476 research outputs found
Widnes Sure Start user satisfaction survey
This report discusses levels of satisfaction with Sure Start Widnes, levels of knowledge of the existence of Sure Start Widnes, and how people access the services offered by Sure Start Widnes.Sure Start Widne
Education for What and for Whom: Challenges, Visions and Realities in the 21st Century, A Third World Perspective
Kinetic evaluation of human cloned coproporphyrinogen oxidase using a ring isomer of the natural substrate
Background: The enzyme coproporphyrinogen oxidase (copro\u27gen oxidase) converts coproporphyrinogen-Ill (GIII) to protoporphyrinogen-IX via an intermediary monovinyl porphyrinogen. The A ring isomer coproporphyrinogen-IV (C-IV) has previously been shown to be a substrate for copro\u27gen oxidase derived from avian erythrocytes. In contrast to the authentic substrate (GIII) where only a small amount of the monovinyl intermediate is detected, C-IV gives rise to a monovinyl intermediate that accumulates before being converted to an isomer of protoporphyrinogen-IX. No kinetic studies have been carried out using the purified human copro\u27gen oxidase to evaluate its ability to process both the authentic substrate as well as analogs. Material/Methods: Therefore, purified, cloned human copro\u27gen oxidase was incubated with GIII or C-IV at 37 degrees C with various substrate concentrations (from 0.005 mu M to 3.5 mu M). The Km (an indication of molecular recognition) and Kcat (turnover number) values were determined. Results: The Km value for total product formation was about the same with either C-III or C-IV indicating the same molecular recognition. However, the catalytic efficiency (Kcat/Km) of the enzyme for total product formation was not more than two fold higher using GIII relative to C-IV. Conclusions: Since the Km values are about the same for either substrate and the total Kcat/Km values are within two fold of each other, this could correlate with the increase of severity of porphyrias with monovinyl accumulation. The ability of the increased levels of C-IV to compete with the authentic substrate has important implications for clinical porphyrias
Construction and evaluation of exercises for quick silent reading responses for grade two.
Thesis (Ed.M.)--Boston Universit
FTIR Photoacoustic Spectroscopy Applied to the Curing and Aging of Composites
Fourier-transform infrared photoacoustic spectroscopy has been applied to carbonfiber composites to test whether bulk physical properties of the composites could be determined using the near-surface-sensitive photoacoustic approach. Both the cure levels of carbon fiber/cyanate ester composites and the interlaminar shear strengths of artificially aged carbon fiber/epoxy composites were successfully measured. Standard errors of cross validation were 3.46% cure for a sample set ranging from 8% to 95% cured and 1.60 MPa for aged samples with strengths ranging from 22 to 77 MPa
Use of Di- and Tripropionate substrate analogs to probe the active site of human recombinant coproporphyrinogen oxidase
Background: Defects in the enzyme coproporphyrinogen oxidase result in accumulation of porphyrins which may affect the severity of a subset of porphyrias. Thus evaluation of this enzyme for substrate selectivity is of value. Kinetic evaluations of recombinant human coproporphyrinogen oxidase have been undertaken using six di- and tripropionate analogs of the natural substrate coproporphyrinogen-III. These Substrate analogs were modified by having alkyl groups in place of one or both of the ring 13- or 17-propionate moieties. Material/Methods: Cloned human enzyme was incubated with analogs under apparent first order conditions and with various substrate concentrations. The kinetic values, K-m and V-max, were determined. Results: Relative to the authentic substrate, the K-m values for the 13-ethyl, dimethyl and diethyl porphyrinogens were very comparable whereas the K-m values were much higher using dipropyl and dibutyl porphyrinogen and much lower for the 17-ethyl analog. For the dipropionate analogs, the V-max values were an apparent function of the carbon length of the substituent. on the C and D rings, with longer carbon length severely reducing product formation by some 4-5 orders of magnitude. Also, the two isomeric tripropionates that were tested indicated that it was more detrimental to have an ethyl group at the 13-position for both binding and catalysis. Conclusions: This work extends our understanding of porphyrin ring substituent effects reported by Cooper et al. (2005). The substituents on both the C and D rings have significant effects on both the substrate binding and catalysis by this important enzyme
- …