The unusual cyclic products from tetra- and penta-peptides of α-methylalanine

Tetra- and pentapeptides of α-methylalanine give with PCl₅, SOCl₂ etc. intermediates which, with or without loss of amino adds, lead to bi- and tricyclic products containing imidazole and piperazine rings through different routes.     

Self-assembled amphiphilic fluorescent probe: detecting pH-fluctuations within cancer cells and tumour tissues

Abnormal anaerobic metabolism leads to a lowering of the pH of many tumours, both within specific intracellular organelles and in the surrounding extracellular regions. Information relating to pH-fluctuations in cells and tissues could aid in the identification of neoplastic lesions and in understanding the determinants of carcinogenesis. Here we report an amphiphilic fluorescent pH probe (CS-1) that, as a result of its temporal motion, provides pH-related information in cancer cell membranes and selected intracellular organelles without the need for specific tumour targeting. Time-dependent cell imaging studies reveal that CS-1 localizes within the cancer cell-membrane about 20 min post-incubation. This is followed by migration to the lysosomes at 30 min before being taken up in the mitochondria after about 60 min. Probe CS-1 can selectively label cancer cells and 3D cancer spheroids and be readily observed using the green fluorescence channel (λ_em = 532 nm). In contrast, CS-1 only labels normal cells marginally, with relatively low Pearson''s correlation coefficients being found when co-incubated with standard intracellular organelle probes. Both in vivo and ex vivo experiments provide support for the suggestion that CS-1 acts as a fluorescent label for the periphery of tumours, an effect ascribed to proton-induced aggregation. A much lower response is seen for muscle and liver. Based on the present results, we propose that sensors such as CS-1 may have a role to play in the clinical and pathological detection of tumour tissues or serve as guiding aids for surgery.

A self-assembled amphiphilic fluorescent probe allows pH-fluctuations within cancer cells and tumour tissues to be readily detected.     

Triton-emission cross sections with 30 MeV d(Be) break-up neutrons

Triton-emission cross sections were measured for Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Nb, Mo, Ag, Ta, Tl, Pb and Bi with a 30 MeV d(Be) break-up neutron spectrum characterized by a multiple-foil activation technique. The accumulated tritium was separated by vacuum extraction and measured by low-level gas-phase β^? counting. The systematic trend in the cross sections is somewhat similar to that in the 53 MeV d(Be) break-up neutron spectrum; apart from some initial decrease as a function of Z, the cross section is almost constant over the entire range of Z = 22 to 83. The magnitudes of the cross sections lie between those with 14 MeV neutrons and 53 MeV d(Be) break-up neutrons. Hauser-Feshbach calculations show that the statistical model describes the triton-emission cross sections for nuclei in the (2s, ld) shell within a factor of 2; for the heavier nuclei, however, the calculated cross sections are much smaller than the experimental values.     

Camouflaging Structural Diversity: Co‐crystallization of Two Different Nanoparticles Having Different Cores But the Same Shell

Two ligand‐protected nanoscale silver moieties, [Ag₄₆(SPhMe₂)₂₄(PPh₃)₈](NO₃)₂ and [Ag₄₀(SPhMe₂)₂₄(PPh₃)₈](NO₃)₂ (abbreviated as Ag₄₆ and Ag₄₀, respectively) with almost the same shell but different cores were synthesized simultaneously. As their external structures are identical, the clusters were not distinguishable and become co‐crystallized. The occupancy of each cluster was 50 %. The outer shell of both is composed of Ag₃₂S₂₄P₈, which is reminiscent of fullerenes, and it encapsulates a well‐studied core, Ag₁₄ and a completely new core, Ag₈, which correspond to a face‐centered cube and a simple cube, respectively, resulting in the Ag₄₆ and Ag₄₀ clusters. The presence of two entities (Ag₄₀ and Ag₄₆ clusters) in a single crystal and their molecular formulae were confirmed by detailed electrospray ionization mass spectrometry. The optical spectrum of the mixture showed unique features which were in good agreement with the results from time‐dependent density functional theory (TD‐DFT).     

