Genetic validation and spectroscopic detailing of DHN-melanin extracted from an environmental fungus

Accurate characterization of melanin using analytical methodologies has proved to be difficult due to its heterogeneity, insolubility in wide pH and broad range of solvents. The present study was undertaken to characterize melanin extracted from an environmental Aspergillus fumigatus AFGRD105 by studying its genes, chemical properties and spectral data. A gene based approach to confirm the type of melanin carried out indicated the extracted melanin to be of the dihydroxynaphthalene type. On comparison with synthetic melanin, UV–Vis and IR spectra of the extracted melanin revealed characteristic peaks that can be further used for confirmation of DHN-melanin extracted from any source. Solid state ¹³C NMR spectroscopy established the presence of the hydroxyl-naphthalene moiety and validated the results obtained by genetic analysis. The correct assignment of the observed spectral frequency characteristic of functional groups can be further adapted in future works that deal with binding capacities and biomolecule systems involving melanin.     

Milestoning simulation of ligand dissociation from the glycogen synthase kinase 3β

As drug-binding kinetics has become an important factor to be considered in modern drug discovery, this work evaluated the ability of the Milestoning method in computing the absolute dissociation rate of a ligand from the serine–threonine kinase, glycogen synthase kinase 3β, which is a target for designing drugs to treat diseases such as neurodegenerative disorders and diabetes. We found that the Milestoning method gave good agreement with experiment with modest computational costs. Although the time scale for dissociation lasted tens of seconds, the collective molecular dynamics simulations total less than 1μs. Computing the committor function helped to identify the transition states (TSs), in which the ligand moved substantially away from the binding pocket. The glycine-rich loop with a serine residue attaching to its tips was found to undergo large movement from the bound to the TSs and might play a role in controlling drug-dissociation kinetics.     

Electrical stimulation of the macaque ventral tegmental area drives category-selective learning without attention

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Mammalian cells share a common pathway for the relief of DNA replication arrest by O6-alkyl guanine, incorporated 6-thioguanine and UV photoproducts.

We previously reported the cloning of a mammalian gene that restores UV resistance to a postreplication recovery defective and mex- Indian muntjac mutant cell line, SVM, by improving daughter-strand DNA replication on a UV-damaged template. The improved replication was, however, found to be error-prone, as judged by a hypermutable phenotype (Bouffler et al. (1990) Somatic Cell Mol. Genet., 16, 507-516). We now report that this gene also increases the resistance of SVM to the cytotoxic effects of methyl- and ethyl-nitrosourea, though not to dimethyl sulphate, by a similar postreplication recovery process. The gene does not increase the activity of O6-alkylguanine-DNA-alkyltransferase in the cell. We conclude that at least one mechanism of postreplication recovery in mammalian cells allows UV photoproducts and O6-alkylguanine lesions to be tolerated by the replication complex. The fact that the gene also confers resistance to 6-thioguanine suggests that, once incorporated, this base analogue can disrupt normal DNA replication and that a single mechanism can allow replication to proceed beyond 3 diverse DNA lesions.