bluuebunny/crossref_metadata_2025 huggingface dataset:
Interaction location outweighs the competitive advantage of numerical superiority inCebus capucinusintergroup contests
Authors: Crofoot Margaret C. , Gilby Ian C. , Wikelski Martin C. , Kays Roland W.
Published: January 2008

Numerical superiority confers a competitive advantage during contests among animal groups, shaping patterns of resource access, and, by extension, fitness. However, relative group size does not always determine the winner of intergroup contests. Smaller, presumably weaker social groups often defeat their larger neighbors, but how and when they are able to do so remains poorly understood. Models of competition between individuals suggest that location may influence contest outcome. However, because of the logistical difficulties of studying intergroup interactions, previous studies have been unable to determine how contest location and group size interact to shape relationships among groups. We address this question by using an automated radio telemetry system to study intergroup interactions among six capuchin monkey (Cebus capucinus) social groups of varying sizes. We find that the odds of winning increase with relative group size; one additional group member increases the odds of winning an interaction by 10%. However, this effect is not uniform across space; with each 100 m that a group moves away from the center of its home range, its odds of winning an interaction decrease by 31%. We demonstrate that contest outcome depends on an interaction between group size and location, such that small groups can defeat much larger groups near the center of their home range. The tendency of resident groups to win contests may help explain how small groups persist in areas with intense intergroup competition.
Preferred side-chain constellations at antiparallel coiled-coil interfaces
Authors: Hadley Erik B. , Testa Oliver D. , Woolfson Derek N. , Gellman Samuel H.
Published: January 2008

Reliable predictive rules that relate protein sequence to structure would facilitate postgenome predictive biology and the engineering and
de novo
design of peptides and proteins. Through a combination of experiment and analysis of the protein data bank (PDB), we have deciphered and rationalized new rules for helix–helix interfaces of a common protein-folding and association motif, the antiparallel dimeric coiled coil. These interfaces are defined by a specific pattern of interactions among largely hydrophobic side chains often referred to as knobs-into-holes (KIH) packing: a knob from one helix inserts into a hole formed by four residues on the partner. Previous work has focused on
lateral
interactions within the KIH motif, for example, between an
a
position on one helix and a
d′
position on the other in an antiparallel coiled coil. We show that
vertical
interactions within the KIH motif, such as
a′
-
a–a′
, are energetically important as well. The experimental and database analyses concur regarding preferred vertical combinations, which can be rationalized as leading to favorable side-chain interactions that we call
constellations
. The findings presented here highlight an unanticipated level of complexity in coiled-coil interactions, and our analysis of a few specific constellations illustrates a general, multipronged approach to addressing this complexity.
Single-shot detection of bacterial endospores via coherent Raman spectroscopy
Authors: Pestov Dmitry , Wang Xi , Ariunbold Gombojav O. , Murawski Robert K. , Sautenkov Vladimir A. , Dogariu Arthur , Sokolov Alexei V. , Scully Marlan O.
Published: January 2008

Recent advances in coherent Raman spectroscopy hold exciting promise for many potential applications. For example, a technique, mitigating the nonresonant four-wave-mixing noise while maximizing the Raman-resonant signal, has been developed and applied to the problem of real-time detection of bacterial endospores. After a brief review of the technique essentials, we show how extensions of our earlier experimental work [Pestov D,
et al.
(2007)
Science
316:265–268] yield single-shot identification of a small sample of
Bacillus subtilis
endospores (≈10
4
spores). The results convey the utility of the technique and its potential for “on-the-fly” detection of biohazards, such as
Bacillus anthracis
. The application of optimized coherent anti-Stokes Raman scattering scheme to problems requiring chemical specificity and short signal acquisition times is demonstrated.
Platelets prevent IFN-α/β-induced lethal hemorrhage promoting CTL-dependent clearance of lymphocytic choriomeningitis virus
Authors: Iannacone Matteo , Sitia Giovanni , Isogawa Masanori , Whitmire Jason K. , Marchese Patrizia , Chisari Francis V. , Ruggeri Zaverio M. , Guidotti Luca G.
Published: January 2008

We found that mice infected with different isolates of lymphocytic choriomeningitis virus (LCMV) develop a mild hemorrhagic anemia, which becomes severe and eventually lethal in animals depleted of platelets or lacking integrin β3. Lethal hemorrhagic anemia is mediated by virus-induced IFN-α/β that causes platelet dysfunction, mucocutaneous blood loss and suppression of erythropoiesis. In addition to the life-threatening hemorrhagic anemia, platelet-depleted mice fail to mount an efficient cytotoxic T lymphocyte (CTL) response and cannot clear LCMV. Transfusion of functional platelets into these animals reduces hemorrhage, prevents death and restores CTL-induced viral clearance in a manner partially dependent on CD40 ligand (CD40L). These results indicate that, upon activation, platelets expressing integrin β3 and CD40L are required for protecting the host against the induction of an IFN-α/β-dependent lethal hemorrhagic diathesis and for clearing LCMV infection through CTLs.
The Actomyosin Ring Recruits Early Secretory Compartments to the Division Site in Fission Yeast
Authors: Vjestica Aleksandar , Tang Xin-Zi , Oliferenko Snezhana
Published: January 2008

