MY RESEARCH INTERESTS (Wersja polska)

Dr hab. Alina Sionkowska (PhD, DSc)

Faculty of Chemistry, NCU Toruń

as@chem.uni.torun.pl

Photodegradation of collagen

Photochemical processes are important in vision and photosynthesis, which are the most representative biological processes. However, the gradual changes in the properties of materials which occur on exposure to sun light are well known.

The effects of ultraviolet radiation are both advantageous and deleterious to living organisms. Ultraviolet light has been used since 1877 to sterilise foods, to maintain sterile conditions during surgery, for preventing rickets, for killing pests and insects and for many other purposes. Ultraviolet light absorption is responsible for skin tanning and has been implicated in a causative way in many kinds of skin cancer.

Collagen is the most abundant protein in animals where it provides the principal structural and mechanical support [1,2]. There are 20 genetically distinct collagens in the collagen family, the major fibril forming collagens: type I ( skin, tendon and bone), type II (cartilage) and type III (skin and vasculature) are found as part of fibrillar structures that form an essential part of tissue architecture and integrity. Collagen is readily available, non-toxic and the fibril architecture that is inherent in natural tissues means that it provides an excellent basis for biomaterials such as arterial prostheses and artificial skin [3,4]. The degradation of biomaterials is an important factor in the suitability of using collagen in prostheses and many attempts have been made to alter the degradation properties of collagen.

Environmental factors such as UV irradiation that are able to modulate the structure and chemistry of collagen in vivo and in vitro therefore have a twofold importance.

Although there have been a number of previous attempts to investigate the effects of UV irradiation on collagen, the results have been far from conclusive with the emphasis often being on only one aspect of UV photodamage such as the biomechanical or biochemical effects. There is poor agreement as to whether the main effect of UV irradiation on collagen is.

Crosslink formation between collagen molecules, this is characterised by the decrease observed in collagen solubility after UV irradiation. Some preliminary evidence from my studies indicates the possibility of the formation of both inter and intramolecular crosslinking. Bond scission has been demonstrated by a number of research groups, this is characterised by a characteristic decrease in viscosity and the changes of absorbances point to the loss of water bonded to collagen, degradation of the peptide chains with scission of the amide bonds and abstraction of the side groups [5-11].

The photodamage of specific residues that allows the development of chromophores may be related to the above properties however the changes have been mainly characterised by spectrophotometry without detailed amino acid analysis. The formation of dityrosine has been reported by some research groups [12,13].

From the foregoing it can be seen that an understanding of photomodification is essential to the development of strategies able to alter the emphasis of bond scission, crosslinkage and photodamage.

References

1. 1. M. Van der Rest, R.Garrone, FASEB J., 5, 2814,(1991)

2. A.J. Bailey, R.G. Paul, J Soc. Leather Technol. Chem.; 82: 104.(1998)

3. Cote M, Doillon CJ, , Biomaterials; 13: 612. (1992)

4. Huc A, , J Am Leather Chem Assoc; 80: 195, (1985)

5. Fujimori E, FEBS lett., 235, 98 (1988)

6. Kamińska A. , Sionkowska A., Polym. Deg. Stab., 51, 15, 19 (1996).

7. Miles Ch. A. , Sionkowska A., Hulin S. L., Sims T. J., Avery N. C., Bailey A. J., J. Biol. Chem. 275, 33014 (2000).

8. Kamińska A. , Sionkowska A., Polimery, 39, 758 (1994).

9. Kamińska A. , Sionkowska A., J. Photochem. Photobiol. A: Chemistry, 96, 123 (1996).

10. Sionkowska A., Kamińska A. , Int. J. Biol. Macromol., 24, 337 (1999).

11. Sionkowska A., Kamińska A., Photochem. Photobiol. A: Chemistry, 120, 207 (1999).

12. Kato Y., Uchida K., Kawakishi S., Photochem. Photobiol. 59, 343 (1994).

13. Kato Y., Takashi N., Shundro K., Photochem. Photobiol. 61, 367 (1995).