Selection on innate immunity and body condition in Florida scrub-jays throughout an epidemic

Opportunities to investigate selection in free-living species during a naturally occurring epidemic are rare; however, we assessed innate immunocompetence in Florida scrub-jays before the population suffered the greatest over-winter mortality in 20 years of study. Propitiously, three months prior to the epidemic, we had sampled a number of male breeders to evaluate a suite of physiological measures that are commonly used to estimate the overall health-state of an individual. There was a significant, positive selection gradient for both Escherichia coli bacterial killing capability and body condition, suggesting that directional selection had occurred upon each of these traits during the disease epidemic.     

Very-Heavy Precipitation in the Greater New York City Region and Widespread Drought Alleviation Tied to Western US Agriculture

Observed intensification of precipitation extremes, responsible for extensive societal impacts, are widely attributed to anthropogenic sources, which may include indirect effects of agricultural irrigation. However quantifying the effects of irrigation on far-downstream climate remains a challenge. We use three paired Community Earth System Model simulations to assess mechanisms of irrigation-induced precipitation trends and extremes in the conterminous US and the effect on the terrestrial carbon sink. Results suggest precipitation enhancement in the central US reduced drought conditions and increased regional carbon uptake, while further downstream, the heaviest precipitation events were more frequent and intense. Specifically, moisture advection from irrigation in the western U.S. and recycling of enhanced local convective precipitation produced very-heavy storm events that were 11% more intense and occurred 23% more frequently in the densely populated greater New York City region.     

Singular Value Decomposition of the Radial Distribution Function for Hard Sphere and Square Well Potentials

We compute the singular value decomposition of the radial distribution function for hard sphere, and square well solutions. We find that decomposes into a small set of basis vectors allowing for an extremely accurate representation at all interpolated densities and potential strengths. In addition, we find that the coefficient vectors describing the magnitude of each basis vector are well described by a low-order polynomial. We provide a program to calculate in this compact representation for the investigated parameter range.     

Defensive secretions of larvae of a carabid beetle

Secretions of an eversible gland on the metathorax of larvae of Chlaenius cordicollis Kirby (Coleoptera: Carabidae) are investigated by headspace analysis using solid phase microextraction followed by gas chromatography‐mass spectrometry (GC‐MS). Larvae from Manitoba, Canada and Pennsylvania, U.S.A., are sampled. Nine presumed defensive compounds are detected when the gland is everted, and this represents the first characterization of defensive secretions of larvae of a carabid beetle. With the exception of a single component (2‐methoxy‐4‐methylphenol), these compounds are distinct from those found in the defensive secretion of adult C. cordicollis. However, seven are more oxidized versions of the alkylphenolic compounds secreted by adult beetles: three hydroquinones (hydroquinone, methylhydroquinone and 2,3‐dimethylhydroquinone) and four quinones (p‐benzoquinone, toluquinone, 2,3‐dimethylquinone and ethyl‐p‐benzoquinone). An additional alkoxyphenol (2‐methoxy‐4‐ethylphenol) is also detected. Two patterns of composition are observed: in one, p‐benzoquinone and hydroquinone are undetectable and the ratio of toluquinone : 2,3‐dimethylquinone is 1 : 4.6 ± 0.6 (mean ± SE); in the other, all nine compounds are detectable and the ratio of toluquinone : 2,3‐dimethylquinone is 1 : 1.0 ± 0.2. These differences in pattern do not appear to be related to geographical source, sex or age of the larvae.     

Structural and functional characterization of second-coordination sphere mutants of soybean lipoxygenase-1.

Lipoxygenases are an important class of non-heme iron enzymes that catalyze the hydroperoxidation of unsaturated fatty acids. The details of the enzymatic mechanism of lipoxygenases are still not well understood. This study utilizes a combination of kinetic and structural probes to relate the lipoxygenase mechanism of action with structural modifications of the iron's second coordination sphere. The second coordination sphere consists of Gln(495) and Gln(697), which form a hydrogen bond network between the substrate cavity and the first coordination sphere (Asn(694)). In this investigation, we compared the kinetic and structural properties of four mutants (Q495E, Q495A, Q697N, and Q697E) with those of wild-type soybean lipoxygenase-1 and determined that changes in the second coordination sphere affected the enzymatic activity by hydrogen bond rearrangement and substrate positioning through interaction with Gln(495). The nature of the C-H bond cleavage event remained unchanged, which demonstrates that the mutations have not affected the mechanism of hydrogen atom tunneling. The unusual and dramatic inverse solvent isotope effect (SIE) observed for the Q697E mutant indicated that an Fe(III)-OH(-) is the active site base. A new transition state model for hydrogen atom abstraction is proposed.     

