- Interaction of Hydrophobic Probes with Serum Albumin-Influence of the Side Chain and Exciplex Formation at the Binding Site
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Novel fluorescent probes of the generic formula Ar-(CH2)n-NH3+ (Scheme I, Ar=9-anthryl or 3-pyrenyl) were synthesized, and their binding properties with bovine serum albumin (BSA) have been evaluated.The anthryl probes 9-anthrylmethylamine hydrochloride (AMAC), N-ethyl (9-anthryl)methylamine hydrochloride (N-Et-AMAC), and 3-(9-anthryl)propylamine hydrochloride (APAC), showed small changes in their absorption spectra upon binding to BSA, whereas the pyrenyl analog, 4-(1-pyrenyl)butylamine hydrochloride (PBAC), showed a 5-nm red shift and an increase in the extinction coefficient at the peak positions.Such a red shift and increase in the intensity of the absorption transitions are consistent with binding of PBAC to hydrophobic sites on the protein.The fluorescence spectra of the anthryl and pyrenyl analogs exhibit different trends.The anthryl analog emission was quenched very effectively by increaseing amounts of BSA (KSV ca. 2.6 E3 M-1).In contrast, PBAC emission was quenched at low BSA concentration whereas at higher concentrations of the protein the emission was enhanced.The fluorescence decays of the anthryl probes bound to the protein can be described by a short-lived and a long-lived component (10.6 and 6.7 ns for AMAC, 10.3 and 5.1 ns for APAC, 14.6 and 7.8 ns for N-Et-AMAC) indicative of at least two types of binding sites.In the case of PBAC , a third component was observed at probe:protein ratios higher than 1:5, which may be due to an exciplex formed at the binding site.Data from the equilibrium dialysis experiments indicate that the order of protein binding affinity of these probes is PBAC >> APAC > N-Et-AMAC > AMAC.Steady-state and time-resolved fluorescence quenching experiments with potassium iodide confirmed the above trend in the binding affinities.Upon binding to BSA, APAC and PBAC emission was extensively protected whereas only moderate protection has been observed for N-Et-AMAC and AMAC.A comparison of the binding properties of AMAC and N-Et-AMAC shows that increased distance of separation between the hydrophobic moiety and cationic function enhances the protein binding affinity.Additionally, comparison of APAC with PBAC revealed the strong role of hydrophobic groups in the binding interactions.Therefore, the protein binding affinity of these probes depends on the degree of hydrophobicity of the aromatic moiety and on the length of the linker separating the hydrophobic group from the cationic function.
- Kumar, C. Vijaya,Tolosa, Leah M.
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- Reductive amination reaction for the functionalization of cellulose nanocrystals
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Cellulose nanocrystals (CNCs) represent intriguing biopolymeric nanocrystalline materials, that are biocompatible, sustainable and renewable, can be chemically functionalized and are endowed with exceptional mechanical properties. Recently, studies have been performed to prepare CNCs with extraordinary photophysical properties, also by means of their functionalization with organic light-emitting fluorophores. In this paper, we used the reductive amination reaction to chemically bind 4-(1-pyrenyl)butanamine selectively to the reducing termini of sulfated or neutral CNCs (S_CNC and N_CNC) obtained from sulfuric acid or hydrochloric acid hydrolysis. The functionalization reaction is simple and straightforward, and it induces the appearance of the typical pyrene emission profile in the functionalized materials. After a characterization of the new materials performed by ATR-FTIR and fluorescence spectroscopies, we demonstrate luminescence quenching of the decorated N_CNC by copper (II) sulfate, hypothesizing for these new functionalized materials an application in water purification technologies.
- Babudri, Francesco,Capodieci, Laura,Colaprico, Erica,Giannelli, Rosa,Omar, Omar Hassan,Operamolla, Alessandra
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- Enhanced H-bonding and π-stacking in DNA: A potent duplex-stabilizing and mismatch sensing nucleobase analogue
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X-pyrene is a new nucleic acid duplex stabilizing cytosine analogue that combines enhanced π-stacking, hydrogen bonding and electrostatic interactions to greatly increase the stability of bulged DNA duplexes and DNA/RNA hybrids. X-pyrene is highly selective for guanine as a partner and duplex stability is reduced dramatically when X-pyrene or a neighboring base is mismatched. An NMR study indicates that the pyrene moiety stacks within the helix, and large changes in fluorescence emission on duplex formation are consistent with this. These favorable properties make X-pyrene a promising cytosine analogue for use in a variety of biological applications.
- Lou, Chenguang,Dallmann, Andre,Marafini, Pietro,Gao, Rachel,Brown, Tom
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p. 3836 - 3844
(2014/11/07)
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- Fluorescent sensors for organophosphorus nerve agent mimics
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We present a small molecule sensor that provides an optical response to the presence of an organophosphorus (OP)-containing nerve agent mimic. The design contains three key features: a primary alcohol, a tertiary amine in close proximity to the alcohol, and a fluorescent group used as the optical readout. In the sensor's rest state, the lone pair of electrons of the basic amine quenches the fluorescence of the nearby fluorophore through photoinduced electron transfer (PET). Exposure to an OP nerve agent mimic triggers phosphorylation of the primary alcohol followed rapidly by an intramolecular substitution reaction as the amine displaces the created phosphate. The quaternized ammonium salt produced by this cyclization reaction no longer possesses a lone pair of electrons, and a fluorescence readout is observed as the nonradiative PET quenching pathway of the fluorophore is shut down. Copyright
- Dale, Trevor J.,Rebek Jr., Julius
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p. 4500 - 4501
(2007/10/03)
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- Synthesis of 4-aryl-butylamine fluorescent probes
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A short synthesis of the fluorescent probes 4-(9-anthracenyl)butyl amine (three steps), 4-(9-phenanthrenyl)butyl amine (three steps) and 4-(1-pyrenyl)butyl amine (two steps) without chromatographic purification is described.
- Afonso, Carlos A. M.,Farinha
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p. 584 - 586
(2007/10/03)
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