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1.
Claudia P. Spampinato Piotr Paneth Marion H. O'Leary Carlos S. Andreo 《Photosynthesis research》1991,28(2):69-76
Structural analogues of the NADP+ were studied as potential coenzymes and inhibitors for NADP+ dependent malic enzyme from Zea mays L. leaves. Results showed that 1, N6-etheno-nicotinamide adenine dinucleotide phosphate ( NADP+), 3-acetylpyridine-adenine dinucleotide phosphate (APADP+), nicotinamide-hypoxanthine dinucleotide phosphate (NHDP+) and -nicotinamide adenine dinucleotide 2: 3-cyclic monophosphate (23NADPc+) act as alternate coenzymes for the enzyme and that there is little variation in the values of the Michaelis constants and only a threefold variation in Vmax for the five nucleotides. On the other hand, thionicotinamide-adenine dinucleotide phosphate (SNADP+), 3-aminopyridine-adenine dinucleotide phosphate (AADP+), adenosine 2-monophosphate (2AMP) and adenosine 2: 3-cyclic monophosphate (23AMPc) were competitive inhibitors with respect to NADP+, while -nicotinamide adenine dinucleotide 3-phosphate (3NADP+), NAD+, adenosine 3-monophosphate (3AMP), adenosine 2: 5-cyclic monophosphate (25AMPc), 5AMP, 5ADP, 5ATP and adenosine act as non-competitive inhibitors. These results, together with results of semiempirical self-consistent field-molecular orbitals calculations, suggest that the 2-phosphate group is crucial for the nucleotide binding to the enzyme, whereas the charge density on the C4 atom of the pyridine ring is the major factor that governs the coenzyme activity.Abbreviations NADP+
1, N6-etheno-nicotinamide adenine dinucleotide phosphate
- NHDP+
nicotinamide-hypoxanthine dinucleotide phosphate
- APADP+
3-acetylpyridine-adenine dinucleotide phosphate
- SNADP+
thionicotinamide-adenine dinucleotide phosphate
- AADP+
3-aminopyridine-adenine dinucleotide phosphate
- 23NADPc+
-nicotinamide adenine dinucleotide 2: 3-cyclic monophosphate
- 3NADP+
-nicotinamide adenine dinucleotide 3-phosphate
- 2AMP
adenosine 2-monophosphate
- 3AMP
adenosine 3-monophosphate
- 23AMPc
adenosine 2: 3 monophosphate cyclic
- A
adenosine
- RuBP
ribulose 1,5-bisphosphate
- SCF-MO
Self-Consistent Field-Molecular Orbitals (method) 相似文献
2.
Summary The perdeuteration of aliphatic sites in large proteins has been shown to greatly facilitate the process of sequential backbone and side-chain 13C assignments and has also been utilized in obtaining long-range NOE distance restraints for structure calculations. To obtain the maximum information from a 4D 15N/15N-separated NOESY, as many main-chain and side-chain 1HN/15N resonances as possible must be assigned. Traditionally, only backbone amide 1HN/15N resonances are assigned by correlation experiments, whereas slowly exchanging side-chain amide, amino, and guanidino protons are assigned by NOEs to side-chain aliphatic protons. In a perdeuterated protein, however, there is a minimal number of such protons. We have therefore developed several gradient-enhanced and sensitivity-enhanced pulse sequences, containing water-flipback pulses, to provide through-bond correlations of the aliphatic side-chain 1HN/15N resonances to side-chain 13C resonances with high sensitivity: NH2-filtered 2D 1H-15N HSQC (H2N-HSQC), 3D H2N(CO)C/ and 3D H2N(COC/)C/ for glutamine and asparagine side-chain amide groups; 2D refocused H(N/)C/ and H(N/C/)C/ for arginine side-chain amino groups and non-refocused versions for lysine side-chain amino groups; and 2D refocused H(N)C and nonrefocused H(N.)C for arginine side-chain guanidino groups. These pulse sequences have been applied to perdeuterated 13C-/15N-labeled human carbonic anhydrase II (2H-HCA II). Because more than 95% of all side-chain 13C resonances in 2H-HCA II have already been assigned with the C(CC)(CO)NH experiment, the assignment of the side-chain 1HN/15N resonances has been straightforward using the pulse sequences mentioned above. The importance of assigning these side-chain HN protons has been demonstrated by recent studies in which the calculation of protein global folds was simulated using only 1HN-1HN NOE restraints. In these studies, the inclusion of NOE restraints to side-chain HN protons significantly improved the quality of the global fold that could be determined for a perdeuterated protein [R.A. Venters et al. (1995) J. Am. Chem. Soc., 117, 9592–9593].To whom correspondence should be addressed. 相似文献
3.
