Studies on the encapsulation of various anions in different fullerenes using density functional theory calculations and Born-Oppenheimer molecular dynamics simulation

The density functional theory (DFT)-based Becke's three parameter hybrid exchange functional and Lee-Yang-Parr correlation functional (B3LYP) calculations and Born-Oppenheimer molecular dynamics (BOMD) simulations have been performed to understand the stability of different anions inside fullerenes of various sizes. As expected, the stability of anion inside the fullerene depends on its size as well as on the size of the fullerene. Results show that the encapsulation of anions in larger fullerenes (smaller fullerene) is energetically favorable (not favorable). The minimum size of the fullerene required to encapsulate F(-) is equal to C(32). It is found from the results that C(60) can accommodate F(-), Cl(-), Br(-), OH(-), and CN(-). The electron density topology analysis using atoms in molecule (AIM) approach vividly delineates the interaction between fullerene and anion. Although F(-)@C(30) is energetically not favorable, the BOMD results reveal that the anion fluctuates around the center of the cage. The anion does not exhibit any tendency to escape from the cage.     

Bifunctional coordination polymers as efficient catalysts for carbon dioxide conversion

The multidentate ligand H₂ L upon complexation with Zn (II) and Cd (II) provide a one‐dimensional polymeric networks. These coordination polymers (CPs) CP‐1 and CP‐2 containing Zn (II) and Cd (II) metals respectively are well characterized. The single crystal structural analysis confirms the formation of one‐dimensional coordination polymer with zigzag fashion in CP‐1 and ladder chain CP‐2 . Both the CPs are applied as catalysts to synthesize various cyclic carbonates from epoxides and carbon dioxide. The catalysts are giving better conversion under solvent‐free and additive‐free condition using 10 bar CO₂ and 100 °C as optimized pressure and temperature. The detailed kinetic experiments suggesting the first order kinetics, the energy of activation (Ea) is calculated for this catalytic conversion.     

Antibody-recruiting protein-catalyzed capture agents to combat antibiotic-resistant bacteria

Antibiotic resistant infections are projected to cause over 10 million deaths by 2050, yet the development of new antibiotics has slowed. This points to an urgent need for methodologies for the rapid development of antibiotics against emerging drug resistant pathogens. We report on a generalizable combined computational and synthetic approach, called antibody-recruiting protein-catalyzed capture agents (AR-PCCs), to address this challenge. We applied the combinatorial protein catalyzed capture agent (PCC) technology to identify macrocyclic peptide ligands against highly conserved surface protein epitopes of carbapenem-resistant Klebsiella pneumoniae, an opportunistic Gram-negative pathogen with drug resistant strains. Multi-omic data combined with bioinformatic analyses identified epitopes of the highly expressed MrkA surface protein of K. pneumoniae for targeting in PCC screens. The top-performing ligand exhibited high-affinity (EC₅₀ ∼50 nM) to full-length MrkA, and selectively bound to MrkA-expressing K. pneumoniae, but not to other pathogenic bacterial species. AR-PCCs that bear a hapten moiety promoted antibody recruitment to K. pneumoniae, leading to enhanced phagocytosis and phagocytic killing by macrophages. The rapid development of this highly targeted antibiotic implies that the integrated computational and synthetic toolkit described here can be used for the accelerated production of antibiotics against drug resistant bacteria.

Antibody-recruiting protein-catalyzed capture agent (AR-PCCs) are a new class of all-synthetic and highly targeted antibiotics that recruit endogenous immune responses to eliminate drug-resistant microbes.     

Studies on the extraction behaviour of plutonium(IV) from mixed aqueous-organic media with sulphoxides

Extraction behaviour of plutonium (IV) from nitric acid media by two long-chain aliphatic sulphoxides, namely, di-n-hexylsulphoxide and di-n-octylsulphoxide has been investigated in the presence of several water-miscible organic solvents to study their possible synergistic effect on metal ion extraction. Methanol, ethanol, n-and iso-propanol, dioxane, acetone as well as as acetonitrile were used as the organic component of the mixed (polar) phase. These additives affected the extraction to varying degrees. Thus, extractability of Pu increases 2–3 fold with increasing concentration (upto 20%) of acetonitrile, acetone, methanol and ethanol while it decreases with increasing concentration of n-and isopropanol. At high concentration of the former, synergism changes into antagonism. Possible reasons for such behaviour are briefly discussed. Among these organic additives, maximum enhancement in the extraction of Pu(IV) was observed in the presence of acetonitrile. The relative increase in extraction was found to be more at lower sulphoxide concentrations.     

Extraction behavior of uranium(VI), plutonium(IV), zirconium(IV), ruthenium(III) and europium(III) with γ-pre-irradiated solutions of N,N′-methylbutyl substituted amides in n-dodecane

The extraction of plutonium(IV), uranium(VI), zirconium(IV), europium(III) and ruthenium(III) with -pre-irradiated n-dodecane solutions of methylbutyl substituted hexanamide (MBHA), octanamide (MBOA) and decanamide (MBDA) from 3.5M HNO₃ has been studied as a function of absorbed dose up to 184×10⁴ Gray. The distribution ratios (K_d) of uranium(VI) decreased gradually up to a dose of 50×10⁴ Gray and became almost constant thereafter, while ruthenium(III) and europium(III) were not extracted in the entire dose range studied. The K_d values of Pu(IV) decreased gradually up to 10×10⁴ Gray, for MBOA, and 30×10⁴ Gray for MBHA and MBDA and then increased up to a dose of 72×10⁴ Gray, indicating the synergistic effect of radiolytic products at higher doses. The extraction of zirconium(IV) was found to increase gradually up to 72×10⁴ Gray. However, the steep fall in K_d values of plutonium(IV), zirconium(IV) beyond a dose of 72×10⁴ Gray was atrributed to third phase formation. The radiolytic degradation of amides was monitored by quantitative IR spectroscopy and was found to follow the order MBOA>MBDA>MBHA at 184×10⁴ Gray having the amines and carboxylic acids as the main radiolytic products.     

