Electrophoretic mobility and dissociation constants of tripeptides evaluated by isotachophoresis.

Ionic mobilities and dissociation constants of twenty peptides (seventeen tripeptides and a few oligoglycines) were evaluated on the basis of the observed isotachophoretic qualitative indices RE in the pH range 8.1-9.5 by the use of a least-squares method. Good correlation was obtained among the mobilities of amino acids, dipeptides and tripeptides when the clay ball model and the conventional formula weight were adopted.     

Determination of traces of lead and cadmium in high-purity tin by polarized zeeman atomic-absorption spectrometry with direct atomization of solid sample in a graphite-cup cuvette

Lead at the mug g level and cadmium at ng g -mug g levels in high-purity tin have been determined by polarized Zeeman atomic-absorption spectrometry with direct atomization of the solid sample. Pieces of high-purity tin weighing up to 5 mg for lead and 20 mg for cadmium were analysed. Calibration graphs were constructed by use of standard solutions of lead and cadmium in the presence of pure tin having lead and cadmium contents below the detection limit. The tin matrix remained in the graphite-cup cuvette after atomization and did not adhere to the wall of the cuvette, so it could be easily removed and the same cuvette repeatedly used.     

Preparation of biocarbon micro coils

ABSTRACT

A novel synthetic polymer-plant-precursor carbonization technique was developed. Carbon micro coils were prepared by the carbonization of plant helical vessels coated with polyaniline or poly(acrylonitrile-co-acrylic acid). The helical vessels served as a helical guide, while the synthetic polymers coated on the vessel surface, which consisted of cellulose, were transformed into carbon material while retaining the helical form. The helical carbon material was prepared without the use of an organic gas or solvents through a relatively simple and convenient process. This technique involved the application of natural resources, the synthesis of a conducting polymer, and carbon science. The biocarbon micro coils thus prepared in this study were characterized by infrared absorption, optical microscopy, and scanning electron microscopy. Moreover, the magnetic properties of the helical carbon were examined by electron spin resonance and a superconducting quantum interference device that proved its paramagnetic features. Additionally, the water transport function in the helical vessels was discussed.     

A mathematical aspect of a tunnel-junction for spintronic qubit

We consider the Dirac particle that lives in the 1-dimensional configuration space consisting of two quantum wires and a junction between the two. We regard the spin of a Dirac particle as spintronic qubit. We give concrete formulae explicitly expressing the one-to-one correspondence between every self-adjoint extension of the minimal Dirac operator and its corresponding boundary condition of the wave functions of the Dirac particle. We then show that all the boundary conditions can be classified into just two types. The two types are characterized by whether the electron passes through the junction or not. We also show how the tunneling produces its own phase factor and what is the relation between the phase factor and the spintronic qubit in the tunneling boundary condition.     

Spin-boson model through a Poisson-driven stochastic process

We give a functional integral representation of the semigroup generated by the spin-boson Hamiltonian by making use of a Poisson point process and a Euclidean field. We present a method of constructing Gibbs path measures indexed by the full real line which can be applied also to more general stochastic processes with jump discontinuities. Using these tools we then show existence and uniqueness of the ground state of the spin-boson, and analyze ground state properties. In particular, we prove super-exponential decay of the number of bosons, Gaussian decay of the field operators, derive expressions for the positive integer, fractional and exponential moments of the field operator, and discuss the field fluctuations in the ground state.     

The S1 ← S0 0–0 transition energies of polychlorinated dibenzofurans (PCDFs) revisited: CIS(D) and MP2 calculations with correction for correlation energies

This paper reexamines the structures and energies of dibenzofuran and twenty PCDFs in S₁–S₃ states. It was demonstrated that, although the CIS method gives a false relative ordering of excited states, the false ordering can be remedied by the CIS(D) method. Moreover the CIS geometries of typical PCDF molecules reasonably agree with their SAC-CI geometries. It was found that molecules chlorinated at the 1- and 9-positions are twisted in the S₂ state but are planar in other states, except for 1,4,6,9-TeCDF and fully chlorinated dibenzofuran (OCDF). The twisted structure of 1,4,6,9-TeCDF occurs in the S₃ state, but the structure of OCDF is twisted in every state. We partitioned the molecule into the parent structure and four chlorine groups and measured the twist energy with reference to the ground state. Then, the S_i ← S₀ 0–0 transition energies (i = 1, 2) calculated using the CIS(D) and MP2 methods could be expressed as a multiple linear equation with components and twist energy. It was further confirmed that if the multiple linear equation is corrected for residual correlation energies of the parent structure, it can predict the S₁ ← S₀ 0–0 transition energies with high precision.     

