Dissociation of heme from gaseous myoglobin ions studied by infrared multiphoton dissociation spectroscopy and Fourier-transform ion cyclotron resonance mass spectrometry

Detachment of heme prosthetic groups from gaseous myoglobin ions has been studied by collision-induced dissociation and infrared multiphoton dissociation in combination with Fourier-transform ion cyclotron resonance mass spectrometry. Multiply charged holomyoglobin ions (hMbn+) were generated by electrospray ionization and transferred to an ion cyclotron resonance cell, where the ions of interest were isolated and fragmented by either collision with Ar atoms or irradiation with 3 mum photons, producing apomyoglobin ions (aMbn+). Both charged heme loss (with [Fe(III)-heme]+ and aMb(n-1)+ as the products) and neutral heme loss (with [Fe(II)-heme] and aMbn+ as the products) were detected concurrently for hMbn+ produced from a myoglobin solution pretreated with reducing reagents. By reference to Ea = 0.9 eV determined by blackbody infrared radiative dissociation for charged heme loss of ferric hMbn+, an activation energy of 1.1 eV was deduced for neutral heme loss of ferrous hMbn+ with n = 9 and 10.     

Global error bounds with fractional exponents

Using the partial order induced by a proper weakly lower semicontinuous function on a reflexive Banach space X we give a sufficient condition for f to have error bounds with fractional exponents. Application is given to identify the set of such exponents for quadratic functions. Received: August 20, 1999 / Accepted: March 20, 2000?Published online July 20, 2000     

Synthesis and Study of an N,N‐Disubstituted 4‐[(4‐Aminophenyl)diazenyl]benzaldehyde

An N,N‐disubstituted 4‐[(4‐aminophenyl)diazenyl]benzaldehyde (‘azo dye') with nematic phase was synthesized by reaction of the phenylpiperazine derivative with the formylbenzenediazonium salt. The salt was prepared by a simplified reaction of poly(aminobenzaldehyde) with NaNO₂ in the presence of HBF₄. The azo dye was further studied by crystallography. On the basis of molecular stacking identified from crystallography, the molecular modeling was carried out to explore the molecular interactions, and it was found that the attraction of two coplanar molecules with side‐to‐side contact is favored, and a nematic phase is thus formed during the thermal process.     

Ester–amide exchange in blends of liquid‐crystalline copolyester and polyamide 6

The kinetics of the ester–amide exchange in solution blends of the random liquid‐crystalline polyester copoly(oxybenzoate‐terephthalate) (P64) and polyamide 6 (PA6) were studied with carbon nuclear magnetic resonance. With second‐order reversible reactions assumed, the activation energy of the ester–amide interchange in 30/70, 50/50, and 70/30 P64/PA6 blends were all about 24.0 kcal/mol. The pre‐exponential factors for the ester–amide exchange in 30/70, 50/50, and 70/30 P64/PA6 blends were 2.01 × 10¹¹, 2.59 × 10¹⁰, and 2.74 × 10¹² min⁻¹, respectively. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2124–2135, 2000