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1.
Johannes H. Ippel Virginia Lanzotti Aldo Galeone Luciano Mayol Jacquelien E. van den Boogaart Jeroen A. Pikkemaat Cornelis Altona 《Journal of biomolecular NMR》1995,6(4):403-422
Summary The circular DNA decamer 5-dpCGC-TT-GCG-TT-3 was studied in solution by means of NMR spectroscopy and molecular dynamics in H2O. At a temperature of 269 K, a 50/50 mixture of two dumbbell structures (denoted L2L2 and L2L4) is present. The L2L2 form contains three Watson-Crick C-G base pairs and two two-residue loops in opposite parts of the molecule. On raising the temperature from 269 K to 314 K, the L2L4 conformer becomes increasingly dominant (95% at 314 K). This conformer has a partially disrupted G(anti)-C(syn) closing base pair in the 5-GTTC-3 loop with only one remaining (solvent-accessible) hydrogen bond between NH of the cytosine dC(1) and O6 of the guanine dG(8). The opposite 5-CTTG-3 loop remains stable. The two conformers occur in slow equilibrium (rate constant 2–20 s–1). Structure determination of the L2L2 and L2L4 forms was performed with the aid of a full relaxation matrix approach (IRMA) in combination with restrained MD. Torsional information was obtained from coupling constants. Coupling constant analysis (3JHH, 3JHP, 3JCP) gave detailed information about the local geometry around backbone torsion angles , , and , revealing a relatively high flexibility of the 5-GTTC-3 loop. The values of the coupling constants are virtually temperature-independent. Weakly constrained molecular dynamics in solvent was used to sample the conformational space of the dumbbell. The relaxation matrices from the MD simulation were averaged over r–3 to predict dynamic NOE volumes. In order to account for the 1:1 conformational mixture of L2L2 and L2L4 present at 271 K, we also included S2 factors and r–6 averaging of the r–3-averaged relaxation matrices. On matrix averaging, the agreement of NOE volumes with experiment improved significantly for protons located in the thermodynamically less stable 5-GTTC-3 loop. The difference in stability of the 5-CTTG-3 and 5-GTTC-3 loops is mainly caused by differences in the number of potential hydrogen bonds in the minor groove and differences in stacking overlap of the base pairs closing the minihairpin loops. The syn conformation for dC(1), favored at high temperature, is stabilized by solvation in the major groove. However, the conformational properties of the dC(1) base, as deduced from R-factor analysis and MD simulations, include a large flexibility about torsion angle . 相似文献
2.
Summary Five different types of experiment are described which make it possible to measure various relaxation rates of selected protons in crowded spectra of macromolecules such as proteins: longitudinal spin-lattice relaxation rates =1/T1, transverse relaxation rates =1/T2 measured under conditions of free precession, transverse relaxation rates 1
LOCK=1/T1
measured under conditions of spin-locking, and transverse relaxation rates DQC=1/T2
DQC and ZQC=1/T2
ZQC of double- and zero-quantum coherences. The surprisingly large discrepancy between the transverse rates t and t is discussed in detail. To separate overlapping proton signals, the experimental schemes involve one or several magnetization transfer steps, using a doubly selective homonuclear Hartmann-Hahn method. Numerous variants of the basic ideas can be conceived, depending on the extent of signal overlap and on the topology of the networks of scalar couplings. Applications are shown to H and H of Tyr23, to H, H and H of Cys30, and to H and H of Ala24 in bovine pancreatic trypsin inhibitor (BPTI). 相似文献
3.
