Spin-lattice relaxation time as a useful indicator for the 13CNMR assignment of terminal cis- and trans-methyls in 2-methyl-1-propenyl moiety

T₁ gives a clue to assign cis- and trans-methyl carbons in 2-methyl-1-propenyl moiety.     

A stereoselective synthesis of “natural” (4S,6S,7S)-serricornin,the sex pheromone of cigarette bettle,from levoglucosenone

The natural stereoisomer of serricornin was synthesized stereoselectively from levoglucosenone. This firmly established the absolute stereochemistry of serricornin to be 4S,6S,7S. A short synthesis of (?)-δ-multistriatin was also reported.     

Protein identification by peptide mass fingerprinting and peptide sequence tagging with alternating scans of nano-liquid chromatography/infrared multiphoton dissociation Fourier transform ion cyclotron resonance mass spectrometry

We have developed a method for protein identification with peptide mass fingerprinting and sequence tagging using nano liquid chromatography (LC)/Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). To achieve greater sensitivity, a nanoelectrospray (nano-ES) needle packed with reversed-phase medium was used and connected to the nano-ES ion source of the FTICR mass spectrometer. To obtain peptide sequence tag information, infrared multiphoton dissociation (IRMPD) was carried out in nano-LC/FTICR-MS analysis. The analysis involves alternating nano-ES/FTICR-MS and nano-ES/IRMPD-FTICR-MS scans during a single LC run, which provides sets of parent and fragment ion masses of the proteolytic digest. The utility of this alternating-scan nano-LC/IRMPD-FTICR-MS approach was evaluated by using bovine serum albumin as a standard protein. We applied this approach to the protein identification of rat liver diacetyl-reducing enzyme. It was demonstrated that this enzyme was correctly identified as 3-alpha-hydroxysteroid dehydrogenase by the alternating-scan nano-LC/IRMPD-FTICR-MS approach with accurate peptide mass fingerprinting and peptide sequence tagging.     

Room-Temperature Phosphorescence from a Series of 3-Pyridylcarbazole Derivatives

Exploration of pure metal-free organic molecules that exhibit strong room-temperature phosphorescence (RTP) is an emerging research topic. In this regard, unveiling the design principles for an efficient RTP molecule is an essential, but challenging, task. A small molecule is an ideal platform to precisely understand the fundamental role of each functional component because the parent molecule can be easily derivatized. Here, the RTP behaviors of a series of 3-pyridylcarbazole derivatives are presented. Experimental studies in combination with theoretical calculations reveal the crucial role of the n orbital on the central pyridine ring in the dramatic enhancement of the intersystem crossing between the charge-transfer-excited singlet state and the locally excited triplet states. Single-crystal X-ray crystallographic studies apparently indicate that both the pyridine ring and fluorine atom contribute to the enhancement of the RTP because of the restricted motion owing to weak C−H⋅⋅⋅N and H⋅⋅⋅F hydrogen-bonding interactions. The single crystal of the fluorine-substituted derivative shows an ultra-long phosphorescent lifetime (τ_P) of 1.1 s and a phosphorescence quantum yield (Φ_P) of 1.2 %, whereas the bromine-substituted derivative exhibits τ_P of 0.15 s with a Φ_P of 7.9 %. We believe that this work provides a fundamental and universal guideline for the generation of pure organic molecules exhibiting strong RTP.     

Design of Chitosan-5Fu Conjugate Exhibiting Antitumor Activity

In order to provide a macromolecular prodrug of 5-fluorouracil (5FU) reducing the side effects, having an affinity for tumor cells, and exhibiting strong antitumor activity, the covalent attachments of 5FUs to chitosan and chitosamino-oligosaccharide (COS) through hexamethylene spacer groups via urea, urea bonds were carried out. The effect of prolongation of life was tested in vivo against p388 lyrnphocytic leukemia in female CDF, mice by intra-peritoneal (i.p.) transplantation/i.p. injection and the growth-inhibitory effect on Meth-A fibrosarcoma or MH-134Y heputoma was evaluated in vivo in SPF-C3H/He scl male or Balb/c male mice by subcutaneous (s.c.) implantation/intravenous (i.v.) injection. The effects of the degree of polymerization of chitosan and     

Expression and Characterization of Recombinant GH11 Xylanase from Thermotolerant Streptomyces sp. SWU10

