# Host-Guest Complexation Studied by Fluorescence Correlation Spectroscopy: Adamantane–Cyclodextrin Inclusion

^{1}

^{2}

^{*}

## Abstract

**:**

^{4}M

^{−1}are obtained in aqueous solution at 25 °C and pH = 6. The necessary experimental conditions are discussed. FCS proves to be an excellent method for the determination of stoichiometry and association equilibrium constant of this type of complexes, where both host and guest are nonfluorescent and which are therefore not easily amenable to standard fluorescence spectroscopic methods.

## 1. Introduction

_{10}H

_{16}) is formed by four cyclohexanes fused to each other in chair conformations achieving a strain free and highly symmetrical stable structure. The adamantyl group is a spherical group with a diameter of 7 Å which perfectly matches the cavity diameter of βCD. Adamantane derivatives form therefore 1:1 inclusion complexes with βCD with high values of the association equilibrium constant, typically between 10

^{4}–10

^{5}M

^{−1}[26–31]. Due to their high stability βCD-adamantane complexes have found several important applications both in supramolecular chemistry and in biomedical applications, such as hydrogels [32], affinity biosensors [33], surface-mediated gene delivery [34], cyclodextrin polymer-based particles [35, or supramolecular polymers [36,37].

## 2. Theory

#### 2.1. Mechanism

_{+}) and exit (dissociation) (k

_{−}) rate constants as follows:

_{0}, and the complexation “reaction” is pseudo-first-order with the relaxation (“reaction”) time τ

_{R}given by:

#### 2.2. FCS

_{D}is given in Equation (5):

^{2}radii w

_{xy}and w

_{z}, respectively. N is the mean number of fluorescent molecules within the sample volume and τ

_{D}is the translational diffusion (transit) time of the molecules across the sample volume, which is related to the translational diffusion coefficient D by Equation (6) [3,41]. The radius of the sampling volume, w

_{xy}, is determined from a calibration measurement with a reference dye with known diffusion coefficient (in this case rhodamine 123) as described in the Experimental section.

_{T}and a time constant τ

_{T}given by the triplet lifetime of the fluorophore. This leads to an additional exponential term in the correlation function as described in Equation (7):

_{R}≪ τ

_{D}) these states of the fluorophore will not be seen by FCS as two distinct species, but as a single one with a mean diffusion time τ̄

_{D}. The value of τ̄

_{D}depends then on the individual diffusion coefficients D

_{f}and D

_{b}of free and bound fluorophore and on the molar fractions X

_{x}= N

_{x}/(N

_{f}+ N

_{b}) of these species:

_{D}:

_{D}can be expressed as function of the total host concentration [H]

_{0}, the equilibrium association constant K and the limiting values of the diffusion times of free and bound dye, τ

_{f}and τ

_{b}, respectively:

## 3. Results and Discussion

^{−3}mol dm

^{−3}) has only small influence on the brightness of the fluorophore, with a reduction of about 5% at low and about 25% at highest irradiance. This change may be due to different photobleaching probabilities of free and complexed dye, to polarisation effects in the detection optics, to a change of the refractive index of the solution, or to increased scattering, but it may also be due to some direct interaction between the Alexa 488 chromophore and the adamantane-cyclodextrin complex. However, the Alexa 488 fluorophore is too big to be included into the βCD cavity and no efficient competition with the adamantane inclusion is to be expected.

_{0}/2 = 27 kW cm

^{−2}was chosen, which is at the upper end of the linear increase of the brightness.

_{DT}[Equation (9)] yielding the diffusion times τ

_{D}shown in the inset of Figure 4a.

_{D}already at very low βCD concentration can not be explained by an increase of the solvent viscosity, which is not significant at these low cyclodextrin concentrations [43]. We interpret these values of τ

_{D}as mean diffusion times τ̄

_{D}of the fluorophore in fast exchange between free and bound states as described by Equations (8)–(10). The fit of these mean diffusion times τ̄

_{D}by the model of a complexation with stoichiometry 1:1 [Equation (10)] is very satisfactory as shown in Figure 5. More precise values of the parameters are obtained by a direct global target fit of the correlation curves by Equations (9) and (10) as shown in Figure 4. The results of this global fit are listed in Table 1, together with calculated values of the diffusion coefficients and the hydrodynamic radii of free dye and the complex.

