Structure-Activity and Mechanism Studies on Silicon Phthalocyanines with Plasmodium falciparum in the Dark and Under Red Light

Syntheses for the new photosensitizers HOSiPc-OSi(CH₃)₂(CH₂)₃N(CH₂)₁ or ₃(CH₃)₂, Pc 34 and Pc 25, have been developed and the order of activity of these photosensitizers and the previously reported photosensi-tizer Pc 4, HOSiPcOSi(CH₃)₂(CH₂)₃N(CH₃)₂, in the dark and with broad-band red light toward Plasmodium falciparum in red blood cell (RBC) suspensions has been studied. The order of activity has been found to be Pc 4 Pc 34 Pc 25. Thus, the activity of the photosensitizers under both sets of conditions is inversely proportional to the length of their terminal amino alkyl chains. The 50% inhibition dye concentration (IC₅₀) in the dark for the parasites in RBC suspension with Pc 4 is 24 nM and the dye concentration and light fluence that yield:3 log₁₀ of parasite inactivation with Pc 4 are 2 mM and 3 J/cm², respectively. The synthesis of DNA and proteins by the parasites in culture was strongly inhibited by Pc 4 in the dark while parasite lactate dehydrogenase (pLDH) activity was unaffected. With Pc 4 and light, DNA and protein synthesis of the parasites in culture was strongly inhibited, pLDH activity of the parasites was moderately inhibited and ribosome density of the parasite cells was reduced. Gel electrophoresis studies showed that synthesis of all parasite proteins was inhibited to a similar extent. These results suggest that Pc 4 both in the dark and with light inactivates the cells by disturbing their machinery for the synthesis of not just one but a whole series of proteins. It is concluded that Pc 4 and light may be able to serve as a practical sterilization combination not only for HIV and other viruses but also for malaria parasites in RBC concentrates, and that Pc 4 by itself may have potential as a chemotherapeutic agent toward malaria.     

Particle spin from representations of the diffeomorphism group

The semidirect productI∧K of Schwartz' spaceI of functions on ?³ with the groupK of diffeomorphisms of ?³ provides a model for quantum theory based on local currents. Certain unitary representations of ?^K are induced by representations of \(\overline {{\text{SL(3, }}\mathbb{R}{\text{)}}}\) . From the local currents in these representations, we construct the generators of local rigid rotations, with respect to which the Hilbert space decomposes into invariant subspaces of fixed spin carrying representations of local SU(2). The physical interpretation of this procedure is discussed.     

Bounded variation of {V n } and its limit

This note studies relations between limV _n and the lower long-run average value ( \(\underline V \) ) in dynamic programming. It is shown that a certain bounded variation conditions of {V _n } implies that limV _n = \(\underline V \) .     

Stimuli‐Responsive Lipidic Cubic Phase: Triggered Release and Sequestration of Guest Molecules

New stimuli‐responsive nanomaterials, made up of host–guest lipidic cubic phases (LCPs) are presented. These biocompatible, stable, transparent and water‐insoluble LCPs are composed of monoolein (MO) as a neutral host, and small amounts of one of three judiciously designed and synthesized designer lipids as guest that preserve the structure and stability of LCPs, but render them specific functionalities. Efficient pH‐ and light‐induced binding, release and sequestration of hydrophilic dyes are demonstrated. Significantly, these processes can be performed sequentially, thereby achieving both temporal and dosage control, opening up the possibility of using such LCPs as effective carriers to be used in drug delivery applications. Specifically, because of the inherent optical transparency and molecular isotropy of LCPs they can be envisaged as light‐induced drug carriers in ophthalmology. The results presented here demonstrate the potential of molecular design in creating new functional materials with predicted operating mode.     

Real‐Time In‐Situ Monitoring of a Tunable Pentapeptide Gel–Crystal Transition

Supramolecular gels often become destabilized by the transition of the gelator into a more stable crystalline phase, but often the long timescale and sporadic localization of the crystalline phase preclude a persistent observation of this process. We present a pentapeptide gel–crystal phase transition amenable for continuous visualization and quantification by common microscopic methods, allowing the extraction of kinetics and visualization of the dynamics of the transition. Using optical microscopy and microrheology, we show that the transition is a sporadic event in which gel dissolution is associated with microcrystalline growth that follows a sigmoidal rate profile. The two phases are based on β‐sheets of similar yet distinct configuration. We also demonstrate that the transition kinetics and crystal morphology can be modulated by extrinsic factors, including temperature, solvent composition, and mechanical perturbation. This work introduces an accessible model system and methodology for studying phase transitions in supramolecular gels.     

3-T MR-guided brachytherapy for gynecologic malignancies

Gynecologic malignancies are a leading cause of death in women worldwide. Standard treatment for many primary and recurrent gynecologic cancer cases includes external-beam radiation followed by brachytherapy. Magnetic resonance (MR) imaging is beneficial in diagnostic evaluation, in mapping the tumor location to tailor radiation dose and in monitoring the tumor response to treatment. Initial studies of MR guidance in gynecologic brachytherapy demonstrate the ability to optimize tumor coverage and reduce radiation dose to normal tissues, resulting in improved outcomes for patients.     

Intramolecular van der Waals Interactions Challenge Anion Binding in perthio-Bambusurils

Bambusurils (BUs) are known to be rigid cavitands that feature an extended, jigger-like conformation, and the BU[6]s strongly bind anions within their hydrophobic cavity. These features are not necessarily shared by the family of perthio-BUs. This study reveals that perthio-BUs assume a compact conformation and perthio-BU[6]s are poor anion binders, crystallizing as anion-free species from solutions containing halide salts. Computational studies show that the equatorial sulfur atoms compete against guest anions for binding with the glycoluril methine groups via strong van der Waals (vdW) attractive interactions. These competitive contacts not only account for the diminished anion-binding of perthio-BUs, but also explain their compact conformation. The semithio- and perthio-BU[4]s form linear coordination polymers with Hg^II in the solid-state regardless of their intrinsic molecular conformation. The strong involvement of sulfur atoms in intramolecular interactions differentiates the equatorial from the axial (peripheral) heteroatoms, thus offering chemoselective and regioselective transformations.