Conformational Effects in the Transport of Glucose through a Cyclic Peptide Nanotube: A Molecular Dynamics Simulation Study

Seo, Yongil,Song, Yeonho,Schatz, George C.,Hwang, Hyonseok American Chemical Society 2018 The Journal of physical chemistry B Vol.122 No.34

<P>The transport behavior of glucose through a cyclic peptide nanotube (CPN), composed of 8 × cyclo[-(Trp-<SMALL>D</SMALL>-Leu)<SUB>4</SUB>-Gln-<SMALL>D</SMALL>-Leu-] rings embedded in DMPC lipid bilayers was examined using all-atom molecular dynamics (AAMD) simulations. Two conformational isomers of β-<SMALL>D</SMALL>-glucose, equatorial (<SUP>4</SUP>C<SUB>1</SUB>) and axial (<SUP>1</SUP>C<SUB>4</SUB>) chair conformers, were used to examine conformational effects on the hydrogen bond network, energetics, and diffusivity of glucose transport through the CPN. Calculations of the number of hydrogen bonds of the two glucose conformers with water molecules and with the CPN illustrate that the total number of hydrogen bonds of the conformers decreases inside the channel compared to bulk water due to the confinement characteristics of the interior of the CPNs although new hydrogen bonds between the hydroxyl and hydroxymethyl hydrogens of glucose and the carbonyl oxygens in the CPN backbone are formed. Despite the decrease of the number of hydrogen bonds inside the CPN, intramolecular hydrogen bonds of <SUP>1</SUP>C<SUB>4</SUB> are maintained during permeation of <SUP>1</SUP>C<SUB>4</SUB> through the CPN. The retention of intramolecular hydrogen bonds and the spherical shape of <SUP>1</SUP>C<SUB>4</SUB> give rise to considerably weaker orientational preferences and higher diffusion coefficients for <SUP>1</SUP>C<SUB>4</SUB> than those of <SUP>4</SUP>C<SUB>1</SUB> inside and outside the CPN. Due to larger dipole moments induced by the alignment of hydroxyl and hydroxymethyl groups, <SUP>1</SUP>C<SUB>4</SUB> has more favorable interactions with the CPN backbone at the channel entrances and inside the channel than <SUP>4</SUP>C<SUB>1</SUB>. In the middle of the CPN channel, entropic gains originating from higher orientational and translational degrees of freedom of <SUP>1</SUP>C<SUB>4</SUB> than those of <SUP>4</SUP>C<SUB>1</SUB> also contribute to lower free energy wells for <SUP>1</SUP>C<SUB>4</SUB> inside the CPN. This work reveals that the conformational variation and intramolecular hydrogen bond formation of β-<SMALL>D</SMALL>-glucose can have important effects on the energetics and dynamics of glucose transport through CPNs, providing insight into the translocation mechanism of <SMALL>D</SMALL>-glucose into the cell through glucose transporters (GLUTs) and the dynamics of glucose confined in silica nanochannels. It is also demonstrated that CPNs can indeed facilitate the permeation of small hydrophilic molecules such as glucose and can be utilized as a novel carrier system for hydrophilic drug compounds into the cell.</P> [FIG OMISSION]</BR>

Ion-mediated single-molecular optical switching and sensing based on the fluorophore-tethered calix[4]pyrrole

Sareen, Divya,Lee, Ji Hye,Hwang, Hyonseok,Yoo, Soeun,Lee, Chang-Hee The Royal Society of Chemistry 2016 Chemical communications Vol.52 No.34

<P>The design and synthesis of the first asymmetrically 'two-walled'' meso-substituted calix[4]pyrrole tethered by a fluorophore and its subsequent implication as an archetype sequential 'on-off-on-off' fluorescent single-molecular switch are reported. The current system permits us to extend the sensitivity up to sub-nanomolar levels with the detection limit as low as 0.4 nM.</P>

Determination of precise pyrimidine cationic structure by vacuum ultraviolet mass-analyzed threshold ionization spectroscopy