^{2}radius of the sample volume obtained from a calibration with Rhodamine 123 as reference (see experimental section). The uncertainty in this calibration and other systematic errors are not included in the indicated standard deviations. The hydrodynamic radii R

_{h}of free Ada-A488 and of the complex Ada-A488:βCD were estimated applying the Stokes-Einstein relation [Equation (11)] with the viscosity of water η (25 °C) = 0.8905 cP:

_{h}

^{−1}~M

^{−1/3}. As shown previously this is well fulfilled for small globular molecules and for inclusion complexes of different cyclodextrins [4]. In this case the ratio between the diffusion coefficients D

_{b}/D

_{f}= 0.74 coincides perfectly with that expected from the ratio of their molar masses (M

_{b}/M

_{f})

^{−1/3}= (2.37)

^{−1/3}= 0.75. The absolute values of the diffusion coefficients compare very well with those obtained before for complexes between pyronines and βCD and γCD [4,5].

_{D)}/τ

_{D}≈ 2%. This translates to a minimal detectable relative change of the molar mass of the fluorophore from this data of about 20%.

^{4}M

^{−1}agrees well with that given in the literature for the inclusion of different adamantane derivatives into βCD with values of K = 1–10 × 10

^{4}M

^{−1}[26–31,44].

## 4. Experimental Section

#### 4.1. Materials

^{−1}) was used as delivered. βCD was checked for fluorescence impurities and was found to be clean enough for classical fluorescence measurements and for FCS experiments. Water was purified with a Milli-Q system. The synthesis of the Ada-A488 compound (M = 825.88 g mol

^{−1}) is described in Section 4.4.

#### 4.2. Sample Preparation

^{−3}mol dm

^{−3}. Stock solutions of Ada-A488 were prepared as follows: the solid compound Ada-A488 was first dissolved in ethanol in order to facilitate its solubilisation. Then, an aliquot of this solution was diluted 1,000 times in 0.1 mol dm

^{−3}phosphate buffer to adjust the pH at 6. The concentrations of Ada-A488 in these stock solutions were still 25-fold higher than that necessary for the FCS measurements (approximately 10

^{−9}mol dm

^{−3}). The FCS samples were finally prepared by dilution of a constant volume of the corresponding Ada-A488 stock together with different volumes of the βCD stock solution and addition of water to adjust to a certain total volume. All these volumes were weighed so that concentration corrections could be performed. Special care was taken in order to avoid any possible contamination of the samples with fluorescent impurities. At the highest βCD concentrations a slight turbidity was observed in the samples, which explains an additional small very slow term in the correlation curves.

#### 4.3. FCS Measurements

_{0}/2 = P/(π·ω

_{xy}

^{2}) = 27 kW cm

^{−2}, assuming a Gaussian intensity distribution along the optical axis. P is the excitation power in the sample) [46].

^{2}radius of ω

_{xy}= 0.53 μm. The value of D

_{R123}= (4.6 ± 0.4) × 10

^{−10}m

^{2}s

^{−1}is estimated from recent PFG-NMR [47] and dual-focus FCS [48] data. The diffusion coefficients are given for 25 °C. All given uncertainties correspond to one standard deviation from the fits and do not include calibration errors.

#### 4.4. Synthesis of the Ada-A488 Compound

#### Preparation of compound 1 (see Scheme 1)

_{3}(sat). The organic layers were dried over Na2SO4, filtered and concentrated under reduce pressure, providing a yellow oil that when purified by flash chromatography (2–4% MeOH in DCM) gave (

**1**, 222 mg) of the compound as a white foam [80%, Rf = 0.5 (5% MeOH in DCM)].

#### Preparation of compound 2

**1**, 25 mg, 0.047 mmols) in piperidine-DCM mixture (1:4, 0.5 mL) was stirred at rt for 20 min, the solvent was removed in vacuo, and the residue was dissolved in DCM. This solution was washed with NaOH (1M). The organic phase was concentrated and dissolved in H2O. The resulted solution was centrifugated and the supernatant was liofilized giving 8-amino-3,6-dioxaocta-methyladamantane amide (

**2**, 11 mg) as a yellow oil which was used without further purification [75%, Rt = 15.3 min (Eclipse Inertsil analitic column, 50–80 % MeOH 0.1%TFA in H2O 0.1%TFA in 19 min)].

^{1}

**H NMR**(CD

_{3}CN, 250.13 MHz, d): 7.04–6.85 (m, 2H, NH

_{2}), 3.9 (s, 2H, CH

_{2}ester), 3.65–3.52 (m, 6H, CH

_{2}ether), 3.01–2.89 (bs, 2H, CH

_{2}amine), 2.83 (d, J = 6.57 Hz, 2H, CH

_{2}amide), 1.72–1.47 (m, 7H, CH and CH

_{2}Ad), 1.4 (s, 6H, CH

_{2}Ad).

