Purine and pyrimidine contents of some desoxypentose nucleic acids

The distribution of purines and pyrimidines in desoxypentose nucleic acids prepared from a variety of animal and plant sources has been studied. 1. The nucleic acids were prepared from calf thymus, calf kidney, sheep spleen, horse spleen, chicken erythrocyte, turtle erythrocyte, trout sperm, shad testes, sea urchin sperm, wheat germ, and Pneumococcus Type III. 2. Separate hydrolyses were carried out for the determination of purines and pyrimidines. These procedures permitted nearly quantitative recovery of nucleic acid phosphorus in many of the preparations examined. 3. In the case of those preparations where a quantitative recovery was obtained it can be concluded that no bases other than adenine, guanine, thymine, and cytosine were present in appreciable amounts. 4. The distribution of purines and pyrimidines in all the nucleic acids studied renders the tetranucleotide hypothesis untenable. 5. The results of the analyses have indicated no great differences in the composition of these nucleic acids with respect to purines and pyrimidines.     

Sensitivity of mitomycin C and nitrogen mustard crosslinks to extreme alkaline conditions

DNA-DNA crosslinks in cells treated with mitomycin C, nitrogen mustard, or decarbamoyl mitomycin C were measured in alkaline isopycnic gradients as a function of pH. Crosslinks from cells treated with mitomycin C and nitrogen mustard, which react with DNA purines, could be detected at pH 12.5 but not at pH 14. No crosslinks from cells treated with decarbamoyl mitomycin C were detected at either pH. Previous studies with cells exposed to psoralen derivatives plus 360 nm light, which produce DNA-DNA crosslinks with pyrimidines, demonstrated stable crosslinks at pH 14. These studies indicate that DNA-DNA crosslinks involving DNA purines are much less stable at high pH than those involving pyrimidines, and that methods involving exposure to extreme alkaline conditions may give inaccurate information for some agents.     

Influence of purines and pyrimidines on cold hardiness of plants. V. Uptake and translocation of purines and pyrimidines in alfalfa

Differential uptake of radioactive purines and pyrimidines by alfalfa leaves was observed. Translocation of radioactive constituents from leaves to stem-crown or root tissues (metabolic sinks) was not proportional to uptake. After 40 days of hardening at low temperatures, ranking of radioactivity levels changed for the base treatments and the change in leaves was different from that in whole plants. Ratios calculated for radioactivity from guanine and cytosine/adenine and uracil for RNA of leaves was twice as large as that for stem-crown or root tissues.More than $\text{3}\text{4}$ of the total radioactivity was found in soluble cytoplasm, although less than 10% of the RNA of hardened plants has been found in this fraction. This has special significance because soluble cytoplasm is the fraction that contains most of the polynucleotide phosphorylase activity and contains 60% of the soluble proteins that have been closely associated with cold tolerance.     

Amino acid catalyzed condensation of purines and pyrimidines with 2-deoxyribose.

Mild heating of aqueous mixtures containing 2-deoxyribose, amino compounds, and purines or pyrimidines produces derivatives of the purines and pyrimidines in high yield. Among the major products formed are 2,3-dideoxy-3-(1'-pyrimidino)pentose and 2,3-dideoxy-3-(9'-purino)pentose. The mechanism of the reaction includes amine-catalzyed dehydration of the alpha, beta positions of the sugar followed by addition of the purine or pyrimidine to the double bond. Rapid addition of purines and pyrimidines to alpha, beta-unsaturated carbonyl compounds (such as acrolin) is a general phenomenon which does not require an amine catalyst. While multiple derivatization of the purines will take place, the N-9 derivative is formed first.     

The Cold Origin of Life: B. Implications Based on Pyrimidines and Purines Produced From Frozen Ammonium Cyanide Solutions

A wide variety of pyrimidines and purineswere identified as products of a dilute frozen ammoniumcyanide solution that had been held at –78°C for 27 years.This demonstrates that both pyrimidines and purines couldhave been produced on the primitive earth in a short time byeutectic concentration of HCN, even though the concentrationof HCN in the primitive ocean may have been low. We suggestthat eutectic freezing is the most plausible demonstratedmechanism by which HCN polymerizations could have producedbiologically important prebiotic compounds.     

Detection of oxidative DNA damage in lymphocytes of patients with Alzheimer's disease.

