Identification, characterization, and insights into the mechanism of novel dipeptidyl peptidase-IV inhibitory peptides from yak hemoglobin by in silico exploration, molecular docking, and in vitro assessment

Dipeptidyl peptidase IV (DPP-IV) inhibitory peptides were screened and identified from yak hemoglobin for the first time by in silico analysis, molecular docking, and in vitro evaluation. Results showed that yak hemoglobin had a high potential to produce DPP-IV inhibitory peptides based on the sequence alignment and bioactive potential evaluation. Furthermore, "pancreatic elastase + stem bromelain" was the optimal combined-enzymatic strategy by simulated proteolysis. Additionally, 25 novel peptides were found from its simulated hydrolysate, among which 10 peptides had high binding affinities with DPP-IV by molecular docking. Most of these peptides were also in silico characterized with favorable physicochemical properties and biological potentials, including relatively low molecular weight, high hydrophobicity, several net charges, good water solubility, nontoxicity, acceptable sensory quality, and good human intestinal absorption. Finally, six novel DPP-IV inhibitory peptides were identified via in vitro assessment, among which EEKA (IC50 = 235.26 μM), DEV (IC50 = 339.45 μM), and HCDKL (IC50 = 632.93 μM) showed the strongest capacities. The hydrogen bonds and electrostatic attractions formed with core residues within the S2 pocket of DPP-IV could be mainly responsible for their inhibition performances. This work provided a time-saving method and broadened application for yak by-products development as sources of functional foods.

In vitro digestion and fermentation combined with microbiomics and metabolomics reveal the mechanism of superfine yak bone powder regulating lipid metabolism by altering human gut microbiota

The effects of superfine yak bone powder (YBP) on human gut microbiota (HGM) were investigated by in vitro digestion and fermentation combined with microbiomics and metabolomics. Results showed that size reduction and protein structural degradation during digestion allowed superfine YBP to release more Ca²⁺ than CaCO₃ powders with similar particle size. Moreover, the indigestible YBP further influenced HGM and was associated with increased occurrence of beneficial bacteria such as Megasphaera spp., Megamonas spp., Acidaminococcus spp., and Prevotella spp. The altered HGM was associated with greater production of short-chain fatty acids with 4-6 carbon atoms. Furthermore, the indigestible YBP was associated with up-regulation of many lipid-related metabolites, including taurine, secondary bile acids, saturated long-chain fatty acids, and ω-3/ω-6 polyunsaturated fatty acids, which modulated favorably lipid metabolic pathways. These findings implied the potential activity of superfine YBP as a food fortifier in favorably altering HGM community structure and regulating lipid metabolism.

[Preparation of zirconia for high performance liquid chromatography using sol-gel technology]

Zirconia sol was prepared by dissolving zirconyl chloride in water, and the sol formed gel in water/cyclohexane W/O style emulsion to obtain monodispersed particles of ZrO2(2-10 microns). After being washed and classified, the zirconia particles (3-5 microns) were collected and calcined at 800 degrees C to remove the organic residues on the surface of the particles. The mean pore diameter, specific surface area and specific pore volume of the zirconia particles were found to be 14.2 nm, 11.2 m2/g, and 0.04 cm3/g, respectively, by means of the BET method. The adsorption behavior of various organic compounds on the ZrO2 shows it will be useful as a column packing material for high performance liquid chromatography.

[Retention behavior of solutes on liquid chromatographic column packed with dynamically modified zirconia]

