Efficient modification of RNA by porphyrin cation photochemistry: monitoring the folding of coaxially stacked RNA helices in tRNA(Phe) and the human immunodeficiency virus type 1 rev response element RNA.

Coaxially stacked RNA helices are a determined of RNA tertiary structure, but their presence is rarely detected using conventional chemical modification methods. In this report we describe a porphyrin ion photoreaction that enables one to monitor RNA stacking interactions and the folding of coaxially stacked RNA helices. The porphyrin cations meso-tetrakis(4-N-methylpyridyl)porphine, meso-tetrakis-(para-N-trimethylanilinium)porphine, and meso-tetrakis(2-N-methylpyridyl)porphine were used to characterize tRNA(Phe) and the human immunodeficiency virus type-I Rev response element RNA. Nucleosides at the bases of contiguous RNA helices in each RNA are efficiently modified by the porphyrin cations following irradiation of porphyrin-RNA mixtures. These photomodifications are markedly reduced for RNA equilibrated in ionic buffers that lead to enhanced stabilization of coaxially stacked helices. The porphyrin cation photoreaction specifically modifies G18, G20, and G34 in the tRNA folding produced by Mg(II). These nucleobases are exposed to solvent in the native tRNA structure and thus available to stack with solvent-borne porphyrin molecules. The describe porphyrin cation photochemical method provides a novel approach to study the solvent accessibility of nucleobases in RNA structure and to monitor the folding of coaxially stacked helices in RNA.

Structure-specific binding and photosensitized cleavage of branched DNA three-way junction complexes by cationic porphyrins.

The interactions of cationic porphyrins with DNA oligonucleotides that form branched, three-way junction complexes (TWJ) were investigated using native gel electrophoresis, absorption spectroscopy and photochemical probing using DNA sequencing techniques. Meso-tetra(para-N- trimethylaniliniumyl)porphine (TMAP), meso-tetra(4-N-methylpyridiniumyl)porphine (T4MPyP) and meso-tetra(3-N-methylpyridiniumyl)porphine(T3MPyP) were found to bind more tightly to DNA TWJ than to DNA duplexes. The binding to the junction DNA persists at high ionic strength, conditions that greatly decrease porphyrin binding affinity to duplex DNA. THe TWJ DNA binding sites of TMAP and T4MPyP were localized to the junction region based on the observation of site- and structure-specific, porphyrin-sensitized photodamage to guanosine residues flanking the junction region.

Rapid diagnosis by buffy coat smear of disseminated Mycobacterium avium complex infection in patients with acquired immunodeficiency syndrome.

A smear of the buffy coat of peripheral blood for acid-fast bacilli was assessed for sensitivity and specificity in the diagnosis of disseminated Mycobacterium avium complex (MAC) infection in acquired immunodeficiency syndrome (AIDS) patients. Seventeen AIDS patients with blood cultures positive for MAC had simultaneous quantitative blood cultures and buffy coat smears performed, as did 4 patients later proven not to have disseminated MAC. The sensitivity of the buffy coat smear for the detection of MAC was 35%, the specificity was 100%, the positive predictive value was 100%, and the negative predictive value was 22%. We conclude that the buffy coat smear is a rapid, simple, and specific method of diagnosis of disseminated MAC infection in AIDS patients, although it is not very sensitive.

[Progressive Duchenne muscular dystrophy: general practice aspects of diagnostic assessment]. / Progressive Muskeldystrophie Duchenne: Praxis der Diagnosefindung.

The analysis of 57 cases of Duchenne muscular dystrophy (DMD) from W.-Germany outlined an average delay in motor development with an extended period of time between learning to stand and to walk. 33 patients could not walk when they were 16 months old. At the age of 27 months people without medical training generally noticed first symptoms. Unexpectedly often quantitative deficiencies in movements became evident. On average 26 months passed until DMD was diagnosed. To improve the situation, the authors propose a selective screening of boys who are not able to walk without help when they are 16 months old (90th percentile for healthy children).