Oxidative damage to DNA may play an important role in both normal ageing and in neurodegenerative diseases. The deleterious consequences of excessive oxidations and the pathophysiological role of reactive oxygen species have been intensively studied in Alzheimer's disease. Although the role of oxidative stress in the aetiology of Alzheimer's disease is still not clear, the detection of an increased damage status in the cells of patients could have important therapeutic implications. The levels of oxidative damage in peripheral lymphocytes of 24 Alzheimer's disease patients and of 21 age-matched controls were determined by comet assay applied to freshly isolated blood samples with oxidative lesion-specific DNA repair endonucleases (endonuclease III for oxidized pyrimidines, formamidopyrimidine glycosylase for oxidized purines). It was demonstrated that Alzheimer's disease is associated with elevated levels of oxidized pyrimidines and purines (p<0.0001) as compared with age-matched control subjects. It was also demonstrated that the comet assay is useful as a biomarker of oxidative DNA damage when used with oxidative lesion-specific enzymes.     

抗寒锻炼中不同抗寒性小麦细胞膜糖蛋白的细胞化学研究

本研究根据植物细胞的特点,修改了在动物和人体细胞方面立的酶标Con A的电镜细胞化学方法,成功地展现了2个不同抗寒性冬小麦品种幼苗在抗寒锻炼和脱锻炼过程中细胞膜系统上糖蛋白的分布动态,显示与Con A连接的标志酶-辣根过氧化物酶活性的反应产物呈颗粒状分散分布在质膜、内质网、核膜及液泡膜的一些部位上,揭示糖蛋白在冬小麦细胞膜系统上的分布似有其特定的位点。经抗寒锻炼后,强抗寒性品种燕大1817细胞内的糖蛋白在内质网和核膜上的分布量明显地增加;同时,几乎所有的胞间连丝通道中都有糖蛋白的分布。脱锻炼后,内质网和核膜上的糖蛋白分布量又减少,胞间连丝通道中的糖蛋白也消失,基本上回复到抗寒锻炼前的分布状态。抗寒性弱的冬小麦品种郑州39-1幼苗在同样的抗寒锻炼和脱锻炼过程中不产生这些明显的变化。这些结果说明,抗寒锻炼中内质网和核膜上糖蛋白分布量的增加,以及糖蛋白输入胞间连丝的动态变化是与植物抗寒力的提高和保持稳定密切相关的。     

HOS1, a genetic locus involved in cold-responsive gene expression in arabidopsis.

Low-temperature stress induces the expression of a variety of genes in plants. However, the signal transduction pathway(s) that activates gene expression under cold stress is poorly understood. Mutants defective in cold signaling should facilitate molecular analysis of plant responses to low temperature and eventually lead to the identification and cloning of a cold stress receptor(s) and intracellular signaling components. In this study, we characterize a plant mutant affected in its response to low temperatures. The Arabidopsis hos1-1 mutation identified by luciferase imaging causes superinduction of cold-responsive genes, such as RD29A, COR47, COR15A, KIN1, and ADH. Although these genes are also induced by abscisic acid, high salt, or polyethylene glycol in addition to cold, the hos1-1 mutation only enhances their expression under cold stress. Genetic analysis revealed that hos1-1 is a single recessive mutation in a nuclear gene. Our studies using the firefly luciferase reporter gene under the control of the cold-responsive RD29A promoter have indicated that cold-responsive genes can be induced by temperatures as high as 19 degrees C in hos1-1 plants. In contrast, wild-type plants do not express the luciferase reporter at 10 degrees C or higher. Compared with the wild type, hos1-1 plants are l ess cold hardy. Nonetheless, after 2 days of cold acclimation, hos1-1 plants acquired the same degree of freezing tolerance as did the wild type. The hos1-1 plants flowered earlier than did the wild-type plants and appeared constitutively vernalized. Taken together, our findings show that the HOS1 locus is an important negative regulator of cold signal transduction in plant cells and that it plays critical roles in controlling gene expression under cold stress, freezing tolerance, and flowering time.     

Cold hardiness in summer and winter diapause and post-diapause pupae of the cabbage armyworm, Mamestra brassicae L. under temperature acclimation

Cold hardiness and biochemical changes were investigated in winter and summer pupae of the cabbage armyworm Mamestra brassicae at the diapause and post-diapause stages under temperature acclimation. Diapause pupae were successively acclimated to 25, 20 and then 10 degrees C (warm-acclimated group). Pupae at the diapause and post-diapause stages were successively acclimated to 5, 0, -5 and then -10 degrees C (cold-acclimated groups). Supercooling point values in winter and summer pupae remained constant regardless of the diapause stages and acclimated temperatures. Warm-acclimated pupae at the diapause stage did not survive the subzero temperature exposure, whereas, cold-acclimated pupae achieved cold hardiness to various degrees. Winter pupae were more cold hardy than summer pupae, and pupae at the post-diapause stage were more cold hardy than those at the diapause stage. Trehalose contents in winter pupae rose under cold acclimation. Summer pupae accumulated far lower trehalose contents than winter pupae, with the maximal level occurring in winter pupae at the post-diapause stage. Glycogen content remained at a high level in diapause pupae after warm acclimation, whereas it decreased after cold acclimation. Alanine, the main free amino acid in haemolymph after cold acclimation, increased at lower temperatures in both diapause and post-diapause pupae, but the increase was greater in the diapause pupae. These results suggest that cold hardiness is more fully developed in winter pupae than in summer pupae, and cold acclimation provides higher cold hardiness in winter pupae at the post-diapause stage than at the diapause stage.     

