Related Concept Videos
01:26Thermal and Photochemical Electrocyclic Reactions: Overview
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.
01:26Photochemical Electrocyclic Reactions: Stereochemistry
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
Selection Rules: Photochemical Activation
01:17Thermal Electrocyclic Reactions: Stereochemistry
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.
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.
01:12Cycloaddition Reactions: MO Requirements for Photochemical Activation
Some cycloaddition reactions are activated by heat, while others are initiated by light. For example, a [2 + 2] cycloaddition between two ethylene molecules occurs only in the presence of light. It is photochemically allowed but thermally forbidden.
01:25Deactivation Processes: Jablonski Diagram
Luminescence, the emission of light by a substance that has absorbed energy, is a process that involves the interaction of molecules with light. The energy-level diagram, or Jablonski diagram, is a graphical representation of these interactions, illustrating the various states and transitions a molecule can undergo. In a typical Jablonski diagram, the lowest horizontal line represents the ground-state energy of the molecule, which is usually a singlet state. This state represents the energies...
01:16Olefin Metathesis Polymerization: Ring-Opening Metathesis Polymerization (ROMP)
Ring-opening metathesis polymerization or ROMP involves strained cycloalkenes as starting materials. The mechanism of ROMP proceeds by reacting cycloalkene with Grubbs catalyst to give metallacyclobutane intermediate which undergoes a ring-opening reaction to form new carbene. The new carbene reacts with another molecule of cycloalkene. Repetition of these steps leads to the formation of an unsaturated open-chain polymer product. All these steps are reversible, however, relieving the ring...
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Related Experiment Video
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14:11
Synthesis of pH Dependent Pyrazole, Imidazole, and Isoindolone Dipyrrinone Fluorophores using a Claisen-Schmidt Condensation Approach
Published on: June 10, 2021
Emission control by binary energy transfer processes on oligouridine.
Shuji Ikeda1, Takeshi Kubota, Dan Ohtan Wang
1Advanced Science Institute, RIKEN, Wako, Saitama 351-0198, Japan.
Organic & Biomolecular Chemistry
|August 13, 2011
Summary
Researchers developed fluorescent oligonucleotides using two energy transfer methods for controlled fluorescence. These probes accurately detect complementary RNA in lab tests and living cells.
Area of Science:
- Molecular Biology
- Biochemistry
- Biophysics
Background:
- Fluorescent probes are crucial for detecting nucleic acids.
- Controlling fluorescence emission is key for accurate detection.
- Oligonucleotides offer a versatile platform for probe design.
Purpose of the Study:
- To design and characterize novel fluorescent oligonucleotides.
- To investigate the combined use of excitonic interaction and Förster Resonance Energy Transfer (FRET).
- To demonstrate the utility of these probes for RNA detection in vitro and in cellulo.
Main Methods:
- Synthesis of fluorescently labeled oligonucleotides.
- Characterization of energy transfer processes (excitonic interaction and FRET).
- Hybridization assays with complementary RNA targets.
- Cellular imaging studies to assess probe performance in vivo.
Main Results:
- Successful integration of excitonic interaction and FRET in oligonucleotide probes.
- Demonstrated precise control over fluorescence emission based on hybridization.
- Effective detection of complementary RNA both in vitro and within living cells.
- High sensitivity and specificity observed in biological samples.
Conclusions:
- The designed fluorescent oligonucleotides offer a robust platform for nucleic acid detection.
- The combined energy transfer mechanisms provide enhanced control over probe signaling.
- These probes show significant potential for applications in molecular diagnostics and biological research.