Single step oxidative binding of antibodies to hydrazide-modified eupergit C

A single step periodate oxidative binding of glycoproteins to synthetic polymeric matrices is proposed. By this procedure, the glycoprotein to be immobilized is simultaneously mixed with sodium periodate and a hydrazide-containing matrix. The carbohydrate moieties of the protein are oxidized and react with matrix. The single step reaction is faster than the commonly-used multistep procedure and it allows conjugation of minute amounts of glycoproteins to the matrix.     

Chair/Twist-Boat Energy Gap in Monocyclic, Conformationally Unconstrained Polyalkylcyclohexanes

A conformational search procedure (HUNTER), in combination with the MM3(92) program, was used for the exploration of the conformational hypersurface of alkyl-substituted cyclohexanes and for the calculation of their chair/twist-boat (TB) energy gap. The systems studied were conformationally unconstrained polyalkylcyclohexanes (alkyl = methyl, ethyl, isopropyl, and tert-butyl) possessing either geminal and/or vicinal arrangements of the alkyl groups, but differing in the number of alkyl substituents and in their relative disposition (i.e., cis or trans). The calculations indicate that in 1,1,3,3,5,5-hexaisopropylcyclohexane the TB is the lowest energy form. Modification of the cis,trans relationship of vicinal alkyl groups changes the chair/TB energy gap, and in the minimum energy conformation of cis,trans,trans-1,2,3,4-tetraisopropylcyclohexane (23c) and cis,syn,cis-1,2,4,5-tetraisopropylcyclohexane (31c) the cyclohexyl ring adopts a TB conformation. The tetrasubstituted systems cis,syn,cis-1,2-diisopropyl-3,4-dimethylcyclohexane (46), cis,syn,cis-1,4-diisopropyl-2,5-dimethyl-cyclohexane (47), and cis,trans,trans-1,2-diisopropyl-3,4-dimethylcyclohexane (41) are the least crowded monocyclic unconstrained cyclohexanes found in which the TB conformation is of lower energy than the chair form. The present study indicates that two methyls and two isopropyl substituents are sufficient for stabilizing the TB form of a cyclohexyl ring relative to the chair form.     

Cross‐Platform Comparison of Therapeutic Delivery from Multilamellar Lipid‐Coated Polymer Nanoparticles

Significant efforts have been invested in finding a delivery system that can encapsulate and deliver therapeutics. Core–shell polymer‐lipid hybrid nanoparticles have been studied as a promising platform because of their mechanical stability, narrow size distribution, biocompatibility, and ability to co‐deliver diverse drugs. Here, novel core–shell nanoparticles based on a poly(lactic‐co‐glycolic acid) (PLGA) core and multilamellar lipid shell are designed, where the lipid bilayers are crosslinked between the two adjacent bilayers (PLGA‐ICMVs). The cross‐platform performance of the nanoparticles to other polymer‐lipid hybrid platforms is examined, including physicochemical characteristics, ability to encapsulate a variety of therapeutics, biocompatibility, and functionality as a vaccine delivery platform. Differential abilities of nanoparticle systems to encapsulate distinct pharmaceutics are observed, which suggest careful consideration of the platform chosen depending on the therapeutic agent and desired function. The novel PLGA‐ICMV platform herein demonstrates great potential in stably encapsulating water‐soluble agents and therefore is an attractive platform for therapeutic delivery.     

Charge distribution in a Kondo-correlated quantum dot

We report on direct measurement of charge and its distribution in a Kondo correlated quantum dot (QD). A noninvasive potential-sensitive detector, in proximity with a QD, reveals that, although the conductance of the QD is significantly enhanced as it enters the Kondo regime, the average charge remains unaffected. This demonstrates the separation between spin and charge degrees of freedom. We find, however, under certain conditions, an abrupt redistribution of charge in the QD, taking place with an onset of Kondo correlation. This suggests a correlation between the spin and charge degrees of freedom.     

Effective mass anisotropy of gamma electrons in GaAs/AlGaAs quantum wells

Resonant magnetotunneling in GaAs/Al(0.28)Ga0.72As double barrier structures is used to demonstrate that the effective mass of confined Gamma conduction electrons becomes anisotropic when an electric field is applied perpendicular to the interfaces. Although several authors have previously reported Gamma-related optical anisotropy, this is the first example of a corresponding electrical anisotropy. The results are explained using a quantum mechanical model involving interface band mixing that contains additional features not found in the optical case.     

Self-organizing lists and independent references: A statistical synergy

Let R₁,…, R_n be a linear list of n elements. We assume the independent reference model, with a fixed but unknown access probability vector. We survey briefly the problem of reorganizing the list dynamically, on the basis of accrued references, with the objective of minimizing the expected access cost. The counter scheme (CS) is known to be asymptotically optimal for this purpose. The paper explores the CS, with the aim of reducing its storage requirements. We start with a detailed exposition of its cost function and then point out that it interacts with the access model to produce some remarkable synergistic effects. These make it possible to use very effective “truncated versions” of the CS, which have very modest space requirements. The versions we consider are: (i) the “limited-counters scheme”, which bounds each of the frequency counters to a maximal value c; (ii) the original CS with a bound on the number of references during which the scheme is active. The bound is chosen so as to achieve a desired level of performance compared with the optimal policy.     

Measurements of Kondo and spin splitting in single-electron transistors

We measure the spin splitting in a magnetic field B of localized states in single-electron transistors using a new method, inelastic spin-flip cotunneling. Because it involves only internal excitations, this technique gives the most precise value of the Zeeman energy Delta=/g/mu(B)B. In the same devices we also measure the splitting with B of the Kondo peak in differential conductance. The Kondo splitting appears only above a threshold field as predicted by theory. However, the magnitude of the Kondo splitting at high fields exceeds 2/g/mu(B)B in disagreement with theory.     

A fast, high-yield preparation of vicinal dinitro compounds using HOF.CH3CN

HOF.CH3CN, a very efficient oxygen-transfer agent, was reacted with various aliphatic and aromatic vicinal diamino compounds. The products were the rare, vicinal dinitro derivatives formed in excellent yields and short reaction times. This is in contrast to other oxygen-transfer agents which tend to break the central C-C bond of the diamino precursor. This reaction was also used for making dinitro compounds with all four oxygens, being the [18]O isotope.     

Disproportionation reactions between alkyl and fluoroalkyl radicals. IV. Pentafluoroethyl and ethyl radicals

A new determination of the disproportionation/combination ratio for C₂F₅ and C₂H₅ radicals gives a value of Δ(C₂F₅, C₂H₅) = 0.24 ± 0.02, independent of temperature. The cross-combination ratio for the two radicals was found to increase with temperature and the significance of this is discussed in evaluating Δ.