Physical Sciences and Mathematics Commons^™

Modulating Photochemical Properties To Enhance The Stability Of Electronically Dimmable Eye Protection Devices, Sruthy Baburaj, Jayachandran Parthiban, Sarvar Aminovich Rakhimov, Rasheedah Johnson, Ludmila Sukhomlinova, Paul Luchette, Steffen Jockusch, Malcolm D. E. Forbes, Jayaraman Sivaguru

Chemistry Faculty Publications

The study evaluates compatibility of stabilizers with dye doped liquid crystal (LC) scaffolds that are used in electronically dimmable materials. The photodegradation of the materials was investigated and suitable stabilizers were evaluated to slow the degradation process. Various types of benzotriazole-based stabilizers were evaluated for stabilizing the liquid crystals. Based on spin trapping experiments, radicals generated upon UV exposure is likely responsible for the degradation of the system. The radical generation is competitively inhibited by the addition of stabilizers.

Abbreviations: LC, liquid crystal; STB, stabilizers.

Towards Upcycling Biomass-Derived Crosslinked Polymers With Light, Ravichandranath Singathi, Ramya Raghunathan, Retheesh Krishnan, Saravana Kumar Rajendran, Sruthy Baburaj, Mukund P. Sibi, Dean C. Webster, Jayaraman Sivaguru

Chemistry Faculty Publications

Photodegradable, recyclable, and renewable, crosslinked polymers from bioresources show promise towards developing a sustainable strategy to address the issue of plastics degradability and recyclability. Photo processes are not widely exploited for upcycling polymers in spite of the potential to have spatial and temporal control of the degradation in addition to being a green process. In this report we highlight a methodology in which biomass-derived crosslinked polymers can be programmed to degrade at ≈300 nm with ≈60 % recovery of the monomer. The recovered monomer was recycled back to the crosslinked polymer.

Thermally Stable Fluorogenic Zn(Ii) Sensor Based On A Bis(Benzimidazole)Pyridine-Linked Phenyl-Silsesquioxane Polymer, Chamika U. Lenora, Nai-Hsuan Hu, Joseph C. Furgal

Chemistry Faculty Publications

A 2,6-bis(2-benzimidazolyl) pyridine-linked silsesquioxane-based semi-branched polymer was synthesized, and its photophysical and metal-sensing properties have been investigated. The polymer is thermally stable up to 285 °C and emits blue in both solid and solution state. The emission of the polymer is sensitive to pH and is gradually decreased and quenched upon protonation of the linkers. The initial emission color is recoverable upon deprotonation with triethylamine. The polymer also shows unique spectroscopic properties in both absorption and emission upon long-term UV irradiation, with red-shifted absorption and emission not present in a simple blended system of phenylsilsesquioxane and linker, suggesting that a …

R-Silsesquioxane-Based Network Polymers By Fluoride Catalyzed Synthesis: An Investigation Of Cross-Linker Structure And Its Influence On Porosity, Nai-Hsuan Hu, Joseph C. Furgal

Chemistry Faculty Publications

Silsesquioxane-based networks are an important class of materials that have many applications where high thermal/oxidative stability and porosity are needed simultaneously. However, there is a great desire to be able to design these materials for specialized applications in environmental remediation and medicine. To do so requires a simple synthesis method to make materials with expanded functionalities. In this article, we explore the synthesis of R-silsesquioxane-based porous networks by fluoride catalysis containing methyl, phenyl and vinyl corners (R-Si(OEt)) combined with four different bis-triethoxysilyl cross-linkers (ethyl, ethylene, acetylene and hexyl). Synthesized materials were then analyzed for their porosity, surface area, thermal stability …

Red-Shifting Mutation Of Light-Driven Sodium-Pump Rhodopsin, Keiichi Inoue, María Del Carmen Marín, Sahoko Tomida, Ryoko Nakamura, Yuta Nakajima, Massimo Olivucci, Hideki Kandori

Chemistry Faculty Publications

Microbial rhodopsins are photoreceptive membrane proteins that transport various ions using light energy. While they are widely used in optogenetics to optically control neuronal activity, rhodopsins that function with longer-wavelength light are highly demanded because of their low phototoxicity and high tissue penetration. Here, we achieve a 40-nm red-shift in the absorption wavelength of a sodium-pump rhodopsin (KR2) by altering dipole moment of residues around the retinal chromophore (KR2 P219T/S254A) without impairing its ion-transport activity. Structural differences in the chromophore of the red-shifted protein from that of the wildtype are observed by Fourier transform infrared spectroscopy. QM/MM models generated with …

