Biomedical subjects

Juan Feng

Publications and source records attributed to Juan Feng.

21 records · Page 2Linked to original sources

PubMed2002

Effect of TiO2 colloids on the fluorescence behavior of two cyanine dyes.

The photophysical properties of two typical cyanine dyes [3,3'-diethyl-9-methyl-thiacarbocyanine iodide (dye A) and anhydro-3,3'-disulfopropyl-5,5'-diphenyl-9-ethyloxacarbocyanine hydroxide (dye B)] in the absence and presence of TiO(2) colloids have been investigated by UV-visible spectroscopy, (1)H-NMR spectroscopy, fluorescence spectroscopy, fluorescence lifetime measurements, and ESR measurements. It was found from the absorption spectra and NMR results that there are two isomers in the ground state of these dyes. Steady-state fluorescence spectra show that the fluorescence intensities of dye A and dye B are enhanced and quenched by TiO(2) colloids, respectively. Time-resolved fluorescence lifetime measurements indicate that the lifetimes of dye A and dye B in the presence of TiO(2) colloids are longer and shorter than those obtained in the absence of TiO(2) colloids, respectively. ESR measurements demonstrate that the electron transfer efficiency from (1)dye B* to the conduction band of TiO(2) is much larger than that from (1)dye A* to the conduction band of TiO(2). The different fluorescence behavior of dye A and dye B can be intepreted in terms of whether phi(Tr,nr)(0)-phi(Tr,nr) (the reduction of the quantum yield for radiationless transition in the excited singlet state (1)dye* caused by the TiO(2) colloids) is larger or smaller than phi(ET) (the quantum yield of electron transfer from (1)dye* to the conduction band of TiO(2) colloids).

Journal Article↗

PubMed2002

[Pathogenesis of optic-spinal MS].

We reviewed the clinical and immunological features of optic-spinal multiple sclerosis (OSMS), or relapsing neuromyelitis optica. OSMS has collected much attention as to whether it is a distinct entity from conventional MS (CMS). However, OSMS plus minor cerebral and brainstem/cerebellar involvement and the later conversion into CMS had been a diagnostic dilemma. To overcome such problems and delineate the features of OSMS, we analyzed 'Pure OSMS' with which patients had only relapsing optic neuritis and myelitis clinically and consistently normal brain MRI during 5 years or longer follow-ups. As a result, we found that this type of MS was characterized by a definite female preponderance and negative oligoclonal IgG bands (OB), although 'Pure OSMS' was heterogeneous with regards to the clinical severity and HLA class II alleles. Previously reported immunological data in OSMS include negative OB and no elevation of IL-10 or matrix metalloproteinase-9 in the cerebrospinal fluid (CSF) during relapses. In addition, we recently demonstrated that the CCR5+ Th1 cell subset in CSF during relapses, which significantly increased in CMS, remained low in OSMS. These unique clinical and immunological findings probably relate to fundamental differences in the pathogeneses of OSMS and CMS and deserve further characterization.

Female↗

PubMedDate not supplied

Radical cation generation from singlet and triplet excited states of all-trans-lycopene in chloroform.

On direct photoexcitation, subpicosecond time-resolved absorption spectroscopy revealed that the 1B(u)-type singlet excited state of all-trans-lycopene in chloroform was about seven times more efficient than all-trans-beta-carotene in generating the radical cation. The time constant of radical cation generation from the 1B(u)-type state was found to be approximately 0.14 ps, a value that was comparable for the two carotenoids. On anthracene-sensitized triplet excitation, radical cation generation was found to be much less efficient for lycopene than for beta-carotene. A slow rising phase (20-30 micros) in the bleaching of ground-state absorption was common for both lycopene and beta-carotene in chloroform and was ascribed to an efficient secondary reaction with a solvent radical leading to the formation of carotenoid radical cations. The reverse ordering in the tendency of the excited states of different multiplicities for the two carotenoids to generate radical cations is discussed in relation to the two carotenoids as scavengers of free radicals.

Carotenoids↗