The ultimate goal of cytokinesis is to establish a membrane barrier between daughter cells. The fission yeast Schizosaccharomyces pombe utilizes an actomyosin-based division ring that is thought to provide physical force for the plasma membrane invagination. Ring constriction occurs concomitantly with the assembly of a division septum that is eventually cleaved. Membrane trafficking events such as targeting of secretory vesicles to the division site require a functional actomyosin ring suggesting that it serves as a spatial landmark. However, the extent of polarization of the secretion apparatus to the division site is presently unknown. We performed a survey of dynamics of several fluorophore-tagged proteins that served as markers for various compartments of the secretory pathway. These included markers for the endoplasmic reticulum, the COPII sites, and the early and late Golgi. The secretion machinery exhibited a marked polarization to the division site. Specifically, we observed an enrichment of the transitional endoplasmic reticulum (tER) accompanied by Golgi cisternae biogenesis. These processes required actomyosin ring assembly and the function of the EFC-domain protein Cdc15p. Cdc15p overexpression was sufficient to induce tER polarization in interphase. Thus, fission yeast polarizes its entire secretory machinery to the cell division site by utilizing molecular cues provided by the actomyosin ring.
Persistence and Spatial Autocorrelation of Clones ofErysiphe necatorOverwintering as Mycelium in Dormant Buds in an Isolated Vineyard in Northern Italy
Authors: Cortesi P. , Pizzatti C. , Bertocchi D. , Milgroom M. G.
Published: January 2008

The population structure of the grape powdery mildew fungus, Erysiphe necator (formerly Uncinula necator), has been hypothesized to vary from being clonal to highly diverse and recombining. We report here on the structure of an E. necator population sampled during a 4-year period from an isolated vineyard in northern Italy (Voghera, Pavia Province). We obtained 54 isolates of E. necator that overwintered asexually as mycelium in grapevine buds and caused severe symptoms on the emerging shoots, known as flag shoots. All isolates were genotyped for mating type, four multilocus polymerase chain reaction (PCR)-based markers (a total of 64 loci were scored), and two single-copy loci designed to identify genetic subgroups in E. necator. All isolates had the same mating type and single-locus alleles that correlate to isolates from flag shoots in other areas. Only 2 of the 64 loci scored from multilocus markers were polymorphic; 46 of the 54 isolates had the same multilocus haplotype. Seven isolates had a second haplotype that was recovered over 3 years, and only a single isolate was found with a third haplotype. Both variant haplotypes differed from the main clonal haplotype by single loci. Spatial autocorrelation analyses showed that vines with flag shoots were not aggregated within years, but they were aggregated between consecutive years. These results demonstrate that this subpopulation of E. necator on flag shoots is composed of a single clonal lineage that has persisted for at least 4 years. We speculate that the lack of diversity in the flag shoot subpopulation in this vineyard is the result of restricted immigration from surrounding areas and genetic drift operating through founder effects and periodic bottlenecks. We propose a model that integrates epidemiology and population genetics to explain the variation observed in genetic structure of E. necator flag shoot subpopulations from different vineyards or viticultural regions.
Apple Proliferation Resistance in Apomictic Rootstocks and Its Relationship to Phytoplasma Concentration and Simple Sequence Repeat Genotypes
Authors: Bisognin C. , Schneider B. , Salm H. , Grando M. S. , Jarausch W. , Moll E. , Seemüller E.
Published: January 2008

In an effort to select and characterize apple rootstock resistant to apple proliferation (AP), progenies from seven apomictic rootstock selections and their parental apomictic species, Malus sieboldii and M. sargentii, were compared to standard stocks M 9 and M 11. Seedlings derived from open pollinated mother plants were grafted with cv. Golden Delicious and grown under natural infection conditions. The progenies differed greatly in resistance to the AP agent ‘Candidatus Phytoplasma mali’. Progenies of M. sieboldii and its descendent rootstock selections D2212, 4608, 4551, and D1131 showed a high level of resistance, whereas progenies of M. sargentii and its descendent selections D1111 and C1828 proved susceptible. M 9 and M 11 showed an intermediate level of resistance. Phytoplasma titer in roots of the M. sieboldii and M. sargentii progeny groups was similarly low, whereas the concentration in the standard stocks was 100 to 5,000 times higher. In trees on most of the resistant stocks, only a minority was colonized in the scion, while in trees on susceptible and standard stocks, infection rate was often higher. Also, the titer in the top of trees on resistant stocks was usually lower than in trees on susceptible and standard stocks. Four progenies derived from open pollinated M. sieboldii and M. sieboldii descendents were subjected to DNA typing using simple sequence repeat (SSR) markers. This study revealed that the selected groups consisted mainly of mother-like plants (apomicts) and type I hybrids (unreduced mother genotype plus one male allele at each locus). Type II hybrids (full recombinants) and autopollinated offspring were rare. In the 4608 progeny, trees grown on type I hybrid rootstocks were significantly less affected than trees on mother-like stocks. In other progenies with fewer or no type I hybrids, trees on type II hybrids and autopollinated offspring suffered considerably more from disease than trees on mother-like stocks.
Spatiotemporal Analysis of Spread of Infections by Verticillium dahliae Pathotypes Within a High Tree Density Olive Orchard in Southern Spain
Authors: Navas-Cortés J. A. , Landa B. B. , Mercado-Blanco J. , Trapero-Casas J. L. , Rodríguez-Jurado D. , Jiménez-Díaz R. M.
Published: January 2008

