Simultaneous determination of thermodynamic and kinetic parameters of aminopolycarbonate complexes of cobalt(II) and nickel(II) based on isothermal titration calorimetry data

The influence of the different side chain residues on the thermodynamic and kinetic parameters for complexation reactions of the Co²⁺ and Ni²⁺ ions has been investigated by using the isothermal titration calorimetry (ITC) technique supported by potentiometric titration data. The study was concerned with the 2 common tripodal aminocarboxylate ligands, namely, nitrilotriacetic acid and N‐(2‐hydroxyethyl) iminodiacetic acid. Calorimetric measurements (ITC) were run in the 2‐(N‐morpholino)ethanesulfonic acid hydrate (2‐(N‐morpholino) ethanesulfonic acid), piperazine‐N ,N ′‐bis(2‐ethanesulfonic acid), and dimethylarsenic acid buffers (0.1 mol L⁻¹, pH 6) at 298.15 K. The quantification of the metal‐buffer interactions and their incorporation into the ITC data analysis enabled to obtain the pH‐independent and buffer‐independent thermodynamic parameters (K , ΔG , ΔH , and ΔS ) for the reactions under study. Furthermore, the kinITC method was applied to obtain kinetic information on complexation reactions from the ITC data. Correlations, based on kinetic and thermodynamic data, between the kinetics of formation of Co²⁺ and Ni²⁺ complexes and their thermodynamic stabilities are discussed.     

Torsional and Bending Rigidity of the Double Helix from Data on Small DNA Rings

Abstract

We have calculated the variance of equilibrium distribution of a circular wormlike polymer chain over the writhing number, ?(Wr)²?, as a function of the number of Kuhn statistical segments, n, For large n these data splice well with our earlier results obtained for a circular freely jointed polymer chain. Assuming that ?(ΔLk)²? = ?(ΔTw)²? + ?(Wr)²? we have compared our results with experimental data on the chain length dependence of the ?(ΔLk) ²? value recently obtained by Horowitz and Wang for small DNA rings. This comparison has shown an excellent agreement between theory and experiment and yielded a reliable estimate of the torsional and bending rigidity parameters. Namely, the torsional rigidity constant is C = 3.0·10^?19 erg cm, and the bending rigidity as expressed in terms of the DNA persistence length is a = 500 A. The obtained value of C agrees well with earlier estimates by Shore and Baldwin as well as by Horowitz and Wang whereas the a value is in accord with the data of Hagerman. We have found the data of Shore and Baldwin on the chain length dependence of the ?(ΔLk) ²? value to be entirely inconsistent with our theoretical results.     

THE ALLOMETRY OF PLANT REPRODUCTIVE BIOMASS AND STEM DIAMETER

The allometry of reproductive biomass M was determined for one moss (Polytrichum commune), four pteridophytes (Psilophyton princeps, Psilotum nudum, Lycopodium lucidulum, and L. clavatum), six gymnosperms (Larix decidua, Pseudotsuga douglasii, Tsuga canadensis, Pinus rigida, Picea abies, and Taxus baccata), and two angiosperms (Crataegus sp. and Quercus bicolor). Biomass M was measured for individual and grouped reproductive organs and regressed as a function of stem diameter D measured proximal to M for representative reproductive stems from each species. Published data for Cooksonia pertoni were used to estimate sporangial M. The data from this vascular plant fossil were compared to those from other species. Least squares regression of the entire data set yielded M = 0.12D²,⁹ (r² = 0.94, N = 215), indicating that M, on the average, compiled with M D^α3.0. The allometries of the moss, pteridophyte, gymnosperm, and angiosperm species, however, were M = 0.46D^4.6 (r² = 0.99, N = 41), M = 0.07D^3.2 (r² = 0.91, N = 65), M = 0.56D^2.2 (r² = 0.92, N =85), and M = 0.44D^1.8 (r² = 0.97, N = 21), respectively, indicating that the proportionality M D^α3.0. recedes with finer taxonomic resolution. The data for Cooksonia were found to comply with the allometry of Polytrichum when the regression curve of this moss was extrapolated into the size range of the fossil species. Analyses showed that intraspecific allometric scaling factors α were dependent upon the manner in which plant stems taper. Species or portions of branching systems with α >; 4.0 had essentially untapered stems (e.g., Polytrichum commune, Psilotum nudum, twigs of Larix decidua); species with α <; 2.2 had tapered stems resulting from secondary growth in most cases. The evolution of tapered primary stems and secondary growth was interpreted to alter reproductive allometry.     

