Design of biomimetic catalysts by molecular imprinting in synthetic polymers: the role of transition state stabilization.

The impressive efficiency and selectivity of biological catalysts has engendered a long-standing effort to understand the details of enzyme action. It is widely accepted that enzymes accelerate reactions through their steric and electronic complementarity to the reactants in the rate-determining transition states. Thus, tight binding to the transition state of a reactant (rather than to the corresponding substrate) lowers the activation energy of the reaction, providing strong catalytic activity.

Functional mimicry of carboxypeptidase A by a combination of transition state stabilization and a defined orientation of catalytic moieties in molecularly imprinted polymers.

An artificial model for the natural enzyme carboxypeptidase A has been constructed by molecular imprinting in synthetic polymers. The tetrahedral transition state analogues (TSAs 4 and 5) for the carbonate hydrolysis have been designed as templates to allow incorporation of the main catalytic elements, an amidinium group and a Zn(2+) or Cu(2+) center, in a defined orientation in the transition state imprinted active site. The complexation of the functional monomer and the template in presence of Cu(2+) through stoichiometric noncovalent interaction was established on the basis of (1)H NMR studies and potentiometric titration.

Effect of tetracycline residues in pig manure slurry on tetracycline-resistant bacteria and resistance gene tet(M) in soil microcosms.

Effects of tetracycline residues from pig manure slurry on the prevalence of tetracycline-resistant bacteria and the tetracycline resistance gene, tet(M), were studied in soil microcosms. Four types of soil microcosms were established for a period of 152 days, supplemented with combinations of pig manure slurry and a tetracycline-resistant Enterococcus faecalis, CG110, containing the tetracycline resistance gene tet(M) (on the conjugative transposon, Tn916). The prevalence of both tetracycline-resistant aerobic bacteria and tetracycline-resistant enterococci declined rapidly until day 45 where no significant differences in the levels of tetracycline-resistant bacteria in any of the four types of microcosms could be detected.

One group of genetically similar Listeria monocytogenes strains frequently dominates and persists in several fish slaughter- and smokehouses.

Contamination of foods with the human pathogen Listeria monocytogenes may occur during processing, and the purpose of this study was to determine whether genetically similar strains colonize different processing plants or whether specific persistent strains are unique to each processing plant. We hypothesized that specific L. monocytogenes strains may be better adapted to specific environmental niches in the processing environment.

Functional mimicry of the active site of carboxypeptidase a by a molecular imprinting strategy: cooperativity of an amidinium and a copper ion in a transition-state imprinted cavity giving rise to high catalytic activity.

A model for the natural enzyme carboxypeptidase A was prepared by molecular imprinting in synthetic polymers. An unusually high activity and efficiency for carbonate hydrolysis could be obtained by imprinting with a stable transition-state analogue template and introducing an amidinium group and a Cu2+ ion-binding site in a defined orientation to each other into the active site. With substrates having a very similar structure to the template, extraordinarily high enhancements of rates of 110 000-fold were obtained of catalyzed to uncatalyzed reaction kcat/kuncat .

A new enzyme model for enantioselective esterases based on molecularly imprinted polymers.

An efficient enzyme model exhibiting enantioselective esterase activity was prepared by using molecular imprinting techniques. The enantiomerically pure phosphonic monoesters 4 L and 5 L were synthesized as stable transition-state analogues. They were used as templates connected by stoichiometric noncovalent interactions to two equivalents of the amidinium binding site monomer 1.

Amidine-based molecularly imprinted polymers-new sensitive elements for chiral chemosensors.

Using the optical measurement technique reflectometric interference spectroscopy (RIfS), the interaction of molecularly imprinted polymers (imprinted with either (R, R)- or (S, S)-2,3-di- O-benzoyltartraric acid) with the corresponding templates and template antipodes were investigated. With these sensors chiral separation with a separation factor of 1.2 could be achieved whereas a reference polymer resulted in no separation.

Stoichiometric noncovalent interaction in molecular imprinting.

In this review article the function of the binding site monomers in the molecular imprinting procedure is discussed. Especially, new developments towards stoichiometric noncovalent interactions are highlighted. In stoichiometric noncovalent interactions template and binding site monomer in an 1:1 molar ratio are nearly completely bound to each other.

Imprinting techniques in synthetic polymers--new options for chemosensors.

Highly selective molecular recognition in synthetic polymers may be the basis for a new type of chemosensor. For the preparation of such polymers, a molecular imprinting procedure during crosslinking is used to generate, with the aid of template molecules, microcavities of specific shape and with a defined arrangement of functional groups. In this review the role of the polymer matrix and the type of binding site interaction is discussed in more detail.

Management of uterine perforation following elective abortion.

Experience is reported with 28 uterine perforations encountered from June 1, 1973, to June 1, 1976, among 20,000 first trimester abortion patients at Reproductive Health Services, St. Louis, Missouri. In order to prevent this complication, one must perform an exacting pelvic examination.

Elective abortion. Complications seen in a free-standing clinic.

Experience is reported with the elective first trimester abortion of 16,410 pregnancies during a 31-month period by Reproductive Health Services of St. Louis, a free-standing clinic. Incidence of complications was 1.

Apolipoproteins in human pregnancy.

Apolipoproteins are important in the structure and metabolism of lipoproteins, and alterations in levels of apoproteins or in their interrelations occur in some forms of hyperlipemia. Pregnancy is regularly accompanied by hyperlipoproteinemia, but while data on lipoprotein lipids is available, the apopipoproteins have not been studied. To characterize the lipemia of pregnancy more completely, we studied some of the apolipoproteins in plasmas of pregnancy women.