Hiroaki Sawai 《Journal of molecular evolution》1981,17(1):48-51
Summary Oligouridylates with more than eight chain units can serve as a template for the template-directed condensation of ImpA catalyzed by Pb2+ ion. The templates and the Pb2+ ion catalyst facilitate the formation of longer oligoadenylates with five or more units. The ratio of 3–5 linked oligomers to the 2–5 isomers increases with increasing chain length of the oligouridylate template. Short oligouridylates up to a hexamer tend to decrease the yield of oligoadenylates, and do not affect the selectivity of internucleotide linkage.Abbreviations EDTA
ethylenediaminetetracetic acid
- Tris
tris(hydroxymethyl)aminomethane
- A
adenosine
- ImpA
adenosine 5-phosphorimidazolide
- pA
adenosine 5-phosphate
- Ap
adenosine 2(3)-phosphate
- poly A
polyadenylic acid
- AppA
P1,P2-diadenosine 5-diphosphate
- pAp
adenosine 2(3),5-diphosphate
- ApA
adenylyl adenosine
- (pA)n (n = 2,3,)
oligomers of pA
- ImpApA
5-phosphorimidazolide of ApA
- U
uridine
- pU
uridine 5-phosphate
- Up
uridine 2(3)-phosphate
- poly U
polyuridylic acid
- pUp
uridine 2(3),5-diphosphate
- (pU)n (n = 2,3,)
oligomers of pU
- (pU)n – (pA)m
cooligomers composed of (pU)n and (pA)m units
- AppUpUpUpUp
pyrophosphate derived from pA and (pU)4
- AppUp
P1-(adenosine 5)-P2-(uridine 2(3)-phosphate 5) -pyrophosphate
- BAP
bacterial alkaline phosphatase
- VPD
venom phosphodiesterase
- N.P1
nuclease P1
- RNase A
pancreatic ribonuclease
- A*
radioactive adenosine 相似文献
4.
Addi R. Fadel Dan Q. Jin Gaetano T. Montelione Ronald M. Levy 《Journal of biomolecular NMR》1995,6(2):221-226
Summary Order parameters for the backbone N–H and C–H bond vectors have been calculated from a 150 ps molecular dynamics (MD) simulation of human type- transforming growth factor in H2O solvent. Two kinds of crankshaft motions of the polypeptide backbone are observed in this MD trajectory. The first involves small-amplitude rocking of the rigid peptide bond due to correlated changes in the backbone dihedral angles i–1 and i. These high-frequency librational crankshaft motions are correlated with systematically smaller values of motional order parameters for backbone N–H bond vectors compared to C–H bond vectors. In addition, infrequent crankshaft flips of the peptide bond from one local minimum to another are observed for several amino acid residues. These MD simulations demonstrate that comparisons of N–H and C–H order parameters provide a useful approach for identifying crank-shaft librational motions in proteins. 相似文献
5.
The continuous control of the maximum position of the dye absorption band (the zero of the derivative dD
()/d of the cell's optical density D
()) in a nematic matrix is demonstrated experimentally, as a result of changing the angle between the optical axis of a planar-oriented sample and the plane of polarization of absorbed light incident normal to the optical axis. The theory proposed describes quantitatively the experimental dependence (). The rotation of the polarizer with given frequency results in the spectral position modulation of the solute band maximum () within (=0°)–(90°)=700 cm–1. 相似文献
6.