The development of Verticillium wilt epidemics in olive cv. Arbequina was studied from November 1999 to May 2003 in a drip-irrigated, nontillage orchard established in a soil without a history of the disease at Córdoba, southern Spain. Disease incidence measured at 1-month-intervals increased from 0.2 to 7.8% during this period. Verticillium dahliae infecting the trees was characterized as defoliating (D) or nondefoliating (ND) pathotypes by a specific, multiplex-polymerase chain reaction (PCR) assay. Of the symptomatic trees, 87.2 and 12.8% were infected by the D or ND pathotypes, respectively. Dynamics of disease incidence were described by a generalized logistic model with a multiple sigmoid pattern. In the fitted model, the infection rate was highest in the winter to spring period and decreased to minimum values in the summer to fall period. Binary data of disease incidence was analyzed for point pattern and spatial correlation, either directly or after parsing them in contiguous quadrats. Overall, ordinary runs analysis indicated a departure from randomness of disease within rows. The binomial index of dispersion, interclass correlation, and Taylor's power law for various quadrat sizes suggested aggregation of diseased trees within the quadrat sizes tested. Spatial analysis by distance indices showed a nonrandom arrangement of quadrats containing infected trees. Spatial pattern was characterized by the occurrence of several clusters of infected trees. Increasing clustering over time was generally suggested by stronger values of clustering index over time and by the increase in the size of patch clusters. Significant spatial association was found in the clustering of diseased trees over time across cropping seasons; however, clustering was significant only for infections by D V. dahliae, indicating that infections by the D pathotype were aggregated around initial infections. The number and size of clusters of D V. dahliae-infected trees increased over time. Microsatellite-primed PCR assays of a representative number of V. dahliae isolates from diseased trees indicated that the majority of infecting D isolates shared the fingerprinting profile with D V. dahliae isolated from soil of a naturally infested cotton field in close proximity to the orchard, suggesting that short distance dispersal of the pathogen from this soil to the olive orchard may have occurred.
Characterization of Genetic and Biochemical Mechanisms of Fludioxonil and Pyrimethanil Resistance in Field Isolates of Penicillium digitatum
Authors: Kanetis L. , Förster H. , Jones C. A. , Borkovich K. A. , Adaskaveg J. E.
Published: January 2008

Genetic and biochemical mechanisms of fludioxonil and pyrimethanil resistance in isolates of Penicillium digitatum were evaluated and compared to those characterized in other fungi. Resistant isolates were naturally occurring in packinghouses and were not associated with crop losses. For the phenylpyrrole fludioxonil, EC50 values were 0.02 to 0.04 μg/ml for sensitive, 0.08 to 0.65 μg/ml for moderately resistant (MR), and >40 μg/ml for highly resistant (HR) isolates. Two fludioxonil-sensitive isolates evaluated were also significantly more sensitive to the unrelated dicarboximide fungicide iprodione, that also disrupts osmotic regulation, than the MR and HR isolates. There was no consistent relationship, however, between the HR and MR isolates and their sensitivity to iprodione or osmotic stress. Although, two nucleotide substitutions were found in a sequence analysis of the N-terminal amino acid repeat region of the os-1-related histidine kinase gene among isolates of P. digitatum, these were not correlated with fludioxonil resistance. In mycelia not exposed to fludioxonil, the amount of phosphorylated OS-2-related protein (PdOS-2) was higher in fludioxonil-sensitive isolates and lowest in the HR isolate. An increase in PdOS-2 was observed for sensitive and resistant isolates after exposure to fludioxonil. In addition, glycerol content in untreated mycelia of the fludioxonil-sensitive isolate was significantly higher than in resistant isolates. After exposure to fludioxonil, glycerol concentrations significantly increased in the sensitive and MR isolates, but not in the HR isolate. Thus, our studies indicate that the mode of action of fludioxonil in P. digitatum is probably the mitogen-activated protein kinase pathway that stimulates glycerol synthesis in sensitive and MR isolates. The general suppression of this pathway in resistant isolates was supported by the fact that growth and sporulation of MR and HR isolates were significantly reduced from that of sensitive isolates. In studies on the mode of action of anilinopyrimidines (AP), EC50 values for mycelial growth of P. digitatum and the previously characterized Botrytis cinerea were determined for cyprodinil and pyrimethanil using a defined culture medium without and with the addition of selected amino acids and homocysteine. The addition of amino acids resulted in a reduced toxicity of the two AP fungicides in both fungi, but the effect of each additive was significantly lower for P. digitatum than for B. cinerea. This suggests that methionine biosynthesis is not the primary target site of APs in P. digitatum.
Adaptation to Fungicides in Monilinia fructicola Isolates with Different Fungicide Resistance Phenotypes
Authors: Luo Chao-Xi , Schnabel Guido
Published: January 2008

The ability to develop fungicide resistance was assessed in Monilinia fructicola isolates with different fungicide sensitivity phenotypes by adapting mycelium and conidia to increasing concentrations of selective fungicides and UV mutagenesis. Results showed that adaptation to Quinone outside inhibitor (QoI) fungicide azoxystrobin and sterol demethylation inhibitor (DMI) fungicide propiconazole was more effective in conidial-transfer experiments compared to mycelial-transfer experiments. DMI-resistant (DMI-R) isolates adapted to significantly higher doses of azoxystrobin in both, mycelial- and conidial-transfer experiments compared to benzimidazole-resistant (BZI-R) and sensitive (S) isolates. Adaptation to propiconazole in conidial-transfer experiments was accelerated in BZI-R isolates when a stable, nonlethal dose of 50 μg/ml thiophanate-methyl was added to the selection medium. One of two azoxystrobin-resistant mutants from DMI-R isolates did not show any fitness penalties; the other isolate expired before further tests could be carried out. The viable mutant caused larger lesions on detached peach fruit sprayed with azoxystrobin compared to the parental isolate. The azoxystrobin sensitivity of the viable mutant returned to baseline levels after the mutant was transferred to unamended medium. However, azoxystrobin resistance recovered quicker in the mutant compared to the corresponding parental isolate after renewed subculturing on medium amended with 0.2 and 1 μg/ml azoxystrobin; only the mutant but not the parental isolate was able to adapt to 5 μg/ml azoxystrobin. In UV mutagenesis experiments, the DMI-R isolates produced significantly more mutants compared to S isolates. All of the UV-induced mutants showed stable fungicide resistance with little fitness penalty. This study indicates the potential for QoI fungicide resistance development in M. fructicola in the absence of a mutagen and provides evidence for increased mutability and predisposition to accelerated adaptation to azoxystrobin in M. fructicola isolates resistant to DMI fungicides.
Genetic Structure of Fusarium pseudograminearum Populations from the Australian Grain Belt
Authors: Bentley Alison R. , Leslie John F. , Liew Edward C. Y. , Burgess Lester W. , Summerell Brett A.
Published: January 2008

