Eulogy for Professor Mirka Miller (1949–2016)

The CIMPA Research School on Mathematical Models for Security Applications was dedicated to the memory of Emeritus Professor Mirka Miller, who suggested that it be held in Havana. Mirka Miller, member of the editorial board of Mathematics in Computer Science, devoted her research to Graph Theory and Data Security, fields where she made important and beautiful contributions.     

Gold(I)-dithioether supramolecular polymers: synthesis, characterization, and luminescence

A series of discrete compounds and supramolecular polymers were synthesized by self-assembly of dithioether building blocks and HAuCl4.3H2O. In complexes 1 {[AuL(1-Me)Cl], where L(1-Me) is bis(methylthio)methane} and 2 {[Au2L(2-Ph)Cl2], where L(2-Ph) is 1,2-bis(phenylthio)ethane}, adjacent units are connected via aurophilic interactions. Complex 1, a one-dimensional (1D) supramolecular polymer, and complex 2, a two-dimensional supramolecular network, both feature nearly linear [Au-Au-](infinity) chains. Complexes 4a, 4b, and 4c, all of which contain 1,3-bis(phenylthio)propane (L(3-Ph)), are polymorphs having the composition [Au2L(3-Ph)Cl2]. Complex 3 {[Au2L(1-Ph)Cl2], where L(1-Ph) is bis(phenylthio)methane}and complexes 4a and 4b consist of nearly identical 1D supramolecular polymers formed through Au-Au interactions. The third polymorph, 4c, is a molecular complex, as it does not have metal-metal interactions. Complex 5 {[Au2L(4-Ph)Cl2], where L(4-Ph) is 1,4-bis(phenylthio)butane} is also molecular. UV-vis spectra showed that the absorption bands of these complexes are allowed ligand-centered transitions between 230 and 260 nm. Complexes 1, 2, and 6 {[AuL(3-Me)Cl], where L(3-Me) is 1,3-bis(methylthio)propane} exhibited solid-state luminescence at 5 K with vibronic progressions and band maxima at approximately 570 nm. It is suggested that complex 6 contains [Au-Au-](infinity) chains.     

Determination of the amplitude of the repulsive-pair potential between particles clothed by end-grafted polymers

 We examine the problem of the determination of the repulsive potential between spherical particles clothed by long end-grafted flexible polymers. This potential varying with the distance according to a logarithmic law has a potential amplitude that depends on the number, L, of grafting chains per particle. The purpose of this work is to compute such a potential amplitude. The clothed particles are first regarded as star polymers with small enough diameter and the same number of arms. Then, the amplitude potential is identified to the critical exponent related to the contact probability between cores of these stars, which allows us to find a universal function for the expected potential amplitude depending on L and d-space dimension only. In two-dimensional space, conformal invariance is used to extract the potential amplitude as a function of L. For dimensions greater than 2, the potential amplitude is obtained within the framework of renormalization theory to third order in ɛ=4 − d, where d is the critical dimension of the system. To determine the best three-dimensional expression for the potential amplitude, A _L , use is made of the Padé–Borel transformation, which provides a closer form valid for small, intermediate and high values of L. This form of potential amplitude, consistent with the exact scaling asymptotic value of Witten and Pincus [(1986) Macromolecules 19:2509], allows us to find the associated prefactor. The procedure is also extended to interacting stars of different numbers of arms. Received: 4 October 1999 Accepted: 2 January 2001     

Luminescent PtII and PtIV Platinacycles with Anticancer Activity Against Multiplatinum-Resistant Metastatic CRC and CRPC Cell Models

Platinum-based chemotherapy persists to be the only effective therapeutic option against a wide variety of tumours. Nevertheless, the acquisition of platinum resistance is utterly common, ultimately cornering conventional platinum drugs to only palliative in many patients. Thus, encountering alternatives that are both effective and non-cross-resistant is urgent. In this work, we report the synthesis, reduction studies, and luminescent properties of a series of cyclometallated (C,N,N′)Pt^IV compounds derived from amine–imine ligands, and their remarkable efficacy at the high nanomolar range and complete lack of cross-resistance, as an intrinsic property of the platinacycle, against multiplatinum-resistant colorectal cancer (CRC) and castration-resistant prostate cancer (CRPC) metastatic cell lines generated for this work. We have also determined that the compounds are effective and selective for a broader cancer panel, including breast and lung cancer. Additionally, selected compounds have been further evaluated, finding a shift in their antiproliferative mechanism towards more cytotoxic and less cytostatic than cisplatin against cancer cells, being also able to oxidize cysteine residues and inhibit topoisomerase II, thereby holding great promise as future improved alternatives to conventional platinum drugs.     

