Adsorption and structural change of beta-lactoglobulin at the diacylglycerol-water interface

Diacylglycerol (DAG)/water and triacylglycerol (TAG)/water emulsions were prepared using beta-lactoglobulin (beta-LG) as an emulsifier. The oil phase (20% in emulsion) was mixed with beta-LG solution (1% beta-LG in water, pH 7) to prepare the emulsions. A fine oil-in-water emulsion was produced from both DAG and TAG oils. The interfacial protein concentration of the TAG emulsion was higher than that of the DAG emulsion. The zeta potential of the DAG oil droplet was higher than that of the TAG oil droplet. The front-surface fluorescence spectroscopy results revealed that tryptophan residues in beta-LG moved to the more hydrophobic environment during the adsorption of protein on the oil droplet surfaces. Changes in secondary structure of beta-LG during the adsorption were determined by FT-IR spectroscopy. Decreases in the beta-sheet content concomitant with increases in the alpha-helix content were observed during the adsorption to the oil droplets, and the degree of structural change was greater for beta-LG in the TAG emulsion than in the DAG emulsion, indicating the increased unfolding of adsorbed beta-LG on the TAG oil droplet surface. Results of interfacial tension measurement supported this speculation, that is, the increased unfolding of the protein at the TAG-water interface. Trypsin- and proteinase K-catalyzed proteolysis was used to probe the topography of the adsorbed beta-LG on the oil droplet surface. SDS-PAGE analyses of liberated peptides after the proteolysis indicated the higher susceptibility of beta-LG adsorbed on the DAG oil droplet surface than on the TAG oil droplet surface. On the basis of all the results, we discussed the conformation of the adsorbed beta-LG on the two oil droplet surfaces.     

Synthesis and Applications of (ONO Pincer)Ruthenium‐Complex‐Bound Norvalines

Two (ONO pincer)ruthenium‐complex‐bound norvalines, Boc?[Ru(pydc)(terpy)]Nva?OMe ( 1 ; Boc=tert‐butyloxycarbonyl, terpy=terpyridyl, Nva=norvaline) and Boc?[Ru(pydc)(tBu‐terpy)]Nva?OMe ( 5 ), were successfully synthesized and their molecular structures and absolute configurations were unequivocally determined by single‐crystal X‐ray diffraction. The robustness of the pincer Ru complexes and norvaline scaffolds against acidic/basic, oxidizing, and high‐temperature conditions enabled us to perform selective transformations of the N‐Boc and C?OMe termini into various functional groups, such as alkyl amide, alkyl urea, and polyether groups, without the loss of the Ru center or enantiomeric purity. The resulting dialkylated Ru‐bound norvaline, n‐C₁₁H₂₃CO?l ‐[Ru(pydc)(terpy)]Nva?NH‐n‐C₁₁H₂₃ (l ‐ 4 ) was found to have excellent self‐assembly properties in organic solvents, thereby affording the corresponding supramolecular gels. Ru‐bound norvaline l ‐ 1 exhibited a higher catalytic activity for the oxidation of alcohols by H₂O₂ than parent complex [Ru(pydc)(terpy)] ( 11 a ).     

Development of a small X-ray source using an ultraviolet laser and pyroelectric crystal

We investigate a miniaturized X-ray source using an ultraviolet (UV) laser and a pyroelectric crystal and discuss potential applications in medicine. The UV laser is the fourth harmonic of a Nd:YAG laser with a wavelength of 266 nm, repetition rate of 10 Hz, and pulse energy of 40 mJ. The pyroelectric crystal is a LiNbO₃ cylinder of diameter 10 mm and length 6 mm. The prototype X-ray source we fabricated is an aluminum parallelepiped of dimensions 3 × 3 × 5 cm. The X-ray count rate of the X-ray source is maximized at approximately 1,400 cps for UV laser irradiation of approximately 5 min. After 30 min of irradiation by the UV laser, the temperature of the pyroelectric crystal rose from 295 K to 312 K. The principles of X-ray generation ensure that X-ray sources using UV lasers and pyroelectric crystals offer ample opportunity for miniaturization. We believe the X-ray source developed in this work is suitable for medical applications, although further study is needed to address points such as increasing the X-ray count rate and adjusting the temperature of the pyroelectric crystal.     

Controlled dynamics at an avoided crossing interpreted in terms of dynamically fluctuating potential energy curves

The nonadiabatic nuclear wavepacket dynamics on the coupled two lowest (1)Σ(+) states of the LiF molecule under the action of a control pulse is investigated. The control is achieved by a modulation of the characteristics of the potential energy curves using an infrared field with a cycle duration comparable to the time scale of nuclear dynamics. The transition of population between the states is interpreted on the basis of the coupled nuclear wavepacket dynamics on the effective potential curves, which are transformed from the adiabatic potential curves with use of a diabatic representation that diagonalizes the dipole-moment matrix of the relevant electronic states. The basic feature of the transition dynamics is characterized in terms of the notion of the collision between the dynamical crossing point and nuclear wavepackets running on such modulated potential curves, and the transition amplitude is mainly dominated by the off-diagonal matrix element of the time-independent electronic Hamiltonian in the present diabatic representation. The importance of the geometry dependence of the intrinsic dipole moments as well as of the diabatic coupling potential is illustrated both theoretically and numerically.     

