Resonance Raman spectroscopic investigation of structural changes of CO‐heme in soluble guanylate cyclase generated by effectors and substrate

The influence of the effectors YC‐1 and BAY on the CO‐heme structure of bovine lung soluble guanylate cyclase (sGC) was investigated with resonance Raman spectroscopy. The effectors produced a five‐coordinate (5c) CO‐heme in addition to the His‐bound six‐coordinate (6c) CO‐heme, and both their Soret maxima were determined by simulation. On the basis of the absorption intensity, the amount of the 5c species was not dominant, in contrast to the high activity. The heme structural features common to the 5c and 6c CO‐hemes generated by effectors are that the vinyl and propionate side chains are more coplanar to the pyrrole rings. The out‐of‐plane Raman bands were observed only for the 5c species, for which the saddling and propeller distortions of heme were deduced to be large. The Fe CO stretching bands of the 5c species at 522 cm⁻¹ and of the 6c species at 488 cm⁻¹ were most enhanced upon excitation at 407 and 422 nm, respectively, which is consistent with the simulated spectra. Unexpectedly, the ¹³C¹⁸O isotope sensitivity appeared in low wavenumber porphyrin modes. From these observations, we propose that the high catalytic activity of sGC‐CO in the presence of effectors is a result of the concerted effects of protein conformational changes triggered by certain local interactions between the heme side chains and effectors/substrate in the heme pocket, which partly induce the cleavage of the Fe Hisβ 105 bond. Copyright © 2010 John Wiley & Sons, Ltd.     

Ore-type degree condition for heavy paths in weighted graphs

A weighted graph is one in which every edge e is assigned a nonnegative number w(e), called the weight of e. For a vertex v of a weighted graph, d^w(v) is the sum of the weights of the edges incident to v. And the weight of a path is the sum of the weights of the edges belonging to it. In this paper, we give a sufficient condition for a weighted graph to have a heavy path which joins two specified vertices. Let G be a 2-connected weighted graph and let x and y be distinct vertices of G. Suppose that d^w(u)+d^w(v)2d for every pair of non-adjacent vertices u and vV(G) x,y . Then x and y are joined by a path of weight at least d, or they are joined by a Hamilton path. Also, we consider the case when G has some vertices whose weighted degree are not assumed.     

The Thermal Rearrangement of an NHC-Ligated 3-Benzoborepin to an NHC-Boranorcaradiene

An N-heterocyclic-carbene-ligated 3-benzoborepin with a bridged structure has been synthesized by double radical trans-hydroboration of benzo[3,4]cycloundec-3-ene-1,5-diyne with an N-heterocyclic carbene borane. The thermal reaction of the NHC-ligated borepin at 150 °C gives an isolable NHC-boranorcaradiene. Experiments and density functional theory calculations support a mechanism whereby the borepin initially rearranges to a boranorcaradiene by a thermal 6π-electrocyclic reaction. This is followed by 1,5-boron shift to give a rearranged boranorcaradiene. This shift occurs with stereoinversion at boron through a transition state with open-shell diradical character. This is the first example of the isolation of a boranorcaradiene from a thermal reaction of a borepin.     

Spin Filtering Along Chiral Polymers

Spin‐dependent conduction and polarization in chiral polymers were studied for polymers organized as self‐assembled monolayers with conduction along the polymer backbone, namely, along its longer axis. Large spin polarization and magnetoresistance effects were observed, showing a clear dependence on the secondary structure of the polymer. The results indicate that the spin polarization process does not include spin flipping and hence it results from backscattering probabilities for the two spin states.     

The Thermal Rearrangement of an NHC‐Ligated 3‐Benzoborepin to an NHC‐Boranorcaradiene

An N‐heterocyclic‐carbene‐ligated 3‐benzoborepin with a bridged structure has been synthesized by double radical trans‐hydroboration of benzo[3,4]cycloundec‐3‐ene‐1,5‐diyne with an N‐heterocyclic carbene borane. The thermal reaction of the NHC‐ligated borepin at 150 °C gives an isolable NHC‐boranorcaradiene. Experiments and density functional theory calculations support a mechanism whereby the borepin initially rearranges to a boranorcaradiene by a thermal 6π‐electrocyclic reaction. This is followed by 1,5‐boron shift to give a rearranged boranorcaradiene. This shift occurs with stereoinversion at boron through a transition state with open‐shell diradical character. This is the first example of the isolation of a boranorcaradiene from a thermal reaction of a borepin.     

