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- Cheeseman, J. D., et al.
(author)
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Structure of an aryl esterase from Pseudomonas fluorescens
- 2004
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In: Acta Crystallographica Section D. - 0907-4449 .- 1399-0047. ; 60:7, s. 1237-1243
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Journal article (peer-reviewed)abstract
- The structure of PFE, an aryl esterase from Pseudomonas fluorescens, has been solved to a resolution of 1.8 Å by X-ray diffraction and shows a characteristic α/β-hydrolase fold. In addition to catalyzing the hydrolysis of esters in vitro, PFE also shows low bromoperoxidase activity. PFE shows highest structural similarity, including the active-site environment, to a family of non-heme bacterial haloperoxidases, with an r.m.s. deviation in 271 Cα atoms between PFE and its five closest structural neighbors averaging 0.8 Å. PFE has far less similarity (r.m.s. deviation in 218 Cα atoms of 5.0 Å) to P. fluorescens carboxyl esterase. PFE favors activated esters with small acyl groups, such as phenyl acetate. The X-ray structure of PFE reveals a significantly occluded active site. In addition, several residues, including Trp28 and Met95, limit the size of the acyl-binding pocket, explaining its preference for small acyl groups.
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| 2. |
- Stangenberg, Friedhelm, et al.
(author)
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Quality assessments of recycled plastics by spectroscopy and chromatography
- 2004
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In: Chromatographia. - 0009-5893 .- 1612-1112. ; 59:02-jan, s. 101-106
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Journal article (peer-reviewed)abstract
- Quality assessments will be important for improved use of recycled polymeric materials. Ongoing preparation of new standards in the area of recycled polymers needs an overview of which properties and thus which polymer ckaracterisation methods that will be important for that purpose. We suggest three polymeric properties as important for this work; these are degree of mixing (composition), degree of degradation and number and amount of low molecular weight compounds (e.g. degradation products, additives, flavour compounds). DSC showed increased degradation as multi modality for LDPE materials obtained from three different sites in a recycling plant. IR demonstrated that the carbonyl index increased during the various steps going from collected material to new product. GC chromatograms obtained for collected film Rakes, processed granules and ready-made bags were quite complex with a series of hydrocarbons among other compounds. The recycling process seems, however, to remove some of the low molecular weight compounds found in the incoming dirty material.
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