Molecular mechanics of mineralized collagen fibrils in bone

Bone is a natural composite of collagen protein and the mineral hydroxyapatite. The structure of bone is known to be important to its load-bearing characteristics, but relatively little is known about this structure or the mechanism that govern deformation at the molecular scale. Here we perform full-atomistic calculations of the three-dimensional molecular structure of a mineralized collagen protein matrix to try to better understand its mechanical characteristics under tensile loading at various mineral densities. We find that as the mineral density increases, the tensile modulus of the network increases monotonically and well beyond that of pure collagen fibrils. Our results suggest that the mineral crystals within this network bears up to four times the stress of the collagen fibrils, whereas the collagen is predominantly responsible for the material’s deformation response. These findings reveal the mechanism by which bone is able to achieve superior energy dissipation and fracture resistance characteristics beyond its individual constituents.United States. Office of Naval Research (N000141010562)United States. Army Research Office (W991NF-09-1-0541)United States. Army Research Office (W911NF-10-1-0127)National Science Foundation (U.S.) (CMMI-0642545

Impact of Reduced Lignin on Plant Fitness

Lignin content of crop plants has been reduced by traditional plant breeding, natural and induced mutations, and insertion of transgenes. The effects of these genes and associated lower lignin content have been examined in terms of agricultural fitness or with regard to economically harvestable yields of useful plant products, or, in the case of some perennial species, survivability over multiple years. In general, crop yields are depressed by significant reductions in lignin content. Other negative effects observed in plants with lowered lignin contents include lodging and reduction of long-term survival of some perennial species. However, the interactions of genes involved in lignin metabolism with genetic background and the environment in which the low- lignin crop is cultivated are substantial. Examples are provided that demonstrate that lignin can be reduced in specific lines or populations without damaging fitness. It is concluded that it will be essential to incorporate lignin reducing genes into numerous genetic backgrounds and combinations, and evaluate the resulting lines in diverse environments, to discover optimal combinations and to obtain a true measure of value and fitness in agricultural systems

Exploring the 'city-bush divide': what do urban people really think of farmers and rural land management?

Many developed economies have highly urbanised populations. As environmental concern in the general population has increased, farmers have found themselves at the centre of competing demands in relation to the resources and land they manage or own. Australian farmers are concerned that urban people are unsympathetic and see them as ‘environmental vandals’. These perceived negative views of farmers are part of a wider division variously described as an ‘urban - rural’ or ‘city - bush’ divide. However, there is no empirical evidence to support, or define the nature of a divide, if it does exist in relation to urban people’s views of farmers’ environmental performance. This study found little evidence of a city - bush divide in relation to urban views of farmers and rural land management. Although diverse views are held of farmers and rural land management, there is a reasonable level of trust in, and empathy with, farmers. Nevertheless, rural land management is of high concern for urban people and they consider the environment to be in poor condition. We identified five groups of people, with only one group that could be considered sceptical of farmers’ land management performance. The results highlight the difficulties in developing appropriate rural land management policies that balance legitimate societal concerns for environmental condition and public versus private benefits and costs, while not adversely affecting the many farmers whom the majority of urban people feel act responsibly. The data suggest uncertainty in the urban community as to whether government is effectively achieving this balance