bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rhamnogalacturonan α-d-Galactopyranosyluronohydrolase1
Authors: Mutter Margien , Beldman Gerrit , Pitson Stuart M. , Schols Henk A. , Voragen Alphons G.J. 
Published: July 2002

Abstract
A new enzyme, rhamnogalacturonan (RG) α-d-galactopyranosyluronohydrolase (RG-galacturonohydrolase), able to release a galacturonic acid residue from the nonreducing end of RG chains but not from homogalacturonan, was purified from an Aspergillus aculeatus enzyme preparation. RG-galacturonohydrolase acted with inversion of anomeric configuration, initially releasing β-d-galactopyranosyluronic acid. The enzyme cleaved smaller RG substrates with the highest catalytic efficiency. A Michaelis constant of 85 μm and a maximum reaction rate of 160 units mg−1 was found toward a linear RG fragment with a degree of polymerization of 6. RG-galacturonohydrolase had a molecular mass of 66 kD, an isoelectric point of 5.12, a pH optimum of 4.0, and a temperature optimum of 50°C. The enzyme was most stable between pH 3.0 and 6.0 (for 24 h at 40°C) and up to 60°C (for 3 h).
The Kinetics of Zeaxanthin Formation Is Retarded by Dicyclohexylcarbodiimide1
Authors: Heyde Sandra , Jahns Peter 
Published: July 2002

AbstractThe de-epoxidation of violaxanthin to antheraxanthin (Anth) and zeaxanthin (Zeax) in the xanthophyll cycle of higher plants and the generation of nonphotochemical fluorescence quenching in the antenna of photosystem II (PSII) are induced by acidification of the thylakoid lumen. Dicyclohexylcarbodiimide (DCCD) has been shown (a) to bind to lumen-exposed carboxy groups of antenna proteins and (b) to inhibit the pH-dependent fluorescence quenching. The possible influence of DCCD on the de-epoxidation reactions has been investigated in isolated pea (Pisum sativum L.) thylakoids. The Zeax formation was found to be slowed down in the presence of DCCD. The second step (Anth → Zeax) of the reaction sequence seemed to be more affected than the violaxanthin → Anth conversion. Comparative studies with antenna-depleted thylakoids from plants grown under intermittent light and with unstacked thylakoids were in agreement with the assumption that binding of DCCD to antenna proteins is probably responsible for the retarded kinetics. Analyses of the DCCD-induced alterations in different antenna subcomplexes showed that Zeax formation in the PSII antenna proteins was predominantly influenced by DCCD, whereas Zeax formation in photosystem I was nearly unaffected. Our data support the suggestion that DCCD binding to PSII antenna proteins is responsible for the observed alterations in xanthophyll conversion.
Eucalypt NADP-Dependent Isocitrate Dehydrogenase1
Authors: Boiffin Vincent , Hodges Michael , Gálvez Susana , Balestrini Raffaella , Bonfante Paola , Gadal Pierre , Martin Francis 
Published: July 2002

AbstractNADP-dependent isocitrate dehydrogenase (NADP-ICDH) activity is increased in roots ofEucalyptus globulus subsp. bicostata ex Maiden Kirkp. during colonization by the ectomycorrhizal fungusPisolithus tinctorius Coker and Couch. To investigate the regulation of the enzyme expression, a cDNA (EgIcdh) encoding the NADP-ICDH was isolated from a cDNA library of E. globulus-P. tinctorius ectomycorrhizae. The putative polypeptide sequence of EgIcdh showed a high amino acid similarity with plant NADP-ICDHs. Because the deduced EgICDH protein lacks an amino-terminal targeting sequence and shows highest similarity to plant cytosolic ICDHs, it probably represents a cytoplasmic isoform. RNA analysis showed that the steady-state level ofEgIcdh transcripts was enhanced nearly 2-fold in ectomycorrhizal roots compared with nonmycorrhizal roots. Increased accumulation of NADP-ICDH transcripts occurred as early as 2 d after contact and likely led to the observed increased enzyme activity. Indirect immunofluorescence microscopy indicated that NADP-ICDH was preferentially accumulated in the epidermis and stele parenchyma of nonmycorrhizal and ectomycorrhizal lateral roots. The putative role of cytosolic NADP-ICDH in ectomycorrhizae is discussed.
Calmodulin Activation of an Endoplasmic Reticulum-Located Calcium Pump Involves an Interaction with the N-Terminal Autoinhibitory Domain
Authors: Hwang Ildoo , Harper Jeffrey F. , Liang Feng , Sze Heven 
Published: July 2002