The limited proteolytic pattern of transducin,G
t
, and its purified subunits with chymotrypsin were analyzed and the cleavage sites on the
t
subunit were identified. The
t
subunit in the GTPS bound form was cleaved into a major 38 kD fragment, whereas
t
-GDP was progressively digested into 38, 23, 21, and 15 kD fragments. The
t
subunit was not very sensitive to proteolytic digestion with chymotrypsin. The
t
subunit was not cleaved and only a small portion of
t
was digested into several fragments. In order to determine which proteolytic fragment of
t
still contained the carboxyl terminal region, chymotrypsinization was carried out usingG
t
previously32P-labeled at Cys347 by petrussis toxin-catalyzed ADP-ribosylation. The32P-label was mainly associated with the
t
subunit and a 15 kD fragment. The 23 and 21 kD fragments were not32P-labeled. Analysis of amino terminal sequences of 38, 21, and 15 kD proteolytic bands allowed the identification of the major cleavage sites. Chymotrypsin had two cleavage sites in the amino terminal region of
t
, at Leu15 and Leu19. Chymotrypsin removed 15–19 amino acid residues from the amino terminus of
t
, generating two peptides (38 kD) which comigrates in gel electrophoresis. Chymotrypsin also cleaved at Trp207 in a conformation-dependent manner. Trp207 of
t
-GTPS was resistant to proteolysis but
t
-GDP and the 38 kD fragments of
t
-GDP produced the 23 and 21 kD fragments, respectively, and a 15 kD fragment containing the carboxyl terminus. This proves that the environment of Trp207 changes when GTP or GTPS is bound, leading to its inaccessibility to chymotrypsin. 相似文献
4.
E. Hagmüller H. -J. Günther H. D. Saeger H. Kolmar J. -P. Striebel Y. Ghoos 《Amino acids》1991,1(2):283-287
Summary Own investigations on in-vivo tumor metabolism of the malignant human colon tumor showed a significant uptake of branched chain amino acids by the tumor itself. To study the quantitative tumor protein metabolism (compartment tumor) the13C-leucine-tracer-technique was modified.Beside the common13C-leucine-breath-test we measured also the AV-differences of13C-leucine,13C-ketoisocaproate and13CO2. The Tumorblood flow was measured by venous-outflow-technique as well as the tumor mass.In this way it is possible to get quantitative results in substrate exchange of branched chain amino acids in malignant human colon tumors. 相似文献
5.
In this paper we use a dynamical systems approach to prove the existence of a unique critical value c
* of the speed c for which the degenerate density-dependent diffusion equation u
ct
= [D(u)u
x
]
x
+ g(u) has: 1. no travelling wave solutions for 0 < c < c
*, 2. a travelling wave solution u(x, t) = (x - c
*
t) of sharp type satisfying (– ) = 1, () = 0 *; '(*–) = – c
*/D'(0), '(*+) = 0 and 3. a continuum of travelling wave solutions of monotone decreasing front type for each c > c
*. These fronts satisfy the boundary conditions (– ) = 1, '(– ) = (+ ) = '(+ ) = 0. We illustrate our analytical results with some numerical solutions. 相似文献
6.
Rajkhowa R.C. Goswami Pranab Singh H.D. 《World journal of microbiology & biotechnology》2000,16(1):63-68
The mechanism of uptake of water-insoluble -sitosterol by a newly isolated strain of Arthrobacter
simplex SS-7 was studied. The production of an extracellular sterol-pseudosolubilizing protein during growth of A. simplex on -sitosterol was demonstrated by isolating the factor from the cell-free supernatant and its subsequent purification by Sephadex G-150 column chromatography. The M
r of the purified sterol-pseudosolubilizing protein determined by SDS–PAGE was 19kDa. The rate of sterol pseudosolubilization (5.2×10–3g l–1h–1) could not adequately account for the rate of sterol uptake (72×10–3g l–1h–1) and the specific growth rate (56×10–3 h–1). However in the unfavourable growth condition, when the cells were treated with sodium azide at the level of 30–60% of MIC, the sterol pseudosolubilization accounted for nearly 74% of the total growth containing 96% free cells. Cellular adherence to substrate particles was found to play an active role in the normal growth of the strain on -sitosterol. Unlike sodium acetate-grown cells, whose surface activity was negligible (60mNm–1), the sterol-grown cells had strong surface activity (40mNm–1). The high lipid content and long chain fatty acids in the cell-wall of -sitosterol-grown cells probably contribute to the high sterol adherence activity of the cells. 相似文献
7.
