Structures of some surfactant—polyelectrolyte complexes

Structures of complexes formed in aqueous solutions by some anionic polyelectrolytes (double and single stranded (ds and ss) DNA, poly(vinyl sulfonate) (PVS), and poly(styrene sulfonate) (PSS)) with a cationic surfactant system consisting of cetyltrimethylammonium bromide (CTAB) and sodium 3-hydroxy-2-naphthoate (SHN) have been determined using small angle X-ray diffraction. All complexes are found to have a two-dimensional (2-D) hexagonal structure at low SHN concentrations. Analysis of the diffraction data shows that the ds DNA—CTAB complex has an intercalated structure, with each DNA strand surrounded by three cylindrical micelles. On increasing SHN concentration, DNA—CTAB—SHN complexes exhibit a hexagonal-to-lamellar transition, whereas PVS complexes show a hexagonal → centered rectangular → lamellar transition. PSS complexes show yet another sequence of structures. These results indicate the significant influence of the chemical nature of the polyelectrolyte on the structure of the complexes.     

Coalescence in 2 dimensions: experiments on thin copolymer films and numerical simulations

This paper presents on one hand the experimental study of the coalescence kinetics of two closed bidimensional fluid domains at the surface of a multilayered dibloc copolymer film, and on the other hand a numerical simulation of the same evolution. The latter is based on ”diffusive” phenomenological equations which are surface conservative and which neglect the 2-dimensional viscosity of the layers. The successive shapes observed in the experiments and obtained from the simulation are very close. It would not be the case if the 2D viscosity was significant. Received : 17 march 1997 / Revised : 11 september 1997 / Accepted : 2 december 1997     

Discontinuous unbinding of lipid multibilayers

We have observed a discontinuous unbinding transition of lipid bilayer stacks composed of phosphatidylethanolamine and phosphatidylglycerol using x-ray diffraction. The unbinding is reversible and coincides with the main (L(beta)-->L(alpha)) transition of the lipid mixture. Interbilayer interaction potentials deduced from the diffraction data reveal that the bilayers in the L(beta) phase are only weakly bound. The unbinding transition appears to be driven by an abrupt increase in steric repulsion resulting from increased thermal undulations of the bilayers upon entering the fluid L(alpha) phase.     

A proof of Oseledec’s multiplicative ergodic theorem

A new proof of a multiplicate ergodic theorem of Oseledec is presented in this paper.     

From Containers to Catalysts: Supramolecular Catalysis within Cucurbiturils

Cucurbiturils are a family of molecular container compounds with superior molecular recognition properties. The use of cucurbiturils for supramolecular catalysis is highlighted in this concept. Both photochemical reactions as well as thermal transformations are reviewed with an eye towards tailoring substrates for supramolecular catalysis mediated by cucurbiturils.     

Anti‐CRLF2 Antibody‐Armored Biodegradable Nanoparticles for Childhood B‐ALL

B‐precursor acute lymphoblastic leukemia (B‐ALL) lymphoblast (blast) internalization of anti‐cytokine receptor‐like factor 2 (CRLF2) antibody‐armored biodegradable nanoparticles (AbBNPs) are investigated. First, AbBNPsaere synthesized by adsorbing anti‐CRLF2 antibodies to poly(D,L‐lactide‐co‐glycolide) (PLGA) nanoparticles of various sizes and antibody surface density (Ab/BNP) ratios. Second, AbBNPs are incubated with CRLF2‐overexpressing (CRLF2+) or control blasts. Third, internalization of AbBNPs by blasts is evaluated by multicolor flow cytometry as a function of receptor expression, AbBNP size, and Ab/BNP ratio. Results from these experiments are confirmed by electron microscopy, fluorescence microscopy, and Western blotting. The optimal size and Ab/BNP for internalization of AbBNPs by CRLF2+ blasts is 50 nm with 10 Ab/BNP and 100 nm with 25 Ab/BNP. These studies show that internalization of AbBNPs in childhood B‐ALL blasts is AbBNP size‐ and Ab/BNP ratio‐dependent. All AbBNP combinations are non‐cytotoxic. It is also shown that CD47 is very slightly up‐regulated by blasts exposed to AbBNPs. CD47 is “the marker of self” overexpressed by blasts to escape phagocytosis, or “cellular devouring”, by beneficial macrophages. The results indicate that precise engineering of AbBNPs by size and Ab/BNP ratio may improve the internalization and selectivity of future biodegradable nanoparticles for the treatment of leukemia patients, including drug‐resistant minority children and Down's syndrome patients with CRLF2+B‐ALL.     

Phonostat: thermostatting phonons in molecular dynamics simulations

Thermostat algorithms in a molecular dynamics simulation maintain an average temperature of a system by regulating the atomic velocities rather than the internal degrees of freedom. Herein, we present a "phonostat" algorithm that can regulate the total energy in a given internal degree of freedom. In this algorithm, the modal energies are computed at each time step using a mode-tracking scheme and then the system is driven by an external driving force of desired frequency and amplitude. The rate and amount of energy exchange between the phonostat and the system is controlled by two distinct damping parameters. Two different schemes for controlling the external driving force amplitude are also presented. In order to test our algorithm, the method is applied initially to a simple anharmonic oscillator for which the role of various phonostat parameters can be carefully tested. We then apply the phonostat to a more realistic (10,0) carbon nanotube system and show how such an approach can be used to regulate energy of highly anharmonic modes.     

Regioselective synthesis of spiropyrrolidine/spiropyrrolizidine/spirothiazolidine-grafted macrocycles through 1,3-dipolar cycloaddition methodology

Synthesis of 13- and 16-membered macrocyclic enone with alkyl ether and triazole as a linker was achieved using intramolecular aldol condensation. The newly synthesized macrocyclic enone was successfully utilized as a dipolarophile in 1,3-dipolar cycloaddition (1,3-DC). The dipole generated from isatin/acenaphthenequinone with various secondary amino acids (sarcosine, l-proline, and thiazolidine-4-carboxylic acid) were reacted with macrocyclic enone to give a new class of spiropyrrolidine-grafted macrocycles in good yield (>85%). The structures were assigned by 2D NMR spectra and the regio- and stereochemical outcome of the cycloadducts were established by a single crystal X-ray analysis.     

Synthesis of acridinedione derived mono spiro-pyrrolidine/pyrrolizidine derivatives—a facile approach via intermolecular [3+2] cycloaddition reaction

A facile synthesis of acridinedione derived mono spiro-pyrrolidine and pyrrolizidine derivatives has been accomplished by 1,3-dipolar cycloaddition reaction. The O-acryloylacridinediones, as dipolarophiles reacted with azomethine ylide derived from di-/tri-ketones and sec-amino acids to give acridinedione derived mono spiropyrrolidine/pyrrolizidine derivatives in good yield.