Unimolecular Research Articles

Structural requirement of G-quadruplex/aptamer-combined DNA macromolecule serving as efficient drug carrier for cancer-targeted drug delivery

Photodynamic therapy (PDT) as a clinical cancer treatment method has been used to treat carcinomas in different organs, and G-quadruplex-based DNA nanocompartments serving as the carriers of cationic porphyrin photosensitizers, especially combined with cell-targeting aptamers, is considered to offer new opportunities for future cancer treatment. However, the structural features of G-quadruplex/aptamer complexes suitable for the capsulation of photosensitizers and target cell recognition is unexplored so far. In this study, unimolecular (UM), bimolecular (BM) and tetramolecular (TM) G-quadruplex structures were used as the drug loading compartments and grafted onto tumor cell-targeting aptamer Sgc8, constructing several targeting drug delivery vehicles (T-GMVs). Besides the binding affinity of resulting DNA architectures for target cells and cell recognition specificity were explored in a comparative fashion, the drug loading capability and cancer therapy efficacy were evaluated using TMPyP4 as the model porphyrin-based drug. The experimental results show that only TM G-quadruplex structure is suitable to combine with Sgc8 for the development of drug delivery vehicle and the as-prepared T-GMV- TMPyP4 complexes display the desirable cancer therapy efficacy, holding the potential application in the future cancer therapy. More importantly, T-GMV- TMPyP4 is expected to lay the scientific groundwork for the successful development of G-quadruplex-based photosensitizer drug delivery carriers for the targeted cancer therapy.

Encapsulation of fluoride and hydrogen sulfate dimer by polyammonium-functionalised first- and second-generation tripodal: cavity-induced anion encapsulation

AbstractDesign, synthesis and complexation with inorganic anions of first (1L) and second (2L) generation tripodal polyamine receptors are reported here. The C3v symmetric second-generation tripodal receptor (2L) possesses large enough cavity to encapsulate larger hydrogen sulfate dimer in a unimolecular capsular fashion [(HSO4)2⊂2]. The dimer is stabilised by (NH)+⋯O type H-bonding and electrostatic interactions between and ammonium group. Water of crystallisation form hybrid anion–water cluster [(HSO4)–(H2O) with ions located outside the cavity. The [(HSO4)–(H2O) cluster and Cl⋯Cl halogen bond play templating role in the supramolecular aggregation of unimolecular capsule [(HSO4)2⊂2]. On the other hand, first-generation receptor (1L) encapsulates only fluoride ion due to its smaller cavity size and thus form unimolecular fluoride complex [F⊂1]. Overall study shows cavity size-induced anion encapsulation. All complexes are well characterised by FT-IR, NMR, TGA, DSC and XRD experiments.

Preparation and AFM-Characterization of Self-Assembled Monolayers Functionalized with a Thrombin Binding Aptamer

Self-assembled monolayers on silicon oxide surfaces functionalized with a unimolecular DNA G-quadruplex derived from the thrombin binding aptamer have been prepared. The formation of the G-quadruplex in the presence of potassium ions is observed by atomic force microscopy (AFM). The results presented here are interesting for the fabrication of nanostructured systems for sensing applications

High-temperature decomposition of azomethane in shock waves: 4. On the unimolecularity of azomethane decomposition: An analysis of high-temperature data

Our own measurements and published experimental data on azomethane (AM) decomposition at 850–1430 K, in conjunction with a theoretical analysis of this reaction, provide convincing evidence for its occurrence via the concerted mechanism in this temperature range. Most of the available experimental data cannot be described within the framework of the classical theory of unimolecular reactions. The need for direct time-resolved low-temperature data on AM decomposition is emphasized.

High-Temperature Decomposition of Azomethane in Shock Waves: 3. On the Unimolecularity of Azomethane Decomposition under Low-Temperature Conditions

The published data on the rate constant of AM decomposition at low temperatures (T = 500−720 K) are examined. A comparison of extrapolations of the Arrhenius expressions for this rate constant with analogous expressions obtained from direct high-temperature measurements is performed. The degree of deviation of the AM decomposition from classical unimolecular behavior is assessed.

CO product distribution in the unimolecular dissociation of HCO

The unimolecular dissociation of HCO ground state was investigated with the time-dependent full-quantum symplectic propagation based on the newest potential energy surface of the system. Calculated energy and widths of HCO resonance states agree well with those in the literature. CO product distribution was systematically investigated. A simple model was presented to interpret the rovibrational distributions in HCO dissociation.

