Optical reagon of EM spectrum
Biological effects of light
UV-B
UV-C
200-280 280-315
nm
nm
Steps leading to the photobiological alterations
UV-A
315-400 nm
Penetration distance of light into skin
UV-C UV-B UV-A
Photophysical processe
(absorption of light)
Photochemical reaction
200
300
400
VIS
600
IR
800
1200 10600 nm
epidermis
dermis
Photobiological processes
subcutis
Absorption of light is a prerequisite of
photobiological processes
Penetration depth is wavelength dependent
Penetration distance of light into eye
Ligth absorbers (chromophores)
in human tissues
Exogenous
Endogenous
retina
e.g. nucleic acids
proteins
melanin
opsins
lens
vitreous
e.g. food coloring dyes
cosmetics
drugs
cornea
Absorption spectra of endogenous chromophores (1)
Absorption spectra of endogenous chromophores (2)
haemoglobin
Relative Absorbance
Relative Absorbance
DNA bases
β-carotin
Melanin
Aromatic amino acids
Wavelength(nm)
Wavelength(nm)
Direct photochemical reactions
Biological consequences of DNA damages in E. coli
UVB - UVC
DNA relative absorbance
Relative frequency of mutations
e.g. Formation of DNA damages
Wavelength(nm)
Efficiency varies with the wavelength
Thymine
Thymine dimer
Mutations are induced by the photons absorbed in DNA
Reciprocity?
J(λ) [J / s m2] x t [s] = D(λ) [J / m2]
The results depends only on the incident dose ( D(λ) )
or
on J and on t separately
Reciprocity is valid for photochemical reactions but not for
photobiological results.
Examples for the photobiolgical
effects of light
Beneficial vs detrimental effects
Spatial distribution of alterations
Local effects
in the skin
in the eye
examples
examples
Vision
Vitamin-D production
Pigmentation
Daily and annual rhythms
Terapeutic applications
target regions of therapies
Sunburn
Wrinkles
Age related pigmentation
Skin cancer
Immuno-suppression
Systemic effects
Temporal distribution of alterations
Penetration distance and localization of
damages
Short term: sunburn
in the eye
immuno-suppression
UV-C
Long terme: age related wrinkles
age related pigmentation
skin Cancer
200
UV-B
UV-A
300
VIS
400
IR
800
corneal burns
(photokeratitis)
1200
corneal burns
kötöhártyagyulladás
(conjunctivitis)
cataracta
cataracta
vision
retinal burns
10600 nm
Daily and annual rhythms
in the skin
UV-C
200
UV-B
UV-A
300
VIS
400
e.g.
IR
800
1200
10600 nm
temperature
hormon production
digestion
sliping / wake
sunburn
(erythema)
pigmentation
cancer
Burning of the skin
Light may play a role on the circadian rhythm
Seasonal Affective Disorder (SAD)
fényhiányos depresszió
A new type of photosensitive cells (RGC) in retina
Pigment
Background of SAD : hight serum level of melatonin
epithelium
Rhodes
and
Cones
Melatonin level is regulated by the intensity, wavelength and time
Optic
nerve
period of the incident light into the eye
Melatonin level regulation is independent of vision – blindness do
not oppose this process
Network of retinal
ganglion cells
RGC axons
to related
brain
structures
Hypotalamus
Large RGCs contain melanopsin
Seasonal Affective Disorder (SAD)
Question of the week
Treatment
Light source: 5000 K incandescent lamp (λmax = 580 nm)
with UV filter
(Sun: about 6000 K, λmax = 480 nm)
max . 5 – 10 000 lux
(normal indoor is about 50-100 lux
bright sunlight is about 105 lux)
10 – 15 minutes / day
Damjanovich, Fidy, Szöllősi: Medical Biophysics
II. 2.3.3
II. 2. 3.4.
IX.2.
Absorption of UV-C and UV-B radiation leads to
photobiological damages in living organisms. Wich
macromolecule is responsible for these processes? Why?