Fluorescence Detection of Adenosine Triphosphate in an Aqueous Solution Using a Combination of Copper(II) Complexes

Fluorescent ligands have been designed to form ternary complexes with a Cu(II) cation and phosphates in a buffer solution at physiological pH 7.4. It has been shown that a combination of two different ligands and CuCl(2) allows one to achieve high adenosine triphosphate/adenosine diphosphate, adenosine 5'-monophosphate selectivity, and ratiometric fluorescence sensing, while separately each ligand complex does not have such properties.     

Switchgrass PviCAD1: Understanding Residues Important for Substrate Preferences and Activity

Cinnamyl alcohol dehydrogenase (CAD) catalyzes the final step in monolignol biosynthesis. Although plants contain numerous genes coding for CADs, only one or two CADs appear to have a primary physiological role in lignin biosynthesis. Much of this distinction appears to reside in a few key residues that permit reasonable catalytic rates on monolignal substrates. Here, several mutant proteins were generated using switchgrass wild type (WT) PviCAD1 as a template to understand the role of some of these key residues, including a proton shuttling HL duo in the active site. Mutated proteins displayed lowered or limited activity on cinnamylaldehydes and exhibited altered kinetic properties compared to the WT enzyme, suggesting that key residues important for efficient catalysis had been identified. We have also shown that a sorghum ortholog containing EW, instead of HL in its active site, displayed negligible activity against monolignals. These results indicate that lignifying CADs require a specific set of key residues for efficient activity against monolignals.     

Snapshot of the palladium(II)-catalyzed oxidative biaryl bond formation by X-ray analysis of the intermediate diaryl palladium(II) complex

Pd(II) caught in the act: The diaryl Pd(II) intermediate of a Pd(II)-catalyzed oxidative biaryl bond formation proceeding via a double C-H bond activation has been isolated and fully characterized, including an X-ray crystal structure analysis. Stabilization due to chelation by adjacent pivaloyloxy and acetyl groups has allowed the isolation of this long-sought crucial intermediate. On gentle warming, the complex is transformed into a carbazole product, and the catalytically active Pd(II) species is regenerated by oxidation with Cu(II).     

Practical azidation of 1,3-dicarbonyls

An operationally simple, direct azidation of 1,3-dicarbonyl compounds has been developed. The reaction proceeds readily under ambient conditions using sodium azide and an iodine-based oxidant such as I(2) or 2-iodoxybenzoic acid (IBX)-SO(3)K/NaI. In particular, the latter method, as a new and well-balanced oxidizing agent, shows excellent functional group tolerance and substrate scope and thus allows access to a variety of tertiary 2-azido and 2,2-bisazido 1,3-dicarbonyl compounds that would be more difficult to access by using traditional methods. Because the azide-containing products easily undergo 1,3-dipolar cycloaddition with alkynes, our report represents a novel route to analogues of sensitive complex molecules.     

A new Technique for Measurement of Myocardial O2-Utilization

The coronary reserve of mammalian hearts is significantly heterogeneous. From this phenomenon we conclude on a heterogeneous energy-demand, i.e., ATP-demand and therefore on a nonuniform ischemic tolerance of cardiomyocytes.

Our aim was to establish a method for direct quantification of cardiomyocyte energy production. According to Langendorff, 10 isolated rabbit hearts were perfused with oxygen enriched Krebs-Henseleit solution. Using the stable oxygen isotope ¹⁸O₂, respiratory water of 7 hearts was labelled, and samples were taken from the coronary venous effluent. Defined cardiac tissue areas were lyophylized. Using the guanidine-hydrochloride technique, μl-water samples from the tissue and the coronary venous effluent were quantitatively converted to CO₂. With the help of mass-spectrometry the δ¹⁸O/¹⁶O-isotope ratios were determined and related to the SMOW-scale.

Compared to control hearts, a significant shift to higher SMOW-values within respiratory water from ¹⁸O-labelled hearts was detected (mean = 14.61%). Control hearts (maximal scatter = 1.42%) as well as ¹⁸O-labelled hearts (4.06%) showed high reproducibilit, of the method. With the employed experimental setup, significant regional differences were not detected. The kinetics of the coronary venous effluent showed a tendency toward saturation with H₂ ¹⁸O within 2 min after starting the ¹⁸O₂-perfusion. After 50 s perfusion increase in SMOW-values reached statistical significance.     

Modeling of material properties after ultrashort laser and XUV excitation

By means of first principles calculations, we studied the possibility of manipulating structural properties of different materials via excitation with intense femtosecond laser or extreme ultraviolet (XUV) pulses. For silicon and boron-nitride nanotubes, we performed ab initio molecular dynamics simulations using the code CHIVES, developed in our group, to describe their laser-induced structural dynamics. For both materials, we determined the damage thresholds. We also investigated the structural response of magnesium and copper to ultrashort XUV excitation. For this purpose, we performed frozen-phonon calculations based on all-electron density functional theory and allowed the possibility of core-hole excitation. We found that Cu undergoes bond hardening and Mg bond softening upon creation of core holes and hot electrons, where we defined the bond strength by the vibrational frequencies.     

Constructing exact Lagrangian immersions with few double points

We establish, as an application of the results from Eliashberg and Murphy (Lagrangian caps, 2013), an h-principle for exact Lagrangian immersions with transverse self-intersections and the minimal, or near-minimal number of double points. One corollary of our result is that any orientable closed 3-manifold admits an exact Lagrangian immersion into standard symplectic 6-space ${\mathbb{R}^6_{\rm st}}$ with exactly one transverse double point. Our construction also yields a Lagrangian embedding ${S^1 \times S^2 \to \mathbb{R}^6_{\rm st}}$ with vanishing Maslov class.     

On Euclidean Norm Balancing

We recall Euclidean norm balancing of linear time-invariant control systems and extend it to other classes of systems. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)