Xylans are major hemicellulose components of plant cell wall which can be hydrolyzed by xylanolytic enzymes. Three forms of endo-β-1,4-xylanases (XynSW1, XynSW2A, and XynSW2B) produced by thermotolerant Streptomyces sp. SWU10 have been reported. In the present study, we described the expression and characterization of the fourth xylanase enzyme from this bacteria, termed XynSW3. The gene containing 726 bp was cloned and expressed in Escherichia coli. The recombinant enzyme (rXynSW3) was purified from cell-free extract to homogeneity using Ni-affinity column chromatography. The apparent molecular mass of rXynSW3 was 48 kDa. Amino acid sequence analysis revealed that it belonged to a xylanase of glycoside hydrolase family 11. The optimum pH and temperature for enzyme activity were 5.5–6.5 and 50 °C, respectively. The enzyme was stable up to 40 °C and in wide pH ranges (pH 0.6–10.3). Xylan without arabinosyl side chain is the most preferable substrate for the enzyme. By using birch wood xylan as substrate, rXynSW3 produced several oligosaccharides in the initial stage of hydrolysis, and their levels increased with time, demonstrating that the enzyme is an endo-acting enzyme. The major products were xylobiose, triose, and tetraose. The rXynSW3 can be applied in several industries such as food, textile, and biofuel industries, and waste treatment.     

Photoinduced electron transfer processes of fullerene rotaxanes containing various electron-donors

The photosensitized electron-transfer processes in the rotaxane hybrids composed with electron-accepting fullerenes and various electron-donors placed in the rotaxanes are revealed with time-resolved fluorescence and absorption spectral methods. Porphyrins are most useful as light-harvesting donors and photosensitizing donors. In addition, aromatic amines and ferrocene act as electron-donor and also hole-shifting reagents in multi-component rotaxanes. In the rotaxanes with spatially placed donor-acceptor molecules, the role of triplet states becomes important compared with the covalently connected donor–acceptor molecular systems, which may be related to the “through-space” and “through-bond” electron transfer, respectively. In the designed multi-component rotaxanes which maintain mechanically or topologically the electron-acceptor, electron-donor, and hole-shifter, the photoinduced electron transfer, hole-shift, electron–hole recombination are established. As a whole, contribution of the triplet excited states is prominent compared with the covalently bonded molecules and supramolecular systems constructed with coordination bonds.     

Syntheses of new unsymmetrically dodecakis(trifluoroethoxy)‐substituted metallophthalocyanines by a palladium‐catalyzed cross‐coupling reaction

Novel unsymmetrical vanadyl and zinc dodecakis(2,2,2‐trifluoroethoxy)phthalocyaninates with an iodo group were synthesized by a statistical condensation route. The palladium‐catalyzed coupling reaction between such monoiodinated metallophthalocyanines and terminal acetylenic derivatives gave various new unsymmetrically dodecakis(2,2,2‐trifluoroethoxy)‐substituted metallophthalocyanines with extended exocyclic π‐conjugation. Unsymmetrical zinc dodecakis(2,2,2‐trifluoroethoxy)phthalocyaninate with a nitro group was also prepared for comparison. All the target phthalocyanines were separated by common col umn chromatography and characterized by elemental analysis, ir and ¹H‐nmr, uv‐visible and fast‐atombombardment mass spectroscopy.     

Determination of elemental and ionic compositions for diesel exhaust particles by particle induced X-ray emission and ion chromatography analysis.

The purpose of this study is to clarify the chemical characterization of PM2.5 and PM10 in diesel exhaust particles (DEP). Sampling of PM2.5 and PM10 in DEP was carried out in November 1999 using an automobile exhaust testing system at the National Traffic Safety and Environment Laboratory, with a diesel truck (engine type: direct injection, displacement: 7,961 cc, carrying weight: 2,020 kg, equivalent inertia weight: 5,600 kg) placed on a chassis dynamometer. Sampling conditions included idling, constant speed of 40 km/h, M-15 test pattern and 60%-revolution/40%-load of maximum power. Samples were collected on a polycarbonate membrane filter (Nuclepore, pore size: 0.8 microm) using a MiniVol Portable Air Sampler (Airmetrics Co., Inc.). The concentrations of several elemental and ionic species in the PM2.5 and PM10 samples were determined by particle induced X-ray emission (PIXE) and ion chromatography analysis. PIXE analysis of the PM2.5 and PM10 samples revealed 15 elements, of which Na, Mg, Si, S, Cl, Ca, Fe and Zn were found to be the major components. Ionic species were Cl-, NO2-, NO3-, SO4(2-), Na+, NH4+, K+ and Ca2+. Concentrations of elements and ionic species under the sampling condition of 60%-revolution/40%-load were highest in comparison with those of the other sampling conditions. The elemental and ionic species data were compared for PM2.5 and PM10; PM2.5 concentrations were 70% or more of PM10 concentrations for the majority of elements, and concentrations of ionic species in PM2.5 and PM10 were almost identical.