Summary Short oligocytidylates can act as templates for the self-condensation of guanosine 5-phosphorimidazolide. In the absence of a catalytic metal ion or in the presence of Pb2+ a noticeable template effect is already observed with the dimer and the yield of long oligomers reaches a plateau with a hexamer template. Short templates give oligomers longers than the template length. The products are predominantly 2-5 linked for the Pb2+-catalyzed reaction while mixed linkages are observed in the uncatalyzed reaction.In the presence of Zn2+, a template effect is first observed with the pentamer and is maximal by the heptamer. The products are predominantly 3-5 linked. Oligomers shorter than or as long as the template are obtained in substantial yield, and longer products in much lower yields.Abbreviations G
Guanosine
- Gp
guanosine 2(3)-phosphate
- pG
guanosine 5-phosphate
- Gp!
guanosine cyclic 2,3-phosphate
- ImpG
guanosine 5-phosphorimidazolide
- ImpG*
[8-14C]-guanosine 5-phosphorimidazolide
- pGp
5-phosphoguanosine 2(3)-phosphate
- G2pG
guanylyl-[2-5]-guanosine
- G3pG
guanylyl-[3-5]-guanosine
- ImpGpG
5-phosphorimidazolide of GpG
- (pG)n (n = 2,3)
oligomers of pG
- GppG
P1, P2-diguanosine 5-diphosphate
- GppGpG
5-[guanosine 5-pyrophosphate] of GpG
- NH2pG
guanosine 5-phosphoramidate
- (pG)4+
tetramer and higher oligoguanylates with 5 terminal phosphate
- oligo(G)
oligoguanylate
- Cp
cytidine 2(3)-phosphate
- Cp!
cytidine cyclic 2,3-phosphate
- (Cp)n–1 Cp! (n= 2,3,4)
oligocytidylates terminated by 5-OH groups and 2,3-cyclic phosphates
- oligo(C)
oligocytidylate
- poly(C)
polycytidylic acid
- poly(U)
polyuridylic acid
- poly(C,G)
random copolymer of C and G
- BAP
bacterial alkaline phosphatase (E. coli)
- EDTA
ethylenediaminetetraacetic acid
- Rf
chromatographic mobility 相似文献
7.
Shafer FE Dropulic B Ely C Schaefer CA Freas D Witkowska HE Schechter AN Noguchi CT Dewey M Karlsson S 《Journal of biomedical science》1994,1(3):147-153
Two transgenic lines of mice were produced which contained the S
Antilles- and 2-hemoglobin genes trandemly coupled to the micro locus control region (LCR). The LCRS
Antilles2-hemoglobin transgenic mice expressed high levels of 2-hemoglobin while S
Antilles-hemoglobin expression was virtually undetectable. Abundant 2-hemoglobin protein was observed in the blood of transgenic mice, while S
Antilles-hemoglobin chains could not be detected. Transgenic red blood cells had substantially decreased sensitivity to osmotic lysis. Attempts to produce homozygotes containing the transgene were unsuccessful. The phenotype of these mice closely resembles that of -thalassemic mice. The LCRS
Antilles2 transgenic mice demonstrate that if the LCR is coupled to the S
Antilles- and 2-hemoglobin genes in tandem, only the distal 2-hemoglobin gene is selected for expression to significant levels in adult mice. These results support a reciprocally competitive model for LCR-hemoglobin developmental switching. 相似文献
8.
Summary Simple pseudo-3D modifications to the constant-time HSQC and HCACO experiments are described that allow accurate (±0.5 Hz) measurement of one bond JCH coupling constants in proteins that are uniformly enriched with 13C. An empirical ,-surface is calculated which describes the deviation of 1JCH from its random coil value, using 203 1JCH values measured for residues in the proteins calmodulin, staphylococcal nuclease, and basic pancreatic trypsin inhibitor, for which and are know with good precision from previous X-ray crystallographic studies. Residues in -helical conformation exhibit positive deviations of 4–5 Hz, whereas deviations in -sheet are small and, on average, slightly negative. Data indicate that 1JCH depends primarily on , and that 1JCH may be useful as a qualitative probe for secondary structure. Comparison of 1JCH coupling constants measured in free calmodulin and in its complex with a 26-aminoacid peptide fragment of myosin light-chain kinase confirm that the calmodulin secondary structure is retained upon complexation but that disruption of the middle part of the central helix is even more extensive than in free calmodulin.