#### Preparation of compound 4

**2**, 0.35 mg, 1.12 mmols) and Alexa Fluor 488 carboxylic acid succinimidyl ester (mixed isomers) (

**3**, 0.2 mg, 0.31 mmols) were dissolved in dry DCM (500 mL) and dry DMF (20 mL), DIEA (1 mL, 5.5 mmols) was added and the mixture was stirred under argon for 1 h. The crude was purified by HPLC, affording (

**4**, 0.15 mg) of compound as a pink solid [58%, Rt = 15 min and 16min for 2 isomers (Eclipse Inertsil analitic column, 50–80% MeOH 0.1%TFA in H

_{2}O 0.1%TFA in 19 min)].

**MS (MALDI-TOF**) [m/z (%)]: 825 ([M

^{−}], 100), 779.4 (8), 604.2 (16).

#### Abbreviations Used

_{3}CN: Deuterated acetonitrile; DCM: Dichloromethane; DIEA: Diisopropylethylamine; DMF: dimethylformamide; Fmoc: Fluorenylmethoxycarbonyl; HATU:O-(7-azabenzotriazol-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate;

^{1}H NMR: Proton nuclear magnetic resonance; HPLC: High Performance Liquid Chromatography; MALDI-TOF: Mass Spectrometry of Laser Desorption/Ionization-Time of Flight; bs: broad singlet; d: doublet; m: multiplet; s: singlet; rt: room temperature.