Crown rot, caused by the fungus Fusarium pseudograminearum (teleomorph Gibberella coronicola) is a major disease of wheat in the Australian grain belt. However, there is little information available on the population structure of this pathogen. We measured genetic diversity as assessed with amplified fragment length polymorphism (AFLP) analysis within and between populations of F. pseudograminearum from northeastern, south central, and southwestern regions of the Australian grain belt. Amongst the 217 isolates, 176 haplotypes were identified and grouped into two main clusters. One cluster contained isolates from populations in northeastern Australia, and the other cluster contained isolates from populations in south central and southwestern Australia. The southern populations were distinguished from the northeastern populations by higher levels of population differentiation (Gst) between them and genetic identity amongst the regional populations. We hypothesize that the F. pseudograminearum populations from northeastern and southern Australia are independent, which could result from different founding events or from geographic isolation and the accumulation of genetic differences due to genetic drift and/or selection.
Technical assistance in the world of London science, 1850–1900
Authors: Gay Hannah
Published: January 2008

Examples of technical assistance in a range of London settings are discussed in this paper. Skilled trades people, apprentices, lab boys and girls, family members, research students, research assistants, and laboratory technicians were, in different ways, all important to the organization of scientific work in this period. To illustrate this point, examples of work performed in trades shops, academic laboratories, entrepreneurial businesses and private laboratories are given. The examples demonstrate not only the complex and collective nature of scientific work, but also something of the social interactions of scientists and their assistants. Of especial note is the dependence of scientists on people who worked in the skilled trades.
Keeping the culture alive: the laboratory technician in mid-twentieth-century British medical research
Authors: Tansey E.M
Published: January 2008

This paper reports results from a detailed study of the careers of laboratory technicians in British medical research. Technicians and their contributions are very frequently missing from accounts of modern medicine, and this project is an attempt to correct that absence. The present paper focuses almost entirely on the Medical Research Council's National Institute for Medical Research in North London, from the first proposal of such a body in 1913 until the mid 1960s. The principal sources of information have been technical staff themselves, largely as recorded in an extensive series of oral history interviews. These have covered a wide range of issues and provide valuable perspectives about technicians' backgrounds and working lives.
Water Transport by Aquaporins in the Extant Plant Physcomitrella patens
Authors: Liénard David , Durambur Gaëlle , Kiefer-Meyer Marie-Christine , Nogué Fabien , Menu-Bouaouiche Laurence , Charlot Florence , Gomord Véronique , Lassalles Jean-Paul
Published: January 2008

Although aquaporins (AQPs) have been shown to increase membrane water permeability in many cell types, the physiological role of this increase was not always obvious. In this report, we provide evidence that in the leafy stage of development (gametophore) of the moss Physcomitrella patens, AQPs help to replenish more rapidly the cell water that is lost by transpiration, at least if some water is in the direct vicinity of the moss plant. Three AQP genes were cloned in P. patens: PIP2;1, PIP2;2, and PIP2;3. The water permeability of the membrane was measured in protoplasts from leaves and protonema. A significant decrease was measured in protoplasts from leaves and protonema of PIP2;1 or PIP2;2 knockouts but not the PIP2;3 knockout. No phenotype was observed when knockout plants were grown in closed petri dishes with ample water supply. Gametophores isolated from the wild type and the pip2;3 mutant were not sensitive to moderate water stress, but pip2;1 or pip2;2 gametophores expressed a water stress phenotype. The knockout mutant leaves were more bent and twisted, apparently suffering from an important loss of cellular water. We propose a model to explain how the AQPs PIP2;1 and PIP2;2 delay leaf dessication in a drying atmosphere. We suggest that in ancestral land plants, some 400 million years ago, APQs were already used to facilitate the absorption of water.
Calcium carbonate cementation of sandstones
Authors: FLEMING NIALL
Published: January 2008

Much effort has been expended in recent years on determining the factors influencing calcite cementation of sandstones, partly out of academic curiosity and partly because of the important influence these cements have on production from hydrocarbon reservoirs. Calcite cementation may occur pervasively throughout a sandstone sequence or be concentrated in certain horizons within which growth may be as concretions. We are only now beginning to understand the factors governing the growth and distribution of carbonate concretions in sandstones.
The local geologist 13: A beginner's guide to the field study of sedimentary rocks
Authors: KERSHAW STEVE , KEELING MIKE
Published: January 2008

Geology is primarily afield study, and no matter what information is collected from detailed study of hand specimens and thin sections in the laboratory, this must be related to the outcrops in order to develop a geological interpretation of a sequence of rocks. Here we focus on the type of information that should be collected when studying sedimentary rocks in the field, and highlight the main techniques employed.
Evaluation of Association Constants from Fluorescence Data: A Corrected Method*
Authors: Lissit E. A. , Gunthe G. , Zanocco A. L.
Published: January 2008

