Deciphering of interactions between platinated DNA and HMGB1 by hydrogen/deuterium exchange mass spectrometry

A high mobility group box 1 (HMGB1) protein has been reported to recognize both 1,2-intrastrand crosslinked DNA by cisplatin (1,2-cis-Pt-DNA) and monofunctional platinated DNA using trans-[PtCl2(NH3)(thiazole)] (1-trans-PtTz-DNA). However, the molecular basis of recognition between the trans-PtTz-DNA and HMGB1 remains unclear. In the present work, we described a hydrogen/deuterium exchange mass spectrometry (HDX-MS) method in combination with docking simulation to decipher the interactions of platinated DNA with domain A of HMGB1. The global deuterium uptake results indicated that 1-trans-PtTz-DNA bound to HMGB1a slightly tighter than the 1,2-cis-Pt-DNA. The local deuterium uptake at the peptide level revealed that the helices I and II, and loop 1 of HMGB1a were involved in the interactions with both platinated DNA adducts. However, docking simulation disclosed different H-bonding networks and distinct DNA-backbone orientations in the two Pt-DNA-HMGB1a complexes. Moreover, the Phe37 residue of HMGB1a was shown to play a key role in the recognition between HMGB1a and the platinated DNAs. In the cis-Pt-DNA-HMGB1a complex, the phenyl ring of Phe37 intercalates into a hydrophobic notch created by the two platinated guanines, while in the trans-PtTz-DNA-HMGB1a complex the phenyl ring appears to intercalate into a hydrophobic crevice formed by the platinated guanine and the opposite adenine in the complementary strand, forming a penta-layer π–π stacking associated with the adjacent thymine and the thiazole ligand. This work demonstrates that HDX-MS associated with docking simulation is a powerful tool to elucidate the interactions between platinated DNAs and proteins

Bessel beam CARS of axially structured samples

We report about a Bessel beam CARS approach for axial profiling of multi-layer structures. This study presents an experimental implementation for the generation of CARS by Bessel beam excitation using only passive optical elements. Furthermore, an analytical expression is provided describing the generated anti-Stokes field by a homogeneous sample. Based on the concept of coherent transfer functions, the underling resolving power of axially structured geometries is investigated. It is found that through the non-linearity of the CARS process in combination with the folded illumination geometry continuous phase-matching is achieved starting from homogeneous samples up to spatial sample frequencies at twice of the pumping electric field wave. The experimental and analytical findings are modeled by the implementation of the Debye Integral and scalar Green function approach. Finally, the goal of reconstructing an axially layered sample is demonstrated on the basis of the numerically simulated modulus and phase of the anti-Stokes far-field radiation pattern

Effects of Digestive Enzymes on Rheological Properties and Microstructure of κ-Carrageenan/Casein Composite Systemsin vitro Simulated Digestion Environment

The combination of carrageenan and casein had a certain protective effect on the intestinal barrier. In order to study whether the digestive enzymes of the κ-carrageenan and casein in vitro digestion simulation were the main factors affecting the conformational transformation of polysaccharides or polysaccharide-protein composite systems, κ-carrageenan was used as the research object and the casein in cow's milk was selected as the target food matrix in this paper to explore the effect of digestive enzymes on the binding stability of κ-carrageenan/casein composite systems in vitro simulated digestion. The results showed that gastrointestinal digestive enzymes had little effect on the binding of κ-carrageenan to casein, but could significantly increase the exposure of sulfate groups in the system, which was not conducive to the configuration of κ-carrageenan. The casein in the system was decomposed into low molecular weight proteins or peptides, which increased the characteristic length of the composite system, weakened the interaction, decreased the viscoelasticity, and decreased the stability of the double helix structure. This study provides a theoretical basis for the safe application of κ-carrageenan

Interactions between Casein Micelles and Various Active Molecules and Properties of Their Complexes

