Tomohiro Maruyama

Conformational changes and anticoagulant activity of chondroitin sulfate following its O-sulfonation

Chondroitin sulfate from bovine tracheal cartilage, with the basic structure (4-O-sulfo-D-GalpNAc beta-1-->4-D-GlcpA)n, was chemically modified by O-sulfonation. Depending on the reaction conditions, the products showed a different degree of O-sulfonation. A fully O-sulfonated chondroitin sulfate, having no free hydroxyl groups, and a sulfo ester group:disaccharide unit ratio of 4.0 was prepared. This chondroitin sulfate derivative was shown by 1H NMR spectroscopy to have a uronate residue with an altered conformation. Usually, the uronate residue in chondroitin sulfate resides in the 4C1 form. Fully O-sulfonated chondroitin sulfate had an uronate residue in the 1C4 form at 30 degrees C, similar to the preferred conformation of the 2-O-sulfo-iduronate residue most commonly found in heparin. The 2S0 form of the uronate residue was also found in fully O-sulfonated chondroitin sulfate at 60 degrees C. The anti-factor IIa activity of fully O-sulfonated chondroitin sulfate was 40 units/mg. This value is similar to the activities reported for various low-molecular-weight heparins, and substantially higher than those previously reported for partially O-sulfonated chondroitin sulfates having an average sulfate group/disaccharide unit of 2.5 to 3.3. The anti-factor Xa activity of the fully O-sulfonated chondroitin sulfate was 12 units/mg. This value is considerably lower than the activities reported for various low-molecular-weight heparins, consistent with the critical importance of an antithrombin III pentasaccharide binding site for anti-factor Xa activity. These findings suggest that the conformational change of glucuronic acid residue in chondroitin sulfate resulting from its full O-sulfonation can result in enhanced anticoagulant activity, particularly as measured by anti-factor IIa assay.

PREPARATION AND ANTICOAGULANT ACTIVITY OF FULLY O-SULPHONATED GLYCOSAMINOGLYCANS

Glycosaminoglycans including dermatan sulphate, hyaluronan, heparan sulphate and heparin were chemically modified by O-sulphonation. By altering the reaction conditions, products having a different degree of O-sulphonation could be obtained. Glycosaminoglycan derivatives were prepared having no free hydroxyl groups, with sulphoester group/disaccharide unit ratios of 4.0 for dermatan sulphate and hyaluronan, and sulphoester and sulphamide group/disaccharide unit ratios of 4.22 and 4.88 for heparan sulphate and heparin, respectively. 1H NMR spectroscopy showed that the fully O-sulphonated hyaluronan derivative had a glucuronate residue with an altered conformation. Since glycosaminiglycans and their derivatives are often used as anticoagulant/antithrombotic agents, their anti-amidolytic activities were determined. The anti-factor IIa activity of fully O-sulphonated dermatan sulphate, hyaluronan and heparan sulphate ranged from 40 to 80 units/mg, while no anti-factor Xa activity of the fully O-sulphonated glycosaminoglycans was detected. These values are lower than those reported for low-molecular-weight heparins and are consistent with the requirement of an antithrombin III pentasaccharide binding site for anti-factor Xa activity. Interestingly, the anti-factor Xa of heparin is lost by chemical O-sulphonation.

Detection of glycosaminoglycans as a copper(II) complex in high-performance liquid chromatography

Glycosaminoglycans including heparin, heparan sulfate, chondroitin sulfate, dermatan sulfate and hyaluronan were analyzed by high-performance gel filtration chromatography. Detection was achieved at 240 nm based on the formation of copper(II) complex in copper sulfate solution at low pH. Detection of the copper(II)-heparin complex is sensitive, permitting the analysis of as little as 10(-7) g. This method was also successfully applied to the analysis of the chemically derivatized glycosaminoglycans (de-N-acetylated and/or oversulfated chondroitin sulfate) that cannot be depolymerized by enzymes such as heparin and chondroitin lyases.

Assist control for ball catching using high-speed vision on a master-slave robot

In recent years, the demand for robots that can perform various tasks in dangerous environments has increased. Teleoperated robots are more suitable for dangerous environments than autonomous robots. We have developed a master-slave robot system that consists of a lightweight master device and a high-power slave robot and proposed operation assistance methods to improve the dexterity and increase the moving speed. In this paper, we propose a control method for catching a flying ball with a master-slave system. The slave robot is controlled by integrating the operators commands and autonomous visual feedback control so as to track and catch the flying object. The object trajectory and operator motion are predicted by using a Kalman filter. The proposed method was verified by experiment.

Operation assistance using visual feedback with considering human intention on master-slave systems

In the paper, we propose a method for improving maneuverability of master-slave systems. We aim for reproducing human skillfulness and dynamic performance in master-slave robots by using assist control for human operators. In this paper, we focus on a reaching task of a master-slave robot and propose an operation assist algorithm based on visual feedback control. It consists of visual recognition of an object for a slave robot, prediction of operators motion by a particle filter, estimation of a target for grasping, assist control of the reaching motion. Finally, the validity of the proposed method is verified in a master-slave robot system.

Vision-based predictive assist control on master-slave systems

In this paper, we propose a method for improving the maneuverability of master-slave systems. We aim at reproducing human skillfulness and dynamic performance in master-slave robots by using assist control for human operators. In this paper, we tackle a reaching task performed by a master-slave robot and propose an operation assist algorithm based on visual feedback control. The algorithm consists of visual object recognition for a slave robot, prediction of the operators motion by a particle filter, estimation of the operators intention, and operation assistance of the reaching motion. We verified the validity of the proposed system in experiments.