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In this study, we investigated the effects of different Ca2+ and Mg2+ concentrations in the water column on the growth and molting of Macrobrachium rosenbergii. We used three concentrations of both Ca2+ and Mg2+ and tested these in culture experiments over a period of four complete molting cycles. Analyses revealed that increasing concentrations of Ca2+ in the water led to a gradual reduction in the expression levels of MIH and a gradual increase in the expression levels of EcR and chitinase, thus accelerating molting frequency and shortening the molting cycle. However, high concentrations of Ca2+ significantly reduced the survival rate of M. rosenbergii. Increasing concentrations of Mg2+ in the water column led to a significant increase in heart beat count (P < 0.05); in addition, malate dehydrogenase activity during postmolt A and intermolt C tended to increase, and energy metabolism was accelerated. Furthermore, increased Ca2+ concentrations in the water column promoted an increase in the Ca2+ content of muscles and shells. In contrast, as the Mg2+ concentration in the water column increased, the Mg2+ content in the muscles and shells showed different patterns of change. Too low or too high Ca2+ and Mg2+ concentrations in the external environment had differing degrees of negative effects on the gill tissue such as edema and necrosis. In summary, low levels of Ca2+ and Mg2+ in the external environment reduced ion levels in the muscle and shell; inhibited growth, molting, and survival; and exerted negative effects on the gill tissue. Furthermore, high concentrations of Ca2+ and Mg2+ may accelerate molting rate and energy metabolism, but can cause more serious damage to gill tissue and reduce the survival rate. [ABSTRACT FROM AUTHOR]

C26H26N6O5, monoclinic, P21/c (no. 14), a = 10.9393(1) Å, b = 16.8724(2) Å, c = 13.5836(2) Å, β = 102.843(1)°, V = 2444.43(5) Å3, Z = 4, Rgt(F) = 0.0318, wRref(F2) = 0.0827, T = 173 K. [ABSTRACT FROM AUTHOR]

In the present paper, on the basis of molecular hybridization, a series of 4,6-dihydrazone pyrimidine derivatives containing the pyridine moiety were synthesized, structurally characterized, and evaluated in vitro for their antitumor activity. According to the results, all the tested compounds demonstrated broad-spectrum antitumor activity against selected tumor cell lines (MCF-7, BGC-823, A549, and BEL-7402) and no obvious toxicity toward normal cells HL-7702. In particular, compounds 10a and 10f were found to be the most promising antitumor agents among the tested compounds against BGC-823 cells (IC50 = 9.00 μM and 7.89 μM) and BEL-7402 cells (IC50 = 6.70 μM and 7.66 μM), respectively. Compounds 10a and 10f exhibited higher potency against BGC-823 and BEL-7402 than the positive control 5-FU (IC50 = 15.18 μM and 15.81 μM). Further mechanism investigations demonstrated that compounds 10a and 10f could significantly increase the level of cellular ROS and induce early apoptosis of BGC-823 cells in a dose-dependent manner. Moreover, the DNA binding results from UV/Vis, CD spectroscopy, and molecular docking studies indicated that 10a and 10f bind with DNA via groove binding and partial intercalation. These results demonstrated that 10a and 10f may serve as novel lead compounds for the discovery of more dihydrazone pyrimidine derivatives with improved antitumor potency and selectivity. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the effect of pH-mediated surface properties of bovine serum albumin (BSA) on protein aggregation and the changes of protein structure and colloidal stability at different solution pH levels. The hydrophobicity of BSA surface was characterized by endogenous fluorescence spectroscopy, fluorescence quenching of acrylamide, and fluorescence probe. The results showed that the hydrophobicity of BSA surface was similar at pH 5, 6, 7.4, followed by pH 4, 8, 9, 10, and finally by pH 3 and 11 with strong acidity and alkalinity. The positive charge on the BSA surface was increased gradually with the decrease of solution pH, while the negative charge on protein surface was increased gradually with the increase of solution pH. The degree of protein aggregation was examined by turbidimetry, flow cytometry, and SDS-PAGE. The results showed that the oscillating aggregation of BSA did not change with the solution pH, but was partially dependent on the relative contribution of electrostatic and hydrophobic interactions between the protein molecules. In addition, the secondary structure, conformational stability, unfolding degree, and colloidal stability of proteins were investigated by circular dichroism, fluorescence spectroscopy, protein pulse hydrolysis, and dynamic light scattering, respectively. The results suggested that the solution pH could change the structure and stability of the protein at different levels. Solution pH has distinct effects on the structural stability of protein at different levels. The change of protein surface properties mediated by solution pH is related to protein aggregation. [ABSTRACT FROM AUTHOR]

Purpose: Understanding the mechanism of protein-excipient interaction and illuminating the influencing factors on protein stability are key steps in the rational design of protein formulations. The objective of this study was to assess effects of preferential interaction type of excipient and surface aromatic hydrophobicity of protein on protein solution stability. Methods: The preferential interaction between excipient and aromatic hydrophobic area of protein was investigated by solubility and fluorescence studies of amino acid derivatives in excipient solutions. We examined conformational, colloidal and mechanical stabilities of model proteins with different surface aromatic hydrophobicities, including bovine serum albumin (BSA) and ovalbumin (OVA), and then stability data were visualized by three-index empirical phase diagram. Results: The result showed that preferentially excluded excipients (trehalose, sucrose and sorbitol) protected protein conformation against damage, but they could accelerate mechanical stress-induced aggregation. Preferentially bound excipients (propanediol and arginine) suppressed BSA aggregation, but arginine failed to inhibit OVA aggregation, which might be attributed to the disparate conformational perturbing effects of arginine on aromatic hydrophobic regions of BSA and OVA. Conclusions: These findings provided strong evidence that excipient possessed bilateral effects, and its application should be determined on different preferential interaction behaviors of excipients with protein, especially with the aromatic hydrophobic region. [ABSTRACT FROM AUTHOR]