Solid-Phase Synthesis of an Insect Pyrokinin Analog Incorporating an Imidazoline Ring as Isosteric Replacement of a trans Peptide Bond

A facile solid-phase synthetic method for incorporating the imidazoline ring motif, a surrogate for a trans peptide bond, into bioactive peptides is reported. The example described is the synthesis of an imidazoline peptidomimetic analog of an insect pyrokinin neuropeptide via a cyclization reaction of an iminium salt generated from the preceding amino acid and 2,4-diaminopropanoic acid (Dap).     

Coordination ability of insect kinin analogs

Spectroscopic data, including electronic absorption, CD and EPR results, as well as theoretical calculations have shown that the insertion of 4-aminopyroglutamate, a novel cis-peptide bond mimic, in the insect kinin peptide leads to an effective ligand towards Cu(II) ions at basic pH ranges. The 4-aminopyroglutamate motif induces a specific peptide conformation which favors the formation of one or two five-membered chelating rings stabilizing a bent structure, with the coordination of 3N-type or 4N-type in the metallopeptide molecule involving in metal bonding C-terminal of modified peptide. It is worth noting that the copper(II) bonding does not undergo hydrolysis even at a very high pH range.     

Radial vibrations of composite piezoelectric ceramic disks

A theory is developed for the radial vibrations of thin disks composed of several piezoelectric ceramic materials bonded at their cylindrical interfaces. Closed type solutions are obtained for the resonant and antiresonant frequency equations, and numerical results are presented for various steel/PZT-4 composite disks. The frequency spectrums and corresponding electromechanical coupling factors are found to be quite sensitive to the heterogeneity of the considered piezoelectric systems.     

The fast-time instability of diffusion flames

A diffusion flame burns with varying intensity if the pressure is varied, and the nonlinear steady-state response is typically S-shaped; that is, multiple solutions exist for some range of pressure. The physically relevant branch can only be determined by unsteady analyses, and in this paper we discuss the stability of a large class of diffusion flames when the activation energy characterizing the reaction rate is large. Specifically, we examine the evolution from the stationary solution on a time scale so short that changes are confined to the thin flame sheet where all the reaction occurs. In this region time derivatives are added to the steady state equations, which otherwise describe a balance between diffusion and chemical reaction. The stability problem is then reduced to the determination of the spectrum of Schrödinger's equation, defined on the infinite interval, with a potential that is not of one sign on this interval. In this way certain conclusions about extinction are drawn and certain past misconceptions are clarified.     

Some singular,nonlinear differential equations arising in boundary layer theory

The nonlinear, second-order differential equation which describes boundary layer flow when Crocco variables are employed is examined under several different endpoint conditions. Uniqueness and analyticity are established for boundary conditions corresponding to flow behind weak expansion and shock waves and for the flow above a moving conveyor belt.     

o-Hydroxyphenylureas. Intermediates in the urea fusion synthesis of 2-benzoxazolinones

o-Hydroxyphenylureas have been identified as intermediates in the urea fusion synthesis of 2-benzoxazolinones. The pyrolysis of these intermediates represents a new alternate synthesis of the benzoxazolinone ring system.