Intramolekulare Wasserstoffverschiebung in der Hexosephosphatisomerase-Reaktion bei der photosynthetischen Stärkebildung in Chlorella

1966 ◽  
Vol 21 (6) ◽  
pp. 557-562 ◽  
Author(s):  
Hans-Dieter Dorrer ◽  
Carl Fedtke ◽  
Achim Trebst
Keyword(s):  
Hydrogen Transfer ◽  
Chlorella Pyrenoidosa ◽  
Starch Biosynthesis ◽  
Strong Indication ◽  
Exchange Reactions ◽  
Carbon 14 ◽  
Multienzyme System ◽  
Intramolecular Hydrogen

Chlorella pyrenoidosa was illuminated in the presence of glucose and fructose echa having carbon-14 and tritium markers. Starch and sucrose were degraded to obtain the intramulocular distribution of 14C and tritium. Glucose-1-14C-2-T was incorporated into the glucose of starch and into the glucose moiety of sucrose without change of the T/14C ratio. Fructose-1-14C-1-T (labelled stereospecifically in the isomerase position) was incorporated into starch, yielding predominately glucose-1-14C-2-T, whereas fructose-1-14C-1-T (labelled in the nonisomerase position) gave mainly glucose-1-14C-1-T.The results, in particular the transfer of tritium from C-1 of fructose to C-2 of glucose, are interpreted as being a strong indication for an intramolecular hydrogen transfer in the hexosephosphat-isomerase reaction in a multienzyme system of the photosynthetic starch biosynthesis in vivo, shielding the hexoses of T-exchange reactions with water.

scholarly journals Excited-State Intramolecular Hydrogen Transfer of Compact Molecules Controls Amyloid Aggregation Profiles

2021 ◽  
Author(s):  
Mannkyu Hong ◽  
Mingeun Kim ◽  
Jiwon Yoon ◽  
Seung-Hee Lee ◽  
Mu-Hyun Baik ◽  
...  
Keyword(s):  
Excited State ◽  
Hydrogen Transfer ◽  
Experimental Studies ◽  
Amyloid Β ◽  
Molecular Structures ◽  
Hydroxyl Groups ◽  
Chemical Reagents ◽  
Amyloidogenic Peptides ◽  
Intramolecular Hydrogen

Designing new chromophores by tuning their molecular structures and optimizing their photophysical properties leads to suitable photochromic features. Herein, we report a series of anthraquinone (AQ)-based photosensitizers that undergoes excited-state intramolecular hydrogen transfer and effectively oxidizes amyloidogenic peptides, which significantly affects the subsequent aggregation pathways. DFT calculations showed that the appropriate position of the hydroxyl groups in the AQ backbone and the consequent intramolecular hydrogen transfer can facilitate the energy transfer to triplet oxygen. Biochemical and biophysical investigations confirmed that these photoactive chemical reagents are able to oxidatively modify both metal-free amyloid-β (Aβ) and metal-bound Aβ, thereby redirecting their on-pathway aggregation into off-pathway as well as disassembling their pre-formed aggregates. Moreover, the in vivo histochemical analysis of Aβ species produced upon photoactivation of the most promising candidate demonstrated that they do not aggregate into toxic oligomeric or fibrillar aggregates in the brain. Overall, our combined computational and experimental studies validate a light-based approach for designing small molecules as chemical reagents targeting and controlling amyloidogenic peptides associated with neurodegenerative disorders.

Reductive intramolecular hydrogen transfer in a d8 metal hydride promoted by carbon monoxide addition. An experimental study and its theoretical implications

1984 ◽  
Vol 23 (7) ◽  
pp. 922-929 ◽  
Author(s):  
Franco Cecconi ◽  
Carlo A. Ghilardi ◽  
Paolo Innocenti ◽  
Carlo Mealli ◽  
Stefano Midollini ◽  
...  
Keyword(s):  
Experimental Study ◽  
Carbon Monoxide ◽  
Metal Hydride ◽  
Hydrogen Transfer ◽  
Intramolecular Hydrogen

Theoretical study on intramolecular hydrogen transfer of 1-methylbutyl peroxide radical

2013 ◽  
Vol 53 (6) ◽  
pp. 431-437 ◽  
Author(s):  
Min Li ◽  
Li-Feng Xie ◽  
Xue-Hai Ju ◽  
Feng-Qi Zhao
Keyword(s):  
Hydrogen Transfer ◽  
Theoretical Study ◽  
Peroxide Radical ◽  
Intramolecular Hydrogen

