Reactive Terminal Groups Research Articles

Immobilization of acetylcoenzyme A synthetase and the preparation of an enzyme reactor for the synthesis of [ 11C]acetylcoenzyme A

The enzyme acetylcoenzyme A synthetase (acetate-CoA ligase (AMP forming), EC 6.2.1.1) from Saccharomyces cerevisiae (baker's yeast) is used for the synthesis of 1 μmol [ 11C]acetylcoenzyme A. (CoA-[ 11C]Ac). A screening of the immobilization of the enzyme on differently derivatized controlled pore glass beads (50 nm pore size and 125–180 μm particle size) was performed. Several silanes, spacer arms and terminal reactive groups were tested. The immobilized enzyme was subjected to storage stability tests. From these experiments, the method of choice was selected: immobilization on CNBr-activated controlled pore glass. The immobilized parameters were optimized further to improve the activity of the enzyme-loaded glass beads. The latter were packed in a glass column. The kinetic properties of the column were investigated and optimized to obtain an almost complete conversion of 1 (μmol acetate into acetylcoenzyme A (CoA-Ac) within a few minutes. This is realized with an enzyme reactor (13.0 × 0.5 cm) containing 6.12 U active acetylcoenzyme A synthetase immobilized onto 1 g controlled pore glass.

Influence of the specific interaction of components on the mutual solubility of modified oligomers of isobutylene and epoxide resins

An interference micromethod has been used to study the solubility of the components of epoxydiane resin-isobutylene oligomer systems with different reactive terminal groups. The introduction of fucntional groups with high reactivity yields homogeneous systems even when the nature of the components differs sharply. The possibility of predicting the solubility of oligomers with reactive groups on the basis of Flory's theory of solutions is shown.

Relative reactivity of organosilicon oligomers with terminal isocyanate groups in reactions with hydroxyl-containing compounds

IR spectroscopy has been used to study certain kinetic patterns of the reaction of organosilicon oligomers ( M = 1200) of isocyanurate structure containing terminal isocyanate groups with a number of hydroxyl-containing compounds of functionality 1–3, in dioxane and DMF. Dependence of the reaction rate constant on the concentration both of the hydroxyl-containing component and the isocyanate-containing oligomers has been established. The activity series of the hydroxyl-containing reagents is drawn up. It is shown that in urethane formation the organosilicon oligomers with reactive terminal isocyanate groups possess somewhat reduced activity as compared with the monomer organic organosilicon diisocyanates.

Dynamics of chain molecules. Intramolecular diffusion controlled reactions for a pair of terminal reactive groups

AbstractThe first order intramolecular rate constant for the reaction between the terminal groups of flexible macromolecules is calculated in the partial draining case, following the theory formulated by Wilemski and Fixman for diffusion controlled reactions. Substantial differences with respect to the nondraining and free‐draining limits are evidenced, and it is shown that the rate constant in the partial‐draining case has relevant contributions from all the modes of the bead‐spring chain. The effects of chain flexibility and hydrodynamic interaction in macromolecules of increasing molecular weight are examined. The effective diffusion constant of the end groups increases with both the flexibility and the length of the chain. Numerical results for polystyrene (PS) and polydimethylsiloxane (PDMS) are presented and employed to calculate the relative quantum yield for fluorescence quenching. For highly flexible chains, like PDMS, quenching effects are expected in a range of molecular weight well above the limit of validity of the bead‐spring model. On the contrary, for more rigid polymers, like PS, the quenching can be observed only at molecular weights lower than this limit. The calculated behavior is compared with some experimental results recently obtained by the authors.

Diffusion-controlled intrachain reactions of polymers. II Results for a pair of terminal reactive groups

The formulas and results of the preceding paper are used to calculate the rate of reaction between reactive groups attached to the ends of a polymer chain. Extensive numerical calculations have been made for both transient rate processes and steady state luminescence quenching. The results are restricted to chains in dilute solution, in either the free draining or nondraining limits and with no excluded volume forces present. A discussion of the qualitative effects of excluded volume forces on the results is included. The results suggest that experimental studies of these processes may be feasible.

Functionally Terminated Butadiene Polymers

Abstract Prepolymer technology is a relatively new science in which polymer structures of any desired type are built from partially polymerized liquid resins containing reactive functional groups. Well over one hundred low molecular weight polymers and crosslinking agents are currently available commercially. The first examples were the liquid phenolic casting resins which appeared in the mid 1930's. Unsaturated polyester-styrene mixtures were available by 1945 followed shortly by the epoxide resins and the liquid polysulfides. Today the chemist or engineer can chose among a wide assortment of liquid polymers: Polymer chain : Polyester, polyether, polyamide, polysulfide, polybutadiene, polyisobutylene Reactive group: Carboxyl, hydroxyl, sulfhydryl, amine, epoxide, isocyanate, olefin These liquid polymers may be separated into two types: those in which the reactive groups are randomly distributed along the backbone chain and those in which the functional groups are located at the ends of the chains. It is the latter with which this discussion is concerned, in particular with the functionally terminated polybutadienes. Uraneck, Hsieh, and Buck have coined the word “telechelic” for polymer molecules having two reactive terminal groups and we will use this term. The word derives from the Greek tele, far off, and chele, claw.

Telechelic elastomers

AbstractTelechelic elastomers, polymers with reactive terminal groups, can be prepared in emulsion and solution systems. Examples of characterization of the polymers and preparation of a mercapto telechelic copolymer in an emulsion system and of mercapto‐, hydroxy‐, and aziridinyl‐telechelic elastomers in solution systems are given. The elastomers were cured in peroxide or sulfur‐accelerator formulations. The telechelic polymers exhibited enhanced stress‐strain and dynamic properties in comparision to those of the controls. In tread formulations, outstanding properties were obtained for the mercapto‐and azieridinyl‐telechelic butadiene‐styrene copolymers.