Qian Yong Jiang Binghua Flynn Daniel C. Leonard Stephen S. Wang Suiwei Zhang Zhuo Ye Jianping Chen Fei Wang Liying Shi Xianglin 《Molecular and cellular biochemistry》2001,222(1-2):199-204
While Cr (VI)containing compounds are well established carcinogens, the mechanisms of their action remain to be investigated. In this study we show that Cr (VI) causes increased tyrosine phosphorylation in human lung epithelial A549 cells in a timedependent manner. Nacetylcysteine (NAC), a general antioxidant, inhibited Cr (VI)induced tyrosine phosphorylation. Catalase, a scavenger of H2O2, sodium formate and aspirin, scavengers of hydroxyl radical (OH), also inhibited the increased tyrosine phosphorylation induced by Cr (VI). SOD, an inhibitor of superoxide radical (O2
–), caused less inhibition. ESR study shows that incubation of Cr (VI) with the A549 cells generates OH radical. The generation of radical was decreased by addition of catalase and sodium formate, while SOD did not have any inhibitory effect. Oxygen consumption measurements show that addition of f Cr (VI) to A549 cells resulted in enhanced molecular oxygen consumption. These results indicate that Cr (VI) can induce an increase in tyrosine phosphorylation. H2O2 and OH radicals generated during the process are responsible for the increased tyrosine phosphorylation induced by Cr (VI). 相似文献
8.
Josiane Szpirer et Philippe Brachet 《Molecular & general genetics : MGG》1970,108(1):78-92
Summary This work deals with the ability of phage 80 to provide defective mutants of with their missing functions.
Functions Involved in Recombination. As shown by others, the Int mechanism of 80 cannot excise prophage . However, 80 efficiently excises recombinants from tandem dilysogens, using its Ter mechanism. Likewise, the nonspecific mechanism Red is interchangeable between 80 and .
Maturation of DNA by 80. The Ter recombinants excised by 80 from tandem dilysogens are packaged into a 80 protein coat. This contrasts with the fact, already mentionned by Dove, that 80 is extremely inefficient for packaging phage superinfecting a -lysogen. The latter result is also found when the helper phage is a hybrid with the left arm of (80hy4 or 80hy41 — see Fig. 1). However, the maturation of the superinfecting is much more efficient if the 80hy used as a helper has the att-N region of (like 80hy1). Conversely a with the att-N region of 80 (hy6 — see Fig. 1) is packaged more efficiently by 80 or 80hy4 than by 80hy1. It is suggested that the maturation of chromosome superinfecting an immune cell requires a recombination with the helper phage.
Vegetative Functions. Among the replicative functoons O and P, the latter only can be supplied by 80. That N mutants are efficiently helped by 80 does not tell that 80 provides the defective with an active N product; the chromosomes are simply packaged into a 80 coat. This shows that 80 is unable to switch on the late genes of . That neither 80 nor any of the 80hy tested can provide an active N product is shown in a more direct way by their complete failure to help N
-r14; this phage carries a polar mutation which makes the expression of genes O and P entirely N-dependant. The maturation of a N
- by 80 contrasts with the fact that mutants affected in late genes (A, F or H) are not efficiently helped by 80. This suggests that the products coded by these genes are not interchangeable between 80 and , and that packaging of DNA into 80 coats is possible but inhibited when late proteins are present in the cell.
