used in this study were imino acid-rich triplets, helical twists were scattered in a wide range from 30 to 70 degrees with an overall average of 52.6 degrees . This distribution of helical twists indicated a strong preference for the 7/2-helical conformation (51.4 degrees ) rather than the 10/3-helical model (36 degrees ).

The crystal structure of a collagen-model peptide [(Pro-Pro-Gly)(9)](3) has been determined at 1.33 A resolution. Diffraction data were collected at 100 K using synchrotron radiation, which led to the first structural study of [(Pro-Pro-Gly)(n)](3) under cryogenic conditions. The crystals belong to the P2(1) space group with cell parameters of a = 25.95, b = 26.56, c = 80.14 Angstroms and beta = 90.0 degrees. The overall molecular conformation was consistent with the left-handed 7/2-helical model with an axial repeat of 20 A for native collagen. A total of 332 water molecules were found in an asymmetric unit. Proline residues in adjacent triple-helices exhibited three types of hydrophobic interactions. Furthermore, three types of hydrogen-bonding networks mediated by water molecules were observed between adjacent triple-helices. These hydrophobic interactions and hydrogen-bonding networks occurred at intervals of 20 Angstroms along the c-axis based on the previous sub-cell structures [(Pro-Pro-Gly)(n)](3) (n = 9, 10), which were also seen in the full-cell structure of [(Pro-Pro-Gly)(10)](3). Five proline residues at the Y position in the X-Y-Gly triplet were found in a down-puckering conformation, this being inconsistent with the recently proposed propensity-based hypothesis. These proline residues were forced to adopt opposing puckering because of the prevailing hydrophobic interaction between triple-helices compared with the Pro:Pro stacking interaction within a triple-helix.

Triple-helical structures of (Pro-Hyp-Gly)n (n = 10, 11) at 100 K and room temperature (RT) were analyzed at 1.26 A resolution by using synchrotron radiation data. Totals of 49 and 42 water molecules per seven triplets in an asymmetric unit were found for the structures at 100 K and RT, respectively. These water molecules were classified into two groups, those in the first and second hydration shells. Although there was no significant difference between water molecules in the first shell at 100 K and those at RT, a significant difference between those in the second shell was observed. That is, the number of water molecules at RT decreased to one half and the average distance from peptide chains at RT became longer by about 0.3 A. On the other hand, of seven triplets in an asymmetric unit, three proline residues at the X position at 100 K clearly showed an up-puckering conformation, as opposed to the recent propensity-based hypothesis for the stabilization and destabilization of triple-helical structures by proline hydroxylation. This puckering was attributed to the interaction between proline rings and the surrounding water molecules at 100 K, which is much weaker at RT, as shown by longer average distance from peptide chains.

Using X-ray diffraction (XRD) analysis, the porous structure of isotactic (it-) poly(methyl methacrylate) (PMMA) thin films fabricated with layer-by-layer (LbL) assembly of it-PMMA and syndiotactic...

The original article to which this Erratum refers was published in Biopolymers (Peptide Science) (2004) 76(5) 367–377

Collagen hydrogels with oriented triple-helix were fabricated simply via the axial orientation of a dense collagen solution onto a glass plate and cross-linking. The orientation of the collagen tri...