A pistil-specific thaumatin/PR5-like protein gene of Japanese pear (Pyrus serotina): sequence and promoter activity of the 5′ region in transgenic tobacco

The genomic clone encoding the pistil-specific thaumatin/PR5-like protein (PsTL1) was isolated from Japanese pear (Pyrus serotina). Sequence analysis showed that the genomic clone contained the 5-flanking sequence of 2.4 kb, the 3-flanking sequence of 648 bp and the coding region interrupted by a intron of 351 bp. A sequence motif conserved in some pistil self-incompatibility gene promoters of solanaceous and brassicaceous species was located in the 5-flanking region of the PsTL1 gene. The 2.4 kb 5-flanking region was fused to the GUS coding sequence and transferred to tobacco. Transgenic tobacco showed GUS activity in pistil and, at low level, in anther, but not in other floral organs and leaf. Histochemical analysis localized GUS activity to stigma, transmitting tissue, anther and pollen of transgenic tobacco.     

Abiogenic synthesis of oligonucleotides on kaolinite under the action of ultraviolet radiation

Summary The present work deals with the processes involved in the abiogenic polycondensation of nucleotides adsorbed on the clay mineral kaolinite under the action of ultraviolet (UV) radiation. The dependence of the yield of synthesis products on irradiation dose was studied. The maximum yield corresponds to a 6-h exposure. The newly synthesized substances were analyzed by ion-exchange chromatography. Some fractions were studied for the type of bonds they contained by venom phosphodiesterase and RNase T₂ enzymatic hydrolysis. It was determined that some of the products synthesized by exposure of AMP adsorbed on the surface of clay particles to UV radiation may be looked upon as oligonucleotides in which some fragments have 2–5-bonded and others 3–5-bonded nucleotides     

Localization of adenosine 5′-phosphosulfate sulfotransferase in spinach leaves

Roots of spinach (Spinacia oleracea L.) seedlings contained only a very low activity of adenosine 5-phosphosulfate sulfotransferase compared to the cotyledons. Adenosine 5-phosphosulfate sulfotransferase activity increased about tenfold in cotyledons during greening. Preparation of organelle fractions from spinach leaves by a combination of differential and isopycnic density gradient centrifugation showed that adenosine 5-phosphosulfate sulfotransferase banded with NADP-glyceraldehyde-3-phosphate dehydrogenase, a marker enzyme for intact chloroplasts. In the fractions of peroxisomes, mitochondria and broken chloroplasts virtually no adenosine 5-phosphosulfate sulfotransferase activity was measured. Comparison with the chloroplast enzyme NADP-glyceraldehyde-3-phosphate dehydrogenase indicates that in spinach, adenosine 5-phosphosulfate sulfotransferase is localized almost exclusively in the chloroplasts.Abbreviations APS Adenosine 5-phosphosulfate - APSSTase Adenosine 5-phosphosulfate sulfotransferase - BSA Bovine serum albumin - BRIJ58 Polyethylene glycolmonostearylether - DTE Dithioerythritol - DTT Dithiothreitol - EDTA Ethylenediaminetetraacetic acid - ME 2-Mercaptoethanol - NADP-GPD NADP-linked glyceraldehyde-3-phosphate dehydrogenase - PAPS Adenosine 3-phosphate 5-phosphate 5-phosphosulfate - POPOP 1,4 Di [2-(5-phenyloxazolyl)]-benzene - PPO 2,5-Diphenyloxazol The results presented in this paper are taken from the Ph. D. thesis of H.F.     

Enzymic synthesis,chemical characterisation and Sda activity of GalNAcß1-4[NeuAcα2-3]Galß1-4GlcNAc and GalNAcß1-4[NeuAcα2-3]Galß1-4Glc

The tetrasaccharides GalNAcß1-4[NeuAc2-3]Galß1-4Glc and GalNAcß1-4[NeuAc2-3]Galß1-4GlcNAc were synthesised by enzymic transfer of GalNAc from UDP-GalNAc to 3-sialyllactose (NeuAc2-3Galß1-4Glc) and 3-sialyl-N-acetyllactosamine (NeuAc2-3Galß1-4GlcNAc). The structures of the products were established by methylation and¹H-500 MHz NMR spectroscopy. In Sd^a serological tests the product formed with 3-sialyl-N-acetyllactosamine was highly active whereas that formed with 3-sialyllactose had only weak activity.     

