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Functionalized cucurbiturils and their applications
Kim, Kimoon,Selvapalam, Narayanan,Ko, Young Ho,Park, Kyeng Min,Kim, Dongwoo,Kim, Jeeyeon Royal Society of Chemistry 2007 Chemical Society reviews Vol.36 No.2
<P>Cucurbit[<I>n</I>]uril (CB[<I>n</I>], <I>n</I> = 5–10), a new family of molecular hosts comprising <I>n</I> glycoluril units, have gained much attention in the new millennium for their exceptional molecular recognition ability. The CB homologues have brought dynamism to CB chemistry, as witnessed by the heightened interest in the field for the last several years. Compared to the chemistry of cyclodextrins and calixarenes, however, that of CB[<I>n</I>] has developed slowly until recently, which may be attributed mainly to their poor solubility in common solvents, and inability to functionalize these molecules. The direct functionalization method of CB[<I>n</I>] propelled CB chemistry to a new height as this new method not only solved the solubility problem but also opened up the gateway to the generation of tailor-made CB[<I>n</I>] derivatives. The functionalization of CB[<I>n</I>] led us to investigate numerous applications including artificial ion channels, vesicles, stationary phases in chromatography, ISEs, polymers, nanomaterials, and many others. This tutorial review describes the recent advances and challenges in the functionalization of CBs along with the applications of functionalized CBs.</P> <P>Graphic Abstract</P><P>The recent advances and challenges in the functionalization of cucurbiturils (CBs) along with the applications of functionalized CBs are described. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=b603088m'> </P>
Lim, Soyoung,Kim, Hyunuk,Selvapalam, Narayanan,Kim, Kyung-Jin,Cho, Sung June,Seo, Gon,Kim, Kimoon WILEY-VCH Verlag 2008 Angewandte Chemie Vol.47 No.18
<B>Graphic Abstract</B> <P>Holely organic solid: Effective packing of the rigid macrocycle cucurbituril through C&n.bond;H⋅⋅⋅O hydrogen-bonding and van der Waals interactions leads to a honeycomb-like structure with unprecedented stability and porosity. It shows extraordinary sorption properties toward gases, particularly acetylene, which are comparable or superior to those of metal–organic frameworks in terms of storage capacity. <img src='wiley_img/14337851-2008-47-18-ANIE200800772-content.gif' alt='wiley_img/14337851-2008-47-18-ANIE200800772-content'> </P>
Jung, Hyuntae,Park, Ji Sun,Yeom, Junseok,Selvapalam, Narayanan,Park, Kyeng Min,Oh, Kyunghoon,Yang, Jeong-A,Park, Keun Hong,Hahn, Sei Kwang,Kim, Kimoon American Chemical Society 2014 Biomacromolecules Vol.15 No.3
<P>Despite a wide investigation of hydrogels as an artificial extracellular matrix, there are few scaffold systems for the facile spatiotemporal control of mesenchymal stem cells (MSCs). Here, we report 3D tissue engineered supramolecular hydrogels prepared with highly water-soluble monofunctionalized cucurbit[6]uril–hyaluronic acid (CB[6]-HA), diaminohexane conjugated HA (DAH-HA), and drug conjugated CB[6] (drug-CB[6]) for the controlled chondrogenesis of human mesenchymal stem cells (hMSCs). The mechanical property of supramolecular HA hydrogels was modulated by changing the cross-linking density for the spatial control of hMSCs. In addition, the differentiation of hMSCs was temporally controlled by changing the release profiles of transforming growth factor-β3 (TGF-β3) and/or dexamethasone (Dexa) from the hydrolyzable Dexa-CB[6]. The effective chondrogenic differentiation of hMSCs encapsulated in the monoCB[6]/DAH-HA hydrogel with TGF-β3 and Dexa-CB[6] was confirmed by biochemical glycosaminoglycan content analysis, real-time quantitative PCR, histological, and immunohistochemical analyses. Taken together, we could confirm the feasibility of cytocompatible monoCB[6]/DAH-HA hydrogels as a platform scaffold with controlled drug delivery for cartilage regeneration and other various tissue engineering applications.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/bomaf6/2014/bomaf6.2014.15.issue-3/bm401123m/production/images/medium/bm-2013-01123m_0010.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/bm401123m'>ACS Electronic Supporting Info</A></P>
