Concentration control for protein crystallization via a continuously-fed crystallization chamber

A continuously-fed crystallization chamber that allows for kinetic path control through the crystallization phase diagram (from labile/nucleation to metastable/growth) was fabricated and used to crystallize lysozyme. A lumped kinetic model was developed, and parameters for heterogeneous nucleation kinetics were determined. Heterogeneous nucleation was found to have faster nucleation kinetics and slower growth kinetics than homogeneous nucleation, as expected. The major contributions of the new device are (1) to allow better control of the chemical environment for studies of crystal nucleation and growth, and (2) to allow lumped-model analysis of those studies to extract kinetic parameters.     

Nanotube and three-way nanotube formation with nonionic amphiphilic block peptides

Amphiphilic block polypeptides having a helical hydrophobic block with a uniform chain length and a hydrophilic nonionic block were newly synthesized and self-assembled into homogeneous nanotubes with ca. 60 nm diameter and ca. 200 nm length. The tubular assembly was shown to be elongated by heating over micrometer length without changing the diameter. Notably, a distinctive three-way nanotube was obtained just by mixing two kinds of amphiphilic polypeptides with the same helical hydrophobic block but different chain lengths of the hydrophilic block. The morphology of the molecular assemblies was shown to be tunable from a curved sheet-shaped assembly to a long or short nanotubular assembly and a three-way nanotubular assembly by suitable molecular design of the hydrophobic block, selection of the chain length of the hydrophilic block, mixing two-type block peptides, and processing such as heating.     

Asymmetric Michael addition of boronic acids to a γ-hydroxy-α,β-unsaturated aldehyde catalyzed by resin-supported peptide

A resin-supported peptide catalyst effective for the asymmetric Michael addition of boronic acids to (E)-4-hydroxybut-2-enal was developed. From a spectral study, it was revealed that the optimum peptide consisted of both a β-turn and helix. Such a combination of secondary structures was essential for achieving a high catalytic ability.     

Adsorption-induced structural transition of an interpenetrated porous coordination polymer: detailed exploration of free energy profiles

Specific types of coordination polymers show an adsorption-induced structural transition, or so-called "gate adsorption", in which a host framework is said to change its structure from a "closed" nonporous phase to an "open" porous one for guest molecules. To identify the pathway for such a structural transition, we perform grand canonical Monte Carlo simulations for the adsorption of guest molecules in a host interpenetrated framework and calculate the free energy profiles of the structural changes in a complete three-dimensional space. In addition to the open phase found in our previous analyses along a fixed one-dimensional path, we reveal the existence of another open configuration. Each of the two open phases yields the status of global minimum to the other depending on the external pressure, resulting in a two-step isotherm. Moreover, the shape of adsorption hysteresis associated with the structural transition can change depending on the energy barrier between a metastable and a stable state that the system can overcome. Our simulations not only give a comprehensive understanding of stepped isotherms observed empirically but also suggest that isotherms with hysteretic gate adsorption is closely related to the thermal fluctuation of the system.     

Stability of pyrrolidone derivatives against γ-ray irradiation

To evaluate the stability of N-alkylated pyrrolidone derivatives(NRPs),which are supposed to be used as precipitants for U(VI) and Pu(IV,VI) species in HNO 3 media,under irradiation environment,some candidate NRPs were irradiated by γ-ray.Irradiation to HNO 3 solutions up to 6 mol dm 3(= M) containing 2 M N-n-butyl-2-pyrrolidone(NBP),one of NRPs with lower hydrophobicity,has revealed that the residual ratios of NBP in the samples of HNO 3 up to 3 M decreased identically and linearly.Approximately 20% of NBP was found to be degraded after the irradiation at 1 MGy.It was also found that the decrease in the precipitation ratio of UO 2 2+(P.R.,%) was gentle and that the P.R.values were relatively in accordance with the residual ratios of NBP.On the other hand,the degradation of the samples irradiated in 6 M HNO 3 was found more distinguished.It was proposed from the analyses of degraded compounds that the degradation of NBP in HNO 3 by γ-ray irradiation started from the cleavage of the pyrrolidone ring by the addition of oxygen atom originating from HNO 3,followed by the formation of chain compounds by the successive addition of oxygen,leading to the generation of oxalic acid and acetic acid.The stability of other NRPs in 3 M HNO 3 was evaluated to be nearly identical with that of NBP except lower P.R.values of the samples containing NRPs with higher hydrophobicity irradiated at more than 0.5 MGy.     

Effect of hetero-interfaces on in situ wafer curvature behavior in InGaAs/GaAsP strain-balanced MQWs

Using high-accuracy in situ curvature measurement during growth of InGaAs/GaAsP strain-compensated multiple quantum wells (MQWs) by metal organic vapor phase epitaxy (MOVPE), we have successfully clarified the effect of hetero-interfaces on strain control in InGaAs/GaAsP strain-balanced MQWs. By analyzing curvature transients and X-ray diffraction (XRD) fringe patterns, we found that an inadequate gas-switching sequence induces unintended atomic content at the interfaces between InGaAs and GaAsP and then influences the average strain of the structure. Through considering the atomic characteristics and measuring the reflectance anisotropy transient during growth, it has been revealed that the optimized stabilization time for arsenic and phosphorus mixture before GaAsP barrier growth should be longer than 3 s at 610 °C.