Supplementary material available from the authors: One table listing 352 1JCH and 1J-values, together with ,-values for 203 residues of known conformation. Two figures showing (a) a Ramachandran plot of the ,-values of 203 residues used in deriving 1J(,), and (b) the r.m.s.d. 1J(,) distribution. 相似文献
9.
Bodrova ME Brailovskaya IV Efron GI Starkov AA Mokhova EN 《Biochemistry. Biokhimii?a》2003,68(4):391-398
At low Ca2+ concentrations the pore of the inner mitochondrial membrane can open in substates with lower permeability (Hunter, D. R., and Haworth, R. A. (1979) Arch. Biochem. Biophys., 195, 468-477). Recently, we showed that Ca2+ loading of mitochondria augments the cyclosporin A-dependent decrease in transmembrane potential () across the inner mitochondrial membrane caused by 10 M myristic acid but does not affect the stimulation of respiration by this fatty acid. We have proposed that in our experiments the pore opened in a substate with lower permeability rather than in the classic state (Bodrova, M. E., et al. (2000) IUBMB Life, 50, 189-194). Here we show that under conditions lowering the probability of classic pore opening in Ca2+-loaded mitochondria myristic acid induces the cyclosporin A-sensitive decrease and mitochondrial swelling more effectively than uncoupler SF6847 does, though their protonophoric activities are equal. In the absence of Pi and presence of succinate and rotenone (with or without glutamate) cyclosporin A either reversed or only stopped decrease induced by 5 M myristic acid and 5 M Ca2+. In the last case nigericin, when added after cyclosporin A, reversed the decrease, and the following addition of EGTA produced only a weak (if any) increase. In Pi-containing medium (in the presence of glutamate and malate) cyclosporin A reversed the decrease. These data show that the cyclosporin A-sensitive decrease in by low concentrations of fatty acids and Ca2+ cannot be explained by specific uncoupling effect of fatty acid. We propose that: 1) low concentrations of Ca2+ and fatty acid induce the pore opening in a substate with a selective cation permeability, and the cyclosporin A-sensitive decrease results from a conversion of to pH gradient due to the electrogenic cation transport in mitochondria; 2) the ADP/ATP-antiporter is involved in this process; 3) higher efficiency of fatty acid compared to SF6847 in the Ca2+-dependent pore opening seems to be due to its interaction with the nucleotide-binding site of the ADP/ATP-antiporter and higher affinity of fatty acids to cations. 相似文献
10.
M. K. Banerjee M. K. Kalloo 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1987,73(5):707-710
Summary One hundred and twenty-two varieties, lines and wild accessions of Lycopersicon were screened under three different regimes during the autumn/winter season of 1982–83 and 1983–84 for resistance to tomato leaf curl virus (TLCV). L. hirsutum f. glabratum (B6013) and L. hirsutum f. typicum (A1904) proved to be highly resistant to TLCV in all three environments. Various accessions of L. peruvianum were also highly resistant. L. pimpinellifolium (A1921) exhibited no TLCV symptoms within 90 days. Of the cultivated varieties, Acc 99 exhibited the minimim score for susceptibility; AC 142, Collection No. 2, Kalyanpur Angurlata and HS 101 had a low rating for virus incidence. The inheritance of resistance was studied in the interspecific crosses between a TLCV resistant line of L. pimpinellifolium (A1921) and five (HS 101, HS 102, HS 110, Pusa Ruby and Punjab Chhuhara) susceptible cultivars of L. esculentum. Parents, F1, F2 and backcross progenies were artificially inoculated with local strains of TLCV using vector the viruliferious whitefly, Bemisia tabaci (Genn.). Data indicated that the resistance of L. pimpinellifolium (A 1921) is monogenic and incompletely dominant over susceptibility. 相似文献
11.