The determination of absolute electron affinities of the purines and pyrimidines in DNA and RNA from reversible reduction potentials.

We report the reversible reduction potentials of the purines and pyrimidines of DNA and RNA. These were determined in dimethylsulfoxide using cyclic voltammetry. The absolute electron affinities have been determined from these reduction potentials by calibration with the absolute electron affinities for acridine and anthracene measured in the gas phase. These are the first experimentally determined values of the electron affinities of these purines and pyrimidines and are: Guanine = 1.51 eV, Adenine = 0.95 eV, Uracil = 0.80 eV, Thymine = 0.79 eV and Cytosine = 0.56 eV.     

The role of electron donors and acceptors in base stacking in DNA and RNA.

The role of donor-acceptor interactions in base pair stacking in DNA and RNA has been minimized because of the perceived low or negative electron affinities of the purines and pyrimidines. The use of the electron capture detector was among the first methods for measuring electron affinities in the gas phase. Recently, the experimental determination of electron affinities has been extended and improved. Now, there are data for similar compounds in the literature which enable us to estimate electron affinities for purines and pyrimidines. These values are significant, and positive, such that donor-acceptor interactions can, and indeed should play a role in the stacking of bases in nucleic acids.     

Purine and pyrimidine inhibitors of arginase.

1. Adenosine, inosine, adenine and uric acid are competitive inhibitors and cytidine and cytosine noncompetitive inhibitors of bovine liver arginase (L-arginine amidinohydrolase, EC 3.5.3.1). 2. The affinity of the enzyme for these inhibitors was 10--100 times as great as for substrate in terms of Ki versus Km. 3. These nucleic acid metabolites may thus function in vivo to regulate the urea cycle. 4. Several naturally occuring competitive and noncompetitive inhibitors of arginase of unknown structure have been isolated from plant and animal tissue. From their properties and methods of isolation, they may be the purines and pyrimidines herein described. 5. These purines and pyrimidines have no effect on tryptic hydrolysis.     

The Ultraviolet Light Inactivation of ΦX174 Bacteriophage at Different wave Lengths and pH's

The bacterial virus, ΦX174, which contains a single strand of DNA has been inactivated by different wave lengths of monochromatic ultraviolet light at pH 7, 2, and 12. The action spectra for inactivation at these three pH's all showed minima at 2400 A rather than at 2300 A, which is the characteristic absorption minimum of DNA. The shapes of the action spectra have been analyzed in terms of the effects of absorbed light on the pyrimidines and purines rather than the effect on nucleoprotein. In this interpretation the pyrimidines are at least 2 to 3 times more sensitive than the purines. The quantum yield for inactivation of the virus at 2650 A and pH 7 is 0.006. The quantum efficiency for quanta absorbed in the pyrimidines is 0.0085 and for the purines 0.0035. It is pointed out that action spectra for single- and double-stranded polynucleotides should have minima at different wave lengths, and that this difference may be used to distinguish between these two configurations in vivo.     

Chemical evolution XXIX. Pyrimidines from hydrogen cyanide.

Dilute (0.1 M) solutions of HCN condense to oligomers at pH 8-9. Hydrolysis of these oligomers at pH 8.5 or with 6 N HCl yields 4,5-dihydroxypyrimidine, as the most abundant pyrimidine product along with orotic acid and 5-hydroxyuracil. These results, together with the earlier data, demonstrate that the three major nitrogen-containing classes of biomolecules could have originated from HCN on the primitive earth. The observation of the formation of orotic acid and 4-aminoimidazole-5-carboxamide by the hydrolysis of the HCN oligomers suggests that once the initially formed pyrimidines and purines were consumed, those life forms persisted which evolved enzymes for conversion of these intermediates to the pyrimidines and purines present in contemporary RNA.     

Growth requirements and the effect of organic components of the synthetic medium on the biosynthesis of the antibiotic nisin in Streptococcus lactis strain.

A synthetic medium SM-3 has been elaborated for growth of Streptococcus lactis strain 51, which contains the minimal number of organic components required for the growth of this strain and nisin production. This medium contains 9 amino acids, 4 vitamins from B group, glucose and mineral salts. Addition of biotin to the medium stimulated the growth of the strain, while the addition of purines and/or pyrimidines had no effect. Hitherto biotin has been considered to be necessary for the growth of S. lactis and purines and pyrimidines were believed to stimulate the growth of these bacteria. In strain 51 the minimal requirements for growth were also the minimal requirements for nisin biosynthesis. Strain 51 produced 3-4 times less nisin in medium SM-3 than in a complex medium. The addition of one of four amino acids (serine, proline, cysteine or cystine) to SM-3 medium increased the amount of antibiotic produced. The addition of all four amino acids simultaneously, caused formation of nisin amounts similar to those produced in complex medium.     

