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The UV circular dichroism (UVCD) spectra of tri-alanine dissolved in D2O, H2O, and glycerol are measured. The results indicate the coexistence of a polyproline II or 3-helix and a disordered flat beta-strand conformation, in complete agreement with predictions from spectroscopic data.

The synthesis of polypropylenes via polymerization of propylene using 2-arylindene metallocenes is described. This article presents kinetic and mechanistic models of the synthetic approaches, catalysis, and stereoselectivity. Application of the process in the polyolefin manufacture is also discussed.

Co2+ ion interaction with dendrimers of the poly(propylene amine) group with densyl units, is discussed.

Microtiter plate wells modified with thin approximately 20 (mu)m) polymeric films capable of optically sensing macromolecular protamine and other polycationic species are described. The plates are prepared by coating the bottom of each well of a conventional 96-well polypropylene plate with an adherent polymer film (a mixture of poly(vinyl chloride) and polyurethane) containing a lipophilic 2',7'-dichlorofluorescein derivative. Surprisingly, optical response toward polycations is shown to result from the extraction of the fluorescein derivative from the polymer film into a lyophobic colloidal phase at the sample/film interface. This new phase is likely composed of a micellular-type ion pair complex between the analyte polycation from aqueous sample phase and the deprotonated form of the fluorescein derivative. Accumulation of the deprotonated fluorescein species in this interracial region induces an absorbance change measured at 540 nm. Optimized plates can be used to sense protamine concentrations in the range of 0-100 (mu)g/mL in 10 min with little or no response to physiological levels of common cationic species (Na(super +), K(super +), Ca(super 2+), etc.). The modified plates are shown to be useful as simple optical detectors for measuring heparin levels in plasma via titrations with protamine and for monitoring protease activities (trypsin and plasmin) that cleave polycationic peptides/proteins such as protamine into smaller peptide fragments that are not detected by the sensing films. Assays for 'clot busting' plasminogen activators (streptokinase, urokinase, and tissue plasminogen activator) are also demonstrated using this relatively simple microtiter plate-based polycation detection system.

The preparation and properties of poly(propylene amine) dendrimers are reported.

The analysis of free induction decay curves of an isotactic polypropylene film obtained at different temperatures is presented. A combination of the methods of Gardner and Prony was used for the quantitative and qualitative analysis of induction decay curves that were recorded at 40, 60, 80, and 100 degrees Celsius at constant time intervals. These multicomponent decay curves provided information about the physicochemical structure of the polymer sample. Results allowed each component to be characterized by a specific model function based on spin-spin relaxation.

Research was conducted to examine the propylene polymerization behavior of rac- and meso-dimethylsilyl(bis(2-phenylindenyl))zirconium dichloride as a model for the production of elastomeric polypropylene by the two rotamers of bis(2-phenylindenyl)zirconium dichloride. The relative rates of propagation for the meso and rac rotamers could be calculated for the unbridged system by conducting polymerizations with the stereorigid isomers. Results indicate that the rac isomer is favored in the isomerization equilibrium for the unbridged catalysts.

A study was conducted to examine the synthesis of rod-coil molecules containing poly(propylene oxide) (PPO) in ethyl 4-[4-oxypoly(propyleneoxy)-propyloxy]-4'-biphenylcarboxyloxy]-4-biphenyl carboxylate. Several techniques were employed in evaluating the molecules which include optical polarized microscopy, X-ray diffraction and differential scanning calorimetry. The findings showed that the rod-coil molecules aggregate into microphore-separated monolayer lamellar structures.

Reversed-phase membrane introduction tandem mass spectrometry can directly and continually identify volatile organic compounds dissolved in organic solvents. This spectrometric method utilizes a porous polypropylene membrane which increases solvent flow into the mass spectrometer's ion source for analysis. Modification of the membrane and solvent involved facilitates the optimization of chemical ionization conditions which improves detection of various dissolved compounds. Moreover, the method's successful detection of tert-butyl methyl ether and thiophene in gasoline shows the method's viability in the identification of specific compounds in complex systems.

The suitable increase of density allows crystallization of 3-fold helical chains of isotactic polypropylene (iPP) macromolecules in a new form characterized by trigonal unit cell, where the helical symmetry of the chains is maintained in the crystal lattice. The analysis shows that the crystallization of the trigonal form occurs at higher comonomer concentrations in the case of a smaller comonomer, such as pentene.

Ion mobility/time-of-flight measurements and molecular modeling simulations are employed to investigate the gas-phase conformations of a series of polyproline ions that are obtained by electrospraying aqueous and propanol solutions. Molecular dynamics simulations are used to explore the structures of the ions.

In the stabilization of secondary structure, interactions between side chains, and in particular salt bridges, have been shown to be important. The contribution of a salt bridge formed between a lysine and a glutamate to the polyproline II (PII) helical content of proline-rich peptides is investigation.

Research is presented concerning the production of rac-(EBI)ZrCH2CHClR+ intermediates by the insertion of vinyl chloride into rac-(EBI)ZrR+. The rates of insertion of vinyl chloride and propylene are discussed.

Single-component, syndiospecific group 3 metallocene catalysts were prepared and led to the discovery of the ligand system of the Cs symmetric zirconocene (2) which appears to be closely related to the Cs symmetric ansa-metallocene catalyst (1). As expected, the bulky (SiMe3) substituents on the lower cyclopentadienyl ligand acted in the same way as the fluorenyl ligand of 1. Surprisingly, 2 in combination with methylaluminoxane in liquid propylene at 0 degree C generated essentially atactic polypropylene.