Do cellulose binding domains increase substrate accessibility?

This article provides an overview of various theories proposed during the past five decades to describe the enzymatic hydrolysis of cellulose highlighting the major shifts that these theories have undergone. It also describes the effect of the cellulose-binding domain (CBD) of an exoglucanase/xylanase from bacterium Cellulomonas fimi on the enzymatic hydrolysis of Avicel. Pretreatment of Avicel with CBD_Cex at 4 and 37°C as well as simultaneous addition of CBD_Cex to the hydrolytic enzyme (Celluclast, Novo, Nordisk) reduced the initial rate of hydrolysis owing to irreversible binding of CBD proteins to the substrate's binding sites. Nonetheless, near complete hydrolysis was achieved even in the presence of CBD_Cex. Protease treatment of both pure and CBD_Cex-treated Avicel reduced the substrates' hydrolyzability, perhapsowing to proteolysis of the hydrolyzing enzyme (Celluclast) by the residual Proteinase K remaining in the substrate. Better protocols for comptete removal of CBD proteins from the substrate need to be developed to investigate the effect of CBD adsorption on cellulose digestibility.     

Review of Recent Zoom Lens Developments for 35 mm Cinematography at Panavision

A series of high performance zoom lens objectives developed by Panavision over fifteen years, which are very popular in the motion picture (cine) industry, are described. Various aspects of four cine zoom lenses, including; definitions, development, specification, construction, aberrations and tolerances, are discussed.This paper was originally presented at the 2nd International Conference on Optical Design and Fabrication, ODF2000 which was held on November 15-17, 2000 at the International Conference Center, Tokyo, Waseda University, Japan.     

Microporous Polymers as Potential Hydrogen Storage Materials

Microporous organic polymers offer the possibility of storing hydrogen safely at low temperatures and moderate pressures via physisorption. A range of polymers of intrinsic microporosity (PIMs) have been studied. The best PIM to date is based on a triptycene monomer and takes up 2.7% H₂ by mass at 10 bar/77 K. Hypercrosslinked polymers (HCPs) also show promising performance, particularly at pressures >10 bar. The form of the H₂ isotherm is influenced by the micropore distribution, a higher concentration of ultramicropores (pore size <0.7 nm), as found in PIMs, being associated with enhanced low pressure adsorption. The performance of polymers relative to other microporous materials (carbons and metal‐organic frameworks) is compared and promising methods to enhance the hydrogen uptake of microporous polymers are suggested.

     

Large-eddy simulation of low-frequency unsteadiness in a turbulent shock-induced separation bubble

The need for better understanding of the low-frequency unsteadiness observed in shock wave/turbulent boundary layer interactions has been driving research in this area for several decades. We present here a large-eddy simulation investigation of the interaction between an impinging oblique shock and a Mach 2.3 turbulent boundary layer. Contrary to past large-eddy simulation investigations on shock/turbulent boundary layer interactions, we have used an inflow technique which does not introduce any energetically significant low frequencies into the domain, hence avoiding possible interference with the shock/boundary layer interaction system. The large-eddy simulation has been run for much longer times than previous computational studies making a Fourier analysis of the low frequency possible. The broadband and energetic low-frequency component found in the interaction is in excellent agreement with the experimental findings. Furthermore, a linear stability analysis of the mean flow was performed and a stationary unstable global mode was found. The long-run large-eddy simulation data were analyzed and a phase change in the wall pressure fluctuations was related to the global-mode structure, leading to a possible driving mechanism for the observed low-frequency motions.      

Synthesis and structure elucidation of a series of pyranochromene chalcones and flavanones using 1D and 2D NMR spectroscopy and X‐ray crystallography

A series of novel pyranochromene chalcones and corresponding flavanones were synthesized. This is the first report on the confirmation of the absolute configuration of chromene‐based flavanones using X‐ray crystallography. These compounds were characterized by 2D NMR spectroscopy, and their assignments are reported herein. The 3D structure of the chalcone 3b and flavanone 4g was determined by X‐ray crystallography, and the structure of the flavanone was confirmed to be in the S configuration at C‐2. Copyright © 2014 John Wiley & Sons, Ltd.     

Bi2O3 Nanoparticle Clusters: Reversible Agglomeration Revealed by Imaging and Nano‐Impact Experiments

Colloidal suspensions of Bi₂O₃ nanoparticles were studied in aqueous solution using imaging and electrochemical techniques. Nanoparticle tracking analysis revealed the particles to be agglomerated. In contrast, electrochemical detection via the nano‐impacts technique showed almost exclusive detection of monomeric nanoparticles. Comparison of the two techniques allows the conclusion to be drawn that the agglomeration/deagglomeration of the nanoparticles is reversible. A minimum rate constant for the deagglomeration process was estimated.     

A Diels-Alder Reaction Conducted Within the Parameters of Aqueous Organocatalysis: Still Just Smoke and Mirrors

Conducting reactions using water as solvent is a highly prized goal for the organic chemist. Based upon recent literature and our continuing interest in the field of aqueous organocatalysis, we tested the scope of an enamine based Diels-Alder reaction using (±)-nornicotine, proline, and a proline derivative as aqueous organocatalysts. Unfortunately, none of the examined catalysts under aqueous conditions proved useful, leaving the aqueous Diels-Alder reaction as an elusive goal.     

Connecting T-duality invariant theories

We show that the vanishing of the one-loop beta-functional of the doubled formalism (which describes string theory on a torus fibration in which the fibres are doubled) is the same as the equation of motion of the recently proposed generalised metric formulation of double field theory restricted to this background: both are the vanishing of a generalised Ricci tensor. That this tensor arises in both backgrounds indicates the importance of a new doubled differential geometry for understanding both constructions.     

On the substitution rule for Lebesgue–Stieltjes integrals

We show how two change-of-variables formulæ for Lebesgue–Stieltjes integrals generalize when all continuity hypotheses on the integrators are dropped. We find that a sort of “mass splitting phenomenon” arises.