Role of Skin Layers on Mechanical Properties and Supercontraction of Spider Dragline Silk Fiber

Spider dragline silk is a composite biopolymer that harbors extraordinary mechanical characteristics, and consists of a hierarchically arranged protein core surrounded by outer “skin” layers. However, the contribution of the successive fiber layers on material properties has not been well defined. Here, the influence of the different components on the physicochemical and mechanical properties of dragline is investigated. The crystal structure and the mechanical properties are not changed significantly after the removal of skin constituents, indicating that the core region of dragline silk fibers determines the structural and mechanical properties. Furthermore, the outer layers have little influence on supercontraction, suggesting they do not function as protection against the penetration of water molecules. On the other hand, the outer layers offer some protection against protease digestion. The present study provides insight into how the function and structure of silk fibers are modulated and facilitates the design of silk‐inspired functional materials.     

Multiscale evaluation method of the drag effect on shallow water flow through coastal forests based on 3D numerical simulations

This study presents a method for determining the drag parameter in the 2D shallow water (SW) equation for flows through a coastal forest by conducting a series of 3D numerical simulations (3D NSs). Following the theory of multiscale modeling, an evaluation method procedure is proposed. We first prepare a local test domain that contains a sufficient number of trees to constitute part of a coastal forest. Then, 3D NSs are conducted in this test domain with various inflow conditions. Based on the corresponding results, the momentum losses over the test domain are converted into the drag parameter of the global SW equation. A response surface of the drag parameter is constructed as a function of the flow conditions. The stabilized finite element method is employed for both the local and the global NSs, and the phase-field method is utilized to represent 3D free surfaces. Comparisons between the 2D SW calculation results and the 3D NS results are also performed to verify the validity of the proposed method.     

Development of Luciferin Analogues Bearing an Amino Group and Their Application as BRET Donors

We systematically synthesized bioluminogenic substrates bearing an amino group on benzothiazole, quinoline, naphthalene, and coumarin scaffolds. They emit bioluminescence in various colors: red, orange, yellow, and green. An amino‐substituted coumarylluciferin derivative, coumarylaminoluciferin (CAL), showed the shortest bioluminescence wavelength among substrates reported so far. Further, the fluorescence of CAL did not exhibit solvatochromism, which suggests that its bioluminescence is not susceptible to environmental factors. We applied CAL as an energy‐donor substrate for a bioluminescence resonance energy transfer (BRET) system with click beetle red luciferase (CBRluc), a mutant of firefly luciferase, as the energy‐donor enzyme and yellow fluorescent protein (YFP) as the energy‐acceptor fluorophore, and obtained a clearly bimodal bioluminescence spectrum. Stable bioluminescence that is not influenced by environmental factors is highly desirable for reliable measurements in biological assays.     

The detection limit of a Gd3+-based T1 agent is substantially reduced when targeted to a protein microdomain

Simple low molecular weight (MW) chelates of Gd(3+) such as those currently used in clinical MRI are considered too insensitive for most molecular imaging applications. Here, we evaluated the detection limit (DL) of a molecularly targeted low MW Gd(3+)-based T(1) agent in a model where the receptor concentration was precisely known. The data demonstrate that receptors clustered together to form a microdomain of high local concentration can be imaged successfully even when the bulk concentration of the receptor is quite low. A GdDO3A-peptide identified by phage display to target the anti-FLAG antibody was synthesized, purified and characterized. T(1-)weighted MR images were compared with the agent bound to antibody in bulk solution and with the agent bound to the antibody localized on agarose beads. Fluorescence competition binding assays show that the agent has a high binding affinity (K(D)=150 nM) for the antibody, while the fully bound relaxivity of the GdDO3A-peptide/anti-FLAG antibody in solution was a relatively modest 17 mM(-1) s(-1). The agent/antibody complex was MR silent at concentrations below approximately 9 microM but was detectable down to 4 microM bulk concentrations when presented to antibody clustered together on the surface of agarose beads. These results provided an estimate of the DLs for other T(1)-based agents with higher fully bound relaxivities or multimeric structures bound to clustered receptor molecules. The results demonstrate that the sensitivity of molecularly targeted contrast agents depends on the local microdomain concentration of the target protein and the molecular relaxivity of the bound complex. A model is presented, which predicts that for a molecularly targeted agent consisting of a single Gd(3+) complex with bound relaxivity of 100 mM(-1) s(-1) or, more reasonably, four tethered Gd(3+) complexes each having a bound relaxivity of 25 mM(-1) s(-1), the DL of a protein microdomain is approximately 690 nM at 9.4 T. These experimental and extrapolated DLs are both well below current literature estimates and suggests that detection of low MW molecularly targeted T(1) agents is not an unrealistic goal.     