Activation of the Late Genes. Among the im
80
h
+
hybrids tested, only 80hy41 is able to switch on the late genes of a N defective mutant. This hybrid differs from the other hybrids studied here, by the fact that it has the Q-S-R region of (see Fig. 1). The results are consistant with the view that the product of Q gene is sufficient for activating the late genes of a DNA. N would thus control the expression of late genes only indirectly by controlling the expression of gene Q (Couturier & Dambly have independantly reached the same conclusion, 1970). Furthermore the failure of 80 and of the 80hy1 and 80hy4 to activate the late genes of would imply that these phages are unable to provide an Q product active on the chromosome Reciprocally, switches on the late genes of prophage 80hy41, but not of prophages 80hy1 and 80hy4. This suggests that the initiation of late genes expression takes place at a main specific site located in the Q-S-R region of the chromosome. The expression of the late genes would thus be sequential, and proceed through the left arm only when steaky ends cohere. Similar conclusions were reached independantly by Toussaint (1969) and by Herskowitz and Signer (1970).
Ce travail a été réalisé dans le cadre du contrat d'association Euratom-U. L. B. 007-61-10 ABIB et avec l'aide du Fonds de la Recherche Fondamentale Collective. 相似文献
Ce travail a été réalisé dans le cadre du contrat d'association Euratom-U. L. B. 007-61-10 ABIB et avec l'aide du Fonds de la Recherche Fondamentale Collective. 相似文献
9.
The physical origin and functional significance of the near infra-red light scattering changes observable upon flash illumination of diluted suspensions of magnetically oriented, permeabilised frog retinal rods has been reinvestigated with particular attention paid to the degree with which transducin remains attached to the membrane. In the absence of GTP, the so called binding signal is shown to include two components of distinctive origins, widely different kinetics, and whose relative amplitudes depend on the dilution of the suspension and resulting detachment of transducin from the disc membrane. The fast component is a consequence of the fast interaction between photoexcited rhodopsin (R*) and the transducin remaining on the membrane. Its kinetics monitors a structural modification of the discs caused by a change in electrostatic interaction between closely packed membranes upon the formation of R*-T complexes. The slow component monitors the slow rebinding to the membrane and possible subsequent interaction with excess R* of T-GDP which, in spite of its low solubility, had eluted into solution given the high dilution of the permeated rods. In the presence of GTP, the so called dissociation signal includes a fast, anisotropic release component that specifically monitors the release into the interdiscal space of T
-GTP formed from the membrane-bound pool, and a slower isotropic loss component monitoring the leakage from the permeated rod of the excess T
-GTP which did not interact with the cGMP phosphodiesterase. The amplitudes of both components depend exclusively on the membrane bound T-GDP pool. The kinetics of the loss component is limited by the size and degree of permeation of the rod fragments, rather than by the dissociation rate of T
-GTP from the membrane.Abbreviations ROS
rod outer segment
- R
rhodopsin
- R*
photoactivated rhodopsin
-
T, T-GDP, T
-GDP, T
-GTP, T
transducin and its various forms
-
T
mb, T
sol: T
bound to membrane or soluble
- PDE
cGMP-phosphodiesterase
- GTP
guanosine 5-triphosphate
- GDP
guanosine 5-diphosphate
- GDP S
guanosine 5-O-(2-thiodiphosphate)
- cGMP
guanosine-3-5 cyclic-monophosphate
- DTT
dithiothreitol
- HEPES
4-(2-hydroxyethyl)-1-piperazine-ethane sulfonic acid
- TRIS
Tris (hydroxymethyl)aminomethane
- SDS
sodium dodecyl sulfate 相似文献
10.