Temporal mechanisms influencing gender expression and pollen flow within a self-incompatible perennial,Amianthium muscaetoxicum (Liliaceae)

Summary Temporal mechanisms that influence the synchrony of gender expression and the patterns of withinplant pollen flow were examined in Amianthium muscatoxicum. In this species self-incompatible pollinations can clog stigmas, interfere with the growth of outcrossed pollen tubes, and reduce fecundity. The majority of flowers have partial dichogamy: a two-day period of pollen dehiscence and a four-day period of pollen viability are nested in a six-day period of pistil viability. An indeterminate flowering sequence among flowers on the same plant and partial dichogamy within flowers help reduce pollen flow within the whole plant. The combined effects at both of these levels should reduce pollen wastage and lower the incidence of stigma clogging by incompatible self pollen.     

Effect of Inhibition of Glycosylation on the Appearance of a 60 kD Membrane Glycopolypeptide in Endomembrane Fractions of Soybean Root

Endomembrane (endoplasmic reticulum, Golgi apparatus, plasma membrane) proteins of soybean (Glycine max) root cells are highly glycosylated. We investigated whether N-linked oligosaccharide moieties are essential for the correct intracellular transport of plant endomembrane glycoproteins. Excised roots were incubated with tunicamycin, to block cotranslational glycosylation of proteins, and dual labeled with [³H]glucosamine and [³⁵S] (methionine, cysteine). In the presence of tunicamycin, the incorporation of glucosamine into membrane proteins was inhibited by 60 to 90% while amino acid incorporation was only slightly affected. Autoradiograms of two-dimensionally separated polypeptides from each endomembrane fraction revealed the presence of at least one new polypeptide in tunicamycin-treated tissue. The new polypeptide was of the same isoelectric point but lower molecular weight than a preexisting polypeptide. The new polypeptide was unreactive to concanavalin A, as opposed to the preexisting polypeptide, suggesting the absence of the glycan portion. Trifluoromethanesulfonic acid and N-glycanase were used to cleave the carbohydrate from the preexisting concanavalin A binding polypeptide. In each case a deglycosylated polypeptide of the same isoelectric point and molecular weight as the new polypeptide from tunicamycin-treated tissue resulted. Since the absence of carbohydrate from the new endomembrane polypeptide did not prevent its appearance on autoradiograms of Golgi and plasma membrane, intracellular transport and intercalation of newly synthesized glycoproteins into plant cell membranes may not require the presence of polysaccharide moieties.     

The primary role of the P1 residue (ser359) of alpha-1-proteinase inhibitor

The replacement of ser359 with ala359 at the P1 position in human alpha-1-proteinase inhibitor results in the production of a variant protein containing 15% of the inhibitory activity of the normal inhibitor. Separation of active from inactive inhibitor on anhydrochymotrypsin-sepharose yields a form which has a second order association rate with neutrophil elastase which is approximately one half that for the native protein. These data indicate that the P1 residue is not of primary importance during the interaction of proteinases with alpha-1-proteinase inhibitor. Since substitution of alanine for serine causes the formation, primarily, of inactive inhibitor the major function of ser359 probably involves proper folding to give a functionally active inhibitory conformation.     

Stabilization vs. degradation of Staphylococcus aureus metalloproteinase

Purified Staphylococcus aureus metalloproteinase contains trace amounts of a serine proteinase which rapidly degrades the metalloproteinase when EDTA is present. However, no degradation occurs when Ca2+ is added or if the serine proteinase is removed by immunoaffinity chromatography. Selective chelation of Zn2+ by o-phenanthroline, which reversibly inactivates the metalloproteinase, does not result in the degradation of the apometalloproteinase, even with excess of serine proteinase. These data are interpreted as follows: EDTA chelates enzyme-bound Ca2+ and Zn2+, causing irreversible inactivation as well as a conformational change in the metal-free protein. This allows proteolysis by the contaminating serine proteinase and explains why the metalloproteinase purified from serine proteinase-deficient strains of S. aureus was previously thought to be stable to autolysis.