Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:O14944 (EPR)
 13,097 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Reconstitutively active and inactive succinate dehydrogenase have been investigated by low temperature magnetic circular dichroism (MCD) and EPR spectroscopy and room temperature CD and absorption spectroscopy. Reconstitutively active succinate dehydrogenase is found to contain three spectroscopically distinct Fe-S clusters: S1, S2, and S3. In agreement with previous studies, MCD and CD spectroscopy confirm that center S1 is a succinate-reducible [2Fe-2S]2+,1+ center. The MCD characteristics of center S2 identify it as a dithionite-reducible [4Fe-4S]2+,1+ similar to those in bacterial ferredoxins. EPR power saturation studies and the weakness of the EPR signal from reduced S2 indicate that there is a weak magnetic interaction between centers S1 and S2 in their paramagnetic, S = 1/2, reduced states. Center S3 is identified both by the form of the MCD spectrum and the characteristic magnetization behavior as a reduced [3Fe-xS] center in both succinate- and dithionite-reduced reconstitutively active succinate dehydrogenase. Arguments are presented in favor of centers S2 and S3 being separate centers rather than interconversion products of the same cluster. Reconstitutively inactive succinate dehydrogenase is found to be deficient in center S3. These results resolve many of the controversies concerning the Fe-S cluster content of succinate dehydrogenase and reconcile published EPR data with analytical and core extrusion studies. Moreover, they indicate that center S3 is a necessary requirement for reconstitutive activity and suggest that it is able to sustain ubiquinone reductase activity as a [3Fe-xS] center.
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PMID:Magnetic circular dichroism studies of succinate dehydrogenase. Evidence for [2Fe-2S], [3Fe-xS], and [4Fe-4S] centers in reconstitutively active enzyme. 298 54

The affinity of copper(ii) porphyrins for pyridine ligands is extremely weak, but oligo-pyridine templates can be used to direct the synthesis of Cu-containing cyclic porphyrin oligomers when they also have Zn centers. We report the synthesis of two heterometallated nanorings: a six-porphyrin ring prepared from a Zn/Cu/Zn linear trimer and a ten-porphyrin ring prepared from a Zn/Zn/Cu/Zn/Zn pentamer. Both these macrocycles have copper porphyrins at two specific positions across the diameter of the ring and zinc at other sites. The presence of a paramagnetic metal results in broadening of the 1H NMR spectra and reduces the relaxation time constants (T1 and T2). The changes in T1 provide quantitative information on the distance of each proton from the copper atom. The Zn/Zn/Cu/Zn/Zn linear porphyrin pentamer binds strongly to a penta-pyridyl template, despite the weakness of the Cu-N interaction, because of the chelate cooperativity of the neighboring Zn-N coordination. The stabilities of a family of four linear porphyrin pentamer complexes were determined by UV-vis-NIR titration and analyzed using a chemical double-mutant cycle. The results show that the free energy of interaction of a copper center to axial pyridine ligands is -6.2 kJ mol-1 when the entropy cost of bringing together the two molecules has already been paid by pyridine-zinc interactions. The development of template-directed approaches to the synthesis of nanorings with combinations of different metals at specific positions around the ring opens up many possibilities for controlling the photophysical behavior of these supramolecular systems and for probing their conformations by EPR.
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PMID:Nanorings with copper(ii) and zinc(ii) centers: forcing copper porphyrins to bind axial ligands in heterometallated oligomers. 2845 Nov 30

Calcium phosphate (CaP) nanoparticles have been considered as a non-viral gene delivery vehicle, but the weakness of inconsistent and low transfection efficiencies is limited to its progress. In order to overcome these weaknesses and to improve the consistency and efficiency of CaP nanoparticles, a pH-sensitive core-shell system mPEG-Pam/CaP/HMGB1/pDNA hybrid nanoparticle was prepared. The PEGylated pamidronate (mPEG-Pam) segment forms a hydrophilic outer shell for enhancing the stability of nanoparticles and HMGB1 was used as a nucleus locating signal (NLS) to improve the efficiency of nucleus importation and gene expression. The formed hybrid nanoparticles presented small particle size and desired serum stability with the assistance of the mPEG-Pam outer layer. The results of RFP fluorescence intensity analysis in HepG2 cells showed that the hybrid nanoparticles exhibited higher transfection capability with the help of HMGB1 as compared to that of the nanoparticles without the HMGB1. More importantly, after intravenous injection in tumor-bearing S180 nude mice, the hybrid nanoparticles specifically accumulated into the tumor regions by EPR effect, leading to efficient gene expression and anti-tumor effects in vivo. We concluded that the hybrid nanoparticles possessed potential as a safe and effective pDNA delivery system.
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PMID:Self-assembled CaP-based hybrid nanoparticles to enhance gene transfection efficiency in vitro and in vivo: beneficial utilization of PEGylated bisphosphate and nucleus locating signal. 3225 43