The efficiency and specificity of RNA-protein cross-linking in the 30s subunit of Escherichia coli ribosomes, induced by low-intensity (lo1' photons cm-' s-l, 254 nm) and high-intensity [(1.6-6.8) x photons cm-' s-', 266 nm, pulse duration lo-* s] ultraviolet radiation, are studied. Under the former conditions proteins S4, S7 and S9/Sll, and under the latter conditions these proteins together with S3, S18 and S20, are cross-linked to 16s RNA. Biphotonic processes operate in the latter case. In the presence of 2-mercaptoethanol cross-linking occurs either directly, via a higher excited state or via activated intermediates with life-times less than 25 ns. Crosslinks thus formed are specific, i.e. they are formed between regions of macromolecules which are in contact in the native (non-disturbed) complex prior to excitation. The efficiency of cross-linking (per photon absorbed) is 20 -100 times higher upon two-step excitation as compared with single-step excitation and an analysable number of cross-links are produced in a single pulse. Only base U-1239 of 16s RNA is cross-linked to protein S7 by lowintensity radiation, whereas the adjacent base, G-1240 is also involved in laser-induced cross-linking. A transition from the former to the latter conditions allows one to reduce the duration of irradiation from several minutes to several nanoseconds.The formation of functional nucleoproteins depends on interactions between regions of polynucleotides and proteins with specific primary and higher structures. The stability of such complexes is determined by the cooperativity of multiple local non-covalent interactions, in particular between nucleic acid bases and amino acid residues, which can occur only between spatially adjacent groups with suitable mutual orientation and electronic structure.The identification of directly neighbouring macromolecules (i. e. those in contact) and the localisation, within their primary and higher structure, of neighbouring fragments and residues produces information about the functional topography of both component macromolecules and the complex as a whole. This can be achieved by generation of covalent bonds between components of macromolecules which are in direct contact within the original complex.The ultraviolet radiation of standard light sources is widely used for generation of polynucleotide-protein crosslinks in nucleoproteins [l, 21. In these cases reactions take place via lower excited states of nucleic bases [3]. Photochemical conversions via higher excited states populated by high-intensity (laser) irradiation are more efficient than via lower excited states [4 -81. Therefore transition from standard to laser light sources could result in the increase of cross-linking efficiency and in formation of additional crosslinks, which are unable to arise at all via lower excited states.Correspondence to E. 1. Budowsky, Institut Organicheskoj Khimii imeni N. D. Zelinskogo, Akademiya Nauk SSSR, Leninskij prospekt 47, Moskva, USSR 117913Some preliminary results of this study were prese...

The action of high-intensity ultraviolet pulse laser radiation on a 161 bp fragment of pBR 322 DNA (EcoRIlwspI fragment) was studied. At doses up to 5 x lOI photons/cm2 the N-gly~sidic bond splitting is negligible. The action of hot piperidine on irradiated DNA leads to chain splitting at the residues, modified via biphotonic processes. The modification and, hence, splitting efliciences depend on the type of base (G > T > A > C) and on its position in the sequence. Preferentially modified bases in the opposite strands of double-stranded DNA belong, mainly, to the same or adjacent base pairs. Residues in the Pribnow box are modified considerably less, than in Ihe sequences, immediately upstream and downstream. This approach seems to be useful in footp~nting of DNA secondary structure peculiarities and alterations, conjugated with the functional role and state of the respective fragment.Foo tprinting DNA secondary structure DNA splitting Laser ultraviolet irradiation PlasmidpBR 322

The standard module cell interconnection technique requires printed Ag front side busbars and rear side Ag/Al pads. From the standpoint of cell performance these contacts reduce cell efficiency strongly as a result of large cell shading and reduced surface passivations. Cells without busbars and pads would show a cell current and voltage increase and simplify the printing procedure.In this paper we introduce a new cell metallization technique which could be directly applied to standard industrial cells eliminating the need for rear pads and front busbars. Experiments were carried out to study the current and voltage gain of modified cells with the proviso that the cell fill factor will maintain at high level. Optimization experiments showed up to 0.8% higher cell efficiency for modified cells if compared to reference cells. Technique was furthermore successfully applied to 8 inch cells which showed fill factors of 77.9%.

Abstract. The present communication is concerned with the effects of near‐UV radiation (300–380 nm) on yeast Candida guilliermondii. It was found that certain doses of 313 nm irradiation caused inactivation of the yeast which was exhibited in a way different from the lethal action of far‐UV radiation. It was also found that the cells inactivated by 313 nm are capable of recovering vitality, if incubated for some time in a non‐nutrient medium. The yeast inactivated by far‐UV radiation also proved to be capable of recovering, though to a lesser degree. Both 334 nm radiation and non‐lethal doses at 313 nm induced the photoprotective effect against far‐UV damage. The effect was exhibited if there was a certain time interval (2–4 h) between the exposures to photoprotective light and subsequent far‐UV radiation. Within this time interval the extent of photoprotection was dependent on temperature.

Abstract— The set of final products of thymine conversion induced by high‐intensity UV irradiation (λ= 266nm, intensity 1024‐5 × 1029 photons·s−1·m−2, pulse duration 10ns) of the dilute aqueous solution to the first approximation is similar to that formed with ionizing irradiation (γ‐irradiation of aqueous solution or autoradiolysis of a solid 2‐[14C]‐thymine). The data obtained suggest that high‐intensity UV‐induced photochemical conversion of thymine involves photoionization and/or photodissociation. These processes pass through the higher excited state(s) populated as a result of the second photon absorption by excited (most probably in the T1 triplet state) thymine molecules.