The stability issue of fractured rock mass slope under the influences of freeze-thaw cycle.

Freeze-thaw failure of frozen rock slope often occurs during engineering construction and mining in cold area, which poses a great threat to engineering construction and people's life safety. The properties of rock mass in cold region will change with the periodic change of temperature, which makes it difficult to accurately evaluate the stability of slope under the action of freeze-thaw cycle by conventional methods. Based on field investigation and literature review, this paper discusses the characteristics of frozen rock mass and the failure mechanism of frozen rock slope, and gives the types and failure modes of frozen rock slope. Then, the research status of frozen rock slope is analyzed. It is pointed out that the failure of frozen rock slope is the result of thermo-hydro-mechanical (THM) coupling. It is considered that freeze-thaw cycle, rainfall infiltration and fracture propagation have significant effects on the stability of frozen rock slope, and numerical simulation is used to demonstrate. The research shows that the safety factor of frozen rock slope changes dynamically with the surface temperature, and the safety factor of slope decreases year by year with the increase of freeze-thaw cycles, and the fracture expansion will significantly reduce the safety factor. Based on the above knowledge, a time-varying evaluation method of frozen rock slope stability based on THM coupling theory is proposed. This paper can deepen scholars' understanding of rock fracture slope in cold area and promote related research work.

Effects of Strain and Kinetics on the H2O2-Assisted Reconstruction of Ag-Au-Ag Nanorods.

Morphology of Ag nanocrystals (NCs) is essential to the NC application in catalysis, optics, and as antibacterial agents. Therefore, it is important to develop synthetic methods and understand the evaluation of NC morphology in different chemical environments. In this study, we report interesting findings of the morphological change of fivefold-twinned Ag-Au-Ag nanorods (NRs) under the effect of H2O2 both as an oxidant (etchant) and a reductant. At low H2O2 concentration, the reconstruction of Ag-Au-Ag NRs was dominated by the growth along the longitudinal direction of NRs. With the increase of H2O2 concentration, the reconstruction also occurs in the transverse direction, and a clear change in particle morphology was observed. We further systematically studied the mechanism of the reaction. The results showed that the transition of the morphology was a two-step process: (1) the etching of Ag on the seeds and (2) the reduction of Ag2O. In the second step, the reaction kinetics was highly affected by H2O2 concentration. At low H2O2 concentration, the growth mainly occurs along ⟨110⟩. However, at high H2O2 concentration, the reduction of Ag was not facet-selective. Using the developed method, we can prepare various bimetallic NCs (high aspect ratio NRs with abundant pinholes, nanoplates, and other NCs). The effect of the reconstruction process on the surface-enhanced Raman scattering (SERS) performance of NCs was investigated.

Cleavable Linkers in Chemical Proteomics Applications.

The discovery of the protein targets of small molecule probes is a crucial aspect of activity-based protein profiling and chemical biology. Mass spectrometry is the primary method for target identification, and in the last decade, cleavable linkers have become a popular strategy to facilitate protein enrichment and identification. In this chapter, we provide an overview of cleavable linkers used in chemical proteomics approaches, discuss their different chemistries, and describe how they aid in protein identification.

Interaction of endokinin A/B and (Mpa(6))-γ2-MSH-6-12 in pain regulation in mice.

The present study focused on the interactive effects of (Mpa(6))-γ2-MSH-6-12 (Mpa, spinal level) and endokinin A/B (EKA/B, supraspinal level) on pain regulation in mice. EKA/B (30 pmol) only weakened 100 pmol Mpa-induced hyperalgesia at 5 min, but could enhance it during 20-30 min. However, EKA/B (100 pmol) antagonized all dose levels of Mpa significantly at 5 min and blocked them completely at 10 min. EKA/B (3 nmol) co-injected with Mpa presented marked analgesia at 5 min and enduring hyperalgesia within 20-60 min. To investigate the underlying mechanisms between Mpa and EKA/B, SR140333B and SR142801 (NK1 and NK3 receptor antagonists, respectively) were utilized. SR140333B had no influence on Mpa, while SR142801 potentiated it during 20-30 min. Whereas, SR140333B and SR142801 could block the co-administration of Mpa and EKA/B (30 pmol) separately at 5 min and 30 min. These phenomena might attribute to that these two antagonists promoted the antagonism of EKA/B (30 pmol) at the early stage, while antagonized EKA/B preferentially in the latter period. SR140333B weakened the analgesia of EKA/B (3 nmol), but produced no effect on Mpa. However, SR140333B failed to affect the co-injection of Mpa and EKA/B, which implied that EKA/B cooperated with Mpa prior to SR140333B. These results could potentially help to better understand the interaction of NK and MrgC receptors in pain regulation in mice.

Comparative analysis of click chemistry mediated activity-based protein profiling in cell lysates.

Activity-based protein profiling uses chemical probes that covalently attach to active enzyme targets. Probes with conventional tags have disadvantages, such as limited cell permeability or steric hindrance around the reactive group. A tandem labeling strategy with click chemistry is now widely used to study enzyme targets in situ and in vivo. Herein, the probes are reacted in live cells, whereas the ensuing detection by click chemistry takes place in cell lysates. We here make a comparison of the efficiency of the activity-based tandem labeling strategy by using Cu(I)-catalyzed and strain-promoted click chemistry, different ligands and different lysis conditions.

