Caffeine Prevents Transcription Inhibition and P-TEFb/7SK Dissociation Following UV-Induced DNA Damage

Background: The mechanisms by which DNA damage triggers suppression of transcription of a large number of genes are poorly understood. DNA damage rapidly induces a release of the positive transcription elongation factor b (P-TEFb) from the large inactive multisubunit 7SK snRNP complex. P-TEFb is required for transcription of most class II genes through stimulation of RNA polymerase II elongation and cotranscriptional pre-mRNA processing. Methodology/Principal Findings: We show here that caffeine prevents UV-induced dissociation of P-TEFb as well as transcription inhibition. The caffeine-effect does not involve PI3-kinase-related protein kinases, because inhibition of phosphatidylinositol 3-kinase family members (ATM, ATR and DNA-PK) neither prevents P-TEFb dissociation nor transcription inhibition. Finally, caffeine prevention of transcription inhibition is independent from DNA damage. Conclusion/Significance: Pharmacological prevention of P-TEFb/7SK snRNP dissociation and transcription inhibitio

Electronic properties of quantum dot systems realized in semiconductor nanowires

Catalyst-assisted growth of semiconductor nanowires has opened up several new and exciting possibilities for low-dimensional semiconductor structures. The authors review progress on the realization of quantum dots in semiconductor nanowires, and their characterization by transport spectroscopy. Emphasis is placed on the wide range electronic properties exhibited due to flexibility of the growth process in terms of nanostructure composition and size. Particular attention is placed on studies of spin in few-electron quantum dots

Electrical properties and band diagram of InSb-InAs nanowire type-III heterojunctions

The electrical properties of nanowire-based n-InSb-n-InAs heterojunctions were investigated theoretically and experimentally. Analysis of the current-voltage characteristics showed that the current through the heterojunction is caused mostly by generation-recombination processes in the InSb and at the heterointerface. Due to the partially overlapping valence band of InSb and the conduction band of InAs, the second process is fast and activationless. Theoretical analysis showed that, depending on the heterojunction parameters, the flux of non-equilibrium minority carriers may have a different direction, explaining the experimentally observed non-monotonic coordinate dependence of the electron beam induced current. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4795123

Probing the Gate-Voltage-Dependent Surface Potential of Individual InAs Nanowires Using Random Telegraph Signals RID C-6303-2008

We report a novel methocl for probing the gate-voltage dependence of the surface potential of individual semiconductor nanowires. The statistics of electronic occupation of a single defect on the surface of the nanowire, determined from a random telegraph signal, is used as a. measure for the local potential. The method, is demonstrated for the case of one or two switching defects in indium arsenide (InAs) nanowire field effect transistors at temperatures T = 25-77 K. Comparison with a self consistent model shows that surface potential variation is retarded In the conducting regime due to screening by surface states with density D(ss) approximate to 10(12) cm(-2) ev(-1). Temperature-dependent dynamics of, electron capture and emission producing the random telegraph signals are also analyzed, and multiphonon emission is identified as the process responsible for capture and emission of electrons from the surface traps. Two defects studied in detail had capture activation energies of E(B) approximate to 50 meV and E(B) approximate to 110 meV and cross sections of sigma(infinity) approximate to 3 x 10(-19) cm(2) and sigma(infinity) approximate to 2 x 10(-17) cm(2), respectively. A lattice relaxation energy of s (h) over bar omega = 187 +/- 15 meV was found for the first defect

Virtual fragment screening for novel inhibitors of 6-phosphogluconate dehydrogenase

We report the identification of novel inhibitors of Trypanosoma brucei 6PGDH enzyme by virtual fragment screening