Characterization of iron(III)porphyrin-hydroxo complexes in organic media through UV-Vis and EPR spectroscopies

Biochemical Resistivity against Free Radicals and Microbes: Cooperative Action of Zn(II)/Imidazole in Phosphoesterase-Mediated Cell Death

This work delivers a targeted synthesis of four isostructural O-substituted imidazole-based zinc(II) complexes, namely, [Zn2(L1)2(I)2](DMF) (1), [Zn2(L2)2(I)2](DMF) (2), [Zn2(L1)2(Br)2] (3), and [Zn2(L2)2(Br)2] (4), derived from homologous Schiff-base ligands HL1 and HL2 to explore their impact on free radicals, microbes, and dephosphorylation of phosphoesters. The antioxidant activity of all complexes was checked by various radical scavenging assays (ABTS+•, DPPH•, and H2O2 radical quenching). Among them, complex 2 showed superior radical quenching activity, as indicated by its lowest EC50 value and thus maximum antioxidative capability. Again, antibacterial assays against several Gram-positive and Gram-negative bacteria were conducted to evaluate the zone of inhibition. The minimum bactericidal concentration and minimum inhibitory concentration values from the microdilution method for all complexes revealed complex 3 to have maximum potency against Gram-positive bacteria. The P-O bond hydrolysis in the phospholipid chain caused by the hydrolytic phosphoesterase activity of the Zn(II)-complexes plays a crucial role in cell membrane rupture. A model substrate 4-PNPP was used to explain the potency of monomeric Zn(II) complex (3) for cell penetration over dimeric one (2) with a proper mechanism. Furthermore, a heme model substrate, Fe(TPP)Cl, has been introduced with the most potent complex 3 and has spectrophotometric evidence for covalent interaction with imidazole and Fe(III) that can disrupt the nitric oxide dioxygenase function of flavohemoglobin, leading to bacterial cell death. To our knowledge, this is the first case to report a novel mechanism of antimicrobial action where both the metal and the ligand are cooperatively involved in bacterial cell death. The main goal of this work is to invent multifunctional therapeutics as well as the proper chemical rationalization of biological processes using mechanistic approaches, which includes investigating the roles of halides, imidazoles, and solution-phase structural variations of complexes..

Differences in global gene expression in muscle tissue of Nellore cattle with divergent meat tenderness

Background

Meat tenderness is the consumer’s most preferred sensory attribute. This trait is affected by a number of factors, including genotype, age, animal sex, and pre- and post-slaughter management. In view of the high percentage of Zebu genes in the Brazilian cattle population, mainly Nellore cattle, the improvement of meat tenderness is important since the increasing proportion of Zebu genes in the population reduces meat tenderness. However, the measurement of this trait is difficult once it can only be made after animal slaughtering. New technologies such as RNA-Seq have been used to increase our understanding of the genetic processes regulating quantitative traits phenotypes. The objective of this study was to identify differentially expressed genes related to meat tenderness, in Nellore cattle in order to elucidate the genetic factors associated with meat quality. Samples were collected 24 h postmortem and the meat was not aged.

Results

We found 40 differentially expressed genes related to meat tenderness, 17 with known functions. Fourteen genes were up-regulated and 3 were down-regulated in the tender meat group. Genes related to ubiquitin metabolism, transport of molecules such as calcium and oxygen, acid-base balance, collagen production, actin, myosin, and fat were identified. The PCP4L1 (Purkinje cell protein 4 like 1) and BoLA-DQB (major histocompatibility complex, class II, DQ beta) genes were validated by qRT-PCR. The results showed relative expression values similar to those obtained by RNA-Seq, with the same direction of expression (i.e., the two techniques revealed higher expression of PCP4L1 in tender meat samples and of BoLA-DQB in tough meat samples).

Conclusions

This study revealed the differential expression of genes and functions in Nellore cattle muscle tissue, which may contain potential biomarkers involved in meat tenderness.

Electronic supplementary material

The online version of this article (10.1186/s12864-017-4323-0) contains supplementary material, which is available to authorized users.

Intersystem Crossing versus Electron Transfer in Porphyrin-Based Donor−Bridge−Acceptor Systems: Influence of a Paramagnetic Species

We have investigated how the spin state of an acceptor influences the photophysical processes in a donor-bridge-acceptor (D-B-A) system. The system of choice has zinc porphyrin as the electron donor and high- or low-spin iron(III) porphyrin as the acceptor. The spin state of the acceptor porphyrin is switched simply by coordinating imidazole ligands to the metal center. The D-A center-center distance is 26 A, and the bridging chromophore varies from pi-conjugated to a sigma-bonded system. The presence of a high-spin iron(III) porphyrin in such systems has previously been shown to significantly enhance intersystem crossing in the remote zinc porphyrin donor, whereas no significant electron transfer to the iron porphyrin acceptor was observed, even though the thermodynamics would allow for photoinduced electron transfer. Here, we demonstrate that by switching the acceptor to a low-spin state, the dominating photophysical process is drastically changed; the low-spin system shows long-range electron transfer on the picosecond time-scale, and intersystem crossing occurs at its "normal" rate.