How Complex can be the Unimolecular Decomposition of a Simple Molecule? The Case of Acetylene. An Electron Impact and PIPECO Investigation

The dissociative ionization of C2H2, C2D2 and C2HD is presented in this work. Excepting the H2 + ion formation, all dissociation channels are thoroughly investigated by electron impact. The translational energy distribution as a function of the impinging electron energy and the appearance energy as a function of the translational energy are measured for all fragment ions. KE versus AE diagrams are obtained and the isotope effect is examined. All observed thresholds are analyzed in detail and dissociation mechanisms are proposed. For the C2H + ion, the PIPECO technique has also been used. From these discussions the H-C2H, HC≡CH and H-C2 binding energy values are proposed, i.e. 5.33±0.23eV, 9.83±0.10eV and 5.44±0.40 eV respectively. The fragmentation paths leading to C, CH2 + and C2 + are discussed in terms of dissociation mechanisms involving the transient vinylidene structure of the molecular ion as an intermediate. Keyword: Acetylene / Dissociation / Electroionization / Photoionization / Coincidence / Kinetic energy Die dissoziative Ionisation von C2H2, C2D2 und C2HD wird in dieser Arbeit vorgestellt. Sâmtliche der dissoziativen Zerfallskanale, bis auf die H2 -Bildung, wurden mit Hilfe der Elektronenstoβionisation untersucht. Fur sâmtliche Fragmentionen wurde die Verteilung der Translationsenergie als Funktion der Energie der auftreffenden Elektronen sowie die Auftrittspotentiale als Funktion der Translationsenergie gemessen. KE-AEDiagramme werden ermittelt sowie Isotopeneffekte bestimmt. Die experimentellen Schwellenenergien werden im Detail analysiert, so daβ sich Dissoziationsmechanismen ableiten lassen. Zur Bestimmung der Eigenschaften des C2H -Ions wurde die PEPICO-Technik verwendet. Aus den experimentellen Resultaten lassen sich die Bindungsenergien von H-C2H, HC≡CH und H-C2 ableiten, die 5,33±0,23 eV, 9,83±0,10 eV, 5,44±0,40 eV betragen. Die Bildung von C, CH2 + sowie C2 + wird mit Hilfe eines Dissoziationsmechanismus diskutiert, der eine transiente Vinyliden-Struktur des intermediaren Molekulions beinhaltet.

Unimolecular Bifurcation Reactions on Potential Energy Surface

Classical transition-state theory assumes that a reaction in which a given reagent,or a set of reagents are converted to a given product, or a set of products, in a sin-gle kinetic step, takes place only in one way, via a unique transition state(TS). Butrecent theories and the related experiments about bifurcations on potential energysurface(PES) show that this assumption is no longer acceptable. When a chemical system proceeds along a reactive path, another reactive pathemerges. We call this phenomenon bifurcation on PES. As for a kind of bifurcationreactions which exist widely, according to the locations of bifurcate points, there arethree modes as follows:

Unimolecular and collisionally induced fragmentations of [CH2X2]+·

Organic Mass SpectrometryVolume 25, Issue 4 p. 247-248 Oms Letter Unimolecular and collisionally induced fragmentations of [CH2X2]+· O. Bortolini, O. Bortolini Dipartimento di Chimica, Universita' di Ferrara, Via Borsari 46, 44100 Ferrara, ItalySearch for more papers by this authorA. M. Maccioni, A. M. Maccioni CNR, Area di Ricerca, Corso Stati Uniti 4, 35100 Padova, Italy On leave from Istituto di Chimica Tossicologica e Farmaceutica, Universita' di Cagliari, ItalySearch for more papers by this authorR. Seraglia, R. Seraglia CNR, Area di Ricerca, Corso Stati Uniti 4, 35100 Padova, ItalySearch for more papers by this authorP. Traldi, P. Traldi CNR, Area di Ricerca, Corso Stati Uniti 4, 35100 Padova, ItalySearch for more papers by this author O. Bortolini, O. Bortolini Dipartimento di Chimica, Universita' di Ferrara, Via Borsari 46, 44100 Ferrara, ItalySearch for more papers by this authorA. M. Maccioni, A. M. Maccioni CNR, Area di Ricerca, Corso Stati Uniti 4, 35100 Padova, Italy On leave from Istituto di Chimica Tossicologica e Farmaceutica, Universita' di Cagliari, ItalySearch for more papers by this authorR. Seraglia, R. Seraglia CNR, Area di Ricerca, Corso Stati Uniti 4, 35100 Padova, ItalySearch for more papers by this authorP. Traldi, P. Traldi CNR, Area di Ricerca, Corso Stati Uniti 4, 35100 Padova, ItalySearch for more papers by this author First published: April 1990 https://doi.org/10.1002/oms.1210250416Citations: 8 AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article.Citing Literature Volume25, Issue4April 1990Pages 247-248 RelatedInformation

The energy transfer—isotope effect in thermal unimolecular reactions

(1978). The energy transfer—isotope effect in thermal unimolecular reactions. Molecular Physics: Vol. 36, No. 4, pp. 1241-1244.