Structure elucidation,DNA binding,DFT, molecular docking and cytotoxic activity studies on novel single crystal (E)-1-(2-fluorobenzylidene)thiosemicarbazide

Compound 3 {(E)-1-(2-fluorobenzylidene)thiosemicarbazide} – a new Schiff base of thiosemicarbazide has been synthesized, characterized and reported for crystal structure. Planer side chain in the crystal structure was observed co-planer with aromatic ring plane and molecules were connected into centrosymmetric dimmers via intermolecular hydrogen bonding. DFT geometry optimization and the relevant quantum parameters indicated unstable and reactive nature of compound 3. Experimental and theoretical findings for DNA binding by UV–visible, cyclic voltammetry and molecular docking studies showed consistency in kinetic (K_b) and thermodynamic (ΔG) parameters and that compound 3 significantly interacted with DNA via intercalation. Viscometric analysis further comprehended intercalation as possible binding mode of the compound with DNA and non-denaturing of DNA in the presence of 10% aqueous DMSO. Docked parameters further assured the drug like characteristics of the investigated compound as fit in Lipinski’s criteria. Dose dependant cytotoxic activity of compound 3 against human Huh-7 cell line indicated its anti-cancer potential at 100?µg/ml concentration.     

B(C6F5)3: an efficient catalyst for reductive alkylation of alkoxy benzenes and for synthesis of triarylmethanes using aldehydes

Tris(pentafluorophenyl)borane [B(C₆F₅)₃] has been used as an efficient catalyst for reductive alkylation of alkoxy benzenes using aldehydes as an alkylating agent in the presence of polymethylhydrosiloxane (PMHS). Various alkylated trimethoxybenzene derivatives have been prepared in good to high yields. In addition, B(C₆F₅)₃ was also used as a catalyst for the reaction of electron-rich arenes with aldehydes to obtain triarylmethanes. The use of reductive alkylation protocol for the synthesis of an isochroman and tetrahydroisoquinoline derivatives has also been demonstrated.     

“Islands in Sea” and “Lakes in Mainland” phases and related transitions simulated on a square lattice

We describe the Island-Mainland (IM) transition on a square lattice. Black squares are randomly dropped on a white background, with increasing concentration p. We define black (white) clusters as groups of black (white) squares, connected through edges or corners on a quasi-2D system. At a certain p the black islands in white sea (IS) phase crosses over to a mixed phase (MP). At still larger p the MP phase crosses over to the lakes in mainland (LM) phase with white lakes in a black mainland. We show that the Euler number, defined as difference between number of white clusters and number of black clusters goes through extrema near these transition points. The phenomenon is supported by experimental observations.     

Design of a RF window for 170 GHz, 1 MW gyrotron for ECRH application

This paper describes the design of a large sized diamond window for 1 MW, 170 GHz gyrotron. The diameter and the thickness of the diamond window are 80 mm and 1.482 mm, respectively, whose edge is directly cooled by water. The CST microwave studio has been used for the S-parameter, and finite element analysis code ANSYS has been used for the thermal and the structural simulation. The return loss (S₁₁) and insertion loss (S₂₁) of the 170 GHz gyrotron window have been found −39.80 dB and −0.011 dB, respectively. The thermal and structural analysis of RF window the 397 K temperature at disk center and maximum displacement 0.01 mm has been found in the window disk during the thermal analysis.     

Natural flavonoids interact with dinitrobenzene system in aprotic media: an electrochemical probing

Three structurally related natural flavonoids (FlOH), quercetin (Q), rutin (R) and morin (M), were investigated by cyclic voltammetry to probe their interactions with hazardous 1,4-dinitrobenzene (1,4-DNB) using a glassy carbon electrode. Scavenging of 1,4-DNB by FlOH was inferred from a positive shift in reduction potential, decrease in anodic peak current, and irreversible electrochemical behavior of 1,4-DNB on increasing the flavonoid concentration. The homogeneous bi-molecular rate constant (k2) was determined using the Nicholson-Shain equation and found to be higher for the dianion. Morin posed a comparatively higher k2 value for its interaction with the 1,4-DNB electrochemical system owing to its more acidic nature and least intramolecular hydrogen bonding. The cyclic voltammetric (CV) results were further supported by HyperchemPM3 quantum mechanical semi-empirical calculations, which point towards E(r)C(i) interactions between flavonoids and 1,4-DNB. The present investigation is biologically significant in terms of natural flavonoidal scavenging activity toward toxins such as dinitroaromatics.     

Synthesis and Characterization of High-Quality Polycrystalline Sample NiV2O6 by Solid-State Reaction Technique

Physics of the Solid State - Employing the solid-state reaction route, good quality polycrystalline sample NiV2O6 is prepared that has effective application in rechargeable Li-ion batteries. The...