2D-HPLC and MALDI-TOF/TOF analysis of barley proteins glycated during brewing

The barley proteins have been the subject of interests of many research groups dealing with barley grains, malt and beer. The proteins which remain intact after harsh malting conditions influence the quality and flavor of beer. The characteristic feature of the proteins present in malt and beer is their extensive modification with carbohydrates, mainly glucose that comes from the starch degradation during technological processes. The degree of the protein glycation has an effect on the quality of malt and beer and on the properties of the beer foam. A combination of two-dimensional high performance liquid chromatography (2D-HPLC) and matrix assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF/TOF MS) was used for the analysis of the protein extracts that were reduced, alkylated, and degraded enzymatically without prior protein separation. This so-called "shot-gun" approach enabled us to determine glycation sites in one third of the proteins identified in the study and to propose potential glycation markers for fast and efficient monitoring during malting.     

Effect of carnitine on greening barley leaves

Carnitine increases chlorophyll production in greening barley leaves. [Methyl-¹⁴C]carnitine fed to greening leaves was not utilized as a carbon sou     

Thioredoxin: an unexpected meeting place

For much of the latter part of the 20th century, photosynthesis research at Berkeley was dominated by Daniel Arnon and Melvin Calvin. In this article, I have briefly described how their contributions jointly provided the foundation for our work on thioredoxin and how important Andrew Benson was to this effort.     

Symptoms of nitrogen saturation in an aggrading forested watershed in western Maryland

The objective of this study was to evaluate the nitrogen (N) biogeochemistry of an 18–22 year old forested watershed in western Maryland. We hypothesized that this watershed should not exhibit symptoms of N saturation. This watershed was a strong source of nitrate (NO₃ ⁻) to the stream in all years, with a mean annual export of 9.5 kg N ha⁻¹ year⁻¹ and a range of 4.4–18.4 kg N ha⁻¹ year⁻¹. During the 2001 and 2002 water years, wet deposition of inorganic N was 9.0 kg N ha⁻¹ year⁻¹ and 6.3 kg N ha⁻¹ year⁻¹, respectively. Watershed N export rates in 2001 and 2002 water years were 4.2 kg N ha⁻¹ year⁻¹ and 5.3 kg N ha⁻¹ year⁻¹, respectively. During the wetter water years of 2003 and 2004, the watershed exported 15.0 kg N ha⁻¹ year⁻¹ and 18.4 kg N ha⁻¹ year⁻¹, rates that exceeded annual wet deposition of N by a factor of two (7.5 kg N ha⁻¹ year⁻¹ in 2003) and three (5.5 kg N ha⁻¹ year⁻¹ in 2004). Consistent with the high rates of N export, were high concentrations (2.1–3.3%) of N in foliage, wood (0.3%) and fine roots, low C:N ratios in the forest floor (17–24) and mineral soil (14), high percentages (83–96%) of the amount of mineralized N that was nitrified and elevated N concentrations (up to 3 mg N l⁻¹) in soil solution. Although this watershed contained a young aggrading forest, it exhibited several symptoms of N saturation commonly observed in more mature forests.     

Effects of density-dependent migrations on stability of a two-patch predator-prey model

We consider a predator-prey model in a two-patch environment and assume that migration between patches is faster than prey growth, predator mortality and predator-prey interactions. Prey (resp. predator) migration rates are considered to be predator (resp. prey) density-dependent. Prey leave a patch at a migration rate proportional to the local predator density. Predators leave a patch at a migration rate inversely proportional to local prey population density. Taking advantage of the two different time scales, we use aggregation methods to obtain a reduced (aggregated) model governing the total prey and predator densities. First, we show that for a large class of density-dependent migration rules for predators and prey there exists a unique and stable equilibrium for migration. Second, a numerical bifurcation analysis is presented. We show that bifurcation diagrams obtained from the complete and aggregated models are consistent with each other for reasonable values of the ratio between the two time scales, fast for migration and slow for local demography. Our results show that, under some particular conditions, the density dependence of migrations can generate a limit cycle. Also a co-dim two Bautin bifurcation point is observed in some range of migration parameters and this implies that bistability of an equilibrium and limit cycle is possible.