Cyclopropane-based stereochemical diversity-oriented conformational restriction strategy: histamine H3 and/or H4 receptor ligands with the 2,3-methanobutane backbone

The stereochemical diversity-oriented conformational restriction strategy can be an efficient method for developing specific ligands for drug target proteins. To develop potent histamine H(3) and/or H(4) receptor ligands, a series of conformationally restricted analogs of histamine with a chiral trans- or cis-4-amino-2,3-methano-1-(1H-imidazol-4-yl)butane structure was designed based on this strategy. These stereochemically diverse compounds were synthesized from previously developed versatile chiral cyclopropane units. Among these analogs, a trans-cyclopropane-type compound, (2S,3R)-4-(4-chlorobenzylamino)-2,3-methano-1-(1H-imidazol-4-yl)butane (5b), has remarkable antagonistic activity to both the H(3) (K(i) = 4.4 nM) and H(4) (K(i) = 5.5 nM) receptors, and a cis-cyclopropane-type compound, (2R,3R)-4-amino-2,3-methano-1-(1H-imidazol-4-yl)butane (6a), is a potent and selective H(3) receptor partial agonist (K(i) = 5.4 nM). Although (2S,3R)-4-amino-2,3-methano-1-(1H-imidazol-4-yl)butane (5a) does not have a hydrophobic group which the usual H(3) receptor antagonists have, it was found to be a potent H(3) receptor antagonist (K(i) = 20.1 nM). Thus, a variety of compounds with different pharmacological properties depending on the cyclopropane backbones and also on the side-chain functional groups were identified. In addition to the previously used 1,2-methanobutane backbone, the 2,3-methanobutane backbone also worked effectively as a cyclopropane-based conformational restriction structure. Therefore, the combination of these two cyclopropane backbones increases the stereochemical and three-dimensional diversity of compounds in this strategy, which can provide a variety of useful compounds with different pharmacological properties.     

Determination of nitrite, nitrate, bromide, and iodide in seawater by ion chromatography with UV detection using dilauryldimethylammonium-coated monolithic ODS columns and sodium chloride as an eluent

A method was developed for determination of inorganic anions, including nitrite (NO ₂ ^? ), nitrate (NO ₃ ^? ), bromide (Br^?), and iodide (I^?), in seawater by ion chromatography (IC). The IC system used two dilauryldimethylammonium bromide (DDAB)-coated monolithic ODS columns (50?×?4.6?mm i.d. and 100?×?4.6?mm i.d.) connected in series for separation of the ions. Aqueous NaCl (0.5?mol/L; flow rate, 3?mL/min) containing 5?mmol/L phosphate buffer (pH 5) was used as the eluent, and detection was with a UV detector at 225?nm. The monolithic ODS columns were coated and equilibrated with a 1-mmol/L DDAB solution (in H₂O/methanol, 90:10 v/v). The hydrophilic ions (NO ₂ ^? , NO ₃ ^? , and Br^?) were separated within 3?min and the retention time of I^? was 16?min. No interferences from matrix ions, such as chloride and sulfate ions, were observed in 35?‰ artificial seawater. The detection limits were 0.6?μg/L for NO ₂ ^? , 1.1?μg/L for NO ₃ ^? , 70?μg/L for Br^?, and 1.6?μg/L for I^? with a 200-μL sample injection. The performance of the coated columns was maintained without addition of DDAB in the eluent. The IC system was successfully applied to real seawater samples with recovery rates of 94–108?% for all ions.

Determination of cisplatin and its hydrolytic metabolite in human serum by capillary electrophoresis techniques

Cisplatin is for a long time in clinical use as efficient antitumor drug. The success in cisplatin-based chemotherapy, however, strongly depends on how careful the drug's dosages are monitored in order to reduce severe side-effects and overcome cellular resistance. The use of micellar electrokinetic chromatography with direct UV detection is described for the determination of intact cisplatin in human serum. The main product of drug's hydrolytic metabolism, cis-diammineaquachloroplatinum(II), was quantified using capillary zone electrophoresis in combination with indirect UV detection and on-line transient isotachophoresis preconcentration. The detection limits of platinum species studied were about 2-3 micromol l(-1) that allows the proposed methods to be applied for quantification of the administered levels of cisplatin as well as drug's active metabolite. Changes in the speciation of cisplatin occurring after intravenous administration can also be monitored using these simple and convenient CE techniques.     

Ga+ primary ion ToF-SIMS fragment pattern of metals and inorganic compounds.

The appearance regularity of the Ga+ primary ion ToF-SIMS fragment pattern of metals and inorganic compounds is discussed. For inorganic compounds formulated like M-A, where the valence of the cation M is +n, that of the anion A is -p; also, the chemical composition of the ToF-SIMS fragment is MxAy, the rule nx > or = (py + 1) is satisfied for positive ion fragments and nx < or = (py + 1) for negative ones. For example, for an oxide fragment of chemical composition MxOy (valence of M is +n), the chemical composition of the fragment appears obeying the rule nx > or = (2y + 1) for positive ions and nx < or = (2y + 1) for negative ones, respectively. The regularity of ToF-SIMS fragment patterns of sulfides, nitrates, sulfates etc. is discussed. Further, when the Ga+ primary ion ToF-SIMS fragment patterns of metals are observed, it can be inferred that the overlapped particle emission occurs from metal surfaces through alloying and/or clustering of Ga with metal on surfaces.