Studies of the structure of potassium channel KcsA in the open conformation and the effect of anionic lipids on channel inactivation

Membrane proteins play a vital role in cellular processes. In this thesis, we use KcsA, a prokaryotic potassium channel, as a model to investigate the gating mechanism of ion channels and the effect of anionic lipids on the channel activity using solid-state NMR spectroscopy. KcsA activity is known to be highly dependent on the presence of negatively charged lipids. Multiple crystal structures combined with biochemistry assays suggest that KcsA is co-purified with anionic lipids with phosphatidylglycerol headgroup. Here, we identified this specifically bound, isotopically labeled lipid in the protein 13C-13C correlation spectra. Our results reveal that the lipid cross peaks show stronger intensity when the channel is in the inactivated state compared to the activated state, which indicates a stronger protein-lipid interaction when KcsA is inactivated. In addition, our data shows that including anionic lipids into proteoliposomes leads to a weaker potassium ion affinity at the selectivity filter. Considering ion loss as a model of inactivation, our results suggest anionic lipids promote channel inactivation. However, the surface charge is not the only physical parameter that regulates channel gating or conformational preference. We found that the channel adapted to different conformations when reconstituted into liposome either made of DOPC or DOPE, two zwitterionic lipids. Also, we were able to stabilize the open-conformation of KcsA in 3:1 DOPE/DOPG liposome at pH 4.0 and acquired several multi-dimensional solid-state NMR experiments for site-specific resonance assignments. This is the first time that we obtain wild-type full-length KcsA structural information on the transient state. The structure is not only important for understanding channel gating, but can also serve as a homology model for investigating drug binding with more complicated potassium channels such as human voltage gated channel (hERG)

Tea consumption, oxidative stress, and breast cancer risk

Purpose: Oxidative stress, which features the imbalance between reactive oxygen species and antioxidant defenses, is associated with carcinogenesis. Tea contains natural antioxidants and has anti-tumor properties. However, limited epidemiologic studies investigated the association between tea and oxidative stress. Previous epidemiologic studies investigating tea and breast cancer risk have not addressed the potential for associations to vary by breast cancer subtype. Methods: The Sister Study is a nationwide cohort study that enrolled women across the US and Puerto Rico from 2003-2009. In aim 1, we included 889 premenopausal women from a nested case-control study within the Sister Study and investigated associations between black or green tea and oxidative stress which was measured by urinary F2-isoprostane (F2-IsoP) and a primary metabolite, 2,3-dinor-5,6-dihydro-15-F2t-isoprostane (15-F2t-IsoP-M). In aim 2, we investigated the association between black or green tea and breast cancer risk in the full cohort of 49,214 women. The analysis addressed variation by estrogen receptor (ER) status and other biologically important factors. Results: (Aim 1) We observed green tea was not associated with urinary F2-IsoP and 15-F2t-IsoP-M. Black tea was not associated with urinary F2-IsoP. However, drinking at least 5 cups of black tea per week (compared to 0 cup/week) was associated with a higher level of urinary 15-F2t-IsoP-M (geometric mean difference (GMD)=0.09, 95% CI 0.01, 0.17). Additionally adjusting for caffeine intake attenuated the association towards null (GMD=0.07, 95% CI -0.02, 0.16). (Aim 2) A total of 3,044 breast cancer patients were diagnosed from 49,214 participants. High-level black (hazard ratio (HR)=0.86, 95% CI 0.76, 0.98, ≥5 compared to 0 cups/week) and green tea (HR=0.84, 95% CI 0.73, 0.97, ≥5 compared to 0 cups/week) consumption were associated with a lower breast cancer risk. Both black and green tea consumption were inversely associated with ER+ breast cancer risk. Associations with ER- breast cancer risk were similarly inverse but non-significant. Conclusions: Contrary to previous experimental and clinical studies, we did not find an inverse association between black or green tea and oxidative stress. However, drinking at least 5 cups of black or green tea per week (compared to 0) was associated with a lower breast cancer risk.Doctor of Philosoph

Boeravinone B promotes fracture healing in ovariectomyinduced osteoporotic rats via the regulation of NF-κB p65/IκB-α/SIRT-1 signaling pathway