A new chelating resin for preconcentration and determination of Mn(II), Ni(II), Cu(II), Zn(II), Cd(II), and Pb(II) by flame atomic absorption spectrometry

A new polychelatogen, AXAD-16-1,2-diphenylethanolamine, was developed by chemically modifying Amberlite XAD-16 with 1,2-diphenylethanolamine to produce an effective metal-chelating functionality for the preconcentration of Mn(II), Ni(II), Cu(II), Zn(II), Cd(II), and Pb(II) and their determination by flame atomic absorption spectrometry. Various physiochemical parameters that influence the quantitative preconcentration and recovery of metal were optimized by both static and dynamic techniques. The resin showed superior extraction efficiency with high-metal loading capacity values of 0.73, 0.80, 0.77, 0.87, 0.74, and 0.81 mmol/g for Mn(II), Ni(II), Cu(II), Zn(II), Cd(II), and Pb(II), respectively. The system also showed rapid metal-ion extraction and stripping, with complete saturation in the sorbent phase within 15 min for all the metal ions. The optimum condition for effective metal-ion extraction was found to be a neutral pH, which is a great advantage in the preconcentration of trace metal ions from natural water samples without any chemical pretreatment of the sample. The resin also demonstrated exclusive ion selectivity toward targeted metal ions by showing greater resistivity to various complexing species and more common metal ions during analyte concentration, which ultimately led to high preconcentration factors of 700 for Cu(II); 600 for Mn(II), Ni(II), and Zn(II); and 500 for Cd(II) and Pb(II), arising from a larger sample breakthrough volume. The lower limits of metal-ion detection were 7 ng/mL for Mn(II) and Ni(II); 5 ng/mL for Cu(II), Zn(II), and Cd(II), and 10 ng/mL for Pb(II). The developed resin was successful in preconcentrating metal ions from synthetic and real water samples, multivitamin-multimineral tablets, and curry leaves (Murraya koenigii) with relative standard deviations of < or = 3.0% for all analytical measurements, which demonstrated its practical utility.     

Solvent extraction studies of radioisotopic exchange of36Cl with Chloramine-B in strong acid medium

Exchange studies with³⁶Cl and Chloramine-B in strong acid medium revealed that the extent of exchange is less than that occurs at pH 3.3 indicating the formation of a new species of Chloramine-B which is not participating in the exchange reaction and this has been confirmed by conductometric titration of Chloramine-B with dilute solutions of H₂SO₄, HCl, HClO₄ and CH₃COOH.     

A complex two unit system

This paper discusses the availability of a two-unit standby redundant repairable system in which the pdf of the life time of the online unit depends on the time it has spent in the standby state before it is switched online. Explicit expressions for the Laplace transforms of the availability and reliability of the system are obtained by identifying suitable regeneration points.

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Zusammenfassung In dieser Arbeit wird die Verfügbarkeit eines redundanten 2-Komponentensystems mit heißer Reserve und Reparatur betrachtet. -Die Lebensdauerverteilung der Betriebskomponente hängt von der Länge der Zeit ab, die sie vorher als Reservekomponente verbracht hat. Es werden explizite Ausdrücke der Laplacetransformierten für die Verfügbarkeit und Zuverlässigkeit des Systems ermittelt, indem geeignete Regenerationspunkte verwendet werden.

     

Die Zuverlässigkeit eines Systems mit redundanten störanfälligen Komponenten und Reparaturmöglichkeiten

Zusammenfassung Es wird die Zuverlässigkeit eines Systems mit mehreren redundanten Einheiten untersucht, bei dem nicht nur die tätige Einheit, sondern auch die Reserveeinheiten ausfallen und bei dem gestörte Einheiten repariert werden können. Es wird vorausgesetzt, daß die Reparaturzeiten und die Lebensdauern der Reserveeinheiten exponentialverteilt sind, während die Betriebsdauern der tätigen Einheiten, unabhängig von ihrem Alter beim Einsatz, beliebig verteilt sind.Unter diesen Voraussetzungen werden die mittlere Zeit bis zum Ausfall des Systems und die langfristige Verfügbarkeit des Systems explizit für den Fall dreier Einheiten bestimmt.Am Beispiel doppel-exponentialverteilter Betriebsdauern werden die Abhängigkeit dieser Größen von der Reparaturgeschwindigkeit untersucht und die optimale Reparaturrate bestimmt.

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Summary We consider the reliability of a repairable system with several stand-by redundant units, where not only the working unit but also the spares are subject to failure. We assume, that repair-times and life-times of spares are exponentially distributed, whereas the time to failure of a working unit is — independent of its age at the time of switch-on — arbitrarily distributed.Using these assumptions, we derive the expected time to system-failure and the steady-state availability explicitely for the case of three redundant units. The example of double-exponentially distributed working-times is used to examine the dependancy of these characteristics on repair-times, and to calculate the optimal repair-rate.

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Diese Arbeit wurde durch den Sonderforschungsbereich 21 — ökonometrie und Unternehmensforschung — und ein Stipendium der Alexander-von-Humboldt-Stiftung gefördert.