Background/Aims: The exact mechanisms of action of balneophototherapy are incompletely understood. We aimed to investigate the effect of salt water soaks on ultraviolet (UV) transmission and the expression of molecular parameters of psoriasis. Methods: We studied UV transmission and the expression of antimicrobial peptides and skin-derived antileukoproteinase (SKALP/elafin) in psoriatic epidermis equivalents which were pretreated with tap water and differently concentrated salt water solutions. Moreover, we performed in vivo phototoxicity tests in healthy subjects. Results: Highly concentrated salt water soaks significantly increase UV transmission through psoriatic epidermis equivalents, in particular within the wavelength range of 305– 360 nm. In vivo tests revealed increased photosensitivity following highly concentrated salt water baths. A significant decrease in human β-defensin-2 (hBD-2) and SKALP/elafin is observed after highly concentrated NaCl soaks. Conclusion: An increase in UV transmission following highly concentrated salt water soaks likely causes enhanced UV gain within the viable epidermis. Moreover, our data indicate that salt water soaks seem to influence the protein profiles of hBD-2 and SKALP/elafin.

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We have characterised the electron-transfer properties of the D 1/D2/cytochrome b-559 complex using EPR spectrometry. The complex can transfer electrons to silicomolybdate and ferricyanide at cryogenic temperatures. In the presence of silicomolybdate or ferricyanide, two chlorophyll cation radicals were observed from P680 ÷ (0.8 mT) and monomeric Chl (1.0 mT). Reduction of silicomolybdate was detected as a 2.7 mT signal at g = 1.942. A radical attributed to a tyrosine cation radical (D ÷/Z ÷) was also observed in a small percentage of centres.

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We have investigated the quinone-binding region of PS II using exchange reactions to replace key components. Bicarbonate was replaced by formate and Qs by exogenous quinones or herbicide. The effects of these changes were monitored using the ESR signals from the QA iron-semiquinone and FZ+ non-haem iron components. We observed that Qs binding caused characteristic changes in the Qi ESR signal and confirmed that the characteristics of Qi depend on bicarbonate binding. The non-haem iron was oxidised only under conditions where bicarbonate was bound. The characteristics of bicarbonate binding were observed in Phormidium laminosum PS II, showing that the bicarbonate effect occurs in cyanobacteria. The results support a hypothesis which gives a central role to bicarbonate in providing the conditions for electron transfer in both cyanobacteria and higher plant PS II. It is suggested that bicarbonate binds at or close to the nonhaem iron and influences the characteristics of QA, Qa and the non-haem iron.