Synthesis and single enzyme activity of a clicked lipase–BSA hetero-dimer

Two-dimensional reaction free energy surfaces of catalytic reaction: effects of protein conformational dynamics on enzyme catalysis

We introduce a two-dimensional (2D) multisurface reaction free energy description of the catalytic cycle that explicitly connects the recently observed multi-time-scale conformational dynamics as well as dispersed enzymatic kinetics to the classical Michaelis-Menten equation. A slow conformational motion on a collective enzyme coordinate Q facilitates the catalytic reaction along the intrinsic reaction coordinate X, providing a dynamic realization of Pauling's well-known idea of transition-state stabilization. The catalytic cycle is modeled as transitions between multiple displaced harmonic wells in the XQ space representing different states of the cycle, which is constructed according to the free energy driving force of the cycle. Subsequent to substrate association with the enzyme, the enzyme-substrate complex under strain exhibits a nonequilibrium relaxation toward a new conformation that lowers the activation energy of the reaction, as first proposed by Haldane. The chemical reaction in X is thus enslaved to the down hill slow motion on the Q surface. One consequence of the present theory is that, in spite of the existence of dispersive kinetics, the Michaelis-Menten expression of the catalysis rate remains valid under certain conditions, as observed in recent single-molecule experiments. This dynamic theory builds the relationship between the protein conformational dynamics and the enzymatic reaction kinetics and offers a unified description of enzyme fluctuation-assisted catalysis.

Synthesis of azide/alkyne-terminal polymers and application for surface functionalisation through a [2 + 3] Huisgen cycloaddition process, "click chemistry"

Living radical polymerization of methyl methacrylate (MMA) and a fluorescent comonomer with 2-bromo-2-methylpropionic acid 3-azidopropyl ester and 2-bromo-2-methylhept-6-yn-3-one as initiators has been successfully employed for the synthesis of fluorescently tagged azide and alkyne terminated PMMA with close to that predicted, PDI < 1.20, and good first order kinetics as expected for a living polymerisation. Cotton and organic resin surfaces have been functionalised with alkyne groups using a condensation with 4-chlorocarbonylbutyric acid prop-2-ynyl ester. The surfaces have been further modified using a Huisgen [2 + 3] cycloaddition ("click") reaction of polymeric and small molecule azides. Different functional azides, mono azido-PEG and a new fluorescent hostasol derivative have been prepared and tested as model substrates for cotton surface modification. FTIR, tensiometry, FE-SEM and confocal spectroscopy have been used to characterize the modified surfaces. Tensiometry shows an increase in the hydrophobicity of the surface; verified by FE-SEM which shows a change in surface morphology. The use of the fluorescence label allows fluorescent and confocal microscopy to demonstrate the surface reactions. This approach is shown to be very general allowing soft and hard surfaces with different geometries to be modified. In particular it is an excellent method to alter the nature of organic resins allowing the incorporation of many different functionalities.

Well-defined protein–polymer conjugates—synthesis and potential applications

During the last decades, numerous studies have focused on combining the unique catalytic/functional properties and structural characteristics of proteins and enzymes with those of synthetic molecules and macromolecules. The aim of such multidisciplinary studies is to improve the properties of the natural component, combine them with those of the synthetic, and create novel biomaterials in the nanometer scale. The specific coupling of polymers onto the protein structures has proved to be one of the most straightforward and applicable approaches in that sense. In this article, we focus on the synthetic pathways that have or can be utilized to specifically couple proteins to polymers. The different categories of well-defined protein-polymer conjugates and the effect of the polymer on the protein function are discussed. Studies have shown that the specific conjugation of a synthetic polymer to a protein conveys its physico-chemical properties and, therefore, modifies the biodistribution and solubility of the protein, making it in certain cases soluble and active in organic solvents. An overview of the applications derived from such bioconjugates in the pharmaceutical industry, biocatalysis, and supramolecular nanobiotechnology is presented at the final part of the article.

Click chemistry: a new facile and efficient strategy for preparation of functionalized HPLC packings

Click chemistry has been successfully extended into the field of preparation of functionalized HPLC packings, proving a novel facile and efficient strategy for covalently bonding stationary phases onto HPLC grade silica beads; the potential has been demonstrated by the preparation of "Click I-IV" columns and preliminary results in the separation of sugars.