Carotenoid functions--a subject for the biophysical research

Progress, problems and outlooks in studies of functions of carotenoids in cells of living beings.     

可持续发展研究的学科动向

近40年来,可持续发展的概念、理论和方法不断拓展,已成为当今国际社会普遍关心的热点问题。利用中国知网(http://epub.cnki.net)的网络平台,分别以"生态学"、"经济学"、"社会学"以及"可持续发展"为关键词,对6个数据库跨库检索1993年至2011年的所有文献。分别从以上3个学科的角度,对这些文献的研究内容、研究方法进行了统计,分析国内可持续发展研究的趋势。结果表明,可持续发展的研究在3个学科方向上都表现出多学科交叉性、领域综合性、方法定量化的总体趋势;其中生态学在研究方法上较为突出。     

What the hen can tell about her eggs: egg development on the basis of energy budgets

By a simple model involving the state variables size and storage, it is possible to describe a wide variety of observations on the feeding, growth, energy storage and reproduction of animals. The model is based on the assumption that reproduction, growth as well as maintenance depend on the stored energy only and not directly on feeding. If an egg is thought of as a non-feeding animal, the model predicts the respiration ontogeny and growth of the embryo inside the egg. These predictions seem to hold well for published data on the development of eggs of fish and ratite, precocial and altricial birds. The latter two are known to follow different respiration ontogenies, but both are described well, differing only in one (compound) parameter value. The model explains why the incubation times of eggs of different species tend to increase linearly with egg size to the power 1/4, and why kiwis and petrels, which lay relatively large eggs, have to brood them much longer than larger birds with eggs of the same size. Conversely, it explains why the small eggs of the (parasitic) European cuckoo, hatch earlier than the still smaller eggs of their tiny hosts.Furthermore, it has been shown how the maintenance rate constant, which frequently appears in the microbial literature, can be obtained from measurements on the respiration and weight ontogeny in embryos, so linking independent lines of research. Application of the model shows an increase of the maintenance rate constant from bacteria, crustaceans, up to fish and birds, and a decrease from bacteria to green algae, suggesting lines of evolutionary development.     

Parity violation and the evolution of biomolecular homochirality

Parity violation at the level of terrestrial biopolymers, as seen in proteins, DNAs, and RNAs, and parity violation at the level of nuclear processes, as evident in longitudinally polarized beta-particles and parity-violating energy differences (PVEDs), are discussed and their fundamental importances are emphasized. Attempts to find a causal connection between the unique homochirality of biopolymers and parity violation at the nuclear level, and speculations that the former is a consequence of the latter, are reviewed. Consideration of all lines of evidence leads to the conclusion that there is no substantiation for such a causal connection, and that the two levels of parity violation are entirely independent of each other.     

Parity violation and the origins of biomolecular handedness

The violation of parity by the weak interactions ensures that enantiomeric chiral molecules have inequivalent energies, one being inherently stabilized with respect to the other. These parity-violating energy differences have been calculated for a number of fundamental biomolecules including a series of alpha-amino acids, polypeptide structures, and a representative of the sugar series together with its variation over a possible prebiotic reaction path leading to alpha-amino acids. In each case the natural enantiomer found in terrestrial biochemistry was shown to be intrinsically stabilized and preferred over its unnatural enantiomer. The significance of these results in accounting for the prebiotic origins of the terrestrial biomolecular homochirality is discussed and the possible consequences of parity-violating energy differences in mineral catalysts during the prebiotic era considered.