Adenosine thiamine triphosphate and adenosine thiamine triphosphate hydrolase activity in animal tissues

Adenosine thiamine triphosphate (AThTP), a vitamin B1 containing nucleotide with unknown biochemi­cal role, was found previously to be present in various biological objects including bacteria, yeast, some human, rat and mouse tissues, as well as plant roots. In this study we quantify AThTP in mouse, rat, bovine and chicks. We also show that in animal tissues the hydrolysis of AThTP is catalyzed by a membrane-bound enzyme seemingly of microsomal origin as established for rat liver, which exhibits an alkaline pH optimum of 8.0-8.5 and requires no Mg2+ ions for activity. In liver homogenates, AThTP hydrolase obeys Michaelis-Menten kinetics with apparent Km values of 84.4 ± 9.4 and 54.6 ± 13.1 µМ as estimated from the Hanes plots for rat and chicken enzymes, respectively. The hydrolysis of AThTP has been found to occur in all samples examined from rat, chicken and bovine tissues, with liver and kidney being­ the most abundant in enzyme activity. In rat liver, the activity of AThTP hydrolase depends on the age of animals

Band gaps in jagged and straight graphene nanoribbons tunable by an external electric field

International audienceBand gap control by an external field is useful in various optical, infrared and THz applications. However, widely tunable band gaps are still not practical due to a variety of reasons. Using the orthogonal tight-binding method for π-electrons, we have investigated the effect of the external electric field on a subclass of monolayer chevron-type graphene nanoribbons that can be referred to as jagged graphene nanoribbons. A classification of these ribbons was proposed and band gaps for applied fields up to the SiO2 breakdown strength (1Vnm^(−1)) were calculated. According to the tight-binding model, band gap opening (or closing) takes place for some types of jagged graphene nanoribbons in the external electric field that lies on the plane of the structure and perpendicular to its longitudinal axis. Tunability of the band gap up to 0.6eV is attainable for narrow ribbons. In the case of jagged ribbons with armchair edges larger jags forming a chevron pattern of the ribbon enhance the controllability of the band gap. For jagged ribbons with zigzag and armchair edges regions of linear and quadratic dependence of the band gap on the external electric field can be found that are useful in devices with controllable modulation of the band gap