Truis Smith-Palmer

Separation methods applicable to urinary creatine and creatinine

Urinary creatinine has been analyzed for many years as an indicator of glomerular filtration rate. More recently, interest in studying the uptake of creatine as a result of creatine supplementation, a practice increasingly common among bodybuilders and athletes, has lead to a need to measure urinary creatine concentrations. Creatine levels are of the same order of magnitude as creatinine levels when subjects have recently ingested creatine, while somewhat elevated urinary creatine concentrations in non-supplementing subjects can be an indication of a degenerative disease of the muscle. Urinary creatine and creatinine can be analyzed by HPLC using a variety of columns. Detection methods include absorption, fluorescence after post-column derivatization, and mass spectrometry, and some methods have been automated. Capillary zone electrophoresis and micellar electrokinetic capillary chromatography have also been used to analyze urinary creatine and creatinine. Creatine and creatinine have also been analyzed in serum and tissue using HPLC and CE, and many of these separations could also be applicable to urinary analysis.

Confocal Raman microspectroscopy as a tool for studying the chemical heterogeneities of biofilms in situ

Aims:  To investigate the use of confocal Raman microspectroscopy (CRM) for the analysis of the structure, composition and development of fully hydrated biofilms.

Analysis of creatine and creatinine in urine by capillary electrophoresis

Creatine is found in the urine of subjects ingesting creatine monohydrate as an ergogenic aid. Creatinine, the catabolic breakdown product of creatine, is a major constituent of normal urine. It is of interest to follow the excretion of creatine and creatinine in urine as a function of time after creatine ingestion. In this study, creatine and creatinine were analyzed in urine by capillary electrophoresis. The optimization of the method was discussed, with the best results being obtained using a 30 mM phosphate-150 mM sodium dodecyl sulfate buffer at pH 6, with the detector set at 214 nm and an applied voltage of 15 kV across a 45 cm capillary. Verification of the method was provided by HPLC analysis and spiking. The application of the method was demonstrated by analysis of creatine and creatinine in urine samples collected in a 24-h period following creatine ingestion.

MICELLE FORMATION, RELAXATION TIME, AND THREE-PHASE COEXISTENCE IN A MICROEMULSION MODEL

Our Larson‐type microemulsion model for surfactant chains in oil–water solvents leads to long relaxation times as well as, for essential modifications, to a stable peak in the chain‐cluster size distribution. Transfer energies for surfactant chains moving to the oil–water interface, and characteristic micelle concentrations (CMC) as a function of chain length are compared with experiment.

The effects of cationic polymers on flocculation of a coal thickener feed in washery water as a function of pH

The flocculation of a thickener feed using three cationic polyacrylamide copolymers of high molar mass and different charge densities was studied at three pHs in washery water. The binding capacities were very dependent on pH but only slightly dependent on the polymeric charge density. The reverse was true for the settling rates. At pH 7, all three polymers were equally effective at clarifying the suspensions, but there were marked differences at pH 4 and 9. For the polymers of highest charge density, reducing the pH increased their effectiveness; for the polymer of lower charge density, changing the pH had little effect on the residual turbidity.

An FTIR study of Pseudomonas aeruginosa PAO1 biofilm development: interpretation of ATR–FTIR data in the 1500–1180 cm −1 region

Infrared spectra of Pseudomonas aeruginosa PAO1 biofilms grown on 40° ZnSe and 40° AMTIR (amorphous material transmitting infrared radiation, Ge 33 As 12 Se 55 ) internal reflection elements (IRE) at 26 °C in a flow cell were collected. The depth of penetration of the evanescent wave was sufficient to identify four biofilm stages during the experiment: (1) cell/substratum attachment, (2) lag phase, (3) later-stage growth, and (4) restructuring (e.g. rearrangement, detachment or “erosion”). Our experimental results provide the first detection via a non-perturbative technique of an excess of protein in the neighbourhood of the surface. Our mathematical analysis applied to the data supports the conclusion that our observations cannot be completely accounted for by the changing characteristics of bacterial proteins but, rather, shows that an accumulation of excess protein near the attachment surface is taking place. On the assumption that biofilm cells are approximately of the same size as those of the planktonic culture, this suggests the presence of extracellular proteins. Our data do not support the presence of extracellular nucleic acids near the attachment surface in these biofilms. This conclusion is based on our observation that, during the initial 20 h of development (stage 2 and the beginning of stage 3), biofilms had a higher proportion of protein to nucleic acid than in the latter part of stage 3 and in stage 4. In the restructuring phase this ratio became equal to the ratio determined for planktonic cultures. The decrease of biomass during stage 4 is inconsistent with the physical removal or sloughing-off of cellular aggregates from biofilms within a few micrometres of the substrate surface but, instead, supports a model of gradual cell migration away from it. During this cell migration there is also a gradual loss of extracellular protein. Alternatively, therefore, the restructuring may involve cell lysis and the observed loss of biomass may be due to soluble macromolecules being removed from the neighbourhood of the surface.

