22 Result(s)
within
Steffen Jockusch
Chemistry
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Article
The red chlorophyll catabolite (RCC) is an inefficient sensitizer of singlet oxygen – photochemical studies of the methyl ester of RCC
The red chlorophyll catabolite (RCC) is a proposed cryptic intermediate of chlorophyll (Chl) breakdown in higher plants. Its accumulation in higher plants is believed to be metabolically suppressed, as RCC is ...
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Article
Photochemical conversion of a cytidine derivative to a thymidine analog via [2+2]-cycloaddition
Epigenetic information is encoded in the mammalian genome in the form of cytosines methylated at the 5 position. Cytosine methylation has multiple biological effects, but our understanding of these effects has...
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Article
Intra-molecular triplet energy transfer is a general approach to improve organic fluorophore photostability
Bright, long-lasting and non-phototoxic organic fluorophores are essential to the continued advancement of biological imaging. Traditional approaches towards achieving photostability, such as the removal of mo...
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Article
Photostabilization of endogenous porphyrins: excited state quenching by fused ring cyanoacrylates
Endogenous chromophores in human skin, when exposed to sunlight, generate harmful reactive oxygen species (ROS). Protoporphyrin IX (PpIX) is one of the common chromophores in human tissue. A series of aromatic...
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Article
Phototransformation of benzimidazole and thiabendazole inside cucurbit[8]uril
The phototransformation of benzimidazole (BZ) and of the benzimidazole pesticide thiabendazole (TBZ) was investigated in aqueous solution in the absence and presence of the supramolecular host cucurbit[8]uril ...
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Article
Photolysis of endoperoxides in the presence of nitroxides: a laser flash photolysis study with optical and ESR detection
Time-resolved electron paramagnetic resonance spectroscopy, transient absorption, and phosphorescence spectroscopy were used to investigate the spin polarization of a nitroxide free radical induced by interact...
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Article
Enantiospecific photochemical 6π-ring closure of α-substituted atropisomeric acrylanilides–role of alkali metal ions
Direct irradiation of atropisomeric α-substituted acrylanilides in the presence of alkali metal ions gave high ee values in the 3,4-dihydro-2-quinolin-2-one photoproduct, while in the absence of alkali metal i...
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Article
Photochemical studies of a fluorescent chlorophyll catabolite–source of bright blue fluorescence in plant tissue and efficient sensitizer of singlet oxygen
Fluorescent chlorophyll catabolites (FCCs) are fleeting intermediates of chlorophyll breakdown, which is seen as an enzyme controlled detoxification process of the chlorophylls in plants. However, some plants ...
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Article
CdSe/ZnS core shell quantum dot-based FRET binary oligonucleotide probes for detection of nucleic acids
We report the design, synthesis, and characterization of a binary oligonucleotide probe for selective DNA or RNA detection. The probe is based on fluorescence resonance energy transfer (FRET) from quantum dot ...
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Article
Photochemistry of 2-diphenylmethoxyacetophenone. Direct detection of a long-lived enol from a Norrish Type II photoreaction
Photolysis of 2-diphenylmethoxyacetophenone (1) in deaerated acetonitrile at room temperature is expected to proceed via Norrish Type II reaction to generate benzophenone (2) and acetophenone (4) as the main isol...
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Article
Adiabatic ring opening in tethered naphthalene and anthracene cycloadducts
The cycloadducts of tethered naphthalene and anthracene derivatives undergo photochemical ring opening to an electronically excited product with adiabatic yields up to 90%.
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Article
Physical and chemical quenching rates and their influence on stereoselective photooxygenation of oxazolidinone-functionalized enecarbamates
Physical and chemical quenching rate constants were measured for the reaction of singlet oxygen with oxazolidinonefunctionalized enecarbamates to investigate the role of vibrational deactivation in product ste...
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Article
Probing the photoreactivity of aryl chlorides with oxygen
Molecular oxygen was used to probe the mechanism of the phototransformation of chlorobenzene and 4-chloroanisole in organic solvents. Laser flash photolysis, electron paramagnetic resonance and product distributi...
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Article
Vibrational deactivation of singlet oxygen: does it play a role in stereoselectivity during photooxygenation?
Oxazolidinone-substituted enecarbamates offer a system to explore vibrational quenching and the strategic placement of CH bonds as a method for manipulating the stereoselectivity of photoreactions.
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Article
Singlet molecular oxygen by direct excitation
Direct excitation at 1064 nm and detection of singlet molecular oxygen at 1270 nm is made possible by the availability of powerful YAG-lasers and sensitive NIR photomultipliers. Singlet oxygen was generated in...
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Article
Chlorophyll derivatives as visual pigments for super vision in the red
The primary event in vision is light-initiated activation of visual pigments. All visual pigments consist of the protein opsin bound to 11-cis-retinal and are responsible for initiating the transformation of ligh...
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Article
Combinatorial fluorescence energy transfer molecular beacons for probing nucleic acid sequences
We report the design, synthesis, and characterization of molecular beacons (MB) consisting of three distinct fluorophores, 6-carboxyfluorescein (Fam), N,N,N′,N′-tetramethyl-6-carboxyrhodamine (Tam), and Cyanine-5...
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Article
Spectroscopic investigation of a FRET molecular beacon containing two fluorophores for probing DNA/RNA sequences†
We report the design, synthesis, and characterization of a molecular beacon (MB) consisting of two fluorescent dyes (Alexa 488 and RedX) for DNA and RNA analysis. In the absence of the target DNA or RNA the MB...
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Article
Direct measurement of the singlet oxygen lifetime in zeolites by near-IR phosphorescence
Time-resolved near-IR phosphorescence spectroscopy was employed to determine the lifetime of singlet oxygen in Y-zeolites and porous silica and it was found to depend strongly on the alumina content of the zeo...
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Article
In situ EPR investigation of the addition of persistent benzyl radicals to acrylates on ZSM-5 zeolites. Direct spectroscopic detection of the initial steps in a supramolecular photopolymerization
Photolysis of dibenzyl ketone derivatives adsorbed on ZSM-5 zeolites produces persistent benzyl radicals (initiator radicals), which add to methyl acrylates (monomers) to generate persistent adduct radicals. B...
