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  • 1
    ISSN: 1420-9071
    Keywords: HIV RNase H ; inhibitors ; novenamines ; micelles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Few inhibitors of the RNase H function associatesd with the HIV-1 reverse transcriptase have been discovered to date. We observed that three novenamines, U-34445, U-35122, and U-35401, are specific inhibitors of the HIV-1 RT RNase H function. All three compounds are strong amphiphiles and contain one ionizable group. Hence, a priori, in aqueous solutions the inhibitors might exist in at least four different physical states, namely protonated monomers, ionized monomers, protonated micelles and ionized micelles. The three inhibitors all yielded anomalous dose-response curves, indicating that the four molecular species have different inhibitory potentials. In order to identify the inhibitory species, the amphiphilic properties of these compounds were studied. It was established that in alkaline solutions, around pH 8, all compounds are ionized and form micelles at concentrations above their CMC. Both the protonated and the ionized forms of these molecules from stable insoluble monomolecular layers at the air/water interface. The anomalies of the dose-response curves can be resolved by taking into account the fact that, in solution, the relative proportion of these molecules in each physical state depends on the pH and on their analytical concentration. Thus interpreted the results indicate that RNase H is inhibited only by the ionized micellar form of these compounds and not by their monomeric form. Around their pKa (∼pH5) the three componds reproducibly form uniformly sized, self-emulsified colloidal particles that may be used as an efficient drug delivery system.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Molecular genetics and genomics 260 (1998), S. 372-380 
    ISSN: 1617-4623
    Keywords: Key words Maize ; Flavonoids ; Myb ; Tandem repeats ; Tissue-specific silencing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The maize P gene encodes a Myb-homologous transcriptional regulator of flavonoid pigmentation in floral organs, and different P gene alleles condition precise tissue- and organ-specific pigmentation patterns. To determine the molecular basis for allele-specific expression patterns, we have isolated and compared two natural alleles of the P gene which differ in expression, structure and copy number. The P-rr allele is associated with pigmentation of most floral tissues and contains a single copy of the P gene. In contrast, the P-wr allele restricts pigmentation to a subset of floral tissues, and is composed of six gene copies arranged in a tandem head-to-tail array. Each of the six repeats contains a single P gene, including regulatory and coding sequences. Despite the six-fold tandem repetition of P-wr gene copies, P-wr mRNA levels in kernel pericarp are much reduced compared to mRNA levels from the single-copy P-rr gene. Moreover, the P-wr multicopy complex is hypermethylated relative to P-rr. Thus, maize P gene alleles may represent a natural system for studying the effects of methylation and gene copy number on tissue-specific gene expression. We discuss the possibility that somatic pairing of repeated gene copies may be involved in regulating gene expression.
    Type of Medium: Electronic Resource
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