A Study on the Possible Occurrence of Base-Exchange Reactions in Vivo

1978 ◽  
pp. 319-325 ◽  
Author(s):  
P. Orlando ◽  
G. Arienti ◽  
P. Saracino ◽  
L. Corazzi ◽  
P. Massari ◽  
...  
Keyword(s):  
Exchange Reactions ◽  
Base Exchange

scholarly journals Fast Isotopic Exchange between Mitochondria and Cytosol in Brain Revealed by Relayed 13C Magnetization Transfer Spectroscopy

2009 ◽  
Vol 29 (4) ◽  
pp. 661-669 ◽  
Author(s):  
Jehoon Yang ◽  
Su Xu ◽  
Jun Shen
Keyword(s):  
Isotopic Exchange ◽  
Tricarboxylic Acid Cycle ◽  
Magnetization Transfer ◽  
Tricarboxylic Acid ◽  
Transfer Effect ◽  
Resonance Spectroscopy ◽  
Exchange Reactions ◽  
Acid Cycle ◽  
Longitudinal Relaxation

In vivo13C magnetic resonance spectroscopy has been applied to studying brain metabolic processes by measuring 13C label incorporation into cytosolic pools such as glutamate and aspartate. However, the rate of exchange between mitochondrial α-ketoglutarate/oxaloacetate and cytosolic glutamate/aspartate ( Vx) extracted from metabolic modeling has been controversial. Because brain fumarase is exclusively located in the mitochondria, and mitochondrial fumarate is connected to cytosolic aspartate through a chain of fast exchange reactions, it is possible to directly measure Vx from the four-carbon side of the tricarboxylic acid cycle by magnetization transfer. In isoflurane-anesthetized adult rat brain, a relayed 13C magnetization transfer effect on cytosolic aspartate C2 at 53.2ppm was detected after extensive signal averaging with fumarate C2 at 136.1ppm irradiated using selective radiofrequency pulses. Quantitative analysis using Bloch–McConnell equations and a four-site exchange model found that VxE13–19 µmol per g per min (≫ VTCA, the tricarboxylic acid cycle rate) when the longitudinal relaxation time of malate C2 was assumed to be within ±33% of that of aspartate C2. If VxE VTCA, the isotopic exchange between mitochondria and cytosol would be too slow on the time scale of 13C longitudinal relaxation to cause a detectable magnetization transfer effect.

Biosynthesis of Nitrogenous Phospholipids in Spinach Leaves

1974 ◽  
Vol 52 (6) ◽  
pp. 469-482 ◽  
Author(s):  
M. O. Marshall ◽  
M. Kates
Keyword(s):  
Microsomal Fraction ◽  
Enzyme System ◽  
Supernatant Fraction ◽  
Exchange Reactions ◽  
Methylation Pathway ◽  
Ethanolamine Kinase ◽  
Spinach Leaves

Pathways for biosynthesis of phosphatidylserine (PS), phosphatidylethanolamine (PE), and phosphatidylcholine (PC), in spinach leaves have been studied both in vivo (whole leaves and leaf slices) and in vitro (cell-free leaf fractions). Biosynthesis of PS was shown to occur by the action of a particle-bound CDP-diglyceride: serine phosphatidyltransferase, and PE by the action of a PS-decarboxylase localized in the 100 000 × g supernatant fraction. PE was also formed by the operation of the CDP-ethanolamine:diglyceride phosphorylethanolamine transferase, localized in the microsomal fraction. The presence of ethanolamine kinase required for formation of phosphorylethanolamine was demonstrated in vitro, but not the presence of CTP:phosphorylethanolamine cytidyltransferase; however, the latter is presumed present on the basis of in vivo results. Operation of the methylation pathway for biosynthesis of PC was established in vivo, and direct methylation of phosphatidyl-N-methylethanolamine to phosphatidyl-N,N-dimethylethanolamine (PE-diMe) and of PE-diME to PC by S-adenosylmethionine was demonstrated with a particulate enzyme system localized in the microsomal fraction; direct methylation of PE itself could not be shown in this system. PC was also synthesized by the CDP-choline:diglyceride phosphorylcholine transferase system localized in the microsomal fraction. Synthesis of PE and PC by Ca2+-stimulated exchange reactions with ethanolamine and choline, respectively, could be demonstrated, but at low rates. However, no synthesis of PS by exchange reactions with serine could be detected.

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