Kim, Jae Han,Lee, Ji Hye,Hwang, Hyonseok,Kim, Hong Lae,Kwon, Chan Ho The Royal Society of Chemistry 2014 Physical chemistry chemical physics Vol.16 No.4

<P>The vibrational spectrum of a pyrimidine cation in the ground electronic state was obtained using vacuum ultraviolet mass-analyzed threshold ionization (VUV-MATI) spectroscopy. Accurate ionization energy of pyrimidine was determined from the 0–0 band position in the VUV-MATI spectrum and was measured by varying the PFI field to the zero field limit, which is 75 258 ± 7 cm<SUP>−1</SUP> (9.3308 eV). The spectrum displayed a large number of vibrational peaks, which could be nearly completely assigned through Franck–Condon analysis performed with variations of geometrical parameters at the B3LYP/cc-pVTZ level. Based on the excellent agreement between experimental and calculated results, the definite geometry of the pyrimidine cation in the ground electronic state was determined to be a planar structure with <I>C</I><SUB>2v</SUB> symmetry with a decreased N–N distance in the ring.</P> <P>Graphic Abstract</P><P>The vibrational spectrum of a pyrimidine cation in the ground electronic state was obtained using vacuum ultraviolet mass-analyzed threshold ionization (VUV-MATI) spectroscopy. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c3cp53521e'> </P>

Unique prototropy of <i>meso</i>-alkylidenyl carbaporphyrinoid possessing one <i>meso</i>-exocyclic double bond

Saha, Indrajit,Yoo, Jaeduk,Lee, Ji Hye,Hwang, Hyonseok,Lee, Chang-Hee The Royal Society of Chemistry 2015 Chemical communications Vol.51 No.92

<P>Generic synthesis, identification of structural identity, unique prototropy and spectroscopic properties of <I>meso</I>-alkylidenyl-thia(<I>m</I>-benzi)porphyrinoid containing one exocyclic double bond at the <I>meso</I>-position were presented.</P> <P>Graphic Abstract</P><P>The unique prototropy of <I>meso</I>-alkylidenyl-thia(<I>m</I>-benzi)porphyrinoid containing one exocyclic double bond at the <I>meso</I>-position is presented. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c5cc06871a'> </P>

Remarkably selective, non-linear allosteric regulation of anion binding by a tetracationic calix[4]pyrrole homodimer

Saha, Indrajit,Lee, Ji Hye,Hwang, Hyonseok,Kim, Tae Sun,Lee, Chang-Hee The Royal Society of Chemistry 2015 Chemical communications Vol.51 No.26

<P>A covalently coupled, dimeric tetra-cationic calix[4]pyrrolehomodimer bearing anthracene linkers displayed distinctive cooperativity and fluoride selectivity with positive allosterism. The exclusive and successive binding of fluoride anions is accompanied by large ‘turn-on’ fluorescence (<I>K</I><SUB>2</SUB>/<I>K</I><SUB>1</SUB> = 311).</P> <P>Graphic Abstract</P><P>A covalently coupled, dimeric tetra-cationic calix[4]pyrrole homodimer bearing anthracene linkers displayed distinctive cooperativity and fluoride selectivity with large positive allosterism. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c5cc00487j'> </P>

Effective Alkoxylation of Phosphorescent Heteroleptic Iridium(III) Compounds Bearing Fluorinated Bipyridine Ligands

Oh, Hankook,Park, Ki-Min,Hwang, Hyonseok,Oh, Sihyun,Lee, Ji Hye,Lu, Jia-Sheng,Wang, Suning,Kang, Youngjin American Chemical Society 2013 Organometallics Vol.32 No.21

