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Full-Text Articles in Chemistry
Host Guest Complexes Of Pentiptycene Receptors Display Edge-To-Face Interaction, Lorenzo Mosca, Petr Koutník, Vincent M. Lynch, Grigory V. Zyryanov, Nina A. Esipenko, Pavel Anzenbacher Jr.
Host Guest Complexes Of Pentiptycene Receptors Display Edge-To-Face Interaction, Lorenzo Mosca, Petr Koutník, Vincent M. Lynch, Grigory V. Zyryanov, Nina A. Esipenko, Pavel Anzenbacher Jr.
Chemistry Faculty Publications
The pentiptycene receptors form edge-to-face complexes with a variety of aromatic guests including nitroaromatics. X-ray diffractometry revealed that compounds 1, 2, and 3 form host-guest assemblies with a thienyl fragment (from a neightboring molecule of 1), benzene and nitrobenzene, respectively. X-ray studies of the three crystal structures reported here strongly suggest the edge-to-face to be a predominant binding mode between the aromatic guests and electron-rich faces of the pentiptycene aromatic cavity.
Supramolecular Sensor For Cancer-Associated Nitrosamines, Tsuyoshi Minami, Nina A. Esipenko, Ben Zhang, Maria E. Kozelkova, Lyle Isaacs, Ryuhei Nishiyabu, Yuji Kubo, Pavel Anzenbacher Jr.
Supramolecular Sensor For Cancer-Associated Nitrosamines, Tsuyoshi Minami, Nina A. Esipenko, Ben Zhang, Maria E. Kozelkova, Lyle Isaacs, Ryuhei Nishiyabu, Yuji Kubo, Pavel Anzenbacher Jr.
Chemistry Faculty Publications
A supramolecular assay based on two fluorescent cucurbit[n]uril probes enables the recognition and quantification of nitrosamines, including cancer-associated nitrosamines, compounds that are difficult to recognize. The cross-reactive sensor leverages weak interactions and competition among the probe, metal, and guest, yielding high information density in the signal output (variance) and enabling the recognition of structurally similar guests.
Dynamic Electron Correlation Effects On The Ground State Potential Energy Surface Of A Retinal Chromophore Model, Samer Gozem, Mark Huntress, Igor Schapiro, Roland Lindh, Alexander A. Granovsky, Celestino Angeli, Massimo Olivucci
Dynamic Electron Correlation Effects On The Ground State Potential Energy Surface Of A Retinal Chromophore Model, Samer Gozem, Mark Huntress, Igor Schapiro, Roland Lindh, Alexander A. Granovsky, Celestino Angeli, Massimo Olivucci
Chemistry Faculty Publications
The ground state potential energy surface of the retinal chromophore of visual pigments (e.g., bovine rhodopsin) features a low-lying conical intersection surrounded by regions with variable charge transfer and diradical electronic structures. This implies that dynamic electron correlation may have a large effect on the shape of the force fields driving its reactivity. To investigate this effect, we focus on mapping the potential energy for three paths located along the ground state CASSCF potential energy surface of the penta-2,4-dieniminium cation taken as a minimal model of the retinal chromophore. The first path spans the bond length alternation coordinate and intercepts …
Liposome Encapsulation Of A Photochemical No Precursor For Controlled Nitric Oxide Release And Simultaneous Fluorescence Imaging, Alexis D. Ostrowski, Brian F. Lin, Matthew V. Tirrell, Peter C. Ford
Liposome Encapsulation Of A Photochemical No Precursor For Controlled Nitric Oxide Release And Simultaneous Fluorescence Imaging, Alexis D. Ostrowski, Brian F. Lin, Matthew V. Tirrell, Peter C. Ford
Chemistry Faculty Publications
Described are photochemical studies of the nitric oxide precursors, trans-Cr(L)(ONO)(2)(+) (L = cyclam = 1,4,8,11-tetraazacyclotetradecane, CrONO, or L = mac = 5,7-dimethyl-6-anthracenylcyclam, mac-CrONO) encapsulated in phosphatidylcholine liposomes. The liposomes provide a means to maintain a localized high concentration of NO releasing complexes and are easily modified for in vivo targeting through self-assembly. Steady, controlled release of NO is seen after photolysis of the liposome-encapsulated CrONO as compared to the burst of NO release seen by the unencapsulated complex in oxygenated solutions. The quantum yields for photochemical NO release from liposome-encapsulated CrONO and mac-CrONO were determined in both oxygenated and anoxic …
Single-Molecule Photon Stamping Fret Spectroscopy Study Of Enzymatic Conformational Dynamics, Yufan He, Maolin Lu, Hong Peter Lu
