Enthalpies of Solution of Aliphatic Amines, Aliphatic Benzene, and Alkane in Dimethyl Sulfoxide at 298.15 K

The enthalpies of solution of aliphatic compounds [{aliphatic amine, H(CH₂) _n NH₂, n = 3 to 10}, aliphatic benzene {H(CH₂) _n C₆H₅, n = 0 to 8}, and alkane {H(CH₂) _n H, n = 6 to 10}] in dimethyl sulfoxide have been measured at 298.15 K in the low concentration range from x = 5 × 10^?6 to x = 0.002. The partial molar enthalpies at infinite dilution of each aliphatic compound were determined and were found to increase linearly with increasing number of methylene groups. The enthalpic group contribution of methylene, phenyl, methyl, hydroxyl, nitrile, and amine in aliphatic compounds were 1.55, 2.65, 3.81, ?2.55, ?3.71, and ?4.43 kJ-mol^?1, respectively.     

Electronic structures of five-coordinate iron(III) porphyrin complexes with highly ruffled porphyrin ring

The spin states of the iron(III) complexes with a highly ruffled porphyrin ring, [Fe(TEtPrP)X] where X = F-, Cl-, Br-, I-, and ClO4(-), have been examined by 1H NMR, 13C NMR, EPR, and M?ssbauer spectroscopy. While the F-, Cl-, and Br- complexes adopt a high-spin (S = 5/2) state, the I- complex exhibits an admixed intermediate-spin (S = 5/2, 3/2) state in CD2Cl2 solution. The I- complex shows, however, a quite pure high-spin state in toluene solution as well as in the solid. The results contrast those of highly saddled [Fe(OETPP)X] where the I- complex exhibits an essentially pure intermediate-spin state both in solution and in the solid. In contrast to the halide-ligated complexes, the ClO4(-) complex shows a quite pure intermediate-spin state. The 13C NMR spectra of [Fe(TEtPrP)ClO4] are characterized by the downfield and upfield shifts of the meso and pyrrole-alpha carbon signals, respectively: delta(meso) = +342 and delta(alpha-py) = -287 ppm at 298 K. The data indicate that the meso carbon atoms of [Fe(TEtPrP)ClO4] have considerable amounts of positive spin, which in turn indicate that the iron has an unpaired electron in the d(xy) orbital; the unpaired electron in the d(xy) orbital is delocalized to the meso positions due to the iron(d(xy))-porphyrin(a(2u)) interaction. Similar results have been obtained in analogous [Fe(TiPrP)X] though the intermediate-spin character of [Fe(TiPrP)X] is much larger than that of the corresponding [Fe(TEtPrP)X]. On the basis of these results, we have concluded that the highly ruffled intermediate-spin complexes such as [Fe(TEtPrP)ClO4] and [Fe(TiPrP)ClO4] adopt a novel (d(xz), d(yz))3(d(xy))1(d(z)(2)1 electron configuration; the electron configuration of the intermediate-spin complexes reported previously is believed to be (d(xy))2(d(xz)), d(yz))2(d(z)(2))1.     

First total synthesis of antimitotic compound, (+)-phomopsidin

[reaction: see text] The first total synthesis of (+)-phomopsidin has been achieved via a diastereoselective transannular Diels-Alder (TADA) reaction. Key steps in the synthesis include diastereoselective ynone reduction with (-)-alpha-pinene and 9-BBN, macrocyclization by E-selective intramolecular Horner-Wadsworth-Emmons (HWE) reaction, as well as carbometalation under Wipf's conditions, followed by HWE reaction at low temperature to selectively construct the (E)-1-methylpropenyl and (1E,2E)-4-carboxy-1,3-butadienyl substituents.     

Thermal hazard analysis of mixed system of hydrazine and nitric acid

In order to obtain a better understanding of the thermal hazard of hydrazine and nitric acid mixtures which are used in plutonium and uranium recovery by extraction (PUREX) process during recycling of spent fuel in nuclear plant, DSC was carried out for the mixed system made by the small scale reaction calorimeter super-CRC in various conditions. It was found that the concentration of the nitric acid has a strong influence on the thermal behavior of the mixed system, and hydrazine nitrate which is formed in the reaction in the mixture was determined by DSC with FTIR analysis.     

