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Galkin, O. N., & Terenetskaya, I. P. (1999). ‘vitamin d’ biodosimeter: Basic characteristics and potential applications. Journal of Photochemistry and Photobiology B: Biology, 53(1–3), 12–19. 
Added by: Sarina (2017-01-20 15:52:46)   Last edited by: Sarina (2022-11-19 17:32:40)
Resource type: Journal Article
DOI: http://dx.doi.org/10.1016/S1011-1344(99)00115-3
ID no. (ISBN etc.): 1011-1344
BibTeX citation key: Galkin1999
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Categories: Englisch = English
Keywords: Mathematik = Mathematics, UVBreitband = UVBroadband, Vitamin D = Vitamin D
Creators: Galkin, Terenetskaya
Collection: Journal of Photochemistry and Photobiology B: Biology
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Popularity index: 15.5%
Meine Sichtweise (Keine vollständige Zusammenfassung des Artikels! Meine Meinung muss nicht mit der Meinung der Autoren übereinstimmen! Bitte lesen Sie auch die Originalarbeit!)    Wird eine Lösung von 7DHC in Ethanol mit Sonnenlicht bestrahlt, so wandelt sich ein Teil in die diversen bekannten Photoprodukte um. Die spektrale Transmission der Lösung ändert sich dabei und auch die Transmission bei 285 nm. Diese Änderung der Transmission kann als Dosimeter verwendet werden.

 

Enthält alle gekoppelten Differentialgleichungen, Absorptionsspektren und Quanteneffizienzen für die Berechnung des Vitamin-D3-Gleichgewichts.

Eq 2:
Photoisomer concentrations Ci
i = 1: 7DHC, 2: preD3, 3:Tach, 4:Lumi, 5:Tox
dC1/dt = int dλ I∗(λ) [−ε1(λ)C1φ12 + ε2(λ)C2φ21]
dC2/dt = int dλ I∗(λ) [−ε2(λ)C2φ21 + ε1(λ)C1φ12
− ε2(λ)C2φ23 + ε3(λ)C3φ32
− ε2(λ)C2φ24 + ε4(λ)C4φ42
− ε2(λ)C2φ25]
dC3/dt = int dλ I∗(λ) [−ε3(λ)C3φ32 + ε2(λ)C2φ23]
dC4/dt = int dλ I∗(λ) [−ε4(λ)C4φ42 + ε2(λ)C2φ24]
dC5/dt = int dλ I∗(λ) [ε2(λ)C2φ25]

Eq. 3, ref. to [17]
photokinetic factor
I∗(λ) = I0(λ) * [ 1 − 10^[−D(λ)] ]/D(λ)

Eq. 1
total absorbance of the solution
D(λ) = l sum(i=1:5) εi(λ) Ci

quantum yields φij
for the reversible photoreactions: Ref[18]
for the irreversible photoconversion: Ref[19]
Fig 1
φ12 = 0.26 7DHC → preD3
φ21 = 0.015 preD3 → 7DHC
φ23 = 0.48 preD3 → Tach
φ32 = 0.10 Tach → preD3
φ24 = 0.42 preD3 → Lumi
φ42 = 0.03 Lumi → preD3
φ25 = 0.039 preD3 → Tox

absorbance spectra εi(λ)
Fig 2


At t=0 the initial conditions for the concentrations are C1=100% and C2=C3=C4=C5=0

Fig. 4 shows an example of calculated kinetics under monochromatic irradiation at the wavelengths 254, 282, 296 and 305 nm. The calculations were performed for the intensity I0 = 1 mW/cm²/nm, initial concentration of provitamin D (7DHC) C0 = 0.002% and l = 0.5 cm


Added by: Sarina  Last edited by: Sarina
Abstract
The biologically important process of endogenous synthesis of vitamin D under {UV} solar irradiation is widespread in the biosphere and inherent to most animals and plants. A new method of biological dosimetry of {UV} radiation based on an in vitro model of vitamin D synthesis (‘D-dosimeter’) is discussed. Unlike the vast majority of biodosimeters, the action of which depends on the {UV} sensitivity of {DNA} and thus reflects damaging effects of {UV} radiation, the process of vitamin D synthesis is beneficial by its nature. To date, the complex network of photo- and thermoreactions of vitamin D synthesis in vitro is well understood, and an adequate mathematical model is available, ensuring a link between biological and physical units. Original spectral analysis of the multicomponent photoisomer mixture has been specially designed to provide the most effective use of the D-dosimeter in situ. Spectral selectivity (exceptional sensitivity of certain parameters to the spectral composition of {UV} radiation) extends the usefulness of the method.
  
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