On the relation between non adiabatic unimolecular reactions and radiationless processes

In this paper we present the results of a theoretical study of non adiabatic unimolecular dissociation processes with applications to the decomposition of N20(1X) to yield N2(12;9) and O(3P). Such unimolecular reactions which involve a change in the electronic state can be handled by the theory of thermally excited intramolecular radiationless decay processes in analogy to molecular predissociation and electronic relaxation in the statistical limit. General criteria were advanced for describing the decay probability of a single vibronic level in terms of Fermi's golden rule and for specifying the (high pressure) unimolecular rate constant in terms of a thermally averaged transition probability. The quantum mechanical rate constant for the non adiabatic reaction is characterized by a preexponential factor determined by the interstate coupling matrix element and by a temperature dependent activation energy. At low temperatures the activation energy is equal to the continuum onset, and the reaction involves a tunnelling process. In the high temperature limit a general demonstration of the Franck Condon principle for thermal reactions was provided, whereupon the non radiative transition occurs at the intersection of the potential surfaces. Numerical calculations for a one dimensional model system for the thermal decomposition of N20 were performed utilizing the semiclassical approximation and confirm our general conclusions. A two dimensional linear model has been developed representing the rate constant in terms of a convolution of two generalized line shape functions, which enabled us to study the distribution of vibrational energy among the diatomic N 2 molecules resulting from the thermal decomposition of N20. Some predictions concerning the determination of single level decay probabilities and vibrational distribution of the molecular products are presented. In dieser Arbeit werden die Ergebnisse einer theoretischen Untersuchung nicht adiabatischer unimolekularer Zerfallsreaktionen mitgeteilt und auf den Zerfall yon N20(12~) zu N2(12;g) und O(3p) angewandt. Solche unimolekularen Reaktionen, bei denen sich der Elektronenzustand ~indert, k6nnen mit der Theorie thermisch angeregter intramolekularer strahlungsloser Zerfallsprozesse in Analogie zu molekularer Pr~idissoziation und elektronischer Relaxation im statistischen Limit behandelt werden. Kriterien zur Beschreibung der Zerfallswahrscheinlichkeiten eines einzelnen Vibrationszustands unter Berficksichtigung yon Fermis Golden Rule werden entwickelt sowie die unimolekulare Geschwindigkeitskonstante (im Hochdruckbereich), wobei thermisch gemittelte fJbergangswahrscheinlichkeiten berficksichtigt werden, mitgeteilt. Die quantenmechanische Geschwindigkeitskonstante ffir die nicht adiabatische Reaktion wird durch einen pr~iexponentialen Faktor, der durch die Matrixelemente der Kopplung beider Zust~inde bestimmt ist und durch eine temperaturabh~ingige Aktivierungsenergie charakterisiert. Bei tiefer Temperatur stimmt die Aktivierungsenergie mit der Energie der Kontinuumsgrenze iiberein, die Reaktion verliiuft fiber einen Tunneleffekt. Ftir hohe Temperaturen wurde ein allgemeiner Beweis des Franek-Condon-Prinzips ffir thermische Reaktionen gegeben, wonach der strahlungslose Ubergang beim Schnittpunkt der Potentialfl~ichen auftritt. Rechnungen ffir ein eindimensionales Modell des NzO Zerfalls wurden in der semiklassischen N~iherung durchgeffihrt und bestiitigen unsere Folgerungen. Ein zweidimensionales Modell wurde entwickelt, das die Geschwindigkeitskonstante als Faltungsintegral zweier verallgemeinerter Linienformintegrale wiedergibt. Dadurch wurde es erm6glicht, die Verteilung der Vibrationsenergie auf die zweiatomigen N 2 Molektile, die bei dem thermischen Zerfall yon N20 enstehen, zu studieren. Einige Voraussagen tiber die Bestimmung der Zerfallswahrscheinlichkeiten eines Vibrationszustandes und die Vibrationsverteilung der molekularen Produkte werden mitgeteilt. * Present address: Institut ffir physikalische Chemie, Frankfurt, Robert-Mayer-StraBe 11,

Kinetics of the unimolecular dehydrofluorination of methyldifluoramine

Kinetics of the unimolecular dehydrofluorination of methyldifluoramine

The Thermal Unimolecular Isomerization of Methyl-d1 Isocyanide. Fall-Off and Inverse Isotope Effect1

The Thermal Unimolecular Isomerization of Methyl-d₁ Isocyanide. Fall-Off and Inverse Isotope Effect¹

A Test of the Radiation Hypothesis of Chemical Reaction

The viewpoint that thermal unimolecular reactions are to be considered as photochemical reactions with the activating frequencies lying in the infra-red region should be susceptible of experimental test by subjecting a system to radiation from an outside source, and determining whether or not the thermal reaction rate is thereby increased. The difficulties in such an experiment arise from two sources. First, there is the necessity of obtaining a high intensity of infra-red radiation, without at the same time raising the temperature of the reacting substance to such a point that the normal thermal rate is the preponderating effect. In the second place, the extreme opacity of almost all substances to all but the shortest of infra-red rays makes it difficult to find a window that will permit a high intensity over the wide range of frequencies which may be important in activating the molecules. For, since we do not know in what part of the infra-red spectrum the activating frequencies might lie, a conclusive test of the hypothesis should involve the use of all frequencies which are present to an appreciable extent in a hohlraum at the thermal reacting temperature.

CCLXIX.—Studies of dynamic isomerism. Part XII. The equations for two consecutive unimolecular changes

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