Abstract: Use of a stereoselective transaminase in the asymmetric synthesis of a chiral amine. In particular, provided is use of a polypeptide in the production of a chiral amine or a downstream product using a chiral amine as a precursor. Further provided is a method for producing a chiral amine, comprising culturing a strain expressing the polypeptide so as to obtain a chiral amine. Further provided are novel prochiral compounds, a chiral amine production strain and a method for constructing the chiral amine production strain. The stereoselective transaminase has a broad substrate spectrum and thus has a broad application potential in the preparation of a chiral amine.

Abstract: Embodiments of the present invention provide a method, an apparatus, and a system for providing a network traversing service. A resource management center sends a network traversing tunnel resource creating instruction to a secure traversing server according to a received network traversing tunnel resource leasing request sent by a management server of a carrier. After the secure traversing server creates a network traversing tunnel resource, the information of the network traversing tunnel resource is sent to the management server of the carrier through the resource management center. The information of the network traversing tunnel resource includes virtual access point information and service channel information. Thus, the management server of the carrier can provide a network traversing service for a terminal according to the virtual access point information and the service channel information. Network expandability of the carrier and reliability of network traversing can be improved by using the method.

Abstract: Embodiments of the present invention provide a method, an apparatus, and a network system for a terminal to traverse a private network to communicate with a server in an IMS core network. The method includes: the terminal sets a source address of service data to be sent as a virtual IP address, sets a destination address of the service data to be sent as an address of an internal network server, and obtains a first service packet, where the virtual IP address is an address allocated by the IMS core network to the terminal, encapsulate the first service packet into a first tunnel packet, and send the first tunnel packet to the security tunnel gateway over a VPN tunnel between the terminal and a security tunnel gateway, then the security tunnel gateway sends the first service packet in the first tunnel packet to the internal network server.

Abstract: Embodiments of the present invention provide an Internet Protocol multimedia subsystem network, and a data transmission method and apparatus, which are used in the field of communications technologies. The data transmission method which is used in the IMS includes: performing tunnel encapsulation for an RTP packet to obtain a tunnel packet, where the tunnel packet includes a record unit, and a plurality of RTP packets are encapsulated in each record unit; and sending the tunnel packet to a peer end over a tunnel connected to the peer end. According to the embodiments of the present invention, the additional bandwidth caused by tunnel encapsulation is reduced, the bandwidth of a single packet is lowered, and the user experience and service access capabilities are improved.

Abstract: Embodiments of the present invention provide a method, an apparatus, and a network system for a terminal to traverse a private network to communicate with a server in an IMS core network. The method includes: the terminal sets a source address of service data to be sent as a virtual IP address, sets a destination address of the service data to be sent as an address of an internal network server, and obtains a first service packet, where the virtual IP address is an address allocated by the IMS core network to the terminal, encapsulate the first service packet into a first tunnel packet, and send the first tunnel packet to the security tunnel gateway over a VPN tunnel between the terminal and a security tunnel gateway, then the security tunnel gateway sends the first service packet in the first tunnel packet to the internal network server.

Abstract: Embodiments of the present invention provide a method, an apparatus, and a network system for a terminal to traverse a private network to communicate with a server in an IMS core network. The method includes: the terminal sets a source address of service data to be sent as a virtual IP address, sets a destination address of the service data to be sent as an address of an internal network server, and obtains a first service packet, where the virtual IP address is an address allocated by the IMS core network to the terminal, encapsulate the first service packet into a first tunnel packet, and send the first tunnel packet to the security tunnel gateway over a VPN tunnel between the terminal and a security tunnel gateway, then the security tunnel gateway sends the first service packet in the first tunnel packet to the internal network server.

Abstract: Embodiments of the present invention provide a method, an apparatus, and a system for providing a network traversing service. A resource management center sends a network traversing tunnel resource creating instruction to a secure traversing server according to a received network traversing tunnel resource leasing request sent by a management server of a carrier. After the secure traversing server creates a network traversing tunnel resource, the information of the network traversing tunnel resource is sent to the management server of the carrier through the resource management center. The information of the network traversing tunnel resource includes virtual access point information and service channel information. Thus, the management server of the carrier can provide a network traversing service for a terminal according to the virtual access point information and the service channel information. Network expandability of the carrier and reliability of network traversing can be improved by using the method.