A critical comparison of approximation methods and models for equilibrium properties of low-barrier hydrogen bonds

Recent experimental evidence has led to the conclusion that short, strong hydrogen bonds can stabilize transition states of enzyme catalyzed biochemical reactions. Evidence for such hydrogen bonds is the low value of the isotopic fractionation factor, phi, which is defined as the equilibrium constant for the generic reaction, R-H + DOH <--> R-D + HOH, where H is the hydrogen atom participating in the low-barrier hydrogen bond in a molecule R-H. In this work we assess two approximation methods for computing the isotopic fractionation factors for single and multidimensional systems containing a low-barrier hydrogen bond. These methods are WKB and an approach that corrects the classical partition function via a quantum correction factor. We find that the latter approach is universally accurate and applicable in both single and multidimensional systems containing a low-barrier hydrogen bond. We also assess two different models for the coupling of a molecule's low-barrier hydrogen bond to other degrees of freedom, both internal and external to the molecule, and show that each leads to a lowering of the fractionation factor.     

High performance liquid chromatography assay for alanine amino transferase

Summary An improved method of alanine-amino transferase determination is proposed. The reaction is carried out with alanine and 2-oxoglutarate as substrates and analysis is by HPLC on a reversed-phase chromatographic system using a C₁₈ column and tetrabutylammonium phosphate in phosphate buffer (pH 7.0)-acetonitrile as mobile phase. The enzyme activity was determined by directly following the formation of pyruvic acid without employing any secondary reaction, which is necessary in the spectrophotometric method. The detection limit of pyruvic acid is 10 pmole l^–1 and the standard deviation for the enzymatic activity of standard solutions is 5.4%. Furthermore under the chromatographic conditions selected it is possible to detect the presence of some intermediate species.Work supported by National Research Council of Italy. Presented in part at the First International Symposium on Applications of HPLC in Enzyme Chemistry, Verona, September 1990.     

New Promising Therapeutic Avenues of Curcumin in Brain Diseases

Curcumin, the dietary polyphenol isolated from Curcuma longa (turmeric), is commonly used as an herb and spice worldwide. Because of its bio-pharmacological effects curcumin is also called “spice of life”, in fact it is recognized that curcumin possesses important proprieties such as anti-oxidant, anti-inflammatory, anti-microbial, antiproliferative, anti-tumoral, and anti-aging. Neurodegenerative diseases such as Alzheimer’s Diseases, Parkinson’s Diseases, and Multiple Sclerosis are a group of diseases characterized by a progressive loss of brain structure and function due to neuronal death; at present there is no effective treatment to cure these diseases. The protective effect of curcumin against some neurodegenerative diseases has been proven by in vivo and in vitro studies. The current review highlights the latest findings on the neuroprotective effects of curcumin, its bioavailability, its mechanism of action and its possible application for the prevention or treatment of neurodegenerative disorders.     

Monitoring and Quantifying the Passive Transport of Molecules Through Patch–Clamp Suspended Real and Model Cell Membranes

Transport of active molecules across biological membranes is a central issue for the success of many pharmaceutical strategies. Herein, we combine the patch–clamp principle with amperometric detection for monitoring fluxes of redox‐tagged molecular species across a suspended membrane patched from a macrophage. Solvent‐ and protein‐free lipid bilayers (DPhPC, DOPC, DOPG) patched from single‐wall GUV have been thoroughly investigated and the corresponding fluxes measurements quantified. The quality of the patches and their proper sealing were successfully characterized by electrochemical impedance spectroscopy. This procedure appears versatile and perfectly adequate to allow the investigation of transport and quantification of the transport properties through direct measurement of the coefficients of partition and diffusion of the compound in the membrane, thus offering insight on such important biological and pharmacological issues.     

