Cloning of poly(aspartic acid) (PAA) hydrolase-1 gene from Pedobacter sp. KP-2 and hydrolysis of thermally synthesized PAA by its gene product

Pedobacter sp. KP-2 can degrade and metabolize thermally synthesized alpha,beta-poly(D,L-aspartic acid) (tPAA), which contains 70% of unnatural beta-amide units, with high-molecular-weight. In this study, gene cloning and molecular characterization of PAA hydrolase-1 from KP-2 was carried out. Gene analysis reveals that deduced amino acid sequence of the enzyme shows a similarity to only that of PAA hydrolase-1 from Sphingomonas sp. KT-1. GPC and NMR analyses of the hydrolyzed products of tPAA by PAA hydrolase-1 of KP-2 indicate that this enzyme cleaves the beta-beta amide linkage via endo-mode to yield oligo(aspartic acid) from tPAA. Taking the composition of tPAA and the substrate specificity of PAA hydrolase-1 into consideration, the enzyme possibly plays a crucial role in tPAA biodegradation by KP-2.     

Use of dimethyl carbonate as a solvent greatly enhances the biaryl coupling of aryl iodides and organoboron reagents without adding any transition metal catalysts

The coupling reaction of aryl iodides with arylboronic acids to give biaryl compounds can be efficiently performed without adding a transition metal catalyst. The key to success is the use of dimethyl carbonate as a solvent. This finding provides a new strategy for constructing a biaryl linkage.     

Crystal structures and magnetic properties of new europium melilites Eu(2)MSi(2)O(7) (M = Mg, Mn) and their strontium analogues

Synthesis, crystal structures, and magnetic properties of melilite-type oxides A(2)MSi(2)O(7) (A = Sr, Eu; M = Mg, Mn) were investigated. These compounds crystallize in the melilite structure with space group P4?2(1)m. The (151)Eu Mo?ssbauer measurements show that the Eu ions are in the divalent state. The Eu(2)MgSi(2)O(7) is paramagnetic down to 1.8 K. Long-range antiferromagnetic ordering is observed at 3.4 K for Sr(2)MnSi(2)O(7). On the other hand, the Eu(2)MnSi(2)O(7) shows a ferrimagnetic transition at 10.7 K. From the magnetization and specific heat measurements, it is found that the Eu(2+) (14 μ(B)) and Mn(2+) (5 μ(B)) sublattices order antiferromagnetically. This result indicates that an interaction between f-d electrons (Eu-Mn) predominantly operate in this compound.     

Debonding dynamics of pressure-sensitive adhesives: 3D block model

We develop a 3-dimensional mechanical model which describes cavity expansions in a viscoelastic solid medium during the debonding phase of the probe-tack test. The stress-strain curves are in good agreement with experiments for the typical pressure-sensitive adhesives. We also show that the separation speed dependence can be explained by viscous dissipations due to large strain rates around the cavities.     

Influence of nonlinear atomic interaction on excitation of intrinsic localized modes in carbon nanotubes

Excitation of intrinsic localized modes (ILMs) in carbon nanotubes (CNTs) with different chiral structures was investigated by molecular dynamics simulations. For CNTs with a chiral angle less than or equal to 30^°, energy concentration that continued for more than 200 fs was found in a localized area, where a pair of neighboring atoms strongly oscillated with a higher vibrational frequency than the upper bound of phonon bands. This evidently indicates excitation of the ILM. On the other hand, the ILM was not excited in CNTs with a chiral angle greater than or equal to 41^°. Analyzing the nonlinearity of the interaction between excited atoms in the ILM vibration mode, we elucidated that nonlinearity predominates the selective ILM excitation. Furthermore, stronger nonlinearity excites ILMs with both higher frequency and longer lifetime.     

Photo-triggered generation of a free thiol group on DNA: application to DNA conjugation

DNA oligomers possessing a 2-nitrobenzyl (NB) protected thiol group have been prepared. The photo-remove of the NB to generate a free thiol group in DNA has been analyzed by using reverse-phase HPLC and denaturing gel electrophoresis. The photo-triggered generation of the thiol function in DNA was applicable in the light-initiated ligation of thiol-modified DNA oligomers and Au–DNA conjugation.     

Rational design of proteolytically stable, cell-permeable Peptide-based selective mcl-1 inhibitors

Direct chemical modifications provide a simple and effective means to "translate" bioactive helical peptides into potential therapeutics targeting intracellular protein-protein interactions. We previously showed that distance-matching bisaryl cross-linkers can reinforce peptide helices containing two cysteines at the i and i+7 positions and confer cell permeability to the cross-linked peptides. Here we report the first crystal structure of a biphenyl-cross-linked Noxa peptide in complex with its target Mcl-1 at 2.0 ? resolution. Guided by this structure, we remodeled the surface of this cross-linked peptide through side-chain substitution and N-methylation and obtained a pair of cross-linked peptides with substantially increased helicity, cell permeability, proteolytic stability, and cell-killing activity in Mcl-1-overexpressing U937 cells.     

Donor–Acceptor Heterojunction Configurations Based on DNA–Multichromophore Arrays

Multichromophore arrays of bis(2‐thienyl)diketopyrrolopyrrole (DPP) and naphthalenediimide (NDI) with two Zn^II‐cyclens were constructed using thymidine DNA as a scaffold through the binding of the Zn^II‐cyclens with thymine bases. We demonstrate photocurrent generation in a donor–acceptor heterojunction configuration consisting of the DPP (donor) and NDI (acceptor) arrays co‐immobilized on an Au electrode. The co‐immobilized electrode exhibited good photocurrent responses because of the efficient charge separation between the DPP and NDI arrays. In contrast, an immobilized electrode consisting of randomly assembled DPP‐NDI arrays generated no photocurrent response because DPP formed ground‐state charge‐transfer complexes with NDI in the randomly assembled arrays. Therefore, our approach to generate donor–acceptor heterojunctions based on DNA–multichromophore arrays is a useful method to efficiently generate photocurrent.