Mechanism underlying specificity of proteins targeting inorganic materials

Adhesion force analysis using atomic force microscopy clearly revealed for the first time the mechanism underlying the specific binding between a titanium surface and ferritin possessing the sequence of Ti-binding peptide in its N-terminal domain. Our results proved that the specific binding is due to double electrostatic bonds between charged residue and surface groups of the substrate. Furthermore, it is also demonstrated that the accretion of surfactant reduces nonspecific interactions, dramatically enhancing the selectivity and specificity of Ti-binding peptide.     

Application of a quick-freezing and deep-etching method to pathological diagnosis: a case of elastofibroma

A case of elastofibroma in a middle-aged Japanese woman was examined by the quick-freezing and deep-etching (QF-DE) method, as well as by immunohistochemistry and conventional electron microscopy. The slowly growing tumor developed at the right scapular region and was composed of fibrous connective tissue with unique elastic materials called elastofibroma fibers. A normal elastic fiber consists of a central core and peripheral zone, in which the latter has small aggregates of 10 nm microfibrils. By the QF-DE method, globular structures consisting of numerous fibrils (5-20 nm in width) were observed between the collagen bundles. We could confirm that they were microfibril-rich peripheral zones of elastofibroma fibers by comparing the replica membrane and conventional electron microscopy. One of the characteristics of elastofibroma fibers is that they are assumed to contain numerous microfibrils. Immunohistochemically, spindle tumor cells showed positive immunoreaction for vimentin, whereas alpha-smooth muscle actin, desmin, S-100 protein and CD34 showed negative immunoreaction. By conventional electron microscopy, the tumor cell had thin cytoplasmic processes, pinocytotic vesicles and prominent rough endoplasmic reticulum. Abundant intracytoplasmic filaments were observed in some tumor cells. Thick lamina-like structures along with their inner nuclear membrane were often observed in the tumor cell nuclei. The whole image of the tumor cell was considered to be a periosteal-derived cell, which would produce numerous microfibrils in the peripheral zone of elastofibroma fibers. This study indicated that the QF-DE method could be applied to the pathological diagnosis and analysis of pathomechanism, even for surgical specimens obtained from a patient.     

Numerical simulation of natural ventilation of a factory roof cavity

The study targets the reduction of roof solar heat gain through the use of natural ventilation in a cavity of a factory roof. In the laboratory experiment [1], the average air velocity reached 0.25 m/s. A simulation program was developed to calculate the heat and air flow attained in the experiment. An airflow passage was divided into sections to trace the pattern of the air temperature rise. When the cavity was divided into 20 sections, it was enough to trace the temperature rise pattern, and hence to calculate buoyancy for natural ventilation. Then the simulated air velocities, temperatures and heat transportations were compared with the experimental results. The molecular viscosity and thermal conductivity of the air were modified to adjust the simulation results to the experimental results in a wide range of experimental conditions. When they were multiplied with a magnitude of 30 equally, the least root mean square of the ratio of deviations of the heat transportation was obtained. This simulation could predict the heat transportation as a result of natural ventilation with a root mean square of the deviation of 0.25 in a short calculation time.     

Single-walled carbon nanotube growth with non-iron-group “catalysts” by chemical vapor deposition

Various materials have been found to “catalyze” carbon nanotube growth in chemical vapor deposition (CVD) when they become nano-sized particles. These involve not only metals, such as Pd, Pt, Au, Ag, and Cu, but also semiconductors, such as Si, Ge, and SiC. Alumina and diamond nanoparticles also produce carbon nanotubes. These “catalysts”, which are better called “seeds”, can be categorized into two types: one type forms a eutectic liquid or highly-mobile alloy with carbon, and carbon atoms precipitate from the eutectic alloy; the other type remains as a solid phase and form a carbon surface layer during CVD growth. In this paper, we review recent studies of SWCNT growth with these non-iron-group materials and highlight the mechanisms involved.      

Design and characterization of nanoknife with buffering beam for in situ single-cell cutting

A novel nanoknife with a buffering beam is proposed for single-cell cutting. The nanoknife was fabricated from a commercial atomic force microscopy (AFM) cantilever by focused-ion-beam (FIB) etching technique. The material identification of the nanoknife was determined using the energy dispersion spectrometry (EDS) method. It demonstrated that the gallium ion pollution of the nanoknife can be ignored during the etching processes. The buffering beam was used to measure the cutting force based on its deformation. The spring constant of the beam was calibrated based on a referenced cantilever by using a nanomanipulation approach. The tip of the nanoknife was designed with a small edge angle 5° to reduce the compression to the cell during the cutting procedure. For comparison, two other nanoknives with different edge angles, i.e. 25° and 45°, were also prepared. An in situ single-cell cutting experiment was performed using these three nanoknives inside an environmental scanning electron microscope (ESEM). The cutting force and the sample slice angle for each nanoknife were evaluated. It showed the compression to the cell can be reduced when using the nanoknife with a small edge angle 5°. Consequently, the nanoknife was capable for in situ single-cell cutting tasks.