Correspondence between generalized binomial field states and coherent atomic states

We show that the N-photon generalized binomial states of electromagnetic field may be put in a bijective mapping with the coherent atomic states of N two-level atoms. We exploit this correspondence to simply obtain both known and new properties of the N-photon generalized binomial states. In particular, an over-complete basis of these binomial states and an orthonormal basis are obtained. Finally, the squeezing properties of generalized binomial state are analyzed.     

New far infrared laser lines from 13CH2F2 and frequency measurements

We report new FIR laser lines from ¹³CH₂F₂ molecules optically pumped by a waveguide CO₂ laser. The increased tunability (300 MHz) with respect to a conventional CO₂ laser allows the pumping of ¹³CH₂F₂ vibrational transitions of large offset. 34 new laser lines have been discovered, ranging from 113.1 m to 491.4 m in wavelength, thus increasing the number of known FIR laser lines from this important molecule to 99. For all the new lines and many (36) of those known previously, precise offset measurements through the transferred Lamb-dip technique were performed. The frequency of six new laser lines was also directly measured by heterodyne detection with known laser lines.     

Entangling two uncoupled flux qubits via their sequential interaction with a quantized electromagnetic field

A theoretical scheme for the generation of maximally entangled states of two superconducting flux qubits via their sequential interaction with a monochromatic quantum field is presented. The coupling of the qubits with the quantized field can be tuned on and off resonance by modulating the effective Josephson energy of each qubit via an externally applied magnetic flux. The system operates in such a way as to transfer the entanglement from a bipartite field-qubit subsystem to the two qubits. This scheme is attractive in view of the implementation of practical quantum processing systems.     

A Particle Filtering Approach for Tracking an Unknown Number of Objects with Dynamic Relations

In recent years there has been a growing interest on particle filters for solving tracking problems, thanks to their applicability to problems with continuous, non-linear and non-Gaussian state spaces, which makes them more suited than hidden Markov models, Kalman filters and their derivations, in many real world tasks. Applications include video surveillance, sensor fusion, tracking positions and behaviors of moving objects, situation assessment in civil and bellic scenarios, econometric and clinical data series analysis. In many environments it is possible to recognize classes of similar entities, like pedestrians or vehicles in a video surveillance system, or commodities in econometric. In this paper, a relational particle filter for tracking an unknown number of objects is presented which exploits possible interactions between objects to improve the quality of filtering. We will see that taking into account relations between objects will ease the tracking of objects in presence of occlusions and discontinuities in object dynamics. Experimental results on a benchmark data set are presented.     

Stable isotope ratio analysis as a tool to discriminate between rainbow trout (O. mykiss) fed diets based on plant or fish-meal proteins

The use of stable isotope ratio analysis (SIRA) as a rapid analytical tool to characterize and discriminate farmed fish on the basis of the feedstuffs included in the diet formulation is discussed. Two isoproteic (44.8%) and isolipidic (19.6%) extruded diets were formulated: a fish-meal-based diet (FM diet), containing fish meal as the sole protein source; a plant-protein-based diet (PP diet), where pea protein concentrate and wheat gluten meal replaced 80% of fish meal protein. The diets were fed to eight groups of rainbow trout (initial body weight: 106.6g) for 103 days in two daily meals under controlled rearing conditions. Growth performance (final body weight: 318.5 g; specific growth rate: 1.06%) and feed-to-gain ratio (0.79) were not affected by the dietary treatment. The differences in isotopic values of the two diets were clearly reflected in the different carbon and nitrogen isotopic values in rainbow trout fillets. The delta(13)C and delta(15)N values of muscle of farmed rainbow trout showed differences between farmed fish fed a fish-protein-based diet (-20.47 +/- 0.34 and 12.38 +/- 0.57 for delta(13)C and delta(15)N, respectively) and those fed a plant-protein-based diet (-23.96 +/- 0.38 and 7.15 +/- 0.51 for delta(13)C and delta(15)N, respectively). The results suggest that SIRA provides a robust and verifiable analytical tool to discriminate between fish fed on a plant or a fish protein diet.