Fluorescence of the Complexes of 2-Methylnaphthoate and 2-Hydroxypropyl-α-, -β-, and -γ-Cyclodextrins in Aqueous Solution

2002 ◽  
Vol 56 (12) ◽  
pp. 1579-1587 ◽  
Author(s):  
Antonio Di Marino ◽  
Franscisco Mendicuti
Keyword(s):  
Aqueous Solution ◽  
Fluorescence Anisotropy ◽  
Intensity Ratio ◽  
Driving Forces ◽  
Emission Spectra ◽  
Formation Constants ◽  
Dielectric Constants ◽  
Additional Information ◽  
Fluorescence Techniques ◽  
Naturally Occurring

Fluorescence techniques were employed to study the inclusion complexes of 2-methylnaphthoate (MN) with 2-hydroxypropyl-α-cyclodextrin (αHPCD), 2-hydroxypropyl-β-cyclodextrin (βHPCD), and 2-hydroxypropyl-γ-cyclodextrin (γHPCD). Emission spectra of MN show two vibronic bands whose intensity ratio R is very sensitive to the polarity of the medium. The stoichiometry and formation constants of these complexes were investigated by obtaining R as a function of the cyclodextrin (CD) concentration. Results showed identical stoichiometry (1/1) for the three MN/αHPCD, MN/β-HPCD, and MN/γHPCD complexes. Formation constants at 25 °C were 780 ± 15, 2700 ± 130, and 165 ± 10 M−1, respectively. ΔH0 and ΔS0 were obtained from linear van't Hoff plots. Results reveal that the complexation of MN with αHPCD is enthalpy driven. With βHPCD, both the entropy and enthalpy terms favor the process, whereas the formation of the complex with γHPCD is entropically governed. The extrapolation of R at infinite CD concentration allows us to estimate the effective dielectric constants of the inner CD cavities, which are around 50, but which differ from their counterparts, the naturally occurring α-, β-, and γ-CDs. Fluorescence anisotropy, quencher lifetimes, and average lifetimes can also give additional information about the structure and driving forces accompanying the formation of such complexes.

Thermodynamic Parameters of the Inclusion Complexes of 2-Methylnaphthoate and α- and β-Cyclodextrins

1997 ◽  
Vol 51 (11) ◽  
pp. 1621-1627 ◽  
Author(s):  
Jose Manuel Madrid ◽  
Francisco Mendicuti
Keyword(s):  
Steady State ◽  
Thermodynamic Parameters ◽  
Inclusion Complexes ◽  
Emission Spectra ◽  
Formation Constants ◽  
Enthalpy Change ◽  
Dielectric Constants ◽  
High Enthalpy ◽  
Steady State Fluorescence ◽  
Good Probe

Steady-state fluorescence has been used to study the inclusion complexes of 2-methylnaphthoate (MN) with α- and β-cyclodextrins (CDs). Emission spectra of MN show two bands that are very sensitive to the CD concentration and temperature. The stoichiometry and formation constants of these complexes were investigated by obtaining the ratio of the two bands. Results showed identical stoichiometry (1:1) for both MN/α-CD and MN/β-CD complexes. However, the estimated formation constants were quite different. The thermodynamic parameters Δ H and Δ S were obtained from vant'Hoff plots. Results showed that MN/α-CD complexation is accompanied by an high enthalpy change, while MN/β-CD complexation is mainly en tropically favored. Anisotropy measurements were used to interpret the different signs of Δ S upon inclusion for both complexes. In addition, 2-methylnaphthoate seems to be a good probe for estimating microenvironmental polarity. Effective dielectric constants of inner α- and β-CD cavities were evaluated.