How To Fold And Protect Mitochondrial Ribosomal Rna With Fewer Guanines, Maryam Hosseini, Poorna Roy, Marie Sissler, Craig L. Zirbel, Eric Westhof, Neocles B. Leontis

Chemistry Faculty Publications

Mammalian mitochondrial ribosomes evolved from bacterial ribosomes by reduction of ribosomal RNAs, increase of ribosomal protein content, and loss of guanine nucleotides. Guanine is the base most sensitive to oxidative damage. By systematically comparing high-quality, small ribosomal subunit RNA sequence alignments and solved 3D ribosome structures from mammalian mitochondria and bacteria, we deduce rules for folding a complex RNA with the remaining guanines shielded from solvent. Almost all conserved guanines in both bacterial and mammalian mitochondrial ribosomal RNA form guaninespecific, local or long-range, RNA–RNA or RNA– protein interactions. Many solvent-exposed guanines conserved in bacteria are replaced in mammalian mitochondria by …

Polymers Course For Small Colleges And Universities, Joseph Furgal

Chemistry Faculty Publications

This article describes the course design and teaching methodology for a polymer chemistry and applications lecture class specifically aimed at small college and university instruction. This intermediate course for advanced undergraduates and masters level graduate students focuses on teaching the basics of polymer history, synthesis and characterization with connections to the core chemistry curriculum in a small class size environment and without a textbook. Furthermore, an extensive overview of the applications of polymeric materials gives students a connection to real life applications. The course includes polymer case studies, informational lessons on real world objects made of polymers, and demonstrations. Student …

Designing Conical Intersections For Light-Driven Single Molecule Rotary Motors: From Precessional To Axial Motion, Michael Filatov, Massimo Olivucci

Chemistry Faculty Publications

In the past, the design of light-driven single molecule rotary motors has been mainly guided by the modification of their ground-state conformational properties. Further progress in this field is thus likely to be achieved through a detailed understanding of light-induced dynamics of the system and the ways of modulating it by introducing chemical modifications. In the present theoretical work, the analysis of model organic chromophores and synthesized rotary motors is used for rationalizing the effect of electron-withdrawing heteroatoms (such as a cationic nitrogen) on the topography and branching plane of mechanistically relevant conical intersections. Such an analysis reveals how the …

Selective Anion Sensing By Chiral Macrocyclic Receptors With Multiple Hydrogen-Bonding Sites, Tadashi Ema, Keiichi Okuda, Sagiri Watanabe, Takayuki Yamasaki, Tsuyoshi Minami, Nina A. Esipenko, Pavel Anzenbacher Jr.

Chemistry Faculty Publications

Chiral macrocycles featuring sulfonamide and/or amide groups as anion-binding sites were synthesized. X-ray crystal structures and DFT calculations have shown that they adopt different conformations that may lead to unique binding behavior. Indeed, various anions could be sensed by their colorimetric and/or fluorescence signal output. The chiral macrocycles showed chiral recognition for chiral anions. Furthermore, a multisensor array with two or four chiral receptors discriminated seven phosphate anions (AMP, ADP, ATP, CMP, GMP, Pi, and PPi) with 100% classification accuracy.

Enhanced Lifetime Of Excitons In Nonepitaxial Au/Cds Core/Shell Nanocrystals, Scott Lambright, Evgeniia Butaeva, Natalia Razgoniaeva, Thomas Hopkins, Bryan Smith, Dimuthu Perera, Jonathan Corbin, Elena Khon, Rebekah Thomas, Pavel Moroz, Andrey Mereshchenko, Alexander N. Tarnovsky, Mikhail Zamkov

Chemistry Faculty Publications

The ability of metal nanoparticles to capture light through plasmon excitations offers an opportunity for enhancing the optical absorption of plasmon-coupled semiconductor materials via energy transfer. This process, however, requires that the semiconductor component is electrically insulated to prevent a "backward" charge flow into metal and interfacial states, which causes a premature dissociation of excitons. Here we demonstrate that such an energy exchange can be achieved on the nanoscale by using nonepitaxial Au/CdS core/shell nanocomposites. These materials are fabricated via a multistep cation exchange reaction, which decouples metal and semiconductor phases leading to fewer interfacial defects. Ultrafast transient absorption measurements …

