Solvent composition regulates the Se : Sb ratio in antimony selenide nanowires deposited from thiol-amine solvent mixtures.

Antimony selenide (Sb2Se3), a V2VI3 semiconductor with an intriguing crystal structure, has demonstrated improved power conversion and solar-to-hydrogen efficiencies in recent years. Depositing antimony selenide nanowires (NWs) from a solution such as a thiol : amine "alkahest" ink is a low-cost and facile route to deposit high surface area photocathodes. However, little is known about the correlations between the solvent composition and the crystallites' structure and optoelectronic properties, which are crucial for photovoltaic and photoelectrochemical applications. We found that the Se : Sb ratio in the NWs decreases from 3 : 2 to less than 1 : 1 with decreasing thiol : amine ratio in the ink used for deposition but not in the solvent mixture used for dissolving the metals. The reduced Se : Sb ratio in the solid NWS correlates with an optical bandgap wider by ∼0.3 eV in comparison to stoichiometric NWs, a decrease of the NWs diameter from 180 to 30 nanometers, and a ∼0.2 eV larger work function. In addition, we found that the Se : Sb ratio is not uniform along the NWs, which causes a surface potential increase near the tips of the NWs due to a lower Se : Sb ratio near the NWs tips. The increased surface potential near the tips corresponds to a driving force, due to doping or graded bandgap broadening, that facilitates the migration of photoexcited electrons towards the NW tips. Our findings unlock a path for fine-tuning the optoelectronic properties of antimony selenide towards improving the performance of antimony selenide solar cells and photocathodes.

Surface-exposed conserved region of the streptococcal M protein induces antibodies cross-reactive with denatured forms of myosin.

Vaccines based on a highly conserved cell surface exposed C-repeat region of the group A streptococcal M protein molecule have been found to induce protection against mucosal challenge by homologous and heterologous streptococcal serotypes. Rabbit hyperimmune antisera were produced to four partially overlapping peptides of the C-repeat region of M6 protein. These were examined by both direct and competitive ELISA and by Western blotting for their reactivity against mammalian coiled coil proteins such as laminin, myosin, light meromyosin, heavy meromyosin, and cardiac tropomyosin, and to the denatured forms of some of these molecules. All sera reacted strongly with the recombinant M6 protein molecule. In addition, antibodies to three of the peptides displayed generally low levels of cross-reactivity with at least one of the mammalian proteins, whereas antibodies to one peptide did not cross-react with any of the proteins tested. The observed reactivity was found to be directed predominantly against denatured forms of the mammalian molecules. For instance, the cleaved forms of myosin bound better to the cross-reactive antibodies than the intact molecule. Furthermore, heat-denatured heavy meromyosin competed severalfold better in competitive ELISA than the non-heat-denatured "native" form. Our results demonstrate that M protein peptides corresponding to epitopes shared among rheumatic fever-associated strains of streptococci can lead to the production of low levels of antibodies reactive with mammalian coiled coil molecules. These antibodies are directed against the denatured forms of these molecules.

Molecular cloning of the mouse CCK gene: expression in different brain regions and during cortical development.

In this paper we describe experiments that address specific issues concerning the regulation of the mouse cholecystokinin gene in brain and intestine. The mouse cholecystokinin gene was cloned and sequenced. Extensive homology among the mouse, man and rat genes was noted particularly in the three exons and the regions upstream of the RNA start site. RNAse protection assays for each of the three exons were used to demonstrate that CCK is expressed in only a subset of tissues and that the same cap site and splice choices are used in brain, intestine as well as in cerebellum, cortex, midbrain, hypothalamus and hippocampus. CCK RNA was also noted to be detectable in kidney. Thus the same gene using the same promoter is expressed in subsets of cells that differ in their biochemical, morphologic and functional characteristics. The level of expression of CCK was also monitored during mouse cortical development and the appearance of CCK RNA was compared to glutamate decarboxylase (GAD), enkephalin and somatostatin. It was noted that each of these cortical markers was first expressed at different times during cortical development. The appearance of CCK RNA during intestinal development was also measured and found to precede appearance in cortex by several days.