Coupling is a phenomenon in which other reactions are accompanied by chemometrics when a chemical reaction occurs.It is mainly used in the following three situations:
[1] Coupling of oxidation and reduction.When the electron donor AH2 is oxidized to A, the electron acceptor B must be reduced to BH2. At this time, the two reactions are called coupling.For example, glycerol 3-phosphate in alcohol fermentationaldehydeDehydrogenation and reduction of acetaldehyde are coupled by two dehydrogenases in the medium of NAD+.
Coupling reaction, also known as coupling reaction, coupling reaction and oxidative coupling, is a process in which two organic chemical units (moieties) carry out a certain chemical reaction to obtain an organic molecule. The chemical reaction here includes the reaction between Grinard reagent and electrophile, the reaction between lithium reagent and electrophile,The electrophilic and nucleophilic reactions (Diazo, Addition-Elimination) on the aromatic ring, as well as the Wutz reaction in the presence of sodium, because the meaning of coupling reaction is too broad, generally an attribute should be added in front of it. Moreover, this is a relatively unprofessional termIn the narrow sense, coupling reaction involves the carbon carbon bond formation reaction of organometallic catalysts. According to different types, it can be divided into cross coupling reaction and self coupling reaction.During coupling reactionAcid-base propertyIt is very important.commonlyDiazonium saltAndPhenolsThe coupling reaction ofmediumIn.Under this condition, phenol forms phenoxy anion to make aromatic ringElectronic cloudThe increase of density is beneficial to the coupling reaction.Diazonium saltThe coupling reaction with aromatic amine is in neutral or weak acidmediumIn.Under these conditions, the existence of aromatic amine in the form of free amine increases the electron cloud density of aromatic ring, which is conducive to the coupling reaction.If the solution is too acidic, the amine becomes an ammonium salt, which reduces the electron cloud density of the aromatic ring and is not conducive to the coupling reactionDiazonium saltIn terms of properties, the strong alkaline medium will transform the diazonium salt into other compounds that cannot undergo coupling reaction.Azo compoundIt is a kind of colored compounds, some of which can be directly used as dyes orindicator。stayOrganic analysisThe color produced by coupling reaction is often used to identifyphenolOr aromatic amine structure.
Common coupling reactions include:
Reaction name - year - reactant A - reactant B - type - catalyst - note
Wurtz reaction 1855 R-X sp³Self coupling Na
Glaser coupling reaction 1869 R-X sp self coupling Cu
Ullmann reaction 1901 R-X sp²Self coupling Cu
Gomberg Bachmann reaction 1924 R-N2X sp²Self coupling with alkali as medium
Cadiot Chodkiewicz Coupling Reaction 1957 Alkyne sp R-X sp Cross coupling Cu in Alkali Medium
Excitation contraction coupling is an intermediary process that links electrical excitation process with mechanical contraction.The mediators are calcium ions, and the structural basis isTriple pipeStructure.
process
1. The action potential of sarcolemma is transmitted to the deep muscle cells along the transverse tube and activates the L-type calcium channel on the triple tube.
2. Alteration of L-type calcium channel or inward flow of calcium ions → activation of terminal pool RYR → release of calcium ions → increase of calcium ion concentration in cytoplasm nearly 100 times → binding with troponin → muscle contraction.
3. The increase of intracellular calcium ion concentration activates the calcium pump on the sarcoplasmic reticulum → recovers calcium ion → decreases calcium ion concentration → muscle relaxation.
Social science
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analysis
There is also a theory of cross coupling in the field of social science.At this time, it often means to go along with each other.
Network Communications
Network communication protocolSCTP (STREAM CONTROL TRANSMISSION PROTOCOLtransport protocol）Incoupling: A correspondence between two SCTP endpoints. It contains two SCTP endpoints and protocol status information, including verification labels and transmission sequence numbers. A coupling can be uniquely identified by the SCTP endpoint using the coupling with the transmission address. At any time, there will be no more than one coupling between two SCTP endpoints.
SCTP coupling is defined by the transmission addresses of two SCTP endpoints. When SCTP is running on the IP, the transmission address is defined by the combination of the IP address and the SCTP port number. Therefore, a SCTP coupling can be uniquely identified by defining four parameters, namely, the local IP address, the local SCTP port number, the peer IP address, and the peer SCTP port number.A SCTP coupling can be regarded as an M2UA link, M3UA link, IUA link, H.248 link or BICC link.
Stream is a characteristic term of SCTP protocol. Stream in SCTP coupling is used to indicate the sequence of user messages that need to be submitted to the high-level protocol in order. Messages in the same stream need to be submitted in its order.Strictly speaking, "flow" is a one-way logical channel from one endpoint to another in an SCTP coupling.
An SCTP coupling is composed of multiple one-way flows. Each flow is relatively independent and identified by a flow ID. Each flow can send data independently without being affected by other flows.A SCTP coupling can contain multiple streams. The number of available streams is determined by both endpoints through negotiation when establishing SCTP coupling, but a stream can only belong to one SCTP coupling.
Figure 2 SCTP Coupling Relationship Diagram
After understanding the above concept of SCTP coupling, we found that coupling is actually equivalent to a pair of pen pals in life, and this pair of pen pals is equivalent to two SCTP endpoints, forming a tacit relationship through letter communication.To communicate between the pen pals, you need to know the other party's address, zip code, name and telephone number. Through these information, you can uniquely identify the pen pals.The channel for sending letters between the pen pals is equivalent to a stream. Each letter is sent in sequence, one after another, and the first sent is received first. The rules for sending letters are determined by both pen pals through negotiation, as shown in Figure 2.