5-Azido-2-Aminopyridine, A New Nitrene/Nitrenium Ion Photoaffinity Labeling Agent That Exhibits Reversible Intersystem Crossing Between Singlet And Triplet Nitrenes, Maxim S. Panov, Valentyna D. Voskresenska, Mikhail N. Ryazantsev, Alexander N. Tarnovsky, R. Marshall Wilson

Chemistry Faculty Publications

The photochemistry of a new photoaffinity labeling (PAL) agent, 5-azido-2-(N,N-diethylamino)pyridine, was studied in aprotic and protic solvents using femtosecond-to-microsecond transient absorption and product analysis, in conjunction with ab initio multiconfigurational and multireference quantum chemical calculations. The excited singlet SI state is spectroscopically dark, whereas photoexcitation to higher-lying singlet excited S-2 and S-3 states drives the photochemical reaction toward a barrierless ultrafast relaxation path via two conical intersections to S-1, where N-2 elimination leads to the formation of the closed-shell singlet nitrene. The singlet nitrene undergoes intersystem crossing (ISC) to the triplet nitrene in aprotic and protic solvents as well as …

Probing Vibrationally Mediated Ultrafast Excited-State Reaction Dynamics With Multireference (Caspt2) Trajectories, Patrick Z. El-Khoury, Saju Joseph, Igor Schapiro, Samer Gozem, Massimo Olivucci, Alexander N. Tarnovsky

Chemistry Faculty Publications

Excited-state trajectories computed at the complete active space second-order perturbation theory (CASPT2) reveal how vibrational excitation controls the molecular approach to the intersection space that drives the photodissociation of a prototypical halogenated methyl radical, namely CF2I. Translating the Franck-Condon structure along the ground-state CASPT2 vibrational modes in this system followed by propagating the displaced structures in the first excited doublet state simulates specific vibrational excitations and vibrationally mediated dynamics, respectively. Three distinct situations are encountered: the trajectories (i) converge to an energetically flat segment of the intersection space, (ii) locate a segment of the intersection space, and (iii) access a …

Isosteric And Nonisosteric Base Pairs In Rna Motifs: Molecular Dynamics And Bioinformatics Study Of The Sarcin Ricin Internal Loop, Marek Havrila, Kamila RéBlová, Craig L. Zirbel, Neocles B. Leontis, JiřÍ ŠPoner

Chemistry Faculty Publications

The sarcin-ricin RNA motif (SR motif) is one of the most prominent recurrent RNA building blocks that occurs in many different RNA contexts and folds autonomously, that is, in a context-independent manner. In this study, we combined bioinformatics analysis with explicit-solvent molecular dynamics (MD) simulations to better understand the relation between the RNA sequence and the evolutionary patterns of the SR motif. A SHAPE probing experiment was also performed to confirm the fidelity of the MD simulations. We identified 57 instances of the SR motif in a nonredundant subset of the RNA X-ray structure database and analyzed their base pairing, …

Mapping The Excited State Potential Energy Surface Of A Retinal Chromophore Model With Multireference And Equation-Of-Motion Coupled-Cluster Methods, Samer Gozem, Federico Melaccio, Roland Lindh, Anna I. Krylov, Alexander A. Granovsky, Celestino Angeli, Massimo Olivucci

Chemistry Faculty Publications

The photoisomerization of the retinal chromophore of visual pigments proceeds along a complex reaction coordinate on a multidimensional surface that comprises a hydrogen-out-of-plane (HOOP) coordinate, a bond length alternation (BLA) coordinate, a single bond torsion and, finally, the reactive double bond torsion. These degrees of freedom are coupled with changes in the electronic structure of the chromophore and, therefore, the computational investigation of the photochemistry of such systems requires the use of a methodology capable of describing electronic structure changes along all those coordinates. Here, we employ the penta-2,4-dieniminium (PSB3) cation as a minimal model of the retinal chromophore of …

Multianalyte Sensing Of Addictive Over-The-Counter (Otc) Drugs, Tsuyoshi Minami, Nina A. Esipenko, Ali Akdeniz, Ben Zhang, Lyle Isaacs, Pavel Anzenbacher Jr.

