Add time:08/17/2019         Source:sciencedirect.com

1.1. 2-fluoroputrescine (cas 104613-90-3) has a high affinity for spermidine synthase (Km 12μ M) and obeys normal Michaelis-Menten kinetics.2.2. The only product of the spermidine synthase-catalysed aminopropylation of 2-fluoroputrescine is 6-fluorospermidine. Formation of the isomerie 7-fluorospermidine could not be detected.3.3. 2,2-Difluoputrescine has even a higher affinity for spermidine synthase than putrescine and 2-fluoroputrescine; however, at concentrations > 25 μM one observes inhibition of the aminopropylation reaction.4.4. Competition experiments between putrescine and 2,2-difluoroputrescine revealed mixed type inhibition.5.5. HTC cells in suspension culture incorporated only small amounts of 2-fluoroputrescine, and even less in the case of 2,2-difluoroputrescine, if they were exposed to 10μM concentrations of these diamines for up to 24 hr. However, in the presence of 0.5mM DFMO, a concentration not sufficient to decrease cell growth significantly, but sufficient to decrease cellular putrescine and spermidine concentrations, the uptake of the chain-fluorinated diamines and their transformation into the fluorinated polyamine analogues was dramatically enhanced. In comparison with the difluoro analogues the accumulation rate of monofluoropolyamines was greater by a factor of about two.6.6. 6-Fluorospermidine and 6-fluorospermine could be detected in significant quantities in nearly all tissues of mice 48 hr after a single dose (500 mg/kg) of 2-fluoroputrescine. In an analogous experiment with 2,2-difluoroputreseine, the formation of chain-fluorinated polyamines was considerably smaller.7.7. Pretreatment of Lewis lung carcinoma bearing C57BL mice with α-difluoromethylornithine enhanced the incorporation of 2-fluoroputrescine into all organs, except the brain. Tumor and small intestines showed by far the highest accumulation of 6-fluoropolyamines.8.8. Under identical experimental conditions the accumulation of chain-fluorinated polyamines in tumor tissue was more than twice as high with 2-fluoroputrescine as precursor than with the same dose of 2,2-difluoroputrescine. In normal tissues the difference between the uptake of 2-fluoroputrescine and 2,2-difluoroputrescine was usually even greater.9.9. From the fact that the accumulation of 6-fluoropolyamines is less selective in tumors than that of 6,6-difluoropolyamines, and from the lower detection sensitivity due to its lower fluorine content, we conclude that 2,2-difluoroputrescine is more advantageous as a tumor marker than 2-fluoroputrescine for detection with 19F-NMR spectroscopy. However, monofluoropolyamines may have advantages in 19F-NMR-metabolic studies, because of their closer similarity with the natural polyamines.

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