An equation is proposed for the evaluation of partition or association constants from fluorescence properties (such as spectrum shape or anisotropy) whose values are not linearly related to the solute distribution. The proposed procedure is applied to the binding of pyrene to β‐cyclodextrin (employing the I1/I3 relationship and fluorescence anisotropy) and to the association of pyrene to dioctadecyldimethylammonium small unilamellar vesicles (sonicated) and large unilamellar vesicles (injected). The results obtained in the latter system indicate that the pyrene partition constant between the vesicles and the aqueous medium is nearly 10 times larger in the small vesicles.
Larval Tenebrio molitor (Coleoptera: Tenebrionidae) Fat Body Extracts Catalyze Firefly D‐Luciferin‐ and ATP‐Dependent Chemiluminescence: A Luciferase‐like Enzyme*
Authors: Viviani Vadim R. , Bechara Eteivino J. H.
Published: January 2008

Ultraweak light emission was detected upon injection of firefly luciferin into live Tenebrio larvae. A chemilumi‐nescent enzymatic activity dependent on molecular oxygen, D‐luciferin and MgATP was then isolated from larval fat body extracts by precipitation with 70% ammonium sulfate. D‐Luciferin and ATP can be replaced by luciferyl‐adenylate. Pyrophosphate is a main product from the chemiluminescent reaction. The in vitro chemiluminescence intensity was not affected by peroxidase inhibitors such as N3−‐ (0.5 mM) and CN− (1 mM), attesting to its nonperoxidatic nature but was strongly inhibited by AMP (1 mM), luciferin 6′‐ethyl ether (1 mM) and sodium pyrophosphate (2 mM), well‐known firefly lucifer‐ase inhibitors. Some physical‐chemical properties of this enzymatic activity were similar to those of firefly lucif‐erase (KMATP = 195 μM; K0.5 luciferin ‐ 0.8 mM; optimum pH 8.5; δmax= 610 nm at pH 8.5; firefly lucifer‐ase: δmax= 565 nm at pH 8.0 and 619 mm at pH 6.0), but the chemiluminescence was not affected by addition of polyclonal antibodies raised against Photinus pyralis luciferase. These data suggest that this chemiluminescence results from a ligase with luciferase activity.
Investigations of Cylindrical Reaction Cavities from Ordered Phases of Alkyl Alkanoates and Their Influence on Some Norrish‐Yang and Photo‐Fries Reactions*
Authors: Baldvins Jon E. , Cui Changxing , Weisst Richard G.
Published: January 2008

The Norrish‐Yang photochemistry of three isomeric p‐alkyl alkanophenones (p‐propyl nonadecanophenone, p‐pentyl heptadecanophenone and p‐octyl tetradecano‐phenone) and the photo‐Fries reactions of 2‐naphthyl myristate have been investigated in the ordered (layered) phases of three isomeric alkyl alkanoates. Comparisons of photoproduct selectivity for irradiation of one substrate in the isotropic and ordered phases of one host ester provide information concerning the influence of the cylindrically shaped reaction cavities on the relative motions and conformational changes necessary to convert the reactants to products. Comparisons of photoproduct distributions from one substrate in comparable phases of two or more esters provide details concerning the “wall stiffness” and importance of functional group interactions of the reaction cavities. Finally, comparisons using one substrate and two ordered phases of the same ester indicate the role of wall stiffness on photoproduct selectivity. The results show that the course of the photochemical reactions can be controlled effectively within the ordered media and provide an indication of how to design and select ordered media to effect other photochemical transformations selectively.
Detailed Mechanism of Phenol‐Inhibited Peroxidase‐Catalyzed Oxidation of Indole‐3‐Acetic Acid at Neutral pH*
Authors: Krylov Sergey N. , Dunford H. Brian
Published: January 2008

The inhibition of horseradish peroxidase (HRP)‐cata‐lyzed oxidation of indole‐3‐acetic acid (IAA) by a phenol, caffeic acid (CA), was studied using both a kinetic approach and computer simulation. The presence of CA resulted in a lag period in IAA oxidation. The lag period increased slowly with increasing [CA] until a critical concentration, [CA]cr, was reached, then it increased much faster when [CA] was greater than [CA]cr. The [CA]cr was proportional to [IAA] and did not depend upon [HRP]. Caffeic acid was oxidized by compound I and compound II of HRP with bimolecular rate constants (6.8 ± 107 and 2.1 ± 107M‐1s−l), which were much higher than the corresponding rate constants for IAA oxidation (2.3 ± 103 and 2.0 ± 102M−1s−1). Our experimental data show that CA inhibits IAA oxidation because it is able to compete effectively as a peroxidase substrate. A model based on a detailed mechanism of IAA oxidation was investigated using computer simulation. A rate constant driving nonenzymatic hydroperoxide formation in IAA solution was determined, 3.0 × 10−‐7 s−1. The model quantitatively describes the experimental results of this work and also qualitatively explains data published earlier. The critical inhibitor concentration is approximately equal to twice the concentration of hydroperoxide in IAA solution at the time of inhibitor addition. Therefore hydroperoxide Concentration can be calculated from the determination of critical inhibitor concentration.
Chemiluminescence Triggered by Hydrolase Activity in a Horseradish Peroxidase/H2O2‐Coupled Assay*
Authors: Campa Ana , Andrade Andrea de Castro , Catalani Luiz Henrique
Published: January 2008

