Solution Structure and Dynamics of the I214V Mutant of the Rabbit Prion Protein

Background: The conformational conversion of the host-derived cellular prion protein (PrP C) into the disease-associated scrapie isoform (PrP Sc) is responsible for the pathogenesis of transmissible spongiform encephalopathies (TSEs). Various single-point mutations in PrP C s could cause structural changes and thereby distinctly influence the conformational conversion. Elucidation of the differences between the wild-type rabbit PrP C (RaPrP C) and various mutants would be of great help to understand the ability of RaPrP C to be resistant to TSE agents. Methodology/Principal Findings: We determined the solution structure of the I214V mutant of RaPrP C (91–228) and detected the backbone dynamics of its structured C-terminal domain (121–228). The I214V mutant displays a visible shift of surface charge distribution that may have a potential effect on the binding specificity and affinity with other chaperones. The number of hydrogen bonds declines dramatically. Urea-induced transition experiments reveal an obvious decrease in the conformational stability. Furthermore, the NMR dynamics analysis discloses a significant increase in the backbone flexibility on the pico- to nanosecond time scale, indicative of lower energy barrier for structural rearrangement. Conclusions/Significance: Our results suggest that both the surface charge distribution and the intrinsic backbone flexibility greatly contribute to species barriers for the transmission of TSEs, and thereby provide valuable hints fo

Solution Structure and Dynamics of the I214V Mutant of the Rabbit Prion Protein

Background: The conformational conversion of the host-derived cellular prion protein (PrPC) into the disease-associated scrapie isoform (PrPSc) is responsible for the pathogenesis of transmissible spongiform encephalopathies (TSEs). Various single-point mutations in PrP(C)s could cause structural changes and thereby distinctly influence the conformational conversion. Elucidation of the differences between the wild-type rabbit PrPC (RaPrPC) and various mutants would be of great help to understand the ability of RaPrPC to be resistant to TSE agents. Methodology/Principal Findings: We determined the solution structure of the I214V mutant of RaPrPC (91-228) and detected the backbone dynamics of its structured C-terminal domain (121-228). The I214V mutant displays a visible shift of surface charge distribution that may have a potential effect on the binding specificity and affinity with other chaperones. The number of hydrogen bonds declines dramatically. Urea-induced transition experiments reveal an obvious decrease in the conformational stability. Furthermore, the NMR dynamics analysis discloses a significant increase in the backbone flexibility on the pico- to nanosecond time scale, indicative of lower energy barrier for structural rearrangement. Conclusions/Significance: Our results suggest that both the surface charge distribution and the intrinsic backbone flexibility greatly contribute to species barriers for the transmission of TSEs, and thereby provide valuable hints for understanding the inability of the conformational conversion for RaPrPCNational Natural Science Foundation of China [30730026, 30570352]; National Science & Technology, China [2009ZX09301-001

Nanobubbles influence on BSA adsorption on mica surface

Nanobubbles have been shown to exist at liquid/solid interfaces and have become the focus of research in varied interfacial processes. In the present work, bovine serum albumin (BSA) adsorbed on mica was used as a model system to investigate the effect of nanobubbles on protein adsorption at the liquid/solid interface. The adsorption of BSA on mica in two types of surfaces, with and without nanobubbles, was imaged by means of an atomic force microscope (AFM) in both liquid and air. By comparing the data from the two groups, it has been shown clearly that the adsorption of BSA was indeed influenced by the nanobubbles. Generally, nanobubbles blocked BSA adsorption and resulted in circular hollows on the BSA films on mica

Nano-manipulation of single DNA molecules based on atomic force microscopy

Nano-manipulation of single atoms and molecules is a critical technique in nanoscience and nanotechnology. This paper will focus on the recent development of the manipulation of single DNA molecules based on atomic force microscopy (AFM) in our laboratory. Precise manipulation has been realized including varied manipulating modes such as "cutting", "pushing", "folding", "kneading", "picking up", "dipping", etc. The cutting accuracy is dominated by the size of the AFM tip, which is usually 10 nm or less. Single DNA fragments can be cut and picked up and then amplified by single molecule PCR. Thus positioning isolation and sequencing can be performed.Lu Jun-Hong, Li Hai-Kuo, An Hong-Jie, Wang Guo-Hua, Wang Ying, Li Min -Qian, Zhang Yi, Li Bin and Hu Ju

Acidity-activatable upconversion afterglow luminescence cocktail nanoparticles for ultrasensitive in vivo imaging

Abstract Activatable afterglow luminescence nanoprobes enabling switched “off-on” signals in response to biomarkers have recently emerged to achieve reduced unspecific signals and improved imaging fidelity. However, such nanoprobes always use a biomarker-interrupted energy transfer to obtain an activatable signal, which necessitates a strict distance requisition between a donor and an acceptor moiety (<10 nm) and hence induces low efficiency and non-feasibility. Herein, we report organic upconversion afterglow luminescence cocktail nanoparticles (ALCNs) that instead utilize acidity-manipulated singlet oxygen (1O2) transfer between a donor and an acceptor moiety with enlarged distance and thus possess more efficiency and flexibility to achieve an activatable afterglow signal. After in vitro validation of acidity-activated afterglow luminescence, ALCNs achieve in vivo imaging of 4T1-xenograft subcutaneous tumors in female mice and orthotopic liver tumors in male mice with a high signal-to-noise ratio (SNR). As a representative targeting trial, Bio-ALCNs with biotin modification prove the enhanced targeting ability, sensitivity, and specificity for pulmonary metastasis and subcutaneous tumor imaging via systemic administration of nanoparticles in female mice, which also implies the potential broad utility of ALCNs for tumor imaging with diverse design flexibility. Therefore, this study provides an innovative and general approach for activatable afterglow imaging with better imaging performance than fluorescence imaging