Ben A. Bulthuis Gregory M. Koningstein Adriaan H. Stouthamer Henk W. van Verseveld 《Antonie van Leeuwenhoek》1993,63(1):1-16
The magnitude of the proton motive force (p) and its constituents, the electrical () and chemical potential (-ZpH), were established for chemostat cultures of a protease-producing, relaxed (rel
–) variant and a not protease-producing, stringent (rel
+) variant of an industrial strain ofBacillus licheniformis (respectively referred to as the A- and the B-type). For both types, an inverse relation of p with the specific growth rate was found. The calculated intracellular pH (pHin) was not constant but inversely related to . This change in pHin might be related to regulatory functions of metabolism but a regulatory role for pHin itself could not be envisaged. Measurement of the adenylate energy charge (EC) showed a direct relation with for glucose-limited chemostat cultures; in nitrogen-limited chemostat cultures, the EC showed an approximately constant value at low and an increased value at higher . For both limitations, the ATP/ADP ratio was directly related to .The phosphorylation potential (G'p) was invariant with . From the values for G'p and p, a variable H+/ATP-stoichiometry was inferred: H+/ATP=1.83+0.52µ, so that at a given H+/O-ratio of four (4), the apparent P/O-ratio (inferred from regression analysis) showed a decline of 2.16 to 1.87 for =0 to max (we discuss how more than half of this decline will be independent of any change in internal cell-volume). We propose that the constancy of G'p and the decrease in the efficiency of energy-conservation (P/O-value) with increasing are a way in which the cells try to cope with an apparent less than perfect coordination between anabolism and catabolism to keep up the highest possible with a minimum loss of growth-efficiency. Protease production in nitrogen-limited cultures as compared to glucose-limited cultures, and the difference between the A- and B-type, could not be explained by a different energy-status of the cells.Abbreviations CCCP
carbonylcyanide-p-trichloromethoxyphenylhydrazone
- DW
dry weight of biomass
- F
Faraday's constant, 96.6 J/(mV × mol)
- Fo
chemostat outflow-rate (ml/h)
- FCCP
carbonylcyanide-p-trifluoromethoxyphenylhydrazone
- G'p
phosphorylation potential, the Gibbs energy change for ATP-synthesis from ADP and Pi
- G'0p
standard Gibbs energy change at specified conditions
- H+/ATP
number of protons translocated through
- ATP
synthase in synthesis of one ATP
- H+/O
protons translocated during transfer of 2 electrons from substrate to oxygen
-
specific growth rate (1/h)
- H+
transmembrane electrochemical proton potential, J/mol
- Mb
molar weight (147.6 g/mol) of bacteria with general cell formula C6.0H10.8O3.0N1.2
- pHout,in
extracellular, intracellular pH
- Pi
(intracellular) inorganic phosphate
- p
proton motive force, mV
- pH
transmembrane pH-difference
-
transmembrane electrical potential, mV
- P/O
number of ADP phosphorylated to ATP upon reduction of one O2– to H2O by two electrons transferred through the electron transfer chain
- P/O
(H+/O) × (H+/ATP)–1
- P/OF, P/ON
P/O with the two electrons donated by resp. (NADH + H+) and FADH
- q
specific rate of consumption or production (mol/g DW × h)
-
rel
+,rel
–
stringent, relaxed genotype
- R
universal gas constant, 8.36 J/(mol × degree)
- T
absolute temperature
- TPMP+
triphenylmethylphosphonium ion
- TPP+
tetraphenyl phosphonium ion
- Y
growth yield, g DW/mol
- Z
conversion constant=61.8 mV for 310 K (37 °C)
- ZpH
transmembrane proton potential or chemical potential, mV 相似文献
12.
Natural abundance of 15N ( 15N) of leaves harvested from tropical plants in Brazil and Thailand was analyzed. The 15N values of non-N2-fixing trees in Brazil were +4.5±1.9, which is lower than those of soil nitrogen (+8.0±2.2). In contrast, mimosa and kudzu had very low 15N values (–1.4+0.5). The 15N values of Panicum maximum and leguminous trees, except Leucaena leucocephala, were similar to those of non-N2-fixing trees, suggesting that the contribution of fixed N in these plants is negligible. The 15N values of non-N2-fixing trees in Thailand were +4.9±2.0. Leucaena leucocephala, Sesbania grandiflora, Casuarina spp. and Cycas spp. had low 15N values, close to the value of atmospheric N2 (0), pointing to a major contribution of N2 fixation in these plants. Cassia spp. and Tamarindus indica had high 15N values, which confirms that these species are non-nodulating legumes. The 15N values of Acacia spp. and Gliricidia sepium and other potentially nodulating tree legumes were, on average, slightly lower than those of non-N2-fixing trees, indicating a small contribution of N2 fixation in these legumes. 相似文献
13.