2‐Methyl‐1‐propenyl acetate (MPA) was hydrolyzed by wheat lipase, pancreatic lipase, hydrolases and lipopro‐tein lipase from serum in a reaction that produces 2‐methyl‐1‐propenol. The latter was subsequently oxidized by horseradish peroxidase (HRP)/H2O2/O2 yielding triplet acetone that emits visible light. The integrated light emission was proportional to the units of lipase or volume of serum present. When pancreatic lipase was assayed, light emission was observed in the presence of bile salt as surfactant and chlorophyll a as light sensitizer. The potential application of this reaction in determinations of hydrolase/Iipase activities is discussed.
Development of Monoclonal Antibodies Against a Riboflavin‐Tryptophan Photoinduced Adduct: Reactivity to Eye Lens Proteins*
Authors: Diaz Marisol , Becker M. Ines , De Ioannes Alfredo E. , Silva Eduardo
Published: January 2008

We describe here the development of monoclonal antibodies to the hapten tryptophan‐riboflavin, generated by irradiation of a solution of bovine serum albumin in the presence of riboflavin. The specificity of the three obtained monoclonal antibodies, named lE6, 5H5, 5AS all belonging to the IgGl isotype, was assessed by a competitive enzyme‐linked immunosorbent assay in the presence of an increasing concentration of the tryptophan‐riboflavin adduct, obtained from an irradiated riboflavin‐sensitized tryptophan solution. It was demonstrated that the tryptophan‐riboflavin antibodies react with the soluble proteins of the eye lens; this reaction was more intense in the old rat lenses as compared to the young ones, and a maximum binding of the antibodies was obtained with the soluble protein fraction from the human catar‐actous lens. By indirect immunofluorescence, a reactivity associated with the protein matrix, localized in the lens central zone, was observed. In the peripheral zone of the lens, where the younger cells are found, a marked im‐munofluorescent emission was observed on structures preferentially localized in the nuclei.
Photochemistry and Photobiology of Furocoumarin Hydroperoxides Derived from Imperatorin: Novel Intercalating Photo‐Fenton Reagents for Oxidative DNA Modification by Hydroxyl Radicals*
Authors: Adam Waldemar , Berger Maurice , Cadet Jean , Dall'Acqua Francesco , Epe Bernd , Frank Silvia , Rarnaiah Danaboyina , Raoul Sebastian , Saha‐Möller Chantu R. , Vedaldi Daniela
Published: January 2008

Photochemical and photobiological properties of the im‐peratorin‐derived furocoumarin hydroperoxides la, la', 2a and 2a’have been investigated. Irradiation (350 nm) of the hydroperoxide 2a’afforded the alcohol 2b (2%), a diastereomeric mixture of the hydroxy epoxide 2c (40%; diastereomeric ratio = 80:20) and the epoxide 2d (8%). The formation of these products was rationalized in terms of homolysis of the hydroperoxide bond initiated by intramolecular energy transfer from the photoexcited furocoumarin chromophore. The quantum yields for the photolytic decomposition of hydroperoxides were estimated to be in the range of 0.03–0.85 and decreased in the order 2a ≫ 2a′≫ 1a′≥ 1a. The involvement of hydroxyl radicals in these reactions was established by trapping experiments with benzene and spectroscopic evidence was obtained by EPR spin trapping with 5,5‐di‐methylpyrroline‐N‐oxide. Fluorescence titration, DNA melting and linear dichroism studies of furocoumarins indicated that these compounds undergo efficient com‐plexation and also intercalation into the DNA. The binding parameters K (intrinsic binding constant) and l/n (frequency of binding sites) of complexes between furocoumarin derivatives and DNA were determined to be in the range of 3900–23 900 M‐l and 0.017–0.045. The pho‐toreaction of la’and lb’with 2′‐deoxyguanosine (dGuo) afforded exclusively 7,8‐dihydro‐8‐oxo‐2′‐deoxy‐guanosine (8‐oxodGuo), presumably through singlet oxygen, which was formed in a type II photooxidation process. In contrast, the hydroperoxide 2a oxidized dGuo to oxazo‐lone as major and 8‐oxodGuo as minor products through hydroxyl radicals, which were generated from 2a under photolytic conditions. Interestingly, the photoreactions of furocoumarins with salmon testes DNA showed that the highly reactive (φ= 0.85) hydroperoxide 2a is also most efficient in inducing the mutagenic DNA oxidation product 8‐oxodGuo. Hence, the novel furocoumarin hydroperoxide 2a constitutes the first intercalating photo‐Fen‐ton reagent and serves as convenient hydroxyl radical source for genotoxicity studies.
Pyrene Fluorescence in the Presence of Acrylic Acid‐Ethyl Methacrylate Copolymers: Effect of the Copolymer Composition in the Formation of Microdomains*
Authors: de Oliveira Vera A. , Tiera Marcio J. , Gehlen Marcelo H. , Neumann Miguel G.
Published: January 2008

The properties of aqueous solutions of acrylic acid‐ethyl methacrylate (EMA) copolymers have been investigated using pyrene and pyrene pyrenebutyltrimethylammonium (PBTA) as probes. Static and dynamic fluorescence have been used to obtain information about the microenviron‐ments formed. Micropolarity studies using the I1/I3 ratio of the vibronic bands of pyrene show the formation of hydrophobic domains. At low pH the increase of the amount of ethyl methacrylate in the copolymers shows that aqueous microdomains are excluded from the core of the polymer, for the copolymers with high content of EMA low polarity microdomains are still present on the mac‐romolecular chain even at higher pH. The pH‐induced conformational transition indicates that the more hydro‐phobic copolymers adopt a more tightly coiled conformation. Compared to PAA, the decay times for both probes are increased twice for the polymer with 25% molar proportion of EMA. The fluorescence quenching of the probes by nitromethane depends on pH, copolymer composition and probe structure. The efficiency of quenching decreases with increase of the EMA proportion in the copolymers. Pyrene is more efficiently quenched than PBTA as a consequence of the latter being located in more internal (less accessible) sites of the polymer structure.
Photophysical and Aggregation Studies of t‐Butyl‐Substituted Zn Phthalocyanines
Authors: Fernández Daniel A. , Awruch Josefina , Dicelio Lelia E.
Published: January 2008

