Detroit River Flow Characteristics and their Application to Chemical Loading Estimates1

Unsteady flow characteristics were analyzed at the Windmill Point, Fort Wayne, Wyandotte, and Fermi sections of the Detroit River using two hydraulic transient mathematical models. Both models consist of the complete one-dimensional equations of continuity and motion and were calibrated using discharge measurements taken during the 1963-1973 period. The models were used to generate hourly, daily, and monthly flows for the year 1968. A statistical analysis was made of these flows at the Fort Wayne and Fermi sections. The flows at the Fort Wayne section were found to be representative of the entire river on a monthly basis and on a daily basis under most conditions. Individual section flows are necessary for use on an hourly basis or under Lake Erie wind, tide and seiche conditions. Application of flows to computation of Detroit River chloride loadings shows entirely different loading phenomena for both base and peak loadings between the upper and lower river. It also illustrates the danger of computing yearly loadings based upon a limited number of samples for the lower river.     

The purification and specificity of a lipase fromVernonia anthelmintica seed

Acetone powders prepared fromVernonia anthelmintica seed catalyzed the release of 6.4 to 9.6 μ-moles of free fatty acids per milligram of protein when blended with olive oil and phosphate buffer and shaken for 20 min at 43 C. A 20 fold purification was achieved by differential centrifugation of an ammonium hydroxide extract of the acetone powder. Results from Sephadex G-200 chromatography and polyacrylamide gel electrophoresis suggested that the lipase activity was associated with a molecule of molecular weight greater than 200,000. Free fatty acids, 1,2- and 1,3-diglycerides, monoglycerides and glycerol were found in the digestion products. With most substrates the 1,2-to 1,3-diglyceride ratio was approximately 2∶1 and monoglycerides tended to accumulate. Analysis of the digestion products from synthetic triglycerides of known structure indicated that both primary and secondary ester positions of the triglyceride molecule were hydrolyzed and that considerable isomerization of 1,2-diglyceride to 1,3-diglyceride occurred. The monoglyceride was consistently lower than the 1,2-diglyceride and in the majority of cases also lower than the 1,3-diglyceride in the fatty acid originally present in the 2 position of the triglyceride. No fatty acid preference was observed. Scientific contribution No. 316. Presented in part at the AOCS Meeting, Philadelphia, October 1966.     

Screening for noncovalent ligand-receptor interactions by electrospray ionization mass spectrometry-based diffusion measurements

The application of a novel method for the identification of low-molecular-weight noncovalent ligands to a macromolecular target is reported. This technique is based on the measurement of analyte diffusion coefficients by electrospray mass spectrometry (ESI-MS) (Clark et al., Rapid Commun. Mass Spectrom. 2002, 16, 1454-1462). Potential ligands have large diffusion coefficients as long as they are free in solution. Binding to a macromolecular target, however, drastically reduces the diffusional mobility of any ligand species. Mixtures containing six different saccharides [ribose, rhamnose, glucose, maltose, maltotriose, and N,N',N'-triacetylchitotriose (NAG(3))] were screened for noncovalent binding to lysozyme. Of these six compounds, only NAG(3) is known to bind to the protein. In "direct" binding tests, NAG(3) shows a significantly reduced diffusion coefficient in the presence of the protein. No changes were observed for any of the other saccharides. In a second set of experiments, the use of a "competition" screening method was explored in which mixtures of candidate saccharides were tested for their ability to displace a reference ligand from the target. The addition of NAG(3)-containing mixtures significantly increased the diffusion coefficient of the reference ligand NAG(4) (N,N',N',N'-tetraacetylchitotetrose), whereas mixtures that did not contain NAG(3) had no effect. These data clearly indicate the potential of ESI-MS-based diffusion measurements as a novel tool to screen compound libraries for binding to proteins and other macromolecular targets. In contrast to conventional ESI-MS-based ligand-receptor binding studies, this method does not rely on the preservation of noncovalent interactions in the gas phase.     

Determination of ligand-protein dissociation constants by electrospray mass spectrometry-based diffusion measurements

A novel approach for the quantification of ligand-protein interactions is presented. Electrospray ionization mass spectrometry (ESI-MS) is used to monitor the diffusion behavior of noncovalent ligands in the presence of their protein receptors. These data allow the fraction of free ligand in solution to be determined, such that the corresponding dissociation constants can be calculated. A set of conditions is developed that provides an "allowable range" of concentrations for this type of assay. The method is tested by applying it to two different inhibitor-enzyme systems. The dissociation constants measured for benzamidine-trypsin and for N,N',N' '-triacetylchitotriose-lysozyme are (50 +/- 10) and (6 +/- 1) mM, respectively. Both of these results are in good agreement with previous data from the literature. In contrast to traditional ESI-MS-based methods, the approach used in this work does not rely on the preservation of specific solution-type noncovalent interactions in the gas phase. It is shown that this method allows an accurate determination of dissociation constants, even in cases in which the ion abundance ratio of free to ligand-bound protein in ESI-MS does not reflect the corresponding concentration ratio in solution.     

Reliability of scanning electron microscopy information

The reliability of information obtained with the scanning electron microscope is influenced by human and instrumental factors. The human factor enters, for example, when a microstructure is described as being typical of the material when in fact it is only a minor component. Some instrumental factors include charging of the specimen, problems differentiating between positive and negative relief and distortion of the shape of the sample in micrographs. The determination of the amount of a phase present in a composite is a complex problem involving both preparation of representative surfaces and appropriate methods of evaluation. A number of experimental results are provided. Where smearing of surfaces is not a problem, point counting evaluation on sawn surfaces is shown to provide reliable results.     

High-resolution field desorption/ionization fourier transform ion cyclotron resonance mass analysis of nonpolar molecules

We report the first field desorption ionization broadband high-resolution (m/Deltam(50%) approximately 65 000) mass spectra. We have interfaced a field ionization/field desorption source to a home-built 9.4-T FT-ICR mass spectrometer. The instrumental configuration employs convenient sample introduction (in-source liquid injection) and external ion accumulation. We demonstrate the utility of this configuration by generating high-resolution positive-ion mass spectra of C(60) and a midboiling crude oil distillate. The latter contains species not accessible by common soft-ionization methods, for example, low-voltage electron ionization, electrospray ionization, and matrix-assisted laser desorption/ionization. The present work demonstrates significant advantages of FI/FD FT-ICR MS for analysis of nonpolar molecules in complex mixtures.     

Evolving controllers for a homogeneous system of physical robots: structured cooperation with minimal sensors

We report on recent work in which we employed artificial evolution to design neural network controllers for small, homogeneous teams of mobile autonomous robots. The robots were evolved to perform a formation-movement task from random starting positions, equipped only with infrared sensors. The dual constraints of homogeneity and minimal sensors make this a non-trivial task. We describe the behaviour of a successful system in which robots adopt and maintain functionally distinct roles in order to achieve the task. We believe this to be the first example of the use of artificial evolution to design coordinated, cooperative behaviour for real robots.