Chemistry Faculty Publications

A supramolecular sensor array composed of two fluorescent cucurbit[n]uril-type receptors (probe 1 and probe 2) displaying complementary selectivities was tested for its ability to detect and quantify drug-related amines. The fluorimetric titration of the individual probes showed highly variable and cross-reactive analyte-dependent changes in fluorescence. An excellent ability to recognize a variety of analytes was demonstrated in qualitative as well as quantitative assays. Importantly, a successful quantitative analysis of several analytes of interest was achieved in mixtures and in human urine. The throughput and sensitivity surpass those of the current state-of-the-art methods that usually require analyte solid-phase extraction (SPE). These …

Suspended Lipid Bilayer For Optical And Electrical Measurements Of Single Ion Channel Proteins, Suneth P. Rajapaksha, Xuefei Wang, H. Peter Lu

Chemistry Faculty Publications

Making and holding an artificial lipid bilayer horizontally in an aqueous solution within the microscopic working distance of similar to 100 mu m are essential for simultaneous single molecule imaging and single ion-channel electrical current recording. However, preparation of such a lipid bilayer without a solid support is technically challenging. In a typical supported lipid bilayer, the asymmetric local environments and the strong perturbation of the underneath solid or dense surface can diverge the normal behavior of membrane proteins and lipids. On the other hand, the suspended lipid bilayers can provide a native local environment for the membrane proteins and …

Assessment Of Density Functional Theory For Describing The Correlation Effects On The Ground And Excited State Potential Energy Surfaces Of A Retinal Chromophore Model, Miquel Huix-Rotllant, Michael Filatov, Samer Gozem, Igor Schapiro, Massimo Olivucci, Nicolas Ferré

Chemistry Faculty Publications

In the quest for a cost-effective level of theory able to describe a large portion of the ground and excited potential energy surfaces of large chromophores, promising approaches are rooted in various approximations to the exact density functional theory (DFT). In the present work, we investigate how generalized Kohn-Sham DFT (GKS-DFT), time-dependent DFT (TDDFT), and spin-restricted ensemble-DFT (REKS) methods perform along three important paths characterizing a model retinal chromophore (the penta-2,4-dieniminium cation) in a region of near-degeneracy (close to a conical intersection) with respect to reference high-level multiconfigurational wave function methods. If GKS-DFT correctly describes the closed-shell charge transfer state, …

Toward An Understanding Of The Retinal Chromophore In Rhodopsin Mimics, Mark M. Huntress, Samer Gozem, Konstantin R. Malley, Askat E. Jailaubekov, Chrysoula Vasileiou, Mikas Vengris, James H. Geiger, Babak Borhan, Igor Schapiro, Delmar S. Larsen, Massimo Olivucci

Chemistry Faculty Publications

Recently, a rhodopsin protein mimic was constructed by combining mutants of the cellular retinoic acid binding protein II (CRABPII) with an all-trans retinal chromophore. Here, we present a combine computational quantum mechanics/molecular mechanics (QM/MM) and experimental ultrafast kinetic study of CRABPII. We employ the QM/MM models to study the absorption (lambda(a)(max)), fluorescence (lambda(f)(max)), and reactivity of a CRABPII triple mutant incorporating the all-trans protonated chromophore (PSB-KLE-CRABPII). We also study the spectroscopy of the same mutant incorporating the unprotonated chromophore and of another double mutant incorporating the neutral unbound retinal molecule held inside the pocket. Finally, for PSB-KLE-CRABPII, stationary fluorescence spectroscopy …

Controlled Formation Of Emissive Silver Nanoclusters Using Rationally Designed Metal-Binding Proteins, Vasily A. Morozov, Michael Y. Ogawa

Chemistry Faculty Publications

The metal-binding properties of rationally designed, synthetic proteins were used to prepare a series of emissive silver nanoclusters having predictable sizes and emission energies. Metal-binding a-helical coiled coils were designed to exist as peptide trimers, tetramers, and hexamers and found to uniquely bind 6, 8, and 12 Ag+ ions, respectively. Subsequent treatment with a chemical reducing agent produced a series of peptide-bound Ag-0 nanoclusters that display a strong visible fluorescence whose emission energies depend on the number of bound metal ions in excellent agreement with theory.