Three potential photosensitizers for photodynamic therapy: tetra‐t‐butyl phthalocyaninato Zn(II), tetrakis‐(1,1‐dimethyl‐2‐phthalimido)ethylphthalocyaninato Zn(II), and tetrakis‐(1,1‐dimethyl‐2‐amino)ethylphthalocyaninato Zn(II), have been studied in homogeneous organic media. Dimerization constants and monomer and dimer spectra have been determined. Fluorescence, triplet and singlet oxygen quantum yìelds were measured and the photo‐physical characterization of the triplet state was performed for the three dyes. These parameters were evaluated in connection with aggregation results.
Synthesis, Photoreactivity and Cytotoxic Activity of Caged Compounds of L‐Leucyl‐L‐Leucine Methyl Ester, an Apoptosis Inducer
Authors: Odaka Mitsuyo , Furuta Toshiaki , Kobayashi Yoshiro , Iwamura Michiko
Published: January 2008

I,‐Leucyl‐L‐leucine methyl ester (Leu‐Leu‐OMe), an apoptosis inducer in natural killer cells and macro‐phages, was caged with trans‐o‐hydroxycinnamoyl (3ad), trans‐o‐mercaptocinnamoyl (4) and o‐nitrobenzyl derivatives (5a, b), and the photochemical reactivity of these derivatives in phosphate‐buffered saline containing 1% dimethyl sulfoxide and their immunological properties were studied. All of the derivatives exhibited absorplion at wavelengths longer than the UVB region. Although 3a–d and 4 were expected to isomerize to a cis isomer, which thgn cyclizes intramolecularly to give Leu‐Leu‐OMe and a coumarin derivative, cyclization efficiency was not satisfactory except for 3a. However, 3a itself caused necrosis (cell swelling) of U937 cells (a myeloid cell line). In contrast, 5a and b released Leu‐Leu‐OMe quickly and efficiently and did not affect U937 cells. Although irradiated 5b induced necrosis, irradiated 3a and 5a induced apoptosis in these cells, as evidenced by a decrease in cell size.
Measurement of UVA Exposure to Solar Radiation
Authors: Wong J. C. F. , Parisi A. V.
Published: January 2008

Exposure to solar UVA (320–400 nm) radiation can damage DNA and lead to skin disorders. Conventional dosim‐etry using a single piece of polysulfone or diglycol carbonate (CR‐39) cannot provide accurate measurement of the biologically effective irradiance for erythema for the UVA waveband. A package employing four dosimeters (polysulfone, nalidixic acid, 8‐methoxypsoralen and phe‐nothiazine) has been shown to be effective for use as a spectrum evaluator for evaluating the UVA source spectrum. In Brisbane, on a horizontal position, the spectrum evaluator requires about 5 min exposure in summer and about 20 min in winter. This amounts to about 10 mJ cm‐2 of erythemal UV radiation.
Structural and Functional Changes in Catalase Induced by Near‐UV Radiation
Authors: Zigman Seymour , Reddan John , Schultz Joanne B. , McDaniel Thurma
Published: January 2008

Part one of this study shows that exposure of purified beef liver catalase in buffered solutions to BL lamps that provide a mixture of 99% UVA and 1% UVB (to be labeled UVA) alters its chemistry and enzymatic activity. Thus, its spectral absorbance lost detail, it aggregated and exhibited a lower isoelectric point and its enzymatic activity was substantially reduced.

These photochemically induced changes were increased by irradiation in phosphate buffer or in physiological medium (minimal essential medium) containing riboflavin and tryptophan. Neither α‐tocopherol nor de‐feroxamine were protective against these UVA‐induced changes in pure catalase.

We further investigated the effect of UVA radiation on the activity of catalase in cultured lens epithelial cells and the protective effects of antioxidants. Cultured lens epithelial cells of rabbits and squirrels were exposed to near‐UV radiation with representation in the UVA region of 99% and 1% UVB. Catalase assays were done on ho‐mogenate supernatants of cells kept dark or UV exposed. In some instances, cells were cultured in medium containing a‐tocopherol or deferoxamine prior to UV radiation. Comparisons were made between UV‐exposed lens cell catalase activity when exposure was done with or without the antioxidants. The UVA radiation was strongly inhibitory to both rabbit and squirrel lens epithelial cell catalase activities. The range of fluxes of near UV radiation was compatible with that which could reach the lens from the sunlit environment. Catalase inactivation was lessened in cells preincubated with a‐tocopherol and deferoxamine. This suggests that both singlet oxygen and hydroxyl radical formation may be involved in near‐UV damage to lens epithelial cell catalase. Such inhibition of catalase by near‐UV would enhance H2O2 toxicity and stimulate SH oxidation so as to damage the lens.
Preprogrammed and Programmed Cell Death Mechanisms of Apoptosis: UV‐Induced Immediate and Delayed Apoptosis
Authors: Godar Dianne E.
Published: January 2008