Abstract
To investigate how calmodulin regulates a unique subfamily of Ca2+ pumps found in plants, we examined the kinetic properties of isoform ACA2 identified in Arabidopsis. A recombinant ACA2 was expressed in a yeast K616 mutant deficient in two endogenous Ca2+ pumps. Orthovanadate-sensitive45Ca2+ transport into vesicles isolated from transformants demonstrated that ACA2 is a Ca2+ pump. Ca2+ pumping by the full-length protein (ACA2-1) was 4- to 10-fold lower than that of the N-terminal truncated ACA2-2 (Δ2–80), indicating that the N-terminal domain normally acts to inhibit the pump. An inhibitory sequence (IC50 = 4 μm) was localized to a region within valine-20 to leucine-44, because a peptide corresponding to this sequence lowered the V max and increased theK m for Ca2+ of the constitutively active ACA2-2 to values comparable to the full-length pump. The peptide also blocked the activity (IC50 = 7 μm) of a Ca2+ pump (AtECA1) belonging to a second family of Ca2+ pumps. This inhibitory sequence appears to overlap with a calmodulin-binding site in ACA2, previously mapped between asparatate-19 and arginine-36 (J.F. Harper, B. Hong, I. Hwang, H.Q. Guo, R. Stoddard, J.F. Huang, M.G. Palmgren, H. Sze [1998] J Biol Chem 273: 1099–1106). These results support a model in which the pump is kept “unactivated” by an intramolecular interaction between an autoinhibitory sequence located between residues 20 and 44 and a site in the Ca2+ pump core that is highly conserved between different Ca2+ pump families. Results further support a model in which activation occurs as a result of Ca2+-induced binding of calmodulin to a site overlapping or immediately adjacent to the autoinhibitory sequence.
Overexpression of the ArabidopsisCBF3Transcriptional Activator Mimics Multiple Biochemical Changes Associated with Cold Acclimation
Authors: Gilmour Sarah J. , Sebolt Audrey M. , Salazar Maite P. , Everard John D. , Thomashow Michael F. 
Published: July 2002

AbstractWe further investigated the role of the ArabidopsisCBF regulatory genes in cold acclimation, the process whereby certain plants increase in freezing tolerance upon exposure to low temperature. The CBF genes, which are rapidly induced in response to low temperature, encode transcriptional activators that control the expression of genes containing the C-repeat/dehydration responsive element DNA regulatory element in their promoters. Constitutive expression of either CBF1 orCBF3 (also known as DREB1b andDREB1a, respectively) in transgenic Arabidopsis plants has been shown to induce the expression of target COR(cold-regulated) genes and to enhance freezing tolerance in nonacclimated plants. Here we demonstrate that overexpression ofCBF3 in Arabidopsis also increases the freezing tolerance of cold-acclimated plants. Moreover, we show that it results in multiple biochemical changes associated with cold acclimation:CBF3-expressing plants had elevated levels of proline (Pro) and total soluble sugars, including sucrose, raffinose, glucose, and fructose. Plants overexpressing CBF3 also had elevated P5CS transcript levels suggesting that the increase in Pro levels resulted, at least in part, from increased expression of the key Pro biosynthetic enzyme Δ1-pyrroline-5-carboxylate synthase. These results lead us to propose that CBF3 integrates the activation of multiple components of the cold acclimation response.
Entropy—enthalpy compensation: Fact or artifact?
Authors: Sharp Kim 
Published: July 2002

AbstractThe phenomenon of entropy–enthalpy (S‐H) compensation is widely invoked as an explanatory principle in thermodynamic analyses of proteins, ligands, and nucleic acids. It has been suggested that this compensation is an intrinsic property of either complex, fluctuating, or aqueous systems. The questions examined here are whether the observed compensation is extra‐thermodynamic (i.e., reflects anything more than the well‐known laws of statistical thermodynamics) and if so, what does it reveal about the system? Compensation is rather variably defined in the literature and different usages are discussed. The most precise and interesting one, which is considered here, is a linear relationship between ΔH and ΔS for some series of perturbations or changes in experimental variable. Some recent thermodynamic data on proteins purporting to show compensation is analyzed and shown to be better explained by other causes. A general statistical mechanical model of a complex system is analyzed to explore whether and under what conditions extra‐thermodynamic compensation can occur and what it reveals about the system. This model shows that the most likely behavior to be seen is linear S‐H compensation over a rather limited range of perturbations with a compensation temperature Tc = dΔH/dΔS within 20% of the experimental temperature. This behavior is insensitive to the details of the model, thus revealing little extra‐thermodynamic or causal information about the system. In addition, it will likely be difficult to distinguish this from more trivial forms of compensation in real experimental systems.
Triple Cycle: A Conceptual Arrangement of Multiple Cycle Toward
Optimal Energy Conversion
Authors: Hung T. C. 
Published: July 2002