The relative hardening of roots and shoots and the influence of day-length during hardening in perennial ryegrass

The influence of long and short days during the hardening period on the cold hardiness of perennial ryegrass seedlings was studied as was the relative hardiness of roots and shoots. Hardiness was assessed by the electrolyte release method which was a measure of the amount of damage subsequent to low temperature treatment. Long days promoted hardiness in shoots of Pax 0tofte plants and in one case under short days the roots were found to be hardy. Generally roots were less hardy than shoots in Pax 0tofte and S23 plants hardened under long days for 2 wk. When hardened at the fourth leaf stage for 2 wk at + 5 ^oC under long day conditions, Pax 0tofte plants were more hardy than those of S23. The long day effect on hardiness was arrived at more rapidly, there being no difference in hardiness after 3 wk in Pax 0tofte hardened under long or short days, whereas a significant degree of hardening was observed after 1 wk of hardening under long days at – 4 ^oC. The results obtained are discussed in relation to winter kill of grasses in the West of Scotland, and it is considered that root damage is not an important factor in causing winter kill. The promotive effect of long days on hardiness when hardening commences in late autumn is considered an advantage in temperate regions as it may also allow early frosts to be withstood.     

In vitro screening for cold hardiness of raspberry cultivars

Raspberry (Rubus idaeus L.) cultivars ‘Festival’, ‘Titan’ and ‘Willamette’ were cultured in vitro on three different media: (A) MS medium supplemented with 1.0 mg l^-1 BAP and 0.1 mg l^-1 IBA, (B) MS medium without growth regulators, and (C) MS medium with reduced sucrose (10 g l^-1), and exposed to different low temperature acclimation treatments: (1) control, no acclimation, (2) 1 week at +15 °C, 1 week at +2 °C, 24 h at -2 °C and 3 days at +2 °C, and (3) 2 weeks at +15 °C, 2 weeks at +2 °C, 24 h at −2 °C and 3 days at +2 °C. After acclimation, shoot moisture content was measured, and cold hardiness (LT₅₀) was determined by controlled freezing. Shoot moisture content was generally lower on culture medium B compared to the other media, but not affected by acclimation treatment. In non-acclimated plants, medium composition had no effect on cold hardiness and no cultivar differences in hardiness were observed. After acclimation, plants on culture medium B were on average more cold hardy than on the other media. Acclimation treatment 3 on media A and B allowed the best discrimination between the hardy cultivar ‘Festival’ and less cold hardy ‘Titan’ and ‘Willamette’. When acclimation treatments were tested further using 11 raspberry cultivars with different levels of cold hardiness, discrimination between cultivars was satisfactory only after acclimation treatment 3 on culture medium B. This revised version was published online in June 2006 with corrections to the Cover Date.     

Thermal denaturation profiles and gel mobility shift analysis of oligodeoxynucleotide triplexes.

Oligodeoxypurine- and oligodeoxypyrimidine-containing strands were mixed under conditions conducive to the formation of triple stranded assemblies. The mixtures were characterized both by their UV absorbance change with increasing temperature and by their mobility in non-denaturing polyacrylamide gels. Duplexes 34 bp long containing 15 central purines on one strand and 15 complementary pyrimidines on the other strand yielded new melting transitions and showed different gel mobilities upon combination with oligopyrimidine 15-mers. The dependence of the thermal denaturation profiles on pH, salt concentration, GC content, strand orientation, base mismatches, and strand length was investigated.     

Growth responses to nutrients of an auxotroph and a prototroph of a predatory fungus

The growth responses of a prototroph and an auxotroph of Arthrobotrys dactyloides were compared, on several nutrient media. The prototroph can utilize a variety of nitrogenous compounds almost equally, but the auxotroph has an exacting requirement for several amino acids together. Both strains utilize sucrose best among the three sugars tested as a C-source but the prototroph responds strongly to phospholipid, in addition. They differ in their needs for purines, pyrimidines and B vitamins.     

The cometary connection with prebiotic chemistry

Amino-acids, purines and pyrimidines may have been formed in space and brought down to Earth by comets during the final stage of the Earth's cold accretion from dust. Present-day comets seem to be the remnants of the building blocks of the early solar system, put for 4.6 billion years in parking orbits in the deep cold of space by the same process of orbital diffusion that brought a veneer of cometary material to the primitive Earth. The second part of the present review examines the chemical nature of comets as can be reconstructed from (so far) very incomplete evidence.