Equitoxic doses (10% clonogenic survival) of UV radiation (UVR) from the three waveband regions, i.e. UVAl (340–400 nm), UVB (290–320 nm) and UVC (200–290 nm), were shown to induce immediate or delayed apoptosis in L5178Y‐R murine lymphoma cells. Membrane and DNA damage were shown to be the most probable initiators of UVAl‐induced immediate or UVR‐induced delayed apoptosis, respectively. These UV‐induced apop‐totic processes appeared to utilize two different “core” biochemical mechanisms; however, one core mechanism could be initiated at two distinct sites (e.g. membrane or DNA) and result in disparate kinetics. In an attempt to resolve this mechanistic issue, the dependence on mac‐romolecular synthesis of each UV‐induced apoptotic mechanism was investigated. In the absence of UVR, inhibition of either transcription (actinomycin D) or translation (cycloheximide) induced apoptosis in a concentration‐ and time‐dependent manner. These results suggest that an apoptotic mechanism exists that does not require macromolecular synthesis postinsult (constitutive). The UVR data demonstrate that UVAl‐induced immediate apoptosis utilizes this constitutive mechanism (preprogrammed), while UVR‐induced delayed apoptosis utilizes the well‐known inducible mechanism (programmed). Therefore, there are two different core biochemical mechanisms of apoptotic death available to each cell: preprogrammed (constitutive) and programmed (inducible) cell death.
Characterization of the Photosynthetic Activity of Platinized Chloroplasts: A Study Using Fluorescence and Photoacoustic Techniques
Authors: Supponeva Elena , Hotchandani Surat , Carpentier Robert
Published: January 2008

In this report, the effect of platinization on the photosynthetic activity of the chloroplast membranes is studied. Oxygen evolution, fluorescence emission and thermal de‐activation processes are modified after platinization. It is shown that photosystem II activity is affected by the hydrogen purging involved in the platinization procedure as seen by the reduced rates of oxygen evolution and a decrease in variable fluorescence. Depletion of bicarbonate from photosystem II during purging is suggested to be responsible partly for the decreased electron transfer rates and for a lower half‐saturation light intensity required for energy storage as measured by photoacoustic spectroscopy. On the other hand, the electron sink created by the reduction of hydrogen at the acceptor side of photosystem I is shown to reoxidize efficiently the plas‐toquinone pool of photosystem II.
Assembly of Photosystem I and II during the Early Phases of Light‐Induced Development of Chloroplasts from Proplastids in Spirodela oligorrhiza
Authors: McCormac Dennis J. , Marwood Christopher A. , Bruce Doug , Greenberg Bruce M.
Published: January 2008

The aquatic higher plant Spirodela oligorrhiza, which contains proplastids when grown in the dark, was used to study light‐dependent chloroplast development. Low‐temperature (77 K) and room temperature fluorescence were utilized in situ on whole plants to examine plastid development. The dark‐grown plants contain two 77 K fluorescence peaks, at 633 nm (F633) and at 657 nm (F657), with F633 dominating. The F657 species represents protochlorophyllide that is bound to protochloro‐phyllide oxidoreductase. It was rapidly phototrans‐formed to chlorophyllide (within 5 s) via a monomolec‐ular reaction. Free protochlorophyllide (F633) was converted to chlorophyllide during a 3 h exposure to light. Photosystem (PS) assembly in Spirodela could be detected 2 h after the plants were first exposed to light, with the PSII reaction center (77 K fluorescence at 684 nm) appearing slightly before the PSI reaction center (77 K fluorescence at 725 nm). After the first reaction centers were formed the antenna complexes were added; the light‐harvesting complex (LHC) I of PSI appeared after 8 h, and 47 kDa chlorophyll protein of PSII appeared between 12 h and 24 h. After 30 h of exposure to light, the plants acquired the ability to perform a light state transition, marking the appearance of functional LHCII complexes in the developing chloroplast. Finally, it was found that photosynthetic activity, as measured by room temperature chlorophyll fluorescence, accelerated con‐comitantly with detection of the antenna complexes. Therefore, although reaction centers are detected very early during the proplastid to chloroplast conversion, they may have little activity or be unstable until the antennae are present.
Lutetium Texaphyrin (PCI‐0123): A Near‐Infrared, Water‐Soluble Photosensitizer
Authors: Young S. W. , Woodburn K. W. , Wright M. , Mody T. D. , Fan Q. , Sessler J. L. , DOW W. C. , Miller R. A.
Published: January 2008

Lutetium texaphyrin, PCI‐0123, is a pure, water‐soluble photosensitizer with a large broad absorption band centered at 732 nm. The compound was tested for photodynamic therapy (PDT) effectiveness in a murine mammary cancer model. The texaphyrin macrocycle as illustrated by magnetic resonance imaging and 14C‐radiolabeled texaphyrin studies was shown to be tumor selective; a tumor‐to‐muscle ratio of 10.55 was seen after 5 h. Lutetium texaphyrin, at a drug dose of 20 μmol/kg with irradiation 5 h postinjection at 150 J/cm2 and 150 mW/cm2, had significant efficacy (P < 0.0001) in treating neoplasms of moderate size (40 ± 14 mm3) and also had significant efficacy (P < 0.0001) in treating larger neoplasms (147 ± 65 mm3). The PDT efficacy was correlated with the time interval between PCI‐0123 administration and light exposure. A 100% cure rate was achieved when photoirradiation took place 3 h postinjection compared to 50% for 5 h using 10 μmol/kg and 150 J/cm2 at 150 mW/cm2. The PDT efficacy was attributable to the selective uptakehetention of the texaphyrin photosensitizer in addition to the depth of light penetration achievable at the 732 nm laser irradiation.