The periplasmic FbpA (ferric-binding protein A) from Haemophilus influenzae plays a critical role in acquiring iron from host transferrin, shuttling iron from the outer-membrane receptor complex to the inner-membrane transport complex responsible for transporting iron into the cytoplasm. In the present study, we report on the properties of a series of site-directed mutants of two adjacent tyrosine residues involved in iron co-ordination, and demonstrate that, in contrast with mutation of equivalent residues in the N-lobe of human transferrin, the mutant FbpAs retain significant iron-binding affinity regardless of the nature of the replacement amino acid. The Y195A and Y196A FbpAs are not only capable of binding iron, but are proficient in mediating periplasm-to-cytoplasm iron transport in a reconstituted FbpABC pathway in a specialized Escherichia coli reporter strain. This indicates that their inability to mediate iron acquisition from transferrin is due to their inability to compete for iron with receptor-bound transferrin. Wild-type iron-loaded FbpA could be crystalized in a closed or open state depending upon the crystallization conditions. The synergistic phosphate anion was not present in the iron-loaded open form, suggesting that initial anchoring of iron was mediated by the adjacent tyrosine residues and that alternate pathways for iron and anion binding and release may be considered. Collectively, these results demonstrate that the presence of a twin-tyrosine motif common to many periplasmic iron-binding proteins is critical for initially capturing the ferric ion released by the outer-membrane receptor complex.

Aviation is one of the fastest mode of transportation in the world, and demand for air transportation is growing continuously. The past oil crises, volatile fuel prices, depleting fuel stocks, and increasing environmental concerns have drawn the significant attention of aviation industry towards the need for judicious use of aviation fuel. Thus, economic and environmental sustainability concerns have led to dramatic progress in aviation fuel efficiency improvements in the past decades. However, significant efforts to improve the fuel efficiency through more advanced designs, techniques, and strategies will remain a priority. This article provides an overview of the challenging issues, accomplishments, and opportunities in relation to the aviation industry, focusing on aviation fuel consumption. This article offers insights for the aviation industry, that is, aircraft manufacturers and airlines to move toward more fuel-efficient options in future.

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With the projected air traffic growth, aviation fuel needs will grow by 3% globally per year. Considering this, aviation industry has set ambitious goals to enhance its fuel efficiency. This study presents an integrated framework for aviation fuel consumption reduction, which will also limit its CO 2 emissions. Further, this research aims to categorize influential factors and examine their relative importance for fuel-efficient aviation. This study's theoretical framework combines and reconciles eight major areas: alternative jet fuels, aviation infrastructure, aircraft operations, socio-ecopolitical environment, aircraft design, technology, environmental uncertainty, and strategic changes. In all, 37 sub-factors were identified. The priority ratings of these sub-factors with respect to 'aviation fuel consumption reduction' objective is measured by hybrid analytical hierarchy process-entropy method, using pair-wise comparison matrices. The findings attributed the highest importance to 'technological innovations', followed by 'aircraft design' and 'aircraft operations' for saving aviation fuel. Based on the obtained ranking 'engine design', 'laminar flow technology', and 'air traffic management technology' emerged as the three most important sub-factors. The robustness of priority rankings has been tested using sensitivity analysis. This study shows the path for continuous improvement in aviation fuel efficiency by directing efforts and investments on highly important factors.

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