Facile and Versatile Synthesis of End-Functionalized Poly(phenylacetylene)s: A Multicomponent Catalytic System for Well-Controlled Living Polymerization of Phenylacetylenes

A rhodium-based multicomponent catalytic system for well-controlled living polymerization of phenylacetylenes has been developed. The catalytic system is composed of readily available and bench-stable [Rh(nbd)Cl]₂, aryl boronic acid derivatives, diphenylacetylene, 50 % aqueous KOH, and PPh₃. This system offers a method for the facile and versatile synthesis of various end-functionalized cis-stereoregular poly(phenylacetylene)s because components from aryl boronic acids and diphenylacetylene were introduced to the initiating end of the polymers. The polymerization reaction shows a typical living nature with a high initiation efficiency, and the molecular weight of the resulting poly(phenylacetylene)s can be readily controlled with very narrow molecular-weight distributions (M_w/M_n=1.02–1.09). The experimental results suggest that the present catalytic system has a higher polymerization activity than the polymerization activities of other rhodium-based catalytic systems previously reported.     

Chirality sensing of various biomolecules with helical poly(phenylacetylene)s bearing acidic functional groups in water

Stereoregular, cis–transoidal poly(phenylacetylene)s bearing strongly acidic functional groups as pendants, such as a phosphonic acid and its monoethyl ester and a sulfonic acid, were found to interact with various biomolecules such as peptides, proteins, amino sugars, and carbohydrates in water, and the complexes exhibited characteristic induced circular dichroisms in the ultraviolet–visible region of the polymer backbones, which resulted from the formation of predominantly one-handed helical conformations. On the other hand, the sodium salt of poly[(4-carboxyphenyl)acetylene], bearing a weak acidic carboxy group, showed induced circular dichroisms only in the presence of carbohydrates and some positively charged proteins. The sensitivity of the polymers to the chirality of various biomolecules was also investigated with circular dichroism spectroscopy. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5039–5048, 2006     

An information-based traffic control in a public conveyance system: Reduced clustering and enhanced efficiency

A new public conveyance model applicable to buses and trains is proposed in this paper by using stochastic cellular automaton. We have found the optimal density of vehicles, at which the average velocity becomes maximum, significantly depends on the number of stops and passengers behavior of getting on a vehicle at stops. The efficiency of the hail-and-ride system is also discussed by comparing the different behavior of passengers. Moreover, we have found that a big cluster of vehicles is divided into small clusters, by incorporating information of the number of vehicles between successive stops.     

Convenient synthesis of fully and partially deuterated stereoregular poly(phenylacetylene)s bearing a carboxy pendant and helicity induction on the polymers with chiral amines and its memory

Poly[(4-carboxyphenyl)acetylene] and its derivatives deuterated in the main chain and/or on the phenyl group (poly- 1 's) were conveniently synthesized by the polymerization of 4-ethynylbenzoic acid or its derivative deuterated on the phenyl group in the presence of bases with a water-soluble rhodium complex in water or deuterium oxide. The obtained polymers possesses highly cis–transoidal stereoregular structures according to NMR and Raman spectroscopy. Possible deuterium isotope effects of these partially and fully deuterated poly- 1 's during the helicity induction with chiral amines and its memory assisted by achiral amines were investigated. The thermal cis–trans isomerization of the methyl esters of poly- 1 's was also studied with ¹H NMR spectroscopy. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4711–4722, 2004     

Numerical simulation of melting and evaporation of a cold foil target irradiated by a pre-pulse

Melting and evaporation of matter due to pre-pulse irradiation of a high-peak-power ultra-short pulse laser onto a cold foil target and the expansion of laser-produced plasma are numerically evaluated using a hydrodynamic code based on CIP (cubic-interpolated propagation) and modified C-CUP (CIP-combined unified procedure) methods. The material properties of the solid, equation of state, laser absorption coefficient, skin depth, and thermal conductivity are consistently implemented. The formation and propagation of laser-produced plasmas are obtained with good numerical stability. PACS 02.70.-c; 52.38.Mf; 52.38.Kd