Evolution of a Distinct Genomic Domain in Drosophila: Comparative Analysis of the Dot Chromosome in Drosophila melanogaster and Drosophila virilis

The distal arm of the fourth (“dot”) chromosome of Drosophila melanogaster is unusual in that it exhibits an amalgamation of heterochromatic properties (e.g., dense packaging, late replication) and euchromatic properties (e.g., gene density similar to euchromatic domains, replication during polytenization). To examine the evolution of this unusual domain, we undertook a comparative study by generating high-quality sequence data and manually curating gene models for the dot chromosome of D. virilis (Tucson strain 15010–1051.88). Our analysis shows that the dot chromosomes of D. melanogaster and D. virilis have higher repeat density, larger gene size, lower codon bias, and a higher rate of gene rearrangement compared to a reference euchromatic domain. Analysis of eight “wanderer” genes (present in a euchromatic chromosome arm in one species and on the dot chromosome in the other) shows that their characteristics are similar to other genes in the same domain, which suggests that these characteristics are features of the domain and are not required for these genes to function. Comparison of this strain of D. virilis with the strain sequenced by the Drosophila 12 Genomes Consortium (Tucson strain 15010–1051.87) indicates that most genes on the dot are under weak purifying selection. Collectively, despite the heterochromatin-like properties of this domain, genes on the dot evolve to maintain function while being responsive to changes in their local environment

A spectroscopic study of some Schiff's bases and their transition metal complexes.

The synthesis of some conjugated 1:3 di-imine Schiff's base ligand hydrochlorides, together with an investigation into their behaviour as ligands in acidic and basic media, is described. The conformation of some of the ligands has been investigated by means of comparisons between calculated electronic spectra, based upon an assumed geometry, and the observed spectra. The microsymmetry of the metal environments in the first-row transition metal complexes cannot be unambiguously deduced from the electronic spectra and room temperature, solid state, magnetic moments. Of principal interest are the isotropic proton resonance shifts of the bis (iminato) cobalt (II) and nickel (II) complexes. These are interpreted in terms of a dominant contact shift interaction stemming from partial delocalisation of an electron of B-spin from the highest filled bonding pi molecular ethital into metal 3d-atomic orbitals of appropriate symmetry. Evidence for concurrent delocalisation involving the ligand 6-bond system, rotation of the phenyl groups, unusual proton spin-spin relaxation effects, attenuation of spin density into the second ring of a biphenyl unit, and the presence of the pseudocontact interaction in the cobalt (II) complexes, is also presented. The literature appertaining to isotropic proton resonance shifts of complexes of divalent nickel and cobalt is reviewed

A spectroscopic study of some Schiff's bases and their transition metal complexes.

The synthesis of some conjugated 1:3 di-imine Schiff's base ligand hydrochlorides, together with an investigation into their behaviour as ligands in acidic and basic media, is described. The conformation of some of the ligands has been investigated by means of comparisons between calculated electronic spectra, based upon an assumed geometry, and the observed spectra. The microsymmetry of the metal environments in the first-row transition metal complexes cannot be unambiguously deduced from the electronic spectra and room temperature, solid state, magnetic moments. Of principal interest are the isotropic proton resonance shifts of the bis (iminato) cobalt (II) and nickel (II) complexes. These are interpreted in terms of a dominant contact shift interaction stemming from partial delocalisation of an electron of B-spin from the highest filled bonding pi molecular ethital into metal 3d-atomic orbitals of appropriate symmetry. Evidence for concurrent delocalisation involving the ligand 6-bond system, rotation of the phenyl groups, unusual proton spin-spin relaxation effects, attenuation of spin density into the second ring of a biphenyl unit, and the presence of the pseudocontact interaction in the cobalt (II) complexes, is also presented. The literature appertaining to isotropic proton resonance shifts of complexes of divalent nickel and cobalt is reviewed

The use of N-methylprotoporphyrin dimethyl ester to inhibit ferrochelatase in Rhodopseudomonas sphaeroides and its effect in promoting biosynthesis of magnesium tetrapyrroles.

N-Methylprotoporphyrin dimethyl ester inhibits ferrochelatase in isolated membranes of Rhodopseudomonas sphaeroides at low concentrations (around 10 nm). Full inhibition developed after a short lag phase. The inhibition was non-competitive with porphyrin substrate. Addition of inhibitor to growing cultures of Rps. sphaeroides caused a decrease (near 40%) in cytochrome content and a severe inhibition of ferrochelatase; the excretion of haem into the medium by cell suspensions was also severely inhibited. The addition of N-methylprotoporphyrin dimethyl ester to suspensions of photosynthetically competent Rps. sphaeroides Ga caused excretion of Mg-protoporphyrin monomethyl ester. When added to mutants V3 and O1, magnesium divinylphaeoporphyrin a5 monomethyl ester and 2-devinyl-2-hydroxyethylphaeophorbide a were excreted, with maximum effect at around 3 microM-inhibitor in the medium. The results are interpreted to suggest that the inhibitor decreases concentration of intracellular haem, which normally controls the activity of 5-aminolaevulinate synthetase. Unregulated activity of this enzyme leads to overproduction of protoporphyrin, which is diverted to the bacteriochlorophyll pathway. Further control operates at magnesium protoporphyrin ester conversion in normal cells