#### Suppliers

## 5. Conclusions

## Acknowledgments

## References and Notes

- Turro, NJ. Supramolecular structure and dynamics special feature: Molecular structure as a blueprint for supramolecular structure chemistry in confined spaces. Proc. Nat. Acad. Sci. USA
**2005**, 102, 10766–10770. [Google Scholar] - Dodziuk, H. Introduction to Supramolecular Chemistry; Springer: Dordrecht, The Netherlands, 2002. [Google Scholar]
- Rigler, R; Elson, ES. Fluorescence Correlation Spectroscopy: Theory and Applications; Springer: Berlin, Germany, 2001. [Google Scholar]
- Al-Soufi, W; Reija, B; Novo, M; Felekyan, S; Kühnemuth, R; Seidel, CAM. Fluorescence correlation spectroscopy, a tool to investigate supramolecular dynamics: Inclusion complexes of pyronines with cyclodextrin. J. Am. Chem. Soc
**2005**, 127, 8775–8784. [Google Scholar] - Al-Soufi, W; Reija, B; Felekyan, S; Seidel, CA; Novo, M. Dynamics of supramolecular association monitored by fluorescence correlation spectroscopy. Chemphyschem
**2008**, 9, 1819–1827. [Google Scholar] - Cramer, F; Hettler, H. Inclusion compounds of cyclodextrins. Naturwissenschaften
**1967**, 54, 625–32. [Google Scholar] - Szejtli, J. Introduction and general overview of cyclodextrin chemistry. Chem. Rev
**1998**, 98, 1743–1754. [Google Scholar] - Dodziuk, H. Cyclodextrins and Their Complexes: Chemistry, Analytical Methods, Applications; Wiley: Weinheim, Germany, 2006. [Google Scholar]
- Carrazana, J; Reija, B; Ramos Cabrer, P; Al-Soufi, W; Novo, M; Vázquez Tato, J. Complexation of methyl orange with beta-cyclodextrin: Detailed analysis and application to quantification of polymer-bound cyclodextrin. Supramol. Chem
**2004**, 16, 549–559. [Google Scholar] - Bordello, J; Reija, B; Al-Soufi, W; Novo, M. Host-assisted guest self-assembly: Enhancement of the dimerization of pyronines Y and B by gamma-cyclodextrin. Chemphyschem
**2009**, 10, 931–939. [Google Scholar] - Reija, B; Al-Soufi, W; Novo, M; Vázquez Tato, J. Specific interactions in the inclusion complexes of Pyronines Y and B with beta-cyclodextrin. J. Phys. Chem. B
**2005**, 109, 1364–1370. [Google Scholar] - Bohne, C. Supramolecular dynamics of guest complexation to cyclodextrins. Spectrum
**2000**, 13, 14–19. [Google Scholar] - Harada, A; Li, J; Kamachi, M. Synthesis of a tubular polymer from threaded cyclodextrins. Nature
**1993**, 364, 516. [Google Scholar] - Lehn, JM. Supramolecular Chemistry; VCH: Weinheim, Germany, 1995. [Google Scholar]
- Nepogodiev, SA; Stoddart, JF. Cyclodextrin-based catenanes and rotaxanes. Chem. Rev
**1998**, 98, 1959–1976. [Google Scholar] - Alvarez Parrilla, E; Ramos Cabrer, P; Al-Soufi, W; Meijide del Río, F; Rodríguez Núñez, EA; Vázquez Tato, J. Dendritic growth of a supramolecular complex. Angew. Chem. Int. Ed. Engl
**2000**, 39, 2856–2858. [Google Scholar] - Ogoshi, T; Harada, A. Chemical sensors based on cyclodextrin derivatives. Sensors
**2008**, 8, 4961–4982. [Google Scholar] - Hennig, A; Bakirci, H; Nau, WM. Label-free continuous enzyme assays with macrocycle-fluorescent dye complexes. Nat. Methods
**2007**, 4, 629–632. [Google Scholar] - Breslow, R; Belvedere, S; Gershell, L; Leung, D. The chelate effect in binding, catalysis, and chemotherapy. Pure Appl. Chem
**2000**, 72, 333–342. [Google Scholar] - Loftsson, T; Brewster, ME. Pharmaceutical applications of cyclodextrins. 1. Drug solubilization and stabilization. J. Pharm. Sci
**1996**, 85, 1017–1025. [Google Scholar] - Uekama, K; Hirayama, F; Irie, T. Cyclodextrin drug carrier systems. Chem. Rev
**1998**, 98, 2045–2076. [Google Scholar] - Hirayama, F; Uekama, K. Cyclodextrin-based controlled drug release system. Adv. Drug Deliv. Rev
**1999**, 36, 125–141. [Google Scholar] - Lezcano, M; Al-Soufi, W; Novo, M; Rodríguez-Núñez, E; Vázquez Tato, J. Complexation of several benzimidazole-type fungicides with alpha- and beta-cyclodextrins. J. Agric. Food Chem
**2002**, 50, 108–112. [Google Scholar] - Ritter, H; Tabatabai, M. Cyclodextrin in polymer synthesis: A green way to polymers. Progr. Polym. Sci
**2002**, 27, 1713–1720. [Google Scholar] - Davis, ME; Brewster, ME. Cyclodextrin-based pharmaceutics: Past, present and future. Nat. Rev. Drug Discov
**2004**, 3, 1023–1035. [Google Scholar] - Eftink, MR; Andy, ML; Bystrom, K; Perlmutter, HD; Kristol, DSJ. Cyclodextrin inclusion complexes: Studies of the variation in the size of alicyclic guests. J. Am. Chem. Soc
**1989**, 111, 6765–6772. [Google