Inverse Versus Normal Dithienylethenes: Computational Investigation Of The Photocyclization Reaction, AuréLie Perrier, StéPhane Aloise, Massimo Olivucci, Denis Jacquemin

Chemistry Faculty Publications

The understanding of the intimate electronic processes in photochromes is essential to optimize the properties of light-controllable devices. For one of the most studied classes of molecular switches, namely, dithienylethenes, the relative efficiencies of the normal and inverse structures remained puzzling. Indeed, despite a larger ratio of the active antiparallel conformers for the latter, the quantum yields of cyclization of inverse dithienylethenes do not exceed those of its normal counterpart. In the present contribution, we provide the first explanation of this experimental outcome using multireference ab initio quantum chemistry. We demonstrate the existence of a fluorescent intermediate on the S-1 …

Sensing Of Carboxylate Drugs In Urine By A Supramolecular Sensor Array, Yuanli Liu, Tsuyoshi Minami, Ryuhei Nishiyabu, Zhuo Wang, Pavel Anzenbacher Jr.

Chemistry Faculty Publications

A supramolecular sensor array consisting of eight chemosensors embedded in a hydrogel matrix was used to sense carboxylate drugs. The discriminatory power of the array has been evaluated using principal component analysis and linear discriminant analysis. The eight-member sensor array has been shown to accurately identify 14 carboxylates in water with 100% classification accuracy. To demonstrate the potential for practical utility in the physiological environment, analysis of carboxylate drugs in human urine was also performed achieving 100% correct classification. In addition, the array performance in semiquantitative identification of nonsteroidal anti-inflammatory drugs has been investigated, and the results show that the …

Effects Of The Protein Environment On The Spectral Properties Of Tryptophan Radicals In Pseudomonas Aeruginosa Azurin, Caterina Bernini, Tadeusz AndrunióW, Massimo Olivucci, Rebecca Pogni, Riccardo Basosi, Adalgisa Sinicropi

Chemistry Faculty Publications

Many biological electron-transfer reactions involve short-lived tryptophan radicals as key reactive intermediates. While these species are difficult to investigate, the recent photogeneration of a long-lived neutral tryptophan radical in two Pseudomonas aeruginosa azurin mutants (Az48W and ReAz108W) made it possible to characterize the electronic, vibrational, and magnetic properties of such species and their sensitivity to the molecular environment. Indeed, in Az48W the radical is embedded in the hydrophobic core while, in ReAz108W it is solvent-exposed. Here we use density functional theory and multiconfigurational perturbation theory to construct quantum-mechanics/molecular-mechanics models of Az48W* and ReAz108W* capable of reproducing specific features of their …

Oxidation Of Adenosine And Inosine: The Chemistry Of 8-Oxo-7,8-Dihydropurines, Purine Iminoquinones, And Purine Quinones As Observed By Ultrafast Spectroscopy, Denis I. Nilov, Dmitry Y. Komarov, Maxim S. Panov, Kanykey E. Karabaeva, Andrey S. Mereshchenko, Alexander N. Tarnovsky, R. Marshall Wilson

Chemistry Faculty Publications

Oxidative damage to purine nucleic acid bases proceeds through quinoidal intermediates derived from their corresponding 8-oxo-7,8-dihydropurine bases. Oxidation studies of 8-oxo-7,8-dihyroadenosine and 8-oxo-7,8-dihydroinosine indicate that these quinoidal species can produce stable cross links with a wide variety of nucleophiles in the 2-positions of the purines. An azide precursor for the adenosine iminoquinone has been synthesized and applied in ultrafast transient absorption spectroscopic studies. Thus, the adenosine iminoquinone can be observed directly, and its susceptibility to nudeophilic attack with various nucleophiles as well as the stability of the resulting cross linked species have been evaluated Finally, these observations indicate that this …

Tuning Photophysical Properties And Improving Nonlinear Absorption Of Pt(Ii) Diimine Complexes With Extended Pi-Conjugation In The Acetylide Ligands, Rui Liu, Alexander Azenkeng, Dapeng Zhou, Yuhao Li, Ksenija D. Glusac, Wenfang Sun