Purpose: To investigate the fracture-healing effect of boeravinone B in ovariectomy-induced (OVX) osteoporotic rats. Methods: Adult female Wistar rats (n = 30) were ovariectomized and after three months, the unilateral cross-tibial fractures were fixed with intramedullary nails. The rats were then randomly assigned to three groups of 10 rats each: normal control group, OVX group and 100 mg/kg body weight boeravinone B group. Boeravinone B was orally administered for a period of 5 weeks. The effect of boeravinone B on indices of bone formation and resorption was assessed. Levels of inflammatory cytokines including tumor necrosis factor- α (TNF-α) and interleukin-1β (IL-1β) were determined using enzyme-linked immunosorbent assay (ELISA). Western blotting was used to determine the expression levels of NF-κB p65, IкB-α and SIRT1 proteins. Results: There were significant increases in the activities of tartrate-resistant acid phosphatase (TRAP) and alkaline phosphatase (ALP), and collagen type I fragment (CTX) level and serum osteocalcin (OC) of OVX group, when compared with normal control group (p < 0.05). However, treatment with boeravinone B significantly reduced the activities and levels of these parameters, relative to OVX group (p < 0.05). The levels of TNF-α and IL-1β significantly increased in OVX group, relative normal control group, but were significantly lower following treatment with boeravinone B (p < 0.05). Bone mineral content (BMC) was not significantly altered in OVX and boeravinone B-treated groups, when compared with normal control group (p > 0.05). There was significant reduction in bone mineral density (BMD) of OVX group relative to normal control group (p < 0.05). However, treatment with boeravinone B significantly increased the BMD, when compared with OVX group (p < 0.05). After Week 5 of treatment, boeravinone B significantly enhanced bone remodeling and formation of callus. Treatment with boeravinone B significantly reduced the expression levels of NF-κB p65 and IκB-α proteins, and significantly upregulated the expression of SIRT-1 (p < 0.05). Conclusion: The results obtained in this study suggest that boeravinone B promotes the healing of fracture caused by osteoporosis via a mechanism involving NF-κB p65/IκB-α/SIRT-1 signaling pathway

Expressing metaphorically, writing creatively: Metaphor identification for creativity assessment

Metaphor, which can implicitly express profound meanings and emotions, is a unique writing technique frequently used in human language. In writing, meaningful metaphorical expressions can enhance the literariness and creativity of texts. Therefore, the usage of metaphor is a significant impact factor when assessing the creativity and literariness of writing. However, little to no automatic writing assessment system considers metaphorical expressions when giving the score of creativity. For improving the accuracy of automatic writing assessment, this paper proposes a novel creativity assessment model that imports a token-level metaphor identification method to extract metaphors as the indicators for creativity scoring. The experimental results show that our model can accurately assess the creativity of different texts with precise metaphor identification. To the best of our knowledge, we are the first to apply automatic metaphor identification to assess writing creativity. Moreover, identifying features (e.g., metaphors) that influence writing creativity using computational approaches can offer fair and reliable assessment methods for educational settings

Apparent emotional expression explains the effects of head posture on perceived trustworthiness and dominance, but a measure of facial width does not

This research was supported by grants from the National Natural Science Foundation of China (No. 61602079; No.61632011) and the Humanity and Social Science Youth Foundation of Ministry of Education of China (No. 16YJCZH141).Interpreting the personality and the disposition of people is important for social interaction. Both emotional expression and facial width are known to affect personality perception. Moreover, both the apparent emotional expression and the apparent width-to-height ratio of the face change with head tilt. We investigated how head tilt affects judgements of trustworthiness and dominance and whether such trait judgements reflect apparent emotion or facial width. Sixty-seven participants rated the dominance, emotion, and trustworthiness of 24 faces posing with different head tilts while maintaining eye gaze at the camera. Both the 30° up and 20° down head postures were perceived as less trustworthy and more dominant (less submissive) than the head-level posture. Change in perceived trustworthiness and submissiveness with head tilt correlated with change in apparent emotional positivity but not change in facial width. Hence, our analysis suggests that apparent emotional expression provides a better explanation of perceived trustworthiness and dominance compared with cues to facial structure.PostprintPeer reviewe

Telling the whole story : a manually annotated Chinese dataset for the analysis of humor in jokes

Humor plays important role in human communication, which makes it important problem for natural language processing. Prior work on the analysis of humor focuses on whether text is humorous or not, or the degree of funniness, but this is insufficient to explain why it is funny. We therefore create a dataset on humor with 9,123 manually annotated jokes in Chinese. We propose a novel annotation scheme to give scenarios of how humor arises in text. Specifically, our annotations of linguistic humor not only contain the degree of funniness, like previous work, but they also contain key words that trigger humor as well as character relationship, scene, and humor categories. We report reasonable agreement between annotators. We also conduct an analysis and exploration of the dataset. To the best of our knowledge, we are the first to approach humor annotation for exploring the underlying mechanism of the use of humor, which may contribute to a significantly deeper analysis of humor. We also contribute with a scarce and valuable dataset, which we will release publicly. © 2019 Association for Computational Linguistic