Explanation by a putative triester-like mechanism for the thio effects and Mn2+ rescues in reactions catalyzed by a hammerhead ribozyme

AbstractDivalent metal ion-dependent hammerhead ribozymes can cleave any RNA with a NUX triplet, wherein the N can be any residue and X can be C, U or A. In recent literature on the mechanism of action of hammerhead ribozymes, one important role of divalent metal ions is generally suggested to be an electrophilic catalyst by directly coordinating with the pro-Rp oxygen of the scissile phosphate to stabilize the transition state. This proposal was made on the basis of thio effects and the proposed electrophilic catalyst is very attractive as an explanation for the catalytic activity of metalloenzymes. Reexamination of thio effects with substrates having a GUA triplet at the cleavage site shows that, in agreement with the previous finding, the cleavage rate, in the presence of Mg2+ ions, is significantly reduced in the case of the phosphorothioate substrate (RpS), wherein the pro-Rp oxygen at the scissile phosphate is replaced by sulfur, while the cleavage rate is reduced to a much lesser extent for the other isomer (SpS), wherein the pro-Sp oxygen at the scissile phosphate is replaced by sulfur. However, more careful examination of the rescue ability of Mn2+ ions with these isomers demonstrates that more thiophilic Mn2+ ions rescue the reaction not only with the RpS isomer but also with the SpS isomer and, importantly, to a greater extent for the SpS isomer. These results argue against the previous conclusion that a metal ion is directly coordinating with the pro-Rp oxygen of the scissile phosphate to stabilize the transition state. In this paper we try to elucidate the possible origin of the thio effects and propose a `triester-like' mechanism in reactions catalyzed by hammerhead ribozymes

Towards the assignment for the 41S04 ^1S_0 meson nonet

The strong decays of the $\pi(2070)$, $\eta(2010)$, $\eta(2100)$, $\eta(2190)$, and $\eta(2225)$ as the $4 ^1S_0$ quark-antiquark states are investigated in the framework of the $^3P_0$ meson decay model. It is found that the $\pi(2070)$, $\eta(2100)$, and $\eta(2225)$ appear to be the convincing $4 ^1S_0$ $q\bar{q}$ states while the assignment of the $\eta(2010)$ and $\eta(2190)$ as the $4 ^1S_0$ isoscalar states is not favored by their widths. In the presence of the $\pi(2070)$, $\eta(2100)$, and $\eta(2225)$ being the members of the $4 ^1S_0$ meson nonet, the $4 ^1S_0$ kaon is phenomenologically determined to has a mass of about 2153 MeV. The width of this unobserved kaon is expected to be about 197 MeV in the $^3P_0$ decay model.Comment: 15 pages, 5 figures, version accepted for publication in Physical Review

Boolean Game on Scale-free Networks

Inspired by the local minority game, we propose a network Boolean game and investigate its dynamical properties on scale-free networks. The system can self-organize to a stable state with better performance than random choice game, although only the local information is available to the agent. By introducing the heterogeneity of local interactions, we find the system has the best performance when each agent's interaction frequency is linear correlated with its information capacity. Generally, the agents with more information gain more than those with less information, while in the optimal case, each agent almost has the same average profit. In addition, we investigate the role of irrational factor and find an interesting symmetrical behavior.Comment: 12 pages and 6 figure

Polycystic ovary syndrome in patients with epilepsy: A study in 102 Chinese women

AbstractPurposeThe incidence of polycystic ovary syndrome (PCOS) increases in women with epilepsy (WWE), which appears to vary with ethnicity. This study was conducted to determine the incidence and risk factors of PCOS in Chinese WWE.MethodsThe study was carried out in 102 of 139 Chinese WWE at reproductive ages, with 32 receiving valproic acid (VPA), 40 receiving other antiepileptic drugs (AEDs), and 30 without AEDs therapy. PCOS was defined as having 2 or more of the following components: polycystic ovaries, hyperandrogenism, and amenorrhoea or oligomenorrhoea (a/oligomenorrhoea).ResultsOne or more isolated components of PCOS were found in 56 (54.9%) patients, with 29 (28.4%) having polycystic ovaries, 20 (19.6%) with a/oligomenorrhea, 7 (6.9%) with hyperandrogenism, and 13 (12.7%) with defined PCOS. Their average age at the start of seizure was 13.8±6.5years, younger than that of patients without these disorders (16.9±8.6years, p<0.05). VPA therapy increased the incidence of PCOS (11/32, 34.4%), in addition to increased blood levels of testosterone and luteinizing hormone (LH) as well as LH to FSH (follicle-stimulating hormone) ratio. No significant relationship was found between the incidence of PCOS and the type, duration, or frequency of seizures in these WWE.ConclusionThere is an increased incidence of PCOS in Chinese WWE at reproductive ages, by more than 2 times of that in the general population. Risk factors include seizures starting at a young age and VPA therapy

The Value of Agricultural Cultural Heritage in Rural Revitalization

The essence of rural revitalization is cultural consciousness and it is a process of cultural consciousness towards cultural self-determination. In rural revitalization, the “dialogue and participation” of rural subjects is the only way. Rural subjects are closely related to agricultural cultural heritage and rural revitalization. Agricultural cultural heritage not only maintains the diversity of agricultural culture, but it also provides economic, cultural, product and ecological services to rural subjects for thousands of years. For this reason, enhancing the cultural consciousness of rural subjects, innovating and using agricultural cultural heritage contribute to the effective promotion of rural revitalization