Latitudinal variation in population structure of wintering Pacific Black Brant

ABSTRACT.   Latitudinal variation in population structure during the winter has been reported in many migratory birds, but has been documented in few species of waterfowl. Variation in environmental and social conditions at wintering sites can potentially influence the population dynamics of differential migrants. We examined latitudinal variation in sex and age classes of wintering Pacific Black Brant ( Branta bernicla nigricans ). Brant are distributed along a wide latitudinal gradient from Alaska to Mexico during the winter. Accordingly, migration distances for brant using different wintering locations are highly variable and winter settlement patterns are likely associated with a spatially variable food resource. We used resightings of brant banded in southwestern Alaska to examine sex and age ratios of birds wintering at Boundary Bay in British Columbia, and at San Quintin Bay, Ojo de Liebre Lagoon, and San Ignacio Lagoon in Baja California from 1998 to 2000. Sex ratios were similar among wintering locations for adults and were consistent with the mating strategy of geese. The distribution of juveniles varied among wintering areas, with greater proportions of juveniles observed at northern (San Quintin Bay and Ojo de Liebre Lagoon) than at southern (San Ignacio Lagoon) locations in Baja California. We suggest that age-related variation in the winter distribution of Pacific Black Brant is mediated by variation in productivity among individuals at different wintering locations and by social interactions among wintering family groups.     

Production of substituted catechols from substituted benzenes by a Pseudomonas sp.

In the presence of a halobenzene or benzonitrile, Pseudomonas T-12 can produce substituted catechols from the corresponding substituted benzenes. A variety of monosubstituted benzenes with substituents containing up to four carbons, and some meta- and para- disubstituted benzenes, can serve as catechol precursors.     

Soluble minerals in chemical evolution

The adsorption of 5-AMP and 5-CMP was studied in saturated solutions of several soluble mineral salts (NaCl, Na₂SO₄, MgCl₂·6H₂O, MgSO₄·7H₂O, CaCl₂·2H₂O, CaSO₄·2H₂O, SrCl₂·6H₂O, SrSO₄, and ZnSO₄·7H₂O) as a function of pH, ionic strength, and surface area of the solid salt. The adsorption shows a pH dependence; this can be correlated with the charge on the nucleotide molecule which is determined by the state of protonation of the N-1 nitrogen of 5-AMP or N-3 nitrogen of 5-CMP and the phosphate oxygens. The adsorption which results from the binding between the nucleotide molecule and the salt surface is proposed as being due to electrostatic forces. It was concluded that the adsorption was reversible in nature. The adsorption shows a strong dependence upon ionic strength and decreases with increasing ionic strength. Surface area is shown to be an important factor in evaluating and comparing the magnitude of adsorption of nucleotides onto various mineral salts. The implications of the results of the study are discussed in terms of the importance of soluble mineral salts as adsorption sites in the characterization of the adsorption reactions of an adsorbed template in biogeochemical cycles.     

Phosphorylation heterogeneity of tryptic phosphopeptides of chicken riboflavin-binding protein

The tryptic phosphopeptide of hen egg white riboflavin-binding protein has been found to exist as a mixture of peptides which differ only with respect to the number of covalently bound phosphoryl groups. Anion-exchange chromatography was used to separate homologues of the tryptic phosphopeptide of egg white riboflavin-binding protein. Four peptide peaks were obtained and analyzed using plasma desorption mass spectrometry. Molecular ions obtained agree closely with calculated molecular weight values for phosphopeptides with 8, 7 and 5 phosphoryl groups. Amino acid analyses showed that the octa- and hepta-phosphorylated peptides were pure and had the same amino acid compositions.     

Optimization by simulating molecular evolution

Based on the analogy between mathematical optimization and molecular evolution and on Eigen's quasi-species model of molecular evolution, an evolutionary algorithm for combinatorial optimization has been developed. This algorithm consists of a versatile variation scheme and an innovative decision rule, the essence of which lies in a radical revision of the conventional philosophy of optimization: A number of configurations of variables with better values, instead of only a single best configuration, are selected as starting points for the next iteration. As a result the search proceeds in parallel along a number of routes and is unlikely to get trapped in local optima. An important innovation of the algorithm is introduction of a constraint to let the starting points always keep a certain distance from each other so that the search is able to cover a larger region of space effectively. The main advantage of the algorithm is that it has more chances to find the global optimum and as many local optima as possible in a single run. This has been demonstrated in preliminary computational experiments.     

Aqueous two-phase partition coefficients for Escherichia coli β-galactosidase fusions

The partition of native Escherichia coli -galactosidase and of two different fusion proteins comprised mainly of -galactosidase from E. coli was studied in aqueous two-phase systems composed of polyethylene glycol (PEG) and dextran. These fusions contain an amino-terminal segment from the E. coli outer membrane protein F (OmpF) and a linker peptide. Differences in the partition pattern could be observed for the three enzymes despite their similarity. Decreased polymer concentrations in the phase system increased the partition coefficient for all three -galactosidases.     

The effect of predation on the structure and invasibility of assembled communities

Summary Fifty four microcosmic communities were assembled over 4 months from a 28-species source pool of phytoplankton using nine different invasion patterns each replicated six times. Three communities from each set of replicates then were invaded with a cladoceran that feeds on phytoplankton. All communities were then treated identically for an additional 4 months. In all nine invasion categories species richness was greater in predated communities. Predation opened communities to invasion by increasing the representation of infrequently sampled species at the expense of more common species. Invasion rate was four times more influential than predation and over eleven times more important than either invasion order or the timing pattern of interspecific arrivals in determining species richness in this system of communitites.