Origin of the enhanced copper spin echo decay rate in the pseudogap regime of the multilayer high-T(c) cuprates

We report measurements of the anisotropy of the spin echo decay for the inner layer Cu site of the triple layer cuprate Hg(0.8)Re(0.2)Ba(2)Ca(2)Cu(3)O(8) (T(c)=126 K). The angular dependence of the second moment (T(-2)(2M) identical with ) deduced from the decay curves indicates that T(-2)(2M) for H0 parallel c is enhanced in the pseudogap regime below T(pg) approximately 170 K, as seen in bilayer systems. Comparison of T(-2)(2M) between H0 parallel c and H0 perpendicular c indicates that this enhancement is caused by electron spin correlations between the inner and the outer CuO2 layers. The results provide the answer to the long-standing controversy regarding the opposite T dependences of (T1T)(-1) and T(-2)(2G) (T(2G): Gaussian component) in the pseudogap regime of multilayer systems.     

Anomalous scattering from dielectric bispheres in the specular direction

Resonant scattering from dielectric bispheres in the specular direction (the so-called specular resonance), previously known only in the microwave range, has been observed at the optical wavelength. Systematic experiments with micrometer-sized dielectric bispheres assembled by micromanipulation, together with rigorous numerical calculations, reveal that this scattering is a precursor of the classical rainbow and is a general phenomenon observed in the wide range of size parameters (>5 for n=1.59) for various refractive indices.     

Monotosylated α- and β-cyclodextrins prepared in an alkaline aqueous solution

In order to establish the tosylated positions of α- and β-cyclodextrins, ¹³C-nmr spectra for the monotosyl-derivatives prepared in an alkaline aqueous solution were examined and determined to be in the 6-position of one glucose unit for β-cyclodextrin and to be in the C-2 position for α-cyclodextrin.     

First functionalized MRI contrast agent recognizing vascular lesions.

A new MRI-contrast agent, EB-DTPA-Gd, that has an Evans Blue analogue as a sensing unit for endothelium lesions, was designed and synthesized. The agent also has diethylenetriamine-N,N,N',N",N"-pentaacetic acid-Gd complex (Gadolinium-DTPA) units, which have been used as detection units for T1-weighted MRI. The EB-DTPA-Gd was able to recognize and adsorb to the vascular endothelium-denuded region of porcine aorta, and to decrease the relaxation time of circumferential water's protons, making possible MR imaging of the endothelium-denuded region. The compound can be employed as a contrast agent for the imaging of vascular lesions using MRI.     

The cyclodextrin-nicotinamide compound as a dehydrogenase model simulating apoenzyme-coenzyme-substrate ternary complex system

The cyclodextrin-dihydronicotinamde had a dihydronicotinamde group at the open side of cyclodextrin cavity, and showed a large rate enhancement in the reduction of substrate upon complexation comparing with NADH.     

Stability of periodic travelling wave solutions with large spatial periods in reaction-diffusion systems

We consider a spatially homogeneous system of reaction-diffusion equation defined on the interval (?∞, ∞) of the one-dimensional spatial variable x. It is known that this equation has a one-parameter family of periodic travelling wave solutions Ψ(x + ct; c) if this equation has a spatially homogeneous periodic solution φ(t). The spatial period L(c) of the travelling wave solution satisfies $\text{L(c)}\text{c}\text{→ T}\text{if}\text{c → +∞}$, where c is the propagation speed and T is the period of φ(t). We prove that, in the case c > 0 is sufficiently large, Ψ(x + ct; c) is unstable if φ(t) is “strongly unstable” and Ψ(x + ct; c) is “marginally stable” if φ(t) is “strongly stable.” If the equation is defined on a finite interval [0, l] of the variable x with the periodic boundary conditions, we can obtain a more precise result regarding the stability of $\text{Ψ(x +}\text{c}\text{?}\text{t;}\text{c}\text{?}\text{)}$, where $\text{c}\text{?}\text{> 0}$ is a speed which satisfies $\text{l = mL(}\text{c}\text{?}\text{)}$ for some positive integer m. We prove that this solution is asymptotically stable in the sense of waveform stability if $\text{c}\text{?}\text{> 0}$ is sufficiently large and if φ(t) is “strongly stable.”