Single-Molecule Photon Stamping Fret Spectroscopy Study Of Enzymatic Conformational Dynamics, Yufan He, Maolin Lu, Hong Peter Lu
H. Peter Lu
The fluorescence resonant energy transfer (FRET) from a donor to an acceptor via transition dipole-dipole interactions decreases the donor's fluorescent lifetime. The donor's fluorescent lifetime decreases as the FRET efficiency increases, following the equation: E-FRET = 1 - tau(DA)/tau(D), where tau(D) and tau(DA) are the donor fluorescence lifetime without FRET and with FRET. Accordingly, the FRET time trajectories associated with single-molecule conformational dynamics can be recorded by measuring the donor's lifetime fluctuations. In this article, we report our work on the use of a Cy3/Cy5-labeled enzyme, HPPK to demonstrate probing single-molecule conformational dynamics in an enzymatic reaction by measuring single-molecule …
The Effect Of The Charge-Separating Interface On Exciton Dynamics In Photocatalytic Colloidal Heteronanocrystals, Timothy O’Connor, Maxim S. Panov, Andrey Mereshchenko, Alexander N. Tarnovsky, Ryan Lorek, Dimuthu Perera, Geoffrey Diederich, Scott Lambright, Pavel Moroz, Mikhail Zamkov
The Effect Of The Charge-Separating Interface On Exciton Dynamics In Photocatalytic Colloidal Heteronanocrystals, Timothy O’Connor, Maxim S. Panov, Andrey Mereshchenko, Alexander N. Tarnovsky, Ryan Lorek, Dimuthu Perera, Geoffrey Diederich, Scott Lambright, Pavel Moroz, Mikhail Zamkov
Chemistry Faculty Publications
Ultrafast transient absorption spectroscopy was used to investigate the nature of photoinduced charge transfer processes taking place in ZnSe/CdS/Pt colloidal heteronanocrystals. These nanoparticles consist of a dot-in-a-rod semiconductor domain (ZnSe/CdS) coupled to a Pt tip. Together the three components are designed to dissociate an electron-hole pair by pinning the hole in the ZnSe domain while allowing the electron to transfer into the Pt tip. Separated charges can then induce a catalytic reaction, such as the light-driven hydrogen production. Present measurements demonstrate that the internal electron-hole separation is fast and results in the localization of both charges in nonadjacent parts of …
Origin Of Fluorescence In 11-Cis Locked Bovine Rhodopsin, Elena N. Laricheva, Samer Gozem, Silvia Rinaldi, Federico Melaccio, Alessio Valentini, Massimo Olivucci
Origin Of Fluorescence In 11-Cis Locked Bovine Rhodopsin, Elena N. Laricheva, Samer Gozem, Silvia Rinaldi, Federico Melaccio, Alessio Valentini, Massimo Olivucci
Chemistry Faculty Publications
The excited state lifetime of bovine rhodopsin (Rh) increases from ca. 100 fs to 85 ps when the C11=C12 bond of its chromophore is locked by a cyclopentene moiety (Rh5). To explain such an increase, we employed ab initio multiconfigurational quantum chemistry to construct computer models of Rh and Rh5 and to investigate the shape of their excited state potential energy surfaces in a comparative way. Our results show that the observed Rh5 fluorescence (lambda(f)(max) = 620 nm) is due to a previously unreported locally excited intermediate whose lifetime is controlled by a small energy barrier. The analysis of the …
Mechanistic Study Of The Photochemical Hydroxide Ion Release From 9-Hydroxy-10-Methyl-9-Phenyl-9,10-Dihydroacridine, Dapeng Zhou, Renat Khatmullin, Janitha Walpita, Nicholas A. Miller, Hoi Ling Luk, Shubham Vyas, Christopher M. Hadad, Ksenija D. Glusac
Mechanistic Study Of The Photochemical Hydroxide Ion Release From 9-Hydroxy-10-Methyl-9-Phenyl-9,10-Dihydroacridine, Dapeng Zhou, Renat Khatmullin, Janitha Walpita, Nicholas A. Miller, Hoi Ling Luk, Shubham Vyas, Christopher M. Hadad, Ksenija D. Glusac
Chemistry Faculty Publications
The excited-state behavior of 9-hydroxy-10-methyl-9-phenyl-9,10-dihydroacridine and its derivative, 9-methoxy-10-methyl-9-phenyl-9,10-dihydroacridine (AcrOR, R = H, Me), was studied via femtosecond and nanosecond UV-vis transient absorption spectroscopy. The solvent effects on C-O bond cleavage were clearly identified: a fast heterolytic cleavage (tau = 108 ps) was observed in protic solvents, while intersystem crossing was observed in aprotic solvents. Fast heterolysis generates 10methyl-9-phenylacridinium (Acr(+)) and -OH, which have a long recombination lifetime (no signal decay was observed within 100 mu s). AcrOH exhibits the characteristic behavior needed for its utilization as a chromophore in the pOH jump experiment.
