Photodetectors fabricated from a self-assembly of a deoxyguanosine derivative

A metal–semiconductor–metal (MSM) photodetector has been fabricated using as the semiconductor, a self-assembled layer of a DNA basis, namely a deoxyguanosine derivative, deposited between two gold electrodes. These were defined lithographically on a SiO2 substrate, separated by a distance of about 120 nm. The resulting self-assembled guanosine crystal has been deposited in such a way to achieve striking semiconducting properties. We show that with these conditions, the I–V characteristics are independent of the crystal orientation. The device shows a high current response (differential resistance at room temperature ranges in MΩ) which is symmetric with respect to bias sign and dependent on the illumination conditions. This behavior can be explained by taking into account the standard MSM theory and its applications as a photodetector

Hierarchical Formation of Fibrillar and Lamellar Self-Assemblies from Guanosine-Based Motifs

Here we investigate the supramolecular polymerizations of two lipophilic guanosine derivatives in chloroform by light scattering technique and TEM experiments. The obtained data reveal the presence of several levels of organization due to the hierarchical self-assembly of the guanosine units in ribbons that in turn aggregate in fibrillar or lamellar soft structures. The elucidation of these structures furnishes an explanation to the physical behaviour of guanosine units which display organogelator properties

Transistors based on the Guanosine molecule (a DNA base)

Abstract Molecules are attractive to develop nano-electronic devices. In this paper a new type of transistor is realized by using self-organized films of the Guanosine molecule, a modified DNA base. With its 40 nm channel length the transistor is a good starting point for a new class of nano-electronics devices. Experimental current-voltage characteristics are shown. A circuital model is also proposed

{C-1′ Radical-Based Approaches for the Synthesis of Anomeric Spironucleosides}

Efficient methodologies based on radical cascade reactions for the preparation of anomeric spironucleosides of general structure 3 and 4 are reported. The reactions were performed on modified uridine and 2’-deoxyuridine substrates. The protected derivatives 6 and 28 afforded the anomeric spironucleosides 7 and 29, respectively, in a stereospecific manner and in moderate yields (3-50%). In the 2’-deoxyribo series, the efficiency increased considerably (yields higher than 70%) with a concomitant decrease in stereoselectivity. In fact, the protected derivatives 13 and 21 gave mixtures of the anomeric products 11/14 and 22/23, respectively. Chemical transformations of some of these spironucleosides were successfully performed. The circular dichroism spectra of the anomeric spironucleosides displayed some striking features which can be attributed to the restricted rotation of the glycosidic bond. The reaction mechanism, which has been studied in some detail, comprises of a cascade of radical reactions in which the key step is the 1,5-radical translocation from an alkoxyl or vinyl radical. conveniently situated on the base moiety in the vicinity of the anomeric position. After the translocation, the alkoxyl radical 15, generated photolytically from an in situ prepared hypoiodite. afforded spironucleosides which possess an unusual orthoamide structure at the anomeric position. Alternatively, the vinyl radical 30, generated by the reaction of vinyl bromides with tributyltin radical, undergoes a 5-endo-trig cyclization followed by a bromine atom elimination alter the 1.5-radical translocation step