Scholar] - Cromwell, WC; Bystrom, K; Eftink, MR. Cyclodextrin-adamantanecarboxylate inclusion complexes: Studies of the variation in cavity size. J. Phys. Chem
**1985**, 89, 326–332. [Google Scholar] - Gelb, RI; Schwartz, LM. Complexation of admantane-ammonium substrates by beta-cyclodextrin and its O-methylated derivatives. J. Incl. Phenom. Mol. Recogn. Chem
**1989**, 7, 537–543. [Google Scholar] - Palepu, R; Reinsborough, VC. β-cyclodextrin inclusion of adamantane derivatives in solution. Aust. J. Chem
**1990**, 43, 2119–2123. [Google Scholar] - Kwak, ES; Gomez, FA. Determination of the binding of β-cyclodextrin derivatives to adamantane carboxylic acids using capillary electrophoresis. Chromatographia
**1996**, 43, 659–662. [Google Scholar] - Harries, D; Rau, DC; Parsegian, VA. Solutes probe hydration in specific association of cyclodextrin and adamantane. J. Am. Chem. Soc
**2005**, 127, 2184–2190. [Google Scholar] - Koopmans, C; Ritter, H. Formation of physical hydrogels via host-guest interactions of b-cyclodextrin polymers and copolymers bearing adamantyl groups. Macromolecules
**2008**, 41, 7418–7422. [Google Scholar] - Holzinger, M; Bouffier, L; Villalonga, R; Cosnier, S. Adamantane/β-cyclodextrin affinity biosensors based on single-walled carbon nanotubes. Biosens. Bioelectron
**2009**, 24, 1128–1134. [Google Scholar] - Park, I; von Recum, HA; Jiang, S; Pun, SH. Spatially-controlled delivery of cyclodextrin-based polyplexes from solid surfaces. Mol. Ther
**2006**, 13, S67–S67. [Google Scholar] - Bellocq, NC; Pun, SH; Jensen, GS; Davis, ME. Transferrin-containing, cyclodextrin polymer-based particles for tumor-targeted gene delivery. Bioconjug. Chem
**2003**, 14, 1122–1132. [Google Scholar] - Munteanu, M; Choi, S; Ritter, H. Cyclodextrin-click-cucurbit[6]uril: Combi-receptor for supramolecular polymer systems in water. Macromolecules
**2009**, 42, 3887–3891. [Google Scholar] - Soto Tellini, VH; Jover, A; Carrazana Garcia, J; Galantini, L; Meijide, F; Vázquez Tato, J. Thermodynamics of formation of host-guest supramolecular polymers. J. Am. Chem. Soc
**2006**, 128, 5728–5734. [Google Scholar] - Widengren, J; Rigler, R. Fluorescence correlation spectroscopy as a tool to investigate chemical reactions in solutions and on cell surfaces. Cell Mol. Biol
**1998**, 44, 857–879. [Google Scholar] - Widengren, J. Photophysical aspects of FCS Measurements; Rigler, R, Elson, ES, Eds.; Springer Verlag: Berlin, Germany, 2001; p. 276. [Google Scholar]
- Haustein, E; Schwille, P. Fluorescence Correlation Spectroscopy in Vitro and in Vivo; Selvin, PR, Ha, T, Eds.; Cold Spring Harbor Laboratory Press: New York, NY, USA, 2008; p. 259. [Google Scholar]
- Elson, EL; Magde, D. Fluorescence correlation spectroscopy. I. Conceptual basis and theory. Biopolymers
**1974**, 13, 1–27. [Google Scholar] - Enderlein, J; Gregor, I; Patra, D; Dertinger, T; Kaupp, UB. Performance of fluorescence correlation spectroscopy for measuring diffusion and concentration. Chemphyschem
**2005**, 6, 2324–2336. [Google Scholar] - Alcor, D; Allemand, JF; Cogne-Laage, E; Croquette, V; Ferrage, F; Jullien, L; Kononov, A; Lemarchand, A. Stochastic resonance to control diffusive motion in chemistry. J. Phys. Chem. B
**2005**, 109, 1318–1328. [Google Scholar] - Carrazana, J; Jover, A; Meijide, F; Soto, VH; Vázquez Tato, J. Complexation of adamantyl compounds by beta-cyclodextrin and monoaminoderivatives. J. Phys. Chem. B
**2005**, 109, 9719–9726. [Google Scholar] - Felekyan, S; Kuhnemuth, R; Kudryavtsev, V; Sandhagen, C; Becker, W; Seidel, CAM. Full correlation from picoseconds to seconds by time-resolved and time-correlated single photon detection. Rev Sci Instrum
**2005**, 76, 083104:1–083104:14. [Google Scholar] - Eggeling, C; Widengren, J; Rigler, R; Seidel, CAM. Photobleaching of fluorescent dyes under conditions used for single-molecule detection: Evidence of two-step photolysis. Anal. Chem
**1998**, 70, 2651–2659. [Google Scholar] - Gendron, PO; Avaltroni, F; Wilkinson, KJ. Diffusion coefficients of several rhodamine derivatives as determined by pulsed field gradient-nuclear magnetic resonance and fluorescence correlation spectroscopy. J. Fluoresc
**2008**, 18, 1093–1101. [Google Scholar] - Muller, C; Loman, A; Pacheco, V; Koberling, F; Willbold, D; Richtering, W. Precise measurement of diffusion by multi-color dual-focus fluorescence correlation spectroscopy. Europhys Lett
**2008**, 83, 46001:1–46001:6. [Google Scholar]

