Chirality of aromatic bis-imides from their circular dichroism spectra

It is demonstrated that chirality of molecules composed of 1,2,4, 5-benzenetetracarboxydiimide (pyromellitic diimide) or 1,4,5, 8-naphthalenetetracarboxydiimide units is reflected by their exciton Cotton effects. The analysis is based on the calculated (ZINDO/S) excited states of the model diimide chromophores 1a and 2a. Rotation of the diimide chromophores around the C-N bond in diimides 3-5 is evaluated from the dynamic (1)H NMR data. A comparison of chiroptical properties of bis-diimides 3-5 with the CD spectra of bis-imides 6-8 is also presented. Copyright 2000 Wiley-Liss, Inc.

1,8-Naphthalimides as Stereochemical Probes for Chiral Amines: A Study of Electronic Transitions and Exciton Coupling.

The absorption and magnetic circular dichroism (MCD) spectra of 1,8-naphthalimide are analyzed in terms of the number of contributing electronic transitions and their polarization. The experimental results are supported by semiempirical INDO/S calculations. It is demonstrated that the strongly allowed, pi --> pi naphthalene transition of the 1,8-naphthalimide chromophore located at 231 nm is perfectly suited for absolute configuration assignments of amine derivatives on the basis of the bichromophoric exciton coupling. Both degenerate (bis-1,8-naphthalimide) and nondegenerate (1,8-naphthalimide-phthalimide, 1,8-naphthalimide-phenyl, or 1,8-naphthalimide-benzoate) couplings were studied. In the latter case, the sign of the exciton Cotton effect was opposite to the sign of the degenerate exciton Cotton effect for the same absolute configuration. An extension of the application of the exciton coupling to the 264 nm pi --> pi transition of 1,9-anthraimide is also shown.

Disseminated neocortical and subcortical encephalopathy (DNSE) with widespread activation of brain macrophages: a new dementia disorder? Autopsy reports of two postmenopausal women from families with mitochondrial DNA mutations.

In this study we present 2 postmenopausal women who showed clinical symptoms that resembled those of a rather well-defined group of vascular dementia disorders, termed subcortical dementia (Binswanger disease, CADASIL). Patient 1 exhibited mitochondrial DNA (mtDNA) variants in the ND5 gene at position 13,708 and the Cytb gene at position 15,257. These DNA variants have been described in a number of neurologic disorders, but their pathogenetic potential is unclear. Patient 2 showed the same DNA alterations and an additional mtDNA variant at position 15,812 in the Cytb gene. The principal neurohistologic features of the 2 atrophic brains presented here include: subtotal selective neuronal cell loss in the cortex and, to a lesser degree, in the basal ganglia (claustrum, putamen, globus pallidus), sparing palaeocortex and periarchaeocortex, and a very characteristic and diagnostic feature was detachment of astrocytic processes from capillary walls resulting in pericapillary space formation. These pericapillary spaces were partially filled with macrophages. The spaces were not associated with total breakdown of the blood vessel walls as demonstrated by the absence of erythrocytes, lymphocytes, or polymorphonuclear leukocytes outside the vascular bed of the brain; progressive subcortical encephalopathy, as it is seen in subcortical dementia (Binswanger), but lacking arterial lipohyalinosis. The cerebral grey and white matter revealed cuffing of arteries and arterioles by adventitial macrophages. The neocortical and subcortical changes were accompanied by myriads of activated macrophages filled with lipids. The pathology of our 2 cases differs from that of other neurodegenerative disorders and we suggest the term of "disseminated neocortical and subcortical encephalopathy (DNSE) with widespread activation of brain macrophages".

Association of the LHON 13,708 and 15,257 mitochondrial DNA mutations with neurodegenerative diseases distinct from LHON.

300 patients suffering from neurodegenerative diseases distinct from Leber hereditary optic neuropathy (LHON) were screened for the presence of mitochondrial DNA mutations. We report on nine patients, eight female and one male, who all harboured mutations at positions 13,708 and 15,257 of the mitochondrial DNA. Both mutations have previously been claimed to be associated with LHON. Based on our results, these mutations occur in a number of different neurodegenerative diseases and therefore cannot be regarded as "LHON" mutations.

A fluorescence-microscopic and flow-cytometric study of HeLa cells with an experimentally induced respiratory deficiency.

HeLa cells, cultured over a long period in a medium containing low doses of ethidiumbromide, were used as a model system for flow-cytometric detection of human cells with impaired mitochondrial respiratory function. Based on laserscan and flowcytometric analysis after rhodamine 123 staining, the mitochondrial membrane potential of respiratory deficient cells seems unchanged as compared to control cells. Maintenance of this membrane potential in respiration-impaired cells requires glycolytic ATP generation, as transient inhibition of glycolysis by sodium fluoride affects rhodamine 123 accumulation in ethidiumbromide-treated cells, but not in control cells. We present a protocol which allows the detection and separation of respiratory deficient cells by flow cytometry.

Flow cytometry as a tool to discriminate respiratory-competent and respiratory-deficient yeast cells.

The cationic lipophilic dye Rhodamine 123 (Rh123) is selectively enriched in mitochondria in a membrane potential-dependent manner. Application of drugs which interfere with the electron flow of the respiratory chain lead to a severe reduction of mitochondrial dye uptake. In this communication we show that the same effect is observed after Rh123-staining of respiratory-deficient yeast mutants. Based on this observation we used flow cytometry to discriminate respiratory-competent and respiratory-deficient yeast cells. Combined with a cell sorter we were able to selectively enrich respiring and non-respiring yeast cells, respectively, from a mixture of cells.