The regulation of total creatine content in a myoblast cell line 总被引:5,自引:0,他引:5
Joseph E. Odoom Graham J. Kemp George K. Radda 《Molecular and cellular biochemistry》1996,158(2):179-188
Total cellular creatine content is an important bioenergetic parameter in skeletal muscle. To understand its regulation we investigated creatine transport and accumulation in the G8 cultured skeletal myoblast line. Like other cell types, these contain a creatine transporter, whose activity, measured using a radiolabelling technique, was saturable (Km = 110 ± 25 M) and largely dependent on extracellular [Na+]. To study sustained influences on steady state creatine concentration we measured total cellular creatine content using a fluorimetric method in 48 h incubations. We found that the total cellular creatine content was relatively independent of extracellular creatine concentration, consistent with high affinity sodium-dependent uptake balanced by slow passive efflux. Accordingly, in creatine-free incubations net creatine efflux was slow ( 5 ± 1 % of basal creatine content per day over 6 days), while creatine content in 48 h incubations was reduced by 28 ± 13% of control by the Na+,K+-ATPase inhibitor ouabain. Creatine accumulation after 48 h was stimulated by treatment with the mixed - and -adrenergic agonist noradrenaline, the -adrenergic agonist isoproterenol, the 2-agonist clenbuterol and the cAMP analogue N6,2-O-dibutyryladenosine 3,5-cyclic monophosphate, but was unaffected by the 1 adrenergic agonist methoxamine. The noradrenaline enhancement of creatine accumulation at 48 h was inhibited by the mixed - and -antagonist labetalol and by the -antagonist propranolol, but was unaffected by the 2 antagonist phentolamine; greater inhibition was caused by the 2 antagonist butoxamine than the 1 antagonist atenolol. Creatine accumulation at 48 h was increased to 230 ± 6% of control by insulin and by 140 ± 13% by IGF-I (both at 3 nM). Creatine accumulation at 48 h was also increased to 280 ± 40% of control by 3,3,5-triiodothyronine (at 70 M) and to 220 ± 35% of control by amylin (60 nM). As 3,3,5-triiodothyronine, amylin and isoproterenol all stimulate the Na+,K+-ATPase, we suggest that they stimulate Na+-creatine cotransport indirectly by increasing the transmembrane [Na+] concentration gradient and membrane potential.Abbreviations IGF-I
insulin-like growth factor I
- IGF-II
insulin-like growth factor II
- T3
3,3,5-triiodothyronine
- CGRP
calcitonin gene-related peptide 相似文献
14.
Soil organic carbon dynamics: variability with depth in forested and deforested soils under pasture in Costa Rica 总被引:5,自引:2,他引:5
Dynamics of soil organic carbon (SOC) inchronosequences of soils below forests that had beenreplaced by grazed pastures 3–25 years ago, wereinvestigated for two contrasting soil types (AndicHumitropept and Eutric Hapludand) in the Atlantic Zoneof Costa Rica. By forest clearing and subsequentestablishment of pastures, photosynthesis changes froma C-3 to a C-4 pathway. The accompanying changes inC-input and its 13C and 14Csignals, were used to quantify SOC dynamics. C-input from rootturnover at a pasture site was measured by sequentialharvesting and 14C-pulse labelling. With aspatial resolution of 5 cm, data on total SOC,13C and 14C of soil profileswere interpreted with a model that distinguishes threepools of SOC: active C, slow C and passive C,each with a 1-st order decomposition rate(ka, ks and kp). The modelincludes carbon isotope fractionation and depth-dependentdecomposition rates. Transport of C between soillayers was described as a diffusion process, whichaccounts for physical and biotic mixing processes.Calibrated diffusion coefficients were 0.42 cm2yr-1 for the Humitropept and 3.97 cm2yr-1 for the Hapludand chronosequence.Diffusional transport alone was insufficient foroptimal simulation; it had to be augmented bydepth-dependent decomposition rates to explain thedynamics of SOC, 13C and14C. Decomposition rates decreasedstrongly with depth. Upon increased diffusion,differences between calibrated decomposition rates ofSOC fractions between surface soils and subsoilsdiminished, but the concept of depth-dependentdecomposition had to be retained, to obtain smallresiduals between observed and simulated data. At areference depth of 15–20 cm ks was 90 yr-1in the Humitropept and 146 yr-1 in the Hapludand.Slow C contributed most to total organic C in surfacesoils, whereas passive C contributed most below 40 cmdepth. After 18–25 years of pasture, net loss of C was2180 g C m-2 for the Hapludand and 150 g m-2for the Humitropept soil. 相似文献
15.