Fumiaki Nakatsubo T. Kent Kirk Mikio Shimada Takayoshi Higuchi 《Archives of microbiology》1981,128(4):416-420
The degradation of the phenylcoumaran substructure model compound methyl dehydrodiconiferyl alcohol by the white-rot wood decay fungus Phanerochaete chrysosporium was investigated using culture conditions optimized for lignin oxidation. Initial attack was in the cinnamyl alcohol side chain, which was oxidized to a glycerol structure. This was subsequently converted by loss of the two terminal carbon atoms, C and C, to yield a C-aldehyde structure, which was further oxidized to the C-acid compound. The next detected intermediate, a phenylcoumarone, was produced by double bond formation between C and C, and oxidation of the C-alcohol to an aldehyde group. Further oxidation of C to an acid yielded the next intermediate. The final identified degradation product was veratric acid. No products from the 5-substituted aromatic ring, and no phenolic products, were found. The initial glycerol-containing intermediate was a mixture of the threo and erythro forms, and no optical activity could be found, suggesting that its formation might have involved nonstereospecific C-C epoxidation followed by non-enzymatic hydrolysis of the epoxide.Abbreviations TLC
thin layer chromatography
- LDA
lithium diisopropyl amide
- DDQ
2,3-dichloro-5,6-dicyanobenzoquinone
- MS
mass spectrometry
- UV
ultraviolet spectroscopy 相似文献
11.
Richard P. Shank 《Neurochemical research》1992,17(5):423-430
Synaptosome-enriched preparations from rat and guinea pig brain tissue vigorously accumulated [3H]-adenosine 5-monophosphate ([3H]AMP). When the accumulation of [3H]AMP was determined using incubation periods of 30 s or less, high concentrations of adenosine, dipyridamole and soluflazine did not inhibit the accumulation of label appreciably. The accumulation of [3H]AMP was saturable, temperature-dependent, osmotic-sensitive and exhibited structural specificity. Based on the kinetics of uptake by different subcellular fractions, and the inhibitory effects of other nucleotides, the uptake of AMP appeared to be mediated by three saturable systems with Kt values of approximately 0.2, 6, and 100 M. The transport system with the highest affinity for AMP was selectively inhibited by guanosine 5-monophosphate, and its Vmax was several fold higher in a myelin-enriched fraction than in synaptosome-enriched fractions. The transport system with the Kt6 M was selectively inhibited by ,-methylene adenosine diphosphate, and its Vmax was several times higher in a fraction enriched in high-density synaptosomes than in fractions enriched in low-density synaptosomes or myelin. Both of these transport systems were potently inhibited by ATP and ADP. Nucleotides that were either weak or inactive as inhibitors of AMP transport included 3-AMP, cyclic AMP, guanosine 5-diphosphate, and the 5-mononucleotides of cytosine, inosine, and uridine. GTP consistently enhanced uptake at concentrations 1 M. The transport of AMP was not Na+-dependent and was not inhibited by membrane depolarization. This transport system may mediate the release of AMP for subsequent conversion to adenosine extracellularly.Abbreviations used HEPES
N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid
- NBTI
nitrobenzylthioinosine
- ,-MeADP
,-methylene adenosine diphosphate
- GTPgS
guanosine-5-O-(3-thiotriphosphate)
Special issue dedicated to Dr. Morris H. Aprison. 相似文献
12.
Summary Two double heterozygous 0/0 thalassemic sibs of Mexican descent were studied. The father had a 0/0 genotype, while the mother, one sib and several maternal relatives were 0/0 heterozygotes. Parental consanguinity and an apparently low frequency of thalassemia among Mexicans suggested a possible common origin of both 0 and 0 genes. A hypothesis to explain such a possibility is proposed on the basis of a partial mispairing between 0 and genes followed by a crossing-over which would results in a 0 recombinant gene. This hypothesis could also be extended to explain the 22 gluala, 22 alaglu and 116 arghis Hb variants as recombinants from double crossing-over between and mispaired genes for which the name interstitial-Lepore is proposed. 相似文献
13.