Abstract
The purpose of this study is to find a maximum work output from various combinations of thermodynamic cycles from a viewpoint of the cycle systems. Three systems were discussed in this study: a fundamental combined cycle and two other cycles evolved from the fundamental dual combined cycle: series-type and parallel-type triple cycles. In each system, parametric studies were carried out in order to find optimal configurations of the cycle combinations based on the influences of tested parameters on the systems. The study shows that the series-type triple cycle exhibits no significant difference as compared with the combined cycle. On the other hand, the efficiency of the parallel-type triple cycle can be raised, especially in the application of recovering low-enthalpy-content waste heat. Therefore, by properly combining with a steam Rankine cycle, the organic Rankine cycle is expected to efficiently utilize residual yet available energy to an optimal extent. The present study has pointed out a conceptual design in multiple-cycle energy conversion systems.
Determination of Thermal Accommodation of Translational Energy of Vapors at a Glass Surface
Authors: Morrison J. A. , Tuzi Y. 
Published: July 2002

A new method has been developed for the determination of translational thermal accommodation coefficients, αt, of vapors interacting with solid surfaces and has been used to measure αt for bromine, iodine, benzene, naphthalene, n-hexane, and ethylacetate on Pyrex glass in the temperature region 195 ° to 465 °K. The values obtained (0.55, 0.64, 0.37, 0.37, 0.47, and 0.46, respectively) have a probable accuracy of ±0.06 or better and are only slightly temperature-dependent.
The method, which can be easily adapted for the study of interactions with surfaces other than glass, requires the measurement of the mean velocity of molecules leaving the solid surface. This is accomplished by passing a selected beam of the molecules through the sensitive volume of an ion gauge. The only restriction on the method is that the pressure of the vapor at the temperature of the wall of the gauge should be very low (e.g., 10−12 Torr).
Nutrient Biogeochemistry of the Coastal Zone
Authors: Jickells T. D. 
Published: July 2002

REVIEW
The coastal seas are one of the most valuable and vulnerable of Earth's habitats. Significant inputs of nutrients to the coastal zone arrive via rivers, groundwater, and the atmosphere. Nutrient fluxes through these routes have been increased by human activity. In addition, the N:P:Si ratios of these inputs have been perturbed, and many coastal management practices exacerbate these perturbations. There is evidence of impacts arising from these changes (in phytoplankton numbers and relative species abundance, and deep-water oxygen declines) in areas of restricted water exchange. Elsewhere, the nutrient fluxes through the coastal zone appear to be still dominated by large inputs from the open ocean, and there is little evidence of anthropogenic perturbations.
Interactions of Bacterial Cationic Peptide Antibiotics with Outer and Cytoplasmic Membranes of
Pseudomonas aeruginosa
Authors: Zhang Lijuan , Dhillon Pawandeep , Yan Hong , Farmer Susan , Hancock Robert E. W. 
Published: July 2002

ABSTRACT

Polymyxins B and E1 and gramicidin S are bacterium-derived cationic antimicrobial peptides. The polymyxins were more potent than gramicidin S against
Pseudomonas aeruginosa
, with MICs of 0.125 to 0.25 and 8 μg/ml, respectively. These peptides differed in their affinities for binding to lipopolysaccharide, but all were able to permeabilize the outer membrane of wild-type
P. aeruginosa
PAO1 strain H103, suggesting differences in their mechanisms of self-promoted uptake. Gramicidin S caused rapid depolarization of the bacterial cytoplasmic membrane at concentrations at which no killing was observed within 30 min, whereas, conversely, the concentrations of the polymyxins that resulted in rapid killing resulted in minimal depolarization. These data indicate that the depolarization of the cytoplasmic membrane by these peptides did not correlate with bacterial cell lethality.
In Vitro Activities of DU-1102, a New Trioxaquine Derivative, againstPlasmodium falciparumIsolates
Authors: Basco Leonardo K. , Dechy-Cabaret Odile , Ndounga Mathieu , Meche Fleurette Solange , Robert Anne , Meunier Bernard 
Published: July 2002