Cleavable trifunctional biotin reagents for protein labelling, capture and release.

Trifunctional biotin reagents incorporating cleavable linkers are evaluated for their usage in protein enrichment. A linker based on the Dde protecting group leads to efficient release of protein targets under mild conditions. It additionally contains a masked trypsin cleavage site, which eliminates the majority of the tag during tryptic digestion.

Tuning probe selectivity for chemical proteomics applications.

Covalent chemical probes enable investigation of a desired fraction of the proteome. It is possible to adjust the selectivity of these probes, so they either react with a certain amino acid in all proteins, a class of proteins or only a single protein species. A combination of specific reactive groups with additional recognition elements can fine tune probes to hit the desired proteins, even in the presence of related family members. Using probes of lower or higher selectivity, screening experiments for inhibitor discovery and imaging experiments for localization studies can be performed, showing only a fraction of the power of covalent small molecule probes.

Target profiling of 4-hydroxyderricin in S. aureus reveals seryl-tRNA synthetase binding and inhibition by covalent modification.

4-Hydroxyderricin is a heat labile bioactive chalcone isolated from the plant Angelica keiskei. It received attention due to its antibiotic potency against several strains of bacteria including pathogens such as Staphylococcus aureus. Despite these promising pharmacological properties, the exact mode of action or the biological targets are still unknown. Here we report the synthesis and the application of a 4-hydroxyderricin probe for activity-based protein profiling (ABPP) in S. aureus. Due to the heat sensitivity of the natural product we utilize a chemical tool for the mild and selective enrichment of labile probe-protein conjugates and report seryl-tRNA synthetase (STS) to be covalently modified by our probe. This modification results in inhibition of the amino acylation of tRNAs catalyzed by S. aureus STS which is an essential enzymatic pathway for bacterial viability.

A simple and effective cleavable linker for chemical proteomics applications.

The study of metabolically labeled or probe-modified proteins is an important area in chemical proteomics. Isolation and purification of the protein targets is a necessary step before MS identification. The biotin-streptavidin system is widely used in this process, but the harsh denaturing conditions also release natively biotinylated proteins and non-selectively bound proteins. A cleavable linker strategy is a promising approach for solving this problem. Though several cleavable linkers have been developed and tested, an efficient, easily synthesized, and inexpensive cleavable linker is a desirable addition to the proteomics toolbox. Here, we describe the chemical proteomics application of a vicinal diol cleavable linker. Through easy-to-handle chemistry we incorporate this linker into an activity-based probe and a biotin alkyne tag amenable for bioorthogonal ligation. With these reagents, background protein identifications are significantly reduced relative to standard on-bead digestion.

Effects of endokinin A/B and endokinin C/D on the antinociception properties of hemopressin in mice.

The current study evaluated the effects of hemopressin (HP) on pain modulation by endokinin A/B (EKA/B) and endokinin C/D (EKC/D) at the supraspinal level in mice. Intracerebroventricular administration of HP (10 nmol) fully antagonized the hyperalgesia induced by EKA/B (10, 30, and 100 pmol), and induced a dose-dependent potent analgesic effect. HP at different concentrations (10 pmol, 100 pmol, and 1 nmol) showed varying effects on the analgesic effect of EKA/B (3 nmol). HP extended the duration of the analgesic effect of EKC/D (3 nmol). Moreover, HP at different concentrations (10 pmol, 5 pmol, 1 pmol, and 100 fmol) co-administered with EKC/D (30 pmol) induced significant analgesia at two different time points: 5 min and 50 min. To investigate the antinociceptive mechanism, we used SR140333B and SR142801. HP (1 pmol) potentiated the analgesic effect of SR140333B (100 pmol)+EKA/B (30 pmol) in 5-10 min, while HP (100 pmol) had no effect in the analgesia induced by SR140333B (3 nmol)+EKA/B (3 nmol). HP (1 nmol) fully inhibited the analgesic effect of SR140333B (3 nmol)+EKC/D (3 nmol) or SR142801 (3 nmol)+EKC/D (3 nmol). HP (1 pmol) weakened the analgesic effect of SR142801 (100 pmol)+EKA/B (30 pmol), but HP (100pmol) strengthened the analgesic effect of SR142801 (3 nmol)+EKA/B (3 nmol). These findings may pave the way for a new strategy on investigating the interaction between tachykinins and opioids on pain modulation.

Effects of endokinin A/B, endokinin C/D, and endomorphin-1 on the regulation of mean arterial blood pressure in rats.