Milan Höfer Klaas Nicolay George Robillard 《Journal of bioenergetics and biomembranes》1985,17(3):175-182
The electrochemical gradient of protons,
, was estimated in the obligatory aerobic yeastRhodotorula glutinis in the pH0 range from 3 to 8.5. The membrane potential, , was measured by steady-state distribution of the hydrophobic ions, tetraphenylphosphonium (TPP+) for negative above pH0 4.5, and thiocyanate (SCN–) for positive below pH0 4.5. The chemical gradient of H+ was determined by measuring the chemical shift of intracellular Pi by31P-NMR at given pH0 values. The values of pHi increased almost linearly from 7.3 at pH0 3 to 7.8 at pH0 8.5. In the physiological pH0 range from 3.5 to 6,
was fairly constant at values between 17–18 KJ mol–1, gradually decreasing at pH0 above 6. In deenergized cells, the intracellular pHi decreased to values as low as 6, regardless of whether the cell suspension was buffered at pH0 4.5 or 7.5. There was no membrane potential detectable in deenergized cells. 相似文献
16.
Jens Chr. Madsen Ole Winneche Sørensen Poul Sørensen Flemming M. Poulsen 《Journal of biomolecular NMR》1993,3(2):239-244
Summary NMR pulse sequences for measuring coupling constants in 13C, 15N-labeled proteins are presented. These pulse sequences represent improvements over earlier experiments with respect to resolution and number of radiofrequency pulses. The experiments are useful for measuring JNH
, JNCO, JNC
, JH
N
CO and JH
N
H
. Applications to chymotrypsin inhibitor 2 (CI-2) are shown. 相似文献
17.
Summary Particle supported biofilms of uniform thickness were generated in an aerobic fluidized-bed reactor with phenol as the carbon source. A method was developed for determining the effective diffusivities of oxygen and phenol using trypan blue, a vital stain as the tracer. The effective diffusivities of oxygen and phenol were found to be 2.72×10–6 cm2/s and 1.12×10–6 cm2/s respectively.Nomenclature Ci
initial solute concentration in bulk, g/cm3
- Ct
solute concentration in bulk at time t, g/cm3
- C
bulk solute concentration at equilibrium, g/cm3
- D
molecular diffusivity, cm2/s
- D
effective diffusivity, cm2/s
- Do Dp Dtb
molecular diffusivity of oxygen, phenol and trypan blue, cm2/s
- Do, Dp, Dtb
effective diffusivity of oxygen, phenol and trypan blue, cm2/s
- Ds
molecular diffusivity of substrate, cm2/s
- Ds
effective diffusivity of substrate, cm2/s
- K
partition coefficient
- Mt
amount of solute in the particle at time t, g
- M
amount of solute in the particle at equilibrium, g
-
r
particle radius, cm
-
r
bp
radius of the particle with biofilm, cm
- S
substrate concentration, g/cm3
- Sb
substrate concentration in bulk, g/cm3
- Si
initial substrate concentration, g/cm3
- V1
solute molar volume, cm3/g mol
Greek Symbols
bf
porosity of the biofilm
-
tortuosity factor 相似文献
18.