Jiménez Blanco JL van Rooijen JJ Erbel PJ Leeflang BR Kamerling JP Vliegenthart JF 《Journal of biomolecular NMR》2000,16(1):59-77
The conformational behaviour of the spacer-linked synthetic Sda tetrasaccharide -d-GalpNAc-(14)-[-Neu5Ac-(23)]--d-Galp-(14)--d-GlcpNAc-(1O)(CH2)5NH2 (1) and the two mimics -d-Galp-(14)-[-Neu5Ac-(23)]--d-Galp-(14)--d-GlcpNAc-(1O)(CH2)5NH2 (2) and -d-GlcpNAc-(14)-[-Neu5Ac-(23)]--d-Galp-(14)--d-GlcpNAc-(1O)(CH2)5NH2 (3) were investigated by 1H NMR spectroscopy in combination with molecular dynamics (MD) simulations in water. Experimental 2D 1H ROESY cross-peak intensities (ROEs) of the tetrasaccharides were compared with calculated ROEs derived from MD trajectories using the CROSREL program. Analysis of these data indicated that the oligosaccharidic skeletons of the compounds 1–3 are rather rigid, especially the -d-Hex(NAc)-(14)-[-Neu5Ac-(23)]--d-Galp fragments. The - Neu5-Ac-(23)--d-Galp linkage occurred in two different energy minima in the three-dimensional structure of the compounds 1–3 in aqueous solution. Experimental data and dynamics simulations supported the finding that the higher energy rotamer (CHEAT forcefield) was abundant in compounds 1 and 3 due to the existence of a hydrogen bond between the carboxyl group of the sialic acid and the acetamido group of the terminal monosaccharide (GalNAc or GlcNAc) unit. The conformational similarity between 1 and 3 leads to the suggestion that also their activities will be alike. 相似文献
14.
A statistical analysis of protein conformations in terms of the distance between residues, represented by their C atoms, is presented. We consider four factors that contribute to the determination of the distanced
i,i+k
between a given pair ofith and(i+k)th residues in the native conformation of a globular protein: (1) the distancek along the chain, (2) the size of the protein, (3) the conformational states of theith to(i+k)th residues, and (4) the amino acid types of the and(i+k)th residues. In order to account for the dependence on the distancek along the chain, the statistics are taken for three ranges, viz., short, medium, and long ranges (k8; 9k20; andk21; respectively). In the statistics of short-range distances, a mean distanceD
k
and its standard deviationS
k
are calculated for each value ofk, with and without taking into account the conformational states of all residues fromi toi+k (factors 1 and 3). As an Appendix, the relations for converting from the distances between residues into other conformational parameters are discussed. In the statistics of long-range distances, a reduced distanced*
ij
(the actual distance divided by the radius of gyration) is used to scale the data so that they become independent of protein size, and then a mean reduced distanceD
l (a, a) and its standard deviation l (a, a) are calculated for each amino acid pair (a, a) (factors 2 and 4). The effect of the neighboring residues along the chain on the value of the distanced*
ij
is explored by a linear regression analysis between the actual reduced distanced*
ij
and the mean value over theD
l for all possible pairs of residues in the two segments of the (i–2)th to the (i+2)th and the (j–2)th to the (j+2)th residues. The effect is assessed in terms of the tangentA
l (a, a) of the calculated regression line for each amino acid pair (a, a). In the statistics of medium-range distances, only factors 1 and 4 are considered, to simplify the analysis. The scaled distanced
i,i+k
=(d
i,i+k
-D
k
)/S
k
is used to eliminate the dependence onk, the distance along the chain. The propertiesD
m (a, a), m (a, a) andA
m (a, a) corresponding toD
l (a, a), l (a, a), andA
l (a, a), and also calculated for each amino acid pair (a, a). The results are interpreted as follows: the smaller values ofD
l (a, a) andD
m (a, a) indicate a preference of the pair (a, a) for a contact (e.g., pairs between hydrophobic amino acids, and pairs of Cys with aromatic amino acids), and the larger values of these quantities indicate a preference for distant mutual location (e.g., pairs between strong hydrophilic amino acids); the smaller values of l (a, a) and m (a, a) indicate a strong preference for either contact or noncontact (e.g., pairs between hydrophobic amino acids, and pairs between strong hydrophobic and hydrophilic amino acids, respectively), and the larger values of these quantities indicate the ambivalent/neutral nature of the preference for contact and noncontact (e.g., pairs containing Ser or Thr); the smaller values ofA
l (a, a) andA
m (a, a) indicate that the distance of an (a, a) pair is determined independently of the amino acid character of the neighboring residues along the chain (e.g., some pairs of Cys or Met with other amino acids) and the larger values of these quantities indicare that such amino acid character contributes strongly to the determination of the distance (e.g., pairs containing Ser or Thr, and pairs between amino acids with small side chains). The difference between the statistics for the long- and medium-range distances is also discussed; the former reflect the difference between the hydrophobic and hydrophilic character of the residues, but the latter cannot be easily interpretable only in terms of hydrophobicity and hydrophilicity. The data analyzed here are used in the optimization of an object function to compute protein conformation in a subsequent paper. 相似文献
15.