In this study, binary and ternary complexes were prepared by heat treatment or combined heat and ultrasonic treatment using casein micelles (MC) as matrix and proanthocyanidin (PC), catechin (Cat) and chlorophyllin sodium copper salt (Chl) or their binary combinations as ligands. The interactions between PC, Cat, Chl or their binary combinations and MC were analyzed, and the binding capacity of MC to the various active molecules was evaluated. In addition, the structure, microscopic morphology and thermal stability of the complexes were characterized, and the antioxidant properties and in vitro digestibility of the ternary complexes were investigated as well. The results showed that PC, Cat and Chl formed binary complexes with MC through hydrophobic interactions, among which MC showed the highest affinity for Chl. Under heat treatment conditions, MC bound one molecule through hydrophobic interaction and another one by van der Waals forces and hydrogen bonds. At 298 K, the binding of the first molecule improved the binding constant and the number of binding sites of the second one. The binding of PC, Cat, Chl or their binary complexes had no significant effect on the spatial structure or microscopic morphology of MC. The thermal stability of MC was enhanced after the binding of bioactive molecules under heat treatment conditions. In terms of antioxidant properties, heat treatment promoted the 2,2’-azino bis-(3-ethylbenzthiazoline-6-sulfonicacid) (ABTS) radical cation scavenging activity of the ternary complexes, while combined heat and ultrasonic treatment promoted their 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity. In addition, the loading of active molecules improved the digestibility of MC in simulated intestinal fluid. This study could provide a reference for the application of MC in the loading of bioactive molecules

p53 upregulates PLCε-IP3-Ca2+ pathway and inhibits autophagy through its target gene Rap2B

The tumor suppressor p53 plays a pivotal role in numerous cellular responses as it regulates cell proliferation, metabolism, cellular growth, and autophagy. In order to identify novel p53 target genes, we utilized an unbiased microarray approach and identified Rap2B as a robust candidate, which belongs to the Ras-related GTP-binding protein superfamily and exhibits increased expression in various human cancers. We demonstrated that p53 increases the intracellular IP3 and Ca2+ levels and decreases the LC3 protein levels through its target gene Rap2B, suggesting that p53 can inhibit the autophagic response triggered by starvation via upregulation of the Rap2B-PLCε-IP3-Ca2+ pathway. As a confirmed target gene of p53, we believe that further investigating potential functions of Rap2B in autophagy and tumorigenesis will provide a novel strategy for cancer therapy

Automatic identification and analysis of cells using digital holographic microscopy and Sobel segmentation

Counting and analyzing of blood cells, as well as their subcellular structures, are indispensable for understanding biological processes, studying cell functions, and diagnosing diseases. In this paper, we combine digital holographic microscopy with cell segmentation guided by the Sobel operator using Dice coefficients for automatic threshold selection and aimed to automatic counting and analysis of blood cells in flow and different kinds of cells in the static state. We demonstrate the proposed method with automatic counting and analyzing rat red blood cells (RBCS) flowing in a microfluidic device, extracting quickly and accurately the size, concentration, and dry mass of the sample in a label-free manner. The proposed technique was also demonstrated for automatic segmentation of different cell types, such as COS7 and Siha. This method can help us in blood inspection, providing pathological information in disease diagnosis and treatment

Rheological properties and structural features of coconut milk emulsions stabilized with maize kernels and starch

peer-reviewedIn this study, maize kernels and starch with different amylose contents at the same concentration were added to coconut milk. The nonionic composite surfactants were used to prepare various types of coconut milk beverages with optimal stability, and their fluid properties were studied. The steady and dynamic rheological property tests show that the loss modulus (G″) of coconut milk is larger than the storage modulus (G′), which is suitable for the pseudoplastic fluid model and has a shear thinning effect. As the droplet size of the coconut milk fluid changed by the addition of maize kernels and starch, the color intensity, ζ-potential, interfacial tension and stability of the sample significantly improved. The addition of the maize kernels significantly reduced the size of the droplets (p < 0.05). The potential values of zeta (ζ) and the surface tension of the coconut milk increased. Based on the differential scanning calorimetry (DSC) measurement, the addition of maize kernels leads to an increase in the transition temperature, especially in samples with a high amylose content. The higher transition temperature can be attributed to the formation of some starches and lipids and the partial denaturation of proteins in coconut milk, but phase separation occurs. These results may be helpful for determining the properties of maize kernels in food-containing emulsions (such as sauces, condiments, and beverages) that achieve the goal of physical stability