Endokinins are four novel human tachykinins, including endokinins A (EKA), B (EKB), C (EKC), and D (EKD). Endokinin A/B (EKA/B) is the common C-terminal decapeptide in EKA and EKB, while endokinin C/D (EKC/D) is the common C-terminal duodecapeptide in EKC and EKD. In this study, we attempted to investigate the interactions between EKA/B, EKC/D, and endomorphin-1 (EM-1) on the depressor effect at peripheral level. The effects of EKA/B produced a U-shaped curve. The maximal effect was caused by 10 nmol/kg. EKC/D and EM-1 showed a dose-dependent relationship. Co-administration of EKA/B (0.1, 1, 10 nmol/kg) with EM-1 produced effects similar to those of EKA/B alone but slightly lower. Co-injection of EKA/B (100 nmol/kg) with EM-1 caused an effect stronger than any separate injection. Co-administration of EKC/D (10 nmol/kg) with EM-1 (30 nmol/kg) caused a depressor effect, which was one of the tradeoffs of EM-1 and EKC/D. Mechanism studies showed that SR140333B could block the depressor effects of EKA/B, EKC/D, EM-1, EKA/B+EM-1, and EKC/D+EM-1; SR48968C could block EM-1, EKA/B, EKC/D, and EKC/D+EM-1 and partially block EKA/B+EM-1; SR142801 could block EM-1, EKC/D, and EKC/D+EM-1 and partially block EKA/B and EKA/B+EM-1; naloxone could block EM-1, EKC/D, and EKC/D+EM-1 and partially block EKA/B and EKA/B+EM-1. Pretreatment with NG-nitro-l-arginine methyl ester partially decreased depressor intensity and half-recovery time of EKA/B and EKC/D.

Synthesis and diuretic activities of pseudoproline-containing analogues of the insect kinin core pentapeptide.

C-2 dimethylated/unmethylated thiazolidine-4-carboxylic acid and C-2 dimethylated oxazolidine-4-carboxylic acid were introduced into the insect kinin core pentapeptide in place of Pro(3) , yielding three new analogues. NMR analysis revealed that the peptide bond of Phe(2) -pseudoproline (ΨPro)(3) is practically 100% in cis conformation in the case of dimethylated pseudoproline-containing analogues, about 50% cis for the thiazolidine-4-carboxylic acid analogue and about 33% cis for the parent Pro(3) peptide. The diuretic activities are consistent with the population of cis conformation of the Phe(2) -ΨPro(3) /Pro(3) peptide bonds, and the results confirm a cis Phe-Pro bond as bioactive conformation.

Effects of Endokinin A/B and Endokinin C/D on the modulation of pain in mice.

Endokinins are novel tachykinins encoded on the human TAC4 and consist of Endokinin A (EKA), B (EKB), C (EKC) and D (EKD). To date, the function of Endokinins in pain processing was not fully understood. Therefore the aim of this study was to investigate the effects of Endokinin A/B (EKA/B, the common C-terminal decapeptide in EKA and EKB) and Endokinin C/D (EKC/D, the common C-terminal duodecapeptide in EKC and EKD) on pain modulation at supraspinal level in mice. Intracerebroventricular (i.c.v.) administration of EKA/B (1, 3, 12, 20nmol/mouse) dose dependently induced potent analgesic effect. This effect could be fully antagonized by SR140333B but not SR48968C or SR142801. Naloxone could also block the analgesic effect, suggesting that this analgesic effect is related to opioid receptors. However, i.c.v. administration of EKA/B (10, 30, 100pmol/mouse) caused hyperalgesic effect significantly, with a "U" shape curve. Interestingly, the hyperalgesic effect induced by EKA/B could be attenuated by SR140333B, SR142801 but not SR48968C. I.c.v. administration of EKC/D (1, 3, 12, 20nmol/mouse) also dose dependently induced analgesic effect, which could not be blocked by SR48968C or SR142801 or naloxone. But to our astonishment, it could be significantly enhanced by SR140333B. More interestingly, the hyperalgesic effect induced by EKA/B could be significantly attenuated by EKC/D. In addition, the analgesic effect induced by co-administration of EKA/B and EKC/D was much less stronger than the effect of either EKA/B or EKC/D.

Effects of Endokinin A/B and Endokinin C/D on the antinociception of Endomorphin-1 in mice.

In our previous study, Endokinin A/B (EKA/B, the common C-terminal decapeptide in Endokinin A and Endokinin B) was found to induce analgesic effect at high dose and nociception at low dose, while Endokinin C/D (EKC/D, the common C-terminal duodecapeptide in Endokinin C and Endokinin D) has analgesic effect only. So in this study an attempt was undertaken to investigate the interaction of EKA/B and EKC/D with Endomorphin-1 (EM-1) on antinociceptive effect at supraspinal level. Results showed that the antinociceptive effect of EM-1 was enhanced by high dose of EKA/B and abolished by low dose of EKA/B, while EKC/D could only enhance the analgesic effect. Mechanism studies showed that EKA/B blocked the antinociception of EM-1 by activating neurokinin-1 receptor (NK(1)), whose specific antagonist, SR140333B could fully block EKA/B-induced attenuation on the analgesic response of EM-1. Surprisingly, EKC/D could also block the same EKA/B-induced attenuation. Taken together, the different effects of EKA/B and EKC/D on the antinociception of EM-1 may pave the way for a new strategy on investigating the interaction between tachykinins and opioids on pain modulation.