Significance of eggshell morphology as an additional tool to distinguish species of sand flies (Diptera: Psychodidae: Phlebotominae).

Morphological characteristics of eggshells are important in sand fly ootaxonomy. In this study, eggshells from Phlebotomus stantoni Newstead, Sergentomyia khawi (Raynal), and Grassomyia indica (Theodor) sand flies collected in Chiang Mai province, Thailand were examined and characterized using light microscopy (LM) and scanning electron microscopy (SEM). Then, eggshell morphology of these three species was described for the first time. Each gravid female was forced to lay eggs by decapitation and the eggs were collected for SEM analysis. Egg laying females were identified by morphological examination and molecular typing using cytochrome b (Cytb) as a molecular marker. The chorionic sculpturing of Ph. stantoni eggs combines two patterns on the same egg: unconnected parallel ridges and reticular patterns. Sergentomyia khawi and Gr. indica have similar chorionic polygonal patterns, but their exochorionic morphology and aeropylar area are different. Results indicate that eggshell morphological characteristics such as chorionic pattern, exochorionic morphology, inter-ridge/boundary area, aeropylar area (including the number of aeropyles) and basal layer, can be useful to develop morphological identification keys of eggs. These can serve as an additional tool to distinguish species of sand flies. In addition, the chorionic sculpturing of the eggs of the three species of sand flies observed by LM is useful for species identification in gravid females with spermathecae obscured by eggs.

Structure of a bd oxidase indicates similar mechanisms for membrane-integrated oxygen reductases.

The cytochrome bd oxidases are terminal oxidases that are present in bacteria and archaea. They reduce molecular oxygen (dioxygen) to water, avoiding the production of reactive oxygen species. In addition to their contribution to the proton motive force, they mediate viability under oxygen-related stress conditions and confer tolerance to nitric oxide, thus contributing to the virulence of pathogenic bacteria. Here we present the atomic structure of the bd oxidase from Geobacillus thermodenitrificans, revealing a pseudosymmetrical subunit fold. The arrangement and order of the heme cofactors support the conclusions from spectroscopic measurements that the cleavage of the dioxygen bond may be mechanistically similar to that in the heme-copper-containing oxidases, even though the structures are completely different.

Orientation-dependent electron transport in a single redox protein.

The redox-active protein cytochrome b(562) has been engineered to introduce pairs of thiol groups in the form of cysteine residues at specified sites. Successful STM imaging of the molecules adsorbed on a gold surface indicated that one thiol group controls the orientation of the molecule and that the protein maintains its native form under the experimental conditions. Stable protein-gold STM tip electrical contact was directly observed to form via the second free thiol group in current-voltage and current-distance measurements. Proteins with thiol contacts positioned across the protein's short axis displayed a conductance of (3.48 ± 0.05) × 10(-5)G(0). However proteins with thiol groups placed along the long axis reproducibly yielded two distinct values of (1.95 ± 0.03) × 10(-5)G(0) and (3.57 ± 0.11) × 10(-5)G(0), suggesting that the placement of the asymmetrically located haem within the protein influences electron transfer. In contrast, the unengineered wild-type cytochrome b(562) had conductance values at least 1 order of magnitude less. Here we show that an electron transfer protein engineered to bind gold surfaces can be controllably oriented and electrically contacted to metallic electrodes, a prerequisite for potential integration into electronic circuits.

Self-assembly of one- and two-dimensional hemoprotein systems by polymerization through heme-heme pocket interactions.

Supramolecular protein polymers: When a heme moiety was introduced to the surface of an apo-cytochrome b(562)(H63C) mutant, supramolecular polymers formed through noncovalent heme-heme pocket interactions. The incorporation of a heme triad as a pivot molecule in the protein polymer further led to a two-dimensional protein network structure, which was visualized by tapping-mode atomic force microscopy (see picture).