activated complex

Examples of activated complex in the following topics:

• Transition State Theory

  • The species that is formed during the transition state is known as the activated complex.
  • TST is also referred to as "activated-complex theory," "absolute-rate theory," and "theory of absolute reaction rates."
  • The species that forms during the transition state is a higher-energy species known as the activated complex.
  • The mechanism by which the activated complex breaks apart; it can either be converted into products, or it can "revert" back to reactants.
  • Once the activated complex is formed, it can then continue its transformation into products, or it can revert back to reactants.

• Enzyme Catalysis

  • Enzymes are proteins that are able to lower the activation energy for various biochemical reactions.
  • At the active site, the substrate(s) can form an activated complex at lower energy.
  • This change stabilizes the transition state complex, and thus lowers the activation energy.
  • Electrostatic catalysis: electrostatic attractions between the enzyme and the substrate can stabilize the activated complex.
  • An enzyme catalyzes a biochemical reaction by binding a substrate at the active site.

• Biomolecules

  • Coordination complexes are found in many biomolecules, especially as essential ingredients for the active site of enzymes.
  • Coordination complexes (also called coordination compounds) and transition metals are widespread in nature.
  • The transition metals, particularly zinc and iron, are often key components of enzyme active sites.
  • As with all enzymes, the shape of the active site is crucial.
  • The structure of the active site in carbonic anhydrases is well known from a number of crystal structures.

• Mapping Protein-Protein Interactions

  • In living organisms most of the biological functions are mediated by complex multi-component protein machineries and network activities.
  • The protein complexes formed could be stable (proteins interact for a prolonged period of time) or transient (proteins interact for a brief period of time).
  • The method consists of splitting a yeast transcription factor into its binding domain and activation domain, fusing the binding domain to one protein of interest (the bait) and the activation domain to another protein of interest (the prey), and reconstituting the activity of the transcription factor by bringing the two domains back into physical proximity.
  • If the two proteins do interact the bait recruits the prey to a specific cellular location where it can stimulate a detectable output (e.g., gene activation).
  • Results collected from binary and co-complex experiments are documented into a database.

• Interferons

  • Another function of interferons is to upregulate major histocompatibility complex molecules, MHC I and MHC II, and increase immunoproteasome activity.
  • By interacting with their specific receptors, IFNs activate signal transducer and activator of transcription (STAT) complexes.
  • However, each IFN type can also activate unique STATs.
  • Binding of ISGF3 and other transcriptional complexes activated by IFN signaling to these specific regulatory elements induces transcription of those genes.
  • Type I IFNs further activate p38 mitogen-activated protein kinase (MAP kinase) to induce gene transcription.

• Siderophores

  • The ability to form water soluble Fe3+ complexes is a key component to the active transport of the Fe-siderophore complex across the cellular membrane.
  • The complexes then generally bind to the cellular membrane using cell specific receptors.
  • In areas of low iron, the organism will release yersiniabactin to form Fe3+ complexes.
  • Once the enterobactin-Fe3+ complex arrives intracellularly, it is necessary to remove the Fe3+ from the complex.
  • The iron released from the complex will then be utilized in metabolic processes.

• Metal Cations that Act as Lewis Acids

  • Transition metals can act as Lewis acids by accepting electron pairs from donor Lewis bases to form complex ions.
  • The number of coordinate bonds is known as the complex's coordination number.
  • The product is known as a complex ion, and the study of these ions is known as coordination chemistry.
  • One coordination chemistry's applications is using Lewis bases to modify the activity and selectivity of metal catalysts in order to create useful metal-ligand complexes in biochemistry and medicine.
  • Examples of several metals (V, Mn, Re, Fe, Ir) in coordination complexes with various ligands.

• Immune Complex Autoimmune Reactions

  • An immune complex is formed from the integral binding of an antibody to a soluble antigen and can function as an epitope.
  • An immune complex is formed from the integral binding of an antibody to a soluble antigen.
  • Type III hypersensitivity reactions are immune complex-mediated.
  • Activation of complement primarily results in cleavage of soluble complement proteins forming C5a and C3a, which activate recruitment of PMNs and local mast cell degranulation (requiring the binding of the immune complex onto FcγRIII), resulting in an inflammatory response.
  • An immune complex is formed from the integral binding of an antibody to a soluble antigen.

• Reactions of Alkylidene Complexes

  • The alkylidene complexes described above undergo many interesting and synthetically useful reactions.
  • The next two equations (# 7 & 8) demonstrate the dienophilic activation provided by a Fischer carbene.
  • In most cases the carbene is a stronger activating group than the corresponding ester.

• Electron Transport Chain

  • A prosthetic group is a non-protein molecule required for the activity of a protein.
  • Complex II directly receives FADH2, which does not pass through complex I.
  • Q receives the electrons derived from NADH from complex I and the electrons derived from FADH2 from complex II, including succinate dehydrogenase.
  • This enzyme and FADH2 form a small complex that delivers electrons directly to the electron transport chain, bypassing the first complex.
  • Complex III pumps protons through the membrane and passes its electrons to cytochrome c for transport to the fourth complex of proteins and enzymes.