Limiting the sedimentation coefficient for sedimentation velocity data analysis: partial boundary modeling and g(s) approaches revisited

Brown and coworkers (Eur. Biophys. J. 38 (2009) 1079–1099) introduced partial boundary modeling (PBM) to simplify sedimentation velocity data analysis by excluding species outside the range of interest (e.g., aggregates, impurities) via restricting the sedimentation coefficient range being fitted. They strongly criticized the alternate approach of fitting g(s^∗) distributions using similar range limits, arguing that (i) it produces “nonoptimal fits in the original data space” and (ii) the g(s^∗) data transformations lead to gross underestimates of the parameter confidence intervals. It is shown here that neither of those criticisms is valid. These two approaches are not truly fitting the same data or in equivalent ways; thus, they should not actually give the same best-fit parameters. The confidence limits for g(s^∗) fits derived using F statistics, bootstrap, or a new Monte Carlo algorithm are in good agreement and show no evidence for significant statistical distortion. Here 15 g(s^∗) measurements on monoclonal antibody samples gave monomer mass estimates with experimental standard deviations of less than 1%, close to the confidence limit estimates. Tests on both real and simulated data help to clarify the strengths and drawbacks of both approaches. New algorithms for computing g(s^∗) and a scan-differencing approach for PBM are introduced.     

Dynamic light scattering from thin rigid rods: Anisotropy of translational diffusion of tobacco mosaic virus

An Exact theoretical expression for the apparent diffusion coefficient D_app(K) of a thin rigid rod with arbitrary anisotropy of its translational diffusion diffusion coefficient is derived from the first cumulant of its dynamic structure factor. D_app(K) is predicted to reach a limiting plateau value at extermely large values of KL, where K is the scattering vector and L the rod length. Howerver, that limiting plateau value is approached only very slowly along a quasi-plateau with a very gradual slope. Dynamic light-scattering studies have been performed on tobacco mosaic virus from K² = (0.4–20) × 10¹⁰ cm^?2 using 632-8-nm laser radiation. The present data yield D₀ = (4.19 ± 0.10) × 10^?8 cm²/s (corrected to 20,w conditions) and, with literature data to establish L = 2980 Å and the rotational diffusion coefficient D_R = 318s^?1, yield also Δ ≡ D_∥ ? D_⊥ = (1.79 ± 0.38) × 10^?8 cm²/s. The experimental data closely follow the curve of D_app(K) vs K² calcuated for these parameters. The present value of D₀ substantially exceeds all previous dynamic light-scattering values, but is in good aggreement with previous sedimentation data, which were confirmed for the presemt sample. The anisotropy ratio Δ/D₀ = 0.43 ± 0.09 is in accord with theoretical predictions based on the modified Kirkwood algorithm, despite the fact the D₀ lies significantly below its corresponding theoretical value. The present data largely predlude the possibility that both D₀ and Δ/D₀ could simultaneously match their theoretical predictions. We present a detailed comparison of the experimental data with the calculations of Tirado and Garcia de la Torre based on the modified Kirkwood algorithm and with the Broersma formulas.     

