Detailed equilibrium, spectroscopic and SOD activity studies are reported on nickel(II) complexes formed with the N-terminally free HHDLPCGVY-NH2 (NiSODHH) and HCDLPHGVY-NH2 (NiSODHC) peptides mimicking the nickel binding loop in NiSOD. In these model peptides, cysteine was incorporated in different positions in order to gain better insight into the role of the cysteine residues in NiSOD. The results are compared with those obtained with the wild-type fragment of NiSOD. The complex formation equilibria of nickel(II) with the two peptides exhibit different features. In the case of NiSODHH, the ligand field of the (NH2,NIm,NIm,S-) donor set is not strong enough to cause spin pairing and an octahedral paramagnetic complex is formed under physiological conditions. In contrast, NiSODHC forms square-planar diamagnetic complex with (NH2,N-,S-,NIm) donors which exhibits remarkable SOD activity. Our results unambiguously prove that the presence of cysteine in the secondary position of the peptide chain is crucial to establish the square-planar geometry in the reduced form of NiSOD, while the distant cysteine affects the redox properties of the Ni(II)/Ni(III) couple. Compared to the model systems, the Ni(II) complex with the wild-type fragment of NiSOD exhibits superior SOD activity. This confirms that both cysteinyl residues are essential in efficient degradation of superoxide ion. The enzyme mimetic complexes are also capable to assist the decomposition of superoxide ion, however, they show considerably smaller catalytic activity due to the absence of one of the cysteine residues.

Detailed equilibrium, spectroscopic and superoxide dismutase (SOD) activity studies are reported on a nickel complex formed with a new metallopeptide bearing two nickel binding loops of NiSOD. The metallopeptide exhibits unique nickel binding ability and the binuclear complex is a major species with 2×(NH2,Namide,S−,S−) donor set even in an equimolar solution of the metal ion and the ligand. Nickel(III) species were generated by oxidizing the NiII complexes with KO2 and the coordination modes were identified by EPR spectroscopy. The binuclear complex formed with the binding motifs exhibits superior SOD activity, in this respect it is an excellent model of the native NiSOD enzyme. A detailed kinetic model is postulated that incorporates spontaneous decomposition of the superoxide ion, the dismutation cycle and fast redox degradation of the binuclear complex. The latter process leads to the elimination of the SOD activity. A unique feature of this system is that the NiIII form of the catalyst rapidly accumulates in the dismutation cycle and simultaneously the NiII form becomes a minor species.

No abstract

Introduction:Ex vivo methylene blue (MB) injection into the main supplying arteries of the colorectal specimen after surgical removal is an uncomplicated technique to support lymph node harvest during pathological evaluation. The primary aim of this randomized, interventional, bicentric trial was to evaluate the impact of MB injection on lymph node yield, with secondary aims assessing the accuracy of lymph node staging and the effect on 5-year overall survival for patients undergoing resection of colorectal cancer.Methods: In the study period between December 2013 and August 2015, 200 colorectal resections were performed at two independent onco-surgery centers of Hungary. Following surgical resection, each specimen was randomly assigned either to the control (standard pathological work-up) or to the MB staining group before formaldehyde fixation. Patient-level surgical and clinical data were retrieved from routinely collected clinical datasets. Survival status data were obtained from the National Health Insurance Fund of Hungary.Results: A total of 162 specimens, 82 in the control and 80 in the MB groups, were included for analysis. Baseline characteristics were equally distributed among study groups, except for specimen length. Both the median of total number of lymph nodes retrieved (control 11 ± 8 [0–33] nodes vs. MB 14 ± 6 [0–42] nodes; p < 0.01), and the ratio of cases with at least 12 removed lymph nodes (36/82, 43.9% vs. 53/80, 66.3%; p < 0.01) were higher in the MB group. The rate of accurate lymph node staging was non-significantly improved. As for rectal cancer, nodal staging accuracy (16/31, 51.6% vs. 23/30, 76.7%; p = 0.04) and the proportion with minimum 12 lymph node retrieval (7/31, 22.6%, vs. 18/30, 60%; p < 0.01) was improved by MB injection. In Mantel–Cox regression, a statistically significant survival benefit with methylene blue injection at 5 years post-surgery was proven (51.2% vs. 68.8%; p = 0.04).Conclusion: In our experience, postoperative ex vivo arterial methylene blue injection appears to be an uncomplicated technique, improving lymph node yield and decreasing the chance of insufficient nodal staging. The technique might also associate with a 5-year overall survival benefit.