Tuning Photophysics And Nonlinear Absorption Of Bipyridyl Platinum(Ii) Bisstilbenylacetylide Complexes By Auxiliary Substituents, Zhongjing Li, Ekaterina Badaeva, Dapeng Zhou, Josiah Bjorgaard, Ksenija D. Glusac, Svetlana Killina, Wenfang Sun
Tuning Photophysics And Nonlinear Absorption Of Bipyridyl Platinum(Ii) Bisstilbenylacetylide Complexes By Auxiliary Substituents, Zhongjing Li, Ekaterina Badaeva, Dapeng Zhou, Josiah Bjorgaard, Ksenija D. Glusac, Svetlana Killina, Wenfang Sun
Chemistry Faculty Publications
The photophysics of six bipyridyl platinum(II) bisstilbenylacetylide complexes with different auxiliary substituents are reported. These photophysical properties have been investigated in detail by UV-vis, photoluminescence (both at room temperature and at 77 K) and transient absorption (nanosecond and femtosecond) spectroscopies, as well as by linear response time-dependent density functional theory (TD-DFT) calculations. The photophysics of the complexes are found to be dominated by the singlet and triplet pi,pi* transitions localized at the stilbenylacetylide ligands with strong admixture of the metal-to-ligand (MLCT) and ligand-to-ligand (LLCT) charge-transfer characters. The interplay between the pi,pi* and MLCT/LLCT states depends on the electron-withdrawing or -donating …
Photoisomerization And Relaxation Dynamics Of A Structurally Modified Biomimetic Photoswitch, Adam D. Dunkelberger, Ryan D. Kieda, Jae Yoon Shin, Riccardo Rossi Paccani, Stefania Fusi, Massimo Olivucci, F. Fleming Crim
Photoisomerization And Relaxation Dynamics Of A Structurally Modified Biomimetic Photoswitch, Adam D. Dunkelberger, Ryan D. Kieda, Jae Yoon Shin, Riccardo Rossi Paccani, Stefania Fusi, Massimo Olivucci, F. Fleming Crim
Chemistry Faculty Publications
Recent experimental and theoretical studies on N-alkylated indanylidene pyrroline Schiff bases (NAIP) show that these compounds exhibit biomimetic photoisomerization analogous to that in the chromophore of rhodopsin. The NAIP compounds studied previously isomerize rapidly and often evolve coherently on the ground-electronic surface after reaction. We present the results of transient electronic absorption spectroscopy on dMe-OMe-NAIP, a newly synthesized NAIP analogue that differs from other NAIP compounds in the substituents on its pyrrolinium ring. Following excitation with 400 nm light, dMe-OMe-NAIP relaxes from the electronic-excited state in less than 500 fs, which is slower than in other analogues, and does not …
Photochemistry Of Monochloro Complexes Of Copper(Ii) In Methanol Probed By Ultrafast Transient Absorption Spectroscopy, Andrey S. Mereshchenko, Suman K. Pal, Kanykey E. Karabaeva, Patrick Z. El-Khoury, Alexander N. Tarnovsky
Photochemistry Of Monochloro Complexes Of Copper(Ii) In Methanol Probed By Ultrafast Transient Absorption Spectroscopy, Andrey S. Mereshchenko, Suman K. Pal, Kanykey E. Karabaeva, Patrick Z. El-Khoury, Alexander N. Tarnovsky
Chemistry Faculty Publications
Ultrafast transient absorption spectra in the deep to near UV range (212-384 nm) were measured for the [Cu-II(MeOH)(5)Cl](+) complexes in methanol following 255-nm excitation of the complex into the ligand-to-metal charge-transfer excited state. The electronically excited complex undergoes sub-200 fs radiationless decay, predominantly via back electron transfer, to the hot electronic ground state followed by fast vibrational relaxation on a 0.4-4 Ps time scale. A minor photochemical channel is Cu-Cl bond dissociation, leading to the reduction of copper(H) to copper(I) and the formation of MeOH center dot Cl charge-transfer complexes. The depletion of ground-state [Cu-II(MeOH)(5)Cl](+) perturbs the equilibrium between several …