Full 1H NMR assignment of a 24-nucleotide RNA hairpin: Application of the 1H 3D-NOE/2QC experiment

The subject RNA models the binding site for the coat protein of the R17 virus, as well as the ribosome recognition sequence for the R17 replicase gene. With an RNA of this size, overlaps among the sugar protons complicate assignments of the ¹H NMR spectrum. The cross peaks that overlap significantly in 2D-NOE spectra can frequently be resolved by introducing a third, in our approach the double-quantum, frequency axis. In particular the planes in a 3D-NOE/2QC spectrum perpendicular to the 2Q axis are extremely useful, showing a highly informative repeating NOE-2Q pattern. In this experiment substantial J-coupling confers special advantages. This always occurs for geminal pairs (H5/H5 for RNA plus H2/H2 for DNA), as well as for H5/H6, for H3/H4 in sugars with substantial populations of the N-pucker, for H1/H2 for S-puckered sugars, and usually for H2/H3. For the 24-mer RNA hairpin the additional information from the 3D-NOE/2QC spectrum allowed assignment of all of the non-exchangeable protons, eliminating the need for stable-isotope labeling.     

Interaction between photosynthetic and respiratory electron-transfer chains in the membranes of Anabaena variabilis

The rate of CO₂- and p-benzoquione-dependent photosynthetic O₂ evolution by Anabaena variabilis cells remained unaltered and the rate of O₂ uptake observed after switching off the light (endogenous respiration) was enhanced by a factor of 6–8 when the O₂ concentration was increased from 200 to 400 M. Photosystem-I-linked O₂ uptake and respiration of the cells incubated with ascorbate and N,N,NN-tetramethyl-p-phenylenediamine was not appreciable influenced by the O₂ concentration. 2-Iodo-6-isopropyl-3-methyl-2,4,4-trinitrodiphenyl ether, blocking electron transfer at the plastoquinone level, suppressed O₂ evolution and had no influence on endogenous respiration. 2-n-Heptyl-4-hydroxyquinoline-N-oxide, an inhibitor of electron transfer between photosystems II and I, as well as the cytochrome-oxidase inhibitors N ₃ ^- , CN^- and NH₂OH, caused a 35–50% retardation of endogenous respiration and blocked photosynthetic O₂ evolution. The molar ratio of cytochromes b₆, f, c-553, aa₃ and photosystem-I reaction centers in the isolated membranes equalled approx. 2:1:2:0.7:2. It is inferred that endogenous respiration of A. variabilis cells is inhibited by the light-induced electron flow through both photosystems at the level of the plastoquinone-plastocyanin-oxidoreductase complex.Abbreviations DCMU 3-(3,4-dichlorophenyl)-1,1-dimethylurea - DNP-INT 2-iodo-6-isopropyl-3-methyl-2,4,4-trinitrodiphenyl ether - Hepes 4-(2-hydroxyethyl)-1-piperazine ethansulfonic acid - TMPD N,N,NN-tetramethyl-p-phenylenediamine     

Molecular cloning and expression analysis of the mevalonate kinase gene from Arabidopsis thaliana

Mevalonate kinase (MVK), the enzyme that catalyzes the phosphorylation of mevalonate to produce mevalonate 5-phosphate, is considered as a potential regulatory enzyme of the isoprenoid biosynthetic pathway. The Arabidopsis thaliana MVK gene corresponding to the MVK cDNA previously isolated has been cloned and characterized. RNAse protection analysis indicated that the expression of the MVK gene generates three mRNA populations with 5 ends mapping 203, 254 and 355 nt upstream of the MVK ATG start codon. Northern blot analysis showed that the MVK mRNA accumulates preferentially in roots and inflorescences. Histochemical analysis, with transgenic A. thaliana plants containing a translational fusion of a 1.8 kb fragment of the 5 region of the MVK gene to the -glucuronidase (GUS) reporter gene, indicated that the MVK 5-flanking region directs widespread expression of the GUS gene throughout development, although the highest levels of GUS activity are detected in roots (meristematic region) and flowers (sepals, petals, anthers, style and stigmatic papillae). The expression pattern of the MVK gene suggests that the role of the encoded MVK is the production of a general pool of mevalonate-5-phosphate for the synthesis of different classes of isoprenoids involved in both basic and specialized plant cell functions. Functional promoter deletion analysis in transfected A. thaliana protoplasts indicated that regulatory elements between positions –295 and –194 of the MVK 5-flanking region are crucial for high-level MVK gene expression.     

