54 research outputs found
Hyperbasism
No full textHiten Shelar is an Astrophysicist and Bestselling Astrophysics Author behind Astrophysics for Non-mathematicians, Cosmology for a newbie, Astrophysics for everyone and other bestselling physics books
Crystals the Magic of Life in Different Forms
No full textPharmacognosyThe Image of Research 2010FinalistStructural characterization of macromolecules is often performed by x-ray crystallography. In the x-ray crystallography techniques, the first (and often most difficult) step is to obtain adequate crystals. In this image I have captured four different crystals of the same protein that were crystallized under different conditions. These crystals were grown following standard crystallization technique with hanging drop vapor diffusion, and the images were captured on an inverted microscope
Crystals the Magic of Life in Different Forms
No full textStructural characterization of macromolecules is often performed by x-ray crystallography. In the x-ray crystallography techniques, the first (and often most difficult) step is to obtain adequate crystals. In this image I have captured four different crystals of the same protein that were crystallized under different conditions. These crystals were grown following standard crystallization technique with hanging drop vapor diffusion, and the images were captured on an inverted microscope
Current Trends and Advances in Bulk Crystallization and Freeze-Drying of Biopharmaceuticals
No full textCase Studies and Examples of Biopharmaceutical Modalities Processed by Bulk Crystallization or Bulk Freeze-Drying
No full textGenetic Essentiality, Biochemical and Structural Properties of Fructose 1,6-bisphosphatases II
No full textThe genetic essentiality of the glpX gene in Mycobacterium tuberculosis (Mtb) was investigated by generating an unmarked deletion mutant. This mutant was characterized by its phenotype, including growth on selective media, and its in vivo survival profile in a mouse model. The glpX gene was required for eugonic growth on gluconeogenic substrates such as glycerol, acetate, and oleic acid. Mtb lacking the glpX gene not only failed to maintain the initial inoculum density(100 counts), but also failed to replicate and survive in mouse lungs (3 log difference in bacterial count compared to the wild type strain of Mtb) during the acute phase of infection. The absence of glpX in the chronic phase of infection resulted in significant mycobacterial clearance. The glpX gene encoded a functional fructose 1,6–bisphosphatase which was successfully purified using affinity capture and size exclusion chromatography. Biochemical characterization, including determination of optimal conditions for enzymatic activity was performed. Mtb FBPase belongs to the super family of lithium sensitive phosphatases which require bivalent metal ions for enzymatic activity. The crystal structures of FBPase and its complex with catalytic product fructose 6-phosphate, were solved by a standard molecular replacement method. Mtb FBPase II exists as a functional tetramer with no allosteric regulatory mechanism as compared to the classical FBPase I present in mammals and several other bacteria. The active site of Mtb FBPase is highly conserved and 100% similar to other known FBPase II enzymes, indicative of a common catalytic mechanism.
The FBPase activity of the glpX-encoded protein in Francisella tularensis was confirmed. Furthermore, the protein was purified to homogeneity and crystallized following similar methods used for Mtb FBPase. Two major bottlenecks (i.e. purification and crystallization of the protein target) in the process of structure based drug discovery (SBDD) for an already validated target were overcome.
