Spectral composition of shade light in coastal-zone oak forests in SE Bulgaria,and relationships with leaf area index: a first overview

Major knowledge gaps exist with respect to light-quality regimes in the coastal-zone Strandzha Quercus frainetto (Q.f.) forest region adjoining the southern Bulgarian Black Sea. This paper presents preliminary results that help narrow these gaps. In conjunction with leaf area index (LAI) field campaigns we undertook measurements with an array of 7 broad-band (ca 40 nm) sensors covering the range 0.40–0.94 μm, plus 1 sensor for UVB (0.297 μm peak) and 1 for photosynthetically active radiation (PAR). Measurements focused on inside-forest shade conditions at sites 0 to ca 15 km from the Black Sea and at altitudes up to ca 120 m above sea level. Some of the sites were also studied using a high-resolution spectroradiometer. A sequential measuring strategy was necessary. This involves potentially large uncertainties, here addressed through estimations of the variability around the sinusoidal course of daylight. Light-quality regimes were found to be in general support of earlier studies of deciduous forests. Our data from the broad-band sensors and from the spectroradiometer are mutually supportive. They indicate a stronger red-shift below Q.f. canopies than below canopies in enclaves dominated by Fagus orientalis and Pinus sylvestris. Transmission in the range 0.50–0.55 μm increases beneath the three types of canopies, most pronounced in the Q.f. case. Analysis of relationships between the inside-forest to open-field irradiance ratio and LAI supports the use of Beer’s Law. We found a fairly strong relationship between the red (0.66 μm) to far-red (0.73 μm) irradiance ratios (R/FR) and LAI for the Q.f. forest. In quantitative terms, the result is new for this Q.f. region, and suggests further research to explore whether a two-sensor approach (0.66 and 0.73 μm) might offer possibilities for further low-cost mapping of the spatio-temporal patterns of R/FR and LAI in Strandzha. Such mapping would assist in further studies of the region’s forest biogeochemistry and vitality.     

Synthesis and Analysis of Nucleosides Bearing Pyrrolepolyamide Binding to DNA

Abstract

An efficient synthesis of adenosine bearing pyrrolepolyamide 1 was achieved by coupling of 3 with 2. The CD spectra obtained at several [ligand ]/[duplex] ratios allowed verification of the formation complex of the DNA duplex [d(CGCAAATTGGC)/d(GCCAATTTGCG)] with 1.     

Study of the binding of jatrophone to Escherichia coli s-ribonucleic acid

The interaction of jatrophone with sRNA from Escherichia coli has been investigated through UV, CD, and 1H NMR measurements. The results obtained show that the interaction with jatrophone increases the stability of the polynucleotide. It appears that the optical properties of jatrophone depend upon the jatrophone/nucleotide ratio. The observed behaviour can only be explained by the existence of different types of interaction between jatrophone and sRNA. Even for a jatrophone/nucleotide ratio as low as 0.17 the 1H NMR spectra show a multiplicity of resonances that can only be explained by the simultaneous existence of two different binding modes involving the jatrophone molecules.     

NAD(P)H oscillation in relation to the rhythmic contraction in thePhysarum plasmodium

Summary ThePhysarum plasmodium shows rhythmic contractile activities with a period of a few min. Phases of the oscillation in the plasmodium migrating unindirectionally agreed sideways throughout at the frontal part. So, time course of an intracellular chemical component was determined by analyzing small pieces cut off successively from the frontal part of the large plasmodium. Intracellular NAD(P)H concentration oscillated with the same period as the rhythmic contraction but with a different phase advancing about 1/3 of the period. UV irradiation suppressed the rhythmic contraction without affecting the rhythmic variation of NAD(P)H. Thus, the NAD(P)H oscillator works independently of the rhythmic contractile system, but seems entraining with each other.Abbreviations UV ultraviolet - NADH nicotinamide adenine dinucleotide, reduced form - NADPH nicotinamide adenine dinucleotide phosphate, reduced form - ATP adenosine 5-triphosphate - cAMP cyclic adenosine 3, 5-monophosphate - FMNH₂ flavin mononucleotide, reduced form - TCA tricarboxylic acid - BSA bovine serum albumin - DTT dithiothreitol     

Detection of phospholipid peroxides in biological samples

Peroxidation of membrane lipids has been hypothesized to play a key role in various types of tissue degeneration and pathology. Lipid peroxides are formed when oxygen reacts with an unsaturated fatty acid chain. Virtually all of the unsaturated fatty acids in biological systems are bound by ester linkages in phospholipids or triglycerides. Phospholipid and triglyceride peroxides are primary products of lipid peroxidation and have rarely been measured. Most of the commonly used methods for detection of lipid peroxidation are based on detection of malondialdehyde or other chemical species that are derived from oxidized fatty acids. This review presents an overview of recently developed methods aimed at identifying and measuring oxidized phospholipids and triglycerides which are direct evidence of the occurrence of lipid peroxidation in vivo.     

UV irradiation inhibits initiation of DNA replication from oriC in Escherichia coli

Summary Irradiation of Escherichia coli with UV light causes a transient inhibition of DNA replication. This effect is generally thought to be accounted for by blockage of the elongation of DNA replication by UV-induced lesions in the DNA (a cis effect). However, by introducing an unirradiated E. coli origin (oriC)-dependent replicon into UV-irradiated cells, we have been able to show that the environment of a UV-irradiated cell inhibits initiation of replication from oriC on a dimer-free replicon. We therefore conclude that UV-irradiation of E. coli leads to a trans-acting inhibition of initiation of replication. The inhibition is transient and does not appear to be an SOS function.     

Mutations by near-ultraviolet radiation in Escherichia coli strains lacking superoxide dismutase

Om wild-type Escherichia coli, near-ultraviolet radiation (NUV) was only weakly mutagenic. However, in an allelic mutant strain (sodA sodB) that lacks both Mn- and Fe-superoxide dismutase (SOD) and assumed to have excess superoxide anion (O₂⁻), NUV induced a 9-fold increase in mutation above the level that normally occurs in this double mutant. When a sodA sodB double mutant contained a plasmid carrying katG⁺ HP-I catalase), mutation by NUV was reduced to wild-type (sodA⁺ sodB⁺) levels. Also, in the sodA sodB xthA triple mutant, which lacks exonuclease III (exoIII) in addition to SOD, the mutations frequency by NUV was reduced to wild-type levels. This synergistic action of NUV and O₂⁻ suggested that pre-mutational lesions occur, with exoIII converting these lesions to stable mutants. Exposure to H₂O₂ induced a 2.8 fold increase in mutations in sodA sodB double mutants, but was reduced to control levels when a plasmid carrying katG⁺ was introduced. These results suggest that NUV, in addition to its other effects on cells, increases mutations indirectly by increasing the flux of OH^. radicals, possibly by generating excess H₂O₂.