Super-Helix Formation Induced by Cyanine J-Aggregates onto Random-Coil Carboxymethyl Amylose as Template
| Autor: | Oh-Kil Kim, Glenn Jernigan, David G. Whitten, Jongtae Je, Leonard Buckley |
|---|---|
| Rok vydání: | 2005 |
| Předmět: |
Circular dichroism
Fluorescence spectrometry Analytical chemistry Concentration effect Microscopy Atomic Force Biochemistry Catalysis chemistry.chemical_compound Colloid and Surface Chemistry Carbohydrate Conformation Cyanine J-aggregate health care economics and organizations Circular Dichroism General Chemistry Carbocyanines Hydrogen-Ion Concentration humanities Random coil Kinetics Spectrometry Fluorescence Monomer chemistry Helix Spectrophotometry Ultraviolet Amylose |
| Zdroj: | Journal of the American Chemical Society. 128:510-516 |
| ISSN: | 1520-5126 0002-7863 |
| Popis: | The J-aggregation of Cyanine-1dye in the presence of carboxymethyl amylose (CMA) is described. The J-aggregation requires a large excess CMA concentration; the J-band maximum appears in the concentration range, [CMA]/[dye] = 10-50, depending on the degree of substitution (DS) of carboxylation, where [CMA] is the concentration of polymer repeat units. An extraordinarily large induced circular dichroism (CD) is observed from J-aggregates of the achiral cyanine dye in association with a random coil CMA, suggesting that the CMA is transformed into a helix. The magnitude of CD intensity increases with increasing DS of CMA and pH up to neutral (where a maximum J-aggregation occurs), while the CMA-bound dye monomer and H-aggregates (occurring at pHor = 9) exhibit no induced CD. The trend in the CD intensity (of the J-aggregates) is in parallel with the fluorescence intensity of the J-aggregates. This suggests that binding of the J-aggregates onto the template CMA is sterically controlled by the asymmetric environment of glucose residues (of CMA) so that more twisting power is exerted with increasing DS (of CMA), rendering the cyanine dye/CMA complex a more rigid (a high fluorescence intensity) super-helix. This is also revealed by the AFM image of a long strand. |
| Databáze: | OpenAIRE |
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