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논문입니다,,다소 길어요,,
번역을 해야 되는데,,도저히 실력이 딸리네요,,
도움주시면 감사하겠습니다,,
Current coating strategies are mediated either by chemical exchange or hydrophobic–hydrophobic interaction. Alivisatos and Nie and their co-workers were the first groups to use chemical exchange for modifying the surface chemistry of Qdots.[14,15] In the chemical-exchange method, a bifunctional molecule, such as mercaptoacetic acid (MAA), competes with TOPO (or another organic stabilizer) for binding to a metal atom on the Qdot surface. With excess bifunctional molecules in solution, the thiol functional groups (from the MAA) outcompete the phosphonic oxides (from the TOPO) for binding onto the metal atoms. If the bifunctional molecules contain a polar functional group that is opposite to the thiol functional group, the Qdots become highly polar and soluble in aqueous solvents. Unfortunately, the disadvantages of this technique are rapid flocculation and decrease in fluorescence quantum yield of the Qdots. Libchaber and Wu and their co-workers were the first groups to use the hydrophobic–hydrophobic interactions to water-solubilize Qdots.[50,51] With this method,an amphiphilic molecule, such as 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(poly(ethylene glycol))-2000], interacts with a TOPO molecule through hydrophobic– hydrophobic interactions on the Qdot surface. The amphiphilic molecule can then be crosslinked to prevent desorption from the surface. The Qdots become polar because of the protruding polar functional groups. Disadvantages of this technique are the procedural complexity of the method, the highcost of coating reagents, and an increase in the overall size of the Qdots after coating. For most biomedical applications, a mechanism to attach biorecognition molecules (e.g., oligonucleotides, antibodies, or peptides) onto the Qdot surface is needed. The additional purpose of the coating molecule on the Qdots surface (besidesimproving the polarity) is to provide organic functional groups (–COOH, NH3) for conjugation to biorecognition
molecules. These groups permit the linkage of biorecognition molecules with Qdots via the popular EDC (1-ethyl-3-(3-dimethylamino propyl)carbodiimide) assisted crosslinking method.[15,51] In this reaction, the carboxylic acid functional groups on the surface of the Qdots can covalently couple to primary amino groups on proteins or oligonucleotides. An amide bond joins these two entities. A drawback of this techniqueis that EDC-mediated conjugation can lead to aggregation of Qdots if the Qdot-to-protein-to-EDC concentrations are not optimized. As a result, several groups have developed other strategies to coat Qdots with biorecognition molecules.
Akerman et al. used a chemical exchange method, where MAA on Qdot surfaces is exchanged with thiolated peptides via chemical equilibria.[52] Mattoussi et al. used adaptor amino acid sequences (via electrostatic interactions) to link proteins to the Qdot surfaces.[53,54] Furthermore, Qdot companies sell streptavidin-coated Qdots, where a streptavidin–biotin interaction mediates the linkage between Qdots and biorecognition molecules. The optical properties and size should be monitored at each step, from the modification of the Qdot surface coating to the coupling of biorecognition molecules onto the Qdots. The inability to characterize these two factors can have a significant impact on their use in biomedical experiments and their results.
3. Optical Properties of Qdots
The optical properties of Qdots can be described by conventional semiconductor physics and quantum mechanics. In semiconductor systems, energy bands called valence and conduction bands exist; the energy difference between the two bands is called the bandgap energy. When a semiconductor is optically or electrically excited, static electrons (electrons located in the valence band) become mobile (electrons located in the conduction band) within the semiconductor matrix.
논문입니다,,다소 길어요,,
번역을 해야 되는데,,도저히 실력이 딸리네요,,
도움주시면 감사하겠습니다,,
Current coating strategies are mediated either by chemical exchange or hydrophobic–hydrophobic interaction. Alivisatos and Nie and their co-workers were the first groups to use chemical exchange for modifying the surface chemistry of Qdots.[14,15] In the chemical-exchange method, a bifunctional molecule, such as mercaptoacetic acid (MAA), competes with TOPO (or another organic stabilizer) for binding to a metal atom on the Qdot surface. With excess bifunctional molecules in solution, the thiol functional groups (from the MAA) outcompete the phosphonic oxides (from the TOPO) for binding onto the metal atoms. If the bifunctional molecules contain a polar functional group that is opposite to the thiol functional group, the Qdots become highly polar and soluble in aqueous solvents. Unfortunately, the disadvantages of this technique are rapid flocculation and decrease in fluorescence quantum yield of the Qdots. Libchaber and Wu and their co-workers were the first groups to use the hydrophobic–hydrophobic interactions to water-solubilize Qdots.[50,51] With this method,an amphiphilic molecule, such as 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(poly(ethylene glycol))-2000], interacts with a TOPO molecule through hydrophobic– hydrophobic interactions on the Qdot surface. The amphiphilic molecule can then be crosslinked to prevent desorption from the surface. The Qdots become polar because of the protruding polar functional groups. Disadvantages of this technique are the procedural complexity of the method, the highcost of coating reagents, and an increase in the overall size of the Qdots after coating. For most biomedical applications, a mechanism to attach biorecognition molecules (e.g., oligonucleotides, antibodies, or peptides) onto the Qdot surface is needed. The additional purpose of the coating molecule on the Qdots surface (besidesimproving the polarity) is to provide organic functional groups (–COOH, NH3) for conjugation to biorecognition
molecules. These groups permit the linkage of biorecognition molecules with Qdots via the popular EDC (1-ethyl-3-(3-dimethylamino propyl)carbodiimide) assisted crosslinking method.[15,51] In this reaction, the carboxylic acid functional groups on the surface of the Qdots can covalently couple to primary amino groups on proteins or oligonucleotides. An amide bond joins these two entities. A drawback of this techniqueis that EDC-mediated conjugation can lead to aggregation of Qdots if the Qdot-to-protein-to-EDC concentrations are not optimized. As a result, several groups have developed other strategies to coat Qdots with biorecognition molecules.
Akerman et al. used a chemical exchange method, where MAA on Qdot surfaces is exchanged with thiolated peptides via chemical equilibria.[52] Mattoussi et al. used adaptor amino acid sequences (via electrostatic interactions) to link proteins to the Qdot surfaces.[53,54] Furthermore, Qdot companies sell streptavidin-coated Qdots, where a streptavidin–biotin interaction mediates the linkage between Qdots and biorecognition molecules. The optical properties and size should be monitored at each step, from the modification of the Qdot surface coating to the coupling of biorecognition molecules onto the Qdots. The inability to characterize these two factors can have a significant impact on their use in biomedical experiments and their results.
3. Optical Properties of Qdots
The optical properties of Qdots can be described by conventional semiconductor physics and quantum mechanics. In semiconductor systems, energy bands called valence and conduction bands exist; the energy difference between the two bands is called the bandgap energy. When a semiconductor is optically or electrically excited, static electrons (electrons located in the valence band) become mobile (electrons located in the conduction band) within the semiconductor matrix.
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