The interdisciplinary studies performed herein validate FBPase II as a drug target in pathogenic bacteria and provide critical information for SBDD
A two-step strategy for the complementation of M: tuberculosis mutants
No full textThe sequence of Mycobacterium tuberculosis, completed in 1998, facilitated both the development of genomic tools, and the creation of a number of mycobacterial mutants. These mutants have a wide range of phenotypes, from attenuated to hypervirulent strains. These phenotypes must be confirmed, to rule out possible secondary mutations that may arise during the generation of mutant strains. This may occur during the amplification of target genes or during the generation of the mutation, thus constructing a complementation strain, which expresses the wild-type copy of the gene in the mutant strain, becomes necessary. In this study we have introduced a two-step strategy to construct complementation strains using the Ag85 promoter. We have constitutively expressed dosR and have shown dosR expression is restored to wild-type level
An engine air-brake integration study
No full textThesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2011.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student submitted PDF version of thesis.Includes bibliographical references (p. 109-112).The feasibility of operating an engine air-brake (EAB) integrated with a pylon duct bifurcation in a realistic aircraft engine environment has been analyzed. The EAB uses variable exit guide vanes downstream of a high bypass ratio (BPR) fan rotor to produce drag quietly by swirling flow out of the fan nozzle. The swirling motion yields low pressure in the vortex core from simple radial equilibrium, thereby generating pressure drag. The 4-BB internal plug and 5-BB external plug nozzles of BPR 8 are chosen to provide a realistic environment for model-scale tests at the NASA Aero-Acoustic Propulsion Lab (AAPL). The objectives of this study are to quantify the impact of a pylon on the drag and noise of an EAB, and explore means to mitigate the potential loss of swirling flow and associated drag. Analysis is conducted at approach conditions on the 4-BB nozzle, with fan and core nozzle pressure and temperature ratios obtained from an engine cycle analysis. A pylon is designed to represent engine installations typically encountered in short-range jet aircraft. The pylon is a prismatic NACA 0012 airfoil geometry with swept leading, trailing edges and an extended internal fairing to facilitate compatibility with both nozzles in the AAPL facility. The EAB cases analyzed include three types of pylon/vane configurations: (1) the baseline pylon with un-deflected swirl vanes is used in the calculation of the equivalent drag coefficient (CD); (2) the pylon with the trailing edge (TE) flap deflected full-span by 35 degrees is used to set structural load limits for detailed design of the baseline pylon; and (3) configurations with the pylon TE flap deflected partial-span by 20 degrees and asymmetric swirl vanes are used to generate swirling outflow from the fan nozzle exhaust. The partial-span deflection cases are further categorized by the location of the asymmetric vanes: at the nozzle exhaust (aft) and further upstream. Computational results demonstrate the aft vanes generate CD in the range 0.35-0.61 and the upstream vane cases produce CD between 0.09-0.18. The difference in drag is because the flow avoids the majority of the duct bifurcation in the aft vanes cases to produce stronger swirling outflow. A CD value between 0.7-1.0 is required to achieve a 3-4 degree glidescope change and therefore an overall noise benefit of 2.5 dB for a conventional tube-and-wing aircraft on approach. The aft vane configurations show promise in reaching this target while the upstream vane installation concepts require further investigation.by Hiten Mulchandani.S.M
Structures of the<i>Mycobacterium tuberculosis</i>GlpX protein (class II fructose-1,6-bisphosphatase): implications for the active oligomeric state, catalytic mechanism and citrate inhibition
No full textThe crystal structures of native class II fructose-1,6-bisphosphatase (FBPaseII) fromMycobacterium tuberculosisat 2.6 Å resolution and two active-site protein variants are presented. The variants were complexed with the reaction product fructose 6-phosphate (F6P). The Thr84Ala mutant is inactive, while the Thr84Ser mutant has a lower catalytic activity. The structures reveal the presence of a 222 tetramer, similar to those described for fructose-1,6/sedoheptulose-1,7-bisphosphatase fromSynechocystis(strain 6803) as well as the equivalent enzyme fromThermosynechococcus elongatus. This homotetramer corresponds to a homologous oligomer that is present but not described in the crystal structure of FBPaseII fromEscherichia coliand is probably conserved in all FBPaseIIs. The constellation of amino-acid residues in the active site of FBPaseII fromM. tuberculosis(MtFBPaseII) is conserved and is analogous to that described previously for theE. colienzyme. Moreover, the structure of the active site of the partially active (Thr84Ser) variant and the analysis of the kinetics are consistent with the previously proposed catalytic mechanism. The presence of metabolites in the crystallization medium (for example citrate and malonate) and in the corresponding crystal structures ofMtFBPaseII, combined with their observed inhibitory effect, could suggest the existence of an uncharacterized inhibition of this class of enzymes besides the allosteric inhibition by adenosine monophosphate observed for theSynechocystisenzyme. The structural and functional insights derived from the structure ofMtFBPaseII will provide critical information for the design of lead inhibitors, which will be used to validate this target for future chemical intervention.</jats:p
In vitro growth profile of <i>ΔglpX</i>, WT <i>Mtb</i> and <i>glpX</i> complement on defined (or individual) carbon source(s).
No full text<p>Growth profile in 7H9 medium a) 0.2% glycerol, b) 0.2% Acetate, and c) 0.2% dextrose. Growth profiles are representative of a triplicate data set.</p
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