Utilization of 5-fluorouracil byMyobacterium avium

Myobacterium avium LM1 was exposed to concentrations of 5-fluorouracil (5FU) that ranged from 0 to 100 g/ml. Growth inhibition was inversely proportional to the concentration of the drug. DNA was extracted from cells grown in medium that contained [¹⁴C]5FU, but no carrier. The [¹⁴C]DNA was enzymatically hydrolyzed to deoxyribonucleotides, which were separated and fractionated by high-performance liquid chromatography (HPLC). The isotope was located in 2-deoxycytidine 5-monophosphate (dCMP) and 2-deoxythymidine 5-monophosphate (dTMP), with dCMP containing the majority. There was no radioactivity at the elution times for 5-fluoro-2-deoxyuridine 5-monophosphate or 2-deoxyuridine 5-monophosphate. These results suggested that 5FU was dehalogenated and the uracil moiety ultimately converted into cytosine and thymine deoxyribonucleotides. Cells were grown in [³H]uracil, and [³H]DNA was extracted and analyzed by HPLC. The isotope was found only in the pyrimidine deoxyribonucleotides, with dCMP containing 4.1 times that in dTMP. Thus, it was demonstrated that uracil and dehalogenated 5FU were not directly incorporated into DNA, but rather converted to cytosine and thymine and then incorporated into DNA by a salvage pathway.     

Characterisation of a pea hsp70 gene which is both developmentally and stress-regulated

A pea pod cDNA library was screened for sequences specific to lignifying tissue. A cDNA clone (pLP19) encoding the C-terminal region of a hsp70 heat shock protein hybridised only to pod mRNA from pea lines where pod lignification occurred. Expression of pLP19 was induced by heat shock in leaves, stems and roots of pea and chickpea plants. Four different poly(A) addition sites were observed in cDNAs derived from the same gene as pLP19. This gene was fully sequenced; unlike most hsp70 genes, it contains no introns. The 5-flanking sequence contains heat shock elements and other potential regulatory sequences.     

Characterization of a Gy4 glycinin gene from soybean Glycine max cv. Forrest

The glycinin gene family encoding the glycinin subunits in soybean plants is composed of at least five gene members. A genomic clone S312 containing the Gy4 gene from a genomic library of cv. Forrest was isolated and partially characterized. The organization of this gene was found to be similar to that of a null allele from cv. Raiden, but different from the Gy4 gene from cv. Dare. The complete nucleotide sequence of this gene has been determined. It is 2599 bp long consisting of four exons and three introns. Comparing the DNA sequences between this gene and the gene from Dare and a null allele from Raiden, the difference found in the coding region was 5-GCAGTGCAAG-3 (nt 824 to 833) in the former case versus 5-TGGAGTTGCAATT-3 (nt 1314 to 1326) in the latter case in the exon 2 domain, resulting in three amino acid differences and one amino acid absence. Some other differences were also found in the non-coding region. The coding sequence and 5-flanking region of the Gy4 gene, when compared with that of other legumin genes as well as group 1 glycinin subunit genes, revealed some interesting features: (1) a transposable element-like sequence was found in the hypervariable region (HVR) of the exon 3 domain, which was lacking in the legumin and the glycinin group 1 genes; (2) in the 5-flanking region from nt –145 to –1, two high-homology sequences were found: one from nt –141 to nt –132, the other from nt –118 to nt –92 which includes the legumin box and the RY repeat element.     

Cyanine dye structural and voltage-induced variations in photo-voltages of bilayer membranes

