Equivalence of regularity for the Bergman projection and the\bar \partial-neumann operator

A necessary and sufficient condition for regularity of the -Neumann operator on (0,q)-forms in a smooth bounded pseudoconvex domain in Cⁿ is that the orthogonal projections onto -closed forms of degrees (0,q−1), (0,q), and (0,q+1) all be regular. The first author partially supported by NSF Grant DMS-8701038     

(1-Adamantanethio)pyridines and tetrahydropyridines from the reaction of 1-adamantanethiol with pyridine I-oxide in acetic anhydride

The reaction of pyridine 1-oxide with 1-adamantanethiol in acetic anhydride produced a mixture of 2- and 3-(1-adamantanethio)pyridines, 1-aeetyl-2-(1-adamantanethio)-3-hydroxy-4-acetoxy-1,2,3,4-telrahydropyridine and the corresponding 3-acetoxyderivative. Pure substances were separated by means of column chromatography on alumina. The tetrahydropyridines were identified by means of their proton magnetic and mass spectra. 4-(1-Adamantanethio)pyridine was synthesized from 4-chloropyridinc and 1-adamantanethiol. The three isomeric (1-adamantanethio)-pyridines were, each, cleaved by concentrated hydrochloric acid to give 1-chloroadamantane and the corresponding pyridinethiol.     

Non-chair six-membered-ring conformations. Preference for a twist-boat (or skew) structure in α- -sorbopyranose derivatives

The conformational preferences for 2,3-O-isopropylidene-α- -sorbopyranose derivatives 3–6 were determined by using ¹H NMR data and empirical force field calculations. Proton NMR studies of 3–6 indicate that a twist-boat (or skew) conformation (³S₀) prevails over possible chair forms for each compound. Force-field calculations (MM2, MNDO, AM1) on a model 2,3-O-isopropylidene-α- -sorbopyranose system (18) indicate that the ³S₀ conformation is among the low-energy structures. X-Ray crystallographic analysis of α- -sorbopyranose sulfamate 3, a compound with potent anticonvulsant activity, demonstrates that the ³S₀ skew conformation is manifested in the solid state, as well.     

Comparative inhibition by substrate analogues 3-methoxy- and 3-hydroxydesaminokynurenine and an improved 3 step purification of recombinant human kynureninase.

Background  

Kynureninase is a key enzyme on the kynurenine pathway of tryptophan metabolism. One of the end products of the pathway is the neurotoxin quinolinic acid which appears to be responsible for neuronal cell death in a number of important neurological diseases. This makes kynureninase a possible therapeutic target for diseases such as Huntington's, Alzheimer's and AIDS related dementia, and the development of potent inhibitors an important research aim.     

Variable step molecular dynamics: An exploratory technique for peptides with fixed geometry

A new algorithm is presented for performing molecular dynamics simulations of peptides with fixed geometry, with the aim of simulating conformational changes and of exploring conformational space. The principle of the method is to expand the potential energy as a Taylor's series in the coordinates around the current point, retaining the force and its first two derivatives, and obtain a series solution of the resulting differential equations using a method due to Lyapunov. By choosing the time step so that the second term in the series is small compared to the first, the true solution can in principle be approximated to any desired degree of accuracy. The algorithm has been used to solve numerically Lagrange's equations of motion for N-acetyl alanine amide and N-acetyl methionide amide, regarded as fixed at their C-termini, under the influence of the ECEPP/2 potential energy function, and time steps of 15–30 fsec have been achieved with little variation in the total energy. Possible directions for future development are discussed.     

Photolithographic synthesis of cyclic peptide arrays using a differential deprotection strategy

We report here a strategy for the photolithographic synthesis of diverse, spatially addressable arrays of cyclic peptides which employs a differential deprotection strategy for the combinatorial addition of side chains to a pre-fabricated cyclic core.     

Dilute solution properties of a polyurethane. I. Linear polymers

A linear polyurethane of high molecular weight was prepared in solution by the polyaddition of equimolar amounts of ethylene glycol and methylene bis(4-phenyl isocyanate). The polymer was fractionated by using a direct sequential extraction procedure, with a solvent–nonsolvent system consisting of N,N′-dimethylformamide (DMF) and acetone (A). The resulting fractions were characterized by viscosity and lightscattering measurements. The relationship between the intrinsic viscosity and molecular weight was found in DMF at 25°C. to be [η] = 3.64 × 10^?4M^0.71. The unperturbed polymer chain dimensions were determined from intrinsic viscosity measurements carried out under experimentally determined theta conditions.     

Electron-transfer polymers. XXIX. Copolymerizability of vinylhydroquinone derivatives

Ten vinylhydroquinone and one vinyl resorcinol derivatives are compared, particularly with respect to NMR spectra and copolymerizability with styrene. They are vinylhydroquinone dimethyl ether (I), vinyl-O,O′-bis(1-ethoxyethyl)hydroquinone (II), vinylhydroquinone di(2-pentyl)ether (III), 4-vinyl resorcinol bismethoxymethyl ether (IV), 2-vinyl-5-methylhydroquinone dimethyl ether (V), 2-vinyl-5-methyl-O,O′-bis(1-ethoxyethyl)hydroquinone (VI), 2-vinyl-6-methylhydroquinone dimethyl ether (VII), 2-vinyl-5-tert-butylhydroquinone dimethyl ether (VIII), 2-vinyl-5-chlorohydroquinone dimethyl ether (IX), 2-vinyl-3,6-dimethylhydroquinone dimethyl ether (X), and 2-vinyl-3,5,6-trimethylhydroquinone dimethyl ether (XI). All the vinyl protons have almost the same coupling constants. Though subtle distinctions are found among all the spectra, they can in general be put into two groups on the basis of the chemical shifts. Let the hydrogen on carbon-1 of the vinyl group be A, the hydrogen cis to A be B the hydrogen trans to A be C, then in the first group, (I) through (IX), the chemical shifts (τ) are (A) 3.02 ± 0.08, (C) 4.41 ± 0.05, and (B) 4.87 ± 0.07, and in the second group, (X) and (XI), they are (A) 3.30 ± 0.03, (C) 4.49 ± 0.01, and (B) 4.59 ± 0.03. It is supposed that in (X) and (XI) the vinyl group is out of the plane of the ring, because of the two ortho substituents, and this conformation is reflected in the NMR data. Ultraviolet spectra are consonant with this interpretation, since the λ_max of (X) and (XI) correspond closely with those of nonvinyl reference compounds, while those of (II), (V), and (VIII) are shifted to longer wavelengths. When these compounds are copolymerized separately with styrene, the behaviors are classifiable into the following three groups, where r₁ and r₂ are monomer reactivity ratios with styrene as the first monomer: (i) r₁ < 1 and r₂ < 1 for compounds (II) and (III) and the reference compound O,O′-dibenzoylvinylhydroquinone, (ii) r₁ < 1 and r₂ > 1 for compounds (I), (V), (VII), (VIII), (IX), and (iii) r₁ > 1 and r₂ = 0 for compounds (X) and (XI). These behaviors are correlated with the effect of electronegativity of groups on the stability of the radical at the growing end of the chain and with the simultaneous effects of steric hindrance.