Effect of Intracluster Correlation on the R-Square Statistic

R²-statistic is a popular and very widely used statistic in regression analysis to estimate the square multiple correlation (SMC), ρ², between a response variable Y and p predictor variables, _X1, …, _Xp. Numerous articles are available in the statistical literature on the properties of R² as an estimator of ρ² when the observations are uncorrelated. However, relatively little is known about the behavior of R² when the available observations are correlated such as the data that result from complex sampling schemes. In this paper, we study the behavior R² in the presence of two-stage sampling data. An approximate expressions for the variance and the bias of R² in the presence of two-stage cluster sampling data with positive intracluster correlation (ρ*) are obtained. It is evident from these formulas and from a simulation study that R² is a poor estimator of ρ² except when ρ* is small. As such, we consider several alternative estimators of ρ² and evaluate their theoretical properties and finite sample performance using a simulation study.     

Molecular analysis of HLA-B39 subtypes

Serological studies have suggested the presence of a new HLA-B39 subtype (B39.2) in the Japanese population. To identify the new HLA-B39 subtype and compare it with an other HLA-B39 subtype (B39.1), the genes encoding HLA-B39.1 (B ^* 39013) and B39.2 (B ^* 3902) have been cloned from Japanese. We have sequenced these genes and completed the sequence of HLA-B39.1 (B ^*39011 ) gene from a Caucasian that was partially sequenced. Comparison of the sequence data revealed that B ^* 3902 and B ^* 39013 differ by three nucleotide substitutions which result in a two amino acids change at residues 63 and 67, while one silent substitution at codon 312 is found between B ^* 39011 and B ^* 39013. These results suggest that B ^* 3902 has evolved from B ^* 39013 rather than B ^* 39011.The nucleotide sequence data reported in this paper have been submitted to the GenBank nucleotide sequence database and have been assigned the accession numbers M94051 (HLA-B^*39013), M94052 (HLA-B^*39011), and M94053 (HLA-B^*3902).     

A suite of Mathematica notebooks for the analysis of protein main chain 15N NMR relaxation data

A suite of Mathematica notebooks has been designed to ease the analysis of protein main chain ¹⁵N NMR relaxation data collected at a single magnetic field strength. Individual notebooks were developed to perform the following tasks: nonlinear fitting of ¹⁵N-T ₁ and -T ₂ relaxation decays to a two parameter exponential decay, calculation of the principal components of the inertia tensor from protein structural coordinates, nonlinear optimization of the principal components and orientation of the axially symmetric rotational diffusion tensor, model-free analysis of ¹⁵N-T ₁, -T ₂, and {¹H}–¹⁵N NOE data, and reduced spectral density analysis of the relaxation data. The principle features of the notebooks include use of a minimal number of input files, integrated notebook data management, ease of use, cross-platform compatibility, automatic visualization of results and generation of high-quality graphics, and output of analyses in text format.L. Spyracopoulos is an AHFMR Medical Research Senior Scholar     

Characterization of the backbone dynamics of an anti-digoxin antibody VL domain by inverse detected 1H–15N NMR: Comparisons with X-ray data for the Fab

The dynamic behavior of the polypeptide backbone of a recombinant anti-digoxin antibody V_L domain has been characterized by measurements of ¹⁵N T₁ and T₂ relaxation times, ¹H–¹⁵N NOE values, and ¹H–²H exchange rates. These data were acquired with 2D inverse detected heteronuclear ¹H–¹⁵N NMR methods. The relaxation data are interpreted in terms of model free spectral density functions and exchange contributions to transverse relaxation rates R₂ (= 1/T₂). All characterized residues display low-amplitude picosecond timescale librational motions. Fifteen residues undergo conformational changes on the nanosecond timescale, and 24 residues have significant R₂ exchange contributions, which reflect motions on the microsecond to millisecond timescale. For several residues, microsecond to millisecond motions of nearby aromatic rings are postulated to account for some or all of their observed R₂ exchange contributions. The measured ¹H–²H exchange rates are correlated with hydrogen bonding patterns and distances from the solvent accessible surface. The degree of local flexibility indicated by the NMR measurements is compared to crystallographic B-factors derived from X-ray analyses of the native Fab and the Fab/digoxin complex. In general, both the NMR and X-ray data indicate enhanced flexibility in the turns, hypervariable loops, and portions of β-strands A, B, and G. However, on a residue-specific level, correlations among the various NMR data, and between the NMR and X-ray data, are often absent. This is attributed to the different dynamic processes and environments that influence the various observables. The combined data indicate that certain regions of the V_L domain, including the three hypervariable loops, undergo dynamic changes upon V_L:V_H association and/ or complexation with digoxin. Overall, the 26–10 V_L domain exhibits relatively low flexibility on the ps–ns timescale. The possible functional consequences of this result are considered. © 1993 Wiley-Liss, Inc.     