**Figure 1.**Fluorescent labelling of a host-guest complex (a) inclusion of a fluorescent guest (b) guest with attached fluorophore (c) host with attached fluorophore.

**Figure 2.**(a) Structure of Ada-A488 (b) Structure of βCD. (c) Sketch of an adamantane-βCD inclusion complex.

**Figure 3.**Power series of the FCS signal of Ada-A488 in aqueous solution (squares, [βCD]

_{0}= 0 mol dm

^{−3}) and at high concentration of βCD (circles, [βCD]

_{0}= 6.4 × 10

^{−3}mol dm

^{−3}). [Ada-A488] ≈ 10

^{−9}mol dm

^{−3}). Left scale, filled symbols: count rate per single Ada-A488 molecule. Right scale, open symbols: diffusion time of Ada-A488. All data obtained from FCS correlation curves similar to those shown in Figure 4 at different excitation irradiances. Counts per molecule (cpm) is the total detected fluorescence count rate divided by the mean number of molecules in the focus

**N**.

**Figure 4.**Fluorescence intensity correlation curves G(τ) of Ada-A488 in the presence of increasing concentrations of βCD ([βCD] = 0 mol dm

^{−3}to 6.4 × 10

^{−3}mol dm

^{−3}) in aqueous solution. ([Ada-A488] ≈ 10

^{−9}mol dm

^{−3}). Panel a: normalized experimental correlation curves at increasing βCD concentration (grey curves) and two representative curves from the global fit of Equations. (9) and (10) at [βCD] = 0 mol dm

^{−3}(red curve) and [βCD] = 6.4 × 10

^{−3}mol dm

^{−3}(blue curve) to the correlation curves. The intermediate fit curves are not shown for clarity. Small vertical bars indicate the diffusion time obtained from the fit. Inset: mean diffusion times τ̄

_{D}as function of βCD concentration determined from individual fits of the Equation (9) to the correlation curves. The highest concentrations are not shown. See also Figure 5. Panel b: stacked representation of the same correlation curves as in panel a. Panel c: weighted residuals from the global fit (vertical scale is arbitrary).

**Figure 5.**Upper panel: Mean diffusion times τ̄

_{D}as function of βCD concentration determined from individual fits of correlation function G

_{DT}[Equation (9)] to the normalized correlation curves of Figure 4. Parameter of the fit as given in the text. The black curve represents the best fit of Equation (10) to τ̄

_{D}with the parameter τ

_{f}= 225 ± 2 μs, τ

_{b}= 297 ± 2 μs, and K = (48 ± 7) × 10

^{3}mol

^{−1}dm

^{3}. Note that due to the logarithmic concentration scale the values at [βCD] = 0 M are not visible in the figure, although they are included in the fit. Lower panel: residuals of the fit.

**Table 1.**Results of the global target fit of Equations (9) and (10) to the correlation curves shown in Figure 4 and calculated values. All values at 25.0 ± 0.5 °C.

Ada-A488 + βCD | |
---|---|

K/10^{3} M^{−1} | 52 ± 2 |

τ_{f}/ms | 0.222 ± 0.002 |

τ_{b}/ms | 0.300 ± 0.002 |

A_{T} | 0.20 |

τ_{T}/μs | 4.8 |

D_{f}/10^{−10} m^{2}s^{−1} | 3.15 ± 0.30 |

D_{b}/10^{−10} m^{2}s^{−1} | 2.33 ± 0.20 |

R_{h,f}/Å | 7.8 ± 0.7 |

R_{h,b}/Å | 10.5 ± 0.9 |

© 2010 by the authors; licensee Molecular Diversity Preservation International, Basel, Switzerland. This article is an open-access article distributed under the terms and conditions of the Creative Commons Attribution license (http://creativecommons.org/licenses/by/3.0/).

## Share and Cite

**MDPI and ACS Style**

Granadero, D.; Bordello, J.; Pérez-Alvite, M.J.; Novo, M.; Al-Soufi, W.
Host-Guest Complexation Studied by Fluorescence Correlation Spectroscopy: Adamantane–Cyclodextrin Inclusion. *Int. J. Mol. Sci.* **2010**, *11*, 173-188.
https://doi.org/10.3390/ijms11010173

**AMA Style**

Granadero D, Bordello J, Pérez-Alvite MJ, Novo M, Al-Soufi W.
Host-Guest Complexation Studied by Fluorescence Correlation Spectroscopy: Adamantane–Cyclodextrin Inclusion. *International Journal of Molecular Sciences*. 2010; 11(1):173-188.
https://doi.org/10.3390/ijms11010173

**Chicago/Turabian Style**

Granadero, Daniel, Jorge Bordello, Maria Jesus Pérez-Alvite, Mercedes Novo, and Wajih Al-Soufi.
2010. "Host-Guest Complexation Studied by Fluorescence Correlation Spectroscopy: Adamantane–Cyclodextrin Inclusion" *International Journal of Molecular Sciences* 11, no. 1: 173-188.
https://doi.org/10.3390/ijms11010173