The L2:L3 intensity ratio in soft X-ray emission spectra of 3d-metals

2005 ◽  
Vol 148 (1) ◽  
pp. 1-4 ◽  
Author(s):  
E.Z. Kurmaev ◽  
A.L. Ankudinov ◽  
J.J. Rehr ◽  
L.D. Finkelstein ◽  
P.F. Karimov ◽  
...  
Keyword(s):  
Intensity Ratio ◽  
Emission Spectra ◽  
X Ray ◽  
3D Metals

scholarly journals Stabilisation of Natural Colourants and Lignocellulosic Textiles

2021 ◽  
Author(s):  
◽  
Ying Tang
Keyword(s):  
Reactive Oxygen Species ◽  
Aqueous Solution ◽  
Textile Fibre ◽  
Oxygen Species ◽  
Blue Fluorescence ◽  
Esi Ms ◽  
Naturally Occurring ◽  
Antifungal Effects ◽  
Fluorescent Whitening Agents ◽  
Cyclobutane Ring

<p>The lignocellulosic fibres extracted from the leaves of New Zealand flax, Phormium tenax, have been used as the principal textile fibre by Maori since pre- European times. Variations of antifungal activity were observed in Phormium fibres of different cultivars. The most resistant cultivars of P. tenax in an aqueous antifungal assay also possessed the greatest variety of naturally-occurring 7-hydroxycoumarins as identified by mass spectroscopy, ESI-MS. In addition to antifungal effects, coumarins function as fluorescent whitening agents in Phormium fibres and play a role in the fibre’s photodegradation. Ultraviolet irradiation (350 – 400 nm) of the fibre resulted in a substantial loss of the blue fluorescence originating from a number of 7-hydroxycoumarins present, together with the formation of new fluorophores absorbing and emitting at longer wavelengths, which contribute to the photoyellowing of the fibre. The photolysis of two standard 7-hydroxycoumarins in aqueous solution was examined and two primary photoproducts were elucidated by ESI-MS: a photodimer containing a linking cyclobutane ring and a monomeric photooxidation product. The formation of at least some of the photoproducts is associated with the coumarin-sensitised generation of reactive oxygen species, hydrogen peroxide and superoxide. The fluorescence properties and photodegradation of Chinese handmade papers were also investigated. Papers manufactured by traditional methods were found to be more photostable than that produced from chemically-facilitated techniques.</p>

Local Environment of Surface-Polyelectrolyte-Bound DNA Oligomers

2000 ◽  
Vol 651 ◽  
Author(s):  
Sangmin Jeon ◽  
Sung Chul Bae ◽  
Jiang John Zhao ◽  
Steve Granick
Keyword(s):  
Aqueous Solution ◽  
Salt Concentration ◽  
Fluorescence Anisotropy ◽  
Local Environment ◽  
Time Resolved Fluorescence ◽  
Surface Complexes ◽  
Dna Oligomers ◽  
Time Resolved ◽  
Two Photon ◽  
Anisotropy Decay

AbstractTwo-photon time-resolved fluorescence anisotropy methods were used to study the dynamical environment when fluorescent-labelled DNA oligomers (labelled with FAM, 6-fluorescein-6-carboxamido hexanoate) formed surface complexes with quaternized polyvinylpyridine (QPVP) cationic layers on a glass surface. We compared the anisotropy decay of DNA in bulk aqueous solution, DNA adsorbed onto QPVP, and QPVP-DNA-QPVP sandwich structures. When DNA was adsorbed onto QPVP, its anisotropy decay was dramatically retarded compared to the bulk, which means it had very slow rotational motion on the surface. Motions slowed down with increasing salt concentration up to a level of 0.1 M NaCl, but mobility began to increase at still higher salt concentration owing to detachment from the surface-immobilizing QPVP layers.

Influence of pH on the Absorption and Fluorescence Spectra of 6,7-Dihydroxycoumarin in Aqueous Solution

1982 ◽  
Vol 37 (3) ◽  
pp. 262-265 ◽  
Author(s):  
Jerzy Grzywacz ◽  
Stanisława Taszner
Keyword(s):  
Aqueous Solution ◽  
Fluorescence Spectra ◽  
Singlet State ◽  
Ph Value ◽  
Emission Spectra ◽  
Excited Singlet ◽  
Acid Base ◽  
Wide Ph Range ◽  
Ph Range ◽  
Influence Of Ph

Abstract Absorption and emission spectra of 6,7-dihydroxycoumarin [6,7-DHC] in aqueous solution over a wide pH range are reported. The absorption spectra proved to be strongly sensitive to the pH-value of the solution, whereas the emission spectra change in this range only insignificantly. An interpretation is attempted on the basis of the differences of the acid-base properties of the 6,7-DHC molecule in its ground and excited singlet state. For this purpose the pKa's and pKax's values have been calculated. It has been stated that in the excited state the phototautomer form is very unlikely.

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