Facile Redox-Induced Aromatic-Antiaromatic Interconversion of a ß-Tetracyano-21,23-Dithiaporphyrin under Ambient Conditions.

Facile redox-induced aromatic-antiaromatic interconversions were accomplished by using ß-tetracyano-21,23-dithiaporphyrin (CN4 S2 Por). Introduced cyano groups not only increased the reduction potential of the porphyrin core but also stabilized the antiaromatic isophlorin (CN4 S2 Iph) by π conjugation. The reduction of CN4 S2 Por with hydrazine in polar solvents quantitatively affords CN4 S2 Iph, even under ambient conditions. CN4 S2 Iph retains a nearly planar conformation and exhibits considerable antiaromaticity. Aerobic oxidation of CN4 S2 Iph to CN4 S2 Por occurs in nonpolar solvents. This study was conducted to contribute to the understanding of the structure-antiaromaticity relationship.

Sweetness characterization of recombinant human lysozyme.

Lysozyme, a bacteriolytic enzyme, is widely distributed in nature and is a component of the innate immune system. It is established that chicken egg lysozyme elicits sweetness. However, the sweetness of human milk lysozyme, which is vital for combating microbial infections of the gastrointestinal tract of breast-fed infants, has not been characterized. This study aimed to assess the elicitation of sweetness using recombinant mammalian lysozymes expressed in Pichia pastoris. Recombinant human lysozyme (h-LZ) and other mammalian lysozymes of mouse, dog, cat and bovine milk elicited similar sweetness as determined using a sensory test, whereas bovine stomach lysozyme (bs-LZ) did not. Assays of cell cultures showed that h-LZ activated the human sweet taste receptor hT1R2/hT1R3, whereas bs-LZ did not. Point mutations confirmed that the sweetness of h-LZ was independent of enzyme activity and substrate-binding sites, although acidic amino acid residues of bs-LZ played a significant role in diminishing sweetness. Therefore, we conclude that elicitation of sweetness is a ubiquitous function among all lysozymes including mammalian lysozymes. These findings may provide novel insights into the biological implications of T1R2/T1R3-activation by mammalian lysozyme in the oral cavity and gastrointestinal tract. However, the function of lysozyme within species lacking the functional sweet taste receptor gene, such as cat, is currently unknown.

Surfacers change their dive tactics depending on the aim of the dive: evidence from simultaneous measurements of breaths and energy expenditure.

Air-breathing divers are assumed to have evolved to apportion their time between surface and underwater periods to maximize the benefit gained from diving activities. However, whether they change their time allocation depending on the aim of the dive is still unknown. This may be particularly crucial for 'surfacers' because they dive for various purposes in addition to foraging. In this study, we counted breath events at the surface and estimated oxygen consumption during resting, foraging and other dives in 11 green turtles (Chelonia mydas) in the wild. Breath events were counted by a head-mounted acceleration logger or direct observation based on an animal-borne video logger, and oxygen consumption was estimated by measuring overall dynamic body acceleration. Our results indicate that green turtles maximized their submerged time, following this with five to seven breaths to replenish oxygen for resting dives. However, they changed their dive tactic during foraging and other dives; they surfaced without depleting their estimated stores of oxygen, followed by only a few breaths for effective foraging and locomotion. These dichotomous surfacing tactics would be the result of behavioural modifications by turtles depending on the aim of each dive.

Ethogram of Immature Green Turtles: Behavioral Strategies for Somatic Growth in Large Marine Herbivores.

Animals are assumed to obtain/conserve energy effectively to maximise their fitness, which manifests itself in a variety of behavioral strategies. For marine animals, however, these behavioral strategies are generally unknown due to the lack of high-resolution monitoring techniques in marine habitats. As large marine herbivores, immature green turtles do not need to allocate energy to reproduction but are at risk of shark predation, although it is a rare occurrence. They are therefore assumed to select/use feeding and resting sites that maximise their fitness in terms of somatic growth, while avoiding predation. We investigated fine-scale behavioral patterns (feeding, resting and other behaviors), microhabitat use and time spent on each behavior for eight immature green turtles using data loggers including: depth, global positioning system, head acceleration, speed and video sensors. Immature green turtles at Iriomote Island, Japan, spent an average of 4.8 h feeding on seagrass each day, with two peaks, between 5∶00 and 9∶00, and between 17∶00 and 20∶00. This feeding pattern appeared to be restricted by gut capacity, and thus maximised energy acquisition. Meanwhile, most of the remaining time was spent resting at locations close to feeding grounds, which allowed turtles to conserve energy spent travelling and reduced the duration of periods exposed to predation. These behavioral patterns and time allocations allow immature green turtles to effectively obtain/conserve energy for growth, thus maximising their fitness.