Synthesis of 6-methoxyindoles and indolines. Regioselective c-6 bromination of indolines and subsequent nucleophilic substitution with a methoxyl group

Regioselective bromination of the 6-position of indolines was investigated. Treatment of indolines with bromine in sulfuric acid in the presence of silver sulfate or with bromine in superacid afforded the 6-bromoindolines, which were converted to 6-methoxyindolines and indoles.     

Controlled intracellular localization and enhanced antisense effect of oligonucleotides by chemical conjugation

Oligonucleotides can be covalently linked to peptides composed of any sequence of amino acids by solid phase fragment condensation. The peptides incorporated into the conjugates include nuclear localizing signals (NLS), nuclear export signals (NES), membrane fusion domain of some viral proteins and some designed peptides with amphipathic character. Evaluation of biological properties of DNA-peptide conjugates indicated that (a) the conjugates could bind to target RNA and dsDNA with increased affinity, (b) the conjugates were more resistant to cellular nuclease degradation, (c) the conjugate-RNA hybrids could activate RNase H as effectively as native oligonucleotides, (d) the conjugates with fusion peptides showed largely enhanced cellular uptake, (e) the conjugates with NLS could be predominantly delivered into the cell nucleus, (f) the conjugates with NES could be localized in the cytoplasm. As a result, antisense oligonucleotides conjugated with NLS could inhibit human telomerase in human leukemia cells much more strongly than phosphorothioate oligonucleotides.     

X-ray reflectivity and interfacial tension study of the structure and phase behavior of the interface between water and mixed surfactant solutions of CH3(CH2)19OH and CF3(CF2)7(CH2)2OH in hexane

The interface between water and mixed surfactant solutions of CH(3)(CH(2))(19)OH and CF(3)(CF(2))(7)(CH(2))(2)OH in hexane was studied with interfacial tension and X-ray reflectivity measurements. Measurements of the tension as a function of temperature for a range of total bulk surfactant concentrations and for three different values of the molal ratio of fluorinated to total surfactant concentration (0.25, 0.28, and 0.5) determined that the interface can be in three different monolayer phases. The interfacial excess entropy determined for these phases suggests that two of the phases are condensed single surfactant monolayers of CH(3)(CH(2))(19)OH and CF(3)(CF(2))(7)(CH(2))(2)OH. By studying four different compositions as a function of temperature, X-ray reflectivity was used to determine the structure of these monolayers in all three phases at the liquid-liquid interface. The X-ray reflectivity measurements were analyzed with a layer model to determine the electron density and thickness of the headgroup and tailgroup layers. The reflectivity demonstrates that phases 1 and 2 correspond to an interface fully covered by only one of the surfactants (liquid monolayer of CH(3)(CH(2))(19)OH in phase 1 and a solid condensed monolayer of CF(3)(CF(2))(7)(CH(2))(2)OH in phase 2). This was determined by analysis of the electron density profile as well as by direct comparison to reflectivity studies of the liquid-liquid interface in systems containing only one of the surfactants (plus hexane and water). The liquid monolayer of CH(3)(CH(2))(19)OH undergoes a transition to the solid monolayer of CF(3)(CF(2))(7)(CH(2))(2)OH with increasing temperature. Phase 3 and the transition regions between phases 1 and 2 consist of a mixed monolayer at the interface that contains domains of the two surfactants. In phase 3 the interface also contains gaseous regions that occupy progressively more of the interface as the temperature is increased. The reflectivity determined the coverage of the surfactant domains at the interface. A simple model is presented that predicts the basic features of the domain coverage as a function of temperature for the mixed surfactant system from the behavior of the single surfactant systems.     

