Photoaffinity labeling on magnetic microspheres (PALMm) methodology for topographic mapping: preparation of PALMm reagents and demonstration of biochemical relevance

Photoaffinity labeling (PAL) is a technique widely used for identifying the binding-site within proteins. Although the classic method is both versatile and powerful, it suffers significant disadvantages, such as the need to radiolabel the PAL ligand, and the need to conduct highly complicated separations of both the labeled protein and the labeled peptides derived from it. Here, we propose a novel and universal methodology--Photo-Affinity Labeling on Magnetic microspheres (PALMm) designed to simplify and shorten the PAL protocol. In this context, we describe the preparation of PALMm reagents and the evaluation of their biochemical relevance regarding two ATP-binding enzymes: hexokinase and apyrase.     

Novel method for incorporating the CHF(2) group into organic molecules using BrF(3)

2-Alkyl-1,3-dithiane derivatives, easily made from alkyl bromides and the parent 1,3-dithiane, were reacted with BrF(3) to form the corresponding 1,1-difluoromethyl alkanes (RCHF(2)) in 60-75% yield. The reaction proceeds well with primary alkyl halides. The limiting step for secondary alkyl halides is the relatively low yield of the dithiane preparation. The two sulfur atoms of the dithiane are essential for the reaction.     

An affine PI Hopf algebra not finite over a normal commutative Hopf subalgebra

In formulating a generalized framework to study certain noncommutative algebras naturally arising in representation theory, K. A. Brown asked if every finitely generated Hopf algebra satisfying a polynomial identity was finite over a normal commutative Hopf subalgebra. In this note we show that Radford's biproduct, applied to the enveloping algebra of the Lie superalgebra , provides a noetherian prime counterexample.

     

Gaussian Closure of One-Dimensional Unsaturated Flow in Randomly Heterogeneous Soils

We propose a new method for the solution of stochastic unsaturated flow problems in randomly heterogeneous soils which avoids linearizing the governing flow equations or the soil constitutive relations, and places no theoretical limit on the variance of constitutive parameters. The proposed method applies to a broad class of soils with flow properties that scale according to a linearly separable model provided the dimensionless pressure head has a near-Gaussian distribution. Upon treating as a multivariate Gaussian function, we obtain a closed system of coupled nonlinear differential equations for the first and second moments of pressure head. We apply this Gaussian closure to steady-state unsaturated flow through a randomly stratified soil with hydraulic conductivity that varies exponentially with where =(1/) is dimensional pressure head and is a random field with given statistical properties. In one-dimensional media, we obtain good agreement between Gaussian closure and Monte Carlo results for the mean and variance of over a wide range of parameters provided that the spatial variability of is small. We then provide an outline of how the technique can be extended to two- and three-dimensional flow domains. Our solution provides considerable insight into the analytical behavior of the stochastic flow problem.     

Van der Waals interactions between surfaces of biological interest

Microscopic and macroscopic approaches to calculations of long-range Van der Waals interactions between bodies are reviewed. Expressions are presented for various geometries, including planar-layered structures, sheathed spheres and rods. Retardation effects are shown to reduce dispersion interactions in a similar fashion in both approaches. Pair summation procedure gives 10–25% greater values of dispersion interactions than the macroscopic approach. Orientation effects, previously neglected in microscopic approaches are strongly dependent on many-body effects. When orientation effects are included in a pair summation procedure, its calculated values are close to those calculated with the macroscopic approach.Experimentally determined force values are in agreement with calculated ones for distances of separation above 15 Å in vacuum. In general, the theory is insufficient for yielding forces at distances of separation below 20 Å in water.Determination of Van der Waals parameters from refractive indices of pure liquids and solutions is described. Within 5%, dispersion coefficients are independent of concentration of solution, and isotropic electronic polarizabilities agree with those obtained by the addition of bond polarizabilities. Van der Waals parameters of several major components of cellular surfaces and intercellular media are arranged according to an ascending sequence: water<alkanes<phospholipids<proteins and cholesterol<sugars.Variations in compositions, distances of separation, and layer thicknesses are considered in the calculation of the interactions between cellular surfaces, both in planar and spherical systems, including phospholipid vesicles. In planar-cellular systems, Hamaker coefficients vary between 4 x 10^-15 and 6 x 10^-14 erg; at 50 Å distance of separation the free energies and forces are 210 to 1600 kT/μm², and 4 x 10^-5 to 3 x 10^-4 dynes/μm² respectively. The total potential curve, including electrostatic interactions, is calculated and the questions of cellular adhesion and fusion of phospholipid vesicles are discussed.     

Coulomb energies and charge asymmetry of nuclear forces

Charge-symmetry-breaking potentials suggested in the literature to resolve the discrepancy between calculated Coulomb energy differences of analog states and the experimental values, are considered in detail. We calculate the contributions of these potentials to the ground state energy differences of the mirror nuclei ³He³H, ¹⁵O¹⁵N, ¹⁷F¹⁷O, ³⁹Ca³⁹K and ⁴¹Sc⁴¹Ca. It turns out, due to the short range character of these symmetry-breaking potentials, that their inclusion may resolve the ³He³H difficulty but not the ⁴¹Sc⁴¹Ca discrepancy.     

Searching for photochromic liquid crystals Spironaphthoxazine substituted with a mesogenic group

A number of photochromic spiropyrans and spirooxazines containing mesogenic groups were synthesized. Only one of them, spiro-indoline-naphthoxazine with mesogenic substituent, 4-(4-heptylbenzoyloxy)benzoyloxy in 5-position, revealed mesomorphic properties. Its phase behaviour, photochromism and alignment in the electric field was investigated. A structure of the mesophase is discussed.     

Cobalt carbonyl catalyzed reactions of disulfides: Carbonylation to thioesters and desulfurization to sulfides

aromatic and benzylic disulfides react with carbon monoxide and a catalytic amount of cobalt carbonyl to give thioesters and carbonyl sulfide, while the presence of t-butyl peroxide results in the formation of sulfides in high yields.