ABSTRACTThe antimalarial trioxaquine derivative DU-1102, synthesized by covalent linkage between aminoquinoline and trioxane moieties, was highly active against Cameroonian isolates (mean 50% inhibitory concentration of 43 nmol/liter) ofPlasmodium falciparum. There was no correlation between the responses to DU-1102 and chloroquine and only a low correlation between the responses to DU-1102 and pyrimethamine, suggesting an independent mode of action of the trioxaquine against the parasites.
Antibacterial Properties of Dermaseptin S4 Derivatives with In Vivo Activity
Authors: Navon-Venezia Shiri , Feder Rina , Gaidukov Leonid , Carmeli Yehuda , Mor Amram 
Published: July 2002

ABSTRACT

Derivatives of the cytotoxic peptide dermaseptin S4 have recently emerged as potential antimicrobial agents. Here, we report on the antibacterial properties of three derivatives with improved toxicity profiles: a 28-residues K
4
K
20
-S4 and two shorter versions, K
4
-S4(1-16) and K
4
-S4(1-13). The range of MICs of K
4
K
20
-S4 against clinical isolates of
Staphylococcus aureus
,
Pseudomonas aeruginosa,
and
Escherichia coli
were, respectively, 1 to 4, 1 to 4, and 1 to 16 μg/ml. MICs of the short derivatives were rather similar or two to fourfold higher. Each of the three peptides was rapidly bactericidal in vitro, reducing the number of viable CFU of either
E. coli
or
S. aureus
by 6 log units in 30 min or less. Compared with MSI-78 or PG-1, K
4
-S4(1-13) was at least as potent against bacteria (assessed at two MIC multiples) but displayed lesser toxicity against human erythrocytes. Serial passage in subinhibitory concentrations led to emergence of resistance to commercial antibiotics but not to the
l
- or
d
isomer of either of the dermaseptin derivatives. The short derivatives were further investigated for antibacterial activity in vivo, using a peritonitis model of mice infected with
P. aeruginosa
. Naive mice in the vehicle control group exhibited 75% mortality, compared to 18 or 36% mortality in mice that received a single intraperitoneal injection (4.5 mg/kg) of K
4
-S4(1-16) or K
4
-S4(1-13), respectively. In vivo bactericidal activity was confirmed in neutropenic mice, where intraperitoneal administration of K
4
-S4(1-16) reduced the number of viable CFU in a dose-dependent manner by >3 log units within 1 h of exposure, and this was sustained for at least 5 h. Overall, the data suggest that dermaseptin S4 derivatives could be useful in treatment of infections, including infections caused by multidrug-resistant bacteria.
Antimicrobial Peptides Protect Coho Salmon from
Vibrio anguillarum
Infections
Authors: Jia X. , Patrzykat A. , Devlin R. H. , Ackerman P. A. , Iwama G. K. , Hancock R. E. W. 
Published: July 2002

ABSTRACT

Fish losses from infectious diseases are a significant problem in aquaculture worldwide. Therefore, we investigated the ability of cationic antimicrobial peptides to protect against infection caused by the fish pathogen
Vibrio anguillarum
. To identify effective peptides for fish, the MICs of certain antimicrobial peptides against fish pathogens were determined in vitro. Two of the most effective antimicrobial peptides, CEME, a cecropin-melittin hybrid peptide, and pleurocidin amide, a C-terminally amidated form of the natural flounder peptide, were selected for in vivo studies. A single intraperitoneal injection of CEME did not affect mortality rates in juvenile coho salmon infected with
V. anguillarum
, the causative agent of vibriosis. Therefore, the peptides were delivered continuously using miniosmotic pumps placed in the peritoneal cavity. Twelve days after pump implantation, the fish received intraperitoneal injections of
V. anguillarum
at a dose that would kill 50 to 90% of the population. Fish receiving 200 μg of CEME per day survived longer and had significantly lower accumulated mortalities (13%) than the control groups (50 to 58%). Fish receiving pleurocidin amide at 250 μg per day also survived longer and had significantly lower accumulated mortalities (5%) than the control groups (67 to 75%). This clearly shows the potential for antimicrobial peptides to protect fish against infections and indicates that the strategy of overexpressing the peptides in transgenic fish may provide a method of decreasing bacterial disease problems.
Detection and Identification of
Leishmania
DNA within Naturally Infected Sand Flies by Seminested PCR on Minicircle Kinetoplastic DNA
Authors: Aransay Ana M. , Scoulica Efstathia , Tselentis Yannis 
Published: July 2002