Chemistry Faculty Publications

Two new Pt(II) 4,4'-di(5,9-diethyltridecan-7-yl)-2,2'-bipyridine complexes (1 and 2,) bearing 9,9-diethyl-2-ethynyl-7-(2-(4-nitrophenyl)ethynyl)-9H-fluorene ligand and N-(4-(2-(9,9-diethyl-7-ethynyl-9H-fluoren-2-yl)ethynyl)phenyl)-N-phenylbenzeneamine ligand, respectively, were synthesized and characterized. Their photophysical properties were investigated systematically by UV vis absorption, emission, and transient absorption (TA) spectroscopy, and the nonlinear absorption was studied by nonlinear transmission technique. Theoretical TD-DFT calculations using the CAM-B3LYP functional were carried out to determine the nature of the singlet excited electronic states and to assist in the assignment of significant transitions observed in experiments. Complex 1 exhibits an intense, structureless absorption band at ca. 397 nm in CH2Cl2 solution, which is attributed to mixed metal-to-ligand charge transfer …

Global Sampling Of The Photochemical Reaction Paths Of Bromoform By Ultrafast Deep-Uv Through Near-Ir Transient Absorption And Ab Initio Multiconfigurational Calculations, Alexander N. Tarnovsky, S. K. Pal, A. S. Mereshchenko, E. V. Butaeva, Patrick Z. El-Khoury

Chemistry Faculty Publications

Ultrafast deep-ultraviolet through near infrared (210-950 nm) transient absorption spectroscopy complemented by ab initio multiconfigurational calculations offers a global description of the photochemical reaction pathways of bromoform following 255-nm excitation in methylcyclohexane and acetonitrile solutions. Photoexcitation of CHBr3 leads to the ground-state iso-CHBr3 product in a large quantum yield (∼35), formed through two different mechanisms: concerted excited-state isomerization and cage-induced isomerization through the recombination of the nascent radical pair. These two processes take place on different time scales of tens of femtoseconds and several picoseconds, respectively. The novel ultrafast direct isomerization pathway proposed herein is consistent with the occurrence of …

Combined Self-Consistent-Field And Spin-Flip Tamm-Dancoff Density Functional Approach To Potential Energy Surfaces For Photochemistry, Xuefei Xu, Samer Gozem, Massimo Olivucci, Donald G. Truhlar

Chemistry Faculty Publications

We present a new approach to calculating potential energy surfaces for photochemical reactions by combining self-consistent-field calculations for single-reference ground and excited states with symmetry-corrected spin-flip Tamm-Dancoff approximation calculations for multireference electronic states. The method is illustrated by an application with the M05-2X exchange-correlation functional to cis-trans isomerization of the penta-2,4-dieniminium cation, which is a model (with three conjugated double bonds) of the protonated Schiff base of retinal. We find good agreement with multireference configuration interaction-plus-quadruples (MRCISD+Q) wave function calculations along three key paths in the strong-interaction region of the ground and first excited singlet states.

Conical Intersection And Potential Energy Surface Features Of A Model Retinal Chromophore: Comparison Of Eom-Cc And Multireference Methods, Samer Gozem, Anna I. Krylov, Massimo Olivucci

Chemistry Faculty Publications

This work investigates the performance of equation-of-motion coupled-cluster (EOM-CC) methods for describing the changes in the potential energy surfaces of the penta-2,4-dieniminium cation, a reduced model of the retinal chromophore of visual pigments, due to dynamical electron correlation effects. The ground-state wave function of this model includes charge-transfer and diradical configurations whose weights vary along different displacements and are rapidly changing at the conical intersection between the ground and the first excited states, making the shape of the potential energy surface sensitive to a balanced description of nondynamical and dynamical correlation. Recently, variational (MRCISD) and perturbative (MRPT2) approaches for including …

Single-Cell Imaging And Spectroscopic Analyses Of Cr(Vi) Reduction On The Surface Of Bacterial Cells, Yuanmin Wang, Papatya C. Sevinc, Sara M. Belchik, Jim Fredrickson, Liang Shi, H. Peter Lu

Chemistry Faculty Publications

We investigate the single-cell reduction of toxic Cr(VI) by the dissimilatory metal-reducing bacterium Shewanella oneidensis MR-1 (MR-1), an important bioremediation process, using Raman spectroscopy and scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDX). Our experiments indicate that the toxic, highly soluble Cr(VI) can be efficiently reduced to less toxic, nonsoluble Cr2O3 nanoparticles by MR-1. Cr2O3 is observed to emerge as nanoparticles adsorbed on the cell surface and its chemical nature is identified by EDX imaging and Raman spectroscopy. Co-localization of Cr2O3 and cytochromes by EDX imaging and Raman spectroscopy suggests a terminal reductase role for MR-1 surface-exposed cytochromes …

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.

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.