Bioremediation Potential of Chlorella: Spectroscopic,Kinetics, and Sem Studies

A dead dried alga, Chlorella sp., was used for the uptake of Cr⁺³, Cr₂O₇ ^?2, Cu⁺², and Ni⁺² from the aqueous solutions of these metal ions. The equilibrium data were fitted using the Langmuir and Freundlich isotherm model and the maximum uptakes for Cr⁺³, Cr₂O₇ ^?2, Ni⁺², and Cu⁺² were 98, 104, 108, and 183 mg/g, respectively. The Freundlich model, in comparison to the Langmuir model, better represented the sorption process. The kinetics of metal ions uptake by Chlorella sp. was best described by a pseudo-second order rate equation. Infrared spectroscopic data were employed to identify the site(s) of bonding in Chlorella sp. A scanning electron microscopic (SEM) study of pure dead Chlorella sp. and the species treated with different metal ions provided an idea of the extent of metal uptake by this species. The dead Chlorella sp took up maximum Cu(II). The size of the cell of the metal-treated Chlorella sp. obtained from SEM data is in agreement with the extent of metal uptake.     

Temperature dependence of the dynamic light scattering of linear phi 29 DNA: implications for spontaneous opening of the double-helix

The apparent diffusion coefficient D_app(K) of a single sample of linear ?29 DNA (M_r = 11.5 × 10⁶) has been measured as a function of K² from 0.21 × 10¹⁰ to 20 × 10¹⁰ cm^?2 at a variety of temperatures from ?0.5 to +70°C. D_app(K) scales closely as T/η at every value of K². All of these data are simulated by a particular Rouse-Zimm model comprised of a constant number of subchains with constant rms subchain extension b = 1057 Å and an apparent subchain diffusion coefficient D_plat that scales at T/η from ?0.5 to +70°C. It is inferred from these results that any temperature dependence of the flexural and torsional rigidities of DNA must be rather weak. A less firm inference is that these rigidities actually increase slightly with temperature, possibly in proportion to T, which is weak T dependence in this context. These findings eliminate the possibility that spontaneous transient opening of the DNA structure has any significant effect on the flexural and torsional rigidities of the DNA filament. A review of the most pertinent available data from other experiments concerning spontaneous transient opening of the DNA is presented. The formaldehyde kinetics data do not unequivocally implicate an open base-pair intermediate and provide only an upper limit to the fraction of open base pairs. An alternative nonopening model with a protonated doorway state is proposed to accommodate the hydrogen-exchange data. It is concluded that there is presently no incontrovertible evidence for a fraction of unstacked open base pairs greater than about 10^?4.     

