Oligomer

Abstract: A water-soluble cationic conjugated oligomer, oligo(2-(4-(1-pyrenyl)butanoyloxy)ethyltrimethylammonium bromide) (OPBEAB) was synthesized by the combination of chemical and electrochemical synthesis techniques. The oligomer has an average repeat unit of 4 and a high quantum yield ( Ф ) of 0.7 in an aqueous solution containing 5.91 × 10 −3 mol L −1 sodium dodecyl sulfate (SDS). In this medium, surfactant molecules formed shielding layers along the OPBEAB chains and prevented aggregation of the oligomer and also improved its fluorescence stability. The fluorescence quenching of cationic oligomer (OPBEAB) depends strongly on the mixing sequence of the probe molecule (OPBEAB), analyte (TNT), and anionic surfactant (SDS). A molecule probe based on OPBEAB can rapidly detect ultra-trace TNT in both pure aqueous solution and environmental ground water with high sensitivity. The Stern–Volmer constant ( K SV ) of the probe in aqueous solution was measured to be as high as 5.30 × 10 5 mol −1 L and the limit of detection was about 7.0 × 10 −8 mol L −1 (70 ppb) under optimized conditions.

Abstract: Amidination of aldolase, glyceraldehyde-3-phosphate dehydrogenase, tryptophan synthetase B protein, L-arabinose isomerase, and the catalytic subunit of E coli aspartate transcarbamylase with the bifunctional reagent dimethyl suberimidate produces cross-linked proteins, with reaction predominating within oligomers Disc electrophoresis of a modified protein on polyacrylamide gel in the presence of sodium dodecyl sulfate resolves a set of species with molecular weights equal to integral multiples of the protomer molecular weight For oligomers composed of identical protomers, the number of principal species observed is identical to the number of protomers in the oligomer Application of the method to two proteins composed of dissimilar protomers, native aspartate transcarbamylase and tryptophan synthetase α2β2 complex of E coli, revealed differences in the reactivities of the different kinds of protomer within each oligomer

Abstract: Most theories of the origin of biological organization assume that polymers with lengths in the range of 30-60 monomers are needed to make a genetic system viable. But it has not proved possible to synthesize plausibly prebiotic polymers this long by condensation in aqueous solution, because hydrolysis competes with polymerization. The potential of mineral surfaces to facilitate prebiotic polymerization was pointed out long ago. Here we describe a system that models prebiotic polymerization by the oligomerization of activated monomers -both nucleotides and amino acids. We find that whereas the reactions in solution produce only short oligomers (the longest typically being a 10-mer), the presence of mineral surfaces (montmorillonite for nucleotides, illite and hydroxylapatite for amino adds) induces the formation of oligomers up to 55 monomers long. These are formed by successive "feedings" with the monomers; polymerization takes place on the mineral surfaces in a manner akin to solid-phase synthesis of biopolymers.

Abstract: Amyloid beta-protein (Abeta) oligomers may be the proximate neurotoxins in Alzheimer's disease (AD). "Oligomer" is an ill-defined term because many kinds have been reported and they often exist in rapid equilibrium with monomers and higher-order assemblies. We report here results of studies in which specific oligomers have been stabilized structurally, fractionated in pure form, and then studied by using a combination of CD spectroscopy, Thioflavin T fluorescence, EM, atomic force microscopy (AFM), and neurotoxicity assays. Abeta monomers were largely unstructured, but oligomers exhibited order-dependent increases in beta-sheet content. EM and AFM data suggest that dimerization and subsequent monomer addition are processes in which significant and asymmetric monomer conformational changes occur. Oligomer secondary structure and order correlated directly with fibril nucleation activity. Neurotoxic activity increased disproportionately (order dependence >1) with oligomer order. The structure-activity correlations reported here significantly extend our understanding of the conformational dynamics, structure, and relative toxicity of pure Abeta oligomers of specific order.