Summary Flash illumination alters the voltage across bilayer lipid membranes in the presence of certain cyanine dyes. The waveforms of the photo-voltage vary systematically with dye structure and imposed transmembrane voltage. Experimental results are reported for 27 positively charged cyanine dyes, primarily oxazole derivatives, using lecithin/oxidized cholesterol bilayer membranes and 10-mm sodium chloride solutions. Several dyes do not induce any photo-voltages. Examples are 3,3 diethyl 9 ethyl 2,2 oxacarbocyanine iodide, 3,3 diethyl 2 oxa 2 thiacyanine iodide, and 3,3 dimethyl 2,2 indocarbocyanine iodide. Several dyes, when added to one side of the membranes, induce monophasic waveforms. Examples are 3,3 dimethyl 2,2 oxacarbocyanine chloride, and 3,4,3,4 tetramethyl 2,2 oxazalinocarbocyanine iodide. Other dyes induce a photo-voltage only if transmembrane voltages are imposed. These waveforms are biphasic with some dyes (3,3 diethyl 2,2 oxacarbocyanine iodide, for example) and monophasic with other dyes (3,3 dibutyl 2,2 oxacarbocyanine iodide, for example).The photo-voltage waveforms are explained by models that consider the movement of charged dye molecules within the membrane, following optical excitation. The dye movements are probably induced through charge rearrangements in the dye associated with long-lived triplet states, isomerization, or through excimer formation. These results provide information on the location and orientation of the dye molecules within bilayer membranes. The variations which occur in the waveforms with applied voltage indicate that these membranes are fluid in the direction perpendicular to the membrane plane.     

Identification of the cytokinins in red pine seedlings

Zeatin-9-riboside was identified in shoots and roots of Pinus resinosa by GC-MS analysis of its permethyl derivative. Based on their chromatographic properties on Sephadex LH-20 and C₁₈ HPLC, and their susceptibility to enzymatic degradation, several other cytokinins have been tentatively identified. The basic fraction of both the roots and shoots contained zeatin, whereas the shoots contained dihydrozeatin-O-glucoside and the roots contained zeatin-O-glucoside. Zeatin-9-riboside monophosphate, isopentenyladenosine monophosphate ([9R-5P]iP) and glucosyl phosphate derivatives were detected in the acidic fractions from both roots and shoots. There were equivalent amounts of [9R-5P]iP in both roots and shoots. The presence of equivalent amounts of [9R-5P]iP in both the roots and shots suggests that cytokinin biosynthesis may be occurring in both locations.Abbreviations AMP adenosine-5-monophosphate - BAP benzylaminopurine - BSA bovine serum albumin - BuOH butan-1-ol - CK cytokinin - (diH)Z dihydrozeatin - (diH OG)Z dihydrozeatin-O-glucoside - (diH OG)[9R]Z dihydrozeatin-9-riboside-O-glucoside - DW dry weight - EtOH ethanol - FW fresh weight - GC-MS gas chromatography-mass spectrometry - HPLC high-performance liquid chromatography - [9R]iP isopentenyladenosine - [9R-5P]iP isopentenyladenosine monophosphate - MeOH methanol - PVP polyvinylpyrrolidone - RFE rotary film evaporation - TEAB triethyl ammonium bicarbonate - Z zeatin - [9R]Z zeatin-9-riboside - (OG)Z zeatin-O-glucoside - [7G]Z zeatin-7-glucoside - [9R-5P]Z zeatin-9-riboside monophosphate     

Identification of a multigene family for small heat shock proteins in soybean and physical characterization of one individual gene coding region

When soybean seedlings are tranferred from 28 to 40 ° C, a heat shock (hs) response is elicited. This is characterized by the synthesis of a new set of proteins (hs-proteins) and by cessation of normal protein synthesis (8). At the level of poly(A)mRNA, a new class of highly abundant RNAs appears which encodes a group of hs-proteins in the low molecular weight range of 15–18 kD (11). The classification of these proteins/genes into several sub-classes is based on a complex sequence relationship for class I protein/genes.This was confirmed by both the complexity and the similarity of southern blot hybridization patterns of genomic DNA digests with class I cDNA-probes. Genomic DNA clones (obtained from -libraries by screening with cDNA-probes) for the class I gene 1968 showed cross hybridization with all other class I cDNA-probes. Higher specificity of gene/protein correlation was obtained by variation of hybridization criteria. The specificity of cDNA clone 1968 for the genomic DNA clone hs68-7 was demonstrated by thermal stability of hybridization at 55 ° C and 65 ° C in 50% formamide compared to other cross-reacting probes. The correlation of clone 1968 with a specific hs-protein was obtained by temperature dependent release of hybrid selected hs-mRNAs at 50, 60, 70 and 85 ° C followed byin vitro translation and two-dimensional gel analysis. The coding regions of hs-genes on genomic DNA clones were mapped by R-loop formation. The position of R-loops was mapped relative to certain restriction sites on subclones of hs68-7 DNA. The polarity of hs-genes was determined by attaching X174RF-DNA labels to the 3 poly(A)-tails of the mRNAs of R-loops.     

