Browsing by Author "Tsai, Jia-Chun"

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Iron(III) Bound by Hydrosulfide Anion Ligands: NO-Promoted Stabilization of the [Fe-III-SH] Motif
(2014-07-02)
Tsou, Chih-Chin
;
Chiu, Wei-Chun
;
Ke, Chun-Hung
;
Tsai, Jia-Chun
;
Wang, Yun-Ming
Spontaneous transformation of the thermally stable [HS](-)bound {Fe(NO)(2)}(9) dinitrosyl iron complex (DNIC) [(HS)(2)Fe(NO)(2)](-) (1) into [(NO)(2)Fe(mu-S)](2)(2-) (Roussin's red salt (RRS)) along with release of H2S, probed by NBD-SCN (NBD = nitrobenzofurazan), was observed when DNIC 1 was dissolved in water at ambient temperature. The reversible transformation of RRS into DNIC 1 (RRS -> DNIC 1) in the presence of H2S was demonstrated. In contrast, the thermally unstable hydrosulfide-containing mononitrosyl iron complex (MNIC) [(HS)(3)Fe-III(NO)](-) (3) and [Fe-III(SH)(4)](-) (5) in THF/DMF spontaneously dimerized into the first structurally characterized Fe-III-hydrosulfide complexes [(NO)(SH)Fe(mu-S)](2)(2-) (4) with two {Fe(NO)}(7) motifs antiferromagnetically coupled and [(SH)(2)Fe(mu-S)](2)(2-) (6) resulting from two Fe-III (S = 5/2) centers antiferromagnetically coupled to yield an S = 0 ground state with thermal occupancy of higher spin states, respectively. That is, the greater the number of NO ligands bound to [2Fe2S], the larger the antiferromagnetic coupling constant. On the basis of DFT computation and the experimental (and calculated) reduction potential (E-1/2) of complexes 1, 3, and 5, the NO-coordinate ligand(s) of complexes 1 and 3 serves as the stronger electron-donating ligand, compared to thiolate, to reduce the effective nuclear charge (Z(eff)) of the iron center and prevent DNIC 1 from dimerization in an organic solvent (MeCN).
Iron(III) Bound by Hydrosulfide Anion Ligands: NO-Promoted Stabilization of the [Fe-III-SH] Motif
(2014-07-02)
Tsou, Chih-Chin
;
Chiu, Wei-Chun
;
Ke, Chun-Hung
;
Tsai, Jia-Chun
;
Wang, Yun-Ming
Spontaneous transformation of the thermally stable [HS](-)bound {Fe(NO)(2)}(9) dinitrosyl iron complex (DNIC) [(HS)(2)Fe(NO)(2)](-) (1) into [(NO)(2)Fe(mu-S)](2)(2-) (Roussin\'s red salt (RRS)) along with release of H2S, probed by NBD-SCN (NBD = nitrobenzofurazan), was observed when DNIC 1 was dissolved in water at ambient temperature. The reversible transformation of RRS into DNIC 1 (RRS -> DNIC 1) in the presence of H2S was demonstrated. In contrast, the thermally unstable hydrosulfide-containing mononitrosyl iron complex (MNIC) [(HS)(3)Fe-III(NO)](-) (3) and [Fe-III(SH)(4)](-) (5) in THF/DMF spontaneously dimerized into the first structurally characterized Fe-III-hydrosulfide complexes [(NO)(SH)Fe(mu-S)](2)(2-) (4) with two {Fe(NO)}(7) motifs antiferromagnetically coupled and [(SH)(2)Fe(mu-S)](2)(2-) (6) resulting from two Fe-III (S = 5/2) centers antiferromagnetically coupled to yield an S = 0 ground state with thermal occupancy of higher spin states, respectively. That is, the greater the number of NO ligands bound to [2Fe2S], the larger the antiferromagnetic coupling constant. On the basis of DFT computation and the experimental (and calculated) reduction potential (E-1/2) of complexes 1, 3, and 5, the NO-coordinate ligand(s) of complexes 1 and 3 serves as the stronger electron-donating ligand, compared to thiolate, to reduce the effective nuclear charge (Z(eff)) of the iron center and prevent DNIC 1 from dimerization in an organic solvent (MeCN).
Sensitivity evaluation of NBD-SCN towards cysteine/homocysteine and its bioimaging applications
(2014-06-15)
Chen, Yen-Hao
;
Tsai, Jia-Chun
;
Cheng, Tsan-Hwang
;
Yuan, Shyng-Shiou
;
Wang, Yun-Ming
A push-pull fluorogenic reagent, NBD-SCN, was applied for specific detection of cysteine (Cys) and homocysteine (Hcy). Replacing thiocyanato group with Cys/Hcy increased the push-pull characteristic of the probe and resulted in emission of fluorescence. The fluorescent response of the probe toward Cys/Hcy was significantly higher than toward glutathione and other amino acids. The probe showed a 470-and 745-fold fluorescence enhancement at 550 nm and detection limit of 2.99 and 1.43 nM for Cys and Hcy, respectively. Time-dependent fluorescence assays showed that the fluorescence intensity reached a plateau within 20 s after addition of Cys and within 10 min after addition of Hcy. Furthermore, the fluorescence images of Cys/Hcy in Raw 264.7 cells were obtained after adding this probe to the cells. These results indicate that NBD-SCN not only possesses good selectivity and sensitivity for Cys/Hcy but also can penetrate cells for Cys/Hcy bioimaging. (C) 2014 Elsevier B.V. All rights reserved.