Deuterium NMR and differential scanning calorimetric studies of the calcium salts of rhodium and iridium pentadeuterides, Ca2RhD5 and Ca2IrD5.

The deuterium NMR spectra of the ternary metal deuterides (TMDs) Ca(2)RhD(5) and Ca(2)IrD(5) show that the disorder is dynamic at room temperature, with barriers to the motion of 31.8 and 39.0 kJ mol(-1), respectively. At low temperatures, splittings equivalent to quadrupole coupling constants of 50.9 and 24.5 kHz were obtained for Ca(2)RhD(5) and 68.3 and 41.7 kHz for Ca(2)IrD(5) and are assigned to the planar and apical deuterium positions, respectively. Differential scanning calorimetric study of the transition in Ca(2)IrH(5) located a reversible phase transition at 284 K with an enthalpy change of 650 J mol(-1) and entropy change of 2.3 J K(-1) mol(-1).

Poly(N,N,N-trimethylammoniumalkyl acrylamide chloride) based hydrogels for serum cholesterol reduction.

Hydrogels present an attractive alternative to nanoscale block copolymer aggregates and microscale resin beads as potential asystemic serum cholesterol reduction materials. Not only would the oral delivery of these materials be more pleasant than the sand-like bile salt anion sequestrant beads but also the hydrogel preparation is much simpler than the copolymer aggregate analogues [Cameron, N. S.; Eisenberg, A.; Brown, G. R. Biomacromolecules 2002, 3, 116-123. Cameron, N. S.; Eisenberg, A.; Brown, G. R. Biomacromolecules 2002, 3, 124-132]. Our goal was to explore these materials building on our experience with bulk resins and self-assembled copolymers. In this paper, following a brief introduction to hydrogels and their application to hypercholesterolemia, the synthesis, characterization, and preliminary glycocholate binding properties of poly(N,N,N-trimethylammoniumalkyl acrylamide chloride)gel are presented [Cameron, N. S.; Eisenberg, A.; Brown, G. R. Polym. Preprints 2002, 43, 771-772].

Cocrystallization model for synthetic biodegradable poly(butylene adipate-co-butylene terephthalate).

Synthetic biodegradable poly(butylene adipate-co-butylene terephthalate), P(BA-co-BT), with 56 mol % butylene adipate, BA, was characterized by solid-state NMR spectroscopy, thermal analysis, X-ray diffraction, computer modeling, and polarization microscopy. The NMR study showed the presence of BA and butylene terephthalate, BT. T(1C) NMR measurements proved that some BA and BT units were in crystalline regions. Thermal analysis showed one glass-transition temperature and a single diffuse melting endotherm corresponding to a large melting-point depression of about 100 degrees C compared with poly(butylene terephthalate), PBT. These results suggest that there is only one crystalline phase. An X-ray fiber diagram of a stretched film could be indexed with the same unit cell as that for PBT. Computer modeling showed that the adipate unit fits into the crystal structure of PBT by adopting a TTGTG dihedral angle sequence in the crystalline conformation proposed for the cocrystallization model. The predicted fiber diagram from the proposed model qualitatively agrees with the experimental one. Polarization microscopy revealed that the spherulite growth rate of P(BA-co-BT) was similar to that for poly(butylene adipate), PBA.

Characterization of polyacrylamide-stabilized Pfl phage liquid crystals for protein NMR spectroscopy.

A new polymer-stabilized nematic liquid crystal has been characterized for the measurement of biomolecular residual dipolar couplings. Filamentous Pf1 phage were embedded in a polyacrylamide matrix that fixes the orientation of the particles. The alignment was characterized by the quadrupolar splitting of the 2H NMR water signal and by the measurement of 1H-15N residual dipolar couplings (RDC) in the archeal translation elongation factor 1beta. Protein dissolved in the polymer-stabilized medium orients quantitatively as in media without polyacrylamide. We show that the quadrupolar splitting and RDCs are zero in media in which the Pf1 phage particles are aligned at the magic angle. This allows measurement of J and dipolar couplings in a single sample.