Analysis of dynamic surface tension of tetraethyleneglycol monooctyl ether at air/water interface

The dynamic surface tension of the aqueous solutions of tetraethyleneglycol monooctyl ether (C₈E₄), a nonionic surfactant, was measured at different concentrations and temperatures. Present data at 298.15 K clearly indicate that the mechanism of adsorption is purely diffusion controlled at low concentrations (0.1~0.4 mmol/kg), and there is a switchover in adsorption mechanism to the mixed diffusion-kinetic control at higher concentrations. The calculated activation energies increase with concentration, and thus, with surface density, but decrease with temperature. The magnitude of activation energy and its increase with surface density suggest that the barrier is due to the free surface site formation by overcoming mainly the attractive van der Waals forces between the chain of adsorbed C₈E₄ molecules.     

Efficient C2'alpha-hydroxylation of deoxyribose in protein-induced Z-form DNA

DNA local conformations are thought to play an important biological role in processes such as gene expression by altering DNA-protein interactions. Although left-handed Z-form DNA is one of the best-characterized and significant local structures of DNA, having been extensively investigated for more than two decades, the biological relevance of Z-form DNA remains unclear. This is presumably due to the lack of a versatile detection method in a living cell. Previously, we demonstrated that the incorporation of a methyl group at the guanine C8 position (m(8)G) dramatically stabilizes the Z-form of short oligonucleotides in a variety of sequences. To develop a photochemical method to detect Z-form DNA, we examined the photoreaction of 5-iodouracil-containing Z-form d(CGCG(I)UGCG)(ODN 1)/d(Cm(8)GCAm(8)GCG)(ODN 2) in 2 M NaCl and found stereospecific C2'alpha-hydroxylation occurred at G(4) to provide d(CGCrGUGCG), 5. Recently, Rich and co-workers [Schwartz et al. Science 1999, 284, 1841. Schwartz et al. Nat. Struct. Biol. 2001, 8, 761] found that an ubiquitous RNA editing enzyme, adenosine deaminase 1 (ADAR1), and tumor-associated protein DML-1 specifically bind to Z-form DNA. In the present study, we investigate the photoreactivity of octanucleotide ODN 1-2 in Z-form induced by Zalpha, which is the NH(2)-terminal domain of ADAR1 responsible for tight binding of ADAR1. Detailed product analysis revealed that the C2'alpha-hydroxylated products 5 and 6 produced significantly higher yields in Z-form ODN 1-2 induced by Zalpha compared with that in 2 M NaCl. Upon treatment with ribonuclease T1, 5 and 6 were quantitatively hydrolyzed at the 3'-phosphodiester bond of the rG residue to provide d(UGCG) as a common hydrolyzed fragment on the 3' side. Quantitative analysis demonstrated that the amount of photochemically formed 5 and 6 from ODN 1-2 directly correlated with the proportion of Z-form induced by Zalpha or NaCl. These results suggest that this photochemical and enzymatic procedure can be used as a specific probe for the existence of local Z-form structure in cellular DNA.     

Characterization of hydrogen production by the co-culture of dark-fermentative and photosynthetic bacteria

Apprehension over exhaustion of fossil fuels and global warming, due to increasing amounts of CO₂, has generated a lot of attention for the subject of renewable energy. Renewable energy has an intermittency problem and its output fluctuates depending on natural conditions. Biohydrogen is one of the promising renewable energy sources. Hydrogen produced by photosynthetic bacteria depends on the intensity of light irradiation and also fluctuates with the daily variation of sunlight. The co-culture system of dark-fermentative and photosynthetic bacteria is one solution for reducing the dependency of hydrogen production on light intensity. Because these two strains of bacteria have different processes of hydrogen production, it is possible to combine different outputs so far as the co-culture system works well. This study performed hydrogen production by the co-culture system composed of agar gels embedded with both dark-fermentative bacteria, Clostridium butyricum MIYAIRI, and photosynthetic bacteria, Rhodobacter sphaeroides RV, under a fluctuating light-irradiation. The time-course of hydrogen production was determined for the different conditions of co-culture in the mixing ratios of the two bacterial strains and light-irradiation patterns. As a result, the co-culture system succeeded in producing hydrogen exceeding that in the case of a single culture system and improved its stability against light fluctuation. Hydrogen production by the co-culture system would be applicable to the reduction of intermittency in renewable energies.