Summary The one-bond deuterium isotope shift effect for glycine C resonances exhibits a conformational dependence comparable to that of the corresponding 1JHC scalar coupling in both magnitude (11 Hz at 14.1 T) and dihedral angle dependence. The similarity in the conformational dependence of the 1JHC and deuterium isotope shift values suggests a common physical basis. Given the known distribution of (,) main-chain dihedral angles for glycine residues, the deuterium isotope shifts and the 1JHC scalar couplings can determine conformations in the left-and right-handed helical-to-bridge regions of the (,) plane to an accuracy of approximately 13°. In the absence of stereochemical assignments, the differential deuterium isotope shifts and the 1JHC scalar couplings can be combined with limited independent structural information (e.g., the sign of ) to determine the chirality of the deuterium substitution. 相似文献
16.
Effect of temperature and additional carbon sources on phenol degradation by an indigenous soil <Emphasis Type="Italic">Pseudomonad</Emphasis> 总被引:3,自引:0,他引:3
A new indigenous soil bacterium Pseudomonas sp. growing on phenol and on a mixture of phenol, toluene, o-cresol, naphthalene and 1,2,3-trimethylbenzene (1,2,3-TMB) was isolated and characterized. Phylogenetic analysis suggested its classification to Pseudomonadaceae family and showed 99.8% DNA sequence identity to Pseudomonas pseudoalcaligenes species. The isolate was psychrotroph, with growth temperatures ranging from ca. 0 to 40 °C. The GC–MS structural analysis of metabolic products of phenol degradation by this microorganism indicated a possible ortho cleavage pathway for high concentrations (over 200 mg L–1) of phenol. Biodegradation rates by this species were found to be three times more effective than those previously reported by other Pseudomonas strains. The effect of temperature on phenol degradation was studied in batch cultures at temperatures ranging from 10 to 40°C and different initial phenol concentrations (up to 500mgL–1). Above 300mgL–1 of initial phenol concentration no considerable depletion was recorded at both 10 and 40°C. Maximum degradation rates for phenol were recorded at 30°C. The biodegradation rate of phenol was studied also in the presence of additional carbon sources (o-cresol, toluene, naphthalene, 1,2,3-TMB) at the optimum growth temperature and was found significantly lower by a factor of eight in respect to the strong competitive inhibition between the substrates and the more available sources of carbon and energy. The Haldane equation =m S/(KS+S+S2/KI) was found to best fit the experimental data at the optimum temperature of 30°C than the Monod equation with kinetic constants m=0.27h–1, KS=56.70mgL–1, KI=249.08mgL–1. 相似文献
17.
Heise B Leppert J Wenschuh H Ohlenschläger O Görlach M Ramachandran R 《Journal of biomolecular NMR》2001,19(2):167-179
An approach to the determination of the orientation of the carbonyl chemical shift (CS) tensor in a 13C-15N-1H dipolar coupled spin network is proposed. The method involves the measurement of the Euler angles of the 13C-15N and 15N-1H dipolar vectors in the 13C CS tensor principal axes system, respectively, via a 13C-15N REDOR experiment and by a 2D relayed anisotropy correlation of the 13C CSA (2) and 15N-1H dipolar interaction (1). Via numerical simulations the sensitivity of the 1 cross sections of the 2D spectrum to the Euler angles of the 15N-1H bond vector in the 13C CSA frame is shown. Employing the procedure outlined in this work, we have determined the orientation of the 13C CS tensor in the peptide plane of the dipeptide AibAib-NH2 (Aib = -aminoisobutyric acid). The Euler angles are found to be (CN, CN) = (34° ± 2°, 88° ± 2° ) and (NH, NH) = (90° ± 10°, 80° ± 10° ). From the measured Euler angles it is seen that the 33 and 22 components of the 13C CS tensor approximately lie in the peptide plane. 相似文献
18.
