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Angiogenesis is a hallmark of various pathological conditions and is controlled by a variety of angiogenic factors. Blockade of vascular endothelial growth factor (VEGF) as the most pivotal stimulator of angiogenesis offers a promising therapeutic approach for some diseases, typically cancer. In the present study, a heterodimeric antagonistic VEGF was precisely designed based on structural information of recently-crystallized VEGF/VEGF receptor- 2 (VEGFR-2/fetal liver kinase 1/kinase domain region) complex. Directed blocking of kinase domain region occurs via substitution of a VEGF receptor binding site by two peptide segments in one pole, whereas the binding domain of the other pole of VEGF was intact. Candidate peptides for substitution were selected considering to some sequence and structural criteria. A reliable model of modified VEGF was built, refined using molecular dynamics simulation and docked with VEGFR-2. Docking analysis revealed that binding affinity of mutant VEGF was notably diminished, corroborating our design. Heterodimeric VEGF was expressed, refolded and highly purified by two-step affinity chromatography. Dimerization of this antagonist was confirmed using some analytical techniques. Spectroscopic studies assured us to obtain the heterodimeric form of VEGF. Some angiogenic in vitro assays such endothelial cell proliferation and tube formation indicated that this antagonist is not only strongly capable of inhibiting angiogenesis (half maximal inhibitory concentration of 33 and 24 ng·mL -1, respectively), but also showed the highest inhibitory effect compared to all other heterodimeric VEGF variants. The high anti-angiogenic potency of this VEGF antagonist may allow its future use as an anti-tumor agent. [ABSTRACT FROM AUTHOR]

A method is described for the chemiluminescence based determination of the activity of catalase (CAT) using H2O2-sensitive CdTe quantum dots (QDs). It is based on the finding that the chemiluminescence (CL) of the CdTe/H2O2 system is reduced due to the consumption of H2O2 by the catalytic action of CAT. The Michaelis constant is calculated to be 519 ± 27 mM, showing the potential of the method to accurately measure the Km compared to the standard method. The method does not require QDs to be conjugated to biological/organic molecules and therefore is considered to be a rapid and convenient method for determination of CAT in real samples. At an incubation time of 2 s, the LOD was calculated to be 4.5 unit/mL, with a linear range from 6 to 400 unit/mL. The assay is sensitive, simple, and suitable for practical applications.Schematic representation of chemiluminescence-based catalase U(CAT) assay using the CdSe QD/H2O2 system. The reduction of H2O2 is reflected by the chemiluminescence of the QDs. A mechanism is put forward based on the changes in chemiluminescence intensity of the QDs by the consumption of H2O2 due to the catalytic action of CAT. [ABSTRACT FROM AUTHOR]

Background: Over the past twenty years, the prevalence of diabetes as one of the most common metabolic diseases has become a public health problem worldwide. Blood glucose control is important in delaying the onset and progression of diabetes-related complications. α-Glycosidase (α- Glu) and α-amylase (α-Amy) are important enzymes in glucose metabolism. Diabetic control through the inhibition of carbohydrate hydrolyzing enzymes is established as an effective strategy., Methods: In this study, curcumin-based benzaldehyde derivatives with high stability, bioavailability, and favorable efficiency were synthesized., Results: The results showed that L13, L8, and L11 derivatives have the highest inhibitory effect on α-Glu with IC 50 values of 18.65, 20.6, and 31.7 μM and, also L11, L13, and L8 derivatives have the highest inhibitory effect on α-Amy with IC 50 value of 14.8, 21.8, and 44.9 μM respectively. Furthermore, enzyme inhibitory kinetic characterization was also performed to understand the mechanism of enzyme inhibition., Conclusion: L13, compared to the other compounds, exhibited acceptable inhibitory activity against both enzymes. The L13 derivative could be an appropriate candidate for further study through the rational drug design to the exploration of a new class of powerful anti-diabetic drugs considering the antioxidant properties of the synthesized compounds. The derivative helps reduce the glycemic index and limits the activity of the major reactive oxygen species (ROS) producing pathways., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

Horseradish peroxidase (HRP) is usually used as a label enzyme in immunoassay so the method used for HRP detection in enzyme immunoassay (EIA) plays a key role in sensitivity and precision. The catalytic activity of HRP does not strictly follow classic Michaelis-Menten kinetics, probably due to the inactivation of the enzyme at high concentrations of H 2 O 2 . In this paper, a highly sensitive alternative procedure for the HRP assay using H 2 O 2 -sensitive CdTe quantum dots as a chemiluminescence (CL) system is reported. This method can measure a much more accurate and reliable value of K m (187 mM H 2 O 2 ) in comparison with the standard detection method. This system also was applied to thyroid hormone (T4) detection using HRP-based immunoassay. The QD/H 2 O 2 system exhibits a higher linear range of 0.2-16 μg/dL with the improved LOD value of 0.06 μg/dL and selective response to T4, which was better than the commercial colorimetric immunoassay. Meanwhile, the proposed method has been successfully applied to the clinical determination of T4 in the serum samples, and the results confirmed an excellent correlation with the conventional ELISA method (R 2 = 0.9832), indicating the potential applications of the method for clinical diagnosis as well., (Copyright © 2021 Elsevier B.V. All rights reserved.)