Comprehensive Survey And Geometric Classification Of Base Triples In Rna Structures, Neocles B. Leontis, Amal S. Abu Almakarem, Anton I. Petrov, Jesse Stombaugh, Craig L. Zirbel
Comprehensive Survey And Geometric Classification Of Base Triples In Rna Structures, Neocles B. Leontis, Amal S. Abu Almakarem, Anton I. Petrov, Jesse Stombaugh, Craig L. Zirbel
Chemistry Faculty Publications
Base triples are recurrent clusters of three RNA nucleobases interacting edge-to-edge by hydrogen bonding. We find that the central base in almost all triples forms base pairs with the other two bases of the triple, providing a natural way to geometrically classify base triples. Given 12 geometric base pair families defined by the Leontis-Westhof nomenclature, combinatoric enumeration predicts 108 potential geometric base triple families. We searched representative atomic-resolution RNA 3D structures and found instances of 68 of the 108 predicted base triple families. Model building suggests that some of the remaining 40 families may be unlikely to form for steric …
Manipulating Protein Conformations By Single-Molecule Afm-Fret Nanoscopy, Yufan He, Maolin Lu, Jin Cao, H. Peter Lu
Manipulating Protein Conformations By Single-Molecule Afm-Fret Nanoscopy, Yufan He, Maolin Lu, Jin Cao, H. Peter Lu
Chemistry Faculty Publications
Combining atomic force microscopy and fluorescence resonance energy transfer spectroscopy (AFM-FRET), we have developed a single-molecule AFM-FRET nanoscopy approach capable of effectively pinpointing and mechanically manipulating a targeted dye-labeled single protein in a large sampling area and simultaneously monitoring the conformational changes of the targeted protein by recording single-molecule FRET time trajectories. We have further demonstrated an application of using this nanoscopy on manipulation of single-molecule protein conformation and simultaneous single-molecule FRET measurement of a Cy3-Cy5-labeled kinase enzyme, HPPK (6-hydroxymethyl-7,8-dihydropterin pyrophosphokinase). By analyzing time-resolved FRET trajectories and correlated AFM force pulling curves of the targeted single-molecule enzyme, we are able …
Toward A Stable Alpha-Cycloalkyl Amino Acid With A Photoswitchable Cationic Side Chain, Riccardo Rossi Paccani, Donato Donati, Stefania Fusi, Loredana Latterini, Grazia Farina, Vinicio Zanirato, Massimo Olivucci
Toward A Stable Alpha-Cycloalkyl Amino Acid With A Photoswitchable Cationic Side Chain, Riccardo Rossi Paccani, Donato Donati, Stefania Fusi, Loredana Latterini, Grazia Farina, Vinicio Zanirato, Massimo Olivucci
Chemistry Faculty Publications
The N-alkylated indanylidenepyrroline (NAIP) Schiff base 3 is an unnatural a-amino acid precursor potentially useful for the preparation of semisynthetic peptides and proteins incorporating charged side chains whose structure can be modulated via Z/E photoisomerization. Here we report that the heteroallylic protons of 3 led to partial loss of ethanol accompanied by formation of the novel heterocyclic system 4 during attempted deprotection. We also show that the same protons catalyze the thermal isomerization of 3, making the light-driven conformational control concept ineffective for times longer than a few hours. These problems are not present in the previously unreported compound 5 …