Alkoxy-, acyloxy-, and bromomethylation of resorcinarenes

Reaction of resorcinarene octols with tris-hydroxymethylmethylamine (TRIS), formaldehyde, and alcohols results in tetraalkoxymethylation of the resorcinol rings. Harsh acylation of aminomethylated resorcinarenes with acid anhydrides leads to the complete acylation of eight hydroxyls and substitution of the amino versus acyloxy groups. Acyloxymethylated resorcinarene 6b can be transformed into a tetrabromomethylated derivative 7 through the reaction with HBr in acetic acid.     

Elucidation of the chiral recognition mechanism of cinchona alkaloid carbamate-type receptors for 3,5-dinitrobenzoyl amino acids

A cinchona alkaloid having extraordinary chiral discriminatory powers (alpha = 32.6 for dinitrobenzoyl leucine) is developed as a chiral stationary phase (CSP) for chromatography. An explanation of how chiral discrimination takes place is presented. Using a soluble analogue of the CSP, we found that NMR spectrometry indicates that 1:1 complexes exist for both optical isomers interacting with the CSP, that the free base form of the CSP exists in an open/closed ratio of 35/65 but that the protonated, bound-state form is exclusively in the anti-open conformation, and that significant intermolecular NOEs exist for the more stable diastereomeric complex but not for the less stable complex. Stochastic molecular dynamics simulations were carried out in solvents of low and high dielectric. The chromatographic retention orders and free energy differences of analyte binding to CSP were reproduced computationally as were the observed intra- and intermolecular NOEs. Data from the simulation were used to evaluate the intermolecular forces responsible for analyte binding as well as to discern fragments of the CSP doing most of the work of holding the complexes together. The enantiodifferentiating forces and the parts of the CSP most responsible for chiral discrimination are described. Moments of distributions of key dihedral angles and distances between centroids were used to assess the relative rigidity of the competing diastereomeric complexes. Simultaneous multiple-contact ion-pairing, hydrogen bonding, and pi-stacking are possible for the longer retained enantiomer only. An X-ray crystallographic study of the more stable complex confirms the conclusions derived from chromatography, NMR spectroscopy, and molecular modeling.     

Unitary and Antiunitary Operators Mapping Vectors to Parallel or to Orthogonal Ones, with Applications to Symmetry Transformations

Unitary and antiunitary operators which map vectors either to parallel or to orthogonal vectors are characterized. As an application the results are used to show that symmetry transformations induced by real functions are identity transformations.     

Solvent‐Free Ball‐Milling Subcomponent Synthesis of Metallosupramolecular Complexes

Subcomponent self‐assembly from components A , B , C , D , and Fe²⁺ under solvent‐free conditions by self‐sorting leads to the construction of three structurally different metallosupramolecular iron(II) complexes. Under carefully selected ball‐milling conditions, tetranuclear [Fe₄( AD ₂)₆]^4? 22‐component cage 1 , dinuclear [Fe₂( BD ₂)₃]^2? 11‐component helicate 2 , and 5‐component mononuclear [Fe( CD ₃)]²⁺ complex 3 were prepared simultaneously in a one‐pot reaction from 38 components. Through subcomponent substitution reaction by adding subcomponent B , the [Fe₄( AD ₂)₆]^4? cage converts quantitatively to the [Fe₂( BD ₂)₃]^2? helicate, which, in turn, upon addition of subcomponent C , transforms to [Fe( CD ₃)]²⁺, following the hierarchical preference based on the thermodynamic stability of the complexes.     

Standoff alpha radiation detection for hot cell imaging and crime scene investigation

Optical Review - This paper presents the remote detection of alpha contamination in a nuclear facility. Alpha-active material in a shielded nuclear radiation containment chamber has been localized...     

Characterization of a cylindrical rod by inversion of acoustic scattering data

In this paper, a new approach is proposed for nondestructive characterization of immersed and embedded isotropic rod-shaped samples by inversion of acoustic scattering data. The normal mode expansion technique is used for modelling the scattered field and the compression incident and compression scattered waves are considered. Genetic algorithm is the inversion technique used for estimating the elastic wave velocities and density of the rods from their measured backscattered pressure spectrum. The inversion technique is capable of computing the parameter values that best fit a particular set of data. A perturbation study is conducted on the sensitivity of the resonance frequencies to changes in elastic properties and density of the rods. The numerical results indicate that proper selection of resonance frequencies leads to accurate measurement of elastic constants and density. The proposed approach showed very good convergence and the results obtained were found to agree very well with available data.     

Effective Solubilization Procedure for Analysis of Silkworm Hemolymph Proteins by Two-Dimensional Gel Electrophoresis

The outstanding capability of two-dimensional gel electrophoresis in separating all types of proteins basically depends on the efficiency of sample preparation. Sample preparation is one of the most critical steps in two-dimensional gel electrophoresis. Unfortunately, due to severe solubility, resolution of protein on gel is usually hampered, and thus, analysis remains a difficult task. However, technically several problems are generally encountered during protein extraction and isoelectric focusing. In the present investigation, we emphasized on evaluation and comparison of six different protein solubilization methods intended for resolving and analyzing silkworm hemolymph proteins by two-dimensional gel electrophoresis. Our findings revealed that the buffer composition of 8 M urea, 4 % 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate, 40 mM Tris base, 65 mM dithiothreitol, and 0.2 % ampholyte can effectively solubilize and yields maximum protein spots.