JoVE - Journal of Visualized Experiments
JoVE Visualize
Contact Us
このページは機械翻訳されています。他のページは英語で表示される場合があります。 View in English

既存のテルペンサイクラスの構造,メカニズム,および特異性を明らかにするツールとしての祖先の工学

  • 0School of Engineering Sciences in Chemistry, Biotechnology and Health, Science for Life Laboratory, KTH Royal Institute of Technology, 114 28 Stockholm, Sweden.
Journal of the American Chemical Society +

|

2021年1月26日

PubMedで要約を見る

まとめ

この要約は機械生成です。

関連する概念動画

Thermal and Photochemical Electrocyclic Reactions: Overview 01:26

2.7K

Electrocyclic reactions are reversible reactions. They involve an intramolecular cyclization or ring-opening of a conjugated polyene. Shown below are two examples of electrocyclic reactions. In the first reaction, the formation of the cyclic product is favored. In contrast, in the second reaction, ring-opening is favored due to the high ring strain associated with cyclobutene formation.

Electrocyclic reactions are highly stereospecific. For a substituted polyene, the stereochemical outcome...

Thermal Electrocyclic Reactions: Stereochemistry 01:17

2.3K

The stereochemistry of electrocyclic reactions is strongly influenced by the orbital symmetry of the polyene HOMO. Under thermal conditions, the reaction proceeds via the ground-state HOMO.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.

Conjugated...

Photochemical Electrocyclic Reactions: Stereochemistry 01:26

2.0K

The absorption of UV–visible light by conjugated systems causes the promotion of an electron from the ground state to the excited state. Consequently, photochemical electrocyclic reactions proceed via the excited-state HOMO rather than the ground-state HOMO. Since the ground- and excited-state HOMOs have different symmetries, the stereochemical outcome of electrocyclic reactions depends on the mode of activation; i.e., thermal or photochemical.
Selection Rules: Photochemical Activation

Diels–Alder Reaction Forming Bridged Bicyclic Products: Stereochemistry 01:29

5.0K

Diels–Alder reactions between cyclic dienes locked in an s-cis configuration and dienophiles yield bridged bicyclic products.

Dienophiles with one or more electron-withdrawing substituents form stereochemically different products in which the substituents are oriented in an endo (towards) or exo (away) configuration relative to the double bond.

The endo isomer is formed faster and is the kinetic product. The exo isomer is more stable and is the thermodynamic...

C4 Pathway and CAM 01:27

47.8K

Most plants use the C3 pathway for carbon fixation. However, some plants, such as sugar cane, corn, and cacti that grow in hot conditions, use alternative pathways to fix carbon and conserve energy loss due to photorespiration. Photorespiration is the process that occurs when the oxygen concentration is high. Under such conditions, the rubisco enzyme in the Calvin cycle binds O2 instead of CO2, which halts photosynthesis and consumes energy.
C4 Pathway
The C4 pathway is used by plants such as...

Allosteric Proteins-ATCase 01:19

6.2K

Binding sites linkages can regulate a protein's function.  For example, enzyme activity is often regulated through a feedback mechanism where the end product of the biochemical process serves as an inhibitor.
Aspartate transcarbamoylase (ATCase) is a cytosolic enzyme that catalyzes the condensation of L-aspartate and carbamoyl phosphate to  N-carbamoyl-L-aspartate. This reaction is the first step in pyrimidine biosynthesis. UTP and CTP, the end products of the pyrimidine synthesis...