Tryptophan-mediated denaturation of beta-lactoglobulin A by UV irradiation

beta-Lactoglobulin A, a genetic variant of one of the main whey proteins, was irradiated at 295 nm for 24 h. After irradiation, 18% of the protein was denatured (determined by reverse-phase chromatography). The fluorescence spectrum of the irradiated protein was red-shifted compared to that of the native protein, indicating a change in protein folding. Sulfhydryl groups, which are buried in native beta-lactoglobulin, were exposed following irradiation and became available for quantification using the Ellman assay. The quantity of exposed sulfhydryls increased, but the number of total sulfhydryl groups decreased. Gel permeation chromatography showed that some protein aggregation occurred during irradiation. Fourier transform infrared (FTIR) spectroscopy of irradiated beta-lactoglobulin revealed changes in the secondary structure, comparable to that of early events during heat-induced denaturation. There was evidence for some photo-oxidation of tryptophan.     

Estimation of preliminary reference values for macro and micronutrients in ‘Valencia’ orange in Venezuela,by means of the compositional nutrient diagnosis system

The present study was aimed at developing preliminary reference values for foliar tissue for nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn) for `Valencia´ orange in Venezuela, using the Compositional Nutrient Diagnosis system (CND). References values were derived from a database comprising the nutrients concentrations and the yields of `Valencia´ orange trees (Citrus sinensis L. Osbeck) grafted on two different rootstocks, viz., Volkamer lemon (Citrus volkameriana Pasq.), and Cleopatra tangerine (Citrus reshni, Hort. ex. Tan). Cutoff values separating high- and low-yield sub-samples were estimated through modeling the cumulative variance ratio function versus yield relationships with the Boltzmann equation. For macronutrients, the norms developed were dependent upon the inclusion of the micronutrients concentrations in the calculations, and on the rootstocks. Care must thus be exercised, since nutrient indexes, and thus nutritional diagnosis, are based upon proper selection of such values.     

Nutrient availability in the initial stages of surface mine spoil reclamation — Impact on plant growth

The aim of this study was to characterise nutrient availability in the initial stages of reclamation and its impact on the growth of Secale multicaule L., the typical cover crop in newly established Pinus silvestris L. stands. A field experiment testing different levels of nutrient supply (N, P, K) was conducted on a carboniferous and a non-carboniferous sandy mine spoil representing typical mine spoils in the open-cast lignite mining district of Lower Lusatia. On both types of mine spoils, primarily N and P limited plant growth. On non-carboniferous mine spoil, low P availability to plants was alleviated by mineral fertiliser application while on carboniferous mine spoil, due to P immobilisation, P availability was still limiting plant growth after similar levels of P fertilisation. The elevated N_min content in carboniferous mine spoil compared to non-carboniferous mine spoil is probably the result of less N leaching as the dominant N form in carboniferous mine spoil is NH₄⁺ while the highly mobile NO₃^— is prevailing in the non-carboniferous mine spoil. N release from geogenic organic matter in carboniferous mine spoil as suggested by comparable N_t contents in pedogenetically formed soil organic matter is less likely.     

Modeling of multiple stocks and programs for master planning and feasibility studies

Public hatchery facilities increasingly respond to recreational fishing demands for larger catchable salmonids and to production programs that require a variety of species. The result of this tendency is to require more complexity in hatchery design and operations involving the simultaneous rearing of several species that results in overlapping production schedules for crops of fish that carryover from 1 year to the next. This paper presents a highly accessible spreadsheet based computer simulation model for use by culturists, designers, and program planners in designing hatchery facilities with these expanded program demands. It addresses trade offs between budget constraints, stocking objectives, available water resources, and production technologies. The model is structured so that all the assumptions for any facility program simulation can be entered on a single spreadsheet. The essential fish growth, density, flow, and feeding relationships used within the model are those based on widely used paradigms developed by Piper et al. (1982) and others. The program information assumptions include all of the essential information to simulate production runs for each group of fish within the facility, each with specific characteristics such as growth rate, feed conversion, calendar day stocking and harvest dates, and duration of the crop. Those program assumptions are linked to a series of other spreadsheets within the spreadsheet workbook that calculate weekly model simulation results for rearing space, first-pass and rearing flows, feed consumption, and phosphorus discharge for each group of fish and then for the combined results of the entire facility. The facility simulation results are automatically plotted in a graphic format for comparative evaluation of any series of production program assumptions that the operators consider in the design process. The graphic results for simulated rearing space, flow, and feeding are presented in an annual format in weekly increments. The graphic results readily present the utilization of facility space and water resources and clearly indicate opportunities to improve facility efficiency in a new simulation providing a rapid means of iterating design changes until the exercise generates the most favorable facility. Several case studies provide examples of this process for the user.     

What controls fish functional diversity patterns in Colombian Andean streams?

Understanding the mechanisms that structure communities have been a major challenge in ecological theory. Functional trait-based approaches are increasingly used for studying the processes underlying community assembly. However, species-poor systems of Andean streams these processes are largely unknown. Tropical Andean streams are highly variable in space-time and characterised by the harsh or stable environment, resulting in a high taxonomic and ecological diversity. In this study, we tested the influence of environmental variables on the fish functional structure. We proposed that in ecosystems with harsh environments, environmental filtering will structure fish assemblages, and in ecosystems with a more stable environment, limiting similarity will prevail, increasing functional diversity. We analysed fish assemblages using functional diversity indices, fourth-corner RLQ analyses and multiple regression models. Environmental variables such as altitude, stream width, sub-Andean vegetation and pH influenced functional diversity. For instance, high values of functional redundancy were registered at high elevation streams, reflecting fish assemblages composed of highly dominant species with similar functional traits such as species of the genus Astroblepus. However, we found differences between Astroblepus species in the number and distance of gill rakers which might indicate resource partitioning and coexistence. On the other hand, our results show both stochastic dynamics and environmental filtering are structuring fish assemblages in low and high elevation Andean streams respectively.