Zirconia was dynamically modified with stearic acid, beta-cyclodextrin and sodium dodecylsulfonate, separately, to form liquid chromatographic packings. The chromatographic behaviors of aromatic hydrocarbons, acidic compounds (phenol, nitrophenols and benzoic acids) and basic compounds (aniline, nitroanilines and toluidines) were investigated on these modified zirconia packings with a mixture of methanol/water as the mobile phase. On stearic acid modified zirconia, aromatic hydrocarbons and the basic compounds exhibit symmetrical peaks. The retention time of these solutes decreases with increasing the concentration of methanol in the mobile phase. When the mobile phases with stearic acid were used, the retention time of these solutes has a maximum with variation of stearic acid concentration (0-1.0 mmol/L) in the mobile phase. However, the acidic compounds such as nitrophenols and benzoic acids are strongly adsorbed and can not be eluted from the column with the mobile phases. No leaking of stearic acid on the modified zirconia was found after 3000 column volumes of the methanol/water mobile phase were used. The results showed that the stearic acid modified zirconia can be used as a stationary phase for reversed-phase liquid chromatography. On beta-cyclodextrin modified zirconia, aromatic hydrocarbons and basic compounds exhibit shorter retention time than those on the stearic acid modified zirconia under the same mobile phase composition, however, nitrophenols can be eluted but give unsymmetrical peaks. On sodium dodecylsulfonate modified zirconia packings, the basic compounds can not be retarded; Aromatic hydrocarbons and acidic compounds exhibit short retention time. The results can be ascribed to the weak adsorption of sodium dodecylsulfonate on the zirconia.

[Study on high performance liquid chromatography/indirect photometric detection of fosfomycin with acridine as detection reagent]

Fosfomycin is a broad-spectrum antibacterial agent which has strong polarity and weak UV absorption. In this work, a method using standard ODS column and conventional UV detector set at 254 nm to analyse fosfomycin was investigated. Firstly, several UV detection reagents were tested and acridine(A) was found to give the highest indirect detection response and proper modification on retention of fosfomycin. With acridine as the UV detection reagent, the mobile phase parameters which affect retention and detection response of solute are discussed, e.g. pH, concentration of organic solvent and concentration of acridine. The mechanism is interpreted for each case. After optimization, we adopted mobile phase as V(CH3OH):V(H2O) = 50:50, pH 3.18, [HAc] = 2 mmol/L, [A] = 1 x 10(-5) mol/L. A new chromatographic system monitored by indirect photometry for detection of fosfomycin was established. This method was used for quantitative analysis, the minimum detectable level was 10 mumol/L, the relative deviation was 4.51%.

[Preparation and evaluation of C60 bonded silica phase for high performance liquid chromatography]

C60 was chemically attached to gamma-(ethylenediamino) propylsilyl-bonded silica as a stationary phase for liquid chromatography. The new stationary phase was used to investigate the separations of polycyclic aromatic hydrocarbons (PAHs) and tert-butylcalix[n]arenes. The elution order of PAHs was found to be similar to that on octadecylsilica (ODS); the elution order of tert-butylcalix[n]arenes was found to be tert-butylcalix[8]arene, tert-butylcalix[4]arene and tert-butylcalix[6]arene with 1%(V/V) isopropanol/cyclohexane as a mobile phase.

[Studies on the performance and applications of chloropropyl bonded silica. I. Separation of disubstituted benzene isomers and prostaglandin epimers]

The performance of chloropropyl bonded silica (CPS) in HPLC and its applications in separation of disubstituted benzene isomers and prostaglandin epimers were studied. The CPS column has high column efficiency and the kinetic curves illustrate it is suitable for fast analysis. The effect of composition and pH value of mobile phase (methanol/water or methanol/20 mmol/L H3PO4-NaOH buffer) on the retention of the solutes were investigated. Generally, the main retention mechanism of solutes was hydrophobic interaction, however there also exited polar adsorption interaction, ion-dipole interaction etc. When the mobile phase condition changed, the main separating mechanism may be changed with CPS column. So, with increasing pH value of mobile phase, the retention of isomers of nitrophenol exhibited a parabolic change. The chromatographic condition was optimized, and the isomers of nitrophenol, aminophenol and toluidine etc. as well as the epimers of 15-methyl-PGF2alpha were separated very well on the column. Moreover, the speed of separation was faster than that in general reversed-phase system. CPS showed to have good stability to heat and solvent and it was also a very stable intermediate to prepare bonded phase with various functional groups.