Orientation-dependent interactions in polymer systems: Segmental orientation,miscibility, and self-organization

Three co-operative phenomena that are supposed to originate in the orientation-dependent interactions among polymer segments are discussed and attempted to be interpreted in terms of a common set of polymer models.     

Fractionation of apple procyanidins by size-exclusion chromatography.

Oligomeric constituents of apple procyanidins were fractionated by size-exclusion chromatography using a TSKgel Toyopearl HW-40F column. The best separation was obtained using a mobile phase of acetone-8 M urea (6:4; adjusted to pH 2) at a flow-rate of 1.0 ml/min. In this chromatographic system, the use of 8 M urea in the mobile phase resulted in a molecular sieve effect without any surface affinity interaction between the gel beads and the procyanidin molecules. Each fraction obtained was examined by reversed-phase high-performance liquid chromatography and time-of-flight mass spectrometry. The order of elution of the procyanidins from the column was coincident with their degree of polymerization.     

Synergy of organic dyes for KDP crystal growth

Single potassium dihydrogen phosphate (KDP) crystals were grown in a supersaturated solution containing an organic dye (sunset yellow FCF, brilliant blue FCF, and sky blue). The growth rate, morphology, and impurity dye distribution of faces, (100) and (101) in a KDP crystal were measured as dye concentration and the supersatutation of KDP were changed. Complete expressions for the effect of dye on all aspects of the growth of KDP crystals were discussed. The growth rates of (100) and (101) faces were well correlated by the empirical equation, and resulted in good estimation of the morphology. The distribution of dye in a KDP crystal was represented by the distribution model containing the minimum growth rate for coloring. The growth rate equation and distribution equation were expressed by functions of the supersaturation and dye concentration, and they could effectively provide the operational conditions with coloring the KDP crystal. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The study of heat stress in tomato fruits by NMR microimaging.

The ripening of the tomato fruit was delayed for several days (average 5 days) by a 1-day heat treatment at 42 degrees C. Ethylene production increased during the first 3 h, but, after 6 h inhibition was almost total in tomato fruit incubated at 42 degrees C. However, recovery of ethylene production was rapid if fruits were returned to a temperature of 25 degrees C after heating. In NMR microimaging, three imaging pulse sequences with different repetition and echo times at 42 degrees C were used to obtain the proton density (TR = 6000 ms, TE = 15 ms), the T1 weighted image (TR = 1000 ms, TE = 15 ms) and the T2-weighted image (TR = 6000 ms, TE = 120 ms). After 12 h heating, the water in locular tissues began to show shorter T1 and T2 values. Though the tomatos were returned to 25 degrees C and preserved one more day, the water having a shorter T2 value in locular tissues, did not change. These results show that tomato fruit do not fully recover from heating even after one day, although ethylene production is recovered almost immediately. For this reason, we suggest that some denaturation event inside the tomato, which goes on after the end of heating, is the cause of the delay in tomato ripening.     

Polymorphism of phenylpyruvic acid studied by IR, Raman and solid state C NMR spectroscopy

Polymorphs I and II of phenylpyruvic acid are obtained as mixtures of both crystal forms or relatively pure crystals, from different solvents. Polymorph I is more stable than polymorph II at room temperature. Spectral characteristics of these polymorphs are discussed on the basis of IR, Raman and solid state ¹³C NMR spectra. Also, the assignment of the IR features observed in the 1600–1700 cm⁻¹ region is re-investigated by referring to the spectra of heavy-atom substituted derivatives. It is suggested that the C=O stretching band is split by the crystal field for both polymorphs.     

Impact of intermolecular vibrational coupling effects on the sum-frequency generation spectra of the water/air interface

ABSTRACT

We have examined the impact of intermolecular vibrational coupling effects of the O-H stretch modes, as obtained by the surface-specific velocity-velocity correlation function approach, on the simulated sum-frequency generation spectra of the water/air interface. Our study shows that the inclusion of intermolecular coupling effects within the first three water layers, i.e. from the water/air interface up to a distance of 6?Å towards the bulk, is essential to reproduce the experimental SFG spectra. In particular, we find that these intermolecular vibrational contributions to the SFG spectra of the water/air interface are dominated by the coupling between the SFG active interfacial and SFG inactive bulk water molecules. Moreover, we find that most of the intermolecular vibrational contributions to the spectra originate from the coupling between double-donor water molecules only, whereas the remaining contributions originate mainly from the coupling between single-donor and double-donor water molecules.     

Synthesis of Deuterium-Labeled Vitamin D Metabolites as Internal Standards for LC-MS Analysis

Blood levels of the vitamin D₃ (D₃) metabolites 25-hydroxyvitamin D₃ (25(OH)D₃), 24R,25-dihydroxyvitamin D₃, and 1α,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃) are recognized indicators for the diagnosis of bone metabolism-related diseases, D₃ deficiency-related diseases, and hypercalcemia, and are generally measured by liquid-chromatography tandem mass spectrometry (LC-MS/MS) using an isotope dilution method. However, other D₃ metabolites, such as 20-hydroxyvitamin D₃ and lactone D₃, also show interesting biological activities and stable isotope-labeled derivatives are required for LC-MS/MS analysis of their concentrations in serum. Here, we describe a versatile synthesis of deuterium-labeled D₃ metabolites using A-ring synthons containing three deuterium atoms. Deuterium-labeled 25(OH)D₃ (2), 25(OH)D₃-23,26-lactone (6), and 1,25(OH)₂D₃-23,26-lactone (7) were synthesized, and successfully applied as internal standards for the measurement of these compounds in pooled human serum. This is the first quantification of 1,25(OH)₂D₃-23,26-lactone (7) in human serum.