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Phthalate esters (PAEs) are emerging hazardous and toxic chemicals that are extensively used as plasticizers or additives. Diethyl phthalate (DEP) and dimethyl phthalate (DMP), two kinds of PAEs, have been listed as the priority pollutants by many countries. PAE hydrolases are the most effective enzymes in PAE degradation, among which family IV esterases are predominate. However, only a few PAE hydrolases have been characterized, and as far as we know, no crystal structure of any PAE hydrolases of the family IV esterases is available to date. HylD1 is a PAE hydrolase of the family IV esterases, which can degrade DMP and DEP. Here, the recombinant HylD1 was characterized. HylD1 maintained a dimer in solution, and functioned under a relatively wide pH range. The crystal structures of HylD1 and its complex with monoethyl phthalate were solved. Residues involved in substrate binding were identified. The catalytic mechanism of HylD1 mediated by the catalytic triad Ser140-Asp231-His261 was further proposed. The hylD1 gene is widely distributed in different environments, suggesting its important role in PAEs degradation. This study provides a better understanding of PAEs hydrolysis, and lays out favorable bases for the rational design of highly-efficient PAEs degradation enzymes for industrial applications in future., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal, relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Exposure to microgravity causes a decrease in bone mass and altered bone geometry due to the lack of weight-bearing forces on the skeleton. The mechanical properties of bone are due not only to the structure and geometry, but also to the tissue properties of the bone material itself. To study the effects of microgravity on bone tissue, the mechanical properties of tail suspension rat femurs were investigated. Twelve Sprague-Dawley rats were randomly divided into two groups, tail suspension (TS) and control (CON). On days 0 and 14, the bone mineral density (BMD) of the femurs was determined by Dual Energy X-ray Absorptiometry. After 14 days, three-point bending was used to test the mechanical properties of the whole femur and nanoindentation was used to measure the mechanical properties of the bone materials. The BMD of femurs in TS was significantly lower than that in CON. In the three-point bending testing, the breaking load, stiffness and energy absorption all decreased significantly in the TS group. In the nanoindentation tests, there was no significant difference between TS and CON in elastic modulus (E), while hardness (H) was significantly decreased and E/H significantly increased in TS. Weightlessness affects the intrinsic mechanical properties of bone at the bone material level. It is necessary to investigate further the effect of microgravity on the collagen bone matrix. Nanoindentation is a relatively new technique that is useful for investigating the above changes induced by microgravity and for assessing the efficacy of intervention.

Two-dimensional 1H/13C polarization inversion spin exchange at the magic angle experiments were applied to single crystal samples of amino acids to demonstrate their potential utility on oriented samples of peptides and proteins. High resolution is achieved and structural information obtained on backbone and side chain sites from these spectra. A triple-resonance experiment that correlates the 1H-13Calpha dipolar coupling frequency with the chemical shift frequencies of the alpha-carbon, as well as the directly bonded amide 15N site, is also demonstrated. In this experiment the large 1H-13Calpha heteronuclear dipolar interaction provides an independent frequency dimension that significantly improves the resolution among overlapping 13C resonances of oriented polypeptides, while simultaneously providing measurements of the 13Calpha chemical shift, 1H-13C dipolar coupling, and 15N chemical shift frequencies and angular restraints for backbone structure determination., (Copyright 1999 Academic Press.)