Abscisic acid metabolism —vacuolar/extravacuolar distribution of metabolites

The biotransformation of abscisic acid (ABA) was studied in cell suspension cultures of Lycopersicon esculentum. The ABA was converted by the cells to phaseic acid, nigellic acid, dihydrophaseic acid, abscisic acid--D-glucopyranosyl ester (ABA-Glc) and other ABA and phaseic acid conjugates. Investigation of their cellular distribution showed that the conjugated forms were located only in the vacuoles whereas ABA and its acidic metabolites were found mainly in the extravacuolar fractions. Our results, together with a number of studies on the increase of ABA-Glc as a response to stress, allow us to propose that ABA-Glc is irreversibly compartmented in the vacuoles of plant cells.Abbreviations ABA abscisic acid - ABA-Glc -D-glucopyranosyl ester of ABA - DPA 4-dihydrophaseic acid; nigellic acid=3-methyl-5-(1-hydroxy-2-hydroxymethyl-6-dimethyl-4-oxo-cyclohex-2-enyl)-penta-2Z, 4E-dienoic acid - PA phaseic acid     

Nucleotide sequence and expression of the two genes encoding D2 protein and the single gene encoding the CP43 protein of Photosystem II in the cyanobacterium synechococcus sp. PCC 7002

The unicellular photoheterotrophic cyanobacterium Synechococcus sp. PCC 7002 was shown to encode two genes for the Photosystem II reaction center core protein D2 and one gene for the reaction center chlorophyhll-binding protein CP43. These three genes were cloned and their DNA sequences determined along with their flanking DNA sequences. Northern hybridization experiments show that both genes which encode D2, psbD1 and psbD2, are expressed at roughly equivalent levels. For each of the two psbD genes, there are 18 nucleotide differences among the 1059 nucleotides which are translated. The DNA sequences surrounding the coding sequences are nearly 70% divergent. Despite the DNA sequence differences in the genes, the proteins encoded by the two genes are predicted to be identical. The proteins encoded by psbD1 and psbD2 are 92% homologous to other sequenced cyanobacterial psbD genes and 86% homologous to sequenced chloroplast-encoded psbD genes.The single gene for CP43, psbC, overlaps the 3 end of psbD1 and is co-transcribed with it. Results from previous sequencing of psbC genes encoded by chloroplasts suggest that the 5 end of the psbC gene overlaps the 3 end of the coding sequence of psbD by 50 nucleotides. In Synechococcus sp. PCC 7002, the methionine codon previously proposed to be the start codon for psbC is replaced by an ACG (threonine) codon. We propose an alternative start for the psbC gene at a GTG codon 36 nucleotides downstream from the threonine codon. This GTG codon is preceded by a consensus E. coli-like ribosome binding sequence. Both the GTG start codon and its preceding ribosome binding sequence are conserved in all psbC genes sequenced from cyanobacteria and chloroplasts. This suggests that all psbC genes start at this alternative GTG codon. Based on this alternative start codon, the gene product is 85% identical to other cyanobacterial psbC gene products and 77% identical to eucaryotic chloroplast-encoded psbC gene products.     

Reductive activation of the methyl-tetrahydromethanopterin: coenzyme M methyltransferase from Methanobacterium thermoautotrophicum strain ΔH

The enzymatic conversion of formaldehyde to CH₃S-CoM in crude extracts of Methanobacterium thermoautotrophicum was used as a means to investigate the methyl-tetrahydromethanopterin: HS-CoM methyltransferase reaction. All components necessary for formaldehyde conversion were shown to be present in a soluble protein fraction. This soluble cell fraction still contained a major amount of corrinoids. Apart from tetrahydromethanopterin no other soluble cofactors were required for formaldehyde conversion. The dependence of the system on catalytic amounts of ATP was shown to be specific. Several nucleoside triphosphates or ADP were unable to substitute for ATP. Remarkably, various strong reducing systems, especially titanium(III)citrate could replace ATP to a large extent. The ATP-dependent formaldehyde conversion to CH₃S-CoM was inhibited in the presence of nitrous oxide, detergents or 2,3-dialdehyde-ATP. The results support a role for a corrinoid protein in the methyl-tetrahydromethanopterin: HS-CoM methyltransferase reaction at which ATP is involved in the activation of this protein, probably in the conversion of inactive B_12a or B_12r to active B_12s.Abbreviations HS-CoM Coenzyme M, 2-mercaptoethanesulfonate - CH₃S-CoM methylcoenzyme M, 2-(methylthio)ethanesulfonate - H₄MPT 5,6,7,8-tetrahydromethanopterin - BES 2-bromoethanesulfonate - BCE boiled cell-free extract - DTT dithiothreitol - TCS 3,3,4,5-tetrachlorosalicylanilide - DNTB 2,2-dinitro-5,5-dithiobenzoic acid - TES N-tris(hydroxymethyl)methyl-2-aminoethanesulfonate - HEPES N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid - PIPES piperazine-N,N-bis[2-ethanesulfonic acid] - AMP-PNP 5-adenylyl imidophosphate     

