Mechanochemical synthesis of an elusive fluorinated polyacetylene.

Polymer mechanochemistry has traditionally been employed to study the effects of mechanical force on chemical bonds within a polymer backbone or to generate force-responsive materials. It is under-exploited for the scalable synthesis of wholly new materials by chemically transforming the polymers, especially products inaccessible by other means. Here we utilize polymer mechanochemistry to synthesize a fluorinated polyacetylene, a long-sought-after air-stable polyacetylene that has eluded synthesis by conventional means.

Carbon compositional analysis of hydrogel contact lenses by solid-state NMR spectroscopy.

Contact lenses are worn by over 140 million people each year and tremendous research and development efforts contribute to the identification and selection of hydrogel components and production protocols to yield lenses optimized for chemical and physiological properties, eye health and comfort. The final molecular composition and extent of incorporation of different components in contact lenses is routinely estimated after lens production through the analysis of the soluble components that were not included in the lens, i.e.

Benzoladderene Mechanophores: Synthesis, Polymerization, and Mechanochemical Transformation.

We have previously reported a polymechanophore system, polyladderene, which underwent dramatic bond rearrangement in response to mechanical force to yield semiconducting polyacetylene. Herein, we report the scalable synthesis of benzoladderenes as new mechanophore monomers. Ring-opening metathesis polymerization of benzoladderenes yielded homopolymers and block copolymers with controlled molecular weights and low dispersity.

Synthesis and Mechanochemical Activation of Ladderene-Norbornene Block Copolymers.

We have recently reported a polymechanophore system, polyladderene (PLDE), which dramatically transforms into polyacetylene (PA) upon mechanical stimulation. Herein, we optimized conditions to synthesize unprecedented block copolymers (BCPs) containing a force-responsive block by sequential ring-opening metathesis polymerization of different norbornenes and bromoladderene. Successful extension from PLDE to other blocks required careful timing and low temperatures to preserve the reactivity of the PLDE-appended catalyst.

Peptidoglycan and Teichoic Acid Levels and Alterations in Staphylococcus aureus by Cell-Wall and Whole-Cell Nuclear Magnetic Resonance.

Gram-positive bacteria surround themselves with a multilayered macromolecular cell wall that is essential to cell survival and serves as a major target for antibiotics. The cell wall of Staphylococcus aureus is composed of two major structural components, peptidoglycan (PG) and wall teichoic acid (WTA), together creating a heterogeneous and insoluble matrix that poses a challenge to quantitative compositional analysis. Here, we present C cross polarization magic angle spinning solid-state nuclear magnetic resonance (NMR) spectra of intact cell walls, purified PG, and purified WTA.

Whole Ribosome NMR: Dipolar Couplings and Contributions to Whole Cells.

Solid-state NMR is a powerful tool for quantifying chemical composition and structure in complex assemblies and even whole cells. We employed N{P} REDOR NMR to obtain atomic-level distance propensities in intact N-labeled E. coli ribosomes.

Mechanochemical unzipping of insulating polyladderene to semiconducting polyacetylene.

Biological systems sense and respond to mechanical stimuli in a complex manner. In an effort to develop synthetic materials that transduce mechanical force into multifold changes in their intrinsic properties, we report on a mechanochemically responsive nonconjugated polymer that converts to a conjugated polymer via an extensive rearrangement of the macromolecular structure in response to force. Our design is based on the facile mechanochemical unzipping of polyladderene, a polymer inspired by a lipid natural product structure and prepared via direct metathesis polymerization.

Frequency-selective REDOR and spin-diffusion relays in uniformly labeled whole cells.

Solid-state NMR is a powerful and non-perturbative method to measure and define chemical composition and architecture in bacterial cell walls, even in the context of whole cells. Most NMR studies on whole cells have used selectively labeled samples. Here, we introduce an NMR sequence relay using frequency-selective REDOR (fsREDOR) and spin diffusion elements to probe a unique amine contribution in uniformly (13)C- and (15)N-labeled Staphylococcus aureus whole cells that we attribute to the d-alanine of teichoic acid.

Bacterial cell wall composition and the influence of antibiotics by cell-wall and whole-cell NMR.

The ability to characterize bacterial cell-wall composition and structure is crucial to understanding the function of the bacterial cell wall, determining drug modes of action and developing new-generation therapeutics. Solid-state NMR has emerged as a powerful tool to quantify chemical composition and to map cell-wall architecture in bacteria and plants, even in the context of unperturbed intact whole cells. In this review, we discuss solid-state NMR approaches to define peptidoglycan composition and to characterize the modes of action of old and new antibiotics, focusing on examples in Staphylococcus aureus.

Spectral snapshots of bacterial cell-wall composition and the influence of antibiotics by whole-cell NMR.

Gram-positive bacteria surround themselves with a thick cell wall that is essential to cell survival and is a major target of antibiotics. Quantifying alterations in cell-wall composition are crucial to evaluating drug modes of action, particularly important for human pathogens that are now resistant to multiple antibiotics such as Staphylococcus aureus. Macromolecular and whole-cell NMR spectroscopy allowed us to observe the full panel of carbon and nitrogen pools in S.

Uniform amplification of phage display libraries in monodisperse emulsions.

In this paper, we describe a complete experimental setup for the uniform amplification of libraries of phage. Uniform amplification, which multiplies every phage clone by the same amount irrespective of the growth rate of the clone is essential for phage-display screening. Amplification of phage libraries in a common solution is often non-uniform: it favors fast-growing clones and eliminates those that grow slower.