Anti-Inflammatory and Gut Microbiota Modulation Potentials of Flavonoids Extracted from Passiflora foetida Fruits

This study aimed to explore the anti-inflammatory and gut microbiota modulation potentials of flavonoid-rich fraction (PFF) extracted from Passiflora foetida fruits. The results showed that PFF markedly reduced the production of nitric oxide (NO), tumor necrosis factor &alpha; (TNF-&alpha;), and interleukin 6 (IL-6) in LPS-stimulated RAW 264.7 cells. Meanwhile, PFF treatment also effectively decreased the phosphorylation levels of MAPK, PI3K/Akt, and NF-&kappa;B signaling-pathway-related proteins (ERK, JNK, p38, Akt, and p65). Moreover, PFF had an impact on microbial composition and metabolites in a four-stage dynamic simulator of human gut microbiota (BFBL gut model). Specifically, PFF exhibited the growth-promoting ability of several beneficial bacteria, including Bifidobacterium, Enterococcus, Lactobacillus, and Roseburia, and short-chain fatty acid (SCFA) generation ability in gut microbiota. In addition, spectroscopic data revealed that PFF mainly contained five flavonoid compounds, which may be bioactive compounds with anti-inflammatory and gut microbiota modulation potentials. Therefore, PFF could be utilized as a natural anti-inflammatory agent or supplement to health products

Immunological activity and gut microbiota modulation of pectin from kiwano (Cucumis metuliferus) peels

This article belongs to the Special Issue Analysis, Detection Technology and Safety Risk Assessment of Food Contaminants.For developing the recycling of fruit by-products from kiwano, a polysaccharide was extracted from kiwano (Cucumis metuliferus) peels, namely Cucumis metuliferus peels polysaccharide (CMPP), with the aim of investigating the potential beneficial effects. The composition of polysaccharides was analyzed by chemical methods. RAW264.7 macrophages cells and the microbiota dynamics simulator (BFBL gut model) were used for in vitro study. The result showed that CMPP mainly consists of glucuronic acid, arabinose, galactose and rhamnose. By intervening with RAW264.7 cells, CMPP promoted cell proliferation and showed immune-enhancing activity, which significantly (p < 0.05) induced the release of nitric oxide (NO), tumor necrosis factor α (TNF-α) and interleukin 6 (IL-6) at a concentration of 50 μg/mL. In addition, CMPP had an impact on the composition of the gut bacteria, increasing the growth of Akkermansia, Bacteroides, Bifidobacterium, Feacalibacterium, and Roseburia. During the intake period, acetic, butyric and propionic acids were all increased, especially (p < 0.05) in the descending colon. Moreover, a decrease in ammonia concentration (10.17 ± 0.50 mM in the ascending colon, 13.21 ± 1.54 mM in the transverse colon and 13.62 ± 0.45 mM in the descending colon, respectively) was observed. In summary, CMPP can be considered as a pectin, showed immunological activity and function of gut microbiota modulation. This study could be the scientific basis of developing kiwano peels as beneficial to human health.This research was funded by the Lingnan Modern Agricultural Science and Technology Guangdong Laboratory independent scientific research project (NZ2021032), the Key Area R&D Program of Guangdong Province (NO. 2019B020211002), the Guangdong Province Universities and Colleges Pearl River Scholar Funded Scheme (2017), and the International Cooperation Program of SCAU (NO. 2019SCAUGH03). This research was funded by the Spanish Ministry of Science and Innovation (grant numbers AGL2016-75951-R and PID2019-106071RB-I00)Peer reviewe

An activatable NIR-II fluorescent reporter for in vivo imaging of amyloid-β plaques

Fluorescence imaging in the second near-infrared (NIR-II) window holds great promise for in vivo visualization of amyloid-β (Aβ) pathology, which can facilitate characterization and deep understanding of Alzheimer's disease (AD); however, it has been rarely exploited. Herein, we report the development of NIR-II fluorescent reporters with a donor-π-acceptor (D-π-A) architecture for specific detection of Aβ plaques in AD-model mice. Among all the designed probes, DMP2 exhibits the highest affinity to Aβ fibrils and can specifically activate its NIR-II fluorescence after binding to Aβ fibrils via suppressed twisted intramolecular charge transfer (TICT) effect. With suitable lipophilicity for ideal blood-brain barrier (BBB) penetrability and deep-tissue penetration of NIR-II fluorescence, DMP2 possesses specific detection of Aβ plaques in in vivo AD-model mice. Thus, this study presents a potential agent for non-invasive imaging of Aβ plaques and deep deciphering of AD progression.Ministry of Education (MOE)National Research Foundation (NRF)The authors thank the financial support from National Natural Science Foundation of China (22106115, 81901803, and 22274107), Jiangsu Specially Appointed Professorship, Natural Science Foundation of Jiangsu Province (BK20190830and BK20190811), Leading Talents of Innovation and Entrepreneurship of Gusu (ZXL2021457),and Soochow Technological Project(SYS2020082).K.P. thanks Singapore National Research Foundation(NRF)(NRF-NRFI07-2021-0005), and Singapore Ministry of Education, Academic Research Fund Tier 1 (2019-T1-002-045, RG125/19, RT05/20), Academic Research Fund Tier 2 (MOE-T2EP30220-0010; MOE-T2EP30221-0004), for the financial support