A comprehensive characterization of single-copy T-DNA insertions in the Arabidopsis thaliana genome

T-DNA flanking sequences were isolated from 112 Arabidopsis thaliana single-copy T-DNA lines and sequence mapped to the chromosomes. Even though two T-DNA insertions mapped to a heterochromatic domain located in the pericentromeric region of chromosome I, expression of reporter genes was detected in these transgenic lines. T-DNA insertion did not seem to be biased toward any of Arabidopsis' five chromosomes. The observed distribution of T-DNA copies in intergenic sequence versus gene sequence (i.e. 5-upstream regions, coding sequences and 3-downstream regions) appeared randomly. An evaluation of T-DNA insertion frequencies within gene sequence revealed that integration into 5-upstream regions occurred more frequently than expected, whereas insertions in coding sequences (exons and introns) were found less frequently than expected based on random distribution predictions. In the majority of cases, single-copy T-DNA insertions were associated with small or large rearrangements such as deletions and/or duplications of target site sequences, deletions and/or duplications of T-DNA sequences, and gross chromosomal rearrangements such as translocations. The accuracy of integration was similarly high for both left- and right-border sequences. These results may be called upon when making detailed molecular analyses of transgenic plants or T-DNA induced mutants.     

Central nervous system myelin proteins of the coelacanth Latimeria chalumnae: phylogenetic implications

Synopsis Myelin was isolated from the brain of a coelacanth. Its protein components were separated by polyacrylamide gel electrophoresis in the presence of sodium dodecylsulfate (SDS-PAGE). A protein component of 25000 Dalton was predominant; it was not glycosylated but reacted moderately with anti-mammalian CNS myelin proteolipid protein (PLP) antibodies and weakly with anti-lungfish CNS myelin glycosylated proteolipid protein (gPLP) antibodies. A component equivalent to mammalian DM-20 was not detectable. Presumably due to autolysis myelin basic protein (MBP) was not discernible by protein staining but showed up as a single band of 17000 Dalton with anti-mammalian MBP antibodies. Wolfgram protein (WP) was not present upon immunoblotting and the values for the myelin-specific 2, 3-cyclic nucleotide 3-phosphodiesterase (CNPase) were extremely low. These results question a chondrichthyan association of the coelacanth but are strongly in favor of an Actinistia-Tetrapoda sister group relationship, with Dipnoi being most closely related to that combined group.     

Two-dimensional 1H NMR study of two cyclobutane type photodimers of thymidylyl-(3′→5′)-thymidine

2D NMR spectroscopy and J coupling constant analysis are applied to resolve the structure of two photoproducts of thymidylyl-(35)-thymidine. These products are cyclobutane type thymine dimers possessing the cis-syn (the predominant one) and trans-syn geometry. The cis-syn is formed in an ANTI-ANTI conformation about the N-glycosyl linkages and resembles the normal base-stacked configuration. The glycosidic conformation in solution of the 5 terminal fragment differs from the crystal in which the less common SYN conformation is observed. In this isomer only the sugar pucker of the 3 terminal fragment is changed substantially with respect to the dinucleotide. The trans-syn isomer is formed in a SYN-ANTI glycosidic conformation. In this isomer the sugar puckers of both deoxyribose rings are affected and a preference for a pure 2-endo conformation is observed.Abbreviations dTpdT 2-deoxythymidylyl-(35)-2-deoxythymidine - dTp[]dT cyclobutane type photodimers of dTpdT - dTp- and dTp[]- their 5' terminal fragments (fragment A) - -pdT and-[]pdT their 3 terminal fragments (fragment B) - RP-HPLC reversed-phase high-performance liquid chromatography - COSY two-dimensional correlated spectroscopy - 2D NOE two-dimensional nuclear Overhauser spectroscopy