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Production and Transport of Gaseous (18)F-Synthons: (18)F-Acyl Fluorides.

ABSTRACT: Fluorine-18 ((18)F, T 1/2=109.7 min) is a positron-emitting isotope that has found extensive application as a radiolabel for positron emission tomography (PET). Although gaseous (11)C-CO2 and (11)C-CH4 are practically transported from cyclotron to radiochemistry processes, (18)F-fluoride is routinely transported in aqueous solution because it is commonly produced by proton irradiation of (18)O-enriched water. In most cases, subsequent dry-down steps are necessary to prepare reactive (18)F-fluoride for radiofluorination. In this work, a simple module was designed to generate gaseous (18)F-acyl fluorides from aqueous (18)F-fluoride solution by solid phase (18)F-radiofluorination of acyl anhydride. The gaseous (18)F-acyl fluorides were purified through a column containing Porapak Q/Na2SO4, resulting in high yields (>86%), purities (>99%) and specific activities (>1200 GBq/?mol). Prototypic (18)F-acetyl fluoride ((18)F-AcF) was readily transported through 15 m of 0.8 mm ID polypropylene tubing with low (0.64 ± 0.12 %) adsorption to the tubing. Following dissolution of (18)F-AcF in solvent containing base, highly reactive (18)F-flouride was generated immediately and used directly for (18)F-labeling reactions. These data indicate that (18)F-acyl fluorides represent a new paradigm for preparation and transport of anhydrous, reactive (18)F-fluoride for radiofluorinations.

SUBMITTER: Jiang H

PROVIDER: S-EPMC4797647 | biostudies-literature | 2015 Dec

REPOSITORIES: biostudies-literature

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Production and Transport of Gaseous 18F-Synthons: 18F-Acyl Fluorides.

Jiang Huailei H DiMagno Stephen G SG DeGrado Timothy R TR

Journal of fluorine chemistry 20151003

Fluorine-18 (18F, T 1/2=109.7 min) is a positron-emitting isotope that has found extensive application as a radiolabel for positron emission tomography (PET). Although gaseous 11C-CO2 and 11C-CH4 are practically transported from cyclotron to radiochemistry processes, 18F-fluoride is routinely transported in aqueous solution because it is commonly produced by proton irradiation of 18O-enriched water. In most c ...[more]

PMID: 27003949

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Project description:BackgroundAcyl-(acyl carrier protein (ACP)) reductase (AAR) is a key enzyme for hydrocarbon biosynthesis in cyanobacteria, reducing fatty acyl-ACPs to aldehydes, which are then converted into hydrocarbons by aldehyde-deformylating oxygenase (ADO). Previously, we compared AARs from various cyanobacteria and found that hydrocarbon yield in Escherichia coli coexpressing AAR and ADO was highest for AAR from Synechococcus elongatus PCC 7942 (7942AAR), which has high substrate affinity for 18-carbon fatty acyl-ACP, resulting in production of mainly heptadecene. In contrast, the hydrocarbon yield was lowest for AAR from Synechococcus sp. PCC 7336 (7336AAR), which has a high specificity for 16-carbon substrates, leading to production of mainly pentadecane. However, even the most productive AAR (7942AAR) still showed low activity; thus, residues within AAR that are nonconserved, but may still be important in hydrocarbon production need to be identified to engineer enzymes with improved hydrocarbon yields. Moreover, AAR mutants that favor shorter alkane production will be useful for producing diesel fuels with decreased freezing temperatures. Here, we aimed to identify such residues and design a highly productive and specific enzyme for hydrocarbon biosynthesis in E. coli.ResultsWe introduced single amino acid substitutions into the least productive AAR (7336AAR) to make its amino acid sequence similar to that of the most productive enzyme (7942AAR). From the analysis of 41 mutants, we identified 6 mutations that increased either the activity or amount of soluble AAR, leading to a hydrocarbon yield improvement in E. coli coexpressing ADO. Moreover, by combining these mutations, we successfully created 7336AAR mutants with ~ 70-fold increased hydrocarbon production, especially for pentadecane, when compared with that of wild-type 7336AAR. Strikingly, the hydrocarbon yield was higher in the multiple mutants of 7336AAR than in 7942AAR.ConclusionsWe successfully designed AAR mutants that, when coexpressed with ADO in E. coli, are more highly effective in hydrocarbon production, especially for pentadecane, than wild-type AARs. Our results provide a series of highly productive AARs with different substrate specificities, enabling the production of a variety of hydrocarbons in E. coli that may be used as biofuels.

Dataset Information

Production and Transport of Gaseous (18)F-Synthons: (18)F-Acyl Fluorides.

Publications

Production and Transport of Gaseous <sup>18</sup>F-Synthons: <sup>18</sup>F-Acyl Fluorides.

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