Mechanistic Insight into the Enzymatic Reduction of Truncated Hemoglobin N of Mycobacterium tuberculosis: role of the CD loop and pre-A Motif in electron cycling

Background: The HbN of Mycobacterium tuberculosis carries a potent nitric-oxide dioxygenase activity despite lacking a reductase domain. Results: The NADH-ferredoxin reductase system acts as an efficient partner for the reduction of HbN. Conclusion: The interactions of HbN with the reductase are modulated by its CD loop and the Pre-A region. Significance: The present study provides new insights into the mechanism of electron transfer during nitric oxide detoxification by HbN.Fil: Singh, Sandeep. Institute of Microbial Technology; IndiaFil: Thakur, Naveen. Institute of Microbial Technology; IndiaFil: Oliveira, Ana. Universidad de Barcelona; EspañaFil: Petruk, Ariel Alcides. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Hade, Mangesh Dattu. Institute of Microbial Technology; IndiaFil: Sethi, Deepti. Institute of Microbial Technology; IndiaFil: Bidon Chanal, Axel. Universidad de Barcelona; EspañaFil: Marti, Marcelo Adrian. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Datta, H.. Institute of Microbial Technology; IndiaFil: Parkesh, R.. Institute of Microbial Technology; IndiaFil: Estrin, Dario Ariel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Luque, F. Javier. Universidad de Barcelona; EspañaFil: Dikshit, Kanak L.. Institute of Microbial Technology; Indi

Selective fluorescent chemosensors and iodinated contrast agents : biological evaluation for cellular zinc detection, microdamage detection and imaging

THESIS 7554This thesis entitled "Selective Fluorescent Chemosensors and lodinated Contrast Agents: Biological Evaluation for Cellular Zinc detection, Microdamage Detection and Imaging" has been divided into six Chapters. Chapter 1 highlights advances made in the field of fluorescent chemosensors. Examples discussed have been critically evaluated in terms of their photophysical properties, selectivity, sensitivity and binding ability. To introduce the relevance of supramolecular systems for microdamage detection in bone, a brief introduction to the characteristics of bone and X-rays are also provided. Chapter 2 presents in detail the design, synthesis and photophysical evaluation of two water soluble and selective Zn(II) fluoroprobes 92 and 93. The key feature of these sensors is their stability under simulated physiological conditions. The fluorescence titrations of 92 demonstrated its ability to detect nanomolar free Zn(II). Preliminarily studies carried out using pancreatic tissue have shown the ability of 92 to label the areas, which contain chelatable zinc. Chapter 3 presents in details two aqueous soluble, anthracene based fluorescent PET sensors 125 and 126 for selective recognition of Zn(II) and Cd(II). The evaluation of the photophysical response o f these sensors demonstrated their ability to distinguish between Zn(II) and Cd(II). Chapter 4 details a critical investigation of microdamage in bone using histological methods, SEM and EDXA. A set of fluoroprobes, 135, 136, 138, 140, 141, 142, 143, 92, 93 and 125 were used to investigate the selective labelling of the microcrack in the bone. The scratched and unscratched surfaces of the bone were studied using Raman spectroscopy, SEM and EDXA. The selective labelling of scratches observed can be attributed to the interaction of dyes via binding at the free lattice sites, ionic interactions with the free lattice sites or incorporation in the broken lattice sites

Luminescent sensing

The development of luminescent sensing has been central to the field of supramolecular chemistry. Herein, we give a some insight into some of the developments that have taken place in recent times, focusing most of our effort on the discussion of luminescent sensors for cations, anions, and neutral molecules, by presenting a selected number of examples from this fast, broad, and ever expanding research field. We also demonstrate how the use of luminescent sensors has helped in the development of contrast and imaging agents, and in particular show examples of their use in cellular imaging and sensing within competitive biological environments

Chemo-enzymatic synthesis and biological evaluation of photolabile nicotinic acid adenine dinuclotide phosphate (NAADP+).

A chemo-enzymatic synthesis of novel caged NAADP+ without the formation of multiple cage compounds has been achieved. The biological activity of the caged NAADP+ was demonstrated by its fast uncaging in intact sea-urchin eggs

NAADP-mediated channel 'chatter' in neurons of the rat medulla oblongata.

NAADP (nicotinic acid-adenine dinucleotide phosphate) is a potent Ca(2+)-mobilizing messenger that stimulates Ca(2+) release in a variety of cells. NAADP-sensitive Ca(2+) channels are thought to reside on acidic Ca(2+) stores and to be functionally coupled to IP(3) (inositol 1,4,5-trisphosphate) and/or ryanodine receptors located on the endoplasmic reticulum. Whether NAADP-sensitive Ca(2+) channels 'chatter' to other channels, however, is not clear. In the present study, we have used a cell-permeant NAADP analogue to probe NAADP-mediated responses in rat medulla oblongata neurons. NAADP-AM (NAADP-acetoxymethyl ester) evoked global cytosolic Ca(2+) signals in isolated neurons that were reduced in amplitude by removal of external Ca(2+), abolished by disruption of acidic compartments and substantially inhibited by blockade of ryanodine receptors. In rat medullary slices, NAADP-AM depolarized neurons from the nucleus ambiguus in the presence of intracellular EGTA, but not of the faster Ca(2+) chelator BAPTA [1,2-bis-(o-aminophenoxy)ethane-N,N,N',N'-tetra-acetic acid]. Depolarization was also dependent upon extracellular Ca(2+), acidic stores and ryanodine receptors. In voltage-clamp mode, NAADP-AM induced an inward current with a reversal potential of approx. 0 mV. The results of the present study reveal the presence of acidic NAADP-sensitive Ca(2+) stores in medulla neurons, the mobilization of which results not only in global Ca(2+) signals but also in local signals that activate non-selective cation channels on the cell surface resulting in depolarization. Thus NAADP is capable of co-ordinating channels both within the cell interior and at the cell membrane representing a novel mechanism for excitation of central neurons

DprE1-DprE2 interaction analysis.

<p>(a) The stereo view of the binding surface of the complex where DprE1 and DprE2 are represented by red and green respectively. (b) Cartoon representation of the complex showing interface residues involved in H-bonding where grey and green represents carbon atoms of DprE1 and DprE2 respectively. Oxygen ayoms are coloured red whereas nitrogen atoms are blue. The dashed line represents the H-bond network between residues of DprE1 and DprE2.</p