The mitochondrial function was impaired in APP knockout mouse embryo fibroblast cells

The amyloid precursor protein (APP) is recognized as the source of Aβ, which plays an important role in Alzheimer’s disease. However, the biological function of APP is obscure. Previous studies showed that mitochondria could be a target of APP. In this work, APP knockout mouse embryo fibroblast (MEF) cells were used to test if APP plays any role in maintaining the mitochondrial function. As the result, APP knockout MEF cells (APP-/- cells) showed the abnormal mitochondrial function, including slower cell proliferation, lower mitochondrial membrane potential, lower intracellular ROS, higher mitochondrial membrane fluidity and lower cytochrome c oxidase activity than their wild-type counterparts. However, no change was found in the amount of mitochondria in MEF APP-/-cells.

Endogenously generated amyloid β increases membrane fluidity in neural 2a cells

The effect of endogenously generated amyloid β on membrane fluidity was investigated in Neural 2a cells stably expressing Swedish mutant amyloid precursor protein (APPswe). Membrane fluidity was studied by fluorescence polarizability using 1,6-Diphenyl-1,3,5-Hexatriene (DPH) as the fluorescence probe. It was found that the membrane fluidity in APPswe cells was significantly higher than that in its wild type counterparts. Alleviating the effect of amyloid β either by γ secretase activity inhibition or by amyloid antibody treatment decreased membrane fluidity, which indicated an important role of amyloid β in increasing membrane fluidity. Treatment using amyloid β channel blocker, tromethamine and NA4 suggested that channel formed by amyloid β on the cell membrane is a way through which amyloid β takes its membrane fluidizing effect.

The photodamage process of pigments and proteins of PSI complexes from Spinacia Oleracea L.

Purified PSI complexes from Spinacia Oleracea L. were exposed to the strong light (PFD=2300μmol m-2s-1) for various period. Along with the illumination the photo-damage process of pigments and proteins of PSI complexes was investigated using absorption, fluorescence, circular dichroism (CD) spectroscopy and SDS-PAGE. It was found from the optical absorption spectra that the maximal ab-sorbance of PSI complexes decreased and maximal peaks blue-shifted during the illumination, and the forth derivative spectra demonstrated that the absorbance decreasing at red region mainly resulted from the aborbance decreasing of the long wavelength Chla, implying that the long-wavelength Chla was readily to be bleached. The CD signals contributed by LHCI decreased more rapidly than other CD signals con-tributed by Chla and Carotenoid, indicating that the LHCI was more sensitive to light than core complexes. It was observed by SDS-PAGE that some small polypeptides of PSI complexes were damaged earlier than reaction

Simulation for the primary electronic donor of photosystem II in vitro

Histidine coordinated to Chl a is a distinct characteristic of Chl a in vivo. By usinghistidine analogue of 1-methylimidazole (C4H6N2) and measuring the UV/vis absorption, CD and MCD spectra of the interaction between C4H6N2and Chl a in CCI4, we have obtained that: (i) In pure CCI4 solvent, Chl a molecule is in five-coordinate state, and two Chl a molecules form an asymmetric compact-dimer with strong coupling interaction. We propose that the two Chl a molecules are connected by two unequally coordinated Mg-O bonds (the two oxygen atoms come from the C=O of C131 keto and C17 ester, respectively); (ii) when the molar ratio of C4H6N2/Chl a is 0.5 or 1 (corresponding to 2Chl a #1C4H6N2 and 2Chl a ·2C4H6N2, respectively), significant changes have been observed in the absorption, CD and MCD spectra, which indicate that the Chl a remains in dimer form, but the coupling interaction between them reduces greatly. We postulate that C4H6N2 replaces the ligation of C=O of C17 ester and C131 keto to Mg atoms

Amyloid precursor protein-mediated modulation of capacitive calcium entry

Alzheimer's disease(AD) is a progressive neurodegenerative disorder.In the present study,the function of amyloid precursor protein(APP) in modulating capacitive calcium entry(CCE),a refilling mechanism for depleted intracellular calcium stores,was investigated.CCE in neural 2a(N2a) cells stably expressing wild-type human APP was lower than in wild-type N2a cells,while CCE in APP knockout mouse embryonic fibroblast(MEF) cells was higher than in their wild-type counterparts.We demonstrate that wild-type APP depresses CCE.Furthermore,using N2a cells transfected with C-terminal APP fragments,we show that these fragments anchored in the cell membrane play an important role in CCE depression.

Circular Dichroism Analysis of the Effect of Metallic Ions on Structure of Collagen Molecules

Circular dichroism spectroscopy was used to study the effect of metallic ions such as Fe 3+,Al 3+and Ca 2+on the structure of collagen molecules.The results showed the effect of the ions was similar to that of thermal denaturation but not as strong.On the basis of the obtained results,the mechanism used by the metallic ions to protect the biovalves from calcification may be explained as follows.Collagen is the dominant component of the biovalves.Pretreating the biovalves with glutaraldehyde caused many amino acid residues in collagen molecules to cross link.This leads to a decrease in the total positive charge in the collagen molecules and a relative surplus of free carboxyl groups.The trivalent metallic ions such as Fe 3+preferentially bound with negatively charged carboxyl groups of collagen molecules,which caused the superhelix of the collagen to be loose and random.This improved the mechanical properties of the biovalve and neutralized surplus free carboxyl groups caused by the glutaraldehyde treatment,closed the sites where the Ca 2+was bound.Also,it effectively protected the biovalves from calcification.