Evolution of peptides that modulate the spectral qualities of bound, small-molecule fluorophores

BACKGROUND: Fluorophore dyes are used extensively in biomedical research to sensitively assay cellular constituents and physiology. We have created, as proof of principle, fluorophore dye binding peptides that could have applications in fluorescent dye-based approaches in vitro and in vivo. RESULTS: A panel of Texas red, Rhodamine red, Oregon green 514 and fluorescein binding peptides, termed here 'fluorettes', was selected via biopanning of a combinatorial library of 12-mer peptides fused to a minor coat pIII protein of the filamentous bacteriophage M13. The 'best' fluorette sequences from each of the groups were subjected to further mutagenesis, followed by a second biopanning to select a new generation of improved fluorettes. Phage were selected that had higher avidity for each fluorophore except Rhodamine red. Of these, peptides were characterized that could specifically and with high affinity bind at least one dye, Texas red, in solution. In addition, the binding of certain peptides to Texas red shifted the peak excitation and/or the emission spectra of the bound dye. CONCLUSIONS: Peptides in the context of phage display could readily be selected that could bind to small-molecule fluorophores. The affinities of selected mutant fluorettes could be increased by mutation and further selection. Only a subset of the free peptides could bind free dyes in solution, suggesting that phage context contributed to the selection and ability of certain peptidic regions to independently bind the dyes. Future screens might lead to the creation of other dye-binding peptides with novel characteristics or Texas red derivatives with cross-linking substituents might be designed to increase the utility of the system.     

Virus removal by iron coagulation-microfiltration

This study was undertaken to determine virus removal efficiency by iron coagulation followed by microfiltration (MF) in water treatment using the MS2 bacteriophage (25 nm diameter) as a tracer virus. Results from these bench-scale studies were used to propose a mechanism for virus removal by iron coagulation–MF. Ferric chloride was used as coagulant, and the dosages were 0, 2, 5, and 10 mg/L as Fe(III) with pH adjusted during mixing to 6.3, 7.3 and 8.3. In the absence of iron-coagulation and with less than 2 mg/L Fe, MF alone achieved less than a 0.5 log removal of MS2 virus. However, iron-coagulation pretreatment dramatically improved virus removal, especially in the 5–10 mg/L Fe dose range, ultimately achieving more than 4-log removal at pH 6.3 with 10-mg/L Fe dose. For the 5 and 10 mg/L Fe dosages, decreasing pH in the 8.3–6.3 range resulted in significantly greater virus removal. For 0 and 2 mg/L iron dosages, decreasing pH in the 8.3–6.3 range also improved virus removal, but to a lesser extent. The experimental data indicates negatively charged MS2 viruses first adsorbed onto the positively charged iron oxyhydroxide floc particles before being removed by MF. MS2 viruses were not inactivated in iron or aluminum coagulation as evidenced by the fact that their concentrations before and after coagulation, settling, and re-suspension of the coagulated sludge were not statistically different.     

Oxidation of SiCf/SiC‐HfB2 Composites under Laser Heating

Ceramic matrix composites with Sylramic^TM and CG Nicalon^TM SiC fibers and SiC‐HfB₂ matrices derived from a combination of polymer‐derived SiC ceramic and HfB₂ particulate slurries were prepared. The composites were tested for oxidation resistance by laser heating at 2 MW/m² to achieve temperatures near 1600°C. The oxidation resistance was compared between uncoated CG Nicalon^TM and BN‐coated Sylramic^TM fiber‐based composites. Oxidation resulted in precipitated nano‐sized HfO₂ independent of the fibers and fiber coatings.     

Impact of Multimedia-Based Instruction on Learning and Retention

Studies measuring and evaluating the impact of the same multimedia-based education on learners in universities and high schools are a relatively new phenomenon. This study provides a summary of the results from research on the effects of multimedia-based safety education conducted by the M. E. Rinker Sr. School of Building Construction at the University of Florida. The findings are presented along with their related statistical test results. The findings indicate multimedia-based, self-paced learning offers very distinct advantages over traditional, instructor-led classroom learning. Overall, both the high-school and university student groups involved in the study exhibited superior retention rates when learning from the multimedia-based materials. Higher scoring students in the classroom showed little difference in either media, while students who tended to score at the low end of the grading scale uniformly scored higher on multimedia-based materials. The reduced variation in student performance based on test scores in the CD-ROM instruction indicates the positive effects of multimedia-based instruction.     

The effect of drying on black tea quality

Drying is an important part of tea manufacture, where enzyme reactions in earlier phases are terminated by heat and moisture loss, and new compounds are produced by the action of heat. This work is an attempt to quantify the temperatures required to produce the desired changes without damage through exposure to excess heat. Experiments were carried out giving already‐dried tea further heat exposure, drying tea from wet dhool in a thin layer, and drying a larger sample in a batch fluidized bed dryer. Temperatures in the range of 60–140 °C were used. Effects were monitored by commercial tasters, thin layer chromatography, reverse phase HPLC and size exclusion HPLC. Exposure to at least 80 °C was found to be necessary for quality development. For periods of less than 1 min, tea particle temperatures of up to 120 °C may be tolerated, but, in general, temperatures of 110 °C and above may be considered deleterious. Inlet air temperatures may be in excess of these values, but only while drying rates are high. The stewing phenomenon, cited by several authors, could not be found when drying times of less than 15 min were used. © 2001 Society of Chemical Industry