Alicia Mimbrera Luis Rivas Faustino Mollinedo Emilio Muñoz Vicente Larraga 《Molecular and cellular biochemistry》1983,56(1):73-80
Summary The combined use of proteolytic digestion and lactoperoxidase catalyzed labelling with [125I] applied to membrane-bound or soluble pure F1-ATPase from Micrococcus lysodeikticus has allowed us to establish the topography of its , , and subunits within the protein molecule and with respect to the plane of the membrane.The subunit is most externally located to the membrane bilayer looking towards the cytoplasmic face, a position consistent with its proposed catalytic role. The and subunits lie in an intermediate layer between the subunits and the membrane, in which the subunit occupies a central position within the F1-ATPase molecule in contact with the subunit. The subunit appears to be tightly bound to the F0 component of the ATPase complex, probably buried in the membrane bilayer. A molecular arrangement of M. lysodeikticus ATPase is proposed that, taking into account the subunit stoichiometry 3 3 2 2 (MW 420 000), accommodates the role assigned to each subunit and most, if not all, the known properties of this bacterial energy-transducing protein. 相似文献
19.
The cyclic 35-nucleotide phosphodiesterase D3 was purified from Sinorhizobium fredii MAR-1. The native enzyme had a molecular weight of approximately 44.5kDa and a subunit molecular weight of approximately 21kDa as judged by SDS-gel electrophoresis. The pH optimum of the enzyme for the hydrolysis of cyclic AMP was approximately 6.0 with both acetate and Tris-maleate buffers. The optimum temperature for hydrolysing cyclic AMP was approximately 50C. No metal ion was required for activity and EDTA up to 2.5mM did not markedly affect the enzyme. However, methylxanthines, adenine and adenosine as well as 5-AMP, ATP, ADP and metal ions like Zn2+, Fe2+, Pb2+, Al3+ and Fe3+, were strongly inhibitory at 2.5mM.The D3 enzyme could hydrolyse both cyclic AMP and cyclic GMP with the apparent K
m for cyclic AMP of approximately 0.23M. 相似文献
20.
Hawaii's dry forests are among the most endangered of all ecosystems in the archipelago. Invasion of alien plant species into these ecosystems is one of the most significant threats to on-going efforts to preserve and restore Hawaii's remaining dry forests. Comparing the physiological performance of alien and native species can offer causal explanations behind the relative success of alien plant invasions within Hawaiian dry forests and elsewhere. We compared maximum rates of net CO2 assimilation, water-use efficiency (WUE), daily carbon gain, and leaf morphology for three native and two alien shrubby species growing within 1-m2 plots under two natural light (sub-canopy shade relative to open full sunlight) treatments. Maximum rates of net CO2 assimilation were similar between alien and native species (8.15 vs. 7.12molm–2s–1, respectively), however, native plants exhibited lower stomatal conductance and higher instantaneous WUE than alien plants in all treatments (0.13molm–2s–1 and 72.36mol CO2mol H2O–1 against 0.23 and 58.78, respectively). Alien plants had approximately 65% more aboveground biomass than native plants. This result may reflect differential seed production and seed bank viability between native and alien species. We found an overall strong, positive correlation between species-specific physiological traits and final species aboveground biomass. Based on this type of information we can predict species-specific boundaries across light gradients, and focus restoration efforts accordingly. 相似文献