Mechanism of High Power Picosecond Laser Uv Inactivation of Viruses and Bacterial Plasmids

Abstract

Abstract— The mechanism of inactivating action of high‐power picosecond laser UV radiation (λ= 266 nm) on the λ and φX174 bacteriophages and the pBR 322 plasmid has been studied. It has been shown that at UV radiation intensities from 1011 to 1013 W/m2, inactivation of viruses and bacterial plasmids occurs mainly on account of single‐strand breaks in the DNA chain unlike the case of less powerful UV radiation where the inactivation is associated with the formation of pyrimidine dimers.

Depopulation of Highly Excited Singlet States of DNA Model Compounds: Quantum Yields of 193 and 245 nm Photoproducts of Pyrimidine Monomers and Dinucleoside Monophosphates

“…Scheme 1 143 144 Gagik G. Gurzadyan and Helmut Gorner nucleobases after excitation of S, via internal conversion and geminate recombination, only little is known. On the basis of studies with two-quanta excitation of nucleic acids by use of powerful picosecond lasers it has been predicted that high-lying electronic states (9 eV) do not contribute to dimer formation (22,(52)(53)(54)(55)(56).The aim of this paper is an elucidation of the depopulation process via the S , 3 S, transition and the determination of the quantum yields of these steps. For this purpose we have chosen four uracil-containing monounits and five pyrimidine dinucleoside monophosphates (Scheme 2).…”

“…Scheme 1 143 144 Gagik G. Gurzadyan and Helmut Gorner nucleobases after excitation of S, via internal conversion and geminate recombination, only little is known. On the basis of studies with two-quanta excitation of nucleic acids by use of powerful picosecond lasers it has been predicted that high-lying electronic states (9 eV) do not contribute to dimer formation (22,(52)(53)(54)(55)(56).…”

PHOTOLESIONS IN DNA UPON 193 nm EXCITATION

“…For A,,, c 250 nm it has to he taken into account that the reverse photosplitting reaction occurs effectively (with @ = 0.5-1). Kochcvar and BuckleyZR have used sufficiently low fluences 01' [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] . I m and their rcsult for A,, = 193 nm is ad,,,, = 1.05 x lo-'.…”

BASE RELEASE FROM DNA AND POLYNUCLEOTIDES UPON 193 nm LASER EXCITATION

“…The initial step in most of these laser-induced photoreactions is photoionization, yielding hydrated electrons ( e-& and radical cations of bases. Reactions of the radical cations and their resulting neutral radicals produce single-strand breaks (ssb) in nucleic acids (Croke et al, 1988;Waia et al, 1990;Bothe et al, 1990;Masnyk and Minton, 1991); for recent reviews see Nikogosyan, 1990;Cadet and Vigny, 1990; In the case of ionizing radiation the loss of transforming ability in biologically active DNA has been attributed to ssb formation (Gurzadyan et al, 1981;Huttermann et al, 1978;von Sonntag, 1987;Nikogosyan, 1990;Ward, 1991).…”