Synthesis of fluorescent oligonucleotide--EYFP conjugate: towards supramolecular construction of semisynthetic biomolecular antennae

A novel species of DNA--protein conjugate was synthesized by chemically linking DNA oligonucleotides to Aequorea victoria green fluorescent protein mutant EYFP. An additional cysteine was added to the C-terminus of the EYFP by genetic engineering and used to covalently attach amino-modified oligonucleotide with the aid of the heterobifunctional crosslinker sSMCC. EYFP maintained its fluorescence upon conjugation. The oligonucleotide provides an additional binding site to the fluorescent protein, and hence, the EYFP conjugate could be specifically hybridized with both complementary DNA-protein conjugates in-solution as well as immobilized at capture oligonucleotides attached to a solid substrate. These studies are paving the way for future applications in the self-assembly of photoactive supramolecular complexes, such as artificial light-harvesting systems.     

Novel UDP-glycal derivatives as transition state analogue inhibitors of UDP-GlcNAc 2-epimerase

The "epimerisation" of UDP-GlcNAc to ManNAc, the first step in the biosynthesis of sialic acids, is catalyzed by UDP-GlcNAc 2-epimerase. In this paper we report the synthesis of transition state based inhibitors of this enzyme. To mimic the assumed first transition state of this reaction (TS 1), we designed and synthesized the novel UDP-exo-glycal derivatives 1-4. We also report herein the synthesis of 5 and 6, the first C-glycosidic derivatives of 2-acetamidoglucal, and the synthesis of the ketosides 7 and 8, which were designed as bis-substrate analogue and bis- product analogue, respectively, to mimic the second step of the reaction via the assumed second transition state TS 2.     

Comparison of microwave-assisted acid leaching techniques for the determination of heavy metals in sediments, soils, and sludges

Microwave-assisted EPA method 3051 for nitric acid leaching of environmentally key elements from sediments, soils, and sludges was tested, and the influence of leaching temperature and time on element recovery for an estuarine sediment (CRM 277) was investigated. The extraction efficiencies for four certified reference materials applying EPA method 3051, an optimized nitric acid procedure, and an aqua regia (HCl/HNO₃ 3:1) procedure were compared. Digestions were carried out in a high-pressure microwave system offering simultaneous temperature and pressure control for all digestion vessels employed. Eight elements (Cd, Co, Cr, Cu, Hg, Ni, Pb, and Zn) were determined by ICP-AES and ICP-MS. Extraction efficiency strongly depended on the applied leaching parameters and varied for certain elements among different materials when a nitric acid procedure was applied. In general, element recoveries obtained from the aqua regia procedure were superior to those obtained from nitric acid procedures and showed good agreement with the 95% confidence interval of the certified value for most of the elements investigated. Received: 27 March 1998 / Revised: 29 June 1998 / Accepted: 3 July 1998     

Computation of Entropy Production in Stratified Flames Based on Chemistry Tabulation and an Eulerian Transported Probability Density Function Approach

This contribution presents a straightforward strategy to investigate the entropy production in stratified premixed flames. The modeling approach is grounded on a chemistry tabulation strategy, large eddy simulation, and the Eulerian stochastic field method. This enables a combination of a detailed representation of the chemistry with an advanced model for the turbulence chemistry interaction, which is crucial to compute the various sources of exergy losses in combustion systems. First, using detailed reaction kinetic reference simulations in a simplified laminar stratified premixed flame, it is demonstrated that the tabulated chemistry is a suitable approach to compute the various sources of irreversibilities. Thereafter, the effects of the operating conditions on the entropy production are investigated. For this purpose, two operating conditions of the Darmstadt stratified burner with varying levels of shear have been considered. The investigations reveal that the contribution to the entropy production through mixing emerging from the chemical reaction is much larger than the one caused by the stratification. Moreover, it is shown that a stronger shear, realized through a larger Reynolds number, yields higher entropy production through heat, mixing and viscous dissipation and reduces the share by chemical reaction to the total entropy generated.     

Time-resolved vibrational spectroscopy

Call for papers

Time-resolved vibrational spectroscopy     

Some efficient methods for enclosing simple zeros of nonlinear equations

In the present paper we propose three new methods for computing sequences of enclosing intervals for a zero of a real function without convexity assumptions.The new methods have been tested on a series of published examples. The numerical experiments show that our methods are comparable in terms of efficiency with the well-known algorithms of Dekker and Brent.The present paper was written when this author was visiting the University of Karlsruhe. He would like to acknowledge the support provided by the University of Karlsruhe.     

Leaky helical flexural wave backscattering contributions from tilted cylindrical shells in water: observations and modeling

For tilt angles smaller than the meridional ray coupling condition previously investigated [S. F. Morse et al., J. Acoust. Soc. Am. 103, 785-794 (1998)], flexural helical waves on cylindrical shells can significantly enhance the backscattering. These contributions are compared and modeled here for an empty cylinder. Experiments using tone bursts were performed on a tilted stainless steel shell to investigate the contributions caused by flexural leaky Lamb waves above the coincidence frequency of the shell. In some of the measurements the tone bursts were of sufficient duration to superpose helical wave contributions of successive circumnavigations, along with the meridional contribution near the critical tilt, to arrive at a quasi-steady-state backscattering amplitude for the cylinder. These measurements are compared with an approximate numerical partial-wave series solution and a ray theory as a function of the tilt angle. The data for ka = 20 follow the basic shape of the ray theory and the relevant features of the partial-wave model. They illustrate the importance of the interference of successive helical wave contributions. Measurements (also as a function of the tilt angle) using tone bursts that were sufficiently short to separate the earliest helical wave contribution from later contributions also support the ray theory.     

Illuminating the BOLD signal: combined fMRI-fNIRS studies

Functional magnetic resonance imaging (fMRI) is currently combined with electrophysiological methods to identify the relationship between neuronal activity and the blood oxygenation level-dependent (BOLD) signal. Several processes like neuronal activity, synaptic activity, vascular dilation, blood volume and oxygenation changes underlie both response modalities, that is, the electrophysiological signal and the vascular response. However, accessing single process relationships is absolutely mandatory when aiming at a deeper understanding of neurovascular coupling and necessitates studies on the individual building blocks of the vascular response. Combined fMRI and functional near-infrared spectroscopy studies have been performed to validate the correlation of the BOLD signal to the hemodynamic changes in the brain. Here we review the current status of the integration of both technologies and judge these studies in the light of recent findings on neurovascular coupling.