Trivalent lanthanide interactions with a terdentate bis(dialkyltriazinyl)pyridine ligand studied by electrospray ionization mass spectrometry

The 2,6-bis(5,6-dialkyl-1,2,4-triazin-3-yl)pyridines (DATPs) belong to a new family of extracting agents recently developed in the framework of nuclear fuel reprocessing. These molecules exhibit exceptional properties to separate actinides(III) from lanthanides(III) in nitric acid solutions. A previous work showed that electrospray ionization mass spectrometry (ESI-MS) is a reliable technique to provide solution data such as stoichiometries and conditional stability constants of various DATP complexes with europium and evidenced the unusual capability of DiPTP [bis(di-iso-propyltriazinyl)pyridine] ligand to form 1:3 complexes in nitric acid solution. This latter result is further investigated by considering DiPTP complexation features with the complete lanthanide family. As a starting point of the experimental procedure used for stability constant evaluation, the intensity distribution of ions detected by ESI-MS is studied for solutions containing Ln(NO(3))(3) in water/methanol (1:1 v/v) with the pH value set at 2.8 and 4.6 by HNO(3) additions. At pH 2.8, the nitrate anions are found to prevent lanthanides from processes occurring within the ion source: redox phenomena or gas-phase reactions with methanol which give species such as [Ln(MeO)(2)](+). Thus, the total intensity of MS signals from [Ln(NO(3))(2)(H(2)O)(p)(MeOH)(n)](+) ions is found proportional to the metal ion concentration. At pH 4.6, with lower nitrate concentration, the nature of the species identified on mass spectra depends on the electronic properties of the lanthanide elements. It is shown that Ln(III) complexation with DiPTP leads to the exclusive formation of 1:3 complexes with the whole lanthanide series which may be due not only to the hydrophobic exterior of the ligand but also to the unusual electronic density distribution in DATP ligands as compared with other aza-aromatic ligands. The conditional stability constants of the 1:3 lanthanide(III) complexes with DiPTP have been determined at pH 2.8 and are found to increase almost regularly from La (log beta(3)(app) = 11.7 +/- 0.1) to Lu (log beta(3)(app) = 16.7 +/- 0.8). Moreover, the kinetic stability of the gas-phase 1:3 complexes obtained by electrospray has been investigated by energy-resolved collision-induced dissociation and provides useful information on the bonding and structure.     

Investigation of the interaction between 1-hydroxyethane-1,1'-diphosphonic acid (HEDP) and uranium(VI)

A detailed study, using a panel of spectroscopic analytical methods, of the complexation between 1-hydroxyethane-1,1'-diphosphonic acid (HEDP) and uranyl ion (UO(2)(2+)) is reported. Results suggest that the metal complex is present as only 1:1 (metal/ligand) species at low concentration (<10(-)(4) M). The conditional constants of this complex were determined at various pH using time-resolved laser-induced fluorescence (TRLIF) and electrospray ionization mass spectrometry (ESI-MS). Further investigations indicate the presence of a 1:2 (metal/ligand) complex at higher concentrations ( approximately 10(-)(2) M). Selectivity studies as well as structural aspects are presented.     

Pressure-induced order transition in nanodot-forming diblock copolymers at the air/water interface

Understanding and controlling the processes in block copolymer (BC) monolayers at the air/water interface during surface area compression is a key issue for producing ultrathin films of predetermined morphology with well-defined order and known dimensions. Langmuir isotherms of nanodot-forming BC monolayers generally display a plateau indicative of a 2D phase transition, which has been the subject of various interpretations in the literature. Here, based on investigations of Langmuir-Blodgett and Langmuir-Schaefer nanodot films of PS-P4VP mixed with 3-n-pentadecylphenol (PDP), we show by atomic force microscopy (AFM) that it involves a change in nanodot packing order (from quasi-hexagonal to quasi-square), argued to be a general phenomenon for nanodot BC monolayers. It is accompanied by system-specific conformational changes (as discussed in previous literature), which, in the present case, implicate PDP alkyl chain ordering, as deduced previously from in situ infrared data and indirectly supported here by AFM imaging.     

Self-patterned mixed phospholipid monolayers for the spatially selective deposition of metals

Metal-reactive organosulfur groups were patterned onto mica and silicon surfaces by dewetting instabilities during the Langmuir-Blodgett (LB) deposition of phase-separated mixed phospholipid monolayers. Monolayers were formed from binary mixtures of dipalmitoylphosphatidylcholine (DPPC), dilauroylphosphatidylcholine (DLPC), and their ω-methyldisulfide-dialkylphosphatidylcholine analogues, DSDPPC and DSDLPC. Patterns of highly parallel stripes of condensed DPPC or DSDPPC, protruding by 0.7-0.9 nm from a fluid matrix of DLPC or DSDLPC, were observed over areas extending at least 30 × 30 μm(2) in the LB films. The average stripe width varied from ca. 150 to 500 nm, depending on the lipid composition and deposition pressure. X-ray photoelectron spectroscopy confirmed that the phospholipid-monolayer-bound methydisulfides react with Au vapor to form a gold-thiolate species. The adsorption of thermally evaporated Au, Ag, and Cu onto DSDPPC/DLPC and DPPC/DSDLPC patterns was investigated by field emission gun scanning electron microscopy (FEGSEM) and atomic force microscopy (AFM). A change in phase contrast is observed in FEGSEM and AFM over the methyldisulfide-functionalized areas following metal deposition due to metal-thiolate bond formation. An increase in step height between the DSDPPC stripes and nonfunctionalized DLPC background following metal deposition, as well as the resistance of the metal-coated DSDPPC or DSDLPC regions to detergent extraction from the surface, attest to a selective metallization of the pattern. Our results indicate that the preferential adsorption of vapor-deposited metal onto the ω-methyldisulfide-terminated phase occurs at submonolayer coverages. The chemical reactivity exhibited by the organosulfur-modified phospholipid LB films make these templates potentially interesting for the fabrication of solid-supported patterns of metal nanostructures.