Esterase-Activatable Synthetic M+/Cl− Channel Induces Apoptosis and Disrupts Autophagy in Cancer Cells

The formation of a supramolecular synthetic M⁺/Cl⁻ channel in the membrane phospholipid bilayer has been reported upon activation of a methyl pivalate-linked N¹,N³-dialkyl-2-hydroxyisophthalamide by esterases. The channel formation induces apoptosis in cancer cells via the intrinsic pathway. Interestingly, the supramolecular channel was also shown to disrupt autophagy in cancer cells by causing alkalization of lysosomes – a feature that has been confirmed at the cellular and protein level.     

Free energy for the Lifshitz point in the disordered phase

The free energy for the biaxial Lifshitz point is calculated to order ? = 5 d in the disordered phase using the trajectory integral technique.     

The jost function and bound state solution for the hulthén potential

The parameters of the attractive Hulthén potential are obtained in terms of the parameters of effective range theory by using the Jost function for the potential. The bound state solution for 1 + 0 is found from the corresponding Jost solution. The possibility of extending the present treatment to higher angular momentum states is discussed.     

Asynchronous Teams: Cooperation Schemes for Autonomous Agents

Experiments over a variety of optimization problems indicate that scale-effective convergence is an emergent behavior of certain computer-based agents, provided these agents are organized into an asynchronous team (A-Team). An A-Team is a problem-solving architecture in which the agents are autonomous and cooperate by modifying one another's trial solutions. These solutions circulate continually. Convergence is said to occur if and when a persistent solution appears. Convergence is said to be scale-effective if the quality of the persistent solution increases with the number of agents, and the speed of its appearance increases with the number of computers. This paper uses a traveling salesman problem to illustrate scale-effective behavior and develops Markov models that explain its occurrence in A-Teams, particularly, how autonomous agents, without strategic planning or centralized coordination, can converge to solutions of arbitrarily high quality. The models also perdict two properties that remain to be experimentally confirmed: construction and destruction are dual processes. In other words, adept destruction can compensate for inept construction in an A-Team, and vice-versa. (Construction refers to the process of creating or changing solutions, destruction, to the process of erasing solutions.) solution quality is independent of agent-phylum. In other words, A-Teams provide an organizational framework in which humans and autonomous mechanical agents can cooperate effectively.     

Ligand-gated synthetic ion channels

Supramolecular pi-stack architecture is fundamental in DNA chemistry but absent in biological and synthetic ion channels and pores. Here, a novel rigid-rod pi-stack architecture is introduced to create synthetic ion channels with characteristics that are at the forefront of rational design, that is, ligand gating by a conformational change of the functional supramolecule. Namely, the intercalation of electron-rich aromatics is designed to untwist inactive electron-poor helical pi-stacks without internal space into open barrel-stave ion channels. Conductance experiments in planar lipid bilayers corroborate results from spherical bilayers and molecular modeling: Highly cooperative and highly selective ligand gating produces small, long-lived, weakly anion selective, ohmic ion channels. Structural studies conducted under conditions relevant for function provide experimental support for helix-barrel transition as origin of ligand gating. Control experiments demonstrate that minor structural changes leading to internal decrowding suffice to cleanly annihilate chiral self-organization and function.     

Variation of multiplicities of the secondary charged particles on the geometry of collision

The total charge of the projectile spectator fragments, Q_pf is taken as a measure of the degree of centrality of collision thus defining the collision geometry. In this paper the mean multiplicities of the different charged secondaries emitted in the interaction of ²⁴Mg-Em at 4.5A GeV have been investigated as a function of the total charge Q_pf of the projectile spectator fragments. It has been observed that the average number of the produced particles, 〈N^s〉 and the heavily ionizing particles, 〈N_h> decreases exponentially with the increase of Q_pf showing strong correlation with the geometry of the collision. An attempt has also been made to compare these results with ⁸⁴Kr-Em interaction at 0.95A GeV.     

Schiff base supported mononuclear organotin(IV) complexes: Syntheses,structures and fluorescence cell imaging

Three mononuclear organotin(IV) complexes supported by Schiff bases have been synthesized. The complexes [(C₆H₅)₂Sn(L)] ( 1 ), [(t‐Bu)₂Sn(L)] ( 2 ) and [(t‐Bu)₂Sn(L')] ( 3 ) (L, L' = deprotonated Schiff bases) were obtained in good yield by the reaction of Schiff bases H ₂ L or H ₂ L′ with corresponding diorganotin dichlorides respectively. All newly synthesized complexes were characterized by means of FT‐IR spectroscopy, elemental analysis and multinuclear (¹H, ¹³C and ¹¹⁹Sn) NMR spectroscopy. In addition, single crystal X‐ray diffraction analyses were employed to establish the solid state molecular structures of these complexes. The structures of 1 – 3 reveal that all complexes are mononuclear with a five‐coordinated tin(IV) centre in it. The absorption and emission properties of all complexes have been investigated. Moreover, cytotoxicity and fluorescence cell imaging studies of theses complexes have been performed.     

