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ULTIMO FASCICOLOTHE QUARTERLY JOURNAL OF NUCLEAR MEDICINE AND MOLECULAR IMAGING

Rivista di Medicina Nucleare e Imaging Molecolare


A Journal on Nuclear Medicine and Molecular Imaging
Affiliated to the Society of Radiopharmaceutical Sciences and to the International Research Group of Immunoscintigraphy
Indexed/Abstracted in: Current Contents/Clinical Medicine, EMBASE, PubMed/MEDLINE, Science Citation Index (SciSearch), Scopus
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The Quarterly Journal of Nuclear Medicine 1998 Dicembre;42(4):280-93

MOLECULAR MANIPULATION AND PHARMACOKINETICS 

The influ­ence of ster­eo­i­som­er­ism on the phar­ma­cok­i­net­ics of Tc radio­phar­ma­ceu­ti­cals

Hansen L., Marzilli L. G.*, Taylor A.

From the Department of Radiology *Department of Chemistry Emory University School of Medicine, Atlanta, GA, USA

The influ­ence of ster­eo­i­som­er­ism on the phar­ma­cok­i­net­ics of Tc ­mono-oxo com­plex­es is ­reviewed. Tc(V) ­mono-oxo com­plex­es ­formed ­with N/S ­ligands ­have ­four ­donor ­groups ­from the ­ligands in an equa­to­ri­al ­plane; the oxo ­ligand coor­di­nates in an ­axial posi­tion. Stereoisomerism in Tc (V) ­mono-oxo com­plex­es can be cen­tered with­in the ­ligand (car­bon ­atom in the che­late ­ring or ligat­ing nitro­gen of ­amine ­donors) or at the Tc. The met­al cen­ter ­becomes chi­ral ­when an equa­to­ri­al ­ligand has a ­head and a ­tail (i.e., the two ­ends of the ­ligand dif­fer). All ­types of ster­eo­cen­ters can pro­duce sig­nif­i­cant­ly dif­fer­ent phar­ma­cok­i­net­ic pro­files for indi­vid­u­al iso­mers. Thus, bio­log­i­cal eval­u­a­tion of sep­ar­at­ed ster­eo­i­som­ers is nec­es­sary to iden­ti­fy the opti­mal ster­eo­chem­i­cal con­fig­u­ra­tion, par­tic­u­lar­ly for radio­phar­ma­ceu­ti­cals tar­get­ed to recep­tor mole­cules ­with low spec­i­fic­ity. Because of inter­spe­cies vari­a­tion, ­there is ulti­mate­ly no sub­sti­tute for ­human test­ing. Although it is pos­sible ­that the ­increase in non­spe­cif­ic bind­ing of ­agents incor­po­rat­ing L- vs D-ami­no ­acids may ­more ­than off­set any ­increased recep­tor bind­ing, ­much ­more infor­ma­tion is need­ed. Stereochemical fac­tors can ­also ­lead to unpre­dict­able dif­fer­enc­es in coor­di­na­tion geom­e­try and ther­mo­dy­nam­ic pref­er­ence of a sin­gle iso­mer; ­thus chem­i­cal char­ac­ter­iza­tion of ster­eo­i­som­ers con­tin­ues to be an impor­tant com­po­nent of radio­phar­ma­ceu­ti­cal devel­op­ment.

lingua: Inglese


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