NOPR Collection:

Understanding the unfolding mechanism of human telomeric G-quadruplex using steered molecular dynamics simulation

2017-09-01T00:00:00Z

Title: Understanding the unfolding mechanism of human telomeric G-quadruplex using steered molecular dynamics simulation Authors: Samanta, Pralok K; Pati, Swapan K Abstract: The unfolding pathway of human telomeric G-quadruplex with three G-tetrads in presence of K⁺ and Na⁺ ions, separately using steered molecular dynamics (SMD) simulation is reported. The isothermal-isobaric all-atoms classical molecular dynamics simulation results show that three K⁺ and three Na⁺ ions are required within the central channel of the G-quadruplex (PDB ID: 143D and 2HY9, respectively) to stabilize the respective overall structure. To obtain the unfolded G-quadruplex which is ~5-6 times of its initial contour length, SMD simulation has been carried out by fixing one end of the G-quadruplex and constraining the other end to move only along the long axis (z-axis). The SMD results suggest that the unfolding of G-quadruplex occurs via G-triplex intermediates independent of the presence of cations (K⁺, Na⁺). Page(s): 907-912

Rhenium(I) complex with 2-(benzothiazol-2-yl) quinoline: Synthesis, characterization, spectral properties and DFT/TDDFT investigations

2017-09-01T00:00:00Z

Title: Rhenium(I) complex with 2-(benzothiazol-2-yl) quinoline: Synthesis, characterization, spectral properties and DFT/TDDFT investigations Authors: Sarkar, Rupa; Sinha, Debopam; Maity, Amit; Rajak, Kajal Krishna Abstract: The red colored mononuclear rhenium(I) complex having fac-[Re(CO)₃]⁺ moiety of general formula, [Re(CO)₃(NN)Cl], has been synthesized in excellent yield by reacting [Re(CO)₅Cl] with 2-(benzothiazol-2-yl) quinoline (1:1) in a boiling mixture of methanol+chloroform (3:1, v/v) under argon atmosphere. Elemental, ¹H and ¹³C NMR analysis show the formation of the desired complex. The complex is also characterized by different spectroscopic techniques. The ground and excited-state geometries, NMR, absorption, and phosphorescence properties of the Re(I) complex are examined by DFT and TDDFT methods. The natural transition orbital and spin density difference map analysis reveals the nature of excitations. The lowest lying triplet excited state is associated with the ³MLCT/³ILCT excited state. The emission-like transition is consistent with the strong ³MLCT/ ³ILCT character. Page(s): 913-924

Facile synthesis of bis(indolyl)methanes over cordierite honeycomb coated with modified forms of zirconia under microwave irradiation condition

2017-09-01T00:00:00Z

Title: Facile synthesis of bis(indolyl)methanes over cordierite honeycomb coated with modified forms of zirconia under microwave irradiation condition Authors: Vasantha, V T; Shamshuddin, S Z Mohamed; D’Souza, Joyce Queeny; Shyamprasad, K; Pratap, S R; Venkatesh Abstract: Zirconia (ZrO₂), Mo(VI)/ZrO₂, W(VI)/ZrO₂ and SO₄^2-/ZrO₂ have been coated on honeycomb monoliths and used as catalytic material in the microwave-assisted synthesis of various bis(indolyl)methane derivatives via condensation. These catalytic materials have been characterized for their properties such as surface acidity, crystallinity, morphology and elemental analysis by suitable techniques. A correlation between the acidity, crystallinity and the catalytic activity of these catalytic materials is observed. The effect of conventional heating and microwave heating on the synthesis of these derivatives has been studied. Microwave-assisted synthesis of bis(indolyl)methane derivatives over zirconia and its modified forms is found to be a fast and facile catalytic route. Up to 98% yield of bis(indolyl)methanes is obtained in a very short reaction time of 4 min under microwave irradiation, whereas it requires 20 min to obtain 98% yield under conventional heating.The honeycomb monoliths coated with modified forms of zirconia as catalytic materials are efficient, easily reactivable and reusable for at least six reaction cycles. Page(s): 925-933

Functionalized surface for electrochemical sensing of electrochemically inactive alkali metal ion

2017-09-01T00:00:00Z

Title: Functionalized surface for electrochemical sensing of electrochemically inactive alkali metal ion Authors: Singh, Urvasini; Kumbhat, Sunita Abstract: The binding of Na⁺ ion to the ionophore 4-aminobenzo-crown-5 has been monitored by cyclic voltammetry using the redox couple Fe(CN)₆^3-/Fe(CN)₆^4- as a mediator redox probe. The recognition properties of the ionophore covalently bound to 11-MUA self assembled monolayer on gold surface is found to be selective for Na⁺ ion over Li⁺ and K⁺ ions.The self-assembled sensor interface is highly stable, reproducible and shows good sensitivity for detection of Na⁺ ion. The host-guest recognition of the simple crown ether derivative makes the system highly promising for real-time applications for selective detection of electrochemically inactive alkali metals by electrochemical transducer. Page(s): 934-938