Kim, Youngkook,Kim, Hyunuk,Ko, Young Ho,Selvapalam, Narayanan,Rekharsky, Mikhail V.,Inoue, Yoshihisa,Kim, Kimoon WILEY-VCH Verlag 2009 Chemistry Vol.15 No.25
<P>Without interference: The complexation of aliphatic ammonium ions with a water-soluble cucurbit[6]uril (CB[6]) derivative, CB*[6] (see picture), in pure water is investigated by isothermal titration calorimetry, NMR spectroscopy, and X-ray crystallography. The binding affinity of the host in pure water is 2–5 orders of magnitude higher than that in the presence of interfering ions, such as protons and alkali metal ions. <img src='wiley_img/09476539-2009-15-25-CHEM200900305-content.gif' alt='wiley_img/09476539-2009-15-25-CHEM200900305-content'> </P><P>Complexation of a water-soluble cucurbituril (CB) derivative, cyclohexanocucurbit[6]uril (CB*[6]), the cavity dimensions of which are essentially the same as those of CB[6], with various organic mono- and diammonium ions has been studied by isothermal titration calorimetry and <SUP>1</SUP>H NMR spectroscopy. The binding affinity of CB*[6] with the guest molecules in water is 3–5 and 2–3 orders of magnitude higher than those of CB[6] in 50 % formic acid and in 0.05 m NaCl solution, respectively, which is mainly due to the larger enthalpic gains upon complex formation in the absence of interfering ions, such as protons and Na<SUP>+</SUP>. In particular, the binding constant (K) of spermine to CB*[6] was measured to be 3.4×10<SUP>12</SUP> m<SUP>−1</SUP>, which is the highest binding constant ever reported for CB[6] or its derivatives. We also obtained the X-ray crystal structures of α,ω-alkanediammonium ions (C<SUB>n</SUB>DA<SUP>2+</SUP>, n=4–8) and spermine complexes with CB[6], in which the aliphatic chains of the guest molecules take an extended or partially bent conformation inside the CB[6] cavity, depending on the chain length. The hexamethylene chain of C<SUB>6</SUB>DA<SUP>2+</SUP> takes a twisted conformation, which not only allows strong ion–dipole interactions between the ammonium groups and the carbonyl groups at the portals, but also increases hydrophobic interactions between the alkyl part of the guest and the inner wall of the host, which results in the largest enthalpic gain among α,ω-alkanediammonium ions. The thermodynamic parameters associated with the complexation are discussed in relation to the binding modes and conformations of the aliphatic chain of the guest molecules inside the host, which were investigated by <SUP>1</SUP>H NMR spectroscopy and X-ray crystallography.</P> <B>Graphic Abstract</B> <P>Without interference: The complexation of aliphatic ammonium ions with a water-soluble cucurbit[6]uril (CB[6]) derivative, CB*[6] (see picture), in pure water is investigated by isothermal titration calorimetry, NMR spectroscopy, and X-ray crystallography. The binding affinity of the host in pure water is 2–5 orders of magnitude higher than that in the presence of interfering ions, such as protons and alkali metal ions. <img src='wiley_img/09476539-2009-15-25-CHEM200900305-content.gif' alt='wiley_img/09476539-2009-15-25-CHEM200900305-content'> </P>
Guest Binding Dynamics with Cucurbit[7]uril in the Presence of Cations
Tang, Hao,Fuentealba, Denis,Ko, Young Ho,Selvapalam, Narayanan,Kim, Kimoon,Bohne, Cornelia American Chemical Society 2011 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.133 No.50
