The morphology of decorated amyloid fibers is controlled by the conformation and position of the displayed protein.

Self-assembled structures capable of mediating electron transfer are an attractive scientific and technological goal. Therefore, systematic variants of SH3-Cytochrome b(562) fusion proteins were designed to make amyloid fibers displaying heme-b(562) electron transfer complexes. TEM and AFM data show that fiber morphology responds systematically to placement of b(562) within the fusion proteins. UV-vis spectroscopy shows that, for the fusion proteins under test, only half the fiber-borne b(562) binds heme with high affinity. Cofactor binding also improves the AFM imaging properties and changes the fiber morphology through changes in cytochrome conformation. Systematic observations and measurements of fiber geometry suggest that longitudinal registry of subfilaments within the fiber, mediated by the interaction and conformation of the displayed proteins and their interaction with surfaces, gives rise to the observed morphologies, including defects and kinks. Of most interest is the role of small molecule modulation of fiber structure and mechanical stability. A minimum complexity model is proposed to capture and explain the fiber morphology in the light of these results. Understanding the complex interplay between these factors will enable a fiber design that supports longitudinal electron transfer.

Progress in ultra-high modulation efficiency tapered lasers for free-space communications

Simultaneous high power (2W), high modulation speed (1Gb/s) and high modulation efficiency (14 W/A) operation of a two-electrode tapered laser is reported. © 2011 IEEE.

COMPARISON OF MASTICATORY MORPHOLOGY BETWEEN RHINOPITHECUS-BIETI AND R-ROXELLANA

The masticatory apparatus for two endemic species of golden monkey in China, Rhinopithecus bieti and Rhinopithecus roxellana, were compared with those of macaques, Macaca and leaf monkeys, Presbytis. Multivariate analyses demonstrated that the two golden monkey species are distinct. Interspecies allometric analyses revealed that golden monkeys differ in their masticatory apparatus from both macaques and leaf monkeys. The prominent symphysial fusion, corpus, and sagittal condylar dimension of R. roxellana may produce efficient biting force on the incisal and posterior canine teeth, with the heavy reaction force barn on the temporomandibular joint. However, the well-developed bizygamatic width and mandibular height in R. bieti suggest that posterior canine function is similarly prominent in R. roxellana, while incisal function is not. (C) 1995 Wiley-Liss, Inc.

Ultra-structural defects cause low bone matrix stiffness despite high mineralization in osteogenesis imperfecta mice.

Bone is a complex material with a hierarchical multi-scale organization from the molecule to the organ scale. The genetic bone disease, osteogenesis imperfecta, is primarily caused by mutations in the collagen type I genes, resulting in bone fragility. Because the basis of the disease is molecular with ramifications at the whole bone level, it provides a platform for investigating the relationship between structure, composition, and mechanics throughout the hierarchy. Prior studies have individually shown that OI leads to: 1. increased bone mineralization, 2. decreased elastic modulus, and 3. smaller apatite crystal size. However, these have not been studied together and the mechanism for how mineral structure influences tissue mechanics has not been identified. This lack of understanding inhibits the development of more accurate models and therapies. To address this research gap, we used a mouse model of the disease (oim) to measure these outcomes together in order to propose an underlying mechanism for the changes in properties. Our main finding was that despite increased mineralization, oim bones have lower stiffness that may result from the poorly organized mineral matrix with significantly smaller, highly packed and disoriented apatite crystals. Using a composite framework, we interpret the lower oim bone matrix elasticity observed as the result of a change in the aspect ratio of apatite crystals and a disruption of the crystal connectivity.

Tailoring the morphology of carbon nanotube assemblies using microgradients in the catalyst thickness

In addition to the structural control of individual carbon nanotubes (CNTs), the morphological control of their assemblies is crucial to realize miniaturized CNT devices. Microgradients in the thickness of catalyst are used to enrich the variety of available self-organized morphologies of CNTs. Microtrenches were fabricated in gate/spacer/cathode trilayers using a conventional self-aligned top-down process and catalyst exhibiting a microgradient in its thickness was formed on the cathode by sputter deposition through gate slits. CNTs, including single-walled CNTs, of up to 1μm in length were grown within 5-15 s by chemical vapor deposition. The tendency of thin CNTs to aggregate caused interactions between CNTs with different growth rates, yielding various morphologies dependent on the thickness of the catalyst. The field emission properties of several types of CNT assemblies were evaluated. The ability to produce CNTs with tailored morphologies by engineering the spatial distribution of catalysts will enhance their performance in devices. © 2011 The Japan Society of Applied Physics.