The Cauchy Problem for Hyperbolic Operators with Double Characteristics in Presence of Transition

We study the C ^∞ well-posedness of the Cauchy problem for a class of hyperbolic second order operators with double characteristics in presence of geometric transitions.     

Atomic‐Level Quality Assessment of Enzymes Encapsulated in Bioinspired Silica

Among protein immobilization strategies, encapsulation in bioinspired silica is increasingly popular. Encapsulation offers high yields and the solid support is created through a protein‐catalyzed polycondensation reaction that occurs under mild conditions. An integrated strategy is reported for the characterization of both the protein and bioinspired silica scaffold generated by the encapsulation of enzymes with an external silica‐forming promoter or with the promoter expressed as a fusion to the enzyme. This strategy is applied to the catalytic domain of matrix metalloproteinase 12. Analysis reveals that the structure of the protein encapsulated by either method is not significantly altered with respect to the native form. The structural features of silica obtained by either strategy are also similar, but differ from those obtained by other approaches. In case of the covalently linked R5–enzyme construct, immobilization yields are higher. Encapsulation through a fusion protein, therefore, appears to be the method of choice.     

Synthesis of 3-Acyl and 3-Carboalkoxyfurans by the Ceric Ammonium Nitrate Promoted Addition of 1,3-Dicarbonyl Compounds to Vinylic Acetates

3-Acyl- and 3-carboalkoxyfurans can be prepared in 30–55% yield by the oxidative addition of 1,3-dicarbonyl compounds to vinylic acetates induced by eerie ammonium nitrate.     

Light‐Induced Porphyrin‐Based Spectroscopic Ruler for Nanometer Distance Measurements

We present a novel pulsed electron paramagnetic resonance (EPR) spectroscopic ruler to test the performance of a recently developed spin‐labeling method based on the photoexcited triplet state (S=1). Four‐pulse electron double resonance (PELDOR) experiments are carried out on a series of helical peptides, labeled at the N‐terminal end with the porphyrin moiety, which can be excited to the triplet state, and with the nitroxide at various sequence positions, spanning distances in the range 1.8–8 nm. The PELDOR traces provide accurate distance measurements for all the ruler series, showing deep envelope modulations at frequencies varying in a progressive way according to the increasing distance between the spin labels. The upper limit is evaluated and found to be around 8 nm. The PELDOR‐derived distances are in excellent agreement with theoretical predictions. We demonstrate that high sensitivity is acquired using the triplet state as a spin label by comparison with Cu(II)–porphyrin analogues. The new labeling approach has a high potential for measuring nanometer distances in more complex biological systems due to the properties of the porphyrin triplet state.