Various X2-Tests of Homogeneity: Some Comments

Methodological issues in the analysis of incidence rates or prevalence proportions for count data, presented in a form of a sequence of 2×2 tables, corresponding to levels (strata) of a specified variable (risk factor) X, are discussed. Suppose λ_1i and λ_2i are the incidence rates of an event D in the ith stratum for populations 1 and 2, respectively. The homogeneity (null) hypothesis is formulated in the form: H_0:λ1i=λ_2i for all i (i = 1, 2, …, I). Three X²-tests for H₀ and their theoretical bases are discussed: X_Total² which is sensitive to alternatives HA :λ1i± λ2i for at least some i; X_Comb² which is sensitive to alternatives H A : λ1iλ2i² or < λ_2i but not both for all i; and X_Diff² which is sensitive to alternatives H_A:λ1i>λ2i³ for some i and λ_1i′ < λ_2i′ for some i′ (i≠i′). These statistics satisfy the relation X_Total² = X_Comb² + X_Diff². Also, X′²-statistic for pooled data is calculated, which in conjunction with X_Comb² can serve for detecting confounding. Although most of these techniques are known, they are rather scattered in the literature, and not always considered jointly, as it is emphasized in the present paper. It is hoped that these comments will be helpful to biostatisticians as well as to epidemiologists and medical researchers in the analysis of mortality and morbidity data. For illustration, two examples with large sets of epidemiological data are given.     

Effects of fasting and nutritional restriction on the isotopic ratios of nitrogen and carbon: a meta‐analysis

Many organisms experience fasting in their life time, and this physiological process has the potential to alter stable isotope values of organisms, and confound interpretation of food web studies. However, previous studies on the effects of fasting and starvation on stable isotopes show disparate results, and have never been quantitatively synthesized. We performed a laboratory experiment and meta‐analysis to determine how stable isotopes of δ¹⁵N and δ¹³C change with fasting, and we tested whether moderators such as taxa and tissue explain residual variation. We collected literature data from a wide variety of taxa and tissues. We surveyed over 2000 papers, and of these, 26 met our selection criteria, resulting in 51 data points for δ¹⁵N, and 43 data points for δ¹³C. We determine that fasting causes an average increase in the isotopic value of organisms of 0.5‰ for δ¹⁵N and that the only significant moderator is tissue type. We find that the overall effect size for δ¹³C is not significant, but when the significant moderator of tissue is considered, significant increases in blood and whole organisms are seen with fasting. Our results show that across tissues and taxa, the nutritional status of an organism must be considered when interpreting stable isotope data, as fasting can cause large differences in stable isotope values that would be otherwise attributed to other factors.     

Pigmentiphaga soli sp. nov., a bacterium isolated from soil

Strain BS12^T, a Gram-negative motile bacterium, was isolated from soil in South Korea and characterized to determine its taxonomic position. Phylogenetic analyses based on the 16S rRNA gene sequence revealed that the strain belonged to the family Alcaligenaceae in the class Betaproteobacteria. The highest degree of sequence similarities of strain BS12^T were found with Pigmentiphaga litoralis JSM 061001^T (98.3%), Pigmentiphaga daeguensis K110^T (98.2%), and Pigmentiphaga kullae K24^T (98.1%). Chemotaxonomic data revealed that strain BS12^T possessed ubiquinone-8, which is common in the family Alcaligenaceae, and the predominant fatty acids were C_16:0, C_17:0 cyclo, summed feature 3 (C_16:1 ω6c/ω7c), and summed feature 8 (C_18:1 ω6c/ω7c). The major polar lipids of strain BS12^T were phosphatidylethanolamine and phosphatidylglycerol. Based on these data, BS12^T (=KCTC 23577^T =JCM 17666^T =KEMB 9004-082^T) should be classified as a type strain of a novel species, for which the name Pigmentiphaga soli sp. nov. is proposed.     

