In this study, walnut meal hydrolysates (WMH) and dephenolized walnut meal hydrolysates (DWMH) were found to effectively decrease the serum uric acid level and protect the renal function in potassium oxonate-induced hyperuricemic rats in vivo as well as inhibit xanthine oxidase in vitro. Two novel antihyperuricemic peptides including WPPKN (640.8 Da) and ADIYTE (710.7 Da) were purified from DWMH via Sephadex G-15 gel filtration and reverse-phase high-performance liquid chromatography and identified by LC-ESI-MS/MS. These peptides displayed high in vitro xanthine oxidase inhibition (XOI) activity with IC values of 17.75 ± 0.12 mg mL (WPPKN) and 19.01 ± 0.23 mg mL (ADIYTE). Based on the results of molecular simulation, WPPKN entered into the hydrophobic channel and even obstructed the interaction between xanthine and xanthine oxidase (XO), while ADIYTE was positioned on the surface of the B-chain and blocked the entrance of the substrate to the hydrophobic channel. Therefore, the two peptides are partially responsible for the antihyperuricemic properties of DWMH.
In this study, we propose a new approach to generate two-dimension spectra to enhance the intensity of cross peaks relevant to intermolecular interaction. We investigate intermolecular interaction between two solutes (denoted as P and Q, where P has a characteristic peak at X) dissolved in the same solvent via the near diagonal cross peaks around the coordinate (X, X) in a two-dimensional (2D) asynchronous spectrum of generalized spectroscopy. Because of physical constrains in many cases, the variation ranges of the initial concentrations of P or Q must be kept very narrow, leading to very weak cross peak intensities. The weak cross peaks vulnerable to noise bring about difficulty in the investigation of subtle intermolecular interaction. Herein, we propose a new of way constructing a 2D asynchronous spectrum without the subtraction of the average spectrum often used as a reference spectrum. Mathematical analysis and computer simulation demonstrate that the near diagonal cross peaks around the coordinate (X, X) in the 2D asynchronous spectrum using the new approach possess two characteristics: (1) they can still reflect an intermolecular interaction reliably; 2) the absolute intensities of the cross peaks are significantly stronger than those generated by the conventional method. We incorporate the novel method with the DAOSD (double asynchronous orthogonal sample design scheme) approach and applied the modified DAOSD approach to study hydrogen bonding behavior in diethyl either/methanol/THF system. The new approach made the weak cross peaks, which are not observable in 2D asynchronous spectrum generated using conventional approach, become observable. The appearance of the cross peak demonstrate that When a small amount of THF is introduced into diethyl solution containing low amount of methanol, THF breaks the methanol-diethyl ether complex and forms methanol-THF complex via new hydrogen bond. This process takes place in spite of the fact that the content of diethyl ether is overwhelmingly larger than that of THF. The above result demonstrates that the new approach described in this article is applicable to enhance intensity of cross peaks in real chemical systems.
Single-crystal
structures of five lanthanide–erythritol
complexes are reported. The analysis of the chemical compositions
and scrutinization of structural features in the single-crystal data
of the complexes led us to find that unexpected deprotonation occurs
on the OH group of erythritol of three complexes. Considering these
complexes were prepared in acidic environments, where spontaneous
ionization on an OH group is suppressed, we suggest metal ions play
an important role in promoting the proton transfer. To find out why
the chemically inert OH is activated, the single-crystal structures
of 63 rare-earth complexes containing organic ligands with multiple
hydroxyl groups (OLMHs) were surveyed. The formation of μ2-bridges turns out to be directly relevant to the occurrence
of deprotonation. When an OH group from an OLMH molecule participates
in the formation of a μ2-bridge, the polarization
ability of the metal ions becomes strong enough to promote the deprotonation
on the OH group. The above structural characteristics may be useful
in the rational design of catalysts that can activate the chemically
inert OH group and promote the relevant chemical conversions.
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