<P>Facile one-pot synthetic methods for new alkoxo-functionalized heteroleptic cyclometalated Ir(III) compounds have been developed. Nucleophilic substitution of fluorine atoms in [(dfpypy)<SUB>2</SUB>Ir(μ-Cl)]<SUB>2</SUB> (dfpypy = 2′,6′-difluoro-2,3′-bipyridine) by a methoxyethanol in the presence of an ancillary ligand led to the formation of the new alkoxo-functionalized heteroleptic Ir(III) compounds Ir[(RO)<SUB>2</SUB>pypy]<SUB>2</SUB>(N<SUP>∧</SUP>O) in good yields. These compounds have a distorted octahedral geometry around the Ir(III) center with an <I>N,N-trans-meridional</I> configuration. They exhibit intense blue to yellow phosphorescence (λ<SUB>max</SUB> = 453–558 nm) with moderate to excellent quautum efficiencies (0.22 to 0.96). Comparative studies on the fluoro analogues, Ir(dfpypy)<SUB>2</SUB>(N<SUP>∧</SUP>O), were also carried out. Our investigation established that the substitution of a fluorine atom by an alkoxy chain can greatly improve the solubility of the compounds in common organic solvents without significantly altering the emission color and efficiencies, making alkoxy-functionalized Ir(III) compounds potential candidates for use in solution-processable phosphorescence OLEDs.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/orgnd7/2013/orgnd7.2013.32.issue-21/om400770h/production/images/medium/om-2013-00770h_0014.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/om400770h'>ACS Electronic Supporting Info</A></P>

Biphenyl- and Fluorene-Based <i>o</i>-Carboranyl Compounds: Alteration of Photophysical Properties by Distortion of Biphenyl Rings

Shin, Nara,Yu, Seokhyeon,Lee, Ji Hye,Hwang, Hyonseok,Lee, Kang Mun American Chemical Society 2017 Organometallics Vol.36 No.8

<P>Four biphenyl- and fluorene-based o-carboranyl compounds, 4-[2-(p-n-butylphenyl)-1-o-carboran-1-yl]-biphenyl (1B), 4,4 ''-bis[2-(p-n-butylphenyl)-1-o-carboran-1-yl]-biphenyl (2B), 2-[2-(p-n-butylphenyl)-1-o-carboran-1-yl]-fluorene (1F), and 2,7-bis[2-(p-n-butylphenyl)-1-o-carboran-1-yl]fluorene (2F), were prepared and fully characterized by multinuclear NMR spectroscopy and elemental analysis. The crystal structures of 1B and 2B, analyzed by single-crystal X-ray diffraction, exhibited distinct distortions of the central biphenyl rings with dihedral angles of 44.2 and 33.1 degrees. In photoluminescence measurements, fluorene-based carboranyl compounds in the rigid state (e.g., in solution at 77 K and as films) exhibited a noticeable emission in the low-energy region below 400 nm. 1F displayed a low-energy emissive trace in solution at ambient temperature, whereas biphenyl-based carboranes mainly exhibited high-energy emissions above 400 nm. TD-DFT calculations on the first excited singlet (S-1) state of each compound suggested that the emission in the low-energy region involves intramolecular charge transfer (ICT) between the carborane and central phenylene rings, indicating that the radiative decay of these ICT bands could be enhanced by preventing the distortion of the central biphenyl groups. Furthermore, less distortion on the biphenyl rings of the biphenyl-based analogues at Si in the optimized structures supports that these phenylenes must be flat for the formation of stable excited states. Comparison of the quantum efficiency (Phi(PL)) and radiative decay constants (k(r)) of the o-carboranes also reveals definitively that the structural features of the biphenyl groups can have a decisive effect on those photophysical properties.</P>

Silole-spaced triarylamine derivatives as highly efficient organic sensitizers in dye-sensitized solar cells (DSSCs)

Ko, Sangwon,Choi, Hyunbong,Kang, Moon-Sung,Hwang, Hyonseok,Ji, Heesun,Kim, Jinho,Ko, Jaejung,Kang, Youngjin Royal Society of Chemistry 2010 Journal of materials chemistry Vol.20 No.12