<P>The binding dynamics of R-(+)-2-naphthyl-1-ethylammonium cation (NpH(+)) with cucurbit[7]uril (CB[7]) was investigated. Competitive binding with Na(+) or H(3)O(+) cations enabled the reaction to be slowed down sufficiently for the kinetics to be studied by fluorescence stopped-flow experiments. The binding of two Na(+) cations to CB[7], i.e., CB[7]Na(+) (K(01) = 130 10 M(-1)) and Na(+)CB[7]Na(+) (K(02) = 21 2 M(-1)), was derived from the analysis of binding isotherms and the kinetic studies. NpH(+) binds only to free CB[7] ((1.06 0.05) 10(7) M(-1)), and the association rate constant of (6.3 0.3) 10(8) M(-1) s(-1) is 1 order of magnitude lower than that for a diffusion-controlled process and much higher than the association rate constant previously determined for other CB[n] systems. The high equilibrium constant for the NpH(+)@CB[7] complex is a consequence of the slow dissociation rate constant of 55 s(-1). The kinetics results showed that formation of a complex between a positively charged guest with CB[n] can occur at a rate close to the diffusion-controlled limit with no detection of a stable exclusion complex.</P>
Kim, Byoung Soo,Ko, Young Ho,Kim, Youngkook,Lee, Hyeong Ju,Selvapalam, N.,Lee, Hee Cheon,Kim, Kimoon Royal Society of Chemistry 2008 Chemical communications Vol.2008 No.24
<P>The water soluble cucurbit[6]uril derivative CB*[6] forms a thermodynamically and kinetically stable host–guest complex with xenon in water, the binding affinity of which is about 3 × 10<SUP>3</SUP> M<SUP>−1</SUP>, comparable to those of cryptophanes, suggesting that it may serve as an effective molecular “carrier” for <SUP>129</SUP>Xe NMR-based biosensors.</P> <P>Graphic Abstract</P><P>The water soluble cucurbit[6]uril derivative CB*[6] forms a thermodynamically and kinetically stable host–guest complex with xenon in water, which suggests that it may serve as an effective molecular “carrier” for <SUP>129</SUP>Xe NMR-based biosensors. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=b805724a'> </P>
High and Highly Anisotropic Proton Conductivity in Organic Molecular Porous Materials
Yoon, Minyoung,Suh, Kyungwon,Kim, Hyunuk,Kim, Yonghwi,Selvapalam, Narayanan,Kim, Kimoon WILEY‐VCH Verlag 2011 Angewandte Chemie Vol.123 No.34
<P><B>Isostrukturelle cucurbiturilbasierte</B> organische poröse Materialien, deren 1D‐Kanäle mit einer Wasser‐Säure‐Anordnung gefüllt sind, unterscheiden sich abhängig von der Art und Menge der in den Kanälen vorliegenden Säuremoleküle in der Protonenleitfähigkeit. Das deutlich anisotrope Leitungsverhalten der Materialien wurde mithilfe von Leitfähigkeitsmessung an Einkristallen untersucht.</P>
Rekharsky, Mikhail V,Mori, Tadashi,Yang, Cheng,Ko, Young Ho,Selvapalam, N,Kim, Hyunuk,Sobransingh, David,Kaifer, Angel E,Liu, Simin,Isaacs, Lyle,Chen, Wei,Moghaddam, Sarvin,Gilson, Michael K,Kim, Kimo National Academy of Sciences 2007 Proceedings of the National Academy of Sciences Vol.104 No.52
<P>The molecular host cucurbit[7]uril forms an extremely stable inclusion complex with the dicationic ferrocene derivative bis(trimethylammoniomethyl)ferrocene in aqueous solution. The equilibrium association constant for this host-guest pair is 3 x 10(15) M(-1) (K(d) = 3 x 10(-16) M), equivalent to that exhibited by the avidin-biotin pair. Although purely synthetic systems with larger association constants have been reported, the present one is unique because it does not rely on polyvalency. Instead, it achieves its extreme affinity by overcoming the compensatory enthalpy-entropy relationship usually observed in supramolecular complexes. Its disproportionately low entropic cost is traced to extensive host desolvation and to the rigidity of both the host and the guest.</P>