Heme-heme interactions in tetramers and dimers of hemoglobin subunits: DeVoe theory calculations

Detectable exciton couplets arising from heme-heme interactions in the hemoglobin (Hb) tetramers of HbO(2) and deoxyHb were predicted by DeVoe theory. This prediction was supported by the observation of an exciton couplet in the CD difference spectrum between the Hb tetramer and the alphabeta dimer of HbCO. In this paper, DeVoe theory is used to calculate the heme-heme interactions in the CO complex of the Hb tetramer (alpha(2)beta(2)) and dimer (alphabeta), the systems studied by Goldbeck et al. The couplet strength of the resulting theoretical CD difference spectrum agrees well with experiment, thus confirming that heme-heme interactions contribute significantly to the CD of HbCO. Given that the heme-heme distances in HbCO are 25 A and more, it is highly likely that heme-heme interactions also contribute significantly to the CD of other multi-heme proteins, e.g., cytochrome c(3), cytochrome oxidase, cytochrome bc(1), etc., where the hemes are in closer proximity.

Structural determinations by circular dichroism spectra analysis using coupled oscillator methods: An update of the applications of the DeVoe polarizability model

The exciton (coupled oscillator) model for optical activity is a very useful and powerful method which allows to analyze a circular dichroism (CD) spectrum in a nonempirical way, arriving at a safe assignment of the absolute configuration of organic and inorganic compounds. Usually in this model only the exciton coupling of two electrically allowed transitions (oscillators) is taken into account. This approach has the important advantage of an easy application but, sometimes, it may lead to wrong results. Thus, in this review article a more general treatment, which allows considering the simultaneous coupling of several oscillators, i.e., the DeVoe model, is presented and critically analyzed, discussing in detail the latest applications reported in the literature. In the authors opinion, since the DeVoe model joins generality and reliability requiring an almost negligible computational effort, it represents the method of choice for stereochemical assignments, even by nonspecialists.

Chemoenzymatic synthesis and properties of Schiff bases containing (R)-1-(9-anthryl)ethylamine

Racemic 1-(9-anthryl)ethylamine (10), obtained in 70% overall yield from commercial 9-cyanoanthracene, was kinetically resolved by the Candida antarctica A lipase-catalyzed acetylation with isopropyl acetate as acyl donor, affording (R)-(+)-10 with 95.8% enantiomeric excess (e.e.) (E-value 43.5), which afforded Schiff bases (R)-4 and(R)-8. (1)H-NMR, CD, and MM2 calculations offer a consistent picture of the conformational properties of these potential ligands and an explanation for the limited enhancement of enantioselectivity in cyclopropanation of styrene by their Cu(I) complexes, as compared with previously studied ligands in this series.