Statistics of a Flux in Burgers Turbulence¶with One-Sided Brownian Initial Data

We study the statistics of the flux of particles crossing the origin, which is induced by the dynamics of ballistic aggregation in dimension 1, under certain random initial conditions for the system. More precisely, we consider the cases when particles are uniformly distributed on ℝ at the initial time, and if u(x,t) denotes the velocity of the particle located at x at time t, then u(x,0)= 0 for x<0 and (u(x,0), x≥ 0) is either a white noise or a Brownian motion. Received: 18 April 2001 / Accepted: 16 July 2001     

Asymptotic Properties of Solutions to 3-Particle Schrödinger Equations

We construct a generalized Fourier transformation ℱ(λ) associated with the 3-body Schr?dinger operator H=−Δ+Σ ^a V ^a (x ^a ) and characterize all solutions of (H−λ)u= 0 in the Agmon–H?rmander space ℬ^* as the image of ℱ(λ)^*. These stationary solutions admit asymptotic expansions in ℬ^* in terms of spherical waves associated with scattering channels. Received: 20 September 2000 / Accepted: 20 May 2001     

Quantification of end groups in polystyrenes by pyrolysis–gas chromatography

The determination of end groups in polystyrenes (PSts) polymerized anionically with n-butyllithium as the initiator was carried out by pyrolysis-gas chromatography (Py-GC). The relative proportions of the end groups decrease with increasing molecular weight (MW). Consequently, the peaks which reflect the structure of the end groups can be distinguished by comparing pyrograms of samples with different MW. By comparing the intensities of these peaks relative to total intensities of all the peaks in the pyrogram, the numberaverage molecular weight (M_n) of the polymer can be estimated. The observed M_n values of PSts estimated by this method are compared with those determined by size exclusion chromatography (SEC). By this method it was possible to make direct determination of M_n values of PSts with MWs between 1000 and ca. 1 million. Furthermore, the calibration curve produced by the relative intensity of one of the most characteristic peaks (2-phenyl-1-heptene; C₄H₉? CH₂C (Ph) = CH₂) for the end group to total intensity of all the peaks in the pyrogram, gave rapid and highly reproducible M_n values. © 1994 John Wiley & Sons, Inc.     

Microwave and millimeter-wave spectroscopy of the open-shell van der Waals complex Ar-HO2

Pure rotational transitions of a rare gas atom-reactive open-shell triatom van der Waals complex Ar-HO2 have been observed by Fourier transform microwave spectroscopy. The transitions observed are of a type with K(a) = 0 and 1. Furthermore, by monitoring the change of the free induction decay signal of the a-type transitions, b-type transitions have been observed by a double resonance technique in the region 18-49 GHz. All these transitions provide us precise molecular constants. The r0 structure of Ar-HO2 has been determined by fixing the structure of the HO2 monomer. The determined structure is planar and almost T shaped, where the argon atom is slightly shifted to the hydrogen atom of HO2. The experimental data supplemented by high-level ab initio calculations indicate that the van der Waals bond of Ar-HO2 is relatively rigid. On the other hand, effects on the unpaired electron distribution by the complex formation are found to be fairly small, since the fine and hyperfine constants of Ar-HO2 are well explained by those of the HO2 monomer.     

Enhancement of the Catalytic Activity of Chiral H8‐BINOL Titanium Complexes by Introduction of Sterically Demanding Groups at the 3‐Position

The activity of chiral titanium catalysts derived from H₈‐BINOL ligands in the enantioselective arylation of an aldehyde with PhTi(OiPr)₃ is significantly enhanced by an increase of the size of the substituent at the 3‐position. High enantioselectivity (> 90 % ee) can be obtained even at a substrate/catalyst ratio (S/C) of 800 for DTBP‐H₈‐BINOL (DTBP=3,5‐di‐tert‐butylphenyl) and DAP‐H₈‐BINOL (DAP=3,5‐di(9‐anthraceny)phenyl). These titanium catalysts are successfully applied to the enantioselective arylation and heteroarylation of aldehydes at a S/C ratio of 400 by using organotitanium reagents generated in situ from bromide precursors. The remarkable weakening of the intramolecular aggregation of the two ?Ti(OiPr)₃ units in a DPP‐H₈‐BINOL (DPP=3,5‐diphenylpheny)‐derived bis‐titanium complex is revealed by X‐ray and variable‐temperature (VT)‐NMR studies. Based on these observations, a catalytic cycle, involving the rate‐limiting aryl group transfer followed by aldehyde complexation and enantioselective arylation, is proposed to account for the high activity of the 3‐substituted H₈‐BINOL catalyst system.