A Hapten for the Generation of Antibody Phosphatases

Abstract

A series of hydroxymethylene and α,β-unsaturated aminophosphinic acids was prepared, modelled on the ‘exploded’ transition state proposed (Herschlag [1]) for the chemical hydrolysis of phosphate monoesters. They exhibit the dual utility of being transition state analogues for the chemical hydrolysis of phosphate monoesters and having the potential for inhibition of phosphatase enzymes. (1) was chosen to be utilised as a hapten molecule for the generation of catalytic antibodies.     

A Generalized Rational Interpolation Problem and the Solution of the Welch–Berlekamp Key Equation

We show that an algorithm designed to solve the Welch–Berlekamp key equation may also be used to solve a more general problem, which can be regarded as a finite analogue of a generalized rational interpolation problem. As a consequence, we show that a single algorithm exists which can solve both Berlekamp's classical key equation (usually solved by the Berlekamp–Massey algorithm) and the Welch–Berlekamp key equation which arise in the decoding of Reed–Solomon codes.     

Quantum Mechanical and Experimental Validation that Cyclobis(paraquat‐p‐phenylene) Forms a 1:1 Inclusion Complex with Tetrathiafulvalene

The promiscuous encapsulation of π‐electron‐rich guests by the π‐electron‐deficient host, cyclobis(paraquat‐p‐phenylene) (CBPQT⁴⁺), involves the formation of 1:1 inclusion complexes. One of the most intensely investigated charge‐transfer (CT) bands, assumed to result from inclusion of a guest molecule inside the cavity of CBPQT⁴⁺, is an emerald‐green band associated with the complexation of tetrathiafulvalene (TTF) and its derivatives. This interpretation was called into question recently in this journal based on theoretical gas‐phase calculations that reinterpreted this CT band in terms of an intermolecular side‐on interaction of TTF with one of the bipyridinium (BIPY²⁺) units of CBPQT⁴⁺, rather than the encapsulation of TTF inside the cavity of CBPQT⁴⁺. We carried out DFT calculations, including solvation, that reveal conclusively that the CT band emerging upon mixing TTF with CBPQT⁴⁺ arises from the formation of a 1:1 inclusion complex. In support of this conclusion, we have performed additional experiments on a [2]rotaxane in which a TTF unit, located in the middle of its short dumbbell, is prevented sterically from interacting with either one of the two BIPY²⁺ units of a CBPQT⁴⁺ ring residing on a separate [2]rotaxane in a side‐on fashion. This [2]rotaxane has similar UV/Vis and ¹H NMR spectroscopic properties with those of 1:1 inclusion complexes of TTF and its derivatives with CBPQT⁴⁺. The [2]rotaxane exists as an equimolar mixture of cis‐ and trans‐isomers associated with the disubstituted TTF unit in its dumbbell component. Solid‐state structures were obtained for both isomers, validating the conclusion that the TTF unit, which gives rise to the CT band, resides inside CBPQT⁴⁺.     

The role of photoionization in streamer discharge formation invoids

The crucial role of photoionization in the three-dimensional (3-D) formation of a streamer discharge in a void, filled with air, in an insulator, is demonstrated by performing calculations both with and without a 3-D treatment of photoionization. Secondary electron emission from the walls due to ion impact is found to be too slow to affect the initial streamer formation     

Using Remote Substituents to Control Solution Structure and Anion Binding in Lanthanide Complexes

A study of the anion‐binding properties of three structurally related lanthanide complexes, which all contain chemically identical anion‐binding motifs, has revealed dramatic differences in their anion affinity. These arise as a consequence of changes in the substitution pattern on the periphery of the molecule, at a substantial distance from the binding pocket. Herein, we explore these remote substituent effects and explain the observed behaviour through discussion of the way in which remote substituents can influence and control the global structure of a molecule through their demands upon conformational space. Peripheral modifications to a binuclear lanthanide motif derived from α,α′‐bis(DO3 Ayl)‐m‐xylene are shown to result in dramatic changes to the binding constant for isophthalate. In this system, the parent compound displays considerable conformational flexibility, yet can be assumed to bind to isophthalate through a well‐defined conformer. Addition of steric bulk remote from the binding site restricts conformational mobility, giving rise to an increase in binding constant on entropic grounds as long as the ideal binding conformation is not excluded from the available range of conformers.     

Aqueous solutions containing amino acids and peptides. Part 21. The enthalpic coefficients at 298.15 K for the interaction of N-acetyl-l-prolinamide with some 2-(N-acetylamino)acyl amides

Enthalpies of dilution of N-acetyl-l-prolinamide and equimolal solutions of this with N-acetylglycinamide, N-acetyl-l-alaninamide, N-acetyl-l-valinamide and N-acetyl-l-leucinamide have been determined at 298.15 K using a microcalorimetric procedure. The results obtained were used to calculate the pairwise enthalpic virial coefficients for both like—like (homotactic) and like—unlike (heterotactic) solute interactions. It is shown that the data can be predicted rather well using a group additivity approach with parameters obtained from earlier studies on α-amino and α-imino acid derivatives.