<P>Three new organic dyes that contain the dithienosilole (DTS) moiety as spacer have been synthesized and their photophysical/electrochemical properties, theoretical calculation and dye-sensitized solar cell (DSSC) performance have been investigated. The overall conversion efficiencies for DSSCs based on these dyes range from 6.73 to 7.50%, comparable to a (3–5′-[<I>N</I>,<I>N</I>-bis(9,9-dimethylfluorene-2-yl)phenyl]2,2′-bithiophene-5-yl}-2-cyanoacrylic acid (<B>JK-2</B>)-sensitized device (7.63%), fabricated and measured under the same experimental conditions. The DSSC constructed from one of the three compounds shows a higher open-circuit voltage (<I>V</I><SUB>OC</SUB>) compared to those of the other two dye sensitized solar cells due to an increased electron lifetime (<I>τ</I><SUB>e</SUB>) in the conduction band of TiO<SUB>2</SUB>.</P> <P>Graphic Abstract</P><P>Organic sensitizers bearing dithienosilole (DTS) segment as spacer, DTS-Me<SUB>2</SUB>, DTS-Ph<SUB>2</SUB> and DTS-MePh, exhibit solar conversion efficiencies of 6.73, 7.50 and 6.81%, respectively. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=b926163j'> </P>

Photodissocaition Dynamics of Propiolic Acid at 212 nm: The OH Production Channel

Shin, Myeong Suk,Lee, Ji Hye,Hwang, Hyonseok,Kwon, Chan Ho,Kim, Hong Lae Korean Chemical Society 2012 Bulletin of the Korean Chemical Society Vol.33 No.11

Photodissociation dynamics of propiolic acid ($HC{\equiv}C-COOH$) at 212 nm in the gas phase was investigated by measuring rotationally resolved laser-induced fluorescence spectra of OH ($^2{\Pi}$) radicals exclusively produced in the ground electronic state. From the spectra, internal energies of OH and total translational energy of products were determined. The electronic transition at 212 nm responsible for OH dissociation was assigned as the ${\pi}_{C{\equiv}C}{\rightarrow}{\pi}^*{_{C=O}}$ transition by time-dependent density functional theory calculations. Potential energy surfaces of both the ground and electronically excited states were obtained employing quantum chemical calculations. It was suggested that the dissociation of OH from propiolic acid excited at 212 nm should take place along the $S_1/T_1$ potential energy surfaces after internal conversion and/or intersystem crossing from the initially populated $S_2$ state based upon the potential energy calculations and model calculations for energy partitioning of the available energy among products.

Novel Dimeric <i>o</i>-Carboranyl Triarylborane: Intriguing Ratiometric Color-Tunable Sensor via Aggregation-Induced Emission by Fluoride Anions

Choi, Byung Hoon,Lee, Ji Hye,Hwang, Hyonseok,Lee, Kang Mun,Park, Myung Hwan American Chemical Society 2016 Organometallics Vol.35 No.11

<P>A dimeric o-carboranyl triarylborane compound (2) with a biphenylene bridge group was prepared and characterized. Also, its solid-state structure was determined via X-ray diffraction. Treatment of 2 with an excess amount of KF in the presence of 18-crown-6 formed a dimiertype potassium salt, [2-F-2][K-18-crown-6](2); its structure was fully confirmed by multinuclear NMR spectroscopy. UV-vis,,vis titration experiments carried out in THF showed that 2 binds fluoride ions with a binding constant (K) of 8.5 x 10(5) M-1. The linear decline of the UV/vis absorption of 2 upon titration with fluoride suggested that the triarylborane moieties acted as independent binding sites, which were not affected by each other. Contrary to a single emission (lambda(em) = 376 nm) of 2 assignable to an intramolecular charge transfer (ICT) transition at 298 K in THF, a broad low-energy emission band was additionally observed at 77 K, which is dominant in the film state. The TD-DFT calculation on the first excited singlet state (S-1) of 2 show's that the low-energy emission band originates from the CT nature between carborane and triarylborane groups, Aggregation-induced emission (ATE) of 2 was clearly confirmed by enhanced photoluminescence intensity (lambda(em) = 489 nm) upon increasing the water fraction (f(w)) in the THF solution of 2, and it further accounts for the intense emission in the solid state. Interestingly, am emission spectrum of a film sample of 2 upon addition of two equivalents of fluoride ion was was mostly similar to that of [2-F-2] [K.18-crown-6](2), indicating that the ICT-based AIE nature of 2 could be red-shifted by fluoride binding.</P>