Franklin J. Moy Andrew P. Seddon Ernest B. Campbell Peter Böhlen Robert Powers 《Journal of biomolecular NMR》1995,6(3):245-254
Summary The assignments of the 1H, 15N, 13CO and 13C resonances of recombinant human basic fibroblast growth factor (FGF-2), a protein comprising 154 residues and with a molecular mass of 17.2 kDa, is presented based on a series of three-dimensional triple-resonance heteronuclear NMR experiments. These studies employ uniformly labeled 15N- and 15N-/13C-labeled FGF-2 with an isotope incorporation >95% for the protein expressed in E. coli. The sequence-specific backbone assignments were based primarily on the interresidue correlation of C, C and H to the backbone amide 1H and 15N of the next residue in the CBCA(CO)NH and HBHA(CO)NH experiments and the intraresidue correlation of C, C and H to the backbone amide 1H and 15N in the CBCANH and HNHA experiments. In addition, C and C chemical shift assignments were used to determine amino acid types. Sequential assignments were verified from carbonyl correlations observed in the HNCO and HCACO experiments and C correlations from the carbonyl correlations observed in the HNCO and HCACO experiments and C correlations from the HNCA experiment. Aliphatic side-chain spin systems were assigned primarily from H(CCO)NH and C(CO)NH experiments that correlate all the aliphatic 1H and 13C resonances of a given residue with the amide resonance of the next residue. Additional side-chain assignments were made from HCCH-COSY and HCCH-TOCSY experiments. The secondary structure of FGF-2 is based on NOE data involving the NH, H and H protons as well as 3JH
n
H coupling constants, amide exchange and 13C and 13C secondary chemical shifts. It is shown that FGF-2 consists of 11 well-defined antiparallel -sheets (residues 30–34, 39–44, 48–53, 62–67, 71–76, 81–85, 91–94, 103–108, 113–118, 123–125 and 148–152) and a helix-like structure (residues 131–136), which are connected primarily by tight turns. This structure differs from the refined X-ray crystal structures of FGF-2, where residues 131–136 were defined as -strand XI. The discovery of the helix-like region in the primary heparin-binding site (residues 128–138) instead of the -strand conformation described in the X-ray structures may have important implications in understanding the nature of heparin-FGF-2 interactions. In addition, two distinct conformations exist in solution for the N-terminal residues 9–28. This is consistent with the X-ray structures of FGF-2, where the first 17–19 residues were ill defined. 相似文献
19.
M. Dutta V. Arunachalam A. Bandyopadhyay K. Vinod Prabhu 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1986,71(4):662-666
Summary Seeds of 4 crosses of groundnut (Arachis hypogaea L.), Robut 33-1 x Chico, Robut 33-1 x NC Ac 17090, Robut 33-1 x PI 298115 and MK 374 x GAUG 1, were irradiated with 30 kR. In the F1, some branches of each plant were intermated with other plants at random and others selfed in each cross to produce S2 and F2 seeds. They were evaluated for pod yield, shelling percentage and 100-kernel weight. The frequency of plants superior to F[in1] was much higher in S2 than in F2, which was, in general, true for the values of yield and its components. The S2 and F2 were advanced to third generation by selfing. The families descending from S2 showed clear superiority over those from F2. The reason for such superiority was suggested to be the recombination of genes from the upper and lower ends of the genotypic distribution under intermating. 相似文献
20.
Clones of three cultivars of Medicago sativa (Rambler, Regen S and Rangelander) were used as sources of mesophyll protoplasts. Although all three clones readily produced protoplasts, the subsequent development patterns in culture varied greatly among genotypes, with protoplasts from Regen S and Rambler forming calli which could be induced to form embryos, and protoplasts from Rangelander undergoing direct embryogenesis. Protoplasts of Regen S exhibited high rates of division while those of Rangelander tended to aggregate with only a few cells per aggregate surviving. The surviving cells gave rise to proembryos within the aggregates; these proembryos developed into differentiated embryos after 5–7 weeks of culture. Based on the initial protoplast population, the efficiency of embryo formation averaged 0.13% and ranged from 0.001–0.4%. Observations during the early stages of culture indicated that cell aggregation was a prerequisite for direct embryogenesis. 相似文献