A highly regio- and diastereoselective TiCl4-mediated vinylogous Mukaiyama aldol reaction using the chiral vinylketene silyl N,O-acetal has been developed. The present vinylogous Mukaiyama aldol reaction provides a unique and effective means of controlling remote asymmetric induction. The methyl group at the alpha-position is important in achieving a high level of stereoselectivity. From a synthetic point of view, this methodology can provide a one-step construction of delta-hydroxy-alpha,gamma-dimethyl-alpha,beta-unsaturated carbonyl unit that is seen in many natural polyketide products.
Novel antithrombin molecules were identified from the ixodidae tick, Haemaphysalis longicornis. These molecules, named madanin 1 and 2, are 7-kDa proteins and show no significant similarities to any previously identified proteins. Assays using human plasma showed that madanin 1 and 2 dose-dependently prolonged both activated partial thromboplastin time and prothrombin time, indicating that they inhibit both the intrinsic and extrinsic pathways. Direct binding assay by surface plasmon resonance measurement demonstrated that madanin 1 and 2 specifically interacted with thrombin. Furthermore, it was clearly shown that madanin 1 and 2 inhibited conversion of fibrinogen into fibrin by thrombin, thrombin-catalyzed activation of factor V and factor VIII, and thrombin-induced aggregation of platelets without affecting thrombin amidolytic activity. These results suggest that madanin 1 and 2 bind to the anionbinding exosite 1 on the thrombin molecule, but not to the active cleft, and interfere with the association of fibrinogen, factor V, factor VIII and thrombin receptor on platelets with an anion-binding exosite 1. They appear to be exosite 1-directed competitive inhibitors.Keywords: anticoagulant; Haemaphysalis longicornis; salivary gland; thrombin inhibitor; tick.Thrombin has various physiological functions and plays important roles in hemostasis. For example, in the final step of blood clot formation, thrombin converts soluble fibrinogen into fibrin and subsequently triggers cross-linking between fibrin monomers by activating factor XIII [1]. It also amplifies its own generation by activating nonenzymatic cofactors V and VIII as well as factor XI [2,3]. Conversely, it suppresses its own generation by activating protein C [4], which inactivates factor Va and factor VIIIa together with protein S [5], when bound to the endothelial membrane receptor thrombomodulin. In addition, thrombin induces platelet aggregation via proteolytic activation of G-protein-coupled protease-activated receptors (PARs) [6,7]. Specific interactions of thrombin with these substrates, cofactors, and receptors involve not only the catalytic site and the primary binding pocket, but also secondary recognition sites, termed anion-binding exosite 1 and 2. Anion-binding exosite 1 interacts with negatively charged domains on fibrinogen [8], PARs [6,7,9], and thrombomodulin [10,11]. Anion-binding exosite 2 interacts with heparin [12], promoting inhibition of thrombin by antithrombin III [13] and heparin cofactor II [14]. Furthermore, both exosites are involved in the recognition of factor V and factor VIII by thrombin [15].The salivary glands of blood-sucking animals, such as leeches, insects, and ticks, contain various anticoagulants [16]. These substances inhibit the host hemostatic response so that the blood-sucking organism can feed smoothly on host blood. The best known anticoagulant identified from bloodsucking organisms is hirudin, a highly specific thrombin inhibitor, isolated from the medical leech, Hirudo medicinalis [17]. It interacts with tw...
BackgroundThere is a dearth of sleep questionnaires with few items and confirmed reliability and validity that can be used for the early detection of sleep problems in children. The aim of this study was to develop a questionnaire with few items and assess its reliability and validity in both children at high risk of sleep disorders and a community population.MethodsData for analysis were derived from two populations targeted by the Children’s Sleep Habits Questionnaire (CSHQ): 178 children attending elementary school and 432 children who visited a pediatric psychiatric hospital (aged 6–12 years). The new questionnaire was constructed as a subset of the CSHQ.ResultsThe newly developed short version of the sleep questionnaire for children (19 items) had an acceptable internal consistency (0.65). Using the cutoff value of the CSHQ, the total score of the new questionnaire was confirmed to have discriminant validity (27.2 ± 3.9 vs. 22.0 ± 2.1, p < 0.001) and yielded a sensitivity of 0.83 and specificity of 0.78 by receiver operator characteristic curve analysis. Total score of the new questionnaire was significantly correlated with total score (r = 0.81, p < 0.001) and each subscale score (r = 0.29–0.65, p < 0.001) of the CSHQ.ConclusionsThe new questionnaire demonstrated an adequate reliability and validity in both high-risk children and a community population, as well as similar screening ability to the CSHQ. It could thus be a convenient instrument to detect sleep problems in children.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.