CF3CF=CH2 and (Z)-CF3CF=CHF: temperature dependent OH rate coefficients and global warming potentials

Rate coefficients over the temperature range 206-380 K are reported for the gas-phase reaction of OH radicals with 2,3,3,3-tetrafluoropropene (CF(3)CF=CH(2)), k(1)(T), and 1,2,3,3,3-pentafluoropropene ((Z)-CF(3)CF=CHF), k(2)(T), which are major components in proposed substitutes for HFC-134a (CF(3)CFH(2)) in mobile air-conditioning units. Rate coefficients were measured under pseudo-first-order conditions in OH using pulsed-laser photolysis to produce OH and laser-induced fluorescence to detect it. Rate coefficients were found to be independent of pressure between 25 and 600 Torr (He, N(2)). For CF(3)CF=CH(2), the rate coefficients, within the measurement uncertainty, are given by the Arrhenius expression k(1)(T)=(1.26+/-0.11) x 10(-12) exp[(-35+/-10)/T] cm(3) molecule(-1) s(-1) where k(1)(296 K)=(1.12+/-0.09) x 10(-12) cm(3) molecule(-1) s(-1). For (Z)-CF(3)CF=CHF, the rate coefficients are given by the non-Arrhenius expression k(2)(T)=(1.6+/-0.2) x 10(-18)T(2) exp[(655+/-50)/T] cm(3) molecule(-1) s(-1) where k(2)(296 K)=(1.29+/-0.06) x 10(-12) cm(3) molecule(-1) s(-1). Over the temperature range most relevant to the atmosphere, 200-300 K, the Arrhenius expression k(2)(T)=(7.30+/-0.7) x 10(-13) exp[(165+/-20)/T] cm(3) molecule(-1) s(-1) reproduces the measured rate coefficients very well and can be used in atmospheric model calculations. The quoted uncertainties in the rate coefficients are 2sigma (95% confidence interval) and include estimated systematic errors. The global warming potentials for CF(3)CF=CH(2) and (Z)-CF(3)CF=CHF were calculated to be <4.4 and <3.6, respectively, for the 100 year time horizon using infrared absorption cross sections measured in this work, and atmospheric lifetimes of 12 and 10 days that are based solely on OH reactive loss.     

Excitonically Coupled Cyclic BF2 Arrays of Calix[8]‐ and Calix[16]phyrin as Near‐IR‐Chromophores

Two giant calix[n]phyrin derivatives namely calix[8]‐ ( 4 ) and calix[16]phyrin ( 5 ), involving two and four BF₂ units, respectively, were prepared through the condensation of the bis‐naphthobipyrrolylmethene‐BF₂ complex ( 3 ) with pentafluorobenzaldehyde. Calix[n]phyrins 4 and 5 display extremely high extinction coefficients (3.67 and 4.82×10⁵ m ^?1 cm^?1, respectively) in the near‐IR region, which was taken as initial evidence for strong excitonic coupling within these cyclic multi‐chromophoric systems. Detailed insights into the effect of excitonic coupling dynamics on the electronic structure and photophysical properties of the macrocycles came from fluorescence, time‐correlated single‐photon counting (TCSPC) and transient absorption (TA) measurements. Support for these experimental findings came from theoretical studies. Theory and experiment confirmed that the coupling between the excitons depends on the specifics of the calix[n]phyrin structure, not just its size.     

Study of the kinetics of the reactions of NO3 with HO2 and OH

The Absolute rate constants for the gas-phase reactions of NO₃ with HO₂ and OH have been determined using the discharge flow laser magnetic resonance method (DF-LMR). Since OH was found to be produced in the reaction of HO₂ with NO₃, C₂F₃Cl was used to scavenge it. The overall rate constant, k₁, for the reaction, HO₂ + NO₃ → products, was measured to be k₁=(3.0 ± 0.7)×10^?12 cm³ molecule^?1 s^?1 at (297 ± 2) K and P=(1.4 – 1.9) torr. This result is in reasonable agreement with the previous studies. Direct detection of HO₂ and OH radicals and the use of three sources of NO₃ enabled us to confirm the existence of the channel producing OH:HO₂+NO₃→OH+NO₂+O₂ (1a); the other possible channel is HO₂+NO₃→HNO₃+O₂ (1b). From our measurements and the computer simulations, the branching ratio, k_1a/(k_1a + k_1b), was estimated to be (1.0). The rate coefficient for the reaction of OH with NO₃ was determined to be (2.1 ± 1.0) × 10^?11 cm³ molecule^?1 s^?1. © 1993 John Wiley & Sons, Inc.