ABSTRACT

A seminested PCR assay was developed in order to amplify the kinetoplast minicircle of
Leishmania
species from individual sand flies. The kinetoplast minicircle is an ideal target because it is present in 10,000 copies per cell and its sequence is known for most
Leishmania
species. The two-step PCR is carried out in a single tube using three primers, which were designed within the conserved area of the minicircle and contain conserved sequence blocks. The assay was able to detect as few as 3 parasites per individual sand fly and to amplify minicircle DNA from at least eight
Leishmania
species. This technique permits the processing of a large number of samples synchronously, as required for epidemiological studies, in order to study infection rates in sand fly populations and to identify potential insect vectors. Comparison of the sequences obtained from sand flies and mammal hosts will be crucial for developing hypotheses about the transmission cycles of
Leishmania
spp. in areas of endemicity.
Anaerobic Conversion of Lactic Acid to Acetic Acid and 1,2-Propanediol by
Lactobacillus buchneri
Authors: Oude Elferink Stefanie J. W. H. , Krooneman Janneke , Gottschal Jan C. , Spoelstra Sierk F. , Faber Folkert , Driehuis Frank 
Published: July 2002

ABSTRACT

The degradation of lactic acid under anoxic conditions was studied in several strains of
Lactobacillus buchneri
and in close relatives such as
Lactobacillus parabuchneri
,
Lactobacillus kefir
, and
Lactobacillus hilgardii
. Of these lactobacilli,
L. buchneri
and
L. parabuchneri
were able to degrade lactic acid under anoxic conditions, without requiring an external electron acceptor. Each mole of lactic acid was converted into approximately 0.5 mol of acetic acid, 0.5 mol of 1,2-propanediol, and traces of ethanol. Based on stoichiometry studies and the high levels of NAD-linked 1,2-propanediol-dependent oxidoreductase (530 to 790 nmol min
−1
mg of protein
−1
), a novel pathway for anaerobic lactic acid degradation is proposed. The anaerobic degradation of lactic acid by
L. buchneri
does not support cell growth and is pH dependent. Acidic conditions are needed to induce the lactic-acid-degrading capacity of the cells and to maintain the lactic-acid-degrading activity. At a pH above 5.8 hardly any lactic acid degradation was observed. The exact function of anaerobic lactic acid degradation by
L. buchneri
is not certain, but some results indicate that it plays a role in maintaining cell viability.
Pigment and Virulence Deficiencies Associated with Mutations in the
aroE
Gene of
Xanthomonas oryzae
pv. oryzae
Authors: Goel Ajay Kumar , Rajagopal Lakshmi , Sonti R. V. 
Published: July 2002

ABSTRACT

Xanthomonadins are yellow, membrane-bound pigments produced by members of the genus
Xanthomonas
. We identified an ethyl methanesulfonate-induced
Xanthomonas oryzae
pv. oryzae mutant (BXO65) that is deficient for xanthomonadin production and virulence on rice, as well as auxotrophic for aromatic amino acids (Pig
−
Vir
−
Aro
−
). Reversion analysis indicated that these multiple phenotypes are due to a single mutation. A genomic library of the wild-type strain was used to isolate a 7.0-kb clone that complements BXO65. By transposon mutagenesis, marker exchange, sequence analysis, and subcloning, the complementing activity was localized to a 849-bp open reading frame (ORF). This ORF is homologous to the
aroE
gene, which encodes shikimate dehydrogenase in various bacterial species. Shikimate dehydrogenase activity was present in the wild-type strain and the mutant with the complementing clone, whereas no activity was found in BXO65. This clone also complemented an
Escherichia coli aroE
mutant for prototrophy, indicating that
aroE
is functionally conserved in
X. oryzae
pv. oryzae and
E. coli
. The nucleotide sequence of the 2.9-kb region containing
aroE
revealed that a putative DNA helicase gene is located adjacent to
aroE
. Our results indicate that
aroE
is required for normal levels of virulence and xanthomonadin production in
X. oryzae
pv. oryzae.