Complete H and C NMR chemical shift assignments of mono-, di-, and trisaccharides as basis for NMR chemical shift predictions of polysaccharides using the computer program casper

The computer program casper uses ¹H and ¹³C NMR chemical shift data of mono- to trisaccharides for the prediction of chemical shifts of oligo- and polysaccharides. In order to improve the quality of these predictions the ¹H and ¹³C, as well as ³¹P when applicable, NMR chemical shifts of 30 mono-, di-, and trisaccharides were assigned. The reducing sugars gave two distinct sets of NMR resonances due to the α- and β-anomeric forms. In total 35 ¹H and ¹³C NMR chemical shift data sets were obtained from the oligosaccharides. One- and two-dimensional NMR experiments were used for the chemical shift assignments and special techniques were employed in some cases such as 2D ¹H,¹³C-HSQC Hadamard Transform methodology which was acquired approximately 45 times faster than a regular t₁ incremented ¹H,¹³C-HSQC experiment and a 1D ¹H,¹H-CSSF-TOCSY experiment which was able to distinguish spin-systems in which the target protons were only 3.3 Hz apart. The ¹H NMR chemical shifts were subsequently refined using total line-shape analysis with the PERCH NMR software. The acquired NMR data were then utilized in the casper program (http://www.casper.organ.su.se/casper/) for NMR chemical shift predictions of the O-antigen polysaccharides from Klebsiella O5, Shigella flexneri serotype X, and Salmonella arizonae O62. The data were compared to experimental data of the polysaccharides from the two former strains and the lipopolysaccharide of the latter strain showing excellent agreement between predicted and experimental ¹H and ¹³C NMR chemical shifts.     

Amycolatopsis bartoniae sp. nov. and Amycolatopsis bullii sp. nov., mesophilic actinomycetes isolated from arid Australian soils

The status of two mesophilic filamentous actinomycetes isolated from an arid Australian soil sample was determined using a polyphasic taxonomic approach. The isolates had chemical and morphological properties consistent with their classification in the genus Amycolatopsis, assignments that were supported by analysis of 16S rRNA gene sequence data. Isolate SF26^T formed a distinct phyletic line and hence was sharply separated from its nearest phylogenetic neighbour, Amycolatopsis sacchari DSM 44468^T. In contrast, isolate SF27^T formed a subclade in the Amycolatopsis tree with Amycolatopsis vancoresmycina DSM 44592^T but was separated readily from the latter by DNA:DNA pairing data. The two isolates were distinguished from one another and from their respective nearest phylogenetic neighbours using a range of phenotypic properties. These data indicate that the two isolates should be recognized as new species in the genus Amycolatopsis. The names proposed for these new taxa are Amycolatopsis bartoniae sp. nov. and Amycolatopsis bullii sp. nov. with isolates SF26^T (=NCIMB 14706^T = NRRL B-2846^T) and SF27^T (=NCIMB 14707^T = NRRL B-24847^T) as the respective type strains.     

