Indian Institute of Technology Guwahati

About: Indian Institute of Technology Guwahati is a education organization based out in Guwahati, Assam, India. It is known for research contribution in the topics: Adsorption & Catalysis. The organization has 6933 authors who have published 17102 publications receiving 257351 citations.

Effect of crowding by dextrans and Ficolls on the rate of alkaline phosphatase-catalyzed hydrolysis: a size-dependent investigation.

Abstract: The cell cytosol is crowded with macromolecules such as proteins, nucleic acids, and membranes. The consequences of such crowding remain unclear. How is the rate of a typical enzy- matic reaction, involving a freely diffusing enzyme and substrate, affected by the presence of macro- molecules of different sizes, shapes, and concentrations? Here, we mimic the cytosolic crowding in vitro, using dextrans and Ficolls, for the first time in a variety of sizes ranging from 15 to 500 kDa, in a concentration range 0-30% w/w. Alkaline phosphatase-catalyzed hydrolysis of p-nitrophenyl phosphate (PNPP) was chosen as the model reaction. A pronounced decrease in the rate with increase in fractional volume occupancy of dextran is observed for larger dextrans (200 and 500 kDa) in contrast to smaller dextrans (15-70 kDa). Our results indicate that, at 20% w/w, smaller dextrans (15-70 kDa) reduce the initial rate moderately (1.4- to 2.4-fold slowing), while larger dextrans (>200 kDa) slow the reaction considerably (>5-fold). Ficolls (70 and 400 kDa) slow the reaction moderately (1.3- to 2.3-fold). The influence of smaller dextrans was accounted by a combination of increase in viscosity as sensed by PNPP and a minor offsetting increase in enzyme activity due to crowding. Larger dextrans apparently reduce the frequency of enzyme substrate en- counter. The reduced influence of Ficolls is attributed to their compact and quasispherical shape, much unlike the dextrans. # 2006 Wiley Periodicals, Inc. Biopolymers 83: 477-486, 2006 This article was originally published online as an accepted preprint. The ''Published Online'' date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com

Outage Probability Analysis of IRS-Assisted Systems Under Spatially Correlated Channels

Abstract: This letter investigates the impact of spatial channel correlation on the outage probability of intelligent reflecting surface (IRS)-assisted single-input single-output (SISO) communication systems. In particular, we derive a novel closed-form expression of the outage probability for arbitrary phase shifts and correlation matrices of the indirect channels. To shed light on the impact of the spatial correlation, we further attain the closed-form expressions for two common scenarios met in the literature when the large-scale fading coefficients are expressed by the loss over a propagation distance. Numerical results validate the tightness and effectiveness of the closed-form expressions. Furthermore, the spatial correlation offers significant decreases in the outage probability as the direct channel is blocked.

Study of X(3915)→J/ψω in two-photon collisions

Abstract: We study the process $\gamma \gamma \to J/\psi \omega$ using a data sample of 519.2 $fb^{-1}$ recorded by the BaBar detector at SLAC at the PEP-II asymmetric-energy $e^+ e^-$ collider at center-of-mass energies near the $\Upsilon(nS)$ ($n = 2,3,4$) resonances. We confirm the existence of the charmonium-like resonance X(3915) decaying to $J/\psi \omega$ with a significance of 7.6 standard deviations, including systematic uncertainties, and measure its mass $(3919.4 \pm 2.2 \pm 1.6) MeV/c^2$ and width $(13 \pm 6 \pm 3) MeV$, where the first uncertainty is statistical and the second systematic. A spin-parity analysis supports the assignment $J^P=0^+$ and therefore the ident ification of the signal as due to the $\chi_{c0}(2P)$ resonance. In this hypothesis we determine the product between the two-photon width and the final state branching fraction to be $(52 \pm 10 \pm 3) eV$

A Mild and Regioselective Method for α-Bromination of β-Keto Esters and 1,3-Diketones Using Bromodimethylsulfonium Bromide (BDMS)

Abstract: Bromodimethylsulfonium bromide has been found to be an effective and regioselective reagent for α-monobromination of β-keto esters and 1,3-diketones. A wide variety of β-keto esters and 1,3-diketones undergo chemoselective α-monobromination with excellent yields at 0−5 °C or room temperature. The notable advantages of this protocol are no need of chromatographic separation, use of less hazardous reagent than molecular bromine, and no added base, Lewis acid, or other catalyst.