Preparation of a hydrolyzed yeast β-glucan chromium(III) complex and evaluation of its hypoglycemic activity and sub-acute toxicity

Yeast β-glucan (BYG) possesses extremely low solubility that has limited its applications. In this study, we hydrolyzed BYG using snail enzyme to obtain hydrolyzed yeast β-glucan (HBYG) with desirable water solubility and hypoglycemic activity. On the basis of HBYG, HBYG‑chromium(III) complex (HBYG-Cr) was synthesized. The molecular weight of the complex was 4.41 × 104 Da, and the content of trivalent chromium was 8.95 %. The hydroxyl groups of HBYG participated in the coordination and formed the chromium complex. The space conformations of HBYG exhibited remarkable changes after complex formation. HBYG-Cr existed mainly in an amorphous state and presented good dispersibility, and the surface was uneven. The hypoglycemic activity of HBYG-Cr was studied in db/db and C57 mice. The results showed that HBYG-Cr had good hypoglycemic activity. Histopathological studies demonstrated that the liver, kidney, pancreas, and skeletal muscle in the treatment group were significantly improved compared with those in the diabetic model group. The sub-acute toxicity of HBYG-Cr was studied in KM mice and the results indicated that the complex did not cause adverse reactions or toxic side effects. This study broadened the application of yeast β-glucan and provided an important reference for the development of hypoglycemic functional foods and drugs.

Gold nanoparticle-based nano-probe for the colorimetric sensing of Cr3+ and Cr2O72- by the coordination strategy

In this work, an N-T/gold nanoparticle system was assembled for the convenient and colorimetric identification of Cr based on its coordination chemistry with the thymine derivative (N-T). In addition to the visible colorimetric changes for the qualitative Cr identification, the A_{630 nm/520 nm} values changed linearly with Cr concentration over a range of 0.5-2.5 μM and the detection limits reached 0.03 μM and 0.07 μM for Cr³⁺ and Cr₂O₇^2-, respectively, both of which satisfied the Cr water quality standards of the U.S. EPA, WHO and China. Furthermore, a more convenient method was developed for quantitative determination of Cr concentrations in practical samples based on the Eyedropper function in Microsoft's PowerPoint software, wherein the RGB (red, green and blue) value of the sample could be easily screened in the colorimetric card for a more accurate result with good recovery, avoiding complicated instrumentation.

High-resolution crystal structure of Z-DNA in complex with Cr(3+) cations

This work is part of our project aimed at characterizing metal-binding properties of left-handed Z-DNA helices. The three Cr³⁺ cations found in the asymmetric unit of the d(CGCGCG)₂–Cr³⁺ crystal structure do not form direct coordination bonds with atoms of the Z-DNA molecule. Instead, the hydrated Cr³⁺ ions are engaged in outer-sphere interactions with phosphate groups and O6 and N7 guanine atoms of the DNA. The Cr³⁺(1) and Cr³⁺(2) ions have disordered coordination spheres occupied by six water molecules each. These partial-occupancy chromium cations are 2.354(15) Å apart and are bridged by three water molecules from their hydration spheres. The Cr³⁺(3) cation has distorted square pyramidal geometry. In addition to the high degree of disorder of the DNA backbone, alternate conformations are also observed for the deoxyribose and base moieties of the G2 nucleotide. Our work illuminates the question of conformational flexibility of Z-DNA and its interaction mode with transition-metal cations.