The Interaction of Riboflavin, FMN, and FAD with Various Metal Ions: The Riboflavin Catalyzed Photochemical Reduction of FeIII, and Photooxidation of FeII.

Zhou

Macro Chemistry & Physics

2012

Carbazole-substituted hydroxyethylcelluloses (Cz-HECs) are homogeneously synthesized by reacting hydroxyethylcellulose (HEC) with N -3 ′ -bromopropyl carbazole (Br-Cz). The structure of Cz-HECs is characterized with elemental analysis and NMR, and the DS of the carbazole is in the range 0.11-0.43, determined from nitrogen content. The fl uorescent properties of Cz-HECs are measured using a spectrofl uorimeter. The results show that the fl uorescence lifetime increases as the DS increases, and the fl uorescent intensity of Cz-HECs is stronger than that of Br-Cz. All samples exhibit concentration self-quenching properties. The addition of acrylonitrile, as an electron acceptor, quenches the emission spectra of Cz-HECs, and the fl uorescence quenching is found to be a dynamic quenching by analyzing with the Stern-Volmer equation.

Section: Fluorescent Propertiesmentioning

confidence: 99%

Synthesis and Fluorescent Properties of Carbazole‐Substituted Hydroxyethylcelluloses

Zhou

Macro Chemistry & Physics

2012

“…A number of biochemical processes of avins are based on their strong interactions with coordinating metal ions. [6][7][8][9][10][11][12][13][14][15] Due to their importance, numerous studies have characterized the absorption properties of avins by a variety of spectroscopies in the condensed phase (absorption, emission, time-resolved spectroscopy) [16][17][18][19] and quantum chemical calculations. 16,[20][21][22][23][24][25] These studies reveal that the excited-state photochemistry and absorption of avins from the ground electronic state (S 0 ) are controlled by optically bright pp* excitations of the aromatic p electron system and essentially dark np* states involving the excitation of electrons from in-plane lone pairs of the various O and N heteroatoms.…”

Section: Introductionmentioning

confidence: 99%

Effect of alkali ions on optical properties of flavins: vibronic spectra of cryogenic M⁺lumiflavin complexes (M = Li–Cs)

et al. 2019

Contrast Media & Molecular

“…In general, fluorescence quenching happens through a variety of mechanisms, like ground‐state complexation,25 charge‐transfer phenomena,26 electric energy transfer,27 fluorescence resonance energy transfer (FRET),28 heavy atom effect,29 etc. The Carbazole derivative has an electron donor group, which can cause a charge transfer phenomenon with the addition of an electron acceptor.…”

Section: Resultsmentioning

confidence: 99%

CMR 2005: 9.05: Magnetic labeling and in vivo tracking of embryonic stem cells: efficacy, biological effects, high‐field detection limits and long‐term results

Sieland¹,

Stroh²,

Faber³

et al. 2006

Rationale and Objective: Conventional MRI techniques to track ferumoxide-labeled stem cells rely on the detection of signal voids, which often mimic other image artifacts. Several bright marker imaging techniques have been proposed (1,2), but are either poorly suited for in vivo cardiac imaging or have limited utility owing to reduced signalto-noise ratios. Furthermore, these techniques are not compatible with MR device tracking for transcatheter therapeutics. We present here a novel technique, called Inversion-Recovery with ON water resonance suppression (IRON), to perform positive enhancement of magnetic nanoparticles and also allow the visualization of conventional interventional devices such as stents and catheters. Methods: Mesenchymal stem cells (MSCs) were isolated from bone marrow and MR-labeled with 25 mg Fe/mL ferumoxides and 375 ng/L poly-L-lysine for 24 h as previously described (3,4). IRON imaging of six different concentrations of MR-labeled MSCs, oil and coagulated blood was performed on a 1.5 T MR scanner. The IRON pulse sequence consists of: (i) two non-selective-inversion recovery pulses separated by an interval TI to null fat; (ii) a spatial presaturation radiofrequency pulse centered on the water frequency to suppress all signal except the protons locally dephased by field inhomogeneities created by non-diamagnetic objects; and (iii) a turbo spin-echo image acquisition. This results in an image consisting of bright signal from both devices and magnetic nanoparticles while suppressing all of the surrounding tissue including fat. In vivo studies were performed in dogs with and without myocardial infarction and a New Zealand White rabbit subjected to hindlimb ischemia. In one canine study, labeled MSCs ($7Â10 6 MSCs per injection) were injected transmyocardially using a transcatheter approach under MR fluoroscopy to target MSCs to the infarcted myocardium. IRON imaging of MR-labeled MSCs was compared with conventional gradient-echo (GRE) images. Using a roadmap anatomical image, passive catheter tracking was performed using a real-time IRON gradient and spin-echo (GRASE) sequence in another dog for stent deployment. The volume of tissue enhancement with IRON after direct intramuscular MR-labeled MSCs ($7Â10 6 MSCs per injection) in the rabbit hindlimb was compared with intramyocardial delivery in the dog. Results: A high correlation between MR-labeled MSC concentration and volume of signal enhancement was obtained using in vitro IRON imaging ( y ¼ 149x AE 20, R 2 ¼ 0.99) with adequate fat suppression. Expected dipole enhancement of each MSCs concentration and MSC injection sites in the infarcted heart, but not clotted blood, was demonstrated with a 3D IRON sequence. On 2D IRON images, the volume of signal enhancement could be dynamically altered by altering the bandwidth of the on water suppression pulse. However, in all cases, the volume of positive enhancement from direct skeletal intramuscular injections were larger than that from equivalent intramyocardial injections. Successful iliac stainle...