An FTIR study of Pseudomonas aeruginosa PAO1 biofilm growth and dispersion. An improved ATR method for studying biofilms: the C–H stretch spectral region

Pseudomonas aeruginosa PAO1 was grown on 40° ZnSe and 40° AMTIR® ( A morphous M aterial T ransmitting I nfrared R adiation, Ge 33 As 12 Se 55 ) internal reflection elements in a thermostatted flow cell. Information about the chemistry of the biofilm development was obtained using Fourier transform infrared spectroscopy. The weakly absorbing C–H stretching region of the infrared spectrum was measured for the first time and revealed qualitative and quantitative changes not evident in the amide region studied by previous investigators. There is a chemical difference between the early growth period and subsequent development of the biofilm.

Mn2+ EPR study of phase transitions occurring in single crystals of [N(CH3)4]2ZnCl4, [N(CH3)4]2ZnBr4, [N(CH3)4]2CoBr4, [N(C2H5)4]2ZnCl4, [N(C2 H5)4]2ZnBr4, [N(C2H5)4]2CoBr4 and [N(C2H5)4]2MnBr4

Abstract X-band (∼9.4 GHz) EPR measurements on Mn2+-doped single crystals of the tetra-alkylammonium metal tetra-halide compounds, [N(CH3)4]2ZnCl4, [N(CH3)4]2ZnBr4, [N(CH3)4]2CoBr4, [N(C2H5)4]2-ZnBr4, [N(C2H5)4]2ZnBr4, [N(CH3)4]2CoBr4 and [N(C2H5)4]2MnBr4 have been performed between 77 and 298 K for the first time. The Mn2+ spin-Hamiltonian parameters have been estimated in [N(C2H5)4]2ZnCl4, from the data recorded at 120 K, using a least-squares fitting technique. From the variation in the features of EPR spectra with temperature, the phase-transition temperatures, as well as the nature — first or second order — of the phase transitions, have been determined in these compounds.

Attenuated Total Reflectance Spectra of Colloidal and Particulate Silica Samples in Aqueous Media

We have measured and compared ATR/FT-IR spectra of aqueous dispersions of colloidal silica, and aqueous suspensions of particulate silica, over ranges of bulk concentrations using CIRCLE® and Contact Sampler™ cells. Procedures are described for quantitative analyses of each silica type. Detection limits are approximately 0.001% for the particulate species. The spectra of particulates are distorted by refractive-index effects to low frequency of the main analytical bands around 1090 cm-1, but the distortions are proportional to concentration and do not interfere with the precision of analyses. We recommend either ATR cell, but the Contact Sampler™ is more convenient.

A Confocal Raman Microscopy Study of the Distribution of a Carotene-Containing Yeast in a Living Pseudomonas Aeruginosa Biofilm

The distribution of a carotene-containing yeast (CCY) in a biofilm formed by a small colony variant (SCV) of Pseudomonas aeruginosa PA01 was followed by confocal Raman microspectroscopy (CRM). SCV PA01 and CCY cells were distinguished by their spectral signatures, and the distribution of the overall biomass was monitored by the C–H bending or stretching signal. The distributions of total biomass, PA01, and CCY cells were compared at various times and positions within the biofilm. The distribution of the CCY was very heterogeneous. It was found in the water channels as well as in regions within biofilm colonies. Many of the yeast cells observed within the biofilm colonies under conditions of low or stopped flow were removed when medium was flowing, suggesting that the yeast was not held in the matrix as tightly as were the bacteria.