Anti-TYR monoclonal antibody, clone FQS21252

EPR spectroscopy is an important spectroscopic method for identification and characterization of radical species involved in many biological reactions. The tyrosyl radical is one of the most studied amino acid radical intermediates in biology. Often in conjunction with histidine residues, it is involved in many fundamental biological electron and proton transfer processes, such as in the water oxidation in photosystem II. As biological processes are typically extremely complicated and hard to control, molecular bio-mimetic model complexes are often used to clarify the mechanisms of the biological reactions. Here, we present theoretical calculations to investigate the sensitivity of magnetic resonance parameters to proton-coupled electron transfer events, as well as conformational substates of the molecular constructs which mimic the tyrosine-histidine (Tyr-His) pairs found in a large variety of proteins. Upon oxidation of the phenol, the Tyr analog, these complexes can perform not only one-electron one-proton transfer (EPT), but also one-electron two-proton transfers (E2PT). It is shown that in aprotic environment theg(X)-components of the electronicg-tensor are extremely sensitive to the first proton transfer from the phenoxyl oxygen to the imidazole nitrogen (EPT product), leading to a significant increase of theg(X)-value of up to 0.003, but are not sensitive to the second proton transfer (E2PT). In the latter case, the change of theg(X)-value is much smaller (ca. 0.0001), which is too small to be distinguished even by high-frequency EPR. The(14)N hyperfine values are also too similar to allow differentiation between the different protonation states in EPT and E2PT. The magnetic resonance parameters were also calculated as a function of the rotation angles around single bonds. It was demonstrated that rotation of the phenoxyl group results in large positive changes (> 0.001) in theg(X)-values. Analysis of the data reveals that the main source of these changes is related to the strength of the H-bond between phenoxyl oxygen and the proton(s) on N(1)and N(2)positions of the imidazole.

Chokeberries (Aronia melanocarpa (Michx.) Elliot have recently become one of the most popular and widely used berry fruits, and there are numerous studies dealing with the investigation of their chemical composition and biological activities. Unlike berries, chokeberry leaves were far less investigated. Therefore, the aim of this study was to conduct a bioactivity-based analysis of chokeberry leaves collected after berries were harvested. Chemical analysis of hydroethanolic chokeberry extract and its ethyl acetate, n-butanol, and water fractions was performed. Antioxidant, hypoglycemic, and antineurodegenerative activities of the obtained samples were assessed by in vitro tests. The highest total phenolics content was found in n-butanol fraction (221.5 mg gallic acid equivalents/g dw). Fourteen compounds (six phenolic acids and eight flavonoids) were identified in the samples. Caffeoylquinic acid derivatives and quercetin glycosides were dominant phenolic compounds. The highest content of phenolic acids, as well as flavonoids, was recorded in n-butanol fraction (80.75 mg/g dw and 47.79 mg/g dw, respectively). This fraction was the most active in 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis (3-ethyl-benzothiazoline-6-sulfonic acid) (ABTS), and ferric reducing antioxidant power (FRAP) assays. Also, the n-butanol fraction was the most effective inhibitor of acetylcholinesterase (AChE) and tyrosinase (TYR) enzymes. All samples showed a better inhibitory effect on alpha-glucosidase enzyme with inhibition concentrations IC50 = 4.21 - 9.22 mu g/mL, than alpha-amylase enzymes (IC50 = 14.36 - 88.61 mu g/mL). Pearson's correlation between the content of individual phenolics and the results of biological tests was performed. Thus, hyperoside and isoquercitrin showed a significant correlation with DPPH and ABTS tests, caffeoylquinic acids with FRAP test, quercetin 3-O-vicianoside with beta-carotene assay, hyperoside and isoquercitrin with alpha-amylase inhibition activity, and isorhamnetin 3-O-rutinoside with alpha-glucosidase inhibition assay. Considering the obtained results, chokeberry leaves represent a valuable natural source of phenolic compounds with promising potential for the development of new products with beneficial effects on human health.