THE SCALING OF PLANT AND ANIMAL BODY MASS,LENGTH, AND DIAMETER

The interspecific scaling exponents of body mass M and diameter D with respect to length L were determined to evaluate the predictions of three scaling hypotheses (geometric, stress, and elastic similitude). The relation between M and L was determined for data from a total of 133 aquatic and terrestrial species (66 plant and 67 animal species); the relation between D and L was determined independently for a total of 753 aquatic and terrestrial species (667 plant and 86 animal species). Organisms were crudely classified as to their geometry (spheres, spheroids, cylinders) and shape (defined as the body slenderness factor, L/D) to examine whether geometry and shape evinced size-dependent variations. Regression indicated M = 1.29L^2.95 (r² = 0.91, N = 133; α_RMA = 3.09 ± 0.088). The stress and elastic similitude (which respectively predict α_RMA = 5 and α_RMA = 4) were rejected; geometric similitude was not (α_RMA = 3). For animals and plants, α_RMA = 2.81 ± 0.061 (r² = 0.98), and α_RMA = 2.95 ± 0.093 (r² = 0.94), respectively. For aquatics and terrestrial organisms, α_RMA = 2.82 ±0.134 (r² = 0.97, N = 36), and α_RMA = 3.08 ±0.111 (r² = 0.89, N = 97), respectively. These results were interpreted to support the hypothesis of geometric similitude. For the pooled plant and animals data, D = 0.05L^1.00 (r² = 0.95; α_RMA = 1.03 ± 0.009), which was compatible with the hypothesis of geometric similitude. For plants, D = 0.05L^1.06 (r² = 0.95; α_RMA = 1.09). For animals, D = 0.29L^0.98 (r² = 0.95; α_RMA = 1.01 ± 0.025). Also, for aquatics, α_RMA = 0.951 ± 0.151, whereas for terrestrial plants and animals, α_RMA = 1.03 ± 0.089. Although the scaling exponent for D differed among individual groupings of animals and plants, the results of regression analyses were interpreted to indicate that, on the average, body diameter scaled isometrically with respect to length as predicted by geometric similitude. For the pooled data set, organic shape varied over 3 orders of magnitude; L varied over 9 orders of magnitude reflecting 22 orders of magnitude of M. In terms of body geometry and the absolute numbers of species in the total data set: spherical shaped species (L = D) < unassigned species < prolate spheroidal species < cylindrical (squat < slender) species. The largest organisms in the data set were slender (L/D > 20) cylindrical plants; the smallest organisms were spherical plants and animals. Although not subject to statistical inference, these data were interpreted to indicate that organic shape and geometry evince size-dependent variations. These variations as well as size-dependent changes in bulk density are hypothesized to account for the scaling exponents of M and D determined for individual plant and animal clades and grades.     

The relative orientation of the fibronectin 6F11F2 module pair: A 15N NMR relaxation study

The structure of a pair of modules (⁶F1¹F2), that forms part of the collagen-binding region of fibronectin, is refined using heteronuclear relaxation data. A structure of the pair was previously derived from ¹H-¹H NOE and ³ J _HHN data [Bocquier et al. (1999) Structure, 7, 1451–1460] and a weak module–module interface, comprising Leu19 and Leu28, in ⁶F1, and Tyr68 in ²F1, was identified. In this study, the definition of the average relative orientation of the two modules is improved using the dependence of ¹⁵N relaxation on rotational diffusion anisotropy. This structure refinement is based on the selection of a subset of structures from sets calculated with NOE and ³ J _HHN data alone, using the quality of the fits to the relaxation data as the selection criterion. This simple approach is compared to a refinement strategy where ¹⁵N relaxation data are included in the force field as additional restraints [Tjandra et al. (1997) Nat. Struct. Biol., 4, 443–449].     

Gastric evacuation rates of white perch,Morone americana,determined from laboratory and field data

Synopsis Gastric evacuation rates (R) of white perch,Morone americana, were determined in laboratory experiments and by using field data. The resulting relationship ofR and temperature (T) for white perch wasR = 0.028e^0.106T (r² = 0.98). The high r² of the regression indicates good agreement of the combined laboratory and field data. Our rate compares well with those available for other species; and especially for Eurasian perch, which has a similar thermal existence to white perch in Lake Erie.     

The molecular basis of potassium nutrition in plants

Over the last five years, the cloning and characterization of K⁺ transport genes corresponding to K⁺ channels (KAT1, AKT1, KST1, AKT2), associated subunits (KAB1) and a high-affinity transporter (HKT1) has opened up important new avenues for research on plant K⁺ nutrition. With the abundance of molecular data now available it seems timely to link this information with the wealth of data previously accumulated on the physiology of plant K⁺ acquisition. The ultimate goal of all this research is to gain a better understanding of K⁺ transport and nutrition in the intact plant. Thus it is important to begin to integrate the molecular research with results from biochemical and physiological research conducted at the cellular, root and whole plant levels. This article will focus on describing the features of the cloned K⁺ transporters and their possible roles in mediating high- and low-affinity K⁺ uptake from the soil, as well as how K⁺ acquisition may be regulated.Abbreviations NEM N-ethyl maleimide - PCMBS p-chloromercuribenzene sulphonic acid