1,721,000 research outputs found
Nitrido technetium-99m core in radiopharmaceutical applications: Four decades of research
Full text linkThe knowledge on element 43 (Tc) of the periodic table, built over the years through the contributions given by the close relationship between chemistry and nuclear medicine, allowed the development of new and increasingly effective radiopharmaceuticals useful both as perfusion and target specific imaging agents for SPECT (single photon emission tomography). Among the manifold Tc-compounds, Tc(V) nitrido complexes played a relevant role in the search for new technetium-99m radiopharmaceuticals, providing effcient labeling procedures that can be conveniently exploited for the design and synthesis of agents, also incorporating small organic molecules or peptides having defined structural features. With this work, we present an overview of four decades of research on the chemistry and on the nuclear medicine applications of Tc(V) nitrido complexes
Enzymatic methods for the site-specific radiolabeling of targeting proteins
Full text linkSite-specific conjugation of proteins is currently required to produce homogenous derivatives for medicine applications. Proteins derivatized at specific positions of the polypeptide chain can actually show higher stability, superior pharmacokinetics, and activity in vivo, as compared with conjugates modified at heterogeneous sites. Moreover, they can be better characterized regarding the composition of the derivatization sites as well as the conformational and activity properties. To this aim, several site-specific derivatization approaches have been developed. Among these, enzymes are powerful tools that efficiently allow the generation of homogenous protein–drug conjugates under physiological conditions, thus preserving their native structure and activity. This review will summarize the progress made over the last decade on the use of enzymatic-based methodologies for the production of site-specific labeled immunoconjugates of interest for nuclear medicine. Enzymes used in this field, including microbial transglutaminase, sortase, galactosyltransferase, and lipoic acid ligase, will be overviewed and their recent applications in the radiopharmaceutical field will be described. Since nuclear medicine can benefit greatly from the production of homogenous derivatives, we hope that this review will aid the use of enzymes for the development of better radio-conjugates for diagnostic and therapeutic purposes
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Symmetric bis-substituted and asymmetric mono-substituted nitridotechnetium complexes with heterofunctionalized phosphinothiolate ligands
No full textThe mixed bidentate ligand 2-(dicyclohexylphosphino)-ethanethiol (HL) reacts with labile nitrido-Tc precursors to afford a rare example of an asymmetric monosubstituted species [TcN(L)Cl(PPh3)], 1, along with the symmetric bis-substituted complex [TcN(L)2], 2. The latter compound, as assessed by TLC and HPLC chromatography, was found to possess the same molecular structure as the agent produced at the 'non carrier added' level utilizing the 99mTc nuclear isomer
Facile preparation of Re-188 radiopharmaceuticals from generator-produced Re-188 perrhenate.
No full text--
A bis(thiosemicarbazone) bifunctional chelating agent for nitrido-technetium-99m and copper-64 based radiopharmaceuticals
No full textSynthesis and biological evaluation of new [Tc(N)(PS)]-based mixed-ligand compounds useful in the design of target-specific radiopharmaceuticals: the 2-methoxyphenylpiperazine dithiocarbamate derivatives as an example
No full textThis study presents the first application of a general procedure based on the use of the [Tc(N)Cl(PS)(PPh3)] species (PS is an alkyl phosphinothiolate ligand) for the prepn. of Tc(N) target-specific compds. [Tc(N)Cl(PS)(PPh3)] selectively reacts with an appropriate dithiocarbamate ligand (S-Y) to give [Tc(N)(PS)(S-Y)] compds. 1-(2-Methoxyphenyl)piperazine, which displays a potent and specific affinity for 5HT1A receptors, was selected as a functional group and conjugated to the dithiocarbamate unit through different spacers (Ln). [99mTc(N)(PS)(Ln)] complexes were prepd. in high yield (more than 90%). The chem. identity of 99mTc complexes was detd. by HPLC comparison with the corresponding 99gTc complexes. All complexes are inert toward trans-chelation with an excess of glutathione and cysteine. No notable biotransformation of the native compd. into different species by the in vitro action of the serum and liver enzymes was shown. Nanomolar affinity for the 5HT1A receptor was obtained for [99mTc(N)(PSiso)L3] (IC50 = 1.5 nM); a redn. of the affinity was obsd. for the other complexes as a function of the shortening of the alkyl chain interposed between the dithiocarbamate and the pharmacophore. Negligible brain uptake was found from in vivo distribution data of [99mTc(N)(PSiso)L3]. The key finding of this study is that the complexes maintained good affinity and selectivity for 5HT1A receptors, and the IC50 value for [99gTc(N)(PSiso)L3] being comparable to the IC50 value found for WAY 100635. This result confirmed the possibility of prepg. [99mTc(N)(PS)]-based target-specific compds. without affecting the affinity and selectivity of the bioactive mols. for the corresponding receptors
Oxo-rhenium(V) mixed-ligand complexes with bidentate functionalized phosphines and tridentate Schiff base ligands
No full textA series of monooxo-rhenium(V) mixed-ligand complexes containing bidentate functionalized phosphines and tridentate Schiff base (SB) ligands have been synthesized via ligand-exchange reactions starting from labile Re(V) precursors. A convenient route of synthesis is provided by the isolation of intermediate species such as [Re(O)(Ln)Cl3]- (1-3), (Ln = bidentate phosphino-phenolato or phosphino-carboxylato ligands). Subsequent addition of the relevant SB affords neutral mixed-ligand complexes of general formula [Re(O)(Ln)(SBm)] (1-3m). By reversing the addition of the two ligands, i.e. SB first followed by functionalized phosphine, the resulting mixed-ligand species do not change formulation. Conventional spectroscopic techniques and the single-crystal X-ray structure determination of the two representative compounds ([Re(O)(L1)(SBa)] (1a) and [Re(O)(L1)(SBb)] (1b)) reveal a distorted octahedral geometry around the rhenium center, with the phosphino-phenolato oxygen located trans to the oxo group and the equatorial sites filled by the SB donors and the phosphine phosphorus. It is worth noting that technetium chemistry works quite differently under the same reaction conditions. In fact, no intermediate species of the type [Tc(O)(Ln)Cl3]- can be isolated with [Tc(O)Cl(L1)2] and reduced [Tc(Ln)3] being the major compound
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
- …
