Biodegradation of random co-polypeptide hydrogels consisting of N-hydroxypropyl l-glutamine as one component

Two component random co-polypeptide hydrogels consisting of N-hydroxypropyl l-glutamine and l-alanine (Ala) or l-phenylalanine (Phe) were prepared by performing aminolysis reactions with 3-amino-1-propanol together with crosslinking reaction with 1,8-octamethylenediamine on hydrogels of the starting co-polymers consisted of γ-benzyl l-glutamate and Ala or Phe. The relationship between their bulk structure and properties was evaluated with regard to the swelling ratio in water (q), the rate of water vapor permeability (V_f), tensile properties, and enzymatic degradation behaviors of hydrogels in a pseudo-extracellular fluid (PECF). The tensile property of the hydrogels was highly dependent on q in PECF, and on the hydrophobicity of the side chains. A relationship was obtained between the V_f and q of hydrogels in PECF regardless of the differences in the nature of the side chains. Biodegradation of the hydrogels in vitro by bromelain indicated that degradation took place in bulk rather than on the surface, and that the rate of degradation was also highly dependent on q in the samples as well as on the hydrophobicity of the side chains of the samples.     

Application of ion-exchange cartridge clean-up in food analysis III. Determination of benzylpenicillin, phenoxymethyl-penicillin, oxacillin, cloxacillin, nafcillin and dicloxacillin in bovine liver and kidney by liquid chromatography with ultraviolet detection

A multiresidue analytical method was developed for the simultaneous determination of benzylpenicillin (PCG), phenoxymethylpenicillin (PCV), oxacillin (MPIPC), cloxacillin (MCIPC), nafcillin (NFPC) and dicloxacillin (MDIPC) in bovine liver and kidney. The method involves the use of an ion-exchange cartridge for sample clean-up followed by ion-pair high-performance liquid chromatography with ultraviolet detection. The recoveries of PCG, PCV, MPIPC, MCIPC, NFPC and MDIPC from bovine liver spiked at levels of 0.5 mg/kg and 0.1 mg/kg were in the range of 73–91% and 83–96% with coefficients of variation of 1.4–4.2% and 3.4–8.7%, respectively. For bovine kidney spiked at levels of 0.5 mg/kg and 0.1 mg/kg, the recoveries of these compounds were 79–92% and 82–92% with RSDs of 1.8–5.9% and 2.7–7.8%, respectively. The detection limits for the six penicillins were 0.02–0.05 mg/kg in bovine liver and kidney.     

X-Ray Diffraction Studies of Bacteriorhodopsin. Determination of the Positions of Mercury Label at Several Engineered Cysteine Residues

Abstract— The single cysteine-containing bacteriorhodopsin mutants F27C, L100C, T170C, F171C and I222C were labeled with p -chloromercuribenzoic acid, which specifically reacts with sulfhydryl groups. These cysteines should be located at the cytoplasmic ends of the transmembrane helices A, C, F or G. We determined the positions of the bound mercury atoms by X-ray diffraction of purple membrane films, with better than 1 Å accuracy. The determined mercury positions were compared with the structural model from cryoelectron microscopy (N. Grigorieff, T. A. Ceska, K. H. Downing, J. M. Baldwin and R. Henderson, J. Mol. Biol 259, 393-421, 1996). Given that the distance between the mercury and the Cα atom of the cysteine in the xy plane must be shorter than 4.5 Å and that the mercury atom is located at the δ position, the positions obtained for the mercury labels agree with their expected positions from the structural model. The present results give a rationale for detecting structural changes upon illumination as shifts occur in the mercury label position.     

Catalytic Asymmetric Total Synthesis of Exiguolide

The catalytic asymmetric total synthesis of (−)-exiguolide, a complex 20-membered macrolide embedded with a bis(tetrahydropyran) motif, is reported. The convergent synthesis involves the construction of the C1–C11 tetrahydropyran segment via catalytic asymmetric allylation and Prins cyclization, and the formation of the C12–C21 phosphonate segment via catalytic asymmetric cyclocondensation reaction and Johnson–Claisen rearrangement. The synthesis of 15-epi-exiguolide is also described.     

Magnetic and structural properties of M-type barium hexaferrites films with transition metal substitutions

We have investigated the correlation between structural and magnetic properties of M-type BaFe₁₂O₁₉ thin films (～1.4 $\mu m$) with Co-Ti (magnetic/non-magnetic) and Co-Ni(magnetic/magnetic) substitution, as BaFe_12-2xCo_xTi_xO₁₉ and BaFe_12-2xCo_xNi_xO₁₉ (0?≤?x?≤?1). With structural properties sensitively related to the magnetic properties, where ferro-ferri phase transition is involved, it has been found that magnetic properties can be substantially controlled by substitution concentration.     

Dynamical stability of a many-body Kapitza pendulum

We consider a many-body generalization of the Kapitza pendulum: the periodically-driven sine–Gordon model. We show that this interacting system is dynamically stable to periodic drives with finite frequency and amplitude. This finding is in contrast to the common belief that periodically-driven unbounded interacting systems should always tend to an absorbing infinite-temperature state. The transition to an unstable absorbing state is described by a change in the sign of the kinetic term in the Floquet Hamiltonian and controlled by the short-wavelength degrees of freedom. We investigate the stability phase diagram through an analytic high-frequency expansion, a self-consistent variational approach, and a numeric semiclassical calculation. Classical and quantum experiments are proposed to verify the validity of our results.     

Evaluation of magnetic force distribution on a pair of superconducting bulk magnets

We study the construction of superconducting permanent magnets by RE123 bulk materials and the investigation of these industrial applications such as a magnetic separation. A bulk magnet can generate strong magnetic fields exceeding 2 T, which is the limit of ordinary iron-cored electromagnets, in a compact device with a low running cost. A magnetic field distribution of the bulk magnet is a cone shape, and it contributes to an increase of magnetic force which is proportional to the product of a magnetic field and its gradient. It is important to evaluate magnetic force when the application of the bulk magnet is discussed. In this paper, two Gd123 bulk materials of 65 mm in diameter were magnetized using a pair of superconducting bulk magnet system and three-axis components of magnetic flux density (B_x,⋅B_y, and B_z) in an open space between the magnetic poles were scanned with pitch of 2 mm in each direction. From these measured data, the axial and radial components of magnetic force factor, B_z⋅dB_z/dz and B_r⋅dB_r/dr, were calculated. At 10 mm gap, the B_z⋅dB_z/dz value reached 180.6 